The raw diatomaceous earth from the vicinity of Bitola (North Macedonia) showed low bulk density ... more The raw diatomaceous earth from the vicinity of Bitola (North Macedonia) showed low bulk density (0.61-0.69 g/cm3), high-water absorption (75-81%) and porosity (66- 72%). The chemical composition was determined with ICP-MS, revealing the following results for the diatomaceous earth: SiO2 (63.69 wt%), Al2O3 (11.79 wt%), Fe2O3 (5.95 wt%), MnO (0.15 wt%), TiO2 (0.65 wt%), CaO (1.51 wt%), MgO (2.24 wt%), P2O5 (0.13 wt%), K2O (1.64 wt%), Na2O (0.93 wt%), LOI (11.21 wt%). XRPD data of the examined sample of clayey diatomite mainly depicted crystalline behavior with a small presence of amorphous phase. The crystalline mineral phases mainly comprise: silica (quartz), feldspars (plagioclase), mica (muscovite), chlorites and dolomite. SEM and TEM results show cased presence of micro- and nanostructures with pores ranging from 250 to 600 nm. The clayey diatomite was sintered at three temperatures (900, 1000 and 1100?C) for a period of 1 h. XRPD of the sintered samples at 1100?C showed certain ...
The structural transformations and magnetic property changes of the Nd16.2FebalCo9.9Ga0.5B7.5 (SG... more The structural transformations and magnetic property changes of the Nd16.2FebalCo9.9Ga0.5B7.5 (SG1, SG2) and Nd15.0FebalGa2.0B7.3 (SG3) nanocomposite alloys obtained by melt spinning in the as-quenched state and after annealing at a temperature range of 560–650 °C for 30 min were studied. The methods used were X-ray diffraction analysis, magnetic property measurements, TEM studies, X-ray fluorescence analysis and Mössbauer spectroscopy. Amorphous phase and crystalline phase Nd2Fe14B (P42/mnm) were observed in the alloy after melt spinning. The content of the amorphous phase ranged from 20% to 50% and depended on the cooling rate. Annealing of the alloys resulted in amorphous phase crystallization into Nd2Fe14B and led to the increased coercivity of the alloys up to 1840 kA/m (23.1 kOe) at 600 °C annealing for 30 min. The alloy with the maximum coercivity had a grain size of the Nd2Fe14B phase ≈50–70 nm with an Nd-rich phase between grains.
The present article overviews the current state-of-the-art and future prospects for the use of di... more The present article overviews the current state-of-the-art and future prospects for the use of diatomaceous earth (DE) in the continuously expanding sector of energy science and technology.
Functionalization of silicon has become an interesting research topic due to the excellent combin... more Functionalization of silicon has become an interesting research topic due to the excellent combination of properties of functionalized Silicon that could be used in many applications, e.g. in energy conversion based on its good thermoelectric properties. One type of functionalized silicon is its nanoporous form that can be produced by subtractive or additive manufacturing at the nanoscale. However, due to the high cost, the search for cost efficient technologies is currently under way. One promising route is offered by Metallothermic Reduction Reaction (MRR) from silica. Here we report the characterization of nanoporous Silicon produced from diatomite earth via Magnesiothermic Reduction Reaction. The methods used include Raman Spectroscopy, Scanning Electron Microscopy and X-ray Diffraction. Index Terms — Nanoporous Silicon, Magnesiothermic reduction reaction, X-ray Diffraction, Diatomite, Calcination, Raman Spectroscopy
The powder characteristics of nanostructured silicon produced via Magnesiothermic Reduction React... more The powder characteristics of nanostructured silicon produced via Magnesiothermic Reduction Reaction (MRR) of raw (amorphous) and calcined (crystalline) diatomite powders were studied. Magnesiothermic reduction reaction of diatomaceous earth samples was carried out in an argon-filled electric furnace at 700 °C for 2.5 h. Both X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis of calcined diatomite powders confirmed the crystallization of opal to cristobalite and the preservation of the nano-scale morphology of natural diatomite after calcination at 1200 °C for 4 h. Raw and calcined diatomite after MRR contained product nanostructured silicon, unreacted silica, and by-product MgO. Silicon with nano-scale morphology was obtained after etching the reduced powder with 1.0 M HCl and 5% HF severally. Among the different grades of nanostructured Si produced via different routes, the one obtained from the diatomite powder calcined under argon flow showed nano-scale morp...
The present article overviews the current state-of-the-art and future prospects for the use of di... more The present article overviews the current state-of-the-art and future prospects for the use of diatomaceous earth (DE) in the continuously expanding sector of energy science and technology.
Abstract The pursuit of new nanotechnologies is driven by the demand for miniaturization, ubiquit... more Abstract The pursuit of new nanotechnologies is driven by the demand for miniaturization, ubiquitous computing, increasing connectivity and the Internet of Things (IoT) paradigm, the environmental agenda, and the confluence between microelectronics and biomedical fields. Of particular interest for the present overview are the capabilities of prokaryotic and eukaryotic microorganisms to fabricate numerous nanostructured self-copies from ecologically friendly and renewable raw materials offering new pathways for low energy consumption, smart nanofabrication at production rates that remain unattainable for today’s engineering technologies. The present discussion is focused on the use of stiff and strong nanostructured silica diatom frustules that is widely mooted in the literature in consideration of photonic, photovoltaic, plasmonic, and drug delivery applications. Chemical post-processing routes can be applied to synthesize and deposit nanostructures (Ag, Au, MnO2, ZnO etc.) using templates and substrates of diatomaceous earth and individual diatom frustules. In this concise overview we discuss the background knowledge, motivation and justification for the use of siliceous diatom frustules as a platform for smart nanofabrication, and attempt to anticipate future developments in this field.
Abstract Diatom algae are active and efficient photosynthesizing single cell organisms responsibl... more Abstract Diatom algae are active and efficient photosynthesizing single cell organisms responsible for a quarter of biomass and a quarter of oxygen release on the Earth surface. Diatoms form an enormously diverse class of microorganisms possessing stiff and strong, durable exoskeletons made from hydrated amorphous silica forming neat 3D nanostructures, and displaying hierarchical organization up to the scale of tens of micrometres. In our ongoing research into the structure and properties of diatoms we observed their colonization patterns on various surfaces, including polymers (PE, PP, PC and PETF) and silicon. This process can be guided by purposeful surface patterning to introduce pits, grooves, and ledges. Guided colonization opens the prospect of assembly and harvesting diatom frustules for applications in micro- and nano-electro-mechanical systems (MEMS and NEMS). Additionally, the wide range and specificity of diatoms opens the possibility of using them as tags and markers that are below the level of visibility by naked eye, but present specific spectroscopic fingerprints in visible light and UV ranges. Diatom ‘tags’ can also be read using high magnification imaging using Scanning Electron Microscopy (SEM). As a contributory guidance to morphological diversity of diatoms we present a mini-atlas of diatom in the form of high resolution SEM images.
Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a si... more Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a single crystalline silicon wafer via the magnesiothermic reduction reaction is reported. The formed porous coating of 6 µm overall thickness contains silicon as the majority phase along with minor traces of Mg, as evident from SEM-EDS and the Focused Ion Beam (FIB) analysis. Raman peaks of silicon at 519 cm−1 and 925 cm−1 were found in both the film and wafer substrate, and significant intensity variation was observed, consistent with the SEM observation of the directly formed silicon nanoflake layer. Microstructural analysis of the flakes reveals the presence of pores and cavities partially retained from the precursor diatomite powder. A considerable reduction in surface reflectivity was observed for the silicon nanoflakes, from 45% for silicon wafer to below 15%. The results open possibilities for producing nanostructured silicon with a vast range of functionalities.
The raw diatomaceous earth from the vicinity of Bitola (North Macedonia) showed low bulk density ... more The raw diatomaceous earth from the vicinity of Bitola (North Macedonia) showed low bulk density (0.61-0.69 g/cm3), high-water absorption (75-81%) and porosity (66- 72%). The chemical composition was determined with ICP-MS, revealing the following results for the diatomaceous earth: SiO2 (63.69 wt%), Al2O3 (11.79 wt%), Fe2O3 (5.95 wt%), MnO (0.15 wt%), TiO2 (0.65 wt%), CaO (1.51 wt%), MgO (2.24 wt%), P2O5 (0.13 wt%), K2O (1.64 wt%), Na2O (0.93 wt%), LOI (11.21 wt%). XRPD data of the examined sample of clayey diatomite mainly depicted crystalline behavior with a small presence of amorphous phase. The crystalline mineral phases mainly comprise: silica (quartz), feldspars (plagioclase), mica (muscovite), chlorites and dolomite. SEM and TEM results show cased presence of micro- and nanostructures with pores ranging from 250 to 600 nm. The clayey diatomite was sintered at three temperatures (900, 1000 and 1100?C) for a period of 1 h. XRPD of the sintered samples at 1100?C showed certain ...
The structural transformations and magnetic property changes of the Nd16.2FebalCo9.9Ga0.5B7.5 (SG... more The structural transformations and magnetic property changes of the Nd16.2FebalCo9.9Ga0.5B7.5 (SG1, SG2) and Nd15.0FebalGa2.0B7.3 (SG3) nanocomposite alloys obtained by melt spinning in the as-quenched state and after annealing at a temperature range of 560–650 °C for 30 min were studied. The methods used were X-ray diffraction analysis, magnetic property measurements, TEM studies, X-ray fluorescence analysis and Mössbauer spectroscopy. Amorphous phase and crystalline phase Nd2Fe14B (P42/mnm) were observed in the alloy after melt spinning. The content of the amorphous phase ranged from 20% to 50% and depended on the cooling rate. Annealing of the alloys resulted in amorphous phase crystallization into Nd2Fe14B and led to the increased coercivity of the alloys up to 1840 kA/m (23.1 kOe) at 600 °C annealing for 30 min. The alloy with the maximum coercivity had a grain size of the Nd2Fe14B phase ≈50–70 nm with an Nd-rich phase between grains.
The present article overviews the current state-of-the-art and future prospects for the use of di... more The present article overviews the current state-of-the-art and future prospects for the use of diatomaceous earth (DE) in the continuously expanding sector of energy science and technology.
Functionalization of silicon has become an interesting research topic due to the excellent combin... more Functionalization of silicon has become an interesting research topic due to the excellent combination of properties of functionalized Silicon that could be used in many applications, e.g. in energy conversion based on its good thermoelectric properties. One type of functionalized silicon is its nanoporous form that can be produced by subtractive or additive manufacturing at the nanoscale. However, due to the high cost, the search for cost efficient technologies is currently under way. One promising route is offered by Metallothermic Reduction Reaction (MRR) from silica. Here we report the characterization of nanoporous Silicon produced from diatomite earth via Magnesiothermic Reduction Reaction. The methods used include Raman Spectroscopy, Scanning Electron Microscopy and X-ray Diffraction. Index Terms — Nanoporous Silicon, Magnesiothermic reduction reaction, X-ray Diffraction, Diatomite, Calcination, Raman Spectroscopy
The powder characteristics of nanostructured silicon produced via Magnesiothermic Reduction React... more The powder characteristics of nanostructured silicon produced via Magnesiothermic Reduction Reaction (MRR) of raw (amorphous) and calcined (crystalline) diatomite powders were studied. Magnesiothermic reduction reaction of diatomaceous earth samples was carried out in an argon-filled electric furnace at 700 °C for 2.5 h. Both X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis of calcined diatomite powders confirmed the crystallization of opal to cristobalite and the preservation of the nano-scale morphology of natural diatomite after calcination at 1200 °C for 4 h. Raw and calcined diatomite after MRR contained product nanostructured silicon, unreacted silica, and by-product MgO. Silicon with nano-scale morphology was obtained after etching the reduced powder with 1.0 M HCl and 5% HF severally. Among the different grades of nanostructured Si produced via different routes, the one obtained from the diatomite powder calcined under argon flow showed nano-scale morp...
The present article overviews the current state-of-the-art and future prospects for the use of di... more The present article overviews the current state-of-the-art and future prospects for the use of diatomaceous earth (DE) in the continuously expanding sector of energy science and technology.
Abstract The pursuit of new nanotechnologies is driven by the demand for miniaturization, ubiquit... more Abstract The pursuit of new nanotechnologies is driven by the demand for miniaturization, ubiquitous computing, increasing connectivity and the Internet of Things (IoT) paradigm, the environmental agenda, and the confluence between microelectronics and biomedical fields. Of particular interest for the present overview are the capabilities of prokaryotic and eukaryotic microorganisms to fabricate numerous nanostructured self-copies from ecologically friendly and renewable raw materials offering new pathways for low energy consumption, smart nanofabrication at production rates that remain unattainable for today’s engineering technologies. The present discussion is focused on the use of stiff and strong nanostructured silica diatom frustules that is widely mooted in the literature in consideration of photonic, photovoltaic, plasmonic, and drug delivery applications. Chemical post-processing routes can be applied to synthesize and deposit nanostructures (Ag, Au, MnO2, ZnO etc.) using templates and substrates of diatomaceous earth and individual diatom frustules. In this concise overview we discuss the background knowledge, motivation and justification for the use of siliceous diatom frustules as a platform for smart nanofabrication, and attempt to anticipate future developments in this field.
Abstract Diatom algae are active and efficient photosynthesizing single cell organisms responsibl... more Abstract Diatom algae are active and efficient photosynthesizing single cell organisms responsible for a quarter of biomass and a quarter of oxygen release on the Earth surface. Diatoms form an enormously diverse class of microorganisms possessing stiff and strong, durable exoskeletons made from hydrated amorphous silica forming neat 3D nanostructures, and displaying hierarchical organization up to the scale of tens of micrometres. In our ongoing research into the structure and properties of diatoms we observed their colonization patterns on various surfaces, including polymers (PE, PP, PC and PETF) and silicon. This process can be guided by purposeful surface patterning to introduce pits, grooves, and ledges. Guided colonization opens the prospect of assembly and harvesting diatom frustules for applications in micro- and nano-electro-mechanical systems (MEMS and NEMS). Additionally, the wide range and specificity of diatoms opens the possibility of using them as tags and markers that are below the level of visibility by naked eye, but present specific spectroscopic fingerprints in visible light and UV ranges. Diatom ‘tags’ can also be read using high magnification imaging using Scanning Electron Microscopy (SEM). As a contributory guidance to morphological diversity of diatoms we present a mini-atlas of diatom in the form of high resolution SEM images.
Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a si... more Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a single crystalline silicon wafer via the magnesiothermic reduction reaction is reported. The formed porous coating of 6 µm overall thickness contains silicon as the majority phase along with minor traces of Mg, as evident from SEM-EDS and the Focused Ion Beam (FIB) analysis. Raman peaks of silicon at 519 cm−1 and 925 cm−1 were found in both the film and wafer substrate, and significant intensity variation was observed, consistent with the SEM observation of the directly formed silicon nanoflake layer. Microstructural analysis of the flakes reveals the presence of pores and cavities partially retained from the precursor diatomite powder. A considerable reduction in surface reflectivity was observed for the silicon nanoflakes, from 45% for silicon wafer to below 15%. The results open possibilities for producing nanostructured silicon with a vast range of functionalities.
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