Abstract Environmental deterioration and limited resources of hydrocarbons push the development o... more Abstract Environmental deterioration and limited resources of hydrocarbons push the development of alternative power sources. One of the most promising energy carriers is hydrogen. However, handling hydrogen is more hazardous than the use of hydrocarbons because it has a significantly wider flammable range. Thus the development of new sensors for preventing hydrogen leakage is the actual task of modern materials science and chemical engineering. In this work, the response of catalytic sensors to hydrogen with different catalysts of platinum group (Pt, Pd, Ir, Rh, Pt + Pd, Pt + Pd + Rh, Pt + Pd + Ir) in the pre-explosion concentration range is studied. Temperature dependencies of sensitivity are discussed. A hysteresis in sensor response is observed during the cycling of the supply voltage. This phenomenon can be explained by partial transformation of platinum group metal oxides into metallic phase at a temperature of more than 500 °C and reverse metal oxidation at temperatures less than 400 °C. It has been shown that the sensors with catalysts containing Ir and Rh demonstrate more preferable characteristics for practical applications.
Crystal structures of substituted apatites with general formula Ca10−xMx(PO4)6(OH1−δ)2−xOx, where... more Crystal structures of substituted apatites with general formula Ca10−xMx(PO4)6(OH1−δ)2−xOx, where M=La, Bi, 0≤x<2, were refined using high-resolution X-ray powder diffraction patterns. Individual positions for Ca2+ and M3+-ions localized near Ca2-site were determined. The M3+-ion was found shifted toward the hexagonal channel center with respect to the Ca2+-ion, forming very short bond with the intrachannel O2−, while leaving considerably longer distances to other oxygen atoms, which suggested the existence of a MO+ ion. Distinct bands of stretching M–O modes were observed in the Raman and FT-IR spectra of the compounds. The bond lengths for BiO+ and LaO+ were estimated to be 2.05(1) and 2.09(1) A correspondingly. The latter was almost 0.3 A lower than the shortest La–O bond in La2O3. The realization of such a strong lanthanide–oxygen bond in a crystal lattice could provide a very high axial ligand field and might be implemented to develop high-energy-barrier single-molecule magnets as well as to tune properties of lanthanide-based luminophores.
Physica E-low-dimensional Systems & Nanostructures, May 1, 2008
... The authors also would like to acknowledge the help of Alexey V. Garshev for TEM imaging and ... more ... The authors also would like to acknowledge the help of Alexey V. Garshev for TEM imaging and Mr. Artem P. Malakho for SAXS experiments. References. ... [8] KS Napolsky, AA Eliseev, AV Knotko, AV Lukahsin, AA Vertegel and YD Tretyakov, Mater. Sci. Eng. ...
Abstract SiO2‒TiO2 binary aerogels obtained by the methods of low-temperature (carbon dioxide) an... more Abstract SiO2‒TiO2 binary aerogels obtained by the methods of low-temperature (carbon dioxide) and high-temperature (isopropanol, hexafluoroisopropanol and methyl tert-butyl ether) supercritical drying are considered as multifunctional cosmetic pigments with high anti-shine power and photoprotective properties. The composition and structure of SiO2–TiO2 aerogels obtained by supercritical drying in various fluids were studied by IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, scanning and transmission electron microscopy, and low-temperature nitrogen adsorption. The values of the sun protection factors SPF and UVAPF for the obtained materials are comparable to those of the commercial sunscreens Kronos 1171 and Kronos 2971, and the anti-shine power is approximately 1.5 times higher than that of kaolin-based materials.
The hydrothermal treatment of neutral and acidified KMnO4 solutions at concentration of 0.037–0.0... more The hydrothermal treatment of neutral and acidified KMnO4 solutions at concentration of 0.037–0.093 mol/L and temperature of 120, 170, and 220°С for 24 h leads to selective synthesis of three different manganese dioxide modifications: α-MnO2, δ-MnO2, and β-MnO2. The temperature of hydrothermal treatment and medium acidity has been shown to affect considerably the phase composition of KMnO4 reduction products and reaction yield. The obtained samples of MnO2 have been characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and diffuse reflectance spectroscopy.
Under hydrothermal conditions, the formation of the brookite phase occurs due to the oriented att... more Under hydrothermal conditions, the formation of the brookite phase occurs due to the oriented attachment of anatase particles with subsequent recrystallization.
DyO+ embedded in a hydroxy/fluoro-apatite matrix reveals robust and finely tunable single ion mag... more DyO+ embedded in a hydroxy/fluoro-apatite matrix reveals robust and finely tunable single ion magnet properties. The energy barrier for magnetization reversal grows with the increase of the fluoride and the...
Lithium iron phosphate LiFePO4 triphylite is now one of the core positive electrode (cathode) mat... more Lithium iron phosphate LiFePO4 triphylite is now one of the core positive electrode (cathode) materials enabling the Li-ion battery technology for stationary energy storage applications, which are important for broad implementation of the renewable energy sources. Despite the apparent simplicity of its crystal structure and chemical composition, LiFePO4 is prone to off-stoichiometry and demonstrates rich defect chemistry owing to variations in the cation content and iron oxidation state, and to the redistribution of the cations and vacancies over two crystallographically distinct octahedral sites. The importance of the defects stems from their impact on the electrochemical performance, particularly on limiting the capacity and rate capability through blocking the Li ion diffusion along the channels of the olivine-type LiFePO4 structure. Up to now the polyanionic (i.e. phosphate) sublattice has been considered idle on this playground. Here, we demonstrate that under hydrothermal cond...
This paper reports on the good UV-shielding properties (namely, the sun protection factor and the... more This paper reports on the good UV-shielding properties (namely, the sun protection factor and the factor of protection against UV-A radiation) and low cytotoxicity (including photocytotoxicity) of amorphous and crystalline cerium(iv) phosphates.
Titanium phosphates were recently revealed as promising cosmetic pigments; however, their photoca... more Titanium phosphates were recently revealed as promising cosmetic pigments; however, their photocatalytic activity and sun protective factor (SPF) levels have not been investigated in detail. In this study, we used hydrothermal conditions to prepare nanocrystalline anatase, brookite, and layered titanium phosphate using the titanium lactate complex, NH4H2PO4, and urea as precursors. The samples were characterized by powder X-ray diffraction (XRD) in addition to Raman spectroscopy, transmission and scanning electron microscopy (TEM, SEM), energy-dispersive X-ray spectroscopy (EDX), and UV-Vis spectroscopy. Furthermore, the photocatalytic activity, sun protective factor, and moisture retention ability were determined for the samples. Brookite exhibited the highest SPF value and anatase the lowest, while Ti2O2H(PO4)[(NH4)2PO4]2 displayed highly promising UV protection and moisture retention properties and, therefore, represents a polyfunctional pigment that is particularly well suited f...
Abstract Environmental deterioration and limited resources of hydrocarbons push the development o... more Abstract Environmental deterioration and limited resources of hydrocarbons push the development of alternative power sources. One of the most promising energy carriers is hydrogen. However, handling hydrogen is more hazardous than the use of hydrocarbons because it has a significantly wider flammable range. Thus the development of new sensors for preventing hydrogen leakage is the actual task of modern materials science and chemical engineering. In this work, the response of catalytic sensors to hydrogen with different catalysts of platinum group (Pt, Pd, Ir, Rh, Pt + Pd, Pt + Pd + Rh, Pt + Pd + Ir) in the pre-explosion concentration range is studied. Temperature dependencies of sensitivity are discussed. A hysteresis in sensor response is observed during the cycling of the supply voltage. This phenomenon can be explained by partial transformation of platinum group metal oxides into metallic phase at a temperature of more than 500 °C and reverse metal oxidation at temperatures less than 400 °C. It has been shown that the sensors with catalysts containing Ir and Rh demonstrate more preferable characteristics for practical applications.
Crystal structures of substituted apatites with general formula Ca10−xMx(PO4)6(OH1−δ)2−xOx, where... more Crystal structures of substituted apatites with general formula Ca10−xMx(PO4)6(OH1−δ)2−xOx, where M=La, Bi, 0≤x<2, were refined using high-resolution X-ray powder diffraction patterns. Individual positions for Ca2+ and M3+-ions localized near Ca2-site were determined. The M3+-ion was found shifted toward the hexagonal channel center with respect to the Ca2+-ion, forming very short bond with the intrachannel O2−, while leaving considerably longer distances to other oxygen atoms, which suggested the existence of a MO+ ion. Distinct bands of stretching M–O modes were observed in the Raman and FT-IR spectra of the compounds. The bond lengths for BiO+ and LaO+ were estimated to be 2.05(1) and 2.09(1) A correspondingly. The latter was almost 0.3 A lower than the shortest La–O bond in La2O3. The realization of such a strong lanthanide–oxygen bond in a crystal lattice could provide a very high axial ligand field and might be implemented to develop high-energy-barrier single-molecule magnets as well as to tune properties of lanthanide-based luminophores.
Physica E-low-dimensional Systems & Nanostructures, May 1, 2008
... The authors also would like to acknowledge the help of Alexey V. Garshev for TEM imaging and ... more ... The authors also would like to acknowledge the help of Alexey V. Garshev for TEM imaging and Mr. Artem P. Malakho for SAXS experiments. References. ... [8] KS Napolsky, AA Eliseev, AV Knotko, AV Lukahsin, AA Vertegel and YD Tretyakov, Mater. Sci. Eng. ...
Abstract SiO2‒TiO2 binary aerogels obtained by the methods of low-temperature (carbon dioxide) an... more Abstract SiO2‒TiO2 binary aerogels obtained by the methods of low-temperature (carbon dioxide) and high-temperature (isopropanol, hexafluoroisopropanol and methyl tert-butyl ether) supercritical drying are considered as multifunctional cosmetic pigments with high anti-shine power and photoprotective properties. The composition and structure of SiO2–TiO2 aerogels obtained by supercritical drying in various fluids were studied by IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, scanning and transmission electron microscopy, and low-temperature nitrogen adsorption. The values of the sun protection factors SPF and UVAPF for the obtained materials are comparable to those of the commercial sunscreens Kronos 1171 and Kronos 2971, and the anti-shine power is approximately 1.5 times higher than that of kaolin-based materials.
The hydrothermal treatment of neutral and acidified KMnO4 solutions at concentration of 0.037–0.0... more The hydrothermal treatment of neutral and acidified KMnO4 solutions at concentration of 0.037–0.093 mol/L and temperature of 120, 170, and 220°С for 24 h leads to selective synthesis of three different manganese dioxide modifications: α-MnO2, δ-MnO2, and β-MnO2. The temperature of hydrothermal treatment and medium acidity has been shown to affect considerably the phase composition of KMnO4 reduction products and reaction yield. The obtained samples of MnO2 have been characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and diffuse reflectance spectroscopy.
Under hydrothermal conditions, the formation of the brookite phase occurs due to the oriented att... more Under hydrothermal conditions, the formation of the brookite phase occurs due to the oriented attachment of anatase particles with subsequent recrystallization.
DyO+ embedded in a hydroxy/fluoro-apatite matrix reveals robust and finely tunable single ion mag... more DyO+ embedded in a hydroxy/fluoro-apatite matrix reveals robust and finely tunable single ion magnet properties. The energy barrier for magnetization reversal grows with the increase of the fluoride and the...
Lithium iron phosphate LiFePO4 triphylite is now one of the core positive electrode (cathode) mat... more Lithium iron phosphate LiFePO4 triphylite is now one of the core positive electrode (cathode) materials enabling the Li-ion battery technology for stationary energy storage applications, which are important for broad implementation of the renewable energy sources. Despite the apparent simplicity of its crystal structure and chemical composition, LiFePO4 is prone to off-stoichiometry and demonstrates rich defect chemistry owing to variations in the cation content and iron oxidation state, and to the redistribution of the cations and vacancies over two crystallographically distinct octahedral sites. The importance of the defects stems from their impact on the electrochemical performance, particularly on limiting the capacity and rate capability through blocking the Li ion diffusion along the channels of the olivine-type LiFePO4 structure. Up to now the polyanionic (i.e. phosphate) sublattice has been considered idle on this playground. Here, we demonstrate that under hydrothermal cond...
This paper reports on the good UV-shielding properties (namely, the sun protection factor and the... more This paper reports on the good UV-shielding properties (namely, the sun protection factor and the factor of protection against UV-A radiation) and low cytotoxicity (including photocytotoxicity) of amorphous and crystalline cerium(iv) phosphates.
Titanium phosphates were recently revealed as promising cosmetic pigments; however, their photoca... more Titanium phosphates were recently revealed as promising cosmetic pigments; however, their photocatalytic activity and sun protective factor (SPF) levels have not been investigated in detail. In this study, we used hydrothermal conditions to prepare nanocrystalline anatase, brookite, and layered titanium phosphate using the titanium lactate complex, NH4H2PO4, and urea as precursors. The samples were characterized by powder X-ray diffraction (XRD) in addition to Raman spectroscopy, transmission and scanning electron microscopy (TEM, SEM), energy-dispersive X-ray spectroscopy (EDX), and UV-Vis spectroscopy. Furthermore, the photocatalytic activity, sun protective factor, and moisture retention ability were determined for the samples. Brookite exhibited the highest SPF value and anatase the lowest, while Ti2O2H(PO4)[(NH4)2PO4]2 displayed highly promising UV protection and moisture retention properties and, therefore, represents a polyfunctional pigment that is particularly well suited f...
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