The synthesis of n-SnO2/p-CuFe2O4 to degrade toxic methylene blue dye under natural sunlight and ... more The synthesis of n-SnO2/p-CuFe2O4 to degrade toxic methylene blue dye under natural sunlight and its mechanism.
School of Advanced Sciences, VIT University, Vellore-632 014, Tamilnadu, India E-mail : ssasikuma... more School of Advanced Sciences, VIT University, Vellore-632 014, Tamilnadu, India E-mail : ssasikumar@vit.ac.in In this study, we have prepared bioactive sodium calcium silicate (<strong>SCS</strong>) powders from sodium carbonate, calcium nitrate, tetraethyl orthosilicate (<strong>TEOS</strong>) by sol-gel combustion method using citric acid as a fuel. Phase formation of the synthesized <strong>SCS</strong> powders was characterized by powder X-ray diffraction (<strong>XRD</strong>). Composites were prepared by adding different ratios of sodium calcium silicate powder to chitosan and their <em>in vitro</em> bioactivity was analyzed by immersing the composites in simulated body fluid (<strong>SBF</strong>) solution. Results show that more chitosan contain composite shows greater bioactivity when compared to the composites contains lesser chitosan. Estimation of calcium ion concentration in the <strong>SBF<...
Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powde... more Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powders using various fuels. Citric acid, succinic acid, tartaric acid, sucrose, urea, glycine, and L-alanine were used as fuels. Influence of calcination temperature on the phase evolution was investigated. Prepared monticellite powders were characterized using powder-XRD, FT-IR, and DLS techniques. XRD pattern reveals that the L-alanine is a suitable fuel among all the fuels studied and confirms the formation of pure monticellite. FT-IR spectra confirm the presence of characteristic functional groups associated with monticellite. DLS measurements show the particle size of the monticellite powders. Finally, Apatite formation ability studies were carried out by immersing the monticellite and monticellite-polymer (chitosan/chitin) composites in the SBF solution. Pure monticellite shows higher bioactivity than the composites and its surface analysis (SEM and EDS) reveals the deposition of spherical hydroxyapatite particles.
Abstract In the present study, controllable microwave sintering was applied to prepare partially ... more Abstract In the present study, controllable microwave sintering was applied to prepare partially stabilised zirconia ceramics with enhanced phase composition and a more uniform structure. To reveal the phase interface properties and structural changes of PSZ ceramics during the microwave sintering process, XRD, FT-IR, Raman, and SEM characterisations were utilised. XRD analysis and Raman analysis demonstrated that the increase of sintering temperature promoted the martensite conversion. However, prolonging duration time was unconducive to the retention of the stable phase. Additionally, the FT-IR characteristic peak movement caused by the reversible phase martensite transformation was observed. Furthermore, SEM analysis found that microwave treatment improved the grain size and structure distribution of the as-received MgO-PSZ sample. This work constructed a controllable technical prototype of preparing PSZ ceramics via microwave sintering, which can provide a theoretical basis and experimental basis for further industrial production.
The three-dimensional (3D) mesoporous titanium dioxide (TiO2) was synthesized by microwave-assist... more The three-dimensional (3D) mesoporous titanium dioxide (TiO2) was synthesized by microwave-assisted hydrothermal method, using titanium sulfate as titanium source and urea to adjust pH value. Its structure and photocatalytic oxidation properties were studied. The results show that the TiO2 particles have a 3D mesoporous structure, uniform distribution and spherical shape, the average diameter is about 0.67[Formula: see text][Formula: see text]m. These properties provide strong light adsorption, high specific surface area, which increases the active site of the photocatalyst, porosity can also enhance the ability of the material to adsorb pollutants, thus has better stability. It was applied to photocatalytic degradation of 10[Formula: see text]mg/L rhodamine B (RhB) solution. After 80[Formula: see text]min of irradiation under 420[Formula: see text]nm ultraviolet (UV) light, the degradation rate of RhB reached more than 90%. In addition, it also provided an excellent photocatalytic ...
Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powde... more Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powders using various fuels. Citric acid, succinic acid, tartaric acid, sucrose, urea, glycine, and L-alanine were used as fuels. Influence of calcination temperature on the phase evolution was investigated. Prepared monticellite powders were characterized using powder-XRD, FT-IR, and DLS techniques. XRD pattern reveals that the L-alanine is a suitable fuel among all the fuels studied and confirms the formation of pure monticellite. FT-IR spectra confirm the presence of characteristic functional groups associated with monticellite. DLS measurements show the particle size of the monticellite powders. Finally, Apatite formation ability studies were carried out by immersing the monticellite and monticellite-polymer (chitosan/chitin) composites in the SBF solution. Pure monticellite shows higher bioactivity than the composites and its surface analysis (SEM and EDS) reveals the deposition of spherical hydroxyapatite particles.
The use of Pb/Sn/Al composite anode materials has been limited due to the thermodynamic immiscibi... more The use of Pb/Sn/Al composite anode materials has been limited due to the thermodynamic immiscibility between Pb and Al sheets during the welding process.
Vanadium slag contains high contents of vanadium and chromium with complex and dense structures, ... more Vanadium slag contains high contents of vanadium and chromium with complex and dense structures, hence microwave heating instead of conventional methods is expected to destroy the dense structure and further to improve the extraction rate of vanadium and chromium, and exploring its dielectric properties is the prerequisite work. Microwave absorption properties and thermal behavior of vanadium slag were investigated. Results indicated that vanadium slag endowed excellent microwave absorption properties, with minimum εr' value of 34.447 (F/M). Dielectric properties of vanadium slag varied with temperature, which changing trend was matched to the three stages of microwave heating characteristics identified by heating rates. Meanwhile, the changing process of dielectric properties also corresponded to the three processes of thermogravimetric characteristics: dehydration stage (30 °C-280 °C), oxidation decomposition of olivine phase and normal spinel phase (280 °C-650 °C), and oxidation decomposition of vanadium chromium spinel (650 °C-950 °C). Moreover, the maximum dielectric constant and highest microwave heating rate of vanadium slag both appeared at the temperature regime of 500 °C-550 °C, which was also the main temperature regime for oxidation decomposition of olivine phase and normal spinel phase in vanadium slag, demonstrating the appropriate process temperature for microwave heating technology to recycle vanadium slag.
Abstract Partially stabilized zirconia (PSZ) occupies an important application portion in ceramic... more Abstract Partially stabilized zirconia (PSZ) occupies an important application portion in ceramics materials and refractories materials. In this work, calcium oxide-partially stabilized zirconia (CaO-PSZ) ceramics were prepared from fused zirconia by microwave sintering, with its microstructure and stability properties characterized by XRD and SEM. Results indicated that the heating rate, cooling rate, quenching temperature and isothermal treatment time rendered different influence on the stability properties, which was mainly ascribed to the reversible martensitic transformation of zirconia ceramics. Additionally, a mixed-phase composed by cubic phase ZrO2 (c-ZrO2) and monoclinic phase ZrO2 (m-ZrO2) appeared after fused zirconia treated by microwave sintering at 1450 °C for 2 h, indicating the formation of CaO-PSZ ceramics, which the finding was consistent with the SEM and EDAX analysis. Meanwhile, CaO stabilizer precipitated behavior at the crystal boundary, with the formation of acicular grains and fine particles, further rendering a toughening effect to CaO-PSZ ceramics. This work can provide important theoretical and practical significance for applications of microwave sintering to prepare CaO-PSZ ceramics material, even extending further applications in functional materials and structural materials.
The synthesis of n-SnO2/p-CuFe2O4 to degrade toxic methylene blue dye under natural sunlight and ... more The synthesis of n-SnO2/p-CuFe2O4 to degrade toxic methylene blue dye under natural sunlight and its mechanism.
School of Advanced Sciences, VIT University, Vellore-632 014, Tamilnadu, India E-mail : ssasikuma... more School of Advanced Sciences, VIT University, Vellore-632 014, Tamilnadu, India E-mail : ssasikumar@vit.ac.in In this study, we have prepared bioactive sodium calcium silicate (<strong>SCS</strong>) powders from sodium carbonate, calcium nitrate, tetraethyl orthosilicate (<strong>TEOS</strong>) by sol-gel combustion method using citric acid as a fuel. Phase formation of the synthesized <strong>SCS</strong> powders was characterized by powder X-ray diffraction (<strong>XRD</strong>). Composites were prepared by adding different ratios of sodium calcium silicate powder to chitosan and their <em>in vitro</em> bioactivity was analyzed by immersing the composites in simulated body fluid (<strong>SBF</strong>) solution. Results show that more chitosan contain composite shows greater bioactivity when compared to the composites contains lesser chitosan. Estimation of calcium ion concentration in the <strong>SBF<...
Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powde... more Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powders using various fuels. Citric acid, succinic acid, tartaric acid, sucrose, urea, glycine, and L-alanine were used as fuels. Influence of calcination temperature on the phase evolution was investigated. Prepared monticellite powders were characterized using powder-XRD, FT-IR, and DLS techniques. XRD pattern reveals that the L-alanine is a suitable fuel among all the fuels studied and confirms the formation of pure monticellite. FT-IR spectra confirm the presence of characteristic functional groups associated with monticellite. DLS measurements show the particle size of the monticellite powders. Finally, Apatite formation ability studies were carried out by immersing the monticellite and monticellite-polymer (chitosan/chitin) composites in the SBF solution. Pure monticellite shows higher bioactivity than the composites and its surface analysis (SEM and EDS) reveals the deposition of spherical hydroxyapatite particles.
Abstract In the present study, controllable microwave sintering was applied to prepare partially ... more Abstract In the present study, controllable microwave sintering was applied to prepare partially stabilised zirconia ceramics with enhanced phase composition and a more uniform structure. To reveal the phase interface properties and structural changes of PSZ ceramics during the microwave sintering process, XRD, FT-IR, Raman, and SEM characterisations were utilised. XRD analysis and Raman analysis demonstrated that the increase of sintering temperature promoted the martensite conversion. However, prolonging duration time was unconducive to the retention of the stable phase. Additionally, the FT-IR characteristic peak movement caused by the reversible phase martensite transformation was observed. Furthermore, SEM analysis found that microwave treatment improved the grain size and structure distribution of the as-received MgO-PSZ sample. This work constructed a controllable technical prototype of preparing PSZ ceramics via microwave sintering, which can provide a theoretical basis and experimental basis for further industrial production.
The three-dimensional (3D) mesoporous titanium dioxide (TiO2) was synthesized by microwave-assist... more The three-dimensional (3D) mesoporous titanium dioxide (TiO2) was synthesized by microwave-assisted hydrothermal method, using titanium sulfate as titanium source and urea to adjust pH value. Its structure and photocatalytic oxidation properties were studied. The results show that the TiO2 particles have a 3D mesoporous structure, uniform distribution and spherical shape, the average diameter is about 0.67[Formula: see text][Formula: see text]m. These properties provide strong light adsorption, high specific surface area, which increases the active site of the photocatalyst, porosity can also enhance the ability of the material to adsorb pollutants, thus has better stability. It was applied to photocatalytic degradation of 10[Formula: see text]mg/L rhodamine B (RhB) solution. After 80[Formula: see text]min of irradiation under 420[Formula: see text]nm ultraviolet (UV) light, the degradation rate of RhB reached more than 90%. In addition, it also provided an excellent photocatalytic ...
Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powde... more Sol-gel combustion method was employed for the synthesis of monticellite (CaMgSiO4) ceramic powders using various fuels. Citric acid, succinic acid, tartaric acid, sucrose, urea, glycine, and L-alanine were used as fuels. Influence of calcination temperature on the phase evolution was investigated. Prepared monticellite powders were characterized using powder-XRD, FT-IR, and DLS techniques. XRD pattern reveals that the L-alanine is a suitable fuel among all the fuels studied and confirms the formation of pure monticellite. FT-IR spectra confirm the presence of characteristic functional groups associated with monticellite. DLS measurements show the particle size of the monticellite powders. Finally, Apatite formation ability studies were carried out by immersing the monticellite and monticellite-polymer (chitosan/chitin) composites in the SBF solution. Pure monticellite shows higher bioactivity than the composites and its surface analysis (SEM and EDS) reveals the deposition of spherical hydroxyapatite particles.
The use of Pb/Sn/Al composite anode materials has been limited due to the thermodynamic immiscibi... more The use of Pb/Sn/Al composite anode materials has been limited due to the thermodynamic immiscibility between Pb and Al sheets during the welding process.
Vanadium slag contains high contents of vanadium and chromium with complex and dense structures, ... more Vanadium slag contains high contents of vanadium and chromium with complex and dense structures, hence microwave heating instead of conventional methods is expected to destroy the dense structure and further to improve the extraction rate of vanadium and chromium, and exploring its dielectric properties is the prerequisite work. Microwave absorption properties and thermal behavior of vanadium slag were investigated. Results indicated that vanadium slag endowed excellent microwave absorption properties, with minimum εr' value of 34.447 (F/M). Dielectric properties of vanadium slag varied with temperature, which changing trend was matched to the three stages of microwave heating characteristics identified by heating rates. Meanwhile, the changing process of dielectric properties also corresponded to the three processes of thermogravimetric characteristics: dehydration stage (30 °C-280 °C), oxidation decomposition of olivine phase and normal spinel phase (280 °C-650 °C), and oxidation decomposition of vanadium chromium spinel (650 °C-950 °C). Moreover, the maximum dielectric constant and highest microwave heating rate of vanadium slag both appeared at the temperature regime of 500 °C-550 °C, which was also the main temperature regime for oxidation decomposition of olivine phase and normal spinel phase in vanadium slag, demonstrating the appropriate process temperature for microwave heating technology to recycle vanadium slag.
Abstract Partially stabilized zirconia (PSZ) occupies an important application portion in ceramic... more Abstract Partially stabilized zirconia (PSZ) occupies an important application portion in ceramics materials and refractories materials. In this work, calcium oxide-partially stabilized zirconia (CaO-PSZ) ceramics were prepared from fused zirconia by microwave sintering, with its microstructure and stability properties characterized by XRD and SEM. Results indicated that the heating rate, cooling rate, quenching temperature and isothermal treatment time rendered different influence on the stability properties, which was mainly ascribed to the reversible martensitic transformation of zirconia ceramics. Additionally, a mixed-phase composed by cubic phase ZrO2 (c-ZrO2) and monoclinic phase ZrO2 (m-ZrO2) appeared after fused zirconia treated by microwave sintering at 1450 °C for 2 h, indicating the formation of CaO-PSZ ceramics, which the finding was consistent with the SEM and EDAX analysis. Meanwhile, CaO stabilizer precipitated behavior at the crystal boundary, with the formation of acicular grains and fine particles, further rendering a toughening effect to CaO-PSZ ceramics. This work can provide important theoretical and practical significance for applications of microwave sintering to prepare CaO-PSZ ceramics material, even extending further applications in functional materials and structural materials.
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Papers by Sivasankar Koppala