ABSTRACT A highly ordered and worm-like mesoporous TiO2 materials have been prepared by evaporati... more ABSTRACT A highly ordered and worm-like mesoporous TiO2 materials have been prepared by evaporation-induced self-assembly method (EISA) using different concentrations of tri-block copolymer Pluronic F127 as a structure-directing agent and inorganic chlorides as precursors in a non-aqueous medium. The characterization of the mesoporous TiO2 was carried out using small angle X-ray diffraction (SAXD), transmission electron microscopy (TEM) and N2 adsorption/desorption. The well-ordered mesoporous TiO2 showed average pore size of 2.8–3.7 nm and high specific area of 263 m2/g. From TEM observation, the pore pore-wall is composed of nano-crystalline TiO2 domains after successfully synthesized at 573 K. The pore morphology changed from well-ordered to worm-like as the concentration of Pluronic F127 increased beyond 8.35%.
ABSTRACT Without Sr addition, the sintered La2O3 and CuO powder mixture in a mole ratio of 1:2 fo... more ABSTRACT Without Sr addition, the sintered La2O3 and CuO powder mixture in a mole ratio of 1:2 formed K2NiF4-structured La2CuO4 with excess CuO. When 15% of strontium was added, La2CuO4 transformed into the single perovskite La1−xSrxCuO2.5−δ phase with orthorhombic structure. As the strontium addition increased to 20%, the perovskite lattice changed from orthorhombic to tetragonal. These phase transitions may be attributed to the enhanced oxidation of the divalent cupper ions (Cu2+) to trivalent ones (Cu3+) by the strontium addition. Based on the electroneutrality in an ABO3 perovskite lattice, a divalent cation is unstable in the B-site cation sub-lattice when the A-site is occupied by a trivalent cation such as La3+. As strontium was added into the A-site cation sub-lattice, the oxidation of Cu2+ ion into trivalent Cu3+ ion was enhanced. The increase of Cu3+ concentration strengthened the electrostatic bonding (ESB) of copper ions with their neighboring anions. Consequently, the symmetrical tetragonal Sr-doped lanthanum copper oxide was obtained.
... J. Power Sources, 178 (2008), p. 368. [5] James R. Wilson, Worawarit Kobsiriphat, Roberto Men... more ... J. Power Sources, 178 (2008), p. 368. [5] James R. Wilson, Worawarit Kobsiriphat, Roberto Mendoza, Hsun-Yi Chen, Jon M. Hiller, Dean J. Miller, Katsuyo Thornton, Peter W. Voorhees, Stuart B. Adler and Scott A. Barnett. ... [9] A. Karthikeyan, C. Chang and S. Ramanathan. Appl. ...
ABSTRACT The hexagonal mesostructured nanocrystalline 16 mol% yttria-stabilized zirconia (8YSZ) f... more ABSTRACT The hexagonal mesostructured nanocrystalline 16 mol% yttria-stabilized zirconia (8YSZ) formed by using a Pluronic triblock copolymer F127 as template is reported as a function of temperature. The characterization of the samples is achieved using wide-angle XRD diffraction, small-angle XRD diffraction, nitrogen adsorption–desorption, and transmission electron microscopy. The mesostructured 8YSZ calcined at 500 °C is found to be based upon a 2D periodic array of mesopores with diameter around 6.4 nm and the 8YSZ framework is composed of about 4.8 nm nanocrystallites. The sample has a BET surface area of 124 m2/g with a narrow pore size distribution. The ordered mesoporous structure remained even after calcination up to temperature of 600 °C grew out collapsed gradually when calcined above 700 °C owing to the fact that the crystallite size of 8YSZ larger than the inorganic pore-wall thickness.
Highly conductive cubic (Y0.25Bi0.75)2O3 tends to transform to rhombohedral (Y0.25Bi0.75)2O3 when... more Highly conductive cubic (Y0.25Bi0.75)2O3 tends to transform to rhombohedral (Y0.25Bi0.75)2O3 when annealed at 600°C for more than 200 h. Although the rhombohedral phase of (Y0.25Bi0.75)2O3 was known to be the stable phase at temperatures ≤600°C, it was found that the annealed (Y0.25Bi0.75)2O3 was not thermodynamically stable in the water-containing environment. From x-ray diffraction and transmission electron microscopy analysis, it was observed that the annealed (Y0.25Bi0.75)2O3 easily decomposed into monoclinic α-Bi2O3 and yttrium hydroxide at a temperature as low as 50°C. The monoclinic α-Bi2O3 further reacted with CO2 and formed Bi2O2CO3. Consequently, the annealed (Y0.25Bi0.75)2O3 degraded and became flaky powder. Scanning electron microscopy micrographs of water-reacted (Y0.25Bi0.75)2O3 also showed surface swelling and peeling. Such surface deterioration was caused by a large volume increase during the water reaction. Similar reaction was also observed when the annealed (Y0.25...
ABSTRACT Nickel-cobalt oxide with spinel structure was successfully fabricated using a wet chemic... more ABSTRACT Nickel-cobalt oxide with spinel structure was successfully fabricated using a wet chemical route followed by calcinations at 300 °C. In nickel-cobalt spinel oxide, Ni2+ ions occupy the octahedral sites and Co3+ ions are distributed over both octahedral and tetrahedral sites. Very interestingly, nickel-cobalt spinel oxide does not only show a p-type semi-conducting behavior material but also exhibits desired transparency in infrared wavelengths. Electrical and optical properties of the deposited films were investigated as a function of different processing conditions. The sputtering target is fabricated by homogeneously mixing oxide powders and followed by sintering at 1,500 °C. The nickel-cobalt oxide film showed a resistivity as low as 10−2 Ω-cm by radio frequency (RF) magnetron sputtering in a pure oxygen atmosphere. The sputter-deposited nickel-cobalt oxide films also showed more than 70% transmittance in the infrared range.
ABSTRACT A highly ordered and worm-like mesoporous TiO2 materials have been prepared by evaporati... more ABSTRACT A highly ordered and worm-like mesoporous TiO2 materials have been prepared by evaporation-induced self-assembly method (EISA) using different concentrations of tri-block copolymer Pluronic F127 as a structure-directing agent and inorganic chlorides as precursors in a non-aqueous medium. The characterization of the mesoporous TiO2 was carried out using small angle X-ray diffraction (SAXD), transmission electron microscopy (TEM) and N2 adsorption/desorption. The well-ordered mesoporous TiO2 showed average pore size of 2.8–3.7 nm and high specific area of 263 m2/g. From TEM observation, the pore pore-wall is composed of nano-crystalline TiO2 domains after successfully synthesized at 573 K. The pore morphology changed from well-ordered to worm-like as the concentration of Pluronic F127 increased beyond 8.35%.
ABSTRACT Without Sr addition, the sintered La2O3 and CuO powder mixture in a mole ratio of 1:2 fo... more ABSTRACT Without Sr addition, the sintered La2O3 and CuO powder mixture in a mole ratio of 1:2 formed K2NiF4-structured La2CuO4 with excess CuO. When 15% of strontium was added, La2CuO4 transformed into the single perovskite La1−xSrxCuO2.5−δ phase with orthorhombic structure. As the strontium addition increased to 20%, the perovskite lattice changed from orthorhombic to tetragonal. These phase transitions may be attributed to the enhanced oxidation of the divalent cupper ions (Cu2+) to trivalent ones (Cu3+) by the strontium addition. Based on the electroneutrality in an ABO3 perovskite lattice, a divalent cation is unstable in the B-site cation sub-lattice when the A-site is occupied by a trivalent cation such as La3+. As strontium was added into the A-site cation sub-lattice, the oxidation of Cu2+ ion into trivalent Cu3+ ion was enhanced. The increase of Cu3+ concentration strengthened the electrostatic bonding (ESB) of copper ions with their neighboring anions. Consequently, the symmetrical tetragonal Sr-doped lanthanum copper oxide was obtained.
... J. Power Sources, 178 (2008), p. 368. [5] James R. Wilson, Worawarit Kobsiriphat, Roberto Men... more ... J. Power Sources, 178 (2008), p. 368. [5] James R. Wilson, Worawarit Kobsiriphat, Roberto Mendoza, Hsun-Yi Chen, Jon M. Hiller, Dean J. Miller, Katsuyo Thornton, Peter W. Voorhees, Stuart B. Adler and Scott A. Barnett. ... [9] A. Karthikeyan, C. Chang and S. Ramanathan. Appl. ...
ABSTRACT The hexagonal mesostructured nanocrystalline 16 mol% yttria-stabilized zirconia (8YSZ) f... more ABSTRACT The hexagonal mesostructured nanocrystalline 16 mol% yttria-stabilized zirconia (8YSZ) formed by using a Pluronic triblock copolymer F127 as template is reported as a function of temperature. The characterization of the samples is achieved using wide-angle XRD diffraction, small-angle XRD diffraction, nitrogen adsorption–desorption, and transmission electron microscopy. The mesostructured 8YSZ calcined at 500 °C is found to be based upon a 2D periodic array of mesopores with diameter around 6.4 nm and the 8YSZ framework is composed of about 4.8 nm nanocrystallites. The sample has a BET surface area of 124 m2/g with a narrow pore size distribution. The ordered mesoporous structure remained even after calcination up to temperature of 600 °C grew out collapsed gradually when calcined above 700 °C owing to the fact that the crystallite size of 8YSZ larger than the inorganic pore-wall thickness.
Highly conductive cubic (Y0.25Bi0.75)2O3 tends to transform to rhombohedral (Y0.25Bi0.75)2O3 when... more Highly conductive cubic (Y0.25Bi0.75)2O3 tends to transform to rhombohedral (Y0.25Bi0.75)2O3 when annealed at 600°C for more than 200 h. Although the rhombohedral phase of (Y0.25Bi0.75)2O3 was known to be the stable phase at temperatures ≤600°C, it was found that the annealed (Y0.25Bi0.75)2O3 was not thermodynamically stable in the water-containing environment. From x-ray diffraction and transmission electron microscopy analysis, it was observed that the annealed (Y0.25Bi0.75)2O3 easily decomposed into monoclinic α-Bi2O3 and yttrium hydroxide at a temperature as low as 50°C. The monoclinic α-Bi2O3 further reacted with CO2 and formed Bi2O2CO3. Consequently, the annealed (Y0.25Bi0.75)2O3 degraded and became flaky powder. Scanning electron microscopy micrographs of water-reacted (Y0.25Bi0.75)2O3 also showed surface swelling and peeling. Such surface deterioration was caused by a large volume increase during the water reaction. Similar reaction was also observed when the annealed (Y0.25...
ABSTRACT Nickel-cobalt oxide with spinel structure was successfully fabricated using a wet chemic... more ABSTRACT Nickel-cobalt oxide with spinel structure was successfully fabricated using a wet chemical route followed by calcinations at 300 °C. In nickel-cobalt spinel oxide, Ni2+ ions occupy the octahedral sites and Co3+ ions are distributed over both octahedral and tetrahedral sites. Very interestingly, nickel-cobalt spinel oxide does not only show a p-type semi-conducting behavior material but also exhibits desired transparency in infrared wavelengths. Electrical and optical properties of the deposited films were investigated as a function of different processing conditions. The sputtering target is fabricated by homogeneously mixing oxide powders and followed by sintering at 1,500 °C. The nickel-cobalt oxide film showed a resistivity as low as 10−2 Ω-cm by radio frequency (RF) magnetron sputtering in a pure oxygen atmosphere. The sputter-deposited nickel-cobalt oxide films also showed more than 70% transmittance in the infrared range.
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