The Experts below are selected from a list of 1929 Experts worldwide ranked by ideXlab platform
Ralf Riedel - One of the best experts on this subject based on the ideXlab platform.
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Corrosion behavior of silicon oxycarbide-based Ceramic Nanocomposites under hydrothermal
2020Co-Authors: Christoph Linck, Emanuel Ionescu, Benjamin Papendorf, Dagmar Galuskova, Ralf RiedelAbstract:Silicon oxycarbide-based Ceramic Nanocomposites (SiOC, SiZrOC and SiHfOC) were prepared by means of hot pressing techniques and their behavior upon hydrothermal corrosion at moderate temperatures (up to 2508C) was investigated. The results indicated linear corrosion behavior for all samples. The corrosion rates of the SiOC Ceramic materials were found to be remarkably lower than those of silicon carbide and comparable to values reported for silicon nitride. Furthermore, SiZrOC and SiHfOC were found to show improved resistance with respect to the non-modified SiOC, due to a unique synergistic effect: whereas zirconia/ hafnia act as \reinforcing" phases with respect to hydrothermal corrosion (due to their extremely low solubility in water under the testing conditions), the silicon oxycarbide matrix protects the MO2 phase from a corrosion-induced t-MO2 ? m-MO2 phase transformation. Consequently, the prepared silicon oxycarbide-based materials exhibit high potential for applications which require high resistance in corrosive media at moderate temperatures.
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single source precursor synthesis and high temperature evolution of novel mesoporous sivn o based Ceramic Nanocomposites
Journal of The European Ceramic Society, 2019Co-Authors: Cong Zhou, Ralf Riedel, Ryo Ishikawa, Yuichi Ikuhara, Emanuel IonescuAbstract:Abstract Mesoporous SiVN(O) Ceramics were prepared from a mixture consisting of VO(acac)2-modified perhydropolysilazane and polystyrene. The resulting amorphous single-phase SiVN(O) Ceramics remained amorphous in nitrogen atmosphere up to 1400 °C. The as-prepared materials consist of nanoscaled vanadium nitride dispersed in amorphous Si3N4; exposure to 1600 °C leads to the crystallization of VN and Si3N4. The specific surface area (SSA) and the pore size of the SiVN(O)-based Ceramics can be easily controlled by the temperature of thermal treatment and by the amount of polystyrene. The average pore size of the prepared SiVN(O) Ceramics was 4–10 nm and their largest SSA values, 642 and 506 m2/g, were achieved upon ammonolysis at 800 and 1000 °C, respectively. The combination of metal-modified single-source precursors and encapsulated porogens provides a convenient one-pot synthesis process to prepare mesoporous Ceramic Nanocomposites with controllable phase compositions and morphology.
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sic hfyta1 ycxn1 x c Ceramic Nanocomposites with hfyta1 ycxn1 x carbon core shell nanostructure and the influence of the carbon shell thickness on electrical properties
Journal of Materials Chemistry C, 2018Co-Authors: Zhaoju Yu, Emanuel Ionescu, Ralf Riedel, Claudia Fasel, Yan Lu, Yeping Xu, Koji Morita, Olivier Guillon, Gerd BuntkowskyAbstract:Dense monolithic SiC/HfyTa1−yCxN1−x/C (y = 0, 0.2 and 0.7) Ceramic Nanocomposites were prepared upon spark plasma sintering of amorphous SiHfTaC(N) Ceramic powders which were synthesized from single-source-precursors. The microstructural evolution of the Ceramic powders was investigated using elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). The results reveal that the powdered and dense monoliths of SiC/HfyTa1−yCxN1−x/C Ceramic Nanocomposites annealed at T ≥ 1700 °C and at 2200 °C, respectively, are characterized by the presence of a homogeneous dispersion of HfyTa1−yCxN1−x-carbon core–shell nanoparticles within a β-SiC matrix. Hf/Ta atomic ratios (or y values) of the in situ generated HfyTa1−yCxN1−x-carbon core–shell nanoparticles can be controlled precisely by molecular tailoring of the preCeramic precursors, which further tunes the thickness of the in situ formed carbon shell. Interestingly, with increasing the value y the thickness of the carbon shell increases, while the electrical conductivity of the dense monolithic SiC/HfyTa1−yCxN1−x/C (y = 0, 0.2 and 0.7) Nanocomposites significantly reduces. The unique HfyTa1−yCxN1−x-carbon core–shell nanostructure opens a new strategy towards tailoring the electrical conductivity of SiC/HfyTa1−yCxN1−x/C Nanocomposites for potential electromagnetic applications in harsh environments.
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preparation of dense sihf b cn based Ceramic Nanocomposites via rapid spark plasma sintering
Journal of The European Ceramic Society, 2017Co-Authors: Jia Yuan, Hans-joachim Kleebe, Ralf Riedel, Duan Li, Kurt E Johanns, Claudia Fasel, Karsten Durst, Zhijian Shen, Emanuel IonescuAbstract:Abstract Dense SiHf(B)CN-based Ceramic Nanocomposites were prepared by spark plasma sintering (SPS) using high heating rates (∼450 ° C/min.) and high pressures (≥100 MPa). The obtained Nanocomposites were investigated by X-ray diffraction, Raman spectroscopy and electron microscopy concerning their phase evolution and microstructure. The hardness and the elastic modulus of dense SiHfCN were found to be 26.8 and 367 GPa, respectively. Whereas the SiHfBCN samples exhibited a hardness of 24.6 GPa and an elastic modulus of 284 GPa. The investigation of the oxidation of the prepared dense Ceramic Nanocomposites at high temperature revealed that the parabolic oxidation rates of SiHfCN were comparable to those of ultra-high temperature Ceramics (UHTCs, e.g. HfC-20 vol% SiC); whereas the parabolic oxidation rates of SiHfBCN were several orders of magnitude lower than those. The results obtained within this study indicate the feasibility of SPS for rapid preparation of dense though nano-scaled Hf-containing Ceramic Nanocomposites that are promising candidates for high-temperature applications in harsh environments.
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single source precursor synthesis and electromagnetic properties of novel rgo sicn Ceramic Nanocomposites
Journal of Materials Chemistry C, 2017Co-Authors: Zhaoju Yu, Ralf Riedel, Ryo Ishikawa, Yuichi Ikuhara, Lingqi ChenAbstract:Single-source-precursors (SSPs) have been synthesized through chemical modification of poly(methylvinyl)silazane (HTT 1800) with graphene oxide (GO) via an amidation reaction catalyzed by ZnCl2. With the formation of an SSP, the restacking of GO was effectively prevented by the HTT 1800 grafted at the surface of GO. After pyrolysis of warm-pressed green bodies comprising the SSP, GO-HTT 1800, monolithic silicon carbonitride (SiCN) Ceramic Nanocomposites containing in situ thermally reduced graphene oxide (RGO), namely RGO–SiCN, were successfully prepared. The resultant RGO–SiCN Nanocomposites possess versatile electromagnetic (EM) properties ranging from EM absorbing to shielding behavior. With 2.5 wt% GO in the feed, the final RGO–SiCN nanocomposite exhibits an outstanding minimal reflection coefficient (RCmin) of −62.1 dB at 9.0 GHz, and the effective absorption bandwidth reaches 3.0 GHz with a sample thickness of 2.10 mm. With the same GO content, the resultant RGO–SiCN nanocomposite prepared by mechanical blending exhibits a far inferior RCmin of −8.2 dB. This finding strongly supports the advantage of the developed SSP route suitable for the fabrication of RGO–SiCN Nanocomposites with significantly enhanced EM properties. With 12.0 wt% GO content in the feed, the obtained RGO–SiCN nanocomposite reveals an excellent shielding effectiveness of 41.2 dB with a sample thickness of 2.00 mm.
Emanuel Ionescu - One of the best experts on this subject based on the ideXlab platform.
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Corrosion behavior of silicon oxycarbide-based Ceramic Nanocomposites under hydrothermal
2020Co-Authors: Christoph Linck, Emanuel Ionescu, Benjamin Papendorf, Dagmar Galuskova, Ralf RiedelAbstract:Silicon oxycarbide-based Ceramic Nanocomposites (SiOC, SiZrOC and SiHfOC) were prepared by means of hot pressing techniques and their behavior upon hydrothermal corrosion at moderate temperatures (up to 2508C) was investigated. The results indicated linear corrosion behavior for all samples. The corrosion rates of the SiOC Ceramic materials were found to be remarkably lower than those of silicon carbide and comparable to values reported for silicon nitride. Furthermore, SiZrOC and SiHfOC were found to show improved resistance with respect to the non-modified SiOC, due to a unique synergistic effect: whereas zirconia/ hafnia act as \reinforcing" phases with respect to hydrothermal corrosion (due to their extremely low solubility in water under the testing conditions), the silicon oxycarbide matrix protects the MO2 phase from a corrosion-induced t-MO2 ? m-MO2 phase transformation. Consequently, the prepared silicon oxycarbide-based materials exhibit high potential for applications which require high resistance in corrosive media at moderate temperatures.
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single source precursor synthesis and high temperature evolution of novel mesoporous sivn o based Ceramic Nanocomposites
Journal of The European Ceramic Society, 2019Co-Authors: Cong Zhou, Ralf Riedel, Ryo Ishikawa, Yuichi Ikuhara, Emanuel IonescuAbstract:Abstract Mesoporous SiVN(O) Ceramics were prepared from a mixture consisting of VO(acac)2-modified perhydropolysilazane and polystyrene. The resulting amorphous single-phase SiVN(O) Ceramics remained amorphous in nitrogen atmosphere up to 1400 °C. The as-prepared materials consist of nanoscaled vanadium nitride dispersed in amorphous Si3N4; exposure to 1600 °C leads to the crystallization of VN and Si3N4. The specific surface area (SSA) and the pore size of the SiVN(O)-based Ceramics can be easily controlled by the temperature of thermal treatment and by the amount of polystyrene. The average pore size of the prepared SiVN(O) Ceramics was 4–10 nm and their largest SSA values, 642 and 506 m2/g, were achieved upon ammonolysis at 800 and 1000 °C, respectively. The combination of metal-modified single-source precursors and encapsulated porogens provides a convenient one-pot synthesis process to prepare mesoporous Ceramic Nanocomposites with controllable phase compositions and morphology.
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sic hfyta1 ycxn1 x c Ceramic Nanocomposites with hfyta1 ycxn1 x carbon core shell nanostructure and the influence of the carbon shell thickness on electrical properties
Journal of Materials Chemistry C, 2018Co-Authors: Zhaoju Yu, Emanuel Ionescu, Ralf Riedel, Claudia Fasel, Yan Lu, Yeping Xu, Koji Morita, Olivier Guillon, Gerd BuntkowskyAbstract:Dense monolithic SiC/HfyTa1−yCxN1−x/C (y = 0, 0.2 and 0.7) Ceramic Nanocomposites were prepared upon spark plasma sintering of amorphous SiHfTaC(N) Ceramic powders which were synthesized from single-source-precursors. The microstructural evolution of the Ceramic powders was investigated using elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). The results reveal that the powdered and dense monoliths of SiC/HfyTa1−yCxN1−x/C Ceramic Nanocomposites annealed at T ≥ 1700 °C and at 2200 °C, respectively, are characterized by the presence of a homogeneous dispersion of HfyTa1−yCxN1−x-carbon core–shell nanoparticles within a β-SiC matrix. Hf/Ta atomic ratios (or y values) of the in situ generated HfyTa1−yCxN1−x-carbon core–shell nanoparticles can be controlled precisely by molecular tailoring of the preCeramic precursors, which further tunes the thickness of the in situ formed carbon shell. Interestingly, with increasing the value y the thickness of the carbon shell increases, while the electrical conductivity of the dense monolithic SiC/HfyTa1−yCxN1−x/C (y = 0, 0.2 and 0.7) Nanocomposites significantly reduces. The unique HfyTa1−yCxN1−x-carbon core–shell nanostructure opens a new strategy towards tailoring the electrical conductivity of SiC/HfyTa1−yCxN1−x/C Nanocomposites for potential electromagnetic applications in harsh environments.
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preparation of dense sihf b cn based Ceramic Nanocomposites via rapid spark plasma sintering
Journal of The European Ceramic Society, 2017Co-Authors: Jia Yuan, Hans-joachim Kleebe, Ralf Riedel, Duan Li, Kurt E Johanns, Claudia Fasel, Karsten Durst, Zhijian Shen, Emanuel IonescuAbstract:Abstract Dense SiHf(B)CN-based Ceramic Nanocomposites were prepared by spark plasma sintering (SPS) using high heating rates (∼450 ° C/min.) and high pressures (≥100 MPa). The obtained Nanocomposites were investigated by X-ray diffraction, Raman spectroscopy and electron microscopy concerning their phase evolution and microstructure. The hardness and the elastic modulus of dense SiHfCN were found to be 26.8 and 367 GPa, respectively. Whereas the SiHfBCN samples exhibited a hardness of 24.6 GPa and an elastic modulus of 284 GPa. The investigation of the oxidation of the prepared dense Ceramic Nanocomposites at high temperature revealed that the parabolic oxidation rates of SiHfCN were comparable to those of ultra-high temperature Ceramics (UHTCs, e.g. HfC-20 vol% SiC); whereas the parabolic oxidation rates of SiHfBCN were several orders of magnitude lower than those. The results obtained within this study indicate the feasibility of SPS for rapid preparation of dense though nano-scaled Hf-containing Ceramic Nanocomposites that are promising candidates for high-temperature applications in harsh environments.
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single source precursor synthesis of novel v8c7 sic o based Ceramic Nanocomposites
Journal of The European Ceramic Society, 2016Co-Authors: Sarabjeet Kaur, Emanuel Ionescu, Hans-joachim Kleebe, Claudia Fasel, Gennady Cherkashinin, Ralf RiedelAbstract:In the present work, novel V8C7/SiC(O) Ceramic Nanocomposites were synthesized upon thermal transformation of a polymer-derived single-source-precursor, which was obtained by the chemical modification of a polycarbosilane with vanadyl acetylacetonate. High-temperature treatment of the precursor in argon atmosphere first leads to an amorphous SiVOC single-phase Ceramic which subsequently undergoes phase-separation, crystallization and finally converts into V8C7/SiC(O) Ceramic Nanocomposites. Interestingly, the high-temperature stability of V8C7/SiC(O) was shown to strongly depend on the oxygen content present either in the SiC(O) matrix or in the atmosphere during the annealing process. Thus, larger oxygen contents induce a conversion of the V8C7 phase into V5Si3. The specific surface area (SSA) of the obtained nanocomposite powders depends on the processing temperature: The SSA decreases from 64 to 4 m2/g as the pyrolysis temperature increases from 600 to 1300 °C, respectively. Whereas it increases again to ca. 50 m2/g as the sample is exposed to 1700 °C (6 h annealing), due to the evolution of CO. Preliminary results of the catalytic activity of the V8C7/SiC(O)-based materials show that they are active for the decomposition of the ammonia. The maximum ammonia conversion efficiency was found to be 35% at around 650 °C, which is higher than that of the pure vanadium carbide reported in the literature (ca. 13%).
Hans-joachim Kleebe - One of the best experts on this subject based on the ideXlab platform.
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preparation of dense sihf b cn based Ceramic Nanocomposites via rapid spark plasma sintering
Journal of The European Ceramic Society, 2017Co-Authors: Jia Yuan, Hans-joachim Kleebe, Ralf Riedel, Duan Li, Kurt E Johanns, Claudia Fasel, Karsten Durst, Zhijian Shen, Emanuel IonescuAbstract:Abstract Dense SiHf(B)CN-based Ceramic Nanocomposites were prepared by spark plasma sintering (SPS) using high heating rates (∼450 ° C/min.) and high pressures (≥100 MPa). The obtained Nanocomposites were investigated by X-ray diffraction, Raman spectroscopy and electron microscopy concerning their phase evolution and microstructure. The hardness and the elastic modulus of dense SiHfCN were found to be 26.8 and 367 GPa, respectively. Whereas the SiHfBCN samples exhibited a hardness of 24.6 GPa and an elastic modulus of 284 GPa. The investigation of the oxidation of the prepared dense Ceramic Nanocomposites at high temperature revealed that the parabolic oxidation rates of SiHfCN were comparable to those of ultra-high temperature Ceramics (UHTCs, e.g. HfC-20 vol% SiC); whereas the parabolic oxidation rates of SiHfBCN were several orders of magnitude lower than those. The results obtained within this study indicate the feasibility of SPS for rapid preparation of dense though nano-scaled Hf-containing Ceramic Nanocomposites that are promising candidates for high-temperature applications in harsh environments.
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single source precursor synthesis of novel v8c7 sic o based Ceramic Nanocomposites
Journal of The European Ceramic Society, 2016Co-Authors: Sarabjeet Kaur, Emanuel Ionescu, Hans-joachim Kleebe, Claudia Fasel, Gennady Cherkashinin, Ralf RiedelAbstract:In the present work, novel V8C7/SiC(O) Ceramic Nanocomposites were synthesized upon thermal transformation of a polymer-derived single-source-precursor, which was obtained by the chemical modification of a polycarbosilane with vanadyl acetylacetonate. High-temperature treatment of the precursor in argon atmosphere first leads to an amorphous SiVOC single-phase Ceramic which subsequently undergoes phase-separation, crystallization and finally converts into V8C7/SiC(O) Ceramic Nanocomposites. Interestingly, the high-temperature stability of V8C7/SiC(O) was shown to strongly depend on the oxygen content present either in the SiC(O) matrix or in the atmosphere during the annealing process. Thus, larger oxygen contents induce a conversion of the V8C7 phase into V5Si3. The specific surface area (SSA) of the obtained nanocomposite powders depends on the processing temperature: The SSA decreases from 64 to 4 m2/g as the pyrolysis temperature increases from 600 to 1300 °C, respectively. Whereas it increases again to ca. 50 m2/g as the sample is exposed to 1700 °C (6 h annealing), due to the evolution of CO. Preliminary results of the catalytic activity of the V8C7/SiC(O)-based materials show that they are active for the decomposition of the ammonia. The maximum ammonia conversion efficiency was found to be 35% at around 650 °C, which is higher than that of the pure vanadium carbide reported in the literature (ca. 13%).
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Single-source-precursor synthesis of novel V8C7/SiC(O)-based Ceramic Nanocomposites
Journal of The European Ceramic Society, 2016Co-Authors: Sarabjeet Kaur, Emanuel Ionescu, Hans-joachim Kleebe, Claudia Fasel, Gennady Cherkashinin, Ralf RiedelAbstract:In the present work, novel V8C7/SiC(O) Ceramic Nanocomposites were synthesized upon thermal transformation of a polymer-derived single-source-precursor, which was obtained by the chemical modification of a polycarbosilane with vanadyl acetylacetonate. High-temperature treatment of the precursor in argon atmosphere first leads to an amorphous SiVOC single-phase Ceramic which subsequently undergoes phase-separation, crystallization and finally converts into V8C7/SiC(O) Ceramic Nanocomposites. Interestingly, the high-temperature stability of V8C7/SiC(O) was shown to strongly depend on the oxygen content present either in the SiC(O) matrix or in the atmosphere during the annealing process. Thus, larger oxygen contents induce a conversion of the V8C7 phase into V5Si3. The specific surface area (SSA) of the obtained nanocomposite powders depends on the processing temperature: The SSA decreases from 64 to 4 m2/g as the pyrolysis temperature increases from 600 to 1300 °C, respectively. Whereas it increases again to ca. 50 m2/g as the sample is exposed to 1700 °C (6 h annealing), due to the evolution of CO. Preliminary results of the catalytic activity of the V8C7/SiC(O)-based materials show that they are active for the decomposition of the ammonia. The maximum ammonia conversion efficiency was found to be 35% at around 650 °C, which is higher than that of the pure vanadium carbide reported in the literature (ca. 13%).
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Carbon Mobility in SiOC/HfO2 Ceramic Nanocomposites
Journal of the American Ceramic Society, 2013Co-Authors: Katharina Nonnenmacher, Emanuel Ionescu, Hans-joachim Kleebe, Jochen Rohrer, Ralf RiedelAbstract:Silicon oxycarbide/hafnia (SiOC/HfO2) Ceramic Nanocomposites were studied by transmission electron microscopy (TEM) upon isothermal annealing at 1300°C for 1–200 h. TEM investigations in conjunction with energy-dispersive X-ray spectroscopy (EDS) analysis revealed a pronounced reduction in the local carbon content in close proximity to internal surfaces. Such small microcracks are a consequence of the polymer-to-Ceramic transition and, hence, are commonly formed upon thermal annealing. The profiles of the carbon content between surface and bulk were analyzed employing error functions to yield carbon diffusivities.
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high temperature creep behavior of dense sioc based Ceramic Nanocomposites microstructural and phase composition effects
Journal of the American Ceramic Society, 2013Co-Authors: Benjamin Papendorf, Emanuel Ionescu, Hans-joachim Kleebe, Katharina Nonnenmacher, Christoph Linck, Olivier Guillon, Ralf RiedelAbstract:In this work, dense monolithic polymer-derived Ceramic Nanocomposites (SiOC, SiZrOC, and SiHfOC) were synthesized via hot-pressing techniques and were evaluated with respect to their compression creep behavior at temperatures beyond 1000°C. The creep rates, stress exponents as well as activation energies were determined. The high-temperature creep in all materials has been shown to rely on viscous flow. In the quaternary materials (i.e., SiZrOC and SiHfOC), higher creep rates and activation energies were determined as compared to those of monolithic SiOC. The increase in the creep rates upon modification of SiOC with Zr/Hf relies on the significant decrease in the volume fraction of segregated carbon; whereas the increase of the activation energies corresponds to an increase of the size of the silica nanodomains upon Zr/Hf modification. Within this context, a model is proposed, which correlates the phase composition as well as network architecture of the investigated samples with their creep behavior and agrees well with the experimentally determined data.
Basudeb Karmakar - One of the best experts on this subject based on the ideXlab platform.
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fabrication and enhanced photoluminescence properties of sm3 doped zno al2o3 b2o3 sio2 glass derived willemite glass Ceramic Nanocomposites
Optical Materials, 2014Co-Authors: Anal Tarafder, Atiar Rahaman Molla, S Mukhopadhyay, Basudeb KarmakarAbstract:Abstract The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were prepared from melt-quench derived ZnO–Al2O3–B2O3–SiO2 (ZABS) precursor glass by an isothermal heat-treatment process. The generation of willemite crystal phase, size and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 80–120 nm. The decreased refractive index with increase in heat-treatment time attributed to partial replacement of ZnO4 units of willemite nanocrystals by AlO4 units and simultaneous generation of vacancies in the Zn-site. Fourier transform infrared (FTIR) reflection spectroscopy exhibits the structural evolution of willemite glass–Ceramics. The photoluminescence spectra of Sm3+ ions exhibit emission transitions of 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, 11/2) and its excitation spectra shows an intense absorption band at 402 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 14-fold with crystallization into willemite.
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Fabrication and enhanced photoluminescence properties of Sm3+-doped ZnO–Al2O3–B2O3–SiO2 glass derived willemite glass–Ceramic Nanocomposites
Optical Materials, 2014Co-Authors: Anal Tarafder, Atiar Rahaman Molla, S Mukhopadhyay, Basudeb KarmakarAbstract:Abstract The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were prepared from melt-quench derived ZnO–Al2O3–B2O3–SiO2 (ZABS) precursor glass by an isothermal heat-treatment process. The generation of willemite crystal phase, size and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 80–120 nm. The decreased refractive index with increase in heat-treatment time attributed to partial replacement of ZnO4 units of willemite nanocrystals by AlO4 units and simultaneous generation of vacancies in the Zn-site. Fourier transform infrared (FTIR) reflection spectroscopy exhibits the structural evolution of willemite glass–Ceramics. The photoluminescence spectra of Sm3+ ions exhibit emission transitions of 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, 11/2) and its excitation spectra shows an intense absorption band at 402 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 14-fold with crystallization into willemite.
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thermal structural and enhanced photoluminescence properties of eu3 doped transparent willemite glass Ceramic Nanocomposites
Journal of the American Ceramic Society, 2013Co-Authors: Anal Tarafder, Atiar Rahaman Molla, Basudeb KarmakarAbstract:The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt-quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat-treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass-Ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 17-fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–Ceramic Nanocomposites are expected to find potential applications in solid-state red lasers, phosphors, and optical display systems.
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Thermal, Structural, and Enhanced Photoluminescence Properties of Eu3+‐doped Transparent Willemite Glass–Ceramic Nanocomposites
Journal of the American Ceramic Society, 2013Co-Authors: Anal Tarafder, Atiar Rahaman Molla, Basudeb KarmakarAbstract:The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt-quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat-treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass-Ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 17-fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–Ceramic Nanocomposites are expected to find potential applications in solid-state red lasers, phosphors, and optical display systems.
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Processing and Properties of Eu3+:LiTaO3 TransparentGlass–Ceramic Nanocomposites
Journal of the American Ceramic Society, 2009Co-Authors: Anal Tarafder, Kalyandurg Annapurna, Reenamoni Saikia Chaliha, V.s. Tiwari, Pradeep Kumar Gupta, Basudeb KarmakarAbstract:We report here the processing and properties of transparent glass and glass-Ceramic Nanocomposites in the Li 2 O―Ta 2 O 5 ―SiO 2 ― Al 2 O 3 system in the presence of Eu 2 O 3 as luminescent probe. The formation of the LiTa0 3 crystal phase, the crystallite size, and the morphology with the progression of heat treatment have been examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transformed infrared reflectance spectroscopy measurements. The crystallite sizes obtained from XRD and TEM are found to increase with heat-treatment time and vary in the range of 2-20 nm. The measured phototuminescence spectra exhibit emission transitions of 5 D 0,1 → F j (j = 0, 1, 2, 3, and 4) of Eu 3+ ions. From the nature of the emission transitions, the site symmetry in the vicinity of Eu 3+ ions has been found to be near C 3v in the glass-Ceramic Nanocomposites. An inverse correlation has been observed between the asymmetric ratio (I ED /I MD ) of Eu 3+ ions and the dielectric constant (e r ), with an increase in the heat-treatment time of glass, which is caused by the dipole―dipole interaction.
Anal Tarafder - One of the best experts on this subject based on the ideXlab platform.
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fabrication and enhanced photoluminescence properties of sm3 doped zno al2o3 b2o3 sio2 glass derived willemite glass Ceramic Nanocomposites
Optical Materials, 2014Co-Authors: Anal Tarafder, Atiar Rahaman Molla, S Mukhopadhyay, Basudeb KarmakarAbstract:Abstract The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were prepared from melt-quench derived ZnO–Al2O3–B2O3–SiO2 (ZABS) precursor glass by an isothermal heat-treatment process. The generation of willemite crystal phase, size and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 80–120 nm. The decreased refractive index with increase in heat-treatment time attributed to partial replacement of ZnO4 units of willemite nanocrystals by AlO4 units and simultaneous generation of vacancies in the Zn-site. Fourier transform infrared (FTIR) reflection spectroscopy exhibits the structural evolution of willemite glass–Ceramics. The photoluminescence spectra of Sm3+ ions exhibit emission transitions of 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, 11/2) and its excitation spectra shows an intense absorption band at 402 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 14-fold with crystallization into willemite.
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Fabrication and enhanced photoluminescence properties of Sm3+-doped ZnO–Al2O3–B2O3–SiO2 glass derived willemite glass–Ceramic Nanocomposites
Optical Materials, 2014Co-Authors: Anal Tarafder, Atiar Rahaman Molla, S Mukhopadhyay, Basudeb KarmakarAbstract:Abstract The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were prepared from melt-quench derived ZnO–Al2O3–B2O3–SiO2 (ZABS) precursor glass by an isothermal heat-treatment process. The generation of willemite crystal phase, size and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 80–120 nm. The decreased refractive index with increase in heat-treatment time attributed to partial replacement of ZnO4 units of willemite nanocrystals by AlO4 units and simultaneous generation of vacancies in the Zn-site. Fourier transform infrared (FTIR) reflection spectroscopy exhibits the structural evolution of willemite glass–Ceramics. The photoluminescence spectra of Sm3+ ions exhibit emission transitions of 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, 11/2) and its excitation spectra shows an intense absorption band at 402 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 14-fold with crystallization into willemite.
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thermal structural and enhanced photoluminescence properties of eu3 doped transparent willemite glass Ceramic Nanocomposites
Journal of the American Ceramic Society, 2013Co-Authors: Anal Tarafder, Atiar Rahaman Molla, Basudeb KarmakarAbstract:The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt-quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat-treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass-Ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 17-fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–Ceramic Nanocomposites are expected to find potential applications in solid-state red lasers, phosphors, and optical display systems.
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Thermal, Structural, and Enhanced Photoluminescence Properties of Eu3+‐doped Transparent Willemite Glass–Ceramic Nanocomposites
Journal of the American Ceramic Society, 2013Co-Authors: Anal Tarafder, Atiar Rahaman Molla, Basudeb KarmakarAbstract:The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt-quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–Ceramic Nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat-treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass-Ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–Ceramic Nanocomposites is enhanced up to 17-fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–Ceramic Nanocomposites are expected to find potential applications in solid-state red lasers, phosphors, and optical display systems.
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Processing and Properties of Eu3+:LiTaO3 TransparentGlass–Ceramic Nanocomposites
Journal of the American Ceramic Society, 2009Co-Authors: Anal Tarafder, Kalyandurg Annapurna, Reenamoni Saikia Chaliha, V.s. Tiwari, Pradeep Kumar Gupta, Basudeb KarmakarAbstract:We report here the processing and properties of transparent glass and glass-Ceramic Nanocomposites in the Li 2 O―Ta 2 O 5 ―SiO 2 ― Al 2 O 3 system in the presence of Eu 2 O 3 as luminescent probe. The formation of the LiTa0 3 crystal phase, the crystallite size, and the morphology with the progression of heat treatment have been examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transformed infrared reflectance spectroscopy measurements. The crystallite sizes obtained from XRD and TEM are found to increase with heat-treatment time and vary in the range of 2-20 nm. The measured phototuminescence spectra exhibit emission transitions of 5 D 0,1 → F j (j = 0, 1, 2, 3, and 4) of Eu 3+ ions. From the nature of the emission transitions, the site symmetry in the vicinity of Eu 3+ ions has been found to be near C 3v in the glass-Ceramic Nanocomposites. An inverse correlation has been observed between the asymmetric ratio (I ED /I MD ) of Eu 3+ ions and the dielectric constant (e r ), with an increase in the heat-treatment time of glass, which is caused by the dipole―dipole interaction.