Search

Abstract: A few compositions in the system Ce1−x Sr x O2−x with 0.05≤ x ≤0.20 have been prepared by auto-combustion method. More than 93% of theoretical density has been achieved by sintering at 1350°C for 4h. Solid solution has formed in the composition with x =0.05. All other compositions have been found to contain XRD lines of SrCeO3 beside the major fluorite phase. Complex plane impedance analysis has clearly revealed the contribution of grains, grain boundaries, and electrode specimen interface to the total observed resistance of the sample. Conduction occurs mainly due to diffusion of O2− ions through oxygen vacancies as indicated by values of activation energy of conduction. Composition, Ce0.95 Sr0.05 O1.95 exhibits the highest ionic conductivity 3.26×10−3 Scm−1 at 500°C among the series. Ionic conductivity decreases gradually with increasing x. This is due to the formation of a second phase SrCeO3 and increasing probability of formation of neutral associated defect pairs, . [Copyright &y& Elsevier]

Abstract: An efficient synthesis is used for the first time to prepare CuO/reduced graphene oxide nanocomposite anode materials for lithium ion batteries. Initially, copper oxide (CuO) nanoparticles are synthesized via a simple, facile and inexpensive microwave-assisted method within short reaction times (<20 min) and subsequent heat treatment at 500 °C for 5 h. The obtained pure CuO nanoparticles are mixed with 10 wt% of graphene nanosheets by the use of spex mill for 1 min. By short-time spex-milling, a unique CuO/reduced graphene oxide nanocomposite is obtained with a microstructure of multi-scale CuO nanoparticles homogeneously dispersed in a graphene matrix. The synthesized samples are characterized using X-ray diffraction and field-emission transmission electron microscopy studies. The spex-milled nanocomposite anode exhibits better electrochemical performance with higher reversible capacity and excellent cyclability in comparison with pure CuO nanoparticles. The initial discharge capacity of the pure CuO nanoparticles and their nanocomposite are 785.2 mAh g−1 and 1043.3 mAh g−1 with reversible capacity retention of 392.1 mAh g−1 and 516.4 mAh g−1 after 45 cycles respectively. The excellent electrochemical performance of CuO/reduced graphene oxide nanocomposite can be attributed to their unique structures, which intimately combine the conductive graphene nanosheets network with uniformly dispersed CuO nanoparticles. [Copyright &y& Elsevier]