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Coatings
Volume 14
Issue 4
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Coatings, Volume 14, Issue 4 (April 2024) – 145 articles

Cover Story (view full-size image): Hard alloy end mills are commonly used in dentistry to mill zirconia prostheses. Nano-diamond (ND) coating improves wear resistance, enhancing the performance and durability of milling tools. This study aims to assess the effects of ND-coated milling bits on the glossiness and roughness of unsintered and sintered zirconia surfaces at different spindle speeds when milling zirconia green blanks. Sintered zirconia blocks had higher glossiness than unsintered blocks. The ND-coated milling bit resulted in higher glossiness for sintered zirconia at all speeds, whereas the uncoated milling bit can only achieve the same glossiness at 1500 rpm. Sintering significantly reduces roughness in zirconia. Overall, the ND-coated milling bit can achieve higher glossiness on sintered zirconia at various speeds, while the uncoated bit only achieves the same glossiness at a specific speed. View this paper
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17 pages, 6151 KiB  
Article
Ternary Holey Carbon Nanohorn/Potassium Chloride/Polyvinylpyrrolidone Nanohybrid as Sensing Film for Resistive Humidity Sensor
by Bogdan-Catalin Serban, Octavian Buiu, Marius Bumbac, Nicolae Dumbravescu, Cristina Pachiu, Mihai Brezeanu, Gabriel Craciun, Cristina Mihaela Nicolescu, Vlad Diaconescu and Cornel Cobianu
Coatings 2024, 14(4), 517; https://doi.org/10.3390/coatings14040517 - 22 Apr 2024
Viewed by 1278
Abstract
The study presents findings on the relative humidity (R.H.) sensing capabilities of a resistive sensor. This sensor utilizes sensing layers composed of a ternary nanohybrid, consisting of holey carbon nanohorn (CNHox), potassium chloride (KCl), and polyvinylpyrrolidone (PVP), with mass ratios of 7/1/2, 6.5/1.5/2, [...] Read more.
The study presents findings on the relative humidity (R.H.) sensing capabilities of a resistive sensor. This sensor utilizes sensing layers composed of a ternary nanohybrid, consisting of holey carbon nanohorn (CNHox), potassium chloride (KCl), and polyvinylpyrrolidone (PVP), with mass ratios of 7/1/2, 6.5/1.5/2, and 6/2/2 (w/w/w). The sensing structure comprises a silicon substrate, a SiO2 layer, and interdigitated transducer (IDT) electrodes. The sensing film is deposited on the sensing structure via the drop-casting method. The sensing layers’ morphology and composition are investigated through Scanning Electron Microscopy (SEM) and RAMAN spectroscopy. The resistance of thin-film sensors based on ternary hybrids increased with exposure to a range of relative humidity (R.H.) levels, from 0% to 100%. The newly designed devices demonstrated a comparable response at room temperature to that of commercial capacitive R.H. sensors, boasting excellent linearity, swift response times, and heightened sensitivity. Notably, the studied sensors outperform others employing CNHox-based sensing layers in terms of sensitivity, as observed through manufacturing and testing processes. It elucidates the sensing mechanisms of each constituent within the ternary hybrid nanocomposites, delving into their chemical and physical properties, electronic characteristics, and affinity for water molecules. Various alternative sensing mechanisms are considered and discussed, including the reduction in holes within CNHox upon interaction with water molecules, proton conduction, and PVP swelling. Full article
(This article belongs to the Special Issue Advanced Thin Films Technologies for Optics, Electronics, and Sensing)
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Figure 1

Figure 1
<p>The structure of (<b>a</b>) holey CNHox and (<b>b</b>) PVP.</p> Full article ">Figure 2
<p>The layout of the IDE sensing structure.</p> Full article ">Figure 3
<p>Experimental setup employed for R.H. measurements.</p> Full article ">Figure 4
<p>SEM of the K1’ sensing layer at (<b>a</b>) ×300,000 magnification and (<b>b</b>) ×150,000 magnification, the K2’ sensing layer at (<b>c</b>) ×300,000 magnification and (<b>d</b>) ×160,000 magnification, and the K3’ sensing layer at (<b>e</b>) ×300,000 magnification and (<b>f</b>) ×160,000 magnification.</p> Full article ">Figure 4 Cont.
<p>SEM of the K1’ sensing layer at (<b>a</b>) ×300,000 magnification and (<b>b</b>) ×150,000 magnification, the K2’ sensing layer at (<b>c</b>) ×300,000 magnification and (<b>d</b>) ×160,000 magnification, and the K3’ sensing layer at (<b>e</b>) ×300,000 magnification and (<b>f</b>) ×160,000 magnification.</p> Full article ">Figure 5
<p>Raman spectra of ternary nanocomposite CNHox/KCl/PVP. (<b>a</b>) K1, (<b>b</b>) K2; (<b>c</b>) is K3; (<b>d</b>) three acquisition points of K3.</p> Full article ">Figure 5 Cont.
<p>Raman spectra of ternary nanocomposite CNHox/KCl/PVP. (<b>a</b>) K1, (<b>b</b>) K2; (<b>c</b>) is K3; (<b>d</b>) three acquisition points of K3.</p> Full article ">Figure 6
<p>Resistance versus R.H. for the (<b>a</b>) K1, (<b>b</b>) K2, and (<b>c</b>) K3 sensors in several operating sequences.</p> Full article ">Figure 6 Cont.
<p>Resistance versus R.H. for the (<b>a</b>) K1, (<b>b</b>) K2, and (<b>c</b>) K3 sensors in several operating sequences.</p> Full article ">Figure 7
<p>The transfer function of the sensor: (<b>a</b>) K1—1st cycle, (<b>b</b>) K1—2nd to 6th cycles, (<b>c</b>) K2—1st cycle, (<b>d</b>) K2—2nd to 6th cycles, (<b>e</b>) K3—1st cycle, and (<b>f</b>) K3—2nd to 6th cycles in humid nitrogen (R.H. = 0%–100%).</p> Full article ">Figure 8
<p>Sensitivity calculated for each humidity jump for sensors: (<b>a</b>) K1, (<b>b</b>) K2, and (<b>c</b>) K3 in humid nitrogen (R.H. = 0%–90%).</p> Full article ">Figure 9
<p>Example of calculating the response time.</p> Full article ">Figure 10
<p>Graphical representations of the ratios between the response time of investigated sensors and the response time of C.O.M. calculated for each humidity jump: (<b>a</b>) K1, (<b>b</b>) K2, and (<b>c</b>) K3 in humid nitrogen (R.H. = 0%–100%).</p> Full article ">
14 pages, 7256 KiB  
Article
Study on the Wettability and Abrasion Resistance of Ultrafast-Laser-Textured Ti Surface
by Yuankun Hou, Weiling Guo, Pengyuan Sun, Yanfang Zhang, Tong Ding, Zhiguo Xing and Sefei Yang
Coatings 2024, 14(4), 516; https://doi.org/10.3390/coatings14040516 - 22 Apr 2024
Cited by 1 | Viewed by 968
Abstract
Titanium (Ti) materials are highly valued in the medical field for their outstanding biocompatibility and corrosion resistance. However, challenges such as suboptimal wettability and wear resistance can impact the tribological properties of titanium implants, potentially leading to implant failure. This study explores the [...] Read more.
Titanium (Ti) materials are highly valued in the medical field for their outstanding biocompatibility and corrosion resistance. However, challenges such as suboptimal wettability and wear resistance can impact the tribological properties of titanium implants, potentially leading to implant failure. This study explores the application of ultrafast pulsed laser processing to create two distinct structures, circular pits and grooves, on the surface of titanium materials. The samples underwent low-surface-energy treatment, after which the wettability and wear resistance of the textured surfaces were evaluated. The findings indicate that the textured surfaces exhibit improved hydrophobic properties and reduced surface wear. Specifically, the textured surfaces demonstrated a remarkable 73.68% reduction in wear compared to the untextured surfaces. These results underscore the potential of etching textured structures onto titanium surfaces to enhance their wear resistance, thereby offering promising implications for the improvement of titanium implant performance. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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<p>Laser-etched titanium plate samples.</p> Full article ">Figure 2
<p>Micro- and nanomorphology of (<b>a</b>) K1, (<b>b</b>) K2, (<b>c</b>) K3.</p> Full article ">Figure 3
<p>Micro- and nanomorphology of (<b>a</b>) C1, (<b>b</b>) C2, (<b>c</b>) C3.</p> Full article ">Figure 4
<p>XPS spectrum: (<b>a</b>–<b>c</b>) are C, O, and Ti high-resolution spectra of the circular pit structure; (<b>d</b>–<b>f</b>) are the C, O, and Ti high-resolution spectra of the grooves.</p> Full article ">Figure 5
<p>Contact angle of (<b>a</b>) Ti and (<b>b</b>) Ti after modification.</p> Full article ">Figure 6
<p>Contact angle of (<b>a</b>) K1, (<b>b</b>) K2, (<b>c</b>) K3, (<b>d</b>) C1, (<b>e</b>) C2, and (<b>f</b>) C3.</p> Full article ">Figure 7
<p>Contact angle of (<b>a</b>) Kt1, (<b>b</b>) Kt2, (<b>c</b>) Kt3, (<b>d</b>) Ct1, (<b>e</b>) Ct2, and (<b>f</b>) Ct3.</p> Full article ">Figure 8
<p>Friction coefficients of textured surfaces with different densities: (<b>a</b>) circular pit structure, (<b>b</b>) groove structure.</p> Full article ">Figure 9
<p>Contour lines of abrasion marks on structures with different weave densities (<b>a</b>). Circular pit structure, (<b>b</b>) groove structure.</p> Full article ">Figure 10
<p>Wear-resistant mechanism of (<b>a</b>) circular pits and (<b>b</b>) grooves.</p> Full article ">
13 pages, 5578 KiB  
Article
Nitrogen-Doped Diamond-like Carbon Buffer Layer Enhances the Mechanical and Tribological Properties of Diamond-like Carbon Films Deposited on Nitrile Rubber Substrate
by Yinqiao Song, Changxin Han, Nini Zhen, Yukai Wang, Yongxiang Leng, Zhiyu Wu, Qiaoyuan Deng and Feng Wen
Coatings 2024, 14(4), 515; https://doi.org/10.3390/coatings14040515 - 21 Apr 2024
Viewed by 1649
Abstract
The poor adhesion between the DLC film and rubber restricts its application of seals. Introducing a suitable interlayer can bolster the adhesion of the coating or film. In this study, nitrogen-doped diamond-like carbon (N-DLC) emerged as the optimal intermediate layer between rubber and [...] Read more.
The poor adhesion between the DLC film and rubber restricts its application of seals. Introducing a suitable interlayer can bolster the adhesion of the coating or film. In this study, nitrogen-doped diamond-like carbon (N-DLC) emerged as the optimal intermediate layer between rubber and DLC. A series of N-DLC/DLC multilayer films were fabricated via DC magnetron sputtering on nitrile rubber (NBR) substrates, varying the substrate bias voltage (0 V, 100 V, 200 V). A scanning electron microscopy analysis revealed that the composite film surface was smoother than the DLC film alone. The results of Raman spectroscopy and X-ray photoelectron spectroscopy indicated a robust bond between nitrogen and carbon atoms in the composite film, with nitrogen facilitating the conversion of sp3C-C bonds into sp2C=C. Mechanical tests demonstrated that the N-DLC interlayer improved film adhesion and reduced the CoF of the composite film to 0.2–0.3. Specifically, the CoF of the N-DLC/DLC film prepared at 100 V was as low as 0.20, with a wear amount of 1.13 mg. Consequently, the inclusion of the N-DLC interlayer substantially enhanced the mechanical and tribological properties of DLC-coated NBR, rendering this coating highly advantageous for various applications. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The schematic diagram illustrates the deposition process of the N-DLC intermediate layer and the composite film.</p> Full article ">Figure 2
<p>The surface morphology of DLC films deposited on NBR at different interlayer bias voltages was investigated using scanning electron microscopy (SEM).</p> Full article ">Figure 3
<p>(<b>a</b>) Raman spectra of the DLC/N-DLC multilayer films and DLC films deposited on nitrile rubber under different interlayer bias voltages; (<b>b</b>) I<sub>D</sub>/I<sub>G</sub> ratio of DLC/N-DLC; (<b>c</b>) I<sub>D</sub>/I<sub>G</sub> ratio of DLC.</p> Full article ">Figure 4
<p>Raman mapping of the deposited N-DLC interlayer and N-DLC/DLC multilayer films (the abscissa and ordinate represent the positions of points, 11 × 11); (<b>a</b>) C1, (<b>b</b>) C2, (<b>c</b>) C3, (<b>d</b>) M1, (<b>e</b>) M2, and (<b>f</b>) M3.</p> Full article ">Figure 5
<p>(<b>a</b>,<b>c</b>) XPS C1s spectra of carbon films (composite film and interlayer) deposited on NBR at different interlayer bias voltages; (<b>b</b>,<b>d</b>) corresponding sp<sup>2</sup> and sp<sup>3</sup> percentages.</p> Full article ">Figure 6
<p>(<b>a</b>) Hardness and Young’s modulus; (<b>b</b>) H/E values; (<b>c</b>) H<sup>3</sup>/E<sup>2</sup> values; and (<b>d</b>) adhesion strength of NBR coated with composite film and DLC.</p> Full article ">Figure 7
<p>(<b>a</b>) Coefficient of Friction and (<b>b</b>) wear volume of NBR coated with composite film and DLC.</p> Full article ">Figure 8
<p>(<b>a</b>) Raman spectra of multilayer films with different interlayer bias voltages at the wear marks; (<b>b</b>) ratio of I<sub>D</sub> to I<sub>G</sub> at the corresponding wear mark; (<b>c</b>) morphology of the wear marks; and (<b>d</b>) a scanning electron microscope image of the C2 fracture cross-section.</p> Full article ">
17 pages, 19076 KiB  
Article
In Situ Synthesis of an Epoxy Resin Microwave Absorption Coating with Anti-Ultraviolet Aging Effects
by Shujun Yan, Xin Chen, Angui Zhang and Jun Tang
Coatings 2024, 14(4), 514; https://doi.org/10.3390/coatings14040514 - 20 Apr 2024
Viewed by 1391
Abstract
A nanoparticle-anchored three-dimensional microsphere flower-structured layered double hydroxide (LDH) material with Fe3O4 particles was successfully prepared using simple hydrothermal and hot solvent methods. Micro-nanostructured Fe3O4@LDHs (SLF) composites balance microwave absorption, corrosion protection, and UV aging resistance. [...] Read more.
A nanoparticle-anchored three-dimensional microsphere flower-structured layered double hydroxide (LDH) material with Fe3O4 particles was successfully prepared using simple hydrothermal and hot solvent methods. Micro-nanostructured Fe3O4@LDHs (SLF) composites balance microwave absorption, corrosion protection, and UV aging resistance. The minimum reflection loss value of SLF is −35.75 dB at 14.16 GHz, when the absorber thickness is 8 mm, and the absorption bandwidth at this frequency is up to 2.56 GHz for RL values less than −10 dB, while the LL is only 1 GHz. The SLF /EP coating has not only excellent microwave absorption performance but also excellent corrosion and UV aging resistance performance. The coating still has some anti-corrosion effect after 10 d of immersion. This work is intended as a reference for the development of new coatings with excellent microwave absorption properties as well as corrosion and UV aging resistance for wind turbine tower barrels (seaside wind power generation equipment) surfaces. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials and Coatings: Synthesis, Properties and Applications)
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Figure 1

Figure 1
<p>Schematic synthesis of SLF composites.</p> Full article ">Figure 2
<p>XRD patterns of LL, SL, and SLF samples.</p> Full article ">Figure 3
<p>FT-IR spectra of LL, SL, and SLF sample.</p> Full article ">Figure 4
<p>(<b>a</b>) XPS spectra of SLF sample and (<b>b</b>–<b>f</b>) high-resolution XPS spectra of (<b>b</b>) Mg 1s, (<b>c</b>) Al 2p, (<b>d</b>) C 1s, (<b>e</b>) O 1s, and (<b>f</b>) Fe 2p for the SLF.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>c</b>) SEM images of (<b>a</b>) LL, (<b>b</b>) SL, (<b>c</b>) SLF; (<b>d</b>,<b>e</b>) TEM images of (<b>d</b>) SL and (<b>e</b>) SLF [<a href="#B20-coatings-14-00514" class="html-bibr">20</a>]; and (<b>f</b>–<b>i</b>) the EDX element mappings corresponding to the following (<b>e</b>): (<b>f</b>) Fe, (<b>g</b>) O, (<b>h</b>) Mg, and (<b>i</b>) Al.</p> Full article ">Figure 6
<p>The frequency dependence of (<b>a</b>) ε′, (<b>b</b>) ε″, (<b>c</b>) μ′, and (<b>d</b>) μ″ for LL, SL, and SLF samples. (<b>e</b>) Dielectric loss and (<b>f</b>) magnetic loss tangents of LL, SL, and SLF sample.</p> Full article ">Figure 7
<p>(<b>a</b>,<b>c</b>,<b>e</b>) 3D and (<b>b</b>,<b>d</b>,<b>f</b>) 2D reflection loss of (<b>a</b>,<b>b</b>) LL, (<b>c</b>,<b>d</b>) SL, and (<b>e</b>,<b>f</b>) SLF sample.</p> Full article ">Figure 8
<p>(<b>a</b>) Attenuation constant and (<b>b</b>) impedance-matching characteristics of LL, SL, and SLF sample.</p> Full article ">Figure 9
<p>Schematic representation of MA mechanism of SLF/EP coating.</p> Full article ">Figure 10
<p>(<b>a</b>,<b>c</b>,<b>e</b>,<b>g</b>) Bode and (<b>b</b>,<b>d</b>,<b>f</b>,<b>h</b>) Nyquist diagrams of (<b>a</b>,<b>b</b>) EP, (<b>c</b>,<b>d</b>) LL/EP, (<b>e</b>,<b>f</b>) SL/EP, (<b>g</b>,<b>h</b>) SLF/EP samples at different immersion times in 3.5 wt% NaCl solution.</p> Full article ">Figure 11
<p>Corrosion morphology of (<b>a</b>) EP, (<b>b</b>) LL/EP, (<b>c</b>) SL/EP, and (<b>d</b>) SLF/EP coatings before and after exposure to salt spray test for 240 h.</p> Full article ">Figure 12
<p>Schematic representation of corrosion protection for the steel with (<b>a</b>) SLF/EP coating and (<b>b</b>) EP composite coating.</p> Full article ">Figure 13
<p>(<b>a</b>) UV-Vis spectra of EP, LL/EP, SL/EP, and SLF/EP coatings; (<b>b</b>) FT-IR of EP, LL/EP, SL/EP, and SLF/EP coatings before and after 24 h UV aging.</p> Full article ">Figure 14
<p>Tribological properties of EP, LL/EP, SL/EP, and SLF/EP coatings under a load of 2 N: (<b>a</b>) coefficient of friction and (<b>b</b>) mean friction coefficient.</p> Full article ">
17 pages, 7705 KiB  
Article
Effect of Annealing on Stress, Microstructure, and Interfaces of NiV/B4C Multilayers
by Chenyuan Chang, Zhenbo Wei, Hui Jiang, Hangjian Ni, Wentao Song, Jialian He, Simeng Xiang, Zhanshan Wang, Zhe Zhang and Zhong Zhang
Coatings 2024, 14(4), 513; https://doi.org/10.3390/coatings14040513 - 20 Apr 2024
Cited by 1 | Viewed by 2994
Abstract
The functionality and reliability of nanoscale multilayer devices and components are influenced by changes in stress and microstructure throughout fabrication, processing, and operation. NiV/B4C multilayers with a d-spacing of 3 nm were prepared by magnetron sputtering, and two groups of annealing [...] Read more.
The functionality and reliability of nanoscale multilayer devices and components are influenced by changes in stress and microstructure throughout fabrication, processing, and operation. NiV/B4C multilayers with a d-spacing of 3 nm were prepared by magnetron sputtering, and two groups of annealing experiments were performed. The stress, microstructure, and interface changes in NiV/B4C after annealing were investigated by grazing-incidence X-ray reflectometry (GIXR), grazing-incidence X-ray diffraction (GIXRD), X-ray diffuse scattering, and grazing-incidence small-angle X-ray scattering (GISAXS). The temperature dependence experiments revealed a gradual shift in the multilayer stress from compression to tension during annealing from 70 °C to 340 °C, with the stress approaching near-zero levels between 70 °C and 140 °C. The time-dependent experiments indicated that most of the stress changes occurred within the initial 10 min, which showed that prolonged annealing was unnecessary. Combining the X-ray diffraction and X-ray scattering measurements, it was found that the changes in the thickness, interface roughness, and lateral correlation length, primarily due to crystallization, drove the changes in stress and microstructure. Full article
(This article belongs to the Special Issue Thin-Film Synthesis, Characterization and Properties)
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Figure 1
<p>Annealing temperature control curve of NiV/B<sub>4</sub>C multilayer film for (<b>a</b>) temperature dependence and (<b>b</b>) time dependence analyses.</p> Full article ">Figure 2
<p>Macro view of the NiV/B<sub>4</sub>C multilayer and sample stage.</p> Full article ">Figure 3
<p>Geometry of the GISAXS technique.</p> Full article ">Figure 4
<p>(<b>a</b>) Surface profile of NiV/B<sub>4</sub>C multilayer film before coating; (<b>b</b>) surface profile of NiV/B<sub>4</sub>C multilayer film after coating.</p> Full article ">Figure 5
<p>(<b>a</b>) Temperature-dependent stress curve of NiV/B<sub>4</sub>C multilayers; (<b>b</b>) stress reduction in the multilayers after annealing at 340 °C for different annealing durations.</p> Full article ">Figure 6
<p>GIXR measurement and fitted result of NiV/B<sub>4</sub>C multilayers under different annealing temperatures.</p> Full article ">Figure 7
<p>Relative changes in the (<b>a</b>) period and (<b>b</b>) interface width of the multilayer after annealing at different temperatures for 60 min.</p> Full article ">Figure 8
<p>GIXR measurement and fitted result of NiV/B<sub>4</sub>C multilayers under different annealing time.</p> Full article ">Figure 9
<p>Relative changes in the (<b>a</b>) period and (<b>b</b>) interface width of the multilayers after annealing at 340 °C for different durations.</p> Full article ">Figure 10
<p>Rocking curves around the 1st Bragg peak of the (<b>a</b>) multilayers annealed at 70, 140, 220, 290, and 340 °C for 60 min; (<b>b</b>) comparison of curves before and after annealing; (<b>c</b>) multilayers annealed at 340 °C for 10, 30, 60, and 120 min; (<b>d</b>) comparison of curves before and after annealing (the curves of different color are measurements, black curve is a fitting result).</p> Full article ">Figure 11
<p>Process of interface changes during annealing of the as-deposited multilayer NiV/B<sub>4</sub>C coatings.</p> Full article ">Figure 12
<p>(<b>a</b>) GIXRD patterns of the film annealed at different conditions. (<b>b</b>) Magnified view of the (0 0 1) reflection of V<sub>5</sub>O<sub>9</sub>.</p> Full article ">Figure 13
<p>Grain size of V<sub>5</sub>O<sub>9</sub>(0.01) crystal phase at 2θ = 11.453° after annealing NV/B<sub>4</sub>C multilayers.</p> Full article ">Figure 14
<p>GISAXS maps of NiV/B<sub>4</sub>C multilayers measured at different annealing conditions.</p> Full article ">Figure 15
<p>PSD functions of (<b>a</b>) different annealing temperatures; (<b>b</b>) fitting curves; (<b>c</b>) different annealing durations; and (<b>d</b>) fitting curves.</p> Full article ">Figure 16
<p>The lateral correlation length for IMD and GISAXS at different annealing (<b>a</b>) temperatures; and (<b>b</b>) different annealing durations.</p> Full article ">
18 pages, 6683 KiB  
Article
Preparation of Conductive Asphalt Concrete Based on the Action Mechanism of Conductive Phase Materials
by Xiujun Li, Zhipeng Zhang, Heng Zhang, Huaiyu Ma and Fangzhi Shi
Coatings 2024, 14(4), 512; https://doi.org/10.3390/coatings14040512 - 20 Apr 2024
Viewed by 990
Abstract
Carbon fiber powder (CFP) was first applied to conductive asphalt concrete as a conductive phase material, but its action mechanism has not been clarified. In this paper, atomic force microscopy (AFM) and molecular dynamics (MDs) simulation are used to study the carbon fiber [...] Read more.
Carbon fiber powder (CFP) was first applied to conductive asphalt concrete as a conductive phase material, but its action mechanism has not been clarified. In this paper, atomic force microscopy (AFM) and molecular dynamics (MDs) simulation are used to study the carbon fiber powder mechanism of action, guide the preparation of conductive asphalt concrete, and study the electrothermal properties of conductive asphalt concrete. The results show that carbon fiber powder weakens the adhesion property of asphalt mastic, and this weakening further strengthens in the water–temperature coupling, so water stability and conductivity are used as evaluation indicators to determine that the optimal content of carbon fiber powder is 2.0% and that the optimal content of carbon fibers (CFs) is 0.4%. Carbon fiber–carbon fiber powder conductive asphalt concrete with a resistivity of 0.98 Ω·m was finally prepared. In the temperature rise test of the Marshall specimen and rutting slab, its warming effect is obvious, and the heat transformation rate is more than 75%, so it has a very good ability to melt snow and ice. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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<p>Conductive asphalt concrete two-electrode method.</p> Full article ">Figure 2
<p>Asphalt–water, asphalt–carbon fiber powder, and asphalt–water–carbon fiber powder models: (<b>a</b>) asphalt–water model; (<b>b</b>) asphalt–carbon fiber powder model; (<b>c</b>) asphalt–water–carbon fiber powder model.</p> Full article ">Figure 3
<p>Morphology of carbon fiber powder asphalt mastic before and after water–temperature coupling: (<b>a</b>) plan of carbon fiber powder asphalt mastic; (<b>b</b>) three-dimensional view of carbon fiber powder asphalt mastic; (<b>c</b>) plan of water–temperature coupled carbon fiber powder asphalt mastic; (<b>d</b>) three-dimensional view of water–temperature coupled carbon fiber powder asphalt mastic.</p> Full article ">Figure 3 Cont.
<p>Morphology of carbon fiber powder asphalt mastic before and after water–temperature coupling: (<b>a</b>) plan of carbon fiber powder asphalt mastic; (<b>b</b>) three-dimensional view of carbon fiber powder asphalt mastic; (<b>c</b>) plan of water–temperature coupled carbon fiber powder asphalt mastic; (<b>d</b>) three-dimensional view of water–temperature coupled carbon fiber powder asphalt mastic.</p> Full article ">Figure 4
<p>Micromechanics of carbon fiber powder asphalt mastic before and after water–temperature coupling: (<b>a</b>) adhesion of carbon fiber powder asphalt mastic; (<b>b</b>) adhesion of water–temperature coupled carbon fiber powder asphalt mastic; (<b>c</b>) DMT modulus of carbon fiber powder asphalt mastic; (<b>d</b>) DMT modulus of water–temperature coupled carbon fiber powder asphalt mastic.</p> Full article ">Figure 4 Cont.
<p>Micromechanics of carbon fiber powder asphalt mastic before and after water–temperature coupling: (<b>a</b>) adhesion of carbon fiber powder asphalt mastic; (<b>b</b>) adhesion of water–temperature coupled carbon fiber powder asphalt mastic; (<b>c</b>) DMT modulus of carbon fiber powder asphalt mastic; (<b>d</b>) DMT modulus of water–temperature coupled carbon fiber powder asphalt mastic.</p> Full article ">Figure 5
<p>Two mixing processes for carbon fiber–carbon fiber powder conductive asphalt concrete: (<b>a</b>) Process I; (<b>b</b>) Process II.</p> Full article ">Figure 6
<p>The mixing homogeneity of the two mixing processes: (<b>a</b>) Process I; (<b>b</b>) Process II.</p> Full article ">Figure 7
<p>Relation between resistivity and carbon fiber content.</p> Full article ">Figure 8
<p>Microscopic distribution of 0.4% carbon fibers.</p> Full article ">Figure 9
<p>Relationship curve between carbon fiber powder content and evaluation indexes.</p> Full article ">Figure 10
<p>(<b>a</b>) Relationship between gross bulk density and oil–stone ratio; (<b>b</b>) relationship between air voids (VVs) and oil–stone ratio; (<b>c</b>) relationship between voids in mineral aggregate (VMA) and oil–stone ratio; (<b>d</b>) relationship between asphalt saturation (VFA) and oil–stone ratio; (<b>e</b>) relationship between Marshall stability and oil–stone ratio; (<b>f</b>) relationship between flow value and oil–stone ratio.</p> Full article ">Figure 11
<p>Temperature rise test of Marshall specimens: (<b>a</b>,<b>b</b>).</p> Full article ">Figure 12
<p>Temperature variation in Marshall specimens with time.</p> Full article ">Figure 13
<p>Temperature rise test of rutting slabs.</p> Full article ">Figure 14
<p>Temperature variation in rutting slab with time.</p> Full article ">
17 pages, 7770 KiB  
Article
Using MA-rFTIR Mapping as a Tool to Assess the Efficacy of Cleaning Treatments and to Aid in the Restoration Activities of Paintings
by Lucilla Pronti, Martina Romani, Marcella Ioele, Gloria Tranquilli, Francesca Fumelli, Serena Sechi, Angelica Donati, Elena Cianca, Ilaria Sinceri and Mariangela Cestelli Guidi
Coatings 2024, 14(4), 511; https://doi.org/10.3390/coatings14040511 - 19 Apr 2024
Viewed by 821
Abstract
The removal of non-original superimposed layers covering the original pictorial layer in paintings is a common practice to restore the authentic appearance of surfaces and mitigate potential risks to artwork preservation. Contemporary assessments of the effectiveness of such cleaning treatments often employ non-destructive [...] Read more.
The removal of non-original superimposed layers covering the original pictorial layer in paintings is a common practice to restore the authentic appearance of surfaces and mitigate potential risks to artwork preservation. Contemporary assessments of the effectiveness of such cleaning treatments often employ non-destructive analytical methods. However, many existing techniques face limitations, either lacking specificity in compound identification or analyzing very limited areas (<millimeters) through a point-by-point approach. This study introduces the application of a macro Fourier transform infrared scanner, in reflection mode (MA-rFTIR), as an effective tool for supporting restorers during cleaning processes. This method proved successful in addressing challenges related to the removal of calcium oxalate films and non-original superimposed layers on two ancient paintings. Full article
(This article belongs to the Special Issue Materials Characterization and Surface Analysis for Cultural Heritage)
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<p>(<b>a</b>) Wooden painted cross from the 13th century, (<b>b</b>) Panel painting “Madonna in trono con Bambino, miracolo delle stimmate di San Francesco, Santi Antonio Abate e Bartolomeo, Crocefissione, San Cristoforo” by Arcangelo Di Cola. The areas under investigation are indicated by the highlighted yellow rectangles and they measure approximately 3 × 10 cm<sup>2</sup>.</p> Full article ">Figure 2
<p>Micro-FTIR spectra of the beeswax reference (1) and of superimposed layer (2).</p> Full article ">Figure 3
<p>The analyzed areas using non-invasive approaches; area (<b>A</b>) represents the untreated surface, area (<b>B</b>) signifies the region cleaned with chemical treatments, and area (<b>C</b>) involves the portion subjected to a combination of laser ablation and chemical cleaning. Additionally, specific points denoted as 1a, 1b, and 1c correspond to the locations of point-by-point analyses within these areas. This strategic selection of points allows for a detailed examination of the effects of different cleaning methods on the 13th-century wooden painted cross without resorting to extensive and potentially damaging sampling.</p> Full article ">Figure 4
<p>rFTIR spectra of 1a, 1b, and 1c points. The spectral features assigned to azurite are labeled as “*”.</p> Full article ">Figure 5
<p>Visible image (<b>top</b>) and correlation map of calcium oxalate (<b>bottom</b>). Area (<b>A</b>) represents the untreated surface, area (<b>B</b>) signifies the region cleaned with chemical treatments, and area (<b>C</b>) involves the portion subjected to a combination of laser ablation and chemical cleaning.</p> Full article ">Figure 6
<p>(<b>a</b>) Visible image (<b>top</b>) and correlation map highlighting gypsum (<b>bottom</b>). (<b>b</b>) Visible image (<b>top</b>) and correlation map emphasizing azurite (<b>bottom</b>). Area (<b>A</b>) represents the untreated surface, area (<b>B</b>) signifies the region cleaned with chemical treatments, and area (<b>C</b>) involves the portion subjected to a combination of laser ablation and chemical cleaning.</p> Full article ">Figure 7
<p>(<b>a</b>) The panel painting before the restoration. (<b>b</b>) The panel painting after the restoration. (<b>c</b>) A closer view of the analyzed area is presented before the restoration process. (<b>d</b>) A closer view of the analyzed area is presented after the restoration process.</p> Full article ">Figure 8
<p>Micro-FTIR spectrum of the dark blue layer.</p> Full article ">Figure 9
<p>r-FTIR spectrum of the dark blue layer.</p> Full article ">Figure 10
<p>r-FTIR spectra of the original layer (point 2) and the dark blue layer (point 1) acquired after the cleaning processes.</p> Full article ">Figure 11
<p>(<b>a</b>) Spectra of the repainted and original layer along with their first derivative spectra. (<b>b</b>) Visible image and the correlation map of the carbonyl group (ROI: 1790–1700 cm<sup>−1</sup>) before the cleaning processes. (<b>c</b>) Visible image and the correlation map of the carbonyl group (ROI: 1790–1700 cm<sup>−1</sup>) after the cleaning processes.</p> Full article ">Figure 12
<p>(<b>a</b>) Visible image and the correlation map of the calcium oxalate (ROI: 1400–1200 cm<span class="html-italic"><sup>−</sup></span><sup>1</sup>) before the cleaning processes. (<b>b</b>) Visible image and the correlation map of the calcium oxalate (ROI: 1400–1200 cm<span class="html-italic"><sup>−</sup></span><sup>1</sup>) after the cleaning processes. (<b>c</b>) Visible image and the correlation map of lapis lazuli (ROI: 2290–2370 cm<span class="html-italic"><sup>−</sup></span><sup>1</sup>) before the cleaning processes. (<b>d</b>) Visible image and the correlation map of lapis lazuli (ROI: 2290–2370 cm<span class="html-italic"><sup>−</sup></span><sup>1</sup>) after the cleaning processes.</p> Full article ">
15 pages, 3605 KiB  
Article
Exploring Na Doping in ZnO Thin Films: Electrical and Optical Insights
by Ana Luiza C. Silva, Luis M. B. Vargas, Marcelos L. Peres, Marcio D. Teodoro and Marcio P. F. de Godoy
Coatings 2024, 14(4), 510; https://doi.org/10.3390/coatings14040510 - 19 Apr 2024
Cited by 1 | Viewed by 1579
Abstract
Strategies to achieve p-type behavior in semiconductor oxides are an important current topic of research. Our study showed that sodium-doped zinc oxide thin films are a plausible approach. The insertion of dopant allowed a transition between n-type p-type electrical behavior in specific temperature [...] Read more.
Strategies to achieve p-type behavior in semiconductor oxides are an important current topic of research. Our study showed that sodium-doped zinc oxide thin films are a plausible approach. The insertion of dopant allowed a transition between n-type p-type electrical behavior in specific temperature ranges around 300 K. Annealing procedures under controlled atmospheres, including Ar, N2, and O2, increased the hole density up to a magnitude of 1016 cm−3, although this also reduced the window temperature. The micro-photoluminescence spectra showed an enhancement of defect-related emissions as the dopant content increased. Notably, yellow-green emissions (around 2.38 eV–520 nm) were the most prominent in the as-grown samples. After annealing, a strong redshift of the defect band was observed (around 1.85 eV–670 nm). Our findings showed that p-type ZnO:Na films exhibited emissions associated with RGB primary colors. In a chromaticity diagram, as-grown samples appeared near the white range, annealed films were close to the warm white area, and O2 annealed films trended within the red range. Full article
(This article belongs to the Special Issue Optical Thin Films and Coatings: Synthesis, Characterisation and Applications)
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<p>Spray pyrolysis configuration used for the growth of ZnO and ZnO:Na films. The SEM images indicate the uniformity of the films at a 100 μm scale.</p> Full article ">Figure 2
<p>(<b>a</b>) Diffractograms of the ZnO, as-grown ZnO:Na, and ZN10 annealed samples. ICSD 060435 and JCPDS 36-1451 are crystallographic standards for sodium and zinc oxides, respectively. XPS survey scans of as-grown ZnO (<b>b</b>) and ZN10 (<b>d</b>) with Na 1s high-resolution spectra for ZnO (<b>c</b>) and ZN10 (<b>e</b>).</p> Full article ">Figure 3
<p>Carrier density of as-grown ZnO (<b>a</b>) and sodium-doped ZnO (<b>b</b>–<b>e</b>) films ZN2, ZN4, ZN6, and ZN10, respectively. Open dots represent n-type conductivity (gray area), while filled dots indicate p-type conductivity. Additionally, (<b>f</b>) shows the bar chart with the crystallite size of the samples.</p> Full article ">Figure 4
<p>Carrier density of the ZN10 annealed in (<b>a</b>) Ar and (<b>b</b>) N<sub>2</sub> and O<sub>2</sub> atmospheres. The gray area indicates that the conductivity is n-type (empty dots). The filled dots indicate that the conductivity is p-type. (<b>c</b>) Crystallite size of ZN10-Ar, ZN10-N<sub>2</sub>, and ZN10-O<sub>2</sub> films.</p> Full article ">Figure 5
<p>Characteristic curves of electrical resistance versus temperature of as-grown samples of (<b>a</b>) ZnO, (<b>b</b>) ZN2, (<b>c</b>) ZN4, (<b>d</b>) ZN6, and (<b>e</b>) ZN10. ZN10 films annealed in an atmosphere of (<b>f</b>) Ar, (<b>g</b>) N<sub>2</sub>, and (<b>h</b>) O<sub>2</sub>. The solid red line indicates the fitting curves.</p> Full article ">Figure 6
<p>The temperature dependence of μPL spectra of undoped ZnO film (<b>a</b>) and Na-doped ZnO films: (<b>b</b>) ZN2, (<b>c</b>) ZN4, (<b>d</b>) ZN6, and (<b>e</b>) ZN10. The ratios between the integrated intensity of defect bands 1, 2, and 3 and the NBE (I<sub>Def</sub>/I<sub>NBE</sub>) at 10K (<b>f</b>) and 300 K (<b>g</b>) are also displayed.</p> Full article ">Figure 7
<p>Integrated μPL intensity as a function of 1/<span class="html-italic">k<sub>B</sub>T</span> for the bands associated with the defects (band 1, band 2, and band 3) and the band related to the emission of energy in the UV range of the ZnO film (<b>a</b>) and the sodium-doped samples: (<b>b</b>) ZN2, (<b>c</b>) ZN4, (<b>d</b>) ZN6, and (<b>e</b>) ZN10. The solid red line indicates the fitting curves.</p> Full article ">Figure 8
<p>μPL spectra of as-grown and annealed ZN10 film in Ar, N<sub>2</sub>, and O<sub>2</sub> atmospheres at (<b>a</b>) 10 K and (<b>b</b>) 300 K. Additionally, the ratio between the integrated intensity of defect bands 1, 2, and 3 and the NBE (I<sub>Def</sub>/I<sub>NBE</sub>) at 10K (<b>c</b>) and 300 K (<b>d</b>) is also shown – Band 4 is associated with the NBE.</p> Full article ">Figure 9
<p>Integrated intensity of μPL versus 1/<span class="html-italic">k<sub>B</sub>T</span> for the bands associated with the defects (band 1 and band 2) and the band related to the emissions in the UV energy region of the ZN10 annealed in (<b>a</b>) argon (ZN10-Ar); (<b>b</b>) nitrogen (ZN10-N<sub>2</sub>) and (<b>c</b>) oxygen (ZN10-O<sub>2</sub>). The solid red line indicates the fitting curves.</p> Full article ">Figure 10
<p>(<b>a</b>) Sketch of energy band diagram elucidating electrical and optical processes. (<b>b</b>) Room temperature PL emissions of samples depicted in the CIE 1931 diagram exhibited a white pattern. The annealing caused a redshift of emissions due to the increase in defects.</p> Full article ">
12 pages, 5797 KiB  
Article
Coating Red Phosphor on Green Luminescent Material for Multi-Mode Luminescence and Advanced Anti-Counterfeit Applications
by Jiale Liu, Bo Chen and Qi Zhu
Coatings 2024, 14(4), 509; https://doi.org/10.3390/coatings14040509 - 19 Apr 2024
Viewed by 1263
Abstract
Traditional fluorescent anti-counterfeiting materials usually exhibit fixed-wavelength excitation patterns and monochromatic luminescence, which are extremely easy to be counterfeited and have low security. Therefore, there is an urgent need to develop multi-mode fluorescent materials with enhanced security to address this issue. Here, SrAl [...] Read more.
Traditional fluorescent anti-counterfeiting materials usually exhibit fixed-wavelength excitation patterns and monochromatic luminescence, which are extremely easy to be counterfeited and have low security. Therefore, there is an urgent need to develop multi-mode fluorescent materials with enhanced security to address this issue. Here, SrAl2O4:1%Eu,2%Dy@Y2O3:Eu3+ core-shell structured phosphors were prepared via a sol-gel method. Coating SrAl2O4:Eu,Dy with Y2O3:Eu3+ red phosphor did not significantly change the crystal structure of SrAl2O4. Under UV excitation at 254 nm, SrAl2O4:1%Eu,2%Dy@Y2O3:Eu3+ exhibited red emission at 613 nm (5D0→7F2 transition of Eu3+), and a strong green afterglow was observed after removing the UV irradiation. However, blue-green emission at 496 nm was observed under UV excitation at 365 nm, followed by green afterglow upon removal of the light source. Varying the content of the Y2O3:Eu3+ shell yielded different emissions and afterglows. The prepared samples are sensitive to the excitation wavelength and duration and have multimodal luminescence properties, which can be used for anti-counterfeiting patterns. The outcomes in this work indicate that the phosphor is a promising fluorescent material for anti-counterfeiting. Full article
(This article belongs to the Special Issue Optical Coatings: From Materials to Applications)
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<p>X-ray diffraction patterns of SrAl<sub>2</sub>O<sub>4</sub>:Eu,Dy@Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+</sup> synthesized with different concentrations of PVA: (<b>a</b>) 1%, (<b>b</b>) 3%, (<b>c</b>) 5%, (<b>d</b>) 7%. ☆ representative positions of the Y<sub>2</sub>O<sub>3</sub> peaks.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) TEM, and (<b>c</b>) HR-TEM images of SrAl<sub>2</sub>O<sub>4</sub>:Eu,Dy@Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+</sup>. (<b>d</b>) Schematic diagram of the core-shell structure of SrAl<sub>2</sub>O<sub>4</sub>:Eu,Dy@Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+.</sup></p> Full article ">Figure 3
<p>(<b>a</b>–<b>d</b>) PLE/PL spectra and (<b>e</b>) CIE coordinates of SrAl<sub>2</sub>O<sub>4</sub>:Eu,Dy@Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+</sup> synthesized with different concentrations of PVA.</p> Full article ">Figure 4
<p>Persistent luminescence decay curves for SrAl<sub>2</sub>O<sub>4</sub>:Eu,Dy@Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+</sup> synthesized with different concentrations of PVA after 254 nm UV light illumination for 15 min. The instrument parameters were kept the same for all the materials.</p> Full article ">Figure 5
<p>Demonstration of the multi-mode anti-counterfeiting SrAl<sub>2</sub>O<sub>4</sub>:Eu,Dy@Y<sub>2</sub>O<sub>3</sub>:Eu<sup>3+</sup> samples irradiated at (<b>a</b>) 254 nm and (<b>b</b>) 365 nm.</p> Full article ">Figure 6
<p>Photographs of the logo “1923” under (<b>a</b>) 254 nm and (<b>b</b>) 365 nm radiation from a box UV lamp and afterglow after the removal of radiation (after 254 nm UV light illumination for 1 min).</p> Full article ">
25 pages, 36685 KiB  
Article
Laser Cleaning Combined with Cladding Improves Cladding Quality for Repairing Steel Plates in Pressure Vessels
by Kaijun Fan, Yongjun Shi, Youfan Xu, Shuyao Wang, Qin Wang, Ying Li, Cheng Zhang and Zhaojian Li
Coatings 2024, 14(4), 508; https://doi.org/10.3390/coatings14040508 - 19 Apr 2024
Viewed by 1388
Abstract
Good-quality metallurgical bonding and a high degree of automation are critical for using laser cladding technology in on-site repairs. At present, most of the on-site repairs are carried out manually, which can bring about problems such as complicated operation procedures, uneven repair quality, [...] Read more.
Good-quality metallurgical bonding and a high degree of automation are critical for using laser cladding technology in on-site repairs. At present, most of the on-site repairs are carried out manually, which can bring about problems such as complicated operation procedures, uneven repair quality, and personnel injuries. In this study, a surface repair method that combined laser cleaning with cladding (LCC) was proposed. First, the plates were scanned with a high-frequency pulsed laser to remove the surface impurity layer. The surface was then coated with Inconel 625 powder while irradiated with a continuous laser for the cladding. Both the macro-morphology and microstructure of the surface were examined, and mechanical property tests were also conducted. The metallographic and scanning electron microscope images indicated that, compared to the manual polishing and laser cladding process, the LCC specimens had a better metallurgical bonding quality and a thicker clad layer. The average hardness of the clad layer on the LCC specimens was high at 256.47 HV, 36.2% higher than that of the Q345R substrate. Compared to the Q345R specimens of the same size, the LCC specimens showed an increased impact on the energy absorption, yield strength, and tensile strength. This study provides a new approach for improving the automation and cladding quality of on-site repairs. Full article
(This article belongs to the Special Issue Laser Surface Engineering: Technologies and Applications)
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<p>A large cyclone separator in a natural gas station.</p> Full article ">Figure 2
<p>The rusted Q345R plate surface: (<b>a</b>) surface; (<b>b</b>) cross section; (<b>c</b>) 3D morphology; and (<b>d</b>) microscopic morphology.</p> Full article ">Figure 3
<p>Manufacturing of specimens: (<b>a</b>) dimensions; (<b>b</b>) cutting directions; and (<b>c</b>) tensile, impact, and metallography specimens.</p> Full article ">Figure 4
<p>Laser cleaning and cladding platform.</p> Full article ">Figure 5
<p>Principle of laser working: (<b>a</b>) laser cleaning; and (<b>b</b>) laser cladding.</p> Full article ">Figure 6
<p>Temperature data acquisition system.</p> Full article ">Figure 7
<p>Comparison of process parameters between LCC and MPLC.</p> Full article ">Figure 8
<p>Macro-morphology of samples (<b>a</b>–<b>y</b>) 1–25, respectively, under different laser process parameters.</p> Full article ">Figure 9
<p>Three-dimensional morphology of sample (<b>a</b>) 1, (<b>b</b>) 2, (<b>c</b>) 4, (<b>d</b>) 7, (<b>e</b>) 12, (<b>f</b>) 14, (<b>g</b>) 19, (<b>h</b>) 21, and (<b>i</b>) 22.</p> Full article ">Figure 10
<p>Responses of three factors to oxygen content.</p> Full article ">Figure 11
<p>Responses of three factors to surface roughness.</p> Full article ">Figure 12
<p>Comparison of surface morphology between laser cleaning and manual polishing: (<b>a</b>) microscopic morphology of laser cleaning; (<b>b</b>) 3D morphology of laser cleaning; (<b>c</b>) microscopic morphology of manual polishing; and (<b>d</b>) 3D morphology of manual polishing.</p> Full article ">Figure 13
<p>Cross-sectional microstructures: (<b>a</b>,<b>b</b>) 50× metallographic images; and (<b>c</b>,<b>d</b>) 100× metallographic images.</p> Full article ">Figure 14
<p>SEM micrographs of specimens: (<b>a</b>–<b>e</b>) cross sections along the Y-direction; and (<b>f</b>,<b>g</b>) cross sections along the X-direction.</p> Full article ">Figure 15
<p>Temperature curve of the substrate: (<b>a</b>) during laser cleaning process; and (<b>b</b>) during manual polishing process.</p> Full article ">Figure 16
<p>Microstructure of the HAZ: (<b>a</b>–<b>e</b>) LCC specimens; and (<b>f</b>,<b>g</b>) MPLC specimens.</p> Full article ">Figure 17
<p>Microhardness test: (<b>a</b>) two test paths; and (<b>b</b>) microhardness distribution for each specimen.</p> Full article ">Figure 18
<p>Results of the impact test.</p> Full article ">Figure 19
<p>Macro-morphology and SEM micro-morphology of impact fracture specimens: (<b>a</b>–<b>c</b>) LCC-X; (<b>d</b>–<b>f</b>) MPLC-X; (<b>g</b>–<b>i</b>) LCC-Y; (<b>j</b>–<b>l</b>) MPLC-Y; and (<b>m</b>–<b>o</b>) substrate.</p> Full article ">Figure 20
<p>Results of the tensile test: (<b>a</b>) stress–strain curves; and (<b>b</b>) tensile strength and elongation of different specimens.</p> Full article ">Figure 21
<p>Macro-morphology and SEM micro-morphology of tensile fracture specimens: (<b>a</b>–<b>c</b>) LCC-X; (<b>d</b>–<b>f</b>) MPLC-X; (<b>g</b>–<b>i</b>) LCC-Y; (<b>j</b>–<b>l</b>) MPLC-Y; and (<b>m</b>–<b>o</b>) substrate.</p> Full article ">Figure 22
<p>Comparison of the process flows of MPLC and LCC.</p> Full article ">Figure A1
<p>Comparison of metallographic structure before and after cutting.</p> Full article ">
20 pages, 4191 KiB  
Article
Enhancing Thermal Insulation of Geothermal Well Cement Using Alkali-Activated Straw Ash and Natural Zeolite
by Ying Ji, Qianqian Sha, Gang Zhu, Yuze Xue and Tinghui Zhang
Coatings 2024, 14(4), 507; https://doi.org/10.3390/coatings14040507 - 19 Apr 2024
Viewed by 1077
Abstract
To improve the heat extraction efficiency from the wellbore fluids to the stratum in the geothermal well, thermal insulation cement, which is prepared by alkali-excited straw ash-natural zeolite, was based on the orthogonal test. The properties of thermal insulation cement, such as compressive [...] Read more.
To improve the heat extraction efficiency from the wellbore fluids to the stratum in the geothermal well, thermal insulation cement, which is prepared by alkali-excited straw ash-natural zeolite, was based on the orthogonal test. The properties of thermal insulation cement, such as compressive strength, thermal conductivity and fluidity, were tested, and the comprehensive evaluation and range analysis of thermal insulation cement were carried out by using analytic hierarchy process (AHP) as a macro reference index. The results show that the alkali equivalent of natural zeolite and water glass are the two biggest factors affecting the properties of cement. The compressive strength of the optimal mixture at 38 °C and 60 °C for 8 h is 9.26 MPa and 24.46 MPa, respectively, and the thermal conductivity reduction rates at 30 °C, 60 °C and 90 °C are 42.41%, 50.29% and 54.03%, respectively. The initial consistency of the optimal mixture is 13.9 BC and the consistency time is 123 min, which can be used for engineering cementing. In addition, the thickening time of cement can be adjusted according to water-reducing agent and retarder to meet the actual construction requirements of cementing. Full article
(This article belongs to the Special Issue Recent Progress in Reinforced Concrete and Building Materials)
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<p>Trend diagram of influence of each factor level on compressive strength of cement paste cured at 38 °C for 8 h.</p> Full article ">Figure 2
<p>Trend diagram of influence of each factor level on compressive strength of cement paste cured at 60 °C for 8 h.</p> Full article ">Figure 3
<p>Trend diagram of influence of each factor level on compressive strength of cement paste cured at 38 °C for 28 d.</p> Full article ">Figure 4
<p>Trend diagram of influence of each factor level on compressive strength of cement paste cured at 60 °C for 28 d.</p> Full article ">Figure 5
<p>Trend diagram of influence of each factor level on thermal conductivity of cement paste tested at 30 °C.</p> Full article ">Figure 6
<p>Trend diagram of influence of each factor level on thermal conductivity of cement paste tested at 60 °C.</p> Full article ">Figure 7
<p>Trend diagram of influence of each factor level on thermal conductivity of cement paste tested at 90 °C.</p> Full article ">Figure 8
<p>Trend diagram of influence of each factor level on fluidity of cement paste.</p> Full article ">Figure 9
<p>Curve of thickening time of A cement sample.</p> Full article ">Figure 10
<p>Curve of thickening time of B cement sample.</p> Full article ">Figure 11
<p>Pore size distribution of Z6 cement sample.</p> Full article ">Figure 12
<p>SEM images of the orthogonal optimal group cured at 38 °C for 8 h and 28 d: (<b>a</b>) C0—8 h; (<b>b</b>) C0—28 d; (<b>c</b>) Z6—8 h; (<b>d</b>) Z6—28 d.</p> Full article ">
15 pages, 8536 KiB  
Article
Excitation-Wavelength- and Time-Dependent Fluorescent Ink Based on RGB Building Blocks for Advanced Anti-Counterfeiting
by Chengxin Lin, Chenxi Kang, Xinxin He, Jiaci Yi and Qi Zhu
Coatings 2024, 14(4), 506; https://doi.org/10.3390/coatings14040506 - 19 Apr 2024
Cited by 1 | Viewed by 1173
Abstract
What is reported here is an advanced anti-counterfeiting ink whose luminous effect changes over time and at different excitation wavelengths. Unlike traditional anti-counterfeit fluorescent materials, the phosphors used here exhibit multicolor emissions under multiple excitation modes. In this work, the most important building [...] Read more.
What is reported here is an advanced anti-counterfeiting ink whose luminous effect changes over time and at different excitation wavelengths. Unlike traditional anti-counterfeit fluorescent materials, the phosphors used here exhibit multicolor emissions under multiple excitation modes. In this work, the most important building blocks are three classic phosphors with primary colors, red (Ca2YNbO6:0.4Eu3+), green (SrAl2O4:0.01Eu2+, 0.02Dy3+) and blue (CaAl2O4:0.012Eu2+, 0.06Nd3+, 0.036Gd3+), which were synthesized using the high-temperature solid-state method. The phosphors formed homogeneous solid solutions and were uniformly distributed throughout the mixture. A homogeneous transparent luminescent ink was obtained by blending the multi-mode phosphors with transparent screen-printing ink, resulting in multi-mode luminescence by simply varying the proportions of the red (R), green (G) and blue (B) phosphors. Thanks to this simple process, an advanced anti-counterfeiting ink with low production costs was achieved. Anti-counterfeiting logos of a “Giraffe” and “Steam Train” were printed using the transparent fluorescent ink onto black cardstock, exhibiting the characteristic of dynamic luminescence dependent on the duration and excitation wavelength. The anti-counterfeiting effect of the patterns suggests that the fluorescent ink is worth developing and is reliable in its application. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology, 2nd Edition)
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<p>XRD patterns of Ca<sub>2</sub>YNbO<sub>6</sub>:0.4Eu<sup>3+</sup> (<b>a</b>), SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (<b>b</b>) and CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (<b>c</b>).</p> Full article ">Figure 2
<p>TEM images, corresponding HR-TEM images, SAED patterns of Ca<sub>2</sub>YNbO<sub>6</sub>:0.4Eu<sup>3+</sup> (<b>a<sub>1</sub></b>–<b>a<sub>3</sub></b>), SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (<b>b<sub>1</sub></b>–<b>b<sub>3</sub></b>) and CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (<b>c<sub>1</sub></b>–<b>c<sub>3</sub></b>).</p> Full article ">Figure 3
<p>SEM micrographs and element mapping images of the tricolor mixed phosphors (R:G:B = 4:2:1).</p> Full article ">Figure 4
<p>PL and PLE spectra of Ca<sub>2</sub>YNbO<sub>6</sub>:0.4Eu<sup>3+</sup> (<b>a<sub>1</sub></b>,<b>a<sub>2</sub></b>), SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (<b>b<sub>1</sub></b>,<b>b<sub>2</sub></b>) and CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (<b>c<sub>1</sub></b>,<b>c<sub>2</sub></b>). Persistent luminescence decay curve of (<b>d</b>) SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (monitored at 514 nm after 254 nm UV light illumination for 5 min) and (<b>e</b>) CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (monitored at 444 nm after 254 nm UV light illumination for 5 min). The corresponding CIE coordinates of Ca<sub>2</sub>YNbO<sub>6</sub>:0.4Eu<sup>3+</sup> (<b>f</b>), SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (<b>g</b>) and CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (<b>h</b>) under their optimal excitation wavelengths.</p> Full article ">Figure 4 Cont.
<p>PL and PLE spectra of Ca<sub>2</sub>YNbO<sub>6</sub>:0.4Eu<sup>3+</sup> (<b>a<sub>1</sub></b>,<b>a<sub>2</sub></b>), SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (<b>b<sub>1</sub></b>,<b>b<sub>2</sub></b>) and CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (<b>c<sub>1</sub></b>,<b>c<sub>2</sub></b>). Persistent luminescence decay curve of (<b>d</b>) SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (monitored at 514 nm after 254 nm UV light illumination for 5 min) and (<b>e</b>) CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (monitored at 444 nm after 254 nm UV light illumination for 5 min). The corresponding CIE coordinates of Ca<sub>2</sub>YNbO<sub>6</sub>:0.4Eu<sup>3+</sup> (<b>f</b>), SrAl<sub>2</sub>O<sub>4</sub>:0.01Eu<sup>2+</sup>, 0.02Dy<sup>3+</sup> (<b>g</b>) and CaAl<sub>2</sub>O<sub>4</sub>:0.012Eu<sup>2+</sup>, 0.06Nd<sup>3+</sup>, 0.036Gd<sup>3+</sup> (<b>h</b>) under their optimal excitation wavelengths.</p> Full article ">Figure 5
<p>PL spectra (<b>a<sub>1</sub></b>,<b>a<sub>2</sub></b>,<b>b<sub>1</sub></b>,<b>b<sub>2</sub></b>,<b>c<sub>1</sub></b>,<b>c<sub>2</sub></b>) of different proportions of mixed phosphors and the corresponding CIE coordinates (<b>d</b>–<b>f</b>) of mixed phosphors under 254 nm and 365 nm excitations. (<b>g<sub>1</sub></b>,<b>g<sub>2</sub></b>) Appearances of the emissions and afterglow signals for mixed phosphors.</p> Full article ">Figure 5 Cont.
<p>PL spectra (<b>a<sub>1</sub></b>,<b>a<sub>2</sub></b>,<b>b<sub>1</sub></b>,<b>b<sub>2</sub></b>,<b>c<sub>1</sub></b>,<b>c<sub>2</sub></b>) of different proportions of mixed phosphors and the corresponding CIE coordinates (<b>d</b>–<b>f</b>) of mixed phosphors under 254 nm and 365 nm excitations. (<b>g<sub>1</sub></b>,<b>g<sub>2</sub></b>) Appearances of the emissions and afterglow signals for mixed phosphors.</p> Full article ">Figure 5 Cont.
<p>PL spectra (<b>a<sub>1</sub></b>,<b>a<sub>2</sub></b>,<b>b<sub>1</sub></b>,<b>b<sub>2</sub></b>,<b>c<sub>1</sub></b>,<b>c<sub>2</sub></b>) of different proportions of mixed phosphors and the corresponding CIE coordinates (<b>d</b>–<b>f</b>) of mixed phosphors under 254 nm and 365 nm excitations. (<b>g<sub>1</sub></b>,<b>g<sub>2</sub></b>) Appearances of the emissions and afterglow signals for mixed phosphors.</p> Full article ">Figure 6
<p>Appearances of the emissions and afterglow signals for transparent luminescent inks.</p> Full article ">Figure 7
<p>Flow chart of the preparation and pattern printing of transparent luminescent inks.</p> Full article ">Figure 8
<p>Appearances of the emission sand afterglow signals for the “Steam Train” pattern printed with monochrome transparent luminescent ink onto commercial paper (<b>a</b>) and the “Giraffe” pattern printed with multi-mode transparent fluorescent ink onto commercial paper (<b>b</b>).</p> Full article ">
13 pages, 10209 KiB  
Article
Plasma Bombardment-Induced Amorphization of (TiNbZrCr)Nx High-Entropy Alloy Nitride Films
by Yantao Li, Donglin Ma, Jun Liang, Deming Huang, Libo Wang, Diqi Ren, Xin Jiang and Yongxiang Leng
Coatings 2024, 14(4), 505; https://doi.org/10.3390/coatings14040505 - 19 Apr 2024
Cited by 2 | Viewed by 1161
Abstract
The (TiNbZrCr)Nx high-entropy nitride films (HENFs) were prepared by high-power pulsed magnetron sputtering (HPPMS). The effect of the N2 flow rate (FN) on the HPPMS plasma discharge, film composition, microstructure, residual stress, tribological properties, and corrosion resistance was investigated. [...] Read more.
The (TiNbZrCr)Nx high-entropy nitride films (HENFs) were prepared by high-power pulsed magnetron sputtering (HPPMS). The effect of the N2 flow rate (FN) on the HPPMS plasma discharge, film composition, microstructure, residual stress, tribological properties, and corrosion resistance was investigated. Results show that, with the increase in FN, plasma discharge is enhanced. Firstly, the introduced N atoms react with Ti, Nb, Cr, and Zr to form an FCC nitride phase structure. Then, with the increase in plasma bombardment on the deposited film, the HENFs undergo amorphization to form an FCC+ amorphous structure, accompanied by a decrease in grain size and a change in the preferred orientation from (1 1 1) to (2 0 0). The HENFs deposited at FN = 8 sccm show the highest hardness of 27.8 GPa. The HENFs deposited at FN = 12 sccm present the best tribological properties, with a low wear rate of 4.0 × 10−6 mm3N−1m−1. The corrosion resistance of the (TiNbZrCr)Nx HENFs shows a strong correlation with the amorphous phase. The corrosion resistance of the FCC nitride film is the worst, and the corrosion resistance gradually increases with the amorphous transformation of the film. Based on the above results, nanocomposite high-entropy films can be prepared using HPPMS technology and exhibit excellent, comprehensive performance. Full article
(This article belongs to the Collection Strong, Ductile and Corrosion-Resistant High-Entropy Alloys)
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<p>(<b>a</b>) The HPPMS discharge voltage and current and (<b>b</b>) the composition of the (TiNbZrCr)N<sub>x</sub> HENFs deposited at different nitrogen flow rates.</p> Full article ">Figure 2
<p>XRD spectra of (TiNbZrCr)N<sub>x</sub> HENFs deposited at different nitrogen flow rates.</p> Full article ">Figure 3
<p>SEM surface and cross-section morphologies of (TiNbZrCr)N<sub>x</sub> HENFs deposited at F<sub>N</sub> = (<b>a</b>) 0 sccm, (<b>b</b>) 4 sccm, (<b>c</b>) 8 sccm, (<b>d</b>) 12 sccm, (<b>e</b>) 16 sccm, (<b>f</b>) the EDS-mapping, and (<b>g</b>) the elemental ratio of (TiNbZrCr)N<sub>x</sub> HENFs deposited at F<sub>N</sub> = 12 sccm.</p> Full article ">Figure 4
<p>TEM images of (TiNbZrCr)N<sub>x</sub> deposited at 12 sccm N<sub>2</sub>: (<b>a</b>) low-magnified images, (<b>b</b>) high-resolution image, and (<b>c</b>) selected area electron diffraction pattern.</p> Full article ">Figure 5
<p>(<b>a</b>) Residual stress, (<b>b</b>) hardness (blue dash line), and Young’s modulus (red dash line) of (TiNbZrCr)N<sub>x</sub> HENFs deposited at different nitrogen flow rates.</p> Full article ">Figure 6
<p>(<b>a</b>) Friction coefficient curves, (<b>b</b>) average friction coefficients, (<b>c</b>) wear track profiles, and (<b>d</b>) wear rates of (TiNbZrCr)N<sub>x</sub> HENFs deposited at different nitrogen flow rates.</p> Full article ">Figure 7
<p>Wear track morphologies and composition distribution of (TiNbZrCr)N<sub>x</sub> HENFs deposited at F<sub>N</sub> = (<b>a</b>) 0 sccm, (<b>b</b>) 4 sccm, (<b>c</b>) 8 sccm, (<b>d</b>) 12 sccm, and (<b>e</b>) 16 sccm.</p> Full article ">Figure 8
<p>(<b>a</b>) Nyquist, (<b>b</b>) and (<b>c</b>) Bode plots from EIS data of 316 SS and (TiNZrCr)N<sub>x</sub> HENFs. (<b>d</b>) Equivalent circuit model of the substrate and HENFs coated substrate.</p> Full article ">Figure 9
<p>Potentiodynamic polarization curves of bare 316 SS and the (TiNbZrCr)N<sub>x</sub> HENFs in 3.5 wt.% NaCl.</p> Full article ">Figure 10
<p>Schematic diagram of chloride ion transport in FCC and amorphous + FCC HENFs.</p> Full article ">
10 pages, 4895 KiB  
Article
Design and Preparation of Bending-Resistant Flexible All-Solid Dye-Sensitized Solar Cells
by Yan Li, Yu-Xuan Hou, Wei-Wu Dang, Li Liu, Jian-Hua Chen and Xian Gu
Coatings 2024, 14(4), 504; https://doi.org/10.3390/coatings14040504 - 18 Apr 2024
Viewed by 1251
Abstract
All-solid-state flexible dye-sensitized solar cells will not only expand the application scenarios of solar cells but also significantly extend the lifetime of solar cells. However, improving their bending-resistant ability is still a great challenge. In this study, a bending-resistant flexible all-solid dye-sensitized solar [...] Read more.
All-solid-state flexible dye-sensitized solar cells will not only expand the application scenarios of solar cells but also significantly extend the lifetime of solar cells. However, improving their bending-resistant ability is still a great challenge. In this study, a bending-resistant flexible all-solid dye-sensitized solar cell was designed and prepared. Firstly, for the preparation of TiO2 photoanode, the traditional nano-sized film has been replaced by dual-porous film with both nano and submicron pores, which can not only benefit the filling of the electrolyte but also supply the space for stress release. Secondly, for the filling of the Poly(vinylidene fluoride)/Poly(ethylene oxide)-based electrolyte, the solvent is removed by a vacuum method, and the electrolyte fibers forming in the submicron pores also show the potential for stress release. Lastly, combined with the advantages of the dual-porous TiO2 film and the fast evaporation of the polymer electrolyte, the conversion efficiency of the solar cells remains constant after the 20,000 bending times. The study supplies a demonstration for the development of all-solid-state flexible dye-sensitized solar cells. Full article
(This article belongs to the Special Issue Advanced Polymer and Thin Film for Sustainable Energy Harvesting)
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<p>The microstructure of the powder and composite film: (<b>a</b>) the pristine P25 powder, (<b>b</b>) the composite cluster after annealing, and (<b>c</b>) the cross-sectional view of the dual-porous film.</p> Full article ">Figure 2
<p>The cross-sectinal view of the dual-porous film after electroplate nickel: (<b>a</b>) distribution and (<b>b</b>) particle size.</p> Full article ">Figure 3
<p>The cross-sectional view of the dual-porous film after being filled with PVDF/PEO-based electrolyte: (<b>a</b>) low magnification and (<b>b</b>) high magnification, and the obvious electrolyte fibers are marked with black arrows.</p> Full article ">Figure 4
<p>The formation process of the electrolyte fiber on dual-porous film: (<b>a</b>) the electrolyte solution fully infiltrates the submicron pore, (<b>b</b>) the PVDF/PEO solute shrank to the TiO<sub>2</sub> film along with the evaporation of the solvent, and (<b>c</b>) the electrolyte undergoes in-situ solidification into a fiber because of the fast evaporation of the solvent. The blue particles represent TiO<sub>2</sub> and the electrolyte filling in the TiO<sub>2</sub> film is represented by yellow.</p> Full article ">Figure 5
<p>The photovoltaic performance of the flexible all-solid-state solar cell under the bending times of 0th, 1000th, 2000th, 5000th, 10,000th, and 20,000th.</p> Full article ">Figure 6
<p>The variation tendency of the photovoltaic parameters for an average of 5 solar cells with increasing bending times: (<b>a</b>) <span class="html-italic">V</span><sub>oc</sub>, (<b>b</b>) <span class="html-italic">J</span><sub>sc</sub>, (<b>c</b>) FF, and (<b>d</b>) <span class="html-italic">η</span>, where <span class="html-italic">V</span><sub>oc</sub> is short for open-circuit voltage; <span class="html-italic">J</span><sub>sc</sub> is short for short-circuit current density; FF is short for fill factor, and <span class="html-italic">η</span> is short for conversion efficiency.</p> Full article ">Figure 7
<p>The typical Nyquist plots of the flexible all-solid-state DSCs under bending times of 0, 2000, and 20,000 at <span class="html-italic">V</span><sub>oc</sub> under illumination. The dots are the pristine data, and the solid lines are the fitting results based on the equivalent circuit model shown in the inset. In the equivalent circuit model, <span class="html-italic">R</span><sub>s</sub> is the series resistance including the sheet resistance of the whole cell; <span class="html-italic">R</span><sub>Pt</sub> and C<sub>Pt</sub> are the charge transfer resistance and electrical double-layer capacitance at the Pt/electrolyte interface; <span class="html-italic">R</span><sub>t</sub> is the transport resistance of the electrons in TiO<sub>2</sub> film, and <span class="html-italic">R</span><sub>ct</sub> is the charge transfer resistance of electrons at the TiO<sub>2</sub>/dye/electrolyte interface; C<sub>μ1</sub> is the chemical capacitance of TiO<sub>2</sub> film; <span class="html-italic">R</span><sub>w</sub> and C<sub>μ2</sub> are the charge diffusion resistance and chemical capacitance of the electrolyte.</p> Full article ">
12 pages, 3515 KiB  
Article
Synthesis of an Epoxy Toughening Curing Agent through Modification of Terephthalic Acid Sludge Waste
by Jinhui Fu, Huixian Kong, Rentong Yu, Jinchun Tu, Qiang Wu, Mingyu Wang, Lina Niu and Kexi Zhang
Coatings 2024, 14(4), 503; https://doi.org/10.3390/coatings14040503 - 18 Apr 2024
Viewed by 1323
Abstract
Purified terephthalic acid (PTA) is widely used as a chemical raw material, with its production process resulting in significant compounds that generate a substantial amount of sludge waste annually. These compounds are known to possess active hydrogen. Utilizing this property, a novel approach [...] Read more.
Purified terephthalic acid (PTA) is widely used as a chemical raw material, with its production process resulting in significant compounds that generate a substantial amount of sludge waste annually. These compounds are known to possess active hydrogen. Utilizing this property, a novel approach for the treatment of PTA sludge waste was developed for its modification and re-use. This study focuses on the preparation of epoxy curing agents using PTA sludge-tank material. The modification of PTA sludge-tank material is achieved by using the one-pot method to investigate the toughening effect of home-made curing agents on epoxy resins and compare them with commercially available curing agents, and to analyze the mechanism of the structure of the curing agent on the material. The results showed that while the tensile strength of the experimental group was generally lower than that of the control group, the impact strength was significantly higher. Additionally, the hardness and tensile strength of the materials gradually decreased with an increase of the amount of hardener, while the elongation at break and impact strength increased. Notably, at a hardener amount of 35%, the elongation at break increased by 3.89%, and the tensile strength and impact strength reached 10.13 MPa and 42.86 kJ m−2, respectively, demonstrating excellent toughness and strength characteristics. These findings testified the feasibility of modifying PTA sludge waste to prepare an epoxy toughening curing agent is not only feasible, but also significantly enhances the material’s toughness. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology, 2nd Edition)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Infrared spectra of PTA sludge waste and purified terephthalic acid (PTA).</p> Full article ">Figure 2
<p>TG curves of PTA and PTA sludge wastes.</p> Full article ">Figure 3
<p>Flow chart of PTA sludge waste modification and curing agent preparation.</p> Full article ">Figure 4
<p>FTIR spectra of (<b>a</b>) PTA sludge waste, (<b>b</b>) esterification, (<b>c</b>) curing agent.</p> Full article ">Figure 5
<p>Homemade curing agent curing epoxy resin process.</p> Full article ">Figure 6
<p>SEM of materials with different curing agent contents. (<b>a</b>) Control group, (<b>b</b>) 20%, (<b>c</b>) 25%, (<b>d</b>) 30%, (<b>e</b>) 35%, (<b>f</b>) 40%.</p> Full article ">Figure 7
<p>Schematic representation of the molecular network of the cured epoxy resin before (<b>a</b>,<b>b</b>) and after impact (<b>c</b>,<b>d</b>), as well as for the control (<b>a</b>,<b>c</b>) and the samples (<b>b</b>,<b>d</b>).</p> Full article ">
14 pages, 5923 KiB  
Article
Preparation of Copper-Doped Zinc Oxide (CZO) Nanoparticles and CZO/Acrylic Copolymer Emulsion with Polyvinylpyrrolidone (PVP) Coated on Glass Substrate for Optical Properties
by Pimpaka Putthithanas, Sujittra Kaenphakdee, Supan Yodyingyong, Wannapong Triampo, Noppakun Sanpo, Jaturong Jitputti and Darapond Triampo
Coatings 2024, 14(4), 502; https://doi.org/10.3390/coatings14040502 - 18 Apr 2024
Viewed by 1581
Abstract
This study investigated the effect of copper (Cu) doping content on zinc oxide with varied weight percentages and the dispersion of Cu-doped ZnO (CZO) by adding polyvinylpyrrolidone (PVP), coated on a glass substrate, through a physical assessment and optical property and thermal insulation [...] Read more.
This study investigated the effect of copper (Cu) doping content on zinc oxide with varied weight percentages and the dispersion of Cu-doped ZnO (CZO) by adding polyvinylpyrrolidone (PVP), coated on a glass substrate, through a physical assessment and optical property and thermal insulation testing. CZO NPs were synthesized by using the sol–gel method with a zinc acetate precursor. The powder X-ray diffraction (XRD) patterns of the CZO showed that the solid solubility limit was below 5 mol% without a secondary phase. A field-emission scanning electron microscopy (FE-SEM) micrograph demonstrated that the particle size of CZO was in nanoscale with the packing of a quasi-spherical shape. The UV-Vis-NIR reflectance spectra of the powder showed that 1 mol% CZO has the highest near-infrared (NIR) reflectivity in the wavelength 780–2500 nm, with great visible light transmission. The CZO NPs were loaded in acrylic copolymer in different weight percentages ranging from 25 wt% to 75 wt%, the film thickness of the coating was varied from 5 µm to 100 µm, and PVP was added into this nanocomposite polymer to disperse through an ultrasonication method. The results showed that the highest loading of CZO powder in a polymer at 75 wt% in 100 µm of thickness with polyvinylpyrrolidone (PVP) as a dispersant showed better sample dispersion and retained good transparency to the naked eye. Full article
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<p>House setup for IR thermal insulation testing.</p> Full article ">Figure 2
<p>Rietveld refinement of X-ray diffraction data of CZO nanopowder at room temperature.</p> Full article ">Figure 3
<p>FE-SEM micrographs of as-synthesized CZO powders: (<b>a</b>) 0 mol%, (<b>b</b>) 1 mol%, and (<b>c</b>) 10 mol% (100k× magnification).</p> Full article ">Figure 4
<p>UV-Vis-NIR reflectance spectra of CZO powders with different Cu doping contents.</p> Full article ">Figure 5
<p>CZO nanopowders coated on glass substrates by varied weight percentage of CZO content to acrylic copolymer (25, 50, and 75 wt%) and varying thicknesses (5, 25, 50, and 100 µm).</p> Full article ">Figure 6
<p>Transmittance spectra of CZO/acrylic copolymer-coated glass substrates with different thicknesses (5, 25, 50, and 100 µm): CZO 1 mol% of (<b>a</b>) 25 wt% CZO content and (<b>b</b>) 50 wt% CZO content in acrylic copolymer.</p> Full article ">Figure 7
<p>Transmittance spectra of CZO/acrylic copolymer-coated glass substrates with different thicknesses (5, 25, 50, and 100 µm) (75 wt% CZO/acrylic copolymer): (<b>a</b>) CZO 0 mol% without PVP, (<b>b</b>) CZO 0 mol% with PVP, (<b>c</b>) CZO 1 mol% without PVP, and (<b>d</b>) CZO 1 mol% with PVP.</p> Full article ">Figure 8
<p>The transmittance spectra of (<b>a</b>) the glass substrate and (<b>b</b>) the acrylic copolymer-coated glass substrate (100 µm thick).</p> Full article ">Figure 9
<p>CZO/acrylic copolymer coatings applied to glass substrates with 75 wt% CZO content in acrylic copolymer with different thicknesses (5, 25, 50, and 100 µm): (<b>a</b>) CZO 0 mol% without/with PVP and (<b>b</b>) CZO 1 mol% without/with PVP.</p> Full article ">Figure 10
<p>Temperature of the coated glass substrates after IR lamp irradiation for 1 h: (<b>a</b>) temperature on glass surface (T<sub>1</sub>) and (<b>b</b>) temperature inside the foam box (T<sub>2</sub>) of 25, 50, and 75 wt% CZO (1 mol%)/acrylic copolymers without PVP.</p> Full article ">Figure 11
<p>Temperature of the coated glass substrates after IR lamp irradiation for 1 h: (<b>a</b>) temperature on glass surface (T<sub>1</sub>) and (<b>b</b>) temperature inside the foam box (T<sub>2</sub>) of 75 wt% CZO (1 mol%)/acrylic copolymers without/with PVP.</p> Full article ">
15 pages, 3407 KiB  
Article
Automatic Defect Detection of Jet Engine Turbine and Compressor Blade Surface Coatings Using a Deep Learning-Based Algorithm
by Md Hasib Zubayer, Chaoqun Zhang, Wen Liu, Yafei Wang and Haque Md Imdadul
Coatings 2024, 14(4), 501; https://doi.org/10.3390/coatings14040501 - 18 Apr 2024
Cited by 1 | Viewed by 2169
Abstract
The application of additive manufacturing (AM) in the aerospace industry has led to the production of very complex parts like jet engine components, including turbine and compressor blades, that are difficult to manufacture using any other conventional manufacturing process but can be manufactured [...] Read more.
The application of additive manufacturing (AM) in the aerospace industry has led to the production of very complex parts like jet engine components, including turbine and compressor blades, that are difficult to manufacture using any other conventional manufacturing process but can be manufactured using the AM process. However, defects like nicks, surface irregularities, and edge imperfections can arise during the production process, potentivally affecting the operational integrity and safety of jet engines. Aiming at the problems of poor accuracy and below-standard efficiency in existing methodologies, this study introduces a deep learning approach using the You Only Look Once version 8 (YOLOv8) algorithm to detect surface, nick, and edge defects on jet engine turbine and compressor blades. The proposed method achieves high accuracy and speed, making it a practical solution for detecting surface defects in AM turbine and compressor blade specimens, particularly in the context of quality control and surface treatment processes in AM. The experimental findings confirmed that, in comparison to earlier automatic defect recognition procedures, the YOLOv8 model effectively detected nicks, edge defects, and surface defects in the turbine and compressor blade dataset, attaining an elevated level of accuracy in defect detection, reaching up to 99.5% in just 280 s. Full article
(This article belongs to the Special Issue Recent Advances in Additive Manufacturing Techniques)
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<p>Surface, nick, and edge defects observed in the manufacturing of turbine blades using AM.</p> Full article ">Figure 2
<p>Schematic experimental flowchart of the research approach.</p> Full article ">Figure 3
<p>Sample dataset images for the deep learning training. (<b>a</b>) Nick marks as orange, (<b>b</b>) red denotes the area of surface defects, and (<b>c</b>) purple squares signify edge defects.</p> Full article ">Figure 4
<p>The Overall improvement custom dataset.</p> Full article ">Figure 5
<p>Metrics for training and validation sets. (<b>a</b>) F1_curve; (<b>b</b>) PR_curve; (<b>c</b>) P_curve; (<b>d</b>) R_curve.</p> Full article ">Figure 6
<p>YOLOv8 performance evaluation. (<b>a</b>) Confusion matrix; (<b>b</b>) Performance results.</p> Full article ">Figure 7
<p>Surface defects detected by the YOLOv8 algorithm.</p> Full article ">
11 pages, 8933 KiB  
Article
Tunable Electronic and Optical Properties of MoGe2N4/AlN and MoSiGeN4/AlN van der Waals Heterostructures toward Optoelectronic and Photocatalytic Applications
by Jingyao Shao, Jian Zeng, Bin Xiao, Zhenwu Jin, Qiyun Wang, Zhengquan Li, Ling-Ling Wang, Kejun Dong and Liang Xu
Coatings 2024, 14(4), 500; https://doi.org/10.3390/coatings14040500 - 18 Apr 2024
Viewed by 1224
Abstract
Van der Waals (vdW) heterostructures provide an effective strategy for exploring and expanding the potential applications of two-dimensional materials. In this study, we employ first-principles density functional theory (DFT) to investigate the geometric, electronic, and optical properties of MoGe2N4/AlN [...] Read more.
Van der Waals (vdW) heterostructures provide an effective strategy for exploring and expanding the potential applications of two-dimensional materials. In this study, we employ first-principles density functional theory (DFT) to investigate the geometric, electronic, and optical properties of MoGe2N4/AlN and MoSiGeN4/AlN vdW heterostructures. The stable MoGe2N4/AlN heterostructure exhibits an indirect band gap semiconductor with a type-I band gap arrangement, making it suitable for optoelectronic devices. Conversely, the stable MoSiGeN4/AlN heterostructure demonstrates various band gap arrangements depending on stacking modes, rendering it suitable for photocatalysis applications. Additionally, we analyze the effects of mechanical strain and vertical electric field on the electronic properties of these heterostructures. Our results indicate that both mechanical strain and vertical electric field can adjust the band gap. Notably, application of an electric field or mechanical strain leads to the transformation of the MoGe2N4/AlN heterostructure from a type-I to a type-II band alignment and from an indirect to a direct band transfer, while MoSiGeN4/AlN can transition from a type-II to a type-I band alignment. Type-II band alignment is considered a feasible scheme for photocatalysis, photocells, and photovoltaics. The discovery of these characteristics suggests that MoGe2N4/AlN and MoSiGeN4/AlN vdW heterostructures, despite their high lattice mismatch, hold promise as tunable optoelectronic materials with excellent performance in optoelectronic devices and photocatalysis. Full article
(This article belongs to the Special Issue Advances in Two-Dimensional Materials: From Synthesis to Applications)
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<p>The geometric structure of (<b>a</b>) AlN, (<b>b</b>) MoGe<sub>2</sub>N<sub>4</sub>, and (<b>c</b>) MoSiGeN<sub>4</sub> monolayers. The calculated band structure and its DOS and PDOS of (<b>d</b>) AlN, (<b>e</b>) MoGe<sub>2</sub>N<sub>4</sub>, and (<b>f</b>) MoSiGeN<sub>4</sub> monolayers. The Fermi level was set to zero.</p> Full article ">Figure 2
<p>Top and side views of optimized (<b>a</b>) AB1, AB2, AB3 AB4, AB5, and AB6 different stacking modes of MoGe<sub>2</sub>N<sub>4</sub>/AlN; (<b>b</b>) AC1, AC2, AC3, AC4, AC5, and AC6 different stacking modes of MoSiGeN<sub>4</sub>/AlN.</p> Full article ">Figure 3
<p>The band structure of six different stacking heterostructures relative to (<b>a</b>) MoGe<sub>2</sub>N<sub>4</sub>/AlN and (<b>b</b>) MoSiGeN<sub>4</sub>/AlN. The Fermi level was set to zero.</p> Full article ">Figure 4
<p>The 3D charge density difference of heterostructures (<b>a</b>) MoGe<sub>2</sub>N<sub>4</sub>/AlN and (<b>b</b>) MoSiGeN<sub>4</sub>/AlN. The orange and green regions represent charge accumulation and consumption, respectively.</p> Full article ">Figure 5
<p>The band gap plots of (<b>a</b>) AlN/MoGe<sub>2</sub>N<sub>4</sub> and (<b>b</b>) AlN/MoSiGeN<sub>4</sub> as a function of the strain.</p> Full article ">Figure 6
<p>The band structure of (<b>a</b>) MoGe<sub>2</sub>N<sub>4</sub>/AlN and (<b>b</b>) MoSiGeN<sub>4</sub>/AlN under the action of an external electric field, with corresponding external electric field values at the bottom. The Fermi level was set to zero.</p> Full article ">Figure 7
<p>The optical absorption spectra of isolated monolayers and heterostructure. The ribbon area represents the visible light absorption range.</p> Full article ">
12 pages, 5557 KiB  
Communication
Preparation and Corrosion Resistance of Superhydrophobic Coatings on 7005 Aluminum Alloy
by Huilan Huang, Feng Guo, Xintao Li, Peng Xia, Li Yang and Chuanbo Hu
Coatings 2024, 14(4), 499; https://doi.org/10.3390/coatings14040499 - 17 Apr 2024
Viewed by 1132
Abstract
Composite coatings on the surface of a semi-continuous cast 7005 aluminum alloy under different aging treatments (T6, RRA, and FSA) are presented and characterized in this research. SiO2 combined with stearic acid (STA) modified by KH550 was utilized to achieve multifunctional superhydrophobic [...] Read more.
Composite coatings on the surface of a semi-continuous cast 7005 aluminum alloy under different aging treatments (T6, RRA, and FSA) are presented and characterized in this research. SiO2 combined with stearic acid (STA) modified by KH550 was utilized to achieve multifunctional superhydrophobic coatings. Adhesive tape adhesion, blade scratch, and mechanical wear tests were utilized to assess the durability of the superhydrophobic coatings. The results showed that the prepared coatings exhibited excellent superhydrophobicity, self-cleaning ability, and mechanical properties, especially the T6 temper alloy. This alloy had the largest CA value (156.5°) and the lowest SA value (4.3°). The composite coatings still exhibited excellent superhydrophobicity under mechanical damage. Furthermore, the alloys with STA/SiO2 displayed marvelous corrosion resistance efficiency. The T6 temper alloy with a protection rate of 73.8% had an approximately one-order-of-magnitude decrement in carrion current density. The composite coating can be effectively utilized in various industrial fields, thus extending its potential impact. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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<p>A schematic diagram of the fabrication of superhydrophobic coating on 7005 aluminum alloy.</p> Full article ">Figure 2
<p>Images of the dyed water droplets on the surface; CA and SA values of (<b>a</b>) RRA-, (<b>b</b>) T6-, and (<b>c</b>) FSA temper samples.</p> Full article ">Figure 3
<p>SEM images and corresponding high-magnification SEM images of (<b>a</b>,<b>d</b>) RRA, (<b>b</b>,<b>e</b>) T6, and (<b>c</b>,<b>f</b>) FSA temper samples modified with SiO<sub>2</sub> particles.</p> Full article ">Figure 4
<p>(<b>a</b>) FTIR spectra and (<b>b</b>) XPS survey spectra of SiO<sub>2</sub> and SKS powders; (<b>c</b>) C1s and (<b>d</b>) Si2p bands in high-resolution spectra.</p> Full article ">Figure 5
<p>XRD pattern of the powders before and after modification.</p> Full article ">Figure 6
<p>The self-cleaning property procedure of (<b>a</b>) RRA, (<b>b</b>) T6, and (<b>c</b>) FSA samples in oblique position; (<b>d</b>) self-cleaning state in horizontal position of RRA, T6, and FSA samples.</p> Full article ">Figure 7
<p>Coating adhesion tests of samples (<b>a</b>) adhesive tape peeling, (<b>b</b>) blade scratch peeling, as well as CA images after the tests.</p> Full article ">Figure 8
<p>Abrasion resistance test of superhydrophobic coating of RRA temper sample.</p> Full article ">Figure 9
<p>The CA values of coating at different temperatures.</p> Full article ">Figure 10
<p>Electrochemical test: (<b>a</b>) electrochemical test mode; (<b>b</b>) Tafel polarization curves of bare alloy and superhydrophobic coating under RRA, T6, and FSA conditions after immersion in 3.5% NaCl aqueous solution for 5 days.</p> Full article ">
2 pages, 721 KiB  
Correction
Correction: Rumyantsev et al. White Phosphate Coatings Obtained on Steel from Modified Cold Phosphating Solutions. Coatings 2022, 12, 70
by Evgeniy Rumyantsev, Varvara Rumyantseva and Viktoriya Konovalova
Coatings 2024, 14(4), 498; https://doi.org/10.3390/coatings14040498 - 17 Apr 2024
Cited by 1 | Viewed by 652
Abstract
In the original publication [...] Full article
(This article belongs to the Special Issue Efficiency of Coatings Formed in Various Ways)
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<p>3-D surface models of phosphate coatings: (<b>a</b>) From a modified solution; (<b>b</b>) From a solution with the addition of zinc nitrate; (<b>c</b>) From a solution with the addition of calcium nitrate.</p> Full article ">Figure 4 Cont.
<p>3-D surface models of phosphate coatings: (<b>a</b>) From a modified solution; (<b>b</b>) From a solution with the addition of zinc nitrate; (<b>c</b>) From a solution with the addition of calcium nitrate.</p> Full article ">
17 pages, 1846 KiB  
Article
A Reduced-Order FEM Based on POD for Solving Non-Fourier Heat Conduction Problems under Laser Heating
by Fanglu Kou, Xiaohua Zhang, Baojing Zheng and Hui Peng
Coatings 2024, 14(4), 497; https://doi.org/10.3390/coatings14040497 - 17 Apr 2024
Viewed by 861
Abstract
The study presents a novel approach called FEM-POD, which aims to enhance the computational efficiency of the Finite Element Method (FEM) in solving problems related to non-Fourier heat conduction. The present method employs the Proper Orthogonal Decomposition (POD) technique. Firstly, spatial discretization of [...] Read more.
The study presents a novel approach called FEM-POD, which aims to enhance the computational efficiency of the Finite Element Method (FEM) in solving problems related to non-Fourier heat conduction. The present method employs the Proper Orthogonal Decomposition (POD) technique. Firstly, spatial discretization of the second-order hyperbolic differential equation system is achieved through the Finite Element Method (FEM), followed by the application of the Newmark method to address the resultant ordinary differential equation system over time, with the resultant numerical solutions collected in snapshot form. Next, the Singular Value Decomposition (SVD) is employed to acquire the optimal proper orthogonal decomposition basis, which is subsequently combined with the FEM utilizing the Newmark scheme to construct a reduced-order model for non-Fourier heat conduction problems. To demonstrate the effectiveness of the suggested method, a range of numerical instances, including different laser heat sources and relaxation durations, are executed. The numerical results validate its enhanced computational accuracy and highlight significant time savings over addressing non-Fourier heat conduction problems using the full order FEM with the Newmark approach. Meanwhile, the numerical results show that when the number of elements or nodes is relatively large, the CPU running time of the FEM-POD method is even hundreds of times faster than that of classical FEM with the Newmark scheme. Full article
(This article belongs to the Section Laser Coatings)
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<p>Distribution of eigenvalues with <math display="inline"><semantics> <mrow> <mn>20</mn> <mo>×</mo> <mn>20</mn> </mrow> </semantics></math> square elements for Example 1.</p> Full article ">Figure 2
<p>The relationship between the <math display="inline"><semantics> <msup> <mi>L</mi> <mn>2</mn> </msup> </semantics></math> norm error of FEM-POD and the number of POD basis for Example 1 with <math display="inline"><semantics> <mrow> <mn>20</mn> <mo>×</mo> <mn>20</mn> </mrow> </semantics></math> square elements and <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <mi>t</mi> <mo>=</mo> <mn>0.001</mn> </mrow> </semantics></math>.</p> Full article ">Figure 3
<p>Temperature and its absolute error versus time at points A(0.6, 0.2), B(0.6, 0.4) and C(0.6, 0.6) with <math display="inline"><semantics> <mrow> <mi>r</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics></math> for Example 1.</p> Full article ">Figure 4
<p>Distribution of eigenvalues with different nodes for Example 2.</p> Full article ">Figure 5
<p>Temperature versus time at points A(0.0, 0.25), B(1.0, 0.25) and C(3.0, 0.25) with different relaxation time for Case 1.</p> Full article ">Figure 6
<p>Temperature versus time at points A(0.0, 0.25), B(1.0, 0.25) and C(3.0, 0.25) with different relaxation time for Case 2.</p> Full article ">Figure 7
<p>Temperature versus time at points A(0.0, 0.25), B(1.0, 0.25) and C(3.0, 0.25) with different relaxation time for Case 3.</p> Full article ">Figure 8
<p>Schematic diagram of geometry and mesh for Example 3.</p> Full article ">Figure 9
<p>Distribution of eigenvalues with 1320 nodes and 1200 elements for Example 3.</p> Full article ">Figure 10
<p>Temperature contours of FEM and FEM-POD at time <math display="inline"><semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>10</mn> </mrow> </semantics></math> s with 1320 nodes for Example 3.</p> Full article ">Figure 11
<p>Temperature contours of FEM and FEM-POD at time <math display="inline"><semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>250</mn> </mrow> </semantics></math> s with 1320 nodes for Example 3.</p> Full article ">Figure 12
<p>Distribution of temperature versus time at points A(0, −0.07), B(0.07, 0) and C(0, 0.07) with 1320 nodes for Example 3.</p> Full article ">Figure 13
<p>The pulse laser heating arrangement for the three-dimensional model in Example 4.</p> Full article ">Figure 14
<p>Distribution of eigenvalues with <math display="inline"><semantics> <mrow> <mn>80</mn> <mo>×</mo> <mn>80</mn> <mo>×</mo> <mn>5</mn> </mrow> </semantics></math> hexahedral elements for Example 4.</p> Full article ">Figure 15
<p>Temperature distribution of FEM at time <math display="inline"><semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>25</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">s</mi> </mrow> </mrow> </semantics></math> with <math display="inline"><semantics> <mrow> <mn>80</mn> <mo>×</mo> <mn>80</mn> <mo>×</mo> <mn>5</mn> </mrow> </semantics></math> hexahedral elements along <math display="inline"><semantics> <mrow> <mi>z</mi> <mo>=</mo> <mn>50</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> <mo>,</mo> <mn>25</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> <mo>,</mo> <mn>0</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> </mrow> </semantics></math>, respectively.</p> Full article ">Figure 16
<p>Temperature distribution of FEM-POD at time <math display="inline"><semantics> <mrow> <mi>t</mi> <mo>=</mo> <mn>25</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">s</mi> </mrow> </mrow> </semantics></math> with <math display="inline"><semantics> <mrow> <mn>80</mn> <mo>×</mo> <mn>80</mn> <mo>×</mo> <mn>5</mn> </mrow> </semantics></math> hexahedral elements along <math display="inline"><semantics> <mrow> <mi>z</mi> <mo>=</mo> <mn>50</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> <mo>,</mo> <mn>25</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> <mo>,</mo> <mn>0</mn> <mrow> <mspace width="3.33333pt"/> <mi mathvariant="sans-serif">μ</mi> <mi mathvariant="normal">m</mi> </mrow> </mrow> </semantics></math>, respectively.</p> Full article ">Figure 17
<p>Distribution of temperature versus time at points A, B and C for Example 4.</p> Full article ">
12 pages, 3792 KiB  
Article
Controlling the Superconducting Critical Temperature and Resistance of NbN Films through Thin Film Deposition and Annealing
by Yang Pei, Qian Fan, Xianfeng Ni and Xing Gu
Coatings 2024, 14(4), 496; https://doi.org/10.3390/coatings14040496 - 17 Apr 2024
Viewed by 1590
Abstract
This study investigated the relationship between the superconducting properties, electrical properties, sputtering process parameters, and post-growth annealing of NbN films. Four series of NbN films were deposited by DC magnetron sputtering using different process parameters. With the assistance of a four-probe method, the [...] Read more.
This study investigated the relationship between the superconducting properties, electrical properties, sputtering process parameters, and post-growth annealing of NbN films. Four series of NbN films were deposited by DC magnetron sputtering using different process parameters. With the assistance of a four-probe method, the superconducting performance presented first an increase and then a decreasing trend as the resistance of the prepared films increased, which could be attributed to the variation of the N/Nb ratio in the films. This correlation implied that it is very challenging to fabricate films with both high Tc and high resistance or high Tc and low resistance by adjusting the sputtering process parameters. In order to overcome these bottlenecks, a series of films were deposited on Si, GaN/Si, SiN/Si, AlN/Si, and AlN/sapphire substrates, and the film deposited on Si was annealed at 900 °C. Annealing reduced the stress of the films on the buffer layer and increased the grain size and crystallinity of the films, except for the films on the GaN/Si substrates. This resulted in a significant decrease in the resistivity of the film and a significant increase in the superconducting transition temperature. Full article
(This article belongs to the Section Thin Films)
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<p>The relationship between resistance, growth rate (black squares), and Tc (red squares) for all films from Series 1 to Series 4.</p> Full article ">Figure 2
<p>SEM and EDS test results of (<b>a</b>) 1%–7.9%, (<b>b</b>) 3–120 W, (<b>c</b>) 4–300 °C, (<b>d</b>) 1%–30%, and (<b>e</b>) 2–180 W, which are marked in <a href="#coatings-14-00496-f001" class="html-fig">Figure 1</a>.</p> Full article ">Figure 3
<p>Tc of NbN films in Series 5.</p> Full article ">Figure 4
<p>Electrical resistance of NbN films in Series 5 before and after annealing.</p> Full article ">Figure 5
<p>XRD ω–2θ scans of (<b>a</b>) Si, (<b>b</b>) SiN/Si, (<b>c</b>) AlN/Si, and (<b>d</b>) AlN/sapphire substrates. NbN films were deposited on the substrates and the films were annealed at 900 °C. The smaller picture on the right side (purple dotted square in the left picture) shows a higher resolution scan of the δ-NbN (111) peak at around 36° obtained by decreasing the scan step size.</p> Full article ">Figure 5 Cont.
<p>XRD ω–2θ scans of (<b>a</b>) Si, (<b>b</b>) SiN/Si, (<b>c</b>) AlN/Si, and (<b>d</b>) AlN/sapphire substrates. NbN films were deposited on the substrates and the films were annealed at 900 °C. The smaller picture on the right side (purple dotted square in the left picture) shows a higher resolution scan of the δ-NbN (111) peak at around 36° obtained by decreasing the scan step size.</p> Full article ">Figure 6
<p>The lattice constants (black) and FWHM (red) of films deposited on Si, AlN/Si, and SiN/Si substrates before and after annealing.</p> Full article ">Figure 7
<p>The SEM of films deposited on Si (<b>a</b>) before and (<b>f</b>) after 900 °C annealing, SiN/Si (<b>b</b>) before and (<b>g</b>) after 900 °C annealing, GaN/Si (<b>c</b>) before and (<b>h</b>) after 750 °C annealing, AlN/Si (<b>d</b>) before and (<b>i</b>) after 900 °C annealing, and AlN/sapphire (<b>e</b>) before and (<b>j</b>) after 900 °C annealing.</p> Full article ">Figure 8
<p>The AFM test results of Si, GaN/Si, SiN/Si, AlN/Si, and AlN/sapphire and NbN films deposited on them.</p> Full article ">
18 pages, 9151 KiB  
Article
Corrosion Behavior of Hybrid Zinc Coatings Based on Chitosan and Corrosion Inhibitor BTA: Effect of the Molecular Weight and ζ-Potential
by Viktoria Milkova, Nelly Boshkova, Georgy Grancharov, Olya Stoilova and Nikolai Boshkov
Coatings 2024, 14(4), 495; https://doi.org/10.3390/coatings14040495 - 17 Apr 2024
Viewed by 1023
Abstract
The creation of anticorrosion hybrid zinc-based coatings containing chitosan particles with low (LMC) or high (HMC) molecular weight is an effective method for safe and durable exploitation of different steel infrastructures. In this work, hybrid coatings consisting of zinc and two types of [...] Read more.
The creation of anticorrosion hybrid zinc-based coatings containing chitosan particles with low (LMC) or high (HMC) molecular weight is an effective method for safe and durable exploitation of different steel infrastructures. In this work, hybrid coatings consisting of zinc and two types of chitosan particles (LMC or HMC) were obtained to protect low-carbon steel from corrosion attack in a chloride environment. Chitosans with different molecular weights (CS50 Mw 50–190 kDa and CS190 Mw 190–310 kDa) have been applied. Furthermore, both particle types were prepared with or without additional content of incorporated corrosion inhibitor benzotriazole (BTA). The chitosan particles were obtained and thereafter electrodeposited in the form of hybrid coatings on mild steel substrates. The electrokinetic charge and hydrodynamic size of the particles and the stability of their aqueous suspensions were evaluated using dynamic light scattering. The concentration of BTA loaded into the particles was determined by the difference between the initial concentration of the compound added during the particle preparation and the concentration in the supernatant after centrifugation of the dispersion. The hybrid coatings were compared concerning their surface morphology, topography, and hydrophilicity (SEM and AFM analysis, water contact angle measurement) as well as corrosion and electrochemical behavior (potentiodynamic polarization curves—PD, polarization resistance—Rp, cyclic voltammetry—CVA). The protective characteristics of the coatings were studied in 5% NaCl solution. The results obtained from the PD studies demonstrated lower corrosion current densities of all hybrid coatings compared to the ordinary zinc one. In addition, the Rp tests showed enhanced protective ability and corrosion resistance of LMC and LMCB compared to the ordinary zinc, HMC, and HMCB, respectively. The obtained scientific information presented the effect of the molecular weight and ζ-potential of the particles on the anticorrosion ability of the hybrid coatings compared to the ordinary zinc one. Full article
(This article belongs to the Special Issue Corrosion and Anticorrosion of Alloys/Metals)
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<p>Dispersions of the produced BTA-loaded chitosan-based particles formed from CS190 (<b>left</b>) and CS50 (<b>right</b>).</p> Full article ">Figure 2
<p>Calibration curve used for estimation of the concentration of BTA in buffer with pH 7 (y = 80.79×).</p> Full article ">Figure 3
<p>SEM images of hybrid LMC (<b>a</b>,<b>b</b>) and LMCB (<b>c</b>,<b>d</b>) coatings before (<b>a</b>,<b>c</b>) and after (<b>b</b>,<b>d</b>) corrosion treatment in model medium of 5% NaCl solution.</p> Full article ">Figure 4
<p>SEM images of hybrid HMC (<b>a</b>,<b>b</b>) and HMCB (<b>c</b>,<b>d</b>) coatings before (<b>a</b>,<b>c</b>) and after (<b>b</b>,<b>d</b>) corrosion treatment in model medium of 5% NaCl solution.</p> Full article ">Figure 5
<p>Cyclic voltammetry measurements in starting solutions for hybrid (LMC and LMCB) and ordinary zinc (Zn) coatings.</p> Full article ">Figure 6
<p>Cyclic voltammetry measurements in starting solutions for hybrid (HMC and HMCB) and ordinary zinc (Zn) coatings.</p> Full article ">Figure 7
<p>Potentiodynamic polarization curves of ordinary zinc (Zn) and hybrid coatings LMC and LMCB.</p> Full article ">Figure 8
<p>Potentiodynamic polarization curves of ordinary zinc (Zn) and hybrid coatings HMC and HMCB.</p> Full article ">Figure 9
<p>Polarization resistance of ordinary zinc (Zn) and hybrid coatings LMC and LMCB.</p> Full article ">Figure 10
<p>Polarization resistance of ordinary zinc (Zn) and hybrid coatings HMC and HMCB.</p> Full article ">Figure 11
<p>AFM tapping mode 2D and 3D images of the hybrid coatings of: (<b>a</b>) LMC; (<b>b</b>) LMCB; (<b>c</b>) HMC; and (<b>d</b>) HMCB.</p> Full article ">Figure 12
<p>AFM tapping mode phase images of the hybrid coatings of: (<b>a</b>) LMC; (<b>b</b>) LMCB; (<b>c</b>) HMC; and (<b>d</b>) HMCB.</p> Full article ">Figure 13
<p>WCA values and representative images of the droplets poured onto hybrid coatings of: LMC (blue); HMC (red); LMCB (green), and HMCB (orange).</p> Full article ">
1 pages, 133 KiB  
Retraction
RETRACTED: Alshahrani et al. Mechanical Properties Study on Sandwich Composites of Glass Fiber Reinforced Plastics (GFRP) Using Liquid Thermoplastic Resin, Elium®: Preliminary Experiments. Coatings 2022, 12, 1423
by Hassan Alshahrani, Azzam Ahmed, Hashim Kabrein and V. R. Arun Prakash
Coatings 2024, 14(4), 494; https://doi.org/10.3390/coatings14040494 - 17 Apr 2024
Viewed by 797
Abstract
The Coatings Editorial Office retracts the article, “Mechanical Properties Study on Sandwich Composites of Glass Fiber Reinforced Plastics (GFRP) Using Liquid Thermoplastic Resin, Elium®: Preliminary Experiments” [...] Full article
15 pages, 24803 KiB  
Article
Quality of Zinc Coating Formed on Structural Steel by Hot-Dip Galvanizing after Surface Contamination
by Jiřina Vontorová, Petr Mohyla and Kateřina Kreislová
Coatings 2024, 14(4), 493; https://doi.org/10.3390/coatings14040493 - 17 Apr 2024
Cited by 2 | Viewed by 1610
Abstract
This paper deals with the evaluation of the surface of structural steel whose samples were deliberately contaminated with transparent spray primer, adhesive label glue, and welding sprays prior to hot-dip galvanizing. The galvanized samples were studied by optical microscopy, GDOES, adhesion tests, and [...] Read more.
This paper deals with the evaluation of the surface of structural steel whose samples were deliberately contaminated with transparent spray primer, adhesive label glue, and welding sprays prior to hot-dip galvanizing. The galvanized samples were studied by optical microscopy, GDOES, adhesion tests, and condensation humidity tests. The effect of surface contamination on the quality of the zinc coating was found to be significant. In some cases, the zinc coating is damaged (after contamination with welding sprays), in others, it is completely absent (after contamination with spray primer or adhesive label glue). Full article
(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)
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<p>Structure of hot-dip zinc coatings [<a href="#B25-coatings-14-00493" class="html-bibr">25</a>].</p> Full article ">Figure 2
<p>Microstructure of Kosmalt E300T steel, magnification 200× (<b>a</b>), magnification 1000× (<b>b</b>).</p> Full article ">Figure 3
<p>Hot-dip galvanizing process of the studied samples in an industrial galvanizing plant; (<b>a</b>) after degreasing, (<b>b</b>) after galvanizing; (photo by the author).</p> Full article ">Figure 4
<p>Photographs of samples before hot-dip galvanizing (<b>a</b>) and after hot-dip galvanizing (<b>b</b>).</p> Full article ">Figure 5
<p>Microstructure of sample A: Zn coating without contamination, magnification 200×.</p> Full article ">Figure 6
<p>GDOES profile analysis of sample A: Zn coating without contamination.</p> Full article ">Figure 7
<p>Microstructure of sample B: contamination with transparent spray primer, magnification 200×: (<b>a</b>) oxide layer, (<b>b</b>) Zn coating fragment.</p> Full article ">Figure 8
<p>Microstructure of sample C: contamination with adhesive label glue, magnification 200×.</p> Full article ">Figure 9
<p>Microstructure of sample D: (<b>a</b>) Zn coating in the area of transition from base metal to weld metal, magnification 200×; (<b>b</b>) Zn coating on the spatter, magnification 50×.</p> Full article ">Figure 10
<p>Microstructure of sample E: (<b>a</b>) Zn coating in the area of transition from base metal to weld metal, magnification 200×; (<b>b</b>) Zn coating on base material, magnification 100×.</p> Full article ">Figure 11
<p>Microstructure of samples F (<b>a</b>) and G (<b>b</b>): Zn coating in the area of transition from base metal to weld metal, magnification 200×.</p> Full article ">Figure 12
<p>Sample E: Measurement of Zn coating thickness at the transition from base material to weld metal, magnification 100×.</p> Full article ">Figure 13
<p>Sample A: (<b>a</b>) image after adhesion test; (<b>b</b>) surface after the test—3D microscope, magnification 50×.</p> Full article ">Figure 14
<p>Sample E: Image after adhesion test.</p> Full article ">Figure 15
<p>Sample E: Image after adhesion test: (<b>a</b>) detail of the scratch on the weld metal, magnification 50×; (<b>b</b>) detail of scratch outside the weld metal, magnification 20×.</p> Full article ">Figure 16
<p>Samples A–G (<b>a</b>–<b>g</b>): image after condensation humidity test.</p> Full article ">
15 pages, 15433 KiB  
Article
Tribological Properties of Hard TiB2 Thin Films Prepared at Low Temperatures Using HiPIMS
by Jianjian Yu, Ping Zhang, Puyou Ying, Changhong Lin, Tao Yang, Jianbo Wu, Chen Li, Min Huang and Vladimir Levchenko
Coatings 2024, 14(4), 492; https://doi.org/10.3390/coatings14040492 - 16 Apr 2024
Cited by 2 | Viewed by 1057
Abstract
Magnetron-sputtered WS2 composite thin films are solid lubricants with excellent performances. However, the low hardness of the WS2 thin films necessitates the further improvement of their wear resistance. For this purpose, an effective strategy is to alternately deposit or code posit [...] Read more.
Magnetron-sputtered WS2 composite thin films are solid lubricants with excellent performances. However, the low hardness of the WS2 thin films necessitates the further improvement of their wear resistance. For this purpose, an effective strategy is to alternately deposit or code posit WS2 and a hard phase, such as TiB2, to form hard lubricant thin films. Herein, a TiB2 thin film was prepared under the same conditions as those used for depositing the WS2 thin film with a dense structure and excellent tribological properties. Because of the high deposition energy of high-power impulse magnetron sputtering (HiPIMS), the TiB2 thin film possesses a dense structure and leather-like flat surface (hardness = 24.17 GPa). The friction coefficient of the film under different loads ranges between 0.6 and 0.8. The wear rate of the thin film increases with load, mainly because of fatigue wear and abrasive wear. Under high loads, obvious furrow-like wear marks are observed. At different sliding frequencies, except 8 Hz, the friction coefficient of the film ranges from 0.6 to 0.8. The main wear mode is fatigue wear, particularly at increasing sliding frequencies. Although the film possesses a relatively high friction coefficient, its wear resistance is excellent (minimum wear rate = 1.96 × 10−6 mm3/(N·m)). Full article
(This article belongs to the Special Issue Nanostructured Films and Their Multi-scale Applications)
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Figure 1

Figure 1
<p>Flow chart of TiB<sub>2</sub> thin-film friction test process.</p> Full article ">Figure 2
<p>SEM images of the surface morphology of (<b>a</b>) the Ti transition layer and (<b>b</b>) the TiB<sub>2</sub> thin film at ×100 k.</p> Full article ">Figure 3
<p>SEM images of the cross-sectional morphology of the TiB<sub>2</sub> thin film at (<b>a</b>) ×50 k and (<b>b</b>) ×100 k.</p> Full article ">Figure 4
<p>XRD patterns of deposited TiB<sub>2</sub> thin film.</p> Full article ">Figure 5
<p>Acoustic emission folding diagram of the TiB<sub>2</sub> thin film.</p> Full article ">Figure 6
<p>Optical map of a scratch of the TiB<sub>2</sub> thin film.</p> Full article ">Figure 7
<p>Friction coefficient of the TiB<sub>2</sub> thin film under different friction loads.</p> Full article ">Figure 8
<p>Histogram of the wear rate of the TiB<sub>2</sub> thin film under different loads.</p> Full article ">Figure 9
<p>Morphological images of abrasion marks on the TiB<sub>2</sub> thin film under the friction loads of (<b>a</b>) 5, (<b>b</b>) 10, (<b>c</b>) 15, and (<b>d</b>) 20 N.</p> Full article ">Figure 10
<p>SEM images and EDS surface scanning analysis results of local wear traces under the loads of (<b>a</b>) 5, (<b>b</b>) 10, (<b>c</b>) 15, and (<b>d</b>) 20 N.</p> Full article ">Figure 11
<p>Local magnification of the abrasion marks on the TiB<sub>2</sub> thin film under the friction loads of (<b>a</b>) 5, (<b>b</b>) 10, (<b>c</b>) 15, and (<b>d</b>) 20 N.</p> Full article ">Figure 12
<p>Friction coefficient of the TiB<sub>2</sub> thin film at different sliding frequencies.</p> Full article ">Figure 13
<p>Histogram of the wear rate of the TiB<sub>2</sub> thin film at different sliding frequencies.</p> Full article ">Figure 14
<p>Wear morphology of the TiB<sub>2</sub> thin film at the sliding frequencies of (<b>a</b>) 2, (<b>b</b>) 4, (<b>c</b>) 6, and (<b>d</b>) 8 Hz.</p> Full article ">Figure 15
<p>EDS patterns of TiB<sub>2</sub>-coated abrasion marks at the sliding frequencies of (<b>a</b>) 2, (<b>b</b>) 4, (<b>c</b>) 6, and (<b>d</b>) 8 Hz.</p> Full article ">Figure 16
<p>SEM images of the abrasion marks of the TiB<sub>2</sub> thin film at (<b>a</b>) 2 Hz, 500×; (<b>b</b>) 4 Hz, 500×; (<b>c</b>) 6 Hz, 600×; and (<b>d</b>) 8 Hz, 500×.</p> Full article ">
14 pages, 8016 KiB  
Article
Study on Electrochemical Corrosion of Q235 Steel in Sand Containing HA Solution under a Natural Air-Dried State
by Ruizhen Xie, Yage Bao, Ruicheng Geng, Qi Zhang, Haosheng Hou, Yakang Wang, Boqiong Li, Pengju Han, Zhenxia Wang, Shiying Wang, Naiming Lin and Baojie Dou
Coatings 2024, 14(4), 491; https://doi.org/10.3390/coatings14040491 - 16 Apr 2024
Viewed by 1023
Abstract
To explore the corrosion of Q235 steel in sand containing a simulated haze aqueous solution (HA solution) under a natural air-dried state, the effect of moisture (age) on the corrosion of Q235 steel in sand was comprehensively studied by EIS, polarization curve, SEM, [...] Read more.
To explore the corrosion of Q235 steel in sand containing a simulated haze aqueous solution (HA solution) under a natural air-dried state, the effect of moisture (age) on the corrosion of Q235 steel in sand was comprehensively studied by EIS, polarization curve, SEM, EDS and XPS. The physical and chemical properties of the sand showed that the sand containing the HA solution was basically neutral under natural air drying, and the temperature was around 20 °C. After 14 days, the moisture content gradually decreased from 30% to 0%, and the salinity decreased from 1.26% to 0.04%. With the increase in age, the Eocp gradually positively skews, indicating the corrosion kinetics of the Q235 steel decrease. The impedance spectra showed that in the frequency of 10−2–103 Hz, the impedance spectra exhibited a flat capacitive loop, and the corrosion of Q235 steel was the strongest in the sand containing HA solution on the 8 d. The polarization curves showed that with increasing age, the degree of corrosion of Q235 steel changed from medium or above to slight corrosion in the sand containing HA solution. The pitting characteristics of anode branch for polarization curve also indicate the faster corrosion kinetics of Q235 steel in the early age (1–5 d). The corrosion current density Io first increased and then decreased, and the highest value was 3.44 × 10−5 A/cm2 at 6 d. The average corrosion rate was 0.1629 mm/a. HA solution accelerates the corrosion of Q235 steel in sand without HA solution (average corrosion rate, 1.51 × 10−2 mm/a). A large amount of brown-yellow corrosion products (iron oxides, about 70–200 μm) presented on the surface of the Q235 steel. The corrosion of Q235 steel belonged to local corrosion, and the corrosion pits were connected to form a large dimple-like area. The HA solution and the porous structure of sand jointly affect the electrochemical corrosion of Q235 steel. Full article
(This article belongs to the Special Issue Detection and Monitoring of Corrosion in Steel Structures)
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<p>Open circuit potential of Q235 steel in sand containing HA solution: 1–14 d.</p> Full article ">Figure 2
<p>Nyquist diagram of Q235 steel in sand containing HA solution: (<b>a</b>) 1 d–7 d; (<b>b</b>) 8 d–14 d.</p> Full article ">Figure 3
<p>Modulus of Q235 steel in sand containing HA solution: (<b>a</b>) 1 d–7 d; (<b>b</b>) 8 d–14 d.</p> Full article ">Figure 4
<p>Phase angle of Q235 steel in sand containing HA solution: (<b>a</b>) 1 d–7 d; (<b>b</b>) 8 d–14 d.</p> Full article ">Figure 5
<p>Equivalent circuit model of sand-steel interface.</p> Full article ">Figure 6
<p>Equivalent circuit fitting results of the impedance spectra of Q235 steel in sand containing HA solution (1 d–7 d).</p> Full article ">Figure 7
<p>Equivalent circuit fitting results of the impedance spectra of Q235 steel in sand containing HA solution (8 d–14 d).</p> Full article ">Figure 8
<p>Polarization curves of Q235 steel in sand containing HA solution: (<b>a</b>) 1 d–7 d; (<b>b</b>) 8 d–14 d.</p> Full article ">Figure 9
<p>Macroscopic corrosion morphology of Q235 steel in sand containing HA solution: (<b>a</b>) 2D image; (<b>b</b>) 3D image (The area in the red circle will be further analyzed by EDS and XPS).</p> Full article ">Figure 10
<p>SEM images of corrosion products on the surface of Q235 steel in sand containing HA solution: (<b>a</b>) ×50; (<b>b</b>) ×100; (<b>c</b>) ×200; (<b>d</b>) ×500; (<b>e</b>) ×1000.</p> Full article ">Figure 11
<p>XPS of the corrosion products on Q235 steel: (<b>a</b>) full spectrum and elemental chemical bond analysis: (<b>b</b>) O1s fine spectrum; (<b>c</b>) Fe2p fine spectrum; (<b>d</b>) Na1s fine spectrum; (<b>e</b>) C1s fine spectrum.</p> Full article ">Figure 12
<p>Microscopic corrosion morphology of Q235 steel in sand containing HA solution after rust cleaning: (<b>a</b>) ×50; (<b>b</b>) ×100; (<b>c</b>) ×200; (d) ×500; (<b>e</b>) ×1000.</p> Full article ">
11 pages, 3973 KiB  
Article
The Effect of Intumescent Coating Containing Expandable Graphite onto Spruce Wood
by Elena Kmeťová, Danica Kačíková and František Kačík
Coatings 2024, 14(4), 490; https://doi.org/10.3390/coatings14040490 - 16 Apr 2024
Cited by 4 | Viewed by 1749
Abstract
Wood, one of the materials predominantly employed in construction, possesses various advantageous properties alongside certain drawbacks, such as susceptibility to thermal degradation. To enhance wood fire resistance, one approach involves the application of flame retardants. This study compared the fire-retardant effectiveness of expandable [...] Read more.
Wood, one of the materials predominantly employed in construction, possesses various advantageous properties alongside certain drawbacks, such as susceptibility to thermal degradation. To enhance wood fire resistance, one approach involves the application of flame retardants. This study compared the fire-retardant effectiveness of expandable graphite, bonded with water glass, as a coating for spruce wood against commercially available fire-retardant treatments. Spruce wood samples (Picea abies (L.) H. Karst) underwent treatment with three distinct retardants: expandable graphite in combination with water glass, Bochemit Antiflash, and Bochemit Pyro. The fire-technical characteristics of the samples were examined by a non-standard test method—a test with a radiant heat source. The experiment evaluated the fire-retardant properties by recording changes in sample mass, burning rate, and temperature difference. The best results among all flame retardants were achieved by expandable graphite in combination with water glass, in all evaluation criteria. Among all the flame retardants used, expandable graphite in combination with water glass achieved the best results in all evaluation criteria. Full article
(This article belongs to the Special Issue Advances in Surface Modification and Coatings of Wood and Wood Composites)
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Figure 1
<p>Locations of points for thermal camera measurement (<b>a</b>) and infrared snapshot (<b>b</b>).</p> Full article ">Figure 2
<p>Photo documentation of samples after testing with a radiant heat source (1—untreated sample, 2—graphite with water glass, 3—Bochemit Antiflash, 4—Bochemit Pyro).</p> Full article ">Figure 3
<p>Relative mass loss of the samples during the test with a radiant heat source (untreated = reference samples, EG + WG = expandable graphite in combination with water glass, antiflash = Bochemit Antiflash, pyro = Bochemit Pyro).</p> Full article ">Figure 4
<p>Relative burning rate of the samples during the test with a radiant heat source (untreated = reference samples, EG + WG = expandable graphite in combination with water glass, antiflash = Bochemit Antiflash, pyro = Bochemit Pyro).</p> Full article ">Figure 5
<p>Temperature course of the samples at point A (untreated = reference samples, EG + WG = expandable graphite in combination with water glass, antiflash = Bochemit Antiflash, pyro = Bochemit Pyro).</p> Full article ">Figure 6
<p>Temperature course of the samples at point B (untreated = reference samples, EG + WG = expandable graphite in combination with water glass, antiflash = Bochemit Antiflash, pyro = Bochemit Pyro).</p> Full article ">Figure 7
<p>Relative temperature course of the samples at point C (untreated = reference samples, EG + WG = expandable graphite in combination with water glass, antiflash = Bochemit Antiflash, pyro = Bochemit Pyro).</p> Full article ">Figure 8
<p>Temperature course of the samples at point D (untreated = reference samples, EG + WG = expandable graphite in combination with water glass, antiflash = Bochemit Antiflash, pyro = Bochemit Pyro).</p> Full article ">
12 pages, 3999 KiB  
Article
Establishment of a Uniaxial Tensile Fracture Inversion Model Based on Fracture Surface Reconstruction (FRASTA)
by Haidong Jia, Zhenghao Jiao, Lianshuang Dai, Yongbin Que, Qingshan Feng, Ming Yang and Yuguang Cao
Coatings 2024, 14(4), 489; https://doi.org/10.3390/coatings14040489 - 16 Apr 2024
Viewed by 1091
Abstract
In order to infer the load on the component after the experimental uniaxial tensile fracture inversion model based on cross-sectional reconstruction, (FRASTA) was proposed to infer the load on the tested components. This model can combine the fracture surface characteristics of experimental specimens [...] Read more.
In order to infer the load on the component after the experimental uniaxial tensile fracture inversion model based on cross-sectional reconstruction, (FRASTA) was proposed to infer the load on the tested components. This model can combine the fracture surface characteristics of experimental specimens to reconstruct the fracture surface morphology and invert the fracture process of uniaxial tensile specimens. Based on the assumption of rectangular rod fracture, a quantitative inversion model for a unidirectional stress load based on dissipative plasticity characteristics was established, and the inversion results based on cross-sectional reconstruction were compared with the experimental measurement results. The results indicate that when only considering the unidirectional stress state, the two have a high degree of consistency, with a maximum measurement error of 5.3%, fully verifying the accuracy of the fracture surface reconstruction and inversion model. Full article
(This article belongs to the Special Issue Material Surface Treatment Technology for a New Era)
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<p>Design drawing of uniaxial tensile specimen.</p> Full article ">Figure 2
<p>Schematic diagram of DIC shooting mode.</p> Full article ">Figure 3
<p>Load displacement curve measured experimentally.</p> Full article ">Figure 4
<p>Specimen positioning diagram.</p> Full article ">Figure 5
<p>Fracture scanning result graph. (<b>a</b>) Reconstruction of three-dimensional morphology of upper fracture surface. (<b>b</b>) Reconstruction of 3D morphology of lower fracture surface. (X: Length (mm)).</p> Full article ">Figure 6
<p>Initial state inversion results. (X: Length (mm) and Y: Width (mm)).</p> Full article ">Figure 7
<p>Lines of fracture surface (middle section). (X: Length (mm) and Y: Height (mm)).</p> Full article ">Figure 8
<p>The difference between the upper and lower fracture surfaces of corresponding position (reference position). (X: Length (mm) and Y: Height (mm)).</p> Full article ">Figure 9
<p>The difference between the upper and lower fracture surfaces of corresponding position (different rotation angles). (<b>a</b>) Diagram of the difference in height curve for rotation of 0.5° up and down. (<b>b</b>) Diagram of the difference in height curve for rotation of 1° up and down. (<b>c</b>) Diagram of the difference in height curve for rotation of 1.5° up and down. (<b>d</b>) Diagram of the difference in height curve for rotation of 2° up and down. (X: Length (mm) and Y: Height (mm)).</p> Full article ">Figure 9 Cont.
<p>The difference between the upper and lower fracture surfaces of corresponding position (different rotation angles). (<b>a</b>) Diagram of the difference in height curve for rotation of 0.5° up and down. (<b>b</b>) Diagram of the difference in height curve for rotation of 1° up and down. (<b>c</b>) Diagram of the difference in height curve for rotation of 1.5° up and down. (<b>d</b>) Diagram of the difference in height curve for rotation of 2° up and down. (X: Length (mm) and Y: Height (mm)).</p> Full article ">Figure 10
<p>Inversion results and comparison of fracture processes. (<b>a</b>) Initial stage inversion. (<b>b</b>) Initial stage testing. (<b>c</b>) Enhancement stage inversion. (<b>d</b>) Strengthening phase testing. (<b>e</b>) Fault stage inversion. (<b>f</b>) Fracture stage test. (X: Length (mm) and Y: Width (mm)).</p> Full article ">Figure 10 Cont.
<p>Inversion results and comparison of fracture processes. (<b>a</b>) Initial stage inversion. (<b>b</b>) Initial stage testing. (<b>c</b>) Enhancement stage inversion. (<b>d</b>) Strengthening phase testing. (<b>e</b>) Fault stage inversion. (<b>f</b>) Fracture stage test. (X: Length (mm) and Y: Width (mm)).</p> Full article ">Figure 11
<p>Assumption of rectangular bars for uniaxial tensile specimens. (<b>a</b>) Three-dimensional view of rectangular pole. (<b>b</b>) Top view of rectangular pole.</p> Full article ">Figure 12
<p>Deformation of rectangular rod. (<b>a</b>) Fracture situation of rectangular rod. (<b>b</b>) Changes in stress path.</p> Full article ">Figure 13
<p>Time difference of the specimen. (<b>a</b>) V<sub>n−1</sub>time. (<b>b</b>) V<sub>n</sub>time. (X: Length (mm) and Y: Width (mm)).</p> Full article ">Figure 14
<p>Comparison diagram of external load measurement results.</p> Full article ">
14 pages, 3932 KiB  
Article
Melamine-Modified Graphene Oxide as a Corrosion Resistance Enhancing Additive for Waterborne Epoxy Resin Coatings
by Xin Li, Dongsheng Li, Jie Chen, Dongxia Huo, Xin Gao, Junhui Dong, Yue Yin, Jun Liu and Ding Nan
Coatings 2024, 14(4), 488; https://doi.org/10.3390/coatings14040488 - 16 Apr 2024
Cited by 3 | Viewed by 1588
Abstract
Waterborne epoxy resin (WEP) coatings are widely used in various fields due to their environmentally friendly properties, yet their corrosion resistance and shielding properties demand further refinement. In this work, melamine-modified graphene oxide (MGO) was synthesized using surface covalent functionalization, and a novel [...] Read more.
Waterborne epoxy resin (WEP) coatings are widely used in various fields due to their environmentally friendly properties, yet their corrosion resistance and shielding properties demand further refinement. In this work, melamine-modified graphene oxide (MGO) was synthesized using surface covalent functionalization, and a novel waterborne epoxy/modified graphene oxide coating (WEP/MGO) was prepared. The optimal modification effect was obtained by exploring different proportions of melamine, which led to significant improvements in the corrosion resistance of WEP. Furthermore, the corrosion protection efficiency of WEP/MGO coatings was systematically evaluated by examining the impact of different additions of MGO. The impedance modulus at the lowest frequency was increased from 3.77 × 108 Ω·cm2 of WEP to 2.85 × 109 Ω·cm2 after immersion in 3.5% NaCl for 48 h, when the addition of MGO was 0.1 wt.%. And the corrosion expansion at both the scratch and corrosion spot frequencies of the WEP-coated samples displayed a remarkable attenuation following exposure to salt spray for 300 h. The corrosion resistance and barrier properties of WEP coatings have been considerably enhanced. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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<p>Schematic diagram of the preparation process for MGO and WEP/MGO coatings.</p> Full article ">Figure 2
<p>FT-IR spectra (<b>a</b>), Raman spectra (<b>b</b>), and XRD spectra (<b>c</b>) of GO and MGO.</p> Full article ">Figure 3
<p>SEM images of GO (<b>a</b>) and MGO (<b>b</b>). TEM images of GO (<b>c</b>) and MGO (<b>d</b>).</p> Full article ">Figure 4
<p>Nyquist plots (<b>a</b>), equivalent electrical circuits (<b>b</b>), and Bode diagrams (<b>c</b>,<b>d</b>) of WEP and WEP/MGO coating samples (immersion in 3.5% NaCl for 48 h).</p> Full article ">Figure 5
<p>Tafel polarization curves of WEP and WEP/MGO coatings immersed in a 3.5% NaCl solution for 48 h.</p> Full article ">Figure 6
<p>Images of WEP and WEP/MGO coating samples after a salt spray test for 300 h (scale bar: 1 cm). (<b>a</b>) WEP, (<b>b</b>) WEP/MGO-0.05, (<b>c</b>) WEP/MGO-0.1, (<b>d</b>) WEP/MGO-0.2, and (<b>e</b>) WEP/MGO-0.3.</p> Full article ">Figure 7
<p>Pull-off adhesion results of coated Q235 steel substrates.</p> Full article ">Figure 8
<p>Schematic diagram of the mechanism of corrosion resistance of coated samples.</p> Full article ">
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