Yinglin Yan

An efficient process to fabricate spherical hierarchical LiFePO 4 /C cathode composites with controllable coating thickness

Hierarchical lithium iron phosphate/carbon (LiFePO4/C) microspheres were fabricated successfully using a facile spray drying-assisted coprecipitation method. A relatively short calcination time and a relatively low calcination temperature were adopted to prepare the hierarchical LiFePO4/C microspheres. The hierarchical microspheres consisted of nanoparticles with a uniform coating of amorphous carbon. The thickness of the carbon layer was controlled by the addition of glucose. The hierarchical LiFePO4/C microspheres exhibited a high tap density and a large specific surface area. The electrochemical properties of the sample were investigated. The sample exhibited a better rate capability and a better cyclability than the coral-like LiFePO4/C cathode material, and these were ascribed to the highly uniform carbon coating and the self-assembled nanoparticles.

Influence of pH and CTAB on Luminescent Property of Hydrothermally Synthesized GdVO4: Eu3+ Phosphors

Luminescent phosphors Gd VO4: Eu3 +was prepared in solutions with different p H values by hydrothermal synthesis route using Gd2O3, NH4VO3 and Eu2O3as precursors, and cetyl trimethyl ammonium bromide(CTAB) as surfactant. The synthesized products were characterized in terms of morphology, structure and luminescent performance by means of XRD, SEM, TEM, and PL. The results show that in an acid solution with p H=1, the size of synthesized Gd VO4: Eu3 +crystal grains is of micron scale;in a solution with p H=4, their size shrinks to nano-scale; it turned out well-dispersed nano-flakes of about50 nm in solution with p H=7; besides, in solution with p H=10, a certain amount of impurity Gd(OH)3was detected by XRD for the synthesized Gd VO4: Eu3+crystal grains. On the other hand, the surfactant affected obviously the final morphology of the synthesized Gd VO4: Eu3 +crystal grains in terms of changes in the crystal growth direction and the aggregation shape, correspondingly, the luminescent properties were affected by grain size and crystallinity. It turned out that square Gd VO4: Eu3 +nano-crystals with well crystallinity represented the optimal emission performance. But it is noted that the aggregation effect may weaken the luminescent property of the products.