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Abstract: Pt-CeO2/carbon nanotubes (Pt-CeO2/CNTs), based on glucose polymerization in the inner pores of anodic aluminum oxide templates under hydrothermal conditions followed by carbonization at high temperature, were synthesized using as precursors H2PtCl6 reduced by NaBH4 and CeCl3 deposited by NaOH. Pt nanoparticles and CeO2 units were inserted onto the outer surfaces and inner surfaces of the as-prepared carbon nanotubes (CNTs). The resulting structures were characterized by scanning electron microscopy (SEM). The electrocatalytic performances of the Pt-CeO2/CNTs modified glass carbon electrodes were investigated for methanol oxidation by cyclic voltammetric and chronoamperometric measurements. It was found that compared with Pt/CNTs, the hybrid Pt-CeO2/CNTs electrodes showed superior catalytic performance when the molar ratio of Pt to CeO2 in the catalyst was about 2:1. The increased catalytic efficiency of Pt is likely to result from its combination with CeO2. [Copyright &y& Elsevier]

Abstract: The effects of zinc oxide (ZnO) additive on the crystal structure, densification, and electrical conductivity of the GdSmZr2O7 ceramic have been examined. The GdSmZr2O7 ceramic with and without the addition of 1 wt.% ZnO sintered at temperatures between 1773 and 1973 K exhibits a single cubic pyrochlore-type phase. ZnO is very effective as a sintering aid for the GdSmZr2O7 ceramic, and it reduces the sintering temperature by about 200 K with a positive effect on the total conductivity. The total conductivity of the ZnO-modified GdSmZr2O7, as measured by A.C. impedance spectroscopy under an air atmosphere, is higher than that of the unmodified GdSmZr2O7 at identical temperature levels. At 1173 K, the highest total conductivity of the ZnO-modified GdSmZr2O7 is about fifteen percent higher than that of the unmodified GdSmZr2O7. The 1 wt.% ZnO-modified GdSmZr2O7 is one of good oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10−4 to 1.0 atm at different test temperatures. [Copyright &y& Elsevier]

Abstract: Gd2−x Sm x Zr2O7 (x =0, 0.2, 0.6, 1.0, 1.4, 1.8, 2.0) ceramic powders synthesized with the chemical-coprecipitation and calcination method were pressureless-sintered at 1873K for 10h in air. The electrical conductivity of Gd2−x Sm x Zr2O7 ceramics was investigated by complex impedance spectroscopy over a frequency range of 0.01Hz to 15MHz. Gd2−x Sm x Zr2O7 is an oxide-ion conductor in the oxygen partial pressure range from 1.0×10−15 to 1.0atm and in the temperature range of 623–873K. The measured electrical conductivity obeys the Arrhenius relation. The activation energy and pre-exponential factor for grain-interior conductivity gradually decrease with increasing Sm content. The grain-interior conductivity varies with the Sm substitution for Gd, and reaches the maximum at the equal molar of Sm3+ and Gd3+ in Gd2−x Sm x Zr2O7 ceramics. A significant increase in the grain-interior conductivity is obtained by isovalent rare-earth element like Sm substitution for Gd in the temperature range of 623–873K. [Copyright &y& Elsevier]

Mechanical activation followed by rotary heating has been successfully applied to the synthesis of Cr-doped lithium manganese oxide (LiMn2O4) powders. The precursor of LiCrxMn2−xO4 for Li-ion batteries has been synthesized from LiOH·H2O, MnO2, and Cr2O3 as starting materials by mechanical activation, which ensured a high level of homogeneity in the chemical composition of the precursor and resulted in a reduction in the synthesis temperature and heating time. Highly crystallized LiCrxMn2−xO4 (0.04≤x≤0.10) powders were obtained by subsequent rotary heating of the precursor at 550–750 °C for 2 h. Rotary heating enhanced the experimental control in chemical composition, particle size distribution and microstructure of the final products. The optimum mechanical activation condition was determined based on XRD analysis. The synthesized LiCrxMn2−xO4 powder has a narrow particle size distribution, high discharge capacities and good cyclability. The method of mechanical activation combined with rotary heating should be an excellent technique of decreasing synthesis temperature and shortening heating time, and enhancing the uniformity of particle size of the product. [Copyright &y& Elsevier]

Abstract: The effect of nickel oxide addition on the sintering behavior and electrical properties of the GdSmZr2O7 ceramic has been investigated. The crystal structure, microstructure and electrical properties of the GdSmZr2O7 ceramic incorporated with or without 1 wt.% nickel oxide are characterized by the X-ray diffraction, field-emission scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The GdSmZr2O7 ceramic exhibits a single phase of the pyrochlore-type structure. No chemical reaction between GdSmZr2O7 and NiO is found in the sintered samples. The grain, grain boundary, and total conductivity of the GdSmZr2O7 ceramic with or without NiO addition obey the Arrhenius relation. The addition of a small amount of NiO to the GdSmZr2O7 ceramic greatly promotes the densification process, achieving 93% of the theoretical density after sintering at 1773 K in air. This reduces the sintering temperature by about 200 K, without adversely affecting the total conductivity of the GdSmZr2O7 ceramic. The GdSmZr2O7 ceramic with 1 wt.% NiO addition is an oxide-ion conductor in the oxygen partial pressure range of 1.0 × 10−4 to 1.0 atm at all test temperature levels. [Copyright &y& Elsevier]

Abstract: The GdSmZr2O7 ceramic is prepared by pressureless-sintered method under different conditions as a possible solid electrolyte. The crystal structure, microstructure and electrical properties are characterized by the X-ray diffraction, field-emission scanning electron microscopy and ac impedance spectroscopy, respectively. The GdSmZr2O7 ceramic exhibits a single phase of the pyrochlore-type structure. The total conductivity of the GdSmZr2O7 ceramic obeys the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173K. The GdSmZr2O7 ceramic is an oxide-ion conductor in the oxygen partial pressure range of 1.0×10−4 to 1.0atm at all test temperature levels. According to the experimental results of the present work, the maximum value of the total conductivity for the GdSmZr2O7 ceramic is about 1.01×10−2 Scm−1 at 1173K. [Copyright &y& Elsevier]