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Materials, Volume 3, Issue 2 (February 2010) – 35 articles , Pages 755-1496

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512 KiB  
Review
Electrically and Thermally Conducting Nanocomposites for Electronic Applications
by Wayne E. Jones, Jr., Jasper Chiguma, Edwin Johnson, Ashok Pachamuthu and Daryl Santos
Materials 2010, 3(2), 1478-1496; https://doi.org/10.3390/ma3021478 - 25 Feb 2010
Cited by 59 | Viewed by 17443
Abstract
Nanocomposites made up of polymer matrices and carbon nanotubes are a class of advanced materials with great application potential in electronics packaging. Nanocomposites with carbon nanotubes as fillers have been designed with the aim of exploiting the high thermal, electrical and mechanical properties [...] Read more.
Nanocomposites made up of polymer matrices and carbon nanotubes are a class of advanced materials with great application potential in electronics packaging. Nanocomposites with carbon nanotubes as fillers have been designed with the aim of exploiting the high thermal, electrical and mechanical properties characteristic of carbon nanotubes. Heat dissipation in electronic devices requires interface materials with high thermal conductivity. Here, current developments and challenges in the application of nanotubes as fillers in polymer matrices are explored. The blending together of nanotubes and polymers result in what are known as nanocomposites. Among the most pressing current issues related to nanocomposite fabrication are (i) dispersion of carbon nanotubes in the polymer host, (ii) carbon nanotube-polymer interaction and the nature of the interface, and (iii) alignment of carbon nanotubes in a polymer matrix. These issues are believed to be directly related to the electrical and thermal performance of nanocomposites. The recent progress in the fabrication of nanocomposites with carbon nanotubes as fillers and their potential application in electronics packaging as thermal interface materials is also reported. Full article
(This article belongs to the Special Issue Composite Materials)
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<p>Hollow carbon fibers. Adapted from reference [<a href="#B7-materials-03-01478" class="html-bibr">7</a>] with permission. Grobert, N. Carbon nanotubes – becoming clean. <span class="html-italic">Mater. Today</span> <b>2007</b>, <span class="html-italic">10</span> (1–2), 28–35.</p> Full article ">Figure 2
<p>Carbon nanotube-like structures. Adapted from reference [<a href="#B8-materials-03-01478" class="html-bibr">8</a>] with permission from Carbon. Kuznetsov, V.L. Who should be given credit for the discovery of carbon nanotubes? <span class="html-italic">Carbon</span> <b>2006</b>, <span class="html-italic">44</span>, 1621–1624.</p> Full article ">Figure 3
<p>Structure of graphite layers.</p> Full article ">Figure 4
<p>TEM of MWCNTs discovered by Iijima in 1991. Adapted from reference [<a href="#B4-materials-03-01478" class="html-bibr">4</a>], with permission from Nature. Iijima, S. Helical microtubules of graphitic carbon. <span class="html-italic">Nature</span> <b>1991</b>, <span class="html-italic">354</span>, 56–58.</p> Full article ">Figure 5
<p>TEM of SWCNTs discovered by Iijima in 1993. Adapted from reference [<a href="#B15-materials-03-01478" class="html-bibr">15</a>], with permission from Nature. Bethume, D.S.; Klang, C.H.; de Vries, M.S.; Gorman, G.; Savoy, R.; Vazquez, J.; Beyers, R. Cobalt-catalysed growth of carbon nanotubes with single-atomic-layer walls. <span class="html-italic">Nature</span>, <b>1993</b>, <span class="html-italic">363</span>, 605–607.</p> Full article ">Figure 6
<p>TEM of DWCNTs. Adapted from reference [<a href="#B16-materials-03-01478" class="html-bibr">16</a>], with permission from Elsevier<span class="html-italic">.</span> Dai, H, Rinzler, A.; Nikolaev, P.; Thess, A.; Colbert, D.; Smalley R. Single-wall nanotubes by metal-catalyzed disproportionation of carbon monoxide. <span class="html-italic">Chem. Phys. Lett.</span> <b>1996</b>, <span class="html-italic">260</span>, 471.</p> Full article ">Figure 7
<p>Macromolecular structure of polymers (a) Linear (b) Branched (c) Network.</p> Full article ">Figure 8
<p>Formation of polyaniline from aniline and its two forms.</p> Full article ">Figure 9
<p>Mechanism illustrating the formation of polypyrrole (a) Overall process (b) Proposed mechanism: 1. monomer oxidation; 2. dimerization; 3. proton loss; 4.repetition.</p> Full article ">Figure 10
<p>Formation of PEDOT.</p> Full article ">Figure 11
<p>Formation of Polythiophene.</p> Full article ">Figure 12
<p>Functionalization methods. Adapted from reference 36, with permission from the publisher. Wagner, H.D.; Vaia, R.A. Nanocomposites: issues at the interface. <span class="html-italic">Mater. Today</span> <b>2004</b>, <span class="html-italic">7</span> (11), 38–42.</p> Full article ">Figure 13
<p>Effect of doping on the band gap and energy in conducting polymers. (a) an undoped and (b) an oxidatively doped (bipolaron) conducting polymer.</p> Full article ">
3224 KiB  
Article
Polymer Nanocomposites Containing Anisotropic Metal Nanostructures as Internal Strain Indicators
by Marco Bernabò, Andrea Pucci, Hasina Harimino Ramanitra and Giacomo Ruggeri
Materials 2010, 3(2), 1461-1477; https://doi.org/10.3390/ma3021461 - 24 Feb 2010
Cited by 22 | Viewed by 16447
Abstract
Polymer/metal nanocomposite containing intrinsically anisotropic metal nanostructures such as metal nanorods and nanowires appeared extremely more sensitive and responsive to mechanical stimuli than nanocomposites containing spherical nanoparticles. After uniaxial stretching of the supporting polymer matrix (poly(vinyl alcohol)), the elongated silver nanostructures embedded at [...] Read more.
Polymer/metal nanocomposite containing intrinsically anisotropic metal nanostructures such as metal nanorods and nanowires appeared extremely more sensitive and responsive to mechanical stimuli than nanocomposites containing spherical nanoparticles. After uniaxial stretching of the supporting polymer matrix (poly(vinyl alcohol)), the elongated silver nanostructures embedded at low concentration into the polymer matrix (<1 wt % of Ag) assume the direction of the drawing, yielding materials with a strong dichroic response of the absorption behavior. Accordingly, the film changed its color when observed under linearly polarized light already at moderate drawings. The results obtained suggest that nanocomposite films have potential in applications such as color polarizing filters, radiation responsive polymeric objects and smart flexible films in packaging applications. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schema of silver nanorod stabilization by CTAB capping.</p> Full article ">Figure 2
<p>(a) UV-Vis absorption spectra of silver seed (grey) and nanorods (black) water dispersions. (b) Plot of the nanorods absorbance at 420 nm as a function of the reaction time with reference to the absorbance recorded at t = 0.</p> Full article ">Figure 3
<p>TEM micrograph of silver nanorods suspension after three min of reaction. Spherical and polygonal architectures like prisms and other geometrical features were present in the mixture as well (picture inset on the bottom left).</p> Full article ">Figure 4
<p>(a) SEM micrograph of a PVA@AgNR oriented film (Dr = 5) The white arrow denotes the stretching direction. In the inset: TEM image of an AgNR embedded in the polymer matrix. (b) Energy dispersive (EDS) spectrum of the film polymer surface. The white rectangle in (a) highlights the area where the EDS analysis was performed.</p> Full article ">Figure 5
<p>UV-Vis spectra of a PVA@AgNR oriented film (Dr = 5) as a function of the angle between the polarization light and the drawing direction.</p> Full article ">Figure 6
<p>Images of oriented PVA@AgNR film (Dr = 5) observed through a linear polarizer with the transmission axis parallel (0°) and perpendicular (90°) to the drawing direction.</p> Full article ">Figure 7
<p>TEM micrograph of an oriented PVA@AgNR film (Dr = 5; the inset shows the presence of dispersed silver structures with dimensions between 50 and 100 nm).</p> Full article ">Figure 8
<p>UV-Vis absorption spectra of the reaction mixture at various reaction times (min).</p> Full article ">Figure 9
<p>FT-IR spectra of neat PVP and silver nanowires.</p> Full article ">Figure 10
<p>XRD pattern of PVA@AgNW film.</p> Full article ">Figure 11
<p>SEM micrograph of a PVA@AgNW film and plot profile of a silver nanowire (line scan within the white arrows).</p> Full article ">Figure 12
<p>UV-Vis absorption spectra of an oriented PVA@AgNW film as a function of the angle between the polarization of light and the drawing direction of the film, and images of the same film observed through a linear polarizer with the transmission axis parallel (0°) and perpendicular (90°) to the drawing direction (inset).</p> Full article ">
797 KiB  
Review
Self-Assembled Hydrogel Nanoparticles for Drug Delivery Applications
by Catarina Gonçalves, Paula Pereira and Miguel Gama
Materials 2010, 3(2), 1420-1460; https://doi.org/10.3390/ma3021420 - 24 Feb 2010
Cited by 170 | Viewed by 25763
Abstract
Hydrogel nanoparticles—also referred to as polymeric nanogels or macromolecular micelles—are emerging as promising drug carriers for therapeutic applications. These nanostructures hold versatility and properties suitable for the delivery of bioactive molecules, namely of biopharmaceuticals. This article reviews the latest developments in the use [...] Read more.
Hydrogel nanoparticles—also referred to as polymeric nanogels or macromolecular micelles—are emerging as promising drug carriers for therapeutic applications. These nanostructures hold versatility and properties suitable for the delivery of bioactive molecules, namely of biopharmaceuticals. This article reviews the latest developments in the use of self-assembled polymeric nanogels for drug delivery applications, including small molecular weight drugs, proteins, peptides, oligosaccharides, vaccines and nucleic acids. The materials and techniques used in the development of self-assembling nanogels are also described. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Size of dextrin nanoparticles evaluated by (a) atomic force microscopy and (b) cryo-scanning electron microscopy, adapted from [<a href="#B19-materials-03-01420" class="html-bibr">19</a>].</p> Full article ">Figure 2
<p>Fluorescence images obtained by confocal microscopy of murine bone marrow-derived macrophages (a) incubated without nanoparticles and (b) with FITC-containing nanoparticles (green). Nucleus stained with DAPI (blue), adapted from [<a href="#B19-materials-03-01420" class="html-bibr">19</a>].</p> Full article ">Figure 3
<p>Schematic representation of intermolecular interactions driving self-assembly processes that includes (a) electrostatic interactions and (b) hydrophobic association.</p> Full article ">Figure 4
<p>Targeting strategies for cancer therapy. Passive targeting can be achieved by enhanced permeation and retention, an effect involving leaky vascular structures. Active targeting mediated by targeting ligands specifically localizes drug carriers at desired cells or tissues. The decoration of the nanoparticles with ligands improves its internalization by endocytosis.</p> Full article ">
2762 KiB  
Review
Microstructural Characterisation and Wear Behaviour of Diamond Composite Materials
by James N. Boland and Xing S. Li
Materials 2010, 3(2), 1390-1419; https://doi.org/10.3390/ma3021390 - 24 Feb 2010
Cited by 93 | Viewed by 18080
Abstract
Since the initial research leading to the production of diamond composite materials, there have been several important developments leading to significant improvements in the properties of these superhard composite materials. Apart from the fact that diamonds, whether originating from natural resources or synthesised [...] Read more.
Since the initial research leading to the production of diamond composite materials, there have been several important developments leading to significant improvements in the properties of these superhard composite materials. Apart from the fact that diamonds, whether originating from natural resources or synthesised commercially, are the hardest and most wear-resistant materials commonly available, there are other mechanical properties that limit their industrial application. These include the low fracture toughness and low impact strength of diamond. By incorporating a range of binder phases into the sintering production process of these composites, these critically important properties have been radically improved. These new composites can withstand much higher operating temperatures without markedly reducing their strength and wear resistance. Further innovative steps are now being made to improve the properties of diamond composites by reducing grain and particle sizes into the nano range. This review will cover recent developments in diamond composite materials with special emphasis on microstructural characterisation. The results of such studies should assist in the design of new, innovative diamond tools as well as leading to radical improvements in the productivity of cutting, drilling and sawing operations in the exploration, mining, civil construction and manufacturing industries. Full article
(This article belongs to the Special Issue Composite Materials)
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<p>P-T phase diagram for carbon relevant to diamond composite manufacture. Note: 10kb = 1 GPa (Copy from US Patent: 4,948,388, 1989).</p> Full article ">Figure 2
<p>SEM images of TSDC cutting elements; (left) SEI of fracture surface with no evident pluck-out of diamond grains; (right) BEI of a polished surface with surface relief masking detailed phase information in the image.</p> Full article ">Figure 3
<p>(a) SEM-BEI image of a TSDC sample showing the dominant diamond phase (A) and the complex, multi-phase matrix material. (b). EDS spectra from points A (left) and B (right). The single carbon peak at A clearly indicates the diamond phase; the multi-elemental spectrum analysed at point B clearly highlights the complexity of the matrix material in this commercially produced TSDC sample.</p> Full article ">Figure 4
<p>SEM-BEI image (left) from a TSDC sample with the corresponding EDS spot analysis of the light-grey phase indicating residual, unalloyed Si metal in the matrix.</p> Full article ">Figure 5
<p>SEM-BEI image (left) from TSDC sample with the EDS spectrum (right) from the designed spot.</p> Full article ">Figure 6
<p>(a). SEM-BEI image of a TSDC sample. The dark grains are diamond and the various shades of lighter contrast in the matrix regions indicate the presence of several phases. (b). Hyperspectral image of the same field-of-view as in (a) in which the specific elements have been colour-rendered according to the attached colour table—see text for details. (c). Cathodoluminescence from TSDC samples listed in <a href="#materials-03-01390-t001" class="html-table">Table 1</a> showing room temperature CL spectra and the three prominent bands A, B and C. Note: M10-a and M3-f as shown in <a href="#materials-03-01390-t001" class="html-table">Table 1</a> are equivalent samples with respect to their wear resistance. (d). Mapping of the cathodoluminescent signals from a TSDC sample with the colour code showing the spectral range in nm—see text for details.</p> Full article ">Figure 6 Cont.
<p>(a). SEM-BEI image of a TSDC sample. The dark grains are diamond and the various shades of lighter contrast in the matrix regions indicate the presence of several phases. (b). Hyperspectral image of the same field-of-view as in (a) in which the specific elements have been colour-rendered according to the attached colour table—see text for details. (c). Cathodoluminescence from TSDC samples listed in <a href="#materials-03-01390-t001" class="html-table">Table 1</a> showing room temperature CL spectra and the three prominent bands A, B and C. Note: M10-a and M3-f as shown in <a href="#materials-03-01390-t001" class="html-table">Table 1</a> are equivalent samples with respect to their wear resistance. (d). Mapping of the cathodoluminescent signals from a TSDC sample with the colour code showing the spectral range in nm—see text for details.</p> Full article ">Figure 7
<p>Raman spectrum from a good quality (low wear rate or high wear resistance) TSDC sample with no evidence of graphitic material.</p> Full article ">Figure 8
<p>Optical micrograph (top) of poor quality (low wear rate or high wear resistance) TSDC material showing large (~25 μm), diamond grains with smaller (~10 μm) golden coloured grains with the distinctive graphitic Raman spectrum (bottom).</p> Full article ">Figure 9
<p>SEM-SEI image of the wear surface of a TSDC cutting element subjected to the standard pin-on-disk abrasive wear test.</p> Full article ">Figure 10
<p>Photos of the CSIRO’s abrasive wear testing rig for diamond composite cutting elements with an alumina grinding wheel as the counter piece for the test. Note: the high temperature region in the vicinity of the cutting tip (left) and tool holder (right).</p> Full article ">Figure 11
<p>Cemented tungsten carbide cutting element (WC) before (left) and after only 20 cuts on the abrasive wear testing rig (right).</p> Full article ">Figure 12
<p>SEM-SEI image of a poor quality TSDC cutting element (see M2-b, <a href="#materials-03-01390-t001" class="html-table">Table 1</a>). The diamond grains are clearly delineated with cleavage fracture features while the matrix is unreacted silicon metal with the porous microstructure. The bonding of the diamond to the unreacted Si appears to be weak as there is evidenced by the diamond grains having been plucked out during the wear test.</p> Full article ">Figure 13
<p>Optical images of both samples as mounted in the sample holder of GADDS<sup>TM</sup>. Upper image is of the high quality TSDC (<span class="html-italic">i.e.,</span> high wear resistance, sample 1) with a small wear flat (upper) and the lower image of poor quality TSDC (<span class="html-italic">i.e.,</span> low wear resistance, sample 5) showing the large wear flat. The bright laser spot on each of the wear surfaces indicates the location of the x-ray beam used in the analyses (Magnifications: upper image ×40, lower image ×30).</p> Full article ">Figure 14
<p>X-ray diffraction spectrum of sample 1 (good quality TSDC with high resistance). The automated peak search revealed diamond, silicon metal, the 6H and 3C polytypes of SiC with two unknown peaks, P1 and P2.</p> Full article ">Figure 15
<p>X-ray diffraction spectrum of sample 5 (poor quality TSDC) with diamond and Si metal positively identified. There are several smaller peaks between 33° and 43° that can tentatively assigned to the SiC polytypes—refer to XRD trace above - but appear to be in much smaller quantitatives than in sample 1.</p> Full article ">Figure 16
<p>EDS spectra observed in the GADDS<sup>TM</sup> analyses from Sample 1 (upper spectrum) and sample 5 (lower spectrum).</p> Full article ">Figure 17
<p>Top views of diamond coated cutting elements sintered onto a WC substrate: upper image showing the wear flat generated on a high quality sample after 100 cuts (approximate cutting distance of 3399 m and wear rate of 6 g/m<sup>3</sup>); lower image showing the excessive wear produced on a poor quality sample in which the diamond coating abraded through to expose the WC substrate after 4 cuts (~152 m) (scale markers: 10 mm).</p> Full article ">Figure 18
<p>SEM-BEI image of the top worn surface of poor quality PCD-coated WC cutting element shown in <a href="#materials-03-01390-f017" class="html-fig">Figure 17</a> (lower image).</p> Full article ">Figure 19
<p>SEM-BEI image of top worn surface of good quality PCD-coated WC cutting element shown in <a href="#materials-03-01390-f017" class="html-fig">Figure 17</a> (upper image).</p> Full article ">Figure 20
<p>X-ray projection image of a PCD coating on WC substrate (blue region). Note the extent of intrusion of the WC substrate into the coating as well as the small cracks confined with the coating itself (scale: coating thickness ~454 μm.)</p> Full article ">Figure 21
<p>Microscopic model of the chip forming processes based on the interaction between an individual diamond grain and the work piece. This model is specific to brittle materials such a stone (Reproduced with permission of Trans Tech Publications – [<a href="#B52-materials-03-01390" class="html-bibr">52</a>])</p> Full article ">Figure 22
<p>Phenomenological model for macro and micro chip formation in brittle materials such as rock.</p> Full article ">
638 KiB  
Article
Scaffold Sheet Design Strategy for Soft Tissue Engineering
by Richard T. Tran, Paul Thevenot, Yi Zhang, Dipendra Gyawali, Liping Tang and Jian Yang
Materials 2010, 3(2), 1375-1389; https://doi.org/10.3390/ma3021375 - 24 Feb 2010
Cited by 45 | Viewed by 16866
Abstract
Creating heterogeneous tissue constructs with an even cell distribution and robust mechanical strength remain important challenges to the success of in vivo tissue engineering. To address these issues, we are developing a scaffold sheet tissue engineering strategy consisting of thin (~200 μm), strong, [...] Read more.
Creating heterogeneous tissue constructs with an even cell distribution and robust mechanical strength remain important challenges to the success of in vivo tissue engineering. To address these issues, we are developing a scaffold sheet tissue engineering strategy consisting of thin (~200 μm), strong, elastic, and porous crosslinked urethane- doped polyester (CUPE) scaffold sheets that are bonded together chemically or through cell culture. Suture retention of the tissue constructs (four sheets) fabricated by the scaffold sheet tissue engineering strategy is close to the surgical requirement (1.8 N) rendering their potential for immediate implantation without a need for long cell culture times. Cell culture results using 3T3 fibroblasts show that the scaffold sheets are bonded into a tissue construct via the extracellular matrix produced by the cells after 2 weeks of in vitro cell culture. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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Figure 1
<p>Representative SEM image cross-sections (a) single CUPE 1.2 scaffold sheet (scale bar = 150 μm), (b) two CUPE 1.2 scaffold sheets crosslinked together (scale bar = 300 μm), and <b>(c)</b> 4 CUPE 1.2 scaffold sheets crosslinked together (scale bar = 600 μm).</p> Full article ">Figure 2
<p>A comparison between single POC and CUPE 1.2 scaffold sheets. All scaffolds were post-polymerized at 80 °C for 4 days followed by 120 °C for 1 day under vacuum. (a) Effect of scaffold material on the peak stress. (b) Effect of scaffold material on elongation at break. ** p &lt; 0.01; N = 6.</p> Full article ">Figure 3
<p>(a) Photograph of a single CUPE 1.2 scaffold sheet (left) and CUPE 1.2 scaffold sheet rolled onto a Teflon rod (right). Typical tensile stress-strain curves of (b) single CUPE 1.2 scaffold sheets post-polymerized under different reaction conditions and (c) multiple CUPE 1.2 scaffold sheets post-polymerized at 80 °C for 4 days followed by 120 °C for 1 day under vacuum.</p> Full article ">Figure 4
<p>(a) Tensile peak stress, (b) initial modulus, (c) elongation at break, and (d) suture retention strength of multiple scaffold sheets fabricated using different CUPE HDI ratios. All scaffolds were post-polymerized at 80 °C for 4 days followed by 120 °C for 1 day under vacuum.</p> Full article ">Figure 5
<p>A comparison of 3T3 fibroblast growth and proliferation on single PLLA, POC, and CUPE 1.2 scaffold sheets over a 5-day incubation time period. MTT absorption was measured at 570 nm. N = 6.</p> Full article ">Figure 6
<p>Photomicrographs of H&amp;E stained CUPE 1.2 cross-sections after 2 weeks of cell culture. (A) Single scaffold sheet. (B) 2 scaffold sheets were shown to have bonded together using 3T3 fibroblasts (scale bar = 100 μm).</p> Full article ">Figure 7
<p>A schematic representation of the scaffold sheet fabrication process and scaffold sheet tissue engineering design. (a) Pre-crosslinked urethane-doped polyester (pre-CUPE) is mixed with sieved salt (50–106 μm). (b) The resulting polymer/salt slurry is cast into an aluminum mold (~200 μm deep). (c) The polymer filled aluminum mold is placed in an oven for predetermined times for post-polymerization to crosslink the polymer. (d) After post-polymerization, the salt is leached from the scaffold by immersion in water. (e) Next, the scaffold is lyophilized to remove any trace amounts of water. The result is a thin (~200 μm thick), soft, and elastic CUPE scaffold sheet. (f) The sterilized CUPE scaffold sheets are seeded with cells. (g) Multiple cell-seeded CUPE scaffold sheets are stacked together and allowed to culture. (h) The bonded scaffold sheets produce a three-dimensional multi-layered construct through a layer-by-layer technique.</p> Full article ">
12376 KiB  
Review
Materials for Powder-Based AC-Electroluminescence
by Michael Bredol and Hubert Schulze Dieckhoff
Materials 2010, 3(2), 1353-1374; https://doi.org/10.3390/ma3021353 - 23 Feb 2010
Cited by 95 | Viewed by 19580
Abstract
At present, thick film (powder based) alternating current electroluminescence (AC-EL) is the only technology available for the fabrication of large area, laterally structured and coloured light sources by simple printing techniques. Substrates for printing may be based on flexible polymers or glass, so [...] Read more.
At present, thick film (powder based) alternating current electroluminescence (AC-EL) is the only technology available for the fabrication of large area, laterally structured and coloured light sources by simple printing techniques. Substrates for printing may be based on flexible polymers or glass, so the final devices can take up a huge variety of shapes. After an introduction of the underlying physics and chemistry, the review highlights the technical progress behind this development, concentrating on luminescent and dielectric materials used. Limitations of the available materials as well as room for further improvement are also discussed. Full article
(This article belongs to the Special Issue Luminescent Materials)
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Figure 1

Figure 1
<p>Internal structure (schematic) of an AC-EL foil lamp.</p> Full article ">Figure 2
<p>Electron micrograph of a cross section through a printed thick-film AC-EL stack.</p> Full article ">Figure 3
<p>Time slots in an AC-El cell under typical excitation conditions.</p> Full article ">Figure 4
<p>Electric field strength over luminescent particles.</p> Full article ">Figure 5
<p>Emission spectra of conventional AC-El cell at various driving voltages, frequency: 300 Hz.</p> Full article ">Figure 6
<p>Impedance spectrum of a conventional AC-El cell at low voltage, together with fitted function.</p> Full article ">Figure 7
<p>Dielectric function plotted from data in <a href="#materials-03-01353-f006" class="html-fig">Figure 6</a>, fitted to <span class="html-italic">Havriliak– Negami</span>’s equation.</p> Full article ">Figure 8
<p>Schmatic of the electrical conditions in a ligand-stabilized nanoparticle.</p> Full article ">Figure 9
<p>Spectral shift and reduction of emission intensity of AC-EL (ZnS:Cu) phosphor after heat treatment in humid air.</p> Full article ">Figure 10
<p>Fluorescence image of a cured (500 <math display="inline"> <msup> <mrow/> <mo>∘</mo> </msup> </math>C) enamel/phosphor composite, taken through the substrate glass under UV illumination (366nm). Image width: 2 mm.</p> Full article ">Figure 11
<p>AC-luminescence after heat treatment at 500 <math display="inline"> <msup> <mrow/> <mo>∘</mo> </msup> </math>C; light taken up by a fibre spectrometer.</p> Full article ">Figure 12
<p>AC-luminescence after heat treatment, viewed through the substrate. Left: after 200 <math display="inline"> <msup> <mrow/> <mo>∘</mo> </msup> </math>C. Center: after 500 <math display="inline"> <msup> <mrow/> <mo>∘</mo> </msup> </math>C. Right: after 600 <math display="inline"> <msup> <mrow/> <mo>∘</mo> </msup> </math>C. Scale bar: 200 <span class="html-italic">μ</span>m.</p> Full article ">
923 KiB  
Review
Colloidal Inorganic Nanocrystal Based Nanocomposites: Functional Materials for Micro and Nanofabrication
by Chiara Ingrosso, AnnaMaria Panniello, Roberto Comparelli, Maria Lucia Curri and Marinella Striccoli
Materials 2010, 3(2), 1316-1352; https://doi.org/10.3390/ma3021316 - 23 Feb 2010
Cited by 56 | Viewed by 17981
Abstract
The unique size- and shape-dependent electronic properties of nanocrystals (NCs) make them extremely attractive as novel structural building blocks for constructing a new generation of innovative materials and solid-state devices. Recent advances in material chemistry has allowed the synthesis of colloidal NCs with [...] Read more.
The unique size- and shape-dependent electronic properties of nanocrystals (NCs) make them extremely attractive as novel structural building blocks for constructing a new generation of innovative materials and solid-state devices. Recent advances in material chemistry has allowed the synthesis of colloidal NCs with a wide range of compositions, with a precise control on size, shape and uniformity as well as specific surface chemistry. By incorporating such nanostructures in polymers, mesoscopic materials can be achieved and their properties engineered by choosing NCs differing in size and/or composition, properly tuning the interaction between NCs and surrounding environment. In this contribution, different approaches will be presented as effective opportunities for conveying colloidal NC properties to nanocomposite materials for micro and nanofabrication. Patterning of such nanocomposites either by conventional lithographic techniques and emerging patterning tools, such as ink jet printing and nanoimprint lithography, will be illustrated, pointing out their technological impact on developing new optoelectronic and sensing devices. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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Graphical abstract
Full article ">Figure 1
<p>TEM images of colloidal NCs with different composition which can be incorporated in a host polymer matrix.</p> Full article ">Figure 2
<p>Luminescence spectra of CdSe@ZnS NCs of different size in CHCl<sub>3</sub> solution. (top panel) Absorbance spectra of aqueous solution of Au nanorods with different aspect ratio(bottom panel).</p> Full article ">Figure 3
<p>Schematic representation of engineered NCs incorporated in polymer matrices. (a) Playing with capping ligand alkyl chain length and steric hindrance; (b) exploiting capping ligand bearing a reactive moiety (c) bi-functional ligand modified NCs (d) NCs modified with polymer ligands. In the picture: fluorescence view of a flat imprinted structure on CdSe@ZnS NC/ PMMA nanocomposite.</p> Full article ">Figure 4
<p>Strategies for homogeneous dispersion of NCs in polymer matrix: part a represent the polymers and part b the prepared nanocomposites. 1 Use of a common solvent; 2 Presence of initiator groups on NC surface to induce the binding to polymer matrix; 3 Functional chemical groups on the polymer chains, able to coordinate NC surface.</p> Full article ">Figure 5
<p>Tilted SEM images of the photostructured CdSe@ZnS NC modified resists, after UV photolithographic processing(Top panel). Fluorescence microscopy images and emission spectra (bottom panel) of the microstructures obtained from the CdSe@ZnS NC modified (a) and unmodified (b) epoxy resist [<a href="#B106-materials-03-01316" class="html-bibr">106</a>].</p> Full article ">Figure 6
<p>UV–Vis absorption and PL spectra of CdS and CdSe@ZnS NCs of different diameters in CHCl<sub>3</sub>, (top panel); fluorescence microscope images of single- and multi- colour microarrays of NC functionalized PS ink-jet printed by a single and a multi nozzle system, respectively (bottom panel) [<a href="#B175-materials-03-01316" class="html-bibr">175</a>].</p> Full article ">
818 KiB  
Article
Layer-by-Layer Method for the Synthesis and Growth of Surface Mounted Metal-Organic Frameworks (SURMOFs)
by Osama Shekhah
Materials 2010, 3(2), 1302-1315; https://doi.org/10.3390/ma3021302 - 23 Feb 2010
Cited by 123 | Viewed by 24000
Abstract
A layer-by-layer method has been developed for the synthesis of metal-organic frameworks (MOFs) and their deposition on functionalized organic surfaces. The approach is based on the sequential immersion of functionalized organic surfaces into solutions of the building blocks of the MOF, i.e., the [...] Read more.
A layer-by-layer method has been developed for the synthesis of metal-organic frameworks (MOFs) and their deposition on functionalized organic surfaces. The approach is based on the sequential immersion of functionalized organic surfaces into solutions of the building blocks of the MOF, i.e., the organic ligand and the inorganic unit. The synthesis and growth of different types of MOFs on substrates with different functionalization, like COOH, OH and pyridine terminated surfaces, were studied and characterized with different surface characterization techniques. A controlled and highly oriented growth of very homogenous films was obtained using this method. The layer-by-layer method offered also the possibility to study the kinetics of film formation in more detail using surface plasmon resonance and quartz crystal microbalance. In addition, this method demonstrates the potential to synthesize new classes of MOFs not accessible by conventional methods. Finally, the controlled growth of MOF thin films is important for many applications like chemical sensors, membranes and related electrodes. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)
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<p>SPR signal as a function of time recorded <span class="html-italic">in situ</span> during sequential injections of Cu(Ac)<sub>2</sub>, ethanol, and H<sub>3</sub>btc in the SPR cell containing MHDA SAM (left) and MUD SAM (right) [<a href="#B13-materials-03-01302" class="html-bibr">13</a>,<a href="#B17-materials-03-01302" class="html-bibr">17</a>].</p> Full article ">Figure 2
<p>QCM-D signal as a function of time recorded <span class="html-italic">in situ</span> during sequential injections of Cu(Ac)<sub>2</sub>, ethanol and H<sub>3</sub>btc on the QCM substrate covered by a MHDA SAM (left), and a MUD SAM (right).</p> Full article ">Figure 3
<p>Out-of-plane XRD data for a Cu<sub>3</sub>(btc)<sub>2</sub>.xH<sub>2</sub>O MOF (a) Bulk, (b) growth on a MHDA SAM (simulation), (c) experimental growth on MHDA SAM (experimental), (d) growth on MUD SAM (simulation), (e) grown on MUD SAM (experimental) [<a href="#B21-materials-03-01302" class="html-bibr">21</a>].</p> Full article ">Figure 4
<p>AFM image of Cu<sub>3</sub>(btc)<sub>2</sub>.xH<sub>2</sub>O MOF (45 cycles) grown on a SAM laterally patterned by microcontact printing (µCP) consisting of COOH-terminated squares and CH<sub>3</sub>-terminated stripes (left), corresponding height averaged profile (calculated over the whole area (right) [<a href="#B37-materials-03-01302" class="html-bibr">37</a>].</p> Full article ">Figure 5
<p>Schematic representation for the synthesis and formation of the 2D and 3D LBMOFs.</p> Full article ">Figure 6
<p>IRRAS spectra of different cycles of Zn<sub>x</sub>(bdc)<sub>y</sub> MOF grown on a MHDA SAM.</p> Full article ">Figure 7
<p>Out-of-plane XRD data for 40 cycles of Zn<sub>x</sub>(bdc)<sub>y</sub> MOF grown on a MHDA SAM.</p> Full article ">Figure 8
<p>SPR signal as a function of time recorded <span class="html-italic">in situ</span> during sequential injections of Zn(Ac)<sub>2</sub>, ethanol , and mixture of H<sub>2</sub>bdc+dabco in the SPR cell containing BPMT SAM.</p> Full article ">Figure 9
<p>Out-of-plane XRD data for a [Zn<sub>2</sub>(bdc)<sub>2</sub>(dabco)] MOF sample (40 cycles) grown on a pyridine terminated SAM (red). The XRD for the bulk (black) is shown for comparison.</p> Full article ">Figure 10
<p>Out-of-plane XRD data for a [Cu<sub>2</sub>(ndc)<sub>2</sub>(dabco)] MOF sample (left) and [Cu<sub>2</sub>(bdc)<sub>2</sub>(dabco)] (right) grown on a pyridine terminated SAM. The XRD of for the bulk is shown for comparison.</p> Full article ">Figure 11
<p>Out-of-plane XRD pattern (blue) for a [Zn(bdc)(4,4′-Bipy)<sub>0.5</sub>] SURMOF-1 sample (40 cycles) grown on a pyridine terminated SAM from PBMT. The XRD patterns for the two possible bulk phases are shown for comparison [<a href="#B34-materials-03-01302" class="html-bibr">34</a>].</p> Full article ">Figure 12
<p>Schematic diagram for the step-by-step approach for the growth of the MOFs on substrates functionalized with SAMs. The approach is done by repeated immersion cycles first in solutions of the metal precursor and subsequently in the solution of organic ligand, after rinsing with the solvent in between.</p> Full article ">
824 KiB  
Article
Synthesis, Structure and Thermal Behavior of Oxalato-Bridged Rb+ and H3O+ Extended Frameworks with Different Dimensionalities
by Hamza Kherfi, Malika Hamadène, Achoura Guehria-Laïdoudi, Slimane Dahaoui and Claude Lecomte
Materials 2010, 3(2), 1281-1301; https://doi.org/10.3390/ma3021281 - 23 Feb 2010
Cited by 12 | Viewed by 14388
Abstract
Correlative studies of three oxalato-bridged polymers, obtained under hydrothermal conditions for the two isostructural compounds {Rb(HC2O4)(H2C2O4)(H2O)2}∞1, 1, {H3O(HC2O4)(H2 [...] Read more.
Correlative studies of three oxalato-bridged polymers, obtained under hydrothermal conditions for the two isostructural compounds {Rb(HC2O4)(H2C2O4)(H2O)2}∞1, 1, {H3O(HC2O4)(H2C2O4).2H2O}∞1, 2, and by conventional synthetic method for {Rb(HC2O4)}∞3, 3, allowed the identification of H-bond patterns and structural dimensionality. Ferroïc domain structures are confirmed by electric measurements performed on 3. Although 2 resembles one oxalic acid sesquihydrate, its structure determination doesn’t display any kind of disorder and leads to recognition of a supramolecular network identical to hybrid s-block series, where moreover, unusual H3O+ and NH4+ similarity is brought out. Thermal behaviors show that 1D frameworks with extended H-bonds, whether with or without a metal center, have the same stability. Inversely, despite the dimensionalities, the same metallic intermediate and final compounds are obtained for the two Rb+ ferroïc materials. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)
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<p>Thermal evolution of the permittivity ε’<sub>r</sub> for compound <b>3</b>.</p> Full article ">Figure 2
<p>Ortep view showing asymmetric unit and Rb environnement in compound <b>1</b>. Displacement ellipsoids are drawn with 50% probability.</p> Full article ">Figure 3
<p>Molecular view of compound <b>2</b>. Displacement ellipsoids are drawn with 50% probability.</p> Full article ">Figure 4
<p>(a)The centrosymmetrical hydrogen-bonded motif, with graph notation R<sub>6</sub><sup>6</sup>(22), (b)The homosynthon, with graph notation R<sub>4</sub><sup>2</sup>(8) in compound <b>2</b>.</p> Full article ">Figure 5
<p>Ortep view showing cage-like assembly of compound <b>3</b>. Displacement ellipsoids are drawn with 50% probability.</p> Full article ">
609 KiB  
Review
Non-Traditional Aromatic Topologies and Biomimetic Assembly Motifs as Components of Functional Pi-Conjugated Oligomers
by John D. Tovar, Stephen R. Diegelmann and Patricia A. Peart
Materials 2010, 3(2), 1269-1280; https://doi.org/10.3390/ma3021269 - 23 Feb 2010
Cited by 3 | Viewed by 15364
Abstract
This article will highlight our recent work using conjugated oligomers as precursors to electroactive polymer films and self-assembling nanomaterials. One area of investigation has focused on nonbenzenoid aromaticity in the context of charge delocalization in conjugated polymers. In these studies, polymerizable pi-conjugated units [...] Read more.
This article will highlight our recent work using conjugated oligomers as precursors to electroactive polymer films and self-assembling nanomaterials. One area of investigation has focused on nonbenzenoid aromaticity in the context of charge delocalization in conjugated polymers. In these studies, polymerizable pi-conjugated units were coupled onto unusual aromatic cores such as methano[10]annulene. This article will also show how biologically-inspired assembly of molecularly well-defined oligopeptides that flank pi-conjugated oligomers has resulted in the aqueous construction of 1-dimensional nanomaterials that encourage electronic delocalization among the pi-electron systems. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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Figure 1
<p>Annulene (<b>MT and MBT</b>) and naphthalene (<b>NT and NBT</b>) electropolymerizable oligomers (at left), along with the expected polymers formed when n = 1 (at right). The naphthalene is boldened in the aromatic form to emphasize the greater degree of localization observed for naphthyl polymers in their oxidized states.</p> Full article ">Figure 2
<p>Polymer growth profiles plotted relative to Ag/Ag<sup>+</sup> for (a) <b>MT</b>, (b) <b>MBT</b>, (c) <b>NT</b> and (d) <b>NBT</b> were obtained in 0.1 M <span class="html-italic">n</span>-Bu<sub>4</sub>NPF<sub>6</sub>/CH<sub>2</sub>Cl<sub>2</sub> using a 2 mm<sup>2</sup> Pt-button working electrode, coiled Pt wire as the counter electrode, and a silver wire reference electrode submersed in 0.01 M AgNO<sub>3</sub> and 0.1 M TBAP in CH<sub>3</sub>CN. Scan rate = 100 mV/s. Figure taken from reference [<a href="#B14-materials-03-01269" class="html-bibr">14</a>] with permission (Copyright 2008, Wiley-VCH Verlag &amp; Co. KGaA).</p> Full article ">Figure 3
<p>Spectroelectrochemical data obtained on an ITO electrode for (a) poly(<b>MT</b>) between 0–1.1 V, (b) poly(<b>MBT</b>) between 0–1.1 V, (c) poly(<b>NT</b>) between 0–1.2 V and (d) poly(<b>NBT</b>) between 0–1.3 V. Other conditions as listed in <a href="#materials-03-01269-f002" class="html-fig">Figure 2</a>. Figure taken from reference [<a href="#B14-materials-03-01269" class="html-bibr">14</a>] with permission (Copyright 2008, Wiley-VCH Verlag &amp; Co. KGaA).</p> Full article ">Figure 4
<p>A bithiophene amino acid can be included into peptide backbones through classical Fmoc-based solid-phase peptide synthesis leading to self-assembling peptides such as <b>QQEFA</b> and the smaller <b>EAA</b>.</p> Full article ">Figure 5
<p>(A) Circular dichroism and (B) fluorescence of <b>QQEFA</b> in basic (dissolved, black traces) and acidic (assembled, red traces) aqueous solutions. The inset of (B) depicts a concentrated solution (left) and a gel (right) irradiated at 365 nm. Tapping-mode atomic force microscopy images and height profiles of the indicated line trace of (C) large area and (D) isolated structures formed after assembly and deposition on freshly cleaved mica surfaces. Figure taken from reference [<a href="#B36-materials-03-01269" class="html-bibr">36</a>] with permission (Copyright 2008, American Chemical Society).</p> Full article ">
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Review
Magnetic and Optical Properties of Submicron-Size Hollow Spheres
by Quan-Lin Ye, Hirofumi Yoshikawa and Kunio Awaga
Materials 2010, 3(2), 1244-1268; https://doi.org/10.3390/ma3021244 - 21 Feb 2010
Cited by 26 | Viewed by 17411
Abstract
Magnetic hollow spheres with a controlled diameter and shell thickness have emerged as an important class of magnetic nanomaterials. The confined hollow geometry and pronouncedly curved surfaces induce unique physical properties different from those of flat thin films and solid counterparts. In this [...] Read more.
Magnetic hollow spheres with a controlled diameter and shell thickness have emerged as an important class of magnetic nanomaterials. The confined hollow geometry and pronouncedly curved surfaces induce unique physical properties different from those of flat thin films and solid counterparts. In this paper, we focus on recent progress on submicron-size spherical hollow magnets (e.g., cobalt- and iron-based materials), and discuss the effects of the hollow shape and the submicron size on magnetic and optical properties. Full article
(This article belongs to the Special Issue Magnetic Nanoparticles)
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<p>(a) and (b) show the synthetic schemes for preparations of cobalt- and iron-based hollow magnets, respectively; (c) and (d) are typical TEM images for the hollow spheres of Co<sub>3</sub>O<sub>4</sub> and Fe<sub>3</sub>O<sub>4</sub>, respectively; and (e) and (f) are MFM images of surface morphology and magnetic phase of hcp-Co hollow spheres, respectively.</p> Full article ">Figure 2
<p>(a) XRD patterns. (b) <span class="html-italic">M</span>-<span class="html-italic">H</span> curves at 2 K for the ccp- and hcp-Co hollow spheres.</p> Full article ">Figure 3
<p>(a) Temperature dependence of FC magnetizations measured in an applied magnetic field of 50 Oe, after cooling down to 2 K with an external field of 50 kOe. (b) Comparison of the normalized FC magnetizations of 360 and 680 nm Co<sub>3</sub>O<sub>4</sub> hollow spheres.</p> Full article ">Figure 4
<p>Time dependence of the magnetization (<span class="html-italic">M</span> <span class="html-italic">vs.</span> ln<span class="html-italic">t</span>) at 2–25 K for Co<sub>3</sub>O<sub>4</sub> hollow spheres of (a) 360 nm and (b) 680 nm.</p> Full article ">Figure 5
<p>The magnetic viscosity <span class="html-italic">S</span> as a function of temperature for Co<sub>3</sub>O<sub>4</sub> hollow spheres of 360 and 680 nm.</p> Full article ">Figure 6
<p>Hysteresis loops of 360 nm Co<sub>3</sub>O<sub>4</sub> hollow spheres. (a) The FC hysteresis loop measured at 2 K; the inset shows the high field irreversibility of magnetization; (b) The central part of the ZFC (open circle) and FC (solid circle) hysteresis loops measured at 2 K.</p> Full article ">Figure 7
<p>Temperature dependence of the zero-field cooled (ZFC) and field-cooled (FC) magnetizations of the magnetite hollow spheres.</p> Full article ">Figure 8
<p>(a) <span class="html-italic">M</span>-<span class="html-italic">H</span> curves at 2 K, (b) <span class="html-italic">M</span><sub>s</sub> (5 T) <span class="html-italic">vs.</span> <span class="html-italic">T</span>, and (c) <span class="html-italic">H</span><sub>c</sub> <span class="html-italic">vs.</span> <span class="html-italic">T</span> for the magnetite hollow spheres, dense particles and ground NPs. The solid lines in (b) are the best fittings to the Bloch law, while the solid lines in (a) and (c) are the guidance to eye.</p> Full article ">Figure 9
<p>The Day plots of <span class="html-italic">M</span><sub>rs</sub>/<span class="html-italic">M</span><sub>s</sub> versus <span class="html-italic">H</span><sub>cr</sub>/<span class="html-italic">H</span><sub>c</sub> for the hollow spheres, dense particles and ground NPs.</p> Full article ">Figure 10
<p>SEM images of thin films of the hollow (a) and dense (b) spheres. The scale bars are 5 μm in (a) and (b). The insets in (a) and (b) are photographs of the corresponding films. (c) and (d) are <span class="html-italic">M</span>-<span class="html-italic">H</span> curves at 300 K for the thin films of the hollow spheres and the dense particles, respectively, with magnetic field <span class="html-italic">H</span> parallel (blue curves) and perpendicular (red curves) to the film plane (see the inset of (c)). Magnetizations are normalized by the value at 50 kOe.</p> Full article ">Figure 11
<p>(a) and (b) are photographs of the hollow and dense particles, respectively; (c) Diffuse reflectance spectra for the magnetite hollow spheres (green solid curve) and the dense particles (black solid curve). The calculated reflectance spectra based on the theory of Mie scattering for the hollow spheres (green dotted curve) and the dense particles (black dotted curve) reproduce the peak positions of the experimental data. The absolute experimental values are typically not reproduced by the calculations, due to the approximation of the Kubelka-Munk approach.</p> Full article ">Figure 12
<p>Diffusion reflectance spectra for Co<sub>3</sub>O<sub>4</sub> hollow spheres. The green solid and dotted curves represent experimental and simulation data, respectively. The inset photograph shows the light green color of the Co<sub>3</sub>O<sub>4</sub> hollow spheres.</p> Full article ">
208 KiB  
Review
Review: Resin Composite Filling
by Keith H. S. Chan, Yanjie Mai, Harry Kim, Keith C. T. Tong, Desmond Ng and Jimmy C. M. Hsiao
Materials 2010, 3(2), 1228-1243; https://doi.org/10.3390/ma3021228 - 19 Feb 2010
Cited by 68 | Viewed by 24958
Abstract
The leading cause of oral pain and tooth loss is from caries and their treatment include restoration using amalgam, resin, porcelain and gold, endodontic therapy and extraction. Resin composite restorations have grown popular over the last half a century because it can take [...] Read more.
The leading cause of oral pain and tooth loss is from caries and their treatment include restoration using amalgam, resin, porcelain and gold, endodontic therapy and extraction. Resin composite restorations have grown popular over the last half a century because it can take shades more similar to enamel. Here, we discuss the history and use of resin, comparison between amalgam and resin, clinical procedures involved and finishing and polishing techniques for resin restoration. Although resin composite has aesthetic advantages over amalgam, one of the major disadvantage include polymerization shrinkage and future research is needed on reaction kinetics and viscoelastic behaviour to minimize shrinkage stress. Full article
(This article belongs to the Special Issue Molecular Biomimetics and Materials Design)
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<p>Clinical procedures of a direct resin composite restoration.</p> Full article ">
934 KiB  
Review
Carbon-Based Honeycomb Monoliths for Environmental Gas-Phase Applications
by Carlos Moreno-Castilla and Agustín F. Pérez-Cadenas
Materials 2010, 3(2), 1203-1227; https://doi.org/10.3390/ma3021203 - 19 Feb 2010
Cited by 55 | Viewed by 18812
Abstract
Honeycomb monoliths consist of a large number of parallel channels that provide high contact efficiencies between the monolith and gas flow streams. These structures are used as adsorbents or supports for catalysts when large gas volumes are treated, because they offer very low [...] Read more.
Honeycomb monoliths consist of a large number of parallel channels that provide high contact efficiencies between the monolith and gas flow streams. These structures are used as adsorbents or supports for catalysts when large gas volumes are treated, because they offer very low pressure drop, short diffusion lengths and no obstruction by particulate matter. Carbon-based honeycomb monoliths can be integral or carbon-coated ceramic monoliths, and they take advantage of the versatility of the surface area, pore texture and surface chemistry of carbon materials. Here, we review the preparation methods of these monoliths, their characteristics and environmental applications. Full article
(This article belongs to the Special Issue Advances in Materials Science)
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<p>Ceramic honeycomb monoliths with different cell density.</p> Full article ">Figure 2
<p>Preparation steps for carbon-coated HMs.</p> Full article ">Figure 3
<p>SEM microphotographs of carbon-coated HMs prepared by A: air blowing and B: spinning. From reference [<a href="#B20-materials-03-01203" class="html-bibr">20</a>], with permission from Elsevier.</p> Full article ">Figure 4
<p>SEM pictures of the channels (cross section) from α-Al<sub>2</sub>O<sub>3</sub> coated monoliths after the first [(b) and (d)] and the last [(a) and (c)] coating. From reference [<a href="#B17-materials-03-01203" class="html-bibr">17</a>], with permission from Elsevier.</p> Full article ">Figure 5
<p>CNF growth rate at 570 ºC as a function of time on stream from a 200 ml min<sup>-1</sup> gas mixture containing 50% CH<sub>4</sub> and 10% H<sub>2</sub> balance N<sub>2</sub>. Adapted from reference [<a href="#B26-materials-03-01203" class="html-bibr">26</a>], with permission from the Royal Society of Chemistry.</p> Full article ">Figure 6
<p>Preparation steps for integral carbon HMs</p> Full article ">Figure 7
<p>Relationship between the mechanical strength and interparticulate pore volume of the monolith composites. Origin of the commercial activated carbon used in the composite: coal ( <span class="html-fig-inline" id="materials-03-01203-i001"> <img alt="Materials 03 01203 i001" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i001.png"/></span>), nutshell ( <span class="html-fig-inline" id="materials-03-01203-i002"> <img alt="Materials 03 01203 i002" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i002.png"/></span>), wood ( <span class="html-fig-inline" id="materials-03-01203-i003"> <img alt="Materials 03 01203 i003" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i003.png"/></span>) and peat ( <span class="html-fig-inline" id="materials-03-01203-i004"> <img alt="Materials 03 01203 i004" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i004.png"/></span>). From reference [<a href="#B33-materials-03-01203" class="html-bibr">33</a>], with permission from Elsevier.</p> Full article ">Figure 8
<p>Breakthrough profiles for carbon-packed beds and monoliths (31 and 62 cells/cm<sup>2</sup>) ( <span class="html-fig-inline" id="materials-03-01203-i005"> <img alt="Materials 03 01203 i005" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i005.png"/></span>, Norit R1 4.3 g; <span class="html-fig-inline" id="materials-03-01203-i006"> <img alt="Materials 03 01203 i006" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i006.png"/></span>, Norit R1 8.6 g; <span class="html-fig-inline" id="materials-03-01203-i007"> <img alt="Materials 03 01203 i007" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i007.png"/></span>, Norit R1 13 g; <span class="html-fig-inline" id="materials-03-01203-i008"> <img alt="Materials 03 01203 i008" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i008.png"/></span>, (31 cells/cm<sup>2</sup>)-5 cm-5 cm; <span class="html-fig-inline" id="materials-03-01203-i009"> <img alt="Materials 03 01203 i009" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i009.png"/></span>, (31 cells/cm<sup>2</sup>)-5 cm-10 cm; <span class="html-fig-inline" id="materials-03-01203-i010"> <img alt="Materials 03 01203 i010" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i010.png"/></span>, (31 cells/cm<sup>2</sup>)-5 cm-15 cm; <span class="html-fig-inline" id="materials-03-01203-i011"> <img alt="Materials 03 01203 i011" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i011.png"/></span>, (62 cells/cm<sup>2</sup>)-5 cm-5 cm; <span class="html-fig-inline" id="materials-03-01203-i012"> <img alt="Materials 03 01203 i012" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i012.png"/></span>, (62 cells/cm<sup>2</sup>)-5 cm-10 cm; <span class="html-fig-inline" id="materials-03-01203-i013"> <img alt="Materials 03 01203 i013" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i013.png"/></span>, (62 cells/cm<sup>2</sup>)-5 cm-15 cm. From reference [<a href="#B40-materials-03-01203" class="html-bibr">40</a>], with permission from Elsevier.</p> Full article ">Figure 9
<p>The dynamic adsorption efficiency towards o-DCB for different contact times and temperatures: 30 ºC ( <span class="html-fig-inline" id="materials-03-01203-i014"> <img alt="Materials 03 01203 i014" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i014.png"/></span>), 100 ºC ( <span class="html-fig-inline" id="materials-03-01203-i015"> <img alt="Materials 03 01203 i015" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i015.png"/></span>) and 150 ºC ( <span class="html-fig-inline" id="materials-03-01203-i016"> <img alt="Materials 03 01203 i016" src="/materials/materials-03-01203/article_deploy/html/images/materials-03-01203-i016.png"/></span>). From reference [<a href="#B43-materials-03-01203" class="html-bibr">43</a>], with permission from Elsevier.</p> Full article ">Figure 10
<p>Kinetics of CO<sub>2</sub> and CH<sub>4</sub> adsorption on carbon honeycomb HP110 and a commercial carbon molecular sieve CMS. From reference [<a href="#B24-materials-03-01203" class="html-bibr">24</a>], with permission from Elsevier.</p> Full article ">Figure 11
<p>Activity of the catalysts in the m-xylene combustion (μmol of m-xylene burned per gram of Pd and per second). From reference [<a href="#B67-materials-03-01203" class="html-bibr">67</a>], with permission of Elsevier.</p> Full article ">
1437 KiB  
Article
The One-Step Pickering Emulsion Polymerization Route for Synthesizing Organic-Inorganic Nanocomposite Particles
by Huan Ma, Mingxiang Luo, Sriya Sanyal, Kaushal Rege and Lenore L. Dai
Materials 2010, 3(2), 1186-1202; https://doi.org/10.3390/ma3021186 - 16 Feb 2010
Cited by 62 | Viewed by 24067
Abstract
Polystyrene-silica core-shell nanocomposite particles are successfully prepared via one-step Pickering emulsion polymerization. Possible mechanisms of Pickering emulsion polymerization are addressed in the synthesis of polystyrene-silica nanocomposite particles using 2,2-azobis(2-methyl-N-(2-hydroxyethyl)propionamide (VA-086) and potassium persulfate (KPS) as the initiator. Motivated by potential applications [...] Read more.
Polystyrene-silica core-shell nanocomposite particles are successfully prepared via one-step Pickering emulsion polymerization. Possible mechanisms of Pickering emulsion polymerization are addressed in the synthesis of polystyrene-silica nanocomposite particles using 2,2-azobis(2-methyl-N-(2-hydroxyethyl)propionamide (VA-086) and potassium persulfate (KPS) as the initiator. Motivated by potential applications of “smart” composite particles in controlled drug delivery, the one-step Pickering emulsion polymerization route is further applied to synthesize polystyrene/poly(N-isopropylacrylamide) (PNIPAAm)-silica core-shell nanoparticles with N-isopropylacrylamide incorporated into the core as a co-monomer. The polystyrene/PNIPAAm-silica composite nanoparticles are temperature sensitive and can be taken up by human prostate cancer (PC3-PSMA) cells. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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<p>An SEM image <b>(a)</b> of the nanocomposite particles prepared using VA-086 as the initiator and a TEM image <b>(b)</b> of cross-sectioned composite particles.</p> Full article ">Figure 2
<p>Thermogravimetric analysis of the nanocomposite particles prepared using VA-086 as the initiator before (solid line) and after (dashed line) HF etching treatment.</p> Full article ">Figure 3
<p>SEM images <b>(a-b)</b> and the size distribution <b>(c)</b> of polystyrene-silica particles prepared using KPS as the initiator.</p> Full article ">Figure 4
<p>The SEM image and energy dispersive X-ray spectrometry analysis element mapping of a polystyrene-silica particle prepared using KPS as the initiator. Red, green, purple and gold represent carbon, silicon, oxygen, and gold elements, respectively.</p> Full article ">Figure 5
<p>Schematic illustration for possible mechanisms of Pickering emulsion polymerization.</p> Full article ">Figure 6
<p>Plot of particle size <span class="html-italic">versus</span> reaction time and representative SEM images with different initiator VA-086 concentrations: 0.83 wt % (▲, inset images a, b and c), 2.5 wt % (□) and 4.2 wt % (▼, inset images d, e and f). The error bars indicate the width of the particle size distribution and the scale bars represent 100 nm.</p> Full article ">Figure 7
<p>Representative transmitted light images viewed on a confocal microscope of the polymerization system sampled at different time intervals after initiation. The scale bar represents 20 µm.</p> Full article ">Figure 8
<p>The dependence of normalized average diameter of the composite nanoparticles on temperature. The initial diameter at 28 °C for each individual batch is used for normalization. The error bars show standard deviations of particles made in three different batches and the curve smoothly connects the data points.</p> Full article ">Figure 9
<p>Cellular uptake of polystyrene/PNIPAAm core-silica shell nanoparticles by PC3-PSMA prostate cancer cells at low <b>(a)</b> or high <b>(b)</b> nanoparticle dosage. Scale bars represent 20 µm.</p> Full article ">
547 KiB  
Article
Thermal Stability and Sublimation Pressures of Some Ruthenocene Compounds
by M. Aslam Siddiqi, Rehan A. Siddiqui, Burak Atakan, Nina Roth and Heinrich Lang
Materials 2010, 3(2), 1172-1185; https://doi.org/10.3390/ma3021172 - 15 Feb 2010
Cited by 13 | Viewed by 15397
Abstract
We set out to study the use of a series of ruthenocenes as possible and promising sources for ruthenium and/or ruthenium oxide film formation.The thermal stability of a series of ruthenocenes, including (η5-C5H4R)(η5-C [...] Read more.
We set out to study the use of a series of ruthenocenes as possible and promising sources for ruthenium and/or ruthenium oxide film formation.The thermal stability of a series of ruthenocenes, including (η5-C5H4R)(η5-C5H4R´)Ru (1), R = R´ = H (3), R = H, R´ = CH2NMe2 (5), R = H, R´= C(O)Me (6), R = R´ = C(O)Me (7), R = H, R´ = C(O)(CH2)3CO2H (8), R = H, R´ = C(O)(CH2)2CO2H (9), R = H, R´ = C(O)(CH2)3CO2Me (10), R = H, R´= C(O)(CH2)2CO2Me (11), R = R´ = SiMe3), (η5-C4H3O-2,4-Me2)2Ru (2), and (η5-C5H5-2,4-Me2)2Ru (4) was studied by thermogravimetry. From these studies, it could be concluded that 1–4, 6 and 9–11 are the most thermally stable molecules. The sublimation pressure of these sandwich compounds was measured using a Knudsen cell. Among these, the compound 11 shows the highest vapor pressure. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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<p>Ruthenocenes <b>1–11</b>.</p> Full article ">Figure 2
<p>TG curves in the isothermal mode for <b>1</b> and <b>3</b>–<b>5</b> at 95 °C, <b>2</b> at 115 °C, and <b>6</b> at 144 °C.</p> Full article ">Figure 3
<p>TG curves in the isothermal mode for <b>7–10</b> at 143 °C, and <b>11</b> at 90 °C.</p> Full article ">Figure 4
<p>Vapor pressure for <b>1</b>: this work ( <span class="html-fig-inline" id="materials-03-01172-i001"> <img alt="Materials 03 01172 i001" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i001.png"/></span>), Cordes and Schreiner [<a href="#B14-materials-03-01172" class="html-bibr">14</a>] ( <span class="html-fig-inline" id="materials-03-01172-i002"> <img alt="Materials 03 01172 i002" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i002.png"/></span>); <b>4</b>: this work ( <span class="html-fig-inline" id="materials-03-01172-i003"> <img alt="Materials 03 01172 i003" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i003.png"/></span>), Kawano <span class="html-italic">et al.</span> [<a href="#B16-materials-03-01172" class="html-bibr">16</a>,<a href="#B17-materials-03-01172" class="html-bibr">17</a>] ( <span class="html-fig-inline" id="materials-03-01172-i004"> <img alt="Materials 03 01172 i004" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i004.png"/></span>); <b>6</b>: this work ( <span class="html-fig-inline" id="materials-03-01172-i005"> <img alt="Materials 03 01172 i005" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i005.png"/></span>); equation 3 (----).</p> Full article ">Figure 5
<p>Measured vapor pressure for ruthenocenes <b>11</b> ( <span class="html-fig-inline" id="materials-03-01172-i006"> <img alt="Materials 03 01172 i006" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i006.png"/></span>), <b>3</b> ( <span class="html-fig-inline" id="materials-03-01172-i007"> <img alt="Materials 03 01172 i007" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i007.png"/></span>), <b>2</b> ( <span class="html-fig-inline" id="materials-03-01172-i008"> <img alt="Materials 03 01172 i008" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i008.png"/></span>), <b>9</b> ( <span class="html-fig-inline" id="materials-03-01172-i009"> <img alt="Materials 03 01172 i009" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i009.png"/></span>), <b>10</b> ( <span class="html-fig-inline" id="materials-03-01172-i010"> <img alt="Materials 03 01172 i010" src="/materials/materials-03-01172/article_deploy/html/images/materials-03-01172-i010.png"/></span>); equation 3 (----).</p> Full article ">Figure 6
<p>Experimental setup for measuring the vapor pressure.</p> Full article ">
499 KiB  
Article
Tissue Response to, and Degradation Rate of, Photocrosslinked Trimethylene Carbonate-Based Elastomers Following Intramuscular Implantation
by Laurianne Timbart, Man Yat Tse, Stephen C. Pang and Brian G. Amsden
Materials 2010, 3(2), 1156-1171; https://doi.org/10.3390/ma3021156 - 11 Feb 2010
Cited by 14 | Viewed by 14096
Abstract
Cylindrical elastomers were prepared through the UV-initiated crosslinking of terminally acrylated, 8,000 Da star-poly(trimethylene carbonate-co-ε-caprolactone) and star-poly(trimethylene carbonate-co-D,L-lactide). These elastomers were implanted intramuscularly into the hind legs of male Wistar rats to determine the influence of the comonomer on the weight loss, tissue [...] Read more.
Cylindrical elastomers were prepared through the UV-initiated crosslinking of terminally acrylated, 8,000 Da star-poly(trimethylene carbonate-co-ε-caprolactone) and star-poly(trimethylene carbonate-co-D,L-lactide). These elastomers were implanted intramuscularly into the hind legs of male Wistar rats to determine the influence of the comonomer on the weight loss, tissue response, and change in mechanical properties of the elastomer. The elastomers exhibited only a mild inflammatory response that subsided after the first week; the response was greater for the stiffer D,L-lactide-containing elastomers. The elastomers exhibited weight loss and sol content changes consistent with a bulk degradation mechanism. The D,L-lactide-containing elastomers displayed a nearly zeroorder change in Young’s modulus and stress at break over the 30 week degradation time, while the ε-caprolactone-containing elastomers exhibited little change in modulus or stress at break. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
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<p>Relationship between shift factor (a<sub>T</sub>) and elastomer strain at break (σ<sub>b</sub>) and modulus (E).</p> Full article ">Figure 2
<p>Change in weight during implantation time of elastomers prepared from TMC prepolymers copolymerized with either CL or DLLA. The data is expressed as the ratio of the dry weight of the explanted cylinder (m<sub>t</sub>) to its initial, pre-implant dry weight (m<sub>0</sub>).</p> Full article ">Figure 3
<p>(a) Change in wet weight of the implanted TMC-DLLA and TMC:CL cylinders with time. The data is presented as the ratio of the wet (immediately after explantation) weight (m<sub>t</sub>) to the initial dry weight (m<sub>0</sub>). (b) Change in elastomer sol contents with time during implantation.</p> Full article ">Figure 4
<p>Photograph of the explanted cylinders at week 25. The TMC:DLLA cylinder (left) was white and had changed dimension, while the TMC:CL cylinder (right) had remained translucent and had not changed shape.</p> Full article ">Figure 5
<p>Change in mechanical properties of the elastomers with time, measured in uniaxial tension. (a) Change in Young’s modulus (E). (b) Change in stress at break (σ<sub>b</sub>).</p> Full article ">Figure 6
<p>Representative Masson trichrome-stained sections of the tissue surrounding the cylinder implants at week 1 (wk1) and week 25 (wk25). In this staining procedure, collagen stains blue, cytoplasm stains pink/red, muscle stains red, and nuclei stain black. The polymer-tissue interface is indicated by the black arrows.</p> Full article ">Figure 7
<p>Change in the thickness of the zone of inflammation surrounding the implanted elastomer cylinders with respect to time of implantation.</p> Full article ">
1123 KiB  
Review
Bone Substitute Fabrication Based on Dissolution-Precipitation Reactions
by Kunio Ishikawa
Materials 2010, 3(2), 1138-1155; https://doi.org/10.3390/ma3021138 - 10 Feb 2010
Cited by 197 | Viewed by 18874
Abstract
Although block- or granular-type sintered hydroxyapatite are known to show excellent tissue responses and good osteoconductivity, apatite powder elicits inflammatory response. For the fabrication of hydroxyapatite block or granules, sintering is commonly employed. However, the inorganic component of bone and tooth is not [...] Read more.
Although block- or granular-type sintered hydroxyapatite are known to show excellent tissue responses and good osteoconductivity, apatite powder elicits inflammatory response. For the fabrication of hydroxyapatite block or granules, sintering is commonly employed. However, the inorganic component of bone and tooth is not high crystalline hydroxyapatite but low crystalline B-type carbonate apatite. Unfortunately, carbonate apatite powder cannot be sintered due to its instability at high temperature. Another method to fabricate apatite block and/or granule is through phase transformation based on dissolution-precipitation reactions using a precursor phase. This reaction basically is the same as a setting and hardening reaction of calcium sulfate or plaster. In this paper, apatite block fabrication methods by phase transformation based on dissolution-precipitation reactions will be discussed, with a focus on the similarity of the setting and hardening reaction of calcium sulfate. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
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<p>Example of sintered HAp used for the artificial bone substitutes.</p> Full article ">Figure 2
<p>Solubility of α and β calcium sulfate hemihydrate and calcium sulfate dihydrate as a function of temperature [<a href="#B13-materials-03-01138" class="html-bibr">13</a>].</p> Full article ">Figure 3
<p>Typical scanning electron microscopic image of hardened calcium sulfate. Needle-like calcium sulfate dihydrate crystals interlock with each other to form hardened calcium sulfate [<a href="#B13-materials-03-01138" class="html-bibr">13</a>].</p> Full article ">Figure 4
<p>Example of calcium sulfate clinically used for the reconstruction of bone defects (Photo courtesy of Wright Medical Technology).</p> Full article ">Figure 5
<p>Radiographic assessment of OsteoSet(R) resorbable beads filled into the bone void of a 40-year-old female resulting from osteomyelitis, taken at: preoperation (left), postoperation (middle), and follow-up (right). (Photo courtesy of Wright Medical Technology).</p> Full article ">Figure 6
<p>Solubility of Ca and P in various calcium phosphate compounds plotted against the pH calculated from their solubility products [<a href="#B13-materials-03-01138" class="html-bibr">13</a>,<a href="#B14-materials-03-01138" class="html-bibr">14</a>].</p> Full article ">Figure 7
<p>Typical scanning electron microscopic image of apatite cement consisting of TTCP and DCPA. Upper image = surface; lower image = interior [<a href="#B13-materials-03-01138" class="html-bibr">13</a>,<a href="#B14-materials-03-01138" class="html-bibr">14</a>].</p> Full article ">Figure 8
<p>Example of the calcium and phosphate ions concentration in the suspension of apatite cement containing TTCP and DCPA. Calcium ion kept some concentration whereas phosphate concentration became less than detection limit over time [<a href="#B13-materials-03-01138" class="html-bibr">13</a>].</p> Full article ">Figure 9
<p>Histological pictures of carbonate apatite 24 weeks after implantation in a bone defect made to the cranial bone of rats. After 24 weeks, most of the carbonate apatite granules were replaced by new bone. Osteoclastic resorption can be seen along with new bone when carbonate apatite was not replaced.</p> Full article ">Figure 10
<p>Example of cancellous bone. Cancellous bone has fully interconnected porous structure.</p> Full article ">Figure 11
<p>Procedure for the fabrication of α-TCP foam.</p> Full article ">Figure 12
<p>Photographs of specimens of α-TCP foam granules after immersion at 37 °C (top) and after hydrothermal treatment at 100 °C (middle) and 200 °C (bottom) for 24 h [<a href="#B39-materials-03-01138" class="html-bibr">39</a>].</p> Full article ">
107 KiB  
Article
Chemoselectivity in the Dehydrocoupling Synthesis of Higher Molecular Weight Polysilanes
by Florian Lunzer and Christoph Marschner
Materials 2010, 3(2), 1125-1137; https://doi.org/10.3390/ma3021125 - 10 Feb 2010
Cited by 7 | Viewed by 12705
Abstract
The Cp2ZrCl2/2 BuLi catalyzed co-polymerization of H2MeSiSiMeH2 and PhSiH3 was compared to the homo-polymerization of H2MeSiSiPhH2. In contrast to the co-polymerization, which gave molecular weights comparable to homo-polymerization of phenylsilane, the [...] Read more.
The Cp2ZrCl2/2 BuLi catalyzed co-polymerization of H2MeSiSiMeH2 and PhSiH3 was compared to the homo-polymerization of H2MeSiSiPhH2. In contrast to the co-polymerization, which gave molecular weights comparable to homo-polymerization of phenylsilane, the reaction of 1-methyl-2-phenyldisilane yielded a partially cross-linked high molecular weight polymer with very broad molecular weight distribution. A higher reactivity of phenyl-substituted silicon atoms compared to methyl-substituted ones was detected. Stoichiometric reactions of some disilanes with the slow dehydropolymerization catalyst CpCp*Hf(Cl)Si(SiMe3)3 gave metal disilanyl intermediates with selectivities that reflect the observed polymerization behavior. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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<p>GPC-trace of the polymer obtained from the polymerization of 1-methyl-2-phenyldisilane.</p> Full article ">Figure 2
<p>GC/MS analysis of an early stage of the homo-polymerization of 1-methyl-2-phenyldisilane. <sup>a</sup></p> Full article ">Figure 3
<p>Enhanced reactivity of the phenylsilyl unit compared to the methylsilyl unit. Preferred transition states and isomers (all hydrogen atoms on silicon omitted for clarity) printed bold.</p> Full article ">Figure 4
<p><sup>29</sup>Si{H} INEPT-NMR spectrum of CpCp*Hf(Cl)SiHPhSiMeH<sub>2</sub>/CpCp*Hf(Cl)-SiHMeSiPhH<sub>2</sub>.</p> Full article ">
537 KiB  
Article
Innovative Use and Characterization of Polymers for Timber-Related Construction
by Antony Darby, Tim Ibell and Mark Evernden
Materials 2010, 3(2), 1104-1124; https://doi.org/10.3390/ma3021104 - 10 Feb 2010
Cited by 7 | Viewed by 14225
Abstract
Timber gridshells have become a very popular, efficient, sustainable and beautiful structural application of timber. However, given the slender laths involved in this form of construction, there is concern over the durability of timber for this purpose, and Glass FRP (GFRP) laths have [...] Read more.
Timber gridshells have become a very popular, efficient, sustainable and beautiful structural application of timber. However, given the slender laths involved in this form of construction, there is concern over the durability of timber for this purpose, and Glass FRP (GFRP) laths have been proposed as a possible substitution. This paper considers this possibility. It goes on to look at the possible use of Basalt FRP (BFRP) for the same purpose, from the perspective of its creep characteristics. It is shown that the use of GFRP gridshells is a viable form of construction, and that enhanced durability characteristics of BFRP could lead to their adoption for gridshells, given that the creep characteristics of basalt fibres presented here are comparable to those of glass fibres. An altogether different form of timber construction is that of joist-and-floorboard. In the UK, there are thousands of historic buildings which use this floor construction, and a sizeable proportion of this building stock now requires upgrade, strengthening and/or stiffening to allow these buildings to be fit for purpose into the future. This paper goes on to consider the possible use of Carbon FRP (CFRP) to strengthen and stiffen such timber floors. It is shown that such strengthening and stiffening is entirely feasible, offering the potential for greatly enhanced stiffness, in particular. Further, it is shown that mechanical shear connection between CFRP and timber is best conducted using perpendicular-positioned screws, rather than raked screws. Full article
(This article belongs to the Special Issue Composite Materials)
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<p>Quadruple layer gridshell element.</p> Full article ">Figure 2
<p>Single layer gridshell constructed of GFRP poles [<a href="#B9-materials-03-01104" class="html-bibr">9</a>].</p> Full article ">Figure 3
<p>(a) 3-D representation of the FEA model. (b) Arrangement of beam elements at connections.</p> Full article ">Figure 4
<p>Exaggerated deflected shape under combined snow and wind loading.</p> Full article ">Figure 5
<p>Exaggerated deflected shape under ultimate funicular load.</p> Full article ">Figure 6
<p>Fibre clamping arrangement.</p> Full article ">Figure 7
<p>Tenacity (ABL/tex) against strand linear density (tex).</p> Full article ">Figure 8
<p>Creep rupture test results.</p> Full article ">Figure 9
<p>Creep strain curve (65% ABL).</p> Full article ">Figure 10
<p>Creep strain curves – all tests on log time scale.</p> Full article ">Figure 11
<p>Breaking strain plotted against %ABL.</p> Full article ">Figure 12
<p>(a) Joist only. (b) Joist with 4mm-thick CFRP topping.</p> Full article ">Figure 13
<p>Layering-up of the FRP topping using two plates of 2 mm-thick CFRP and two plates of 3 mm-thick GFRP.</p> Full article ">Figure 14
<p>(a) Front view of Specimen 1. (b) Side view of Specimen 1. (c) Specimen 2. (d) Specimen 3 (e) Specimen 4.</p> Full article ">Figure 15
<p>(a) Front view of specimen in test rig. (b) Side view of specimen in test rig.</p> Full article ">Figure 16
<p>Load-Displacement plots for all four specimens.</p> Full article ">
625 KiB  
Article
A Route for Polymer Nanocomposites with Engineered Electrical Conductivity and Percolation Threshold
by Kyriaki Kalaitzidou, Hiroyuki Fukushima and Lawrence T. Drzal
Materials 2010, 3(2), 1089-1103; https://doi.org/10.3390/ma3021089 - 9 Feb 2010
Cited by 106 | Viewed by 17923
Abstract
Polymer nanocomposites with engineered electrical properties can be made by tuning the fabrication method, processing conditions and filler’s geometric and physical properties. This work focuses on investigating the effect of filler’s geometry (aspect ratio and shape), intrinsic electrical conductivity, alignment and dispersion within [...] Read more.
Polymer nanocomposites with engineered electrical properties can be made by tuning the fabrication method, processing conditions and filler’s geometric and physical properties. This work focuses on investigating the effect of filler’s geometry (aspect ratio and shape), intrinsic electrical conductivity, alignment and dispersion within the polymer, and polymer crystallinity, on the percolation threshold and electrical conductivity of polypropylene based nanocomposites. The conductive reinforcements used are exfoliated graphite nanoplatelets, carbon black, vapor grown carbon fibers and polyacrylonitrile carbon fibers. The composites are made using melt mixing followed by injection molding. A coating method is also employed to improve the nanofiller’s dispersion within the polymer and compression molding is used to alter the nanofiller’s alignment. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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<p>Electrical conductivity of carbon reinforced PP composites as a function of the filler loading.</p> Full article ">Figure 2
<p>ESEM images of fracture surface of 1 vol % xGnP-15/PP (a) xGnP-15 agglomerates (scale bar 50 μm) and (b) xGnP-15 “roll-up” (scale bar 5 μm).</p> Full article ">Figure 3
<p>Effect of filler orientation on the percolation threshold and conductivity of xGnP-PP nanocomposites.</p> Full article ">Figure 4
<p>Schematic representation of filler distribution in the polymer matrix: (a) filler orientation along the flow direction in injection-molded specimen, and (b) random filler orientation in a compression-molded specimen.</p> Full article ">Figure 5
<p>Schematic of molds used to explore the effect of xGnP anisotropy. The red arrow shows the direction of measurement (a) along the flow direction, parallel to the graphite plane and (b) normal to the flow, parallel to graphite c-axis.</p> Full article ">Figure 6
<p>Effect of filler anisotropy on the percolation threshold and conductivity of xGnP-PP nanocomposites.</p> Full article ">Figure 7
<p>Orientation of xGnP in a disk shape xGnP-15/PP, (a) ESEM image (scale bar 450 μm) (b) schematic representation of the xGnP orientation along the flow front.</p> Full article ">Figure 8
<p>Effect of compounding on the percolation threshold and conductivity of xGnP-1-PP nanocomposites made by compression molding.</p> Full article ">Figure 9
<p>Percolation threshold and electrical conductivity of xGnP/PP nanocomposites made by coating (premixing) and compression molding.</p> Full article ">Figure 10
<p>Effect of compounding on the percolation threshold and conductivity of xGnP-15-PP made by injection molding.</p> Full article ">Figure 11
<p>Effect of cooling rate (crystallization behavior of polymer matrix) on the electrical conductivity of xGnP/PP nanocomposites made by coating (premixing) and compression molding).</p> Full article ">
2741 KiB  
Review
Organometallic Routes into the Nanorealms of Binary Fe-Si Phases
by Manoj K. Kolel-Veetil and Teddy M. Keller
Materials 2010, 3(2), 1049-1088; https://doi.org/10.3390/ma3021049 - 9 Feb 2010
Cited by 26 | Viewed by 17498
Abstract
The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, a-FeSi2 and b-FeSi [...] Read more.
The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, a-FeSi2 and b-FeSi2. While the iron-rich silicides Fe3Si and Fe5Si3 are known to be room temperature ferromagnets, the stoichiometric FeSi is the only known transition metal Kondo insulator. Furthermore, Fe5Si3 has also been demonstrated to exhibit giant magnetoresistance (GMR). The silicon-rich b-FeSi2 is a direct band gap material usable in light emitting diode (LED) applications. Typically, these silicides are synthesized by traditional solid-state reactions or by ion beam-induced mixing (IBM) of alternating metal and silicon layers. Alternatively, the utilization of organometallic compounds with reactive transition metal (Fe)-carbon bonds has opened various routes for the preparation of these silicides and the silicon-stabilized bcc- and fcc-Fe phases contained in the Fe-Si binary phase diagram. The unique interfacial interactions of carbon with the Fe and Si components have resulted in the preferential formation of nanoscale versions of these materials. This review will discuss such reactions. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Fe-Si phase diagram. Reproduced from Ref. [<a href="#B12-materials-03-01049" class="html-bibr">12</a>] with permission from Butterworths &amp; Co., London.</p> Full article ">Figure 2
<p>Schematic representations of the Vapor-Liquid-Solid (VLS), Liquid-Liquid-Solid (LLS) and Solid-Liquid-Solid (SLS) mechanisms. VLS and LLS mechanisms, adapted from Ref. [<a href="#B45-materials-03-01049" class="html-bibr">45</a>] with permission from The American Association for Advancement of Science, and SLS mechanism, adapted from Ref. [<a href="#B47-materials-03-01049" class="html-bibr">47</a>] with permission from Elsevier.</p> Full article ">Figure 3
<p>(Top) The reaction to form the organometallic product. (Bottom) The possible structures of the product formed from the reaction, with <b>2</b> and <b>4</b> being the probably formed ones based on elemental analysis and IR spectroscopy. From Ref. [<a href="#B62-materials-03-01049" class="html-bibr">62</a>], Adapted by permission of The Royal Society of Chemistry.</p> Full article ">Figure 4
<p>(a) TEM photograph of a 1000 °C sample, (b) TEM photograph of a spherical metallic particle, and (c) BEI photograph of an interfacial melting zone observed in a 1400 °C sample. From Ref. [<a href="#B62-materials-03-01049" class="html-bibr">62</a>], Reproduced by permission of The Royal Society of Chemistry.</p> Full article ">Figure 5
<p>The methyl-containing hyperbranched poly[1,1’-ferrocenylene(methyl)silyne], <b>6</b>, used in the production of the Fe<sub>3</sub>Si-containing product <b>7A</b>. Shown, also, are the variants of <b>6</b> that were utilized in the study. Adapted from Ref. [<a href="#B65-materials-03-01049" class="html-bibr">65</a>] with permission from American Chemical Society.</p> Full article ">Figure 6
<p>Ring opening polymerizations (ROP) of 1,1-ferrocenylene(dimethyl)silylene (<b>8A</b>) and spirocyclic[1]-ferrocenophane (<b>8B</b>) that produce the respective crosslinked networks. Adapted from Ref. [<a href="#B68-materials-03-01049" class="html-bibr">68</a>] with permission from American Chemical Society.</p> Full article ">Figure 7
<p>Representation of a nucleation and growth model that illustrates the genesis of the magnetic ceramic <b>10N</b> from (i) the iron atom release from polymer <b>8B</b> followed by (ii) nucleation and growth of iron nanoparticles. Reproduced from Ref. [<a href="#B68-materials-03-01049" class="html-bibr">68</a>] with permission from American Chemical Society.</p> Full article ">Figure 8
<p>The diacetylene-containing ferrocenylsiloxane polymer <b>FS</b> and its conversion into a thermoset by heating. Adapted from Ref. [<a href="#B8-materials-03-01049" class="html-bibr">8</a>] with permission from American Chemical Society.</p> Full article ">Figure 9
<p>(Left) A HRTEM image showing bcc-Fe nanoparticles with protruding carbon fibers, (a) a HAADF image of two bcc-Fe particles encapsulated by carbon, (c) an EDS line scan across the two particles showing the presence of Fe, and (b) and (d) fine probe EDS maps for Fe and Si (present dispersed in the matrix), respectively. (Right) (a) A HRTEM image showing a Fe<sub>5</sub>Si<sub>3</sub> particle encapsulated by a carbon nanocapsule, (b) a high magnification of a portion of the carbon nanocapsule showing the (0002) lattice fringes, (c) a HAADF image of two Fe<sub>5</sub>Si<sub>3</sub> particles encapsulated by carbon, (e) an EDS line scan across the two particles showing the presence of Fe and Si, and (d) and (f) fine probe EDS maps for Fe and Si, respectively. Reproduced from [<a href="#B8-materials-03-01049" class="html-bibr">8</a>] with permission from American Chemical Society.</p> Full article ">Figure 10
<p>The magnetization of the Fe<sub>5</sub>Si<sub>3</sub> nanoparticle-containing product (left) and the silicon-doped bcc-Fe nanoparticle-containing product (right) as a function of the magnetic field; the hysteresis loop being depicted. Reproduced from Ref. [<a href="#B8-materials-03-01049" class="html-bibr">8</a>] with permission from American Chemical Society.</p> Full article ">Figure 11
<p>Structures of the typical organometallics used in the formation of FeSi, such as Fe(CO)<sub>5</sub> (Iron pentacarbonyl), Fe(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> (Ferrocene), <span class="html-italic">cis</span>-Fe(SiCl<sub>3</sub>)<sub>2</sub>(CO)<sub>4</sub>, <span class="html-italic">trans</span>-Fe(SiCl<sub>3</sub>)<sub>2</sub>(CO)<sub>4</sub>, Si<sub>2</sub>H<sub>6</sub> (Disilane) and Si(111) surface.</p> Full article ">Figure 12
<p>(a) FeSi NW growth from single-source precursor <span class="html-italic">trans</span>-Fe(CO)<sub>4</sub>(SiCl<sub>3</sub>)<sub>2</sub>. Representative SEM images of FeSi NWs: (b) over the edge of the growth substrate; (c) over the substrate; and (d) a close up view highlighting the NW tips. Reproduced from Ref. [<a href="#B84-materials-03-01049" class="html-bibr">84</a>] with permission from American Chemical Society.</p> Full article ">Figure 13
<p>(Left) Spectroscopic characterization of FeSi nanowires by X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES) at the Fe <span class="html-italic">L</span><sub>2,3</sub> edge. The black arrows point to the excitation energy (top) and the elastic peak (bottom). (Right) Room-temperature transport properties of FeSi NWs in two-terminal devices. (a) <span class="html-italic">I</span><sub>sd</sub> vs <span class="html-italic">V</span><sub>sd</sub> for several typical FeSi NW devices. (Insets) SEM images of a typical device. (b) Histogram of observed resistance for 47 single FeSi NW devices. (c) <span class="html-italic">I</span><sub>sd</sub> vs <span class="html-italic">V</span><sub>g</sub> recorded for a typical FeSi NW device that breaks down at higher voltage and current. (Inset) SEM image of this particular device after failure. The arrow highlights the breaking point. Reproduced from Ref. [<a href="#B84-materials-03-01049" class="html-bibr">84</a>] with permission from American Chemical Society.</p> Full article ">Figure 14
<p>Characteristic structures formed by Fe(CO)<sub>5</sub> adsorption on Si(111)7×7 (15 nm)<sup>2</sup> as obtained from STM studies. Grey ring: Si(111)7×7 adatoms, White ring: adsorption sites. Reprinted with permission from Ref. [<a href="#B88-materials-03-01049" class="html-bibr">88</a>]. Copyright 1998, American Vacuum Society.</p> Full article ">Figure 15
<p>TEM images of the cross section of the substrates. (Left) (a) SiO<sub>2</sub> area after CVD growth and removing of carbon nanotubes. (b) Si area without any nanotube growth but precipitate of submicron-size particles near the surface. (c) Enlarged picture from the nanotube/SiO<sub>2</sub> interface in (a) showing the formation of gamma iron particles on silicon oxide surface and the growth of nanotubes from the particles formed. (d) Enlarged area from (b) showing the formation of iron silicide and iron silicate crystals during CVD processing. Corresponding schematics are also illustrated. (Right) The panels on the right hand side depicts, selective area diffraction patterns from the particles on the oxide surface (c) and on the Si surface (d), indicating gamma iron (fcc-Fe) formation and iron silicide and iron silicate formation during the CVD process on silicon oxide surface and silicon surface, respectively. Reproduced from Ref. [<a href="#B96-materials-03-01049" class="html-bibr">96</a>] with permission from American Chemical Society.</p> Full article ">Figure 16
<p>(a)–(d) Pane-view and (e) and (f) cross-sectional SEM images of MOCVD-overgrown films deposited on Si (111) substrates with ((a), (c), (e)) 20- or ((b), (d), (f)) 50-nm-thick templates; (a) and (b) after 100 nm MOCVD-overgrowth at 750 °C; (c)–(f): after 200 nm MOCVD-overgrowth at 750 °C. Reproduced from Ref. [<a href="#B106-materials-03-01049" class="html-bibr">106</a>] with permission from Elsevier.</p> Full article ">Figure 17
<p>(Left) Square lattice photonic crystal with hexagonal columns of <span class="html-italic">β</span>-FeSi<sub>2</sub> fabricated by an NLD-plasma etching process. (Right) Reflectance spectrum of polarized incident light at the Brewster angle. (Middle) A polarized light at the wavelength corresponding to the photonic band-gaps cannot propagate into the photonic crystal along any direction. Therefore, the reflectance becomes larger than the usual reflectance of the s-polarized light at the Brewster angle. Reproduced from Ref. [<a href="#B108-materials-03-01049" class="html-bibr">108</a>] with permission from Elsevier Science.</p> Full article ">Figure 18
<p>(Left) TEM micrographs of iron silicide nano-rods grown on a Si(111) substrate. (a) A nano-rod of high aspect ratio, and (b) nano-hexagons. Both types of rods grow parallel to the Si(110) direction. (Right) A TEM micrograph of iron silicide islands grown on a Si(111) edge plane at about 700 K. While islands A retain the plane spacings and plane angles of the Si substrates, islands B seems to have a different structure. Reproduced from Ref. [<a href="#B110-materials-03-01049" class="html-bibr">110</a>] with permission from Springer Netherlands.</p> Full article ">Figure 19
<p>Representation of pathways to form nanoparticles of silicon-doped bcc-Fe and Fe<sub>5</sub>Si<sub>3</sub>, respectively, at slower and faster pyrolysis rates. Adapted from Ref. [<a href="#B8-materials-03-01049" class="html-bibr">8</a>] with permission from American Chemical Society.</p> Full article ">Figure 20
<p>The two cascading reactions resulting from the initial CO or SiCl<sub>4</sub> elimination from <span class="html-italic">cis</span>-Fe(SiCl<sub>3</sub>)<sub>2</sub>(CO)<sub>4</sub> to produce FeSi films. Adapted from Ref. [<a href="#B83-materials-03-01049" class="html-bibr">83</a>] with permission from American Chemical Society.</p> Full article ">Figure 21
<p>Schematic diagram of crystal growth of MOCVD-overgrown <span class="html-italic">β</span>-FeSi<sub>2</sub> films on aggregated templates. Adapted from Ref. [<a href="#B107-materials-03-01049" class="html-bibr">107</a>] with permission from Elsevier.</p> Full article ">
1414 KiB  
Article
Effect of Microstructure Evolution on the Overall Response of Porous-Plastic Solids
by Stefano Mariani
Materials 2010, 3(2), 1031-1048; https://doi.org/10.3390/ma3021031 - 4 Feb 2010
Viewed by 13937
Abstract
Ductile fracture is the macroscopic result of a micromechanical process consisting in void nucleation and growth to coalescence. While growing in size, voids also evolve in shape because of the non-uniform deformation field in the surrounding material; this shape evolution is either disregarded [...] Read more.
Ductile fracture is the macroscopic result of a micromechanical process consisting in void nucleation and growth to coalescence. While growing in size, voids also evolve in shape because of the non-uniform deformation field in the surrounding material; this shape evolution is either disregarded or approximately accounted for by constitutive laws for porous-plastic solids. To assess the effect of void distortion on the overall properties of a porous-plastic material prior to any coalescence-dominated event, we here present a micromechanical study in which the void-containing material is treated as a two-phase (matrix and inclusion) composite. A cylindrical representative volume element (RVE), featuring elliptic cross-section and containing a coaxial and confocal elliptic cylindrical cavity, is considered. In case of a matrix obeying J2 flow theory of plasticity, the overall yield domain and the evolution laws for the volume fraction and aspect ratio of the void are obtained. Under assigned strain histories, these theoretical findings are then compared to finite element unit-cell simulations, in order to assess the capability of the proposed results to track microstructure evolution. The improvements with respect to the customarily adopted Gurson’s model are also discussed. Full article
(This article belongs to the Special Issue Composite Materials)
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Figure 1

Figure 1
<p>Geometry of the considered representative volume element.</p> Full article ">Figure 2
<p>Overall yield condition in the <math display="inline"> <mrow> <msub> <mo>Σ</mo> <mn>11</mn> </msub> <mo>−</mo> <msub> <mo>Σ</mo> <mn>22</mn> </msub> <mo>−</mo> <msub> <mo>Σ</mo> <mn>33</mn> </msub> </mrow> </math> space, at varying <span class="html-italic">λ</span> <math display="inline"> <mrow> <mo>(</mo> <mi>f</mi> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>05</mn> <mo>)</mo> </mrow> </math>.</p> Full article ">Figure 3
<p>Undeformed RVE cross-sections at <math display="inline"> <mrow> <msub> <mi>f</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>01</mn> </mrow> </math> and varying void aspect ratio <math display="inline"> <msub> <mi>λ</mi> <mn>0</mn> </msub> </math> (measures in mm). As a reference, in this figure the volume <span class="html-italic">V</span> (see Equations <a href="#FD1-materials-03-01031" class="html-disp-formula">1</a>) and the out-of-plane thickness <span class="html-italic">L</span> of the RVE has been respectively assumed <math display="inline"> <mrow> <mi>V</mi> <mo>=</mo> <mn>1</mn> </mrow> </math> mm<math display="inline"> <msup> <mrow/> <mn>3</mn> </msup> </math> and <math display="inline"> <mrow> <mi>L</mi> <mo>=</mo> <mn>1</mn> </mrow> </math> mm.</p> Full article ">Figure 4
<p>Effect of the initial aspect ratio <math display="inline"> <msub> <mi>λ</mi> <mn>0</mn> </msub> </math> on the nonlinear response of the orthotropic porous-plastic solid at <math display="inline"> <mrow> <msub> <mi>k</mi> <mi>ε</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>0</mn> </mrow> </math>. Comparison among the proposed constitutive model (black lines), the Gurson’s model (orange line), and unit-cell simulations (blue symbols) in terms of: (a) Cauchy stress <math display="inline"> <msub> <mo>Σ</mo> <mn>11</mn> </msub> </math> <span class="html-italic">vs</span> logarithmic strain <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>; (b) Cauchy stress <math display="inline"> <msub> <mo>Σ</mo> <mn>22</mn> </msub> </math> <span class="html-italic">vs</span> logarithmic strain <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>; (c) void volume fraction <span class="html-italic">f</span> <span class="html-italic">vs</span> <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>; (d) void aspect ratio <span class="html-italic">λ</span> <span class="html-italic">vs</span> <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>.</p> Full article ">Figure 5
<p>Effect of the initial aspect ratio <math display="inline"> <msub> <mi>λ</mi> <mn>0</mn> </msub> </math> on the nonlinear response of the orthotropic porous-plastic solid at <math display="inline"> <mrow> <msub> <mi>k</mi> <mi>ε</mi> </msub> <mo>=</mo> <mo>−</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </math>. Comparison among the proposed constitutive model (black lines), the Gurson’s model (orange line), and unit-cell simulations (blue symbols) in terms of: (a) Cauchy stress <math display="inline"> <msub> <mo>Σ</mo> <mn>11</mn> </msub> </math> <span class="html-italic">vs</span> logarithmic strain <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>; (b) Cauchy stress <math display="inline"> <msub> <mo>Σ</mo> <mn>22</mn> </msub> </math> <span class="html-italic">vs</span> logarithmic strain <math display="inline"> <msub> <mi>E</mi> <mn>22</mn> </msub> </math>; (c) void volume fraction <span class="html-italic">f</span> <span class="html-italic">vs</span> <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>; (d) void aspect ratio <span class="html-italic">λ</span> <span class="html-italic">vs</span> <math display="inline"> <msub> <mi>E</mi> <mn>11</mn> </msub> </math>.</p> Full article ">Figure 6
<p><math display="inline"> <mrow> <msub> <mi>f</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>01</mn> </mrow> </math>, <math display="inline"> <mrow> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>3</mn> </mrow> </math>. Microstructure evolution under <math display="inline"> <mrow> <msub> <mi>k</mi> <mi>ε</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>0</mn> </mrow> </math>, as obtained with the unit-cell simulation.</p> Full article ">Figure 7
<p><math display="inline"> <mrow> <msub> <mi>f</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>01</mn> </mrow> </math>, <math display="inline"> <mrow> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mo>=</mo> <mn>3</mn> </mrow> </math>. Microstructure evolution under <math display="inline"> <mrow> <msub> <mi>k</mi> <mi>ε</mi> </msub> <mo>=</mo> <mo>−</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </math>, as obtained with the unit-cell simulation.</p> Full article ">Figure 8
<p>Effect of the initial aspect ratio <math display="inline"> <msub> <mi>λ</mi> <mn>0</mn> </msub> </math> on the peak values of Chauchy stresses <math display="inline"> <msub> <mo>Σ</mo> <mn>11</mn> </msub> </math> (circles) and <math display="inline"> <msub> <mo>Σ</mo> <mn>22</mn> </msub> </math> (squares), under (a) <math display="inline"> <mrow> <msub> <mi>k</mi> <mi>ε</mi> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>0</mn> </mrow> </math>, and (b) <math display="inline"> <mrow> <msub> <mi>k</mi> <mi>ε</mi> </msub> <mo>=</mo> <mo>−</mo> <mn>0</mn> <mo>.</mo> <mn>5</mn> </mrow> </math>.</p> Full article ">
511 KiB  
Article
Silicoaluminates as “Support Activator” Systems in Olefin Polymerization Processes
by Vanessa Tabernero, Claudimar Camejo, Pilar Terreros, María Dolores Alba and Tomás Cuenca
Materials 2010, 3(2), 1015-1030; https://doi.org/10.3390/ma3021015 - 3 Feb 2010
Cited by 18 | Viewed by 15805
Abstract
In this work we report the polymerization behaviour of natural clays (montmorillonites, MMT) as activating supports. These materials have been modified by treatment with different aluminium compounds in order to obtain enriched aluminium clays and to modify the global Brönsted/Lewis acidity. As a [...] Read more.
In this work we report the polymerization behaviour of natural clays (montmorillonites, MMT) as activating supports. These materials have been modified by treatment with different aluminium compounds in order to obtain enriched aluminium clays and to modify the global Brönsted/Lewis acidity. As a consequence, the intrinsic structural properties of the starting materials have been changed. These changes were studied and these new materials used for ethylene polymerization using a zirconocene complex as catalyst. All the systems were shown to be active in ethylene polymerization. The catalyst activity and the dependence on acid strength and textural properties have been also studied. The behaviour of an artificial silica (SBA 15) modified with an aluminium compound to obtain a silicoaluminate has been studied, but no ethylene polymerization activity has been found yet. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>XRD of acid treated montmorillonites: (a) K10; (b) K30. m = montmorillonite (PDF 3-0015); p = phengite 2M<sub>1</sub> (PDF 76-0928); a = albite (PDF=41-1480); q = quartz (PDF 78-2315).</p> Full article ">Figure 2
<p>SEM microphotographs and EDX spectra of acid treated montmorillonites lamellar particles (a), (c): K10; (b), (d): K30.</p> Full article ">Figure 3
<p><sup>29</sup>Si- (left) and <sup>27</sup>Al- (right) MAS-NMR spectra of acid treated montmorillonites (a): K10; (b): K30.</p> Full article ">Figure 4
<p>XRD in inert atmosphere of acid treated montmorillonites (a) K10; (b) K10/TMA; (c): K10/TEA; (d) K30; (e) K30/TMA; (f) K30/TEA; a = albite; q = quartz.</p> Full article ">Figure 5
<p><sup>29</sup>Si- (top) and <sup>27</sup>Al- (bottom) MAS-NMR spectra of acid treated montmorillonites (a) K10; (b) K10/TMA; (c) K10/TEA; (d) K30; (e) K30/ TMA; (f) K30/TEA.</p> Full article ">Figure 6
<p>Evaluation of acidity from the IR/FT spectra of samples after pyridine sorption and degassed at 200 °C.</p> Full article ">Figure 7
<p>Different activation pathways of precatalyst complexes considering the different nature of the acidic sites in the support activator.</p> Full article ">
246 KiB  
Review
A Review of Keratin-Based Biomaterials for Biomedical Applications
by Jillian G. Rouse and Mark E. Van Dyke
Materials 2010, 3(2), 999-1014; https://doi.org/10.3390/ma3020999 - 3 Feb 2010
Cited by 545 | Viewed by 35753
Abstract
Advances in the extraction, purification, and characterization of keratin proteins from hair and wool fibers over the past century have led to the development of a keratin-based biomaterials platform. Like many naturally-derived biomolecules, keratins have intrinsic biological activity and biocompatibility. In addition, extracted [...] Read more.
Advances in the extraction, purification, and characterization of keratin proteins from hair and wool fibers over the past century have led to the development of a keratin-based biomaterials platform. Like many naturally-derived biomolecules, keratins have intrinsic biological activity and biocompatibility. In addition, extracted keratins are capable of forming self-assembled structures that regulate cellular recognition and behavior. These qualities have led to the development of keratin biomaterials with applications in wound healing, drug delivery, tissue engineering, trauma and medical devices. This review discusses the history of keratin research and the advancement of keratin biomaterials for biomedical applications. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
5214 KiB  
Review
Porous Silicon—A Versatile Host Material
by Petra Granitzer and Klemens Rumpf
Materials 2010, 3(2), 943-998; https://doi.org/10.3390/ma3020943 - 3 Feb 2010
Cited by 169 | Viewed by 22342
Abstract
This work reviews the use of porous silicon (PS) as a nanomaterial which is extensively investigated and utilized for various applications, e.g., in the fields of optics, sensor technology and biomedicine. Furthermore the combination of PS with one or more materials which are [...] Read more.
This work reviews the use of porous silicon (PS) as a nanomaterial which is extensively investigated and utilized for various applications, e.g., in the fields of optics, sensor technology and biomedicine. Furthermore the combination of PS with one or more materials which are also nanostructured due to their deposition within the porous matrix is discussed. Such nanocompounds offer a broad avenue of new and interesting properties depending on the kind of involved materials as well as on their morphology. The filling of the pores performed by electroless or electrochemical deposition is described, whereas different morphologies, reaching from micro- to macro pores are utilized as host material which can be self-organized or fabricated by prestructuring. For metal-deposition within the porous structures, both ferromagnetic and non-magnetic metals are used. Emphasis will be put on self-arranged mesoporous silicon, offering a quasi-regular pore arrangement, employed as template for filling with ferromagnetic metals. By varying the deposition parameters the precipitation of the metal structures within the pores can be tuned in geometry and spatial distribution leading to samples with desired magnetic properties. The correlation between morphology and magnetic behaviour of such semiconducting/magnetic systems will be determined. Porous silicon and its combination with a variety of filling materials leads to nanocomposites with specific physical properties caused by the nanometric size and give rise to a multiplicity of potential applications in spintronics, magnetic and magneto-optic devices, nutritional food additives as well as drug delivery. Full article
(This article belongs to the Special Issue Porous Materials)
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Figure 1
<p>Dynamic response of mesoporous silicon samples of different porosity, varying between 38% and 75% to NO<sub>2</sub> (diagram taken from [<a href="#B47-materials-03-00943" class="html-bibr">47</a>]).</p> Full article ">Figure 2
<p>Scheme of a porous silicon double-layer with two different pore-diameters employed as bio-sensor which detects the molecules dependent on their size (after [<a href="#B48-materials-03-00943" class="html-bibr">48</a>]).</p> Full article ">Figure 3
<p>Scanning electron micrographs showing (a) a plan view macropore covered by a SiO<sub>2</sub> layer and a deposited polysilicon layer acting as top electrode and (b) the corresponding cross-sectional view (image taken from [<a href="#B51-materials-03-00943" class="html-bibr">51</a>]).</p> Full article ">Figure 4
<p>Self-ordered porous alumina template formed under 27 V anodizing potential. Image taken from (reproduced by permission of The Electrochemical Society [<a href="#B61-materials-03-00943" class="html-bibr">61</a>]).</p> Full article ">Figure 5
<p>Diagram corresponding to <a href="#materials-03-00943-t001" class="html-table">Table 1</a>, showing the parameters thickness of the porous layer and the growth rate in dependence on the time.</p> Full article ">Figure 6
<p>(a) Top view of a porous silicon sample with an average pore-diameter of 55 nm. (b) Pore-size distribution showing the deviation from the average pore-diameter being about 10%.</p> Full article ">Figure 7
<p>Morphology of the porous silicon template varied by the applied current density [<a href="#B83-materials-03-00943" class="html-bibr">83</a>]. As starting material a (100) n<sup>+</sup>-Si wafer is used. (a) Pore-diameter ~95 nm ±10 nm, pore-distance ~45 nm; (b) Pore-diameter ~60 nm ±8 nm, pore-distance ~50 nm; (c) Pore-diameter ~45 nm ±10 nm, pore-distance ~55 nm; (d) Pore-diameter ~25 nm, pore-distance ~60 nm; (e) random pore size distribution.</p> Full article ">Figure 8
<p>Fourier Transform images corresponding to the top view pictures of <a href="#materials-03-00943-f003" class="html-fig">Figure 3</a>a–d (images a and b are taken from [<a href="#B83-materials-03-00943" class="html-bibr">83</a>]. The four fold symmetry of the self-assembled pore arrangement can be recognized. The regularity deceases with decreasing pore-diameter and vanishes below a certain value.</p> Full article ">Figure 9
<p>Decreasing pore-diameter and porosity with decreasing current density. The pore-distance is enhanced with decreasing current density (data from [<a href="#B84-materials-03-00943" class="html-bibr">84</a>]).</p> Full article ">Figure 10
<p>Corresponding cross-sections of the images <a href="#materials-03-00943-f003" class="html-fig">Figure 3</a>a–e [<a href="#B83-materials-03-00943" class="html-bibr">83</a>]. The pore-diameter decreases from ~95 nm to ~25 nm. Images a, c, d, e show cross sectional views in the mid of the porous layer. In image (b) a region near the pore tips is shown.</p> Full article ">Figure 11
<p>(a) SEM-image of the entire porous layer of 35 µm, (b) shows the pore-tip region in detail exhibiting a deviation of the pore-length of about 20 nm.</p> Full article ">Figure 12
<p>Left: Transition region between three porous silicon layers of different porosities, etched with three changing current densities (j<sub>1</sub> = 75 mA/cm<sup>2</sup>, j<sub>2</sub> = 50 mA/cm<sup>2</sup>, j<sub>3</sub> = 125 mA/cm<sup>2</sup>) . In the right micrograph the zoomed-in boundary between the two layers etched with j<sub>2</sub> and j<sub>3</sub> which is quite sharp, is shown. The uncertainty concerning the roughness of the transition lies far below 100 nm.</p> Full article ">Figure 13
<p>Scheme of a electrolytic double-tank cell to fabricate double-sided porous silicon samples. During the anodization process which is performed under pulsed conditions each side is contacted by the electrolyte. A typically used frequency is 0.1 Hz.</p> Full article ">Figure 14
<p>Cross-sectional and corresponding plan view of the surfaces (inset) of the two porous layers.</p> Full article ">Figure 15
<p>Ultrathin wafer with an entire thickness of 40 µm etched on both sides. The two layers exhibit a thickness of about 7 µm each. On the right side the corresponding top view images show that the morphology is alike for both sides.</p> Full article ">Figure 16
<p>SEM micrographs of cross sectional regions of metal filled macroporous silicon. (a) Pt deposition within p-type macroporous silicon forming particles within the pores. As supporting electrolyte Na<sub>2</sub>SO<sub>4</sub>is used. (b) Pt deposition into the pores in using NaCl as supporting electrolyte resulting in metal-rods. (Reproduced by permission of The Electrochemical Society [<a href="#B101-materials-03-00943" class="html-bibr">101</a>].)</p> Full article ">Figure 17
<p>Scanning electron micrographs showing (a) the Cu-deposition within p-type macroporous silicon forming rods and (b) the deposition of Ni which covers the pore-walls. The image is taken from reference [<a href="#B105-materials-03-00943" class="html-bibr">105</a>].</p> Full article ">Figure 18
<p>(a) Scanning electron micrograph using the back scattered electrons showing Ni-nanowires with an elongation of about 2.5 µm (current density = 40 mA/cm<sup>2</sup>, pulse duration = 5 s). (b) Ni-nanostructures deposited into a porous silicon matrix with a length of about 200 nm (current density = 40 mA/cm<sup>2</sup>, pulse duration = 20 s). (c) Back scattered electron (BSE)-image of the cross-section of an entire porous layer filled with Ni particles. The filling factor was estimated to be about 25%. Inset: Example of a zoomed area of sample 3c. A series of such images has been used to estimate the average distance of the Ni-particles to a few hundred nanometers. [<a href="#B114-materials-03-00943" class="html-bibr">114</a>]</p> Full article ">Figure 19
<p>Scanning electron micrographs (BSE) showing the different arrangements of the deposited Ni-precipitations within the channels of the PS-matrices [<a href="#B94-materials-03-00943" class="html-bibr">94</a>]. First row: the spatial distribution of the deposited metals varies between 2/3 to 1/3 of the porous layer. Second row: the porous layers are filled between surface and bottom of the pores but the shape of the precipitated Ni-structures differs. Third row: zoomed areas of row two.</p> Full article ">Figure 20
<p>Relation between pulse duration of the applied current and elongation of the precipitated Ni-structures. The deposition time is in all cases 15 min and the applied current density was 25 mA/cm<sup>2</sup>. The length of the particles increases from sphere-like particles of about 60 nm up to wires of 2.5 µm. The diameter of the metal structures corresponds to the pore-diameter, which is in average 60 nm (data from [<a href="#B84-materials-03-00943" class="html-bibr">84</a>]).</p> Full article ">Figure 21
<p>Left: Relation between current density and depth of the metal deposition in consideration of the pulse duration which has also to be adjusted [<a href="#B84-materials-03-00943" class="html-bibr">84</a>]. Right: Micrographs gained from back scattered electrons showing the Ni-distribution within the porous silicon layers (accumulated near the surface, distribution of dispersed nanostructures over the entire porous layer, homogeneously distributed, accumulated near the pore-tips).</p> Full article ">Figure 22
<p>(a) Cross-sectional scanning electron micrographs obtained from the back scattered electrons of Ni-nanowires deposited within the channels of the PS matrix. The elongation of the wires exhibits about 1.5 µm and the average diameter is according to the mean pore-diameter of 55 nm [<a href="#B84-materials-03-00943" class="html-bibr">84</a>]. (b) Precipitated Co-particles within the PS-template. The particle sizes are distributed between spheres of about 60 nm and ellipsoids with a maximum length of 150 nm [<a href="#B84-materials-03-00943" class="html-bibr">84</a>]. (c) NiCo-nanostructures within the pores exhibiting a maximum length of 500 nm. The variation of the length of the precipitations lies between 200 nm and 500 nm [<a href="#B84-materials-03-00943" class="html-bibr">84</a>].</p> Full article ">Figure 23
<p>SEM-image, gained from back scattered electrons, of double-sided porous silicon with Ni deposited into the pores on one side and Co on the other side. The remaining bulk silicon between the layers is about 450 µm, the porous layers are around 30 µm each.</p> Full article ">Figure 24
<p>SEM-image of an enhanced region of the cross section (<a href="#materials-03-00943-f023" class="html-fig">Figure 23</a>) and the corresponding top view images of the two sides. The morphology of the porous structure is very similar on both sides. The average pore-diameters are around 55 nm [<a href="#B45-materials-03-00943" class="html-bibr">45</a>].</p> Full article ">Figure 25
<p>Ultrathin wafer with a thickness of 60 µm etched on both sides and filled with Ni on one side and Co on the other one. The thickness of the porous layer of side one is about 13 µm and of side two about 22 µm.</p> Full article ">Figure 26
<p>Hystereses loops of a PS-matrix filled with a large amount of Ni-wires (length of a few microns). The anisotropy between easy axis (magnetic field perpendicular to the surface) and hard axis magnetization (magnetic field parallel to the surface) is mainly caused by the shape of the deposited structures (diameter ~60 nm, aspect ratio ~80) [<a href="#B120-materials-03-00943" class="html-bibr">120</a>].</p> Full article ">Figure 27
<p>Magnetization curves of a Co-filled porous silicon sample. Co is precipitated in spherical and ellipsoidal particles reaching a maximum length of 200 nm (diameter ~60 nm). The low anisotropy between the two magnetization directions can be ascribed to the small aspect ratio of the deposits but show also that the particles within one individual pore do not strongly interact among each other [<a href="#B120-materials-03-00943" class="html-bibr">120</a>].</p> Full article ">Figure 28
<p>Magnetization measurements of elongated NiCo-structures (~500 nm) within PS exhibit a magnetic anisotropy of about 50% between easy axis and hard axis direction (diameter ~60 nm) [<a href="#B120-materials-03-00943" class="html-bibr">120</a>].</p> Full article ">Figure 29
<p>Magnetization measurements performed on a double-sided etched porous silicon sample whereas the two porous layers are filled with Ni on one side and Co on the other one. The two metals offer a distinct saturation magnetization and thus the hysteresis loop shows two different slopes.</p> Full article ">Figure 30
<p>Temperature dependence of the coerciviy of two samples exhibiting the same pore-diameter and interpore spacing of the matrix (∅ ~60 nm, interpore spacing ~100 nm). One contains a large amount of embedded Ni-wires, the other one mainly Ni-particles. The measurements are performed in both directions of magnetization, with the external field applied perpendicular and parallel to the surface, respectively.</p> Full article ">Figure 31
<p>Squareness (M<sub>R</sub>/M<sub>S</sub>) depending on the temperature between 4.2 K and 250 K. For the easy axis magnetization the value decreases from 41% at 4.2 K to 32% at 250 K, whereas for the hard axis magnetization the value drops from 19% at 4.2 K to 10% at 250 K [<a href="#B120-materials-03-00943" class="html-bibr">120</a>].</p> Full article ">Figure 32
<p>ZFC/FC measurements carried out on a NiCo-filled porous silicon template exhibiting a blocking temperature T<sub>B</sub> of 180 K. The size of deposits varies between 200 nm and 500 nm [<a href="#B120-materials-03-00943" class="html-bibr">120</a>].</p> Full article ">Figure 33
<p>For comparison to <a href="#materials-03-00943-f032" class="html-fig">Figure 32</a> ZFC/FC measurements of a PS-sample with a large amount of densely packed Ni particle deposition is investigated. The shallow increase of the ZFC-branch without the presence of a distinct peak indicates strong coupling between the Ni-structures [<a href="#B120-materials-03-00943" class="html-bibr">120</a>].</p> Full article ">Figure 34
<p>MFM-measurements performed in tapping mode (left) and magnetic mode (right) respectively showing the abrupt change between silicon and porous silicon and also the sharp difference between non-magnetic and magnetic material [<a href="#B122-materials-03-00943" class="html-bibr">122</a>].</p> Full article ">Figure 35
<p>HRTEM-image of porous silicon, showing a native oxide layer of about 5 nm covering the pore-wall.</p> Full article ">Figure 36
<p>From left: TEM-image of a Ni-filled porous silicon membrane. Ni-particles can be seen inside the pores. Middle: zero-loss image of an enhanced region showing the Ni-structures within the PS-matrix. Right: HRTEM-image showing an individual Ni-particle inside a pore and the surrounding PS-skeleton.</p> Full article ">Figure 37
<p>EELS (electron energy loss spectroscopy) spectrum gained from a line scan across an individual Ni-particle (<a href="#materials-03-00943-f036" class="html-fig">Figure 36</a>, right) within a pore shows the Ni and also oxygen. The high oxygen peak at the edge results from a mixture of SiO<sub>2</sub> covering the pore wall and NiO [<a href="#B123-materials-03-00943" class="html-bibr">123</a>].</p> Full article ">Figure 38
<p>HRTEM-image showing small Ni-particles with a size between 2 nm and 5 nm covering the walls of the porous silicon skeleton. Right: enhanced region of the left image showing these small spherical Ni particles in detail.</p> Full article ">Figure 39
<p>(a) TEM-image of the quite monodisperse magnetite nanoparticles, (b) enhanced region. (c) particle size distribution giving an average diameter of 7.7 nm which is gained from the element (Fe) distribution of the sample due to better contrast (reproduced by permission of The Electrochemical Society [<a href="#B131-materials-03-00943" class="html-bibr">131</a>]).</p> Full article ">Figure 40
<p>ZFC/FC measurements carried out at an applied magnetic field of 5 Oe and in a temperature range between 4.2 K and 360 K. The high blocking temperature (maximum peak of the ZFC-branch) at 135 K indicates dipolar coupling between the particles. Inset: Shift of T<sub>B</sub> towards lower temperatures with increasing applied magnetic field (reproduced by permission of The Electrochemical Society [<a href="#B131-materials-03-00943" class="html-bibr">131</a>]).</p> Full article ">Figure 41
<p>Temperature dependent magnetization measurements of Fe<sub>3</sub>O<sub>4</sub>-nanoparticles exhibiting a blocking temperature at 160 K and a bifurcation of the two branches (ZFC/FC) at 230 K (reproduced by permission of The Electrochemical Society [<a href="#B131-materials-03-00943" class="html-bibr">131</a>]).</p> Full article ">Figure 42
<p>Magnetization measurements of a magnetite solution covered silicon wafer performed with the magnetic field applied perpendicular to the surface (full line) and parallel to the surface (dotted line), respectively. The obtained anisotropy is alike to the one of a magnetic film affirming that the Fe<sub>3</sub>O<sub>4</sub>-particles which form a thin layer interact dipolarly (reproduced by permission of The Electrochemical Society [<a href="#B131-materials-03-00943" class="html-bibr">131</a>]).</p> Full article ">Figure 43
<p>Hystereses loops of a PS-matrix impregnated with a magnetite-solution. The measurements have been carried out for easy axis and hard axis magnetization, perpendicular (full line) and parallel (dotted line) to the sample surface. The small anisotropy is mainly caused by the morphology of the used PS-template leading to predetermined stronger coupling of particles situated along one pore (reproduced by permission of The Electrochemical Society [<a href="#B131-materials-03-00943" class="html-bibr">131</a>]).</p> Full article ">
1249 KiB  
Review
Cement and Concrete Nanoscience and Nanotechnology
by Laila Raki, James Beaudoin, Rouhollah Alizadeh, Jon Makar and Taijiro Sato
Materials 2010, 3(2), 918-942; https://doi.org/10.3390/ma3020918 - 3 Feb 2010
Cited by 402 | Viewed by 35395
Abstract
Concrete science is a multidisciplinary area of research where nanotechnology potentially offers the opportunity to enhance the understanding of concrete behavior, to engineer its properties and to lower production and ecological cost of construction materials. Recent work at the National Research Council Canada [...] Read more.
Concrete science is a multidisciplinary area of research where nanotechnology potentially offers the opportunity to enhance the understanding of concrete behavior, to engineer its properties and to lower production and ecological cost of construction materials. Recent work at the National Research Council Canada in the area of concrete materials research has shown the potential of improving concrete properties by modifying the structure of cement hydrates, addition of nanoparticles and nanotubes and controlling the delivery of admixtures. This article will focus on a review of these innovative achievements. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
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<p>Simplified physical model for hydrated Portland cement.</p> Full article ">Figure 2
<p>The schematic molecular structure of a single sheet of tobermorite. Circles: calcium atoms located at the center of Ca-O octahedra; Triangles show silicate tetrahedra ; OH<sup>-</sup> attachments are not shown. Various tobermorite systems exist that vary in the interlayer distance, <span class="html-italic">i.e.</span>, 9, 11 and 14 Å tobermorites.</p> Full article ">Figure 3
<p>Schematic of polymer-modified C-S-H nanostructure. a: the nanostructure of pristine C-S-H. b: The nanostructure of modified C-S-H after the interaction with polymer molecules.</p> Full article ">Figure 4
<p>Schematic of polymer groups grafted at T silicon sites [<a href="#B28-materials-03-00918" class="html-bibr">28</a>].</p> Full article ">Figure 5
<p>Schematic representation comparing the crystal structure of brucite (A) and LDH (B).</p> Full article ">Figure 6
<p>Summary of different paths to modified and pillared LDH derivatives.</p> Full article ">Figure 7
<p>Slump loss with time for selected cement pastes.</p> Full article ">Figure 8
<p>Hardness measurements on cement compacts made at different water/cement ratios with (NT) and without (control) 2% SWNT additions [<a href="#B69-materials-03-00918" class="html-bibr">69</a>]. “sp” indicates that the sample was prepared with a napthalene sulphonate superplasticizer.</p> Full article ">Figure 9
<p>Example of crack bridging in a SWCNT/hydrated OPC composite bridging structures are SWCNT bundles.</p> Full article ">Figure 10
<p>SWCNT bundles on a hydrated OPC surface after pullout.</p> Full article ">Figure 11
<p>Growth of C-S-H around SWCNT bundles (rods in image) at 135 minutes of hydration of an OPC composite sample.</p> Full article ">Figure 12
<p>Scanning electron microscope image of (a) micro-CaCO<sub>3</sub> and (b) nano-CaCO<sub>3</sub>.</p> Full article ">Figure 13
<p>Rate of heat development measured by the conduction calorimeter.</p> Full article ">Figure 14
<p>Microhardness measurement for the hydration of 1-day and 3-days.</p> Full article ">
529 KiB  
Article
EDTA-Reduction of Water to Molecular Hydrogen Catalyzed by Visible-Light-Response TiO2-Based Materials Sensitized by Dawson- and Keggin-Type Rhenium(V)-Containing Polyoxotungstates
by Chika Nozaki Kato, Kazunobu Hara, Masao Kato, Hidekuni Amano, Konomi Sato, Yusuke Kataoka and Wasuke Mori
Materials 2010, 3(2), 897-917; https://doi.org/10.3390/ma3020897 - 2 Feb 2010
Cited by 6 | Viewed by 15149
Abstract
The synthesis and characterization of a Keggin-type mono-rhenium(V)-substituted polyoxotungstate are described. The dimethylammonium salt [Me2NH2]4[PW11ReVO40] was obtained as analytically pure homogeneous black-purple crystals by reacting mono-lacunary Keggin polyoxotungstate with [ReIV [...] Read more.
The synthesis and characterization of a Keggin-type mono-rhenium(V)-substituted polyoxotungstate are described. The dimethylammonium salt [Me2NH2]4[PW11ReVO40] was obtained as analytically pure homogeneous black-purple crystals by reacting mono-lacunary Keggin polyoxotungstate with [ReIVCl6]2- in water, followed by crystallization from acetone at ca. 5 °C. Single-crystal X-ray structural analysis of [PW11ReVO40]4- revealed a monomeric structure with overall Td symmetry. Characterization of [Me2NH2]4[PW11ReVO40] was also accomplished by elemental analysis, magnetic susceptibility, TG/DTA, FTIR, UV-vis, diffuse reflectance (DR) UV-vis, and solution 31P-NMR spectroscopy. Furthermore, [PW11ReVO40]4- and the Dawson-type dirhenium(V)-oxido-bridged polyoxotungstate [O{ReV(OH)(α2-P2W17O61)}2]14- were supported onto anatase TiO2 surface by the precipitation methods using CsCl and Pt(NH3)4Cl2. With these materials, hydrogen evolution from water in the presence of EDTA⋅2Na (ethylenediamine tetraacetic acid disodium salt) under visible light irradiation (≥400 nm) was achieved. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Polyhedral representation of (a) [O{Re<sup>V</sup>(OH)(α<sub>2</sub>-P<sub>2</sub>W<sub>17</sub>O<sub>61</sub>)}<sub>2</sub>]<sup>14-</sup> (<b>1</b>) and (b) [PW<sub>11</sub>Re<sup>V</sup>O<sub>40</sub>]<sup>4-</sup> (<b>2</b>). The one and two rhenium groups are represented by the purple octahedra. The WO<sub>6</sub> and internal PO<sub>4</sub> groups are represented by white octahedra and yellow tetrahedra, respectively.</p> Full article ">Figure 2
<p>FTIR spectrum (as KBr disks) of <b>Me<sub>2</sub>NH<sub>2</sub>-2</b>.</p> Full article ">Figure 3
<p><sup>31</sup>P-NMR spectra in DMSO-<span class="html-italic">d</span><sub>6</sub> of <b>Me<sub>2</sub>NH<sub>2</sub>-2</b>. The resonance at 0.0 ppm is due to the external reference: 85% H<sub>3</sub>PO<sub>4</sub>.</p> Full article ">Figure 4
<p>(a) UV-vis spectrum in DMSO of <b>Me<sub>2</sub>NH<sub>2</sub>-2</b> at 200–800 nm (1.0 × 10<sup>-6</sup> M). Inset: 400–800 nm (1.0 × 10<sup>-4</sup> M). (b) Diffuse reflectance UV-vis spectrum of <b>Me<sub>2</sub>NH<sub>2</sub>-2</b> at 400–800 nm.</p> Full article ">Figure 5
<p>Time course for H<sub>2</sub> evolution catalyzed by (a) <b>1</b>-Cs-TiO<sub>2</sub>(2.0) and (b) <b>1</b>-Cs-TiO<sub>2</sub>(3.3) under light irradiation (≥400 nm). The first and second runs are represented by circles (○) and squares (□), respectively. Reaction conditions: see <a href="#materials-03-00897-t001" class="html-table">Table 1</a>.</p> Full article ">Figure 6
<p>Time course for H<sub>2</sub> evolution catalyzed by (a) <b>1</b>-Pt-TiO<sub>2</sub>(1.6), (b) <b>1</b>-Pt-TiO<sub>2</sub>(3.9), and (c) <b>1</b>-Pt-TiO<sub>2</sub>(5.6) under light irradiation (≥400 nm). The first and second runs are represented by circles (○) and squares (□), respectively. Reaction conditions: see <a href="#materials-03-00897-t001" class="html-table">Table 1</a>.</p> Full article ">Figure 7
<p>Time course for H<sub>2</sub> evolution catalyzed by (a) <b>2</b>-Cs-TiO<sub>2</sub>(0.37) and (b) <b>2</b>-Cs-TiO<sub>2</sub>(2.3) under light irradiation (≥400 nm). The first and second runs are represented by circles (○) and squares (□), respectively. Reaction conditions: see <a href="#materials-03-00897-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 8
<p>Time course for H<sub>2</sub> evolution catalyzed by (a) <b>2</b>-Pt-TiO<sub>2</sub>(0.059) and (b) <b>2</b>-Pt-TiO<sub>2</sub>(0.19) under light irradiation (≥400 nm). The first and second runs are represented by circles (○) and squares (□), respectively. Reaction conditions: see <a href="#materials-03-00897-t002" class="html-table">Table 2</a>.</p> Full article ">
731 KiB  
Review
Performance of Zirconia for Dental Healthcare
by Nelson R.F.A. Silva, Irena Sailer, Yu Zhang, Paulo G. Coelho, Petra C. Guess, Anja Zembic and Ralf J. Kohal
Materials 2010, 3(2), 863-896; https://doi.org/10.3390/ma3020863 - 1 Feb 2010
Cited by 59 | Viewed by 20034
Abstract
The positive results of the performance of zirconia for orthopedics devices have led the dental community to explore possible esthetical and mechanical outcomes using this material. However, questions regarding long-term results have opened strong and controversial discussions regarding the utilization of zirconia as [...] Read more.
The positive results of the performance of zirconia for orthopedics devices have led the dental community to explore possible esthetical and mechanical outcomes using this material. However, questions regarding long-term results have opened strong and controversial discussions regarding the utilization of zirconia as a substitute for alloys for restorations and implants. This narrative review presents the current knowledge on zirconia utilized for dental restorations, oral implant components, and zirconia oral implants, and also addresses laboratory tests and developments, clinical performance, and possible future trends of this material for dental healthcare. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
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<p>This sequence of images shows a molar crown restoration fabricated from a presintered zirconia (3Y-TZP) core (LAVA, 3M-ESPE). The pre-sintered 3Y-TZP block was machined (a) producing an enlarged zirconia framework core (b). Compare the core size related to scanned dowel (black asterisk). The pre-sintered milled block is then fully sintered obtaining the final 3Y-TZP core or framework for further porcelain veneer application. (c) shows the sintering shrinkage amounting to ~25% of the enlarged core as a compensation for the controlled sintering process. Note the shadow of the porcelain through the sintered core segmented (white arrow). (d) shows a mesial-side view of the final crown properly seated on the dowel (black asterisk).</p> Full article ">Figure 2
<p>Image (a) shows a typical clinical fracture (segmented white arrow) of a zirconia-supported all-ceramic restoration after 3 years of service. Image (b) shows a SEM image of the correspondent fracture in (a). Open black arrow points to the rough surface created by occlusal adjustment, supposedly the fracture initiation site. Image (c) is a light polarized picture of fractured specimen obtained using the sliding contact fatigue testing method. Note the similar fracture pattern (d) that this method creates compared to the clinical fracture presented in (a), showing that this methods mimics the <span class="html-italic">in vivo</span> fracture modes. The SEM of the fractured site of the <span class="html-italic">in vivo</span> tested sample (d) is evidenced by the wear facet created by the indenter (open black arrow), similarly what is seen on the SEM image in (b).</p> Full article ">Figure 3
<p>The schematic shows (a) posterior tooth contact in a chewing cycle as an eccentric contact of the mandibular buccal cusps with the inner inclines of the maxillary buccal cusps, followed by a sliding movement through centric occlusion, and then lifting off; (b) represents the sliding movement as a straight-line motion of a spherical indenter on the surface of a flat brittle layer (crown) supported by a complaint substrate (tooth dentin) with an inclination angle <span class="html-italic">θ</span> = 30°.</p> Full article ">Figure 4
<p><a href="#materials-03-00863-f004" class="html-fig">Figure 4</a> shows light polarized images of (a) a maximum fatigue load of 350 N. A partial cone crack has already propagated ~0.3 mm deep from the occlusal surface after the first loading cycle (black curvy line on the porcelain). (b) shows partial cones formed after 5 cycles. Black solid triangles point to the partial cone penetrating through the entire veneer porcelain.</p> Full article ">Figure 5
<p>The graph represents a constructed damage map (load-cycles-type of failure) for porcelain/zirconia/composite trilayers subjected to off-axis fatigue loading .Note that for a high biting force (400 N or greater), cone cracks (black triangles) propagate through the entire porcelain veneers at first cycle. However, for a relatively low biting force (100–140 N), it takes several million cycles to propagate the cone cracks from the occlusal surface to the veneer/core interface.</p> Full article ">Figure 6
<p>This sequence of clinical images shows a titanium implant (Straumann, Basel, Switzerland) placed (a) in a left central incisor area (segmented white arrow). (b) illustrates the occlusal view (black solid arrow) and front view (white solid arrow) of a zirconia abutment (Cares Abutment, Straumann, Basel, Switzerland) screw-retained on the implant. (c) and (d) are front and occlusal views respectively of the final restoration cemented on the abutment.</p> Full article ">Figure 7
<p>This figure shows a series of images of a clinical patient case treated with an alumina-toughened zirconia implant being placed in the area of a missing upper right lateral incisor.</p> Full article ">
681 KiB  
Review
Dinitrogen and Related Chemistry of the Lanthanides: A Review of the Reductive Capture of Dinitrogen, As Well As Mono- and Di-aza Containing Ligand Chemistry of Relevance to Known and Postulated Metal Mediated Dinitrogen Derivatives
by Michael G. Gardiner and Damien N. Stringer
Materials 2010, 3(2), 841-862; https://doi.org/10.3390/ma3020841 - 1 Feb 2010
Cited by 27 | Viewed by 16248
Abstract
This paper reviews the current array of complexes of relevance to achieving lanthanide mediated nitrogen fixation. A brief history of nitrogen fixation is described, including a limited discussion of successful transition metal facilitated nitrogen fixation systems. A detailed discussion of the numerous lanthanide-nitrogen [...] Read more.
This paper reviews the current array of complexes of relevance to achieving lanthanide mediated nitrogen fixation. A brief history of nitrogen fixation is described, including a limited discussion of successful transition metal facilitated nitrogen fixation systems. A detailed discussion of the numerous lanthanide-nitrogen species relevant to nitrogen fixation are discussed and are related to the Chatt cycle for nitrogen fixation. Full article
(This article belongs to the Special Issue Organometallic Compounds)
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Graphical abstract
Full article ">Figure 1
<p>Model of the FeMo cofactor of nitrogenase adapted from Smith [<a href="#B4-materials-03-00841" class="html-bibr">4</a>]. Ho = homocitrate, His = histamine, Cys = cysteine.</p> Full article ">Figure 2
<p>Molecular structure of side-on bound dinitrogen decamethylsamarocene complex <b>V</b> [<a href="#B34-materials-03-00841" class="html-bibr">34</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms omitted for clarity.</p> Full article ">Figure 3
<p>Strongly reduced (N<sub>2</sub>)<sup>4-</sup> species in [{(<span class="html-italic">c</span>-hex<sub>4</sub>N<sub>4</sub>)<sub>2</sub>Sm<sub>3</sub>Li<sub>2</sub>}(µ<sup>3</sup>-N<sub>2</sub>) {Li(THF)<sub>2</sub>}<sup>.</sup>THF], (<b>VI</b>) [<a href="#B40-materials-03-00841" class="html-bibr">40</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity. Also shown is a partial schematic of the binding observed for (N<sub>2</sub>)<sup>4-</sup> fragment.</p> Full article ">Figure 4
<p>Reduced dinitrogen Gd complex, [{(THF)Gd(N(SiMe<sub>3</sub>)<sub>2</sub>)<sub>2</sub>}<sub>2</sub>N<sub>2</sub>], (<b>IX</b>) [<a href="#B44-materials-03-00841" class="html-bibr">44</a>]. Disorder in one TMS group is not shown. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms omitted for clarity.</p> Full article ">Figure 5
<p>Molecular structure of [{(C<sub>5</sub>Me<sub>5</sub>)Sm}<sub>2</sub>(μ-η<sup>1</sup>:η<sup>1</sup>-N<sub>2</sub>Ph<sub>2</sub>)], (<b>X</b>). Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity [<a href="#B48-materials-03-00841" class="html-bibr">48</a>].</p> Full article ">Figure 6
<p>Representation of the structure of [{C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Sm}<sub>2</sub>{(PhN)CO}<sub>2</sub>], (<b>XII</b>) [<a href="#B42-materials-03-00841" class="html-bibr">42</a>].</p> Full article ">Figure 7
<p>Molecular structure of [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Sm(η<sup>2</sup>-N<sub>2</sub>Ph<sub>2</sub>)(THF)], (<b>XV</b>). Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms and one of the two independent molecules in the asymmetric unit are omitted for clarity [<a href="#B49-materials-03-00841" class="html-bibr">49</a>].</p> Full article ">Figure 8
<p>Molecular structure of [Sm{HB-(3,5-Me<sub>2</sub>pz)<sub>3</sub>}<sub>2</sub>(PhNNPh)], (<b>XIX</b>) [<a href="#B50-materials-03-00841" class="html-bibr">50</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity.</p> Full article ">Figure 9
<p>Molecular structure of [Sm(OAr)<sub>2</sub>(PhNNPh)], (<b>XXI</b>) [<a href="#B51-materials-03-00841" class="html-bibr">51</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms and one diethyl ether molecule of crystallisation are omitted for clarity.</p> Full article ">Figure 10
<p>Molecular structure of [(C<sub>5</sub>Me<sub>5</sub>)Sm{(η<sup>6</sup>:η<sup>1</sup>-Ph)<sub>2</sub>BPh<sub>2</sub>}(PhNNPh)], (<b>XXIII</b>) [<a href="#B52-materials-03-00841" class="html-bibr">52</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity.</p> Full article ">Figure 11
<p>Molecular structure of [(PC<sub>4</sub>-2,5-<span class="html-italic">t</span>-Bu-3,4-Me)<sub>2</sub>Tm(PhNNPh)], (<b>XXIV</b>) [<a href="#B53-materials-03-00841" class="html-bibr">53</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity.</p> Full article ">Figure 12
<p>Molecular structure of [{(C<sub>5</sub>Me<sub>5</sub>)Sm(THF)}<sub>2</sub>(µ-η<sup>2</sup>:η<sup>2</sup>-N<sub>2</sub>Ph<sub>2</sub>)<sub>2</sub>], (<b>XIV</b>) [<a href="#B49-materials-03-00841" class="html-bibr">49</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity.</p> Full article ">Figure 13
<p>Molecular structure of [{Ho(PhNNPh)(TePh)(C<sub>6</sub>H<sub>5</sub>N)}<sub>2</sub>], (<b>XXVI</b>) [<a href="#B55-materials-03-00841" class="html-bibr">55</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms, two pyridine molecules of crystallisation and one of the two independent molecules in the asymmetric unit are omitted for clarity.</p> Full article ">Figure 14
<p>Molecular structure of [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Sm(N(H)Ph)(THF)], (<b>XXXVI</b>) [<a href="#B35-materials-03-00841" class="html-bibr">35</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are omitted for clarity.</p> Full article ">Figure 15
<p>Molecular structure of [(C<sub>5</sub>Me<sub>5</sub>)<sub>2</sub>Sm{η<sup>2</sup>-PhNHNPh}(THF)], (<b>XXXVII</b>) [<a href="#B35-materials-03-00841" class="html-bibr">35</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. Non-hydrazine H atoms are omitted for clarity.</p> Full article ">Figure 16
<p>Erbium imide cluster <b>XLI</b> [<a href="#B61-materials-03-00841" class="html-bibr">61</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. Non-nitrogen H atoms are omitted for clarity.</p> Full article ">Figure 17
<p>AlMe<sub>3</sub> retained, nitrogen bridged samarium imide complex <b>XLIV</b>. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms omitted for clarity [<a href="#B65-materials-03-00841" class="html-bibr">65</a>].</p> Full article ">Figure 18
<p>Ytterbium imide complex <b>XLVII</b> resulting from deprotonation by <span class="html-italic">n</span>-BuLi [<a href="#B66-materials-03-00841" class="html-bibr">66</a>]. Figure generated from CCDC obtained coordinates. Atoms of arbitrary size. H atoms are excluded for clarity. Amido H atoms were inferred but were not located.</p> Full article ">Figure 19
<p>Chatt cycle for dinitrogen fixation at a single metal centre adapted from MacKay [<a href="#B23-materials-03-00841" class="html-bibr">23</a>].</p> Full article ">Figure 20
<p>Schrock catalytic cycle for the Mo HIPT system adapted from Yandulov [<a href="#B25-materials-03-00841" class="html-bibr">25</a>].</p> Full article ">Figure 21
<p>Mechanism for N<sub>2</sub> cleavage by the MoN(R)Ar system [<a href="#B29-materials-03-00841" class="html-bibr">29</a>,<a href="#B30-materials-03-00841" class="html-bibr">30</a>].</p> Full article ">Figure 22
<p>THF mediated transformation of [{(C<sub>5</sub>Me<sub>5</sub>)Sm}<sub>2</sub>(μ-η<sup>1</sup>:η<sup>1</sup>-N<sub>2</sub>Ph<sub>2</sub>)], (<b>X</b>) to [{(C<sub>5</sub>Me<sub>5</sub>)Sm(THF)}<sub>2</sub>{µ-η<sup>2</sup>: η<sup>2</sup>-N<sub>2</sub>Ph<sub>2</sub>}<sub>2</sub>], (<b>XIV</b>) [<a href="#B49-materials-03-00841" class="html-bibr">49</a>].</p> Full article ">Figure 23
<p>Reactivity of hydrazine with samarium pentamethylcyclopentadienyl complexes.</p> Full article ">
5055 KiB  
Article
Probing the Texture of the Calamitic Liquid Crystalline Dimer of 4-(4-Pentenyloxy)benzoic Acid
by Maher A. Qaddoura and Kevin D. Belfield
Materials 2010, 3(2), 827-840; https://doi.org/10.3390/ma3020827 - 29 Jan 2010
Cited by 12 | Viewed by 13825
Abstract
The liquid crystalline dimer of 4-(4-pentenyloxy)benzoic acid, a member of the n-alkoxybenzoic acid homologous series, was synthesized using potassium carbonate supported on alumina as catalyst. The acid dimer complex exhibited three mesophases; identified as nematic, smectic X1 and smectic X2. Phase transition [...] Read more.
The liquid crystalline dimer of 4-(4-pentenyloxy)benzoic acid, a member of the n-alkoxybenzoic acid homologous series, was synthesized using potassium carbonate supported on alumina as catalyst. The acid dimer complex exhibited three mesophases; identified as nematic, smectic X1 and smectic X2. Phase transition temperatures and the corresponding enthalpies were recorded using differential scanning calorimetry upon both heating and cooling. The mesophases were identified by detailed texture observations by variable temperature polarized light microscopy. The nematic phase was distinguished by a fluid Schlieren texture and defect points (four and two brushes) while the smectic phases were distinguished by rigid marble and mosaic textures, respectively. Full article
(This article belongs to the Special Issue Liquid Crystals)
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Figure 1

Figure 1
<p>Thermogravemetric analysis of monomer <b>2</b>.</p> Full article ">Figure 2
<p>DSC thermograms for 4-(4-pentenyloxy) benzoic acid (<b>2</b>).</p> Full article ">Figure 3
<p>The proposed dimeric structure of 4-(4-pentenyloxy) benzoic acid; the spectrum indicates the presence of the carboxylic acid dimer; the carbonyl group in the proposed dimer structure has a characteristic band at 1680 cm<sup>-1</sup>.</p> Full article ">Figure 4
<p>Liquid crystalline transitions for the compound <b>2</b> as observed under light polarized microscopy, crossed polarizer, magnification ×150.</p> Full article ">Figure 5
<p>Phase transitions of the monomer upon cooling, cross polarizer, magnification ×150. (5a) Nematic droplets appearing from the isotropic phase with conoscopic crosses; (5b) nematic droplets continue growing at the clearing point with conoscopic crosses, 150 °C; (5c) nematic droplets are growing with increasing in size and show an optically positive uniaxial behavior, 150 °C; (5d) nematic droplets starts to coalesce with clear conoscopic crosses, 150 °C; (5e) coalescence of the crystalline germs,150 °C; (5f) coalescence of germs in the nematic phase and appearing of points singularities (four-fold brush), 150 °C; (5g) fourfolds brush defects start to appear, 150 °C; (5h) coalescence in progress, points of defect increase; 150 °C; (5i) nematic Schlieren texture grows from coalesced droplets, 150 °C; (5j) nematic Schlieren texture with four and two brushes, 150 °C; (5k) nematic Schlieren texture with air bubble, below 150 °C; (5l) nematic Schleiren texture with four and two brushes upon cooling, below 150 °C. In <a href="#materials-03-00827-f005" class="html-fig">Figure 5</a>k, a Schlieren texture with air bubble can be observed.</p> Full article ">Figure 6
<p>Transition from nematic to smectic to crystalline. (6a) Point singularities as evidence of nematic Schlieren texture, 150 °C; (6b) transition from nematic to smectic X2 upon cooling, 117 °C; (6c), (6d) smectic X2 phase, 117 °C; (6e), (5f) fast transition from smectic X2 to smectic X1. Mosaic texture of smectic X1, 103 °C; (6g) smectic X1 to crystalline phase transition upon cooling, 89 °C; (6h) crystalline phase; below 89 °C.</p> Full article ">Figure 7
<p>Phase transitions upon heating and cooling when external shear stress is applied under cross polarizer. (7a), (7b), and (7c), Nematic texture with: disclination lines (threads), points with extinction crosses, and wall defects, below 150 °C; (7d), nematic to isotropic transition, 150 °C; (7e) nematic droplets coalesce upon cooling, 150 °C; (7f) nematic Shlieren texture and points with extinction crosses, 145 °C; (7g) smectic X2 texture upon cooling, 117 °C; (7h) smectic X2 to smectic X1 transition upon cooling, 103 °C; (7i), (7j) smectic X2 to smectic X1 transition upon cooling, 103 °C; (7k), (7l) mosaic texture of smectic X1, 103 °C.</p> Full article ">Figure 8
<p>The mosaic texture is a common appearance of the smectic B phase as reported in the literature [<a href="#B40-materials-03-00827" class="html-bibr">40</a>]. The mosaic textures are usually characterized by area of uniform optical appearance mediated by grain boundaries. The texture is very consistent with our observations in <a href="#materials-03-00827-f006" class="html-fig">Figure 6</a>e and <a href="#materials-03-00827-f007" class="html-fig">Figure 7</a>k.</p> Full article ">Figure 9
<p>Monomer synthesis, 4-(4 -pentenyloxy)benzoic acid).</p> Full article ">
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