One-pot synthesis of Sb-Fe-carbon-fiber composites with in situ catalytic growth of carbon fibers

A Sb-Fe-carbon-fiber （CF） composite was prepared by a chemical vapor deposition （CVD） method with in situ growth of CFs us- ing Sb203/Fe2O3 as the precursor and acetylene （C2H2） as the carbon source. The Sb-Fe-CF composite was characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and transmission electron microscopy （TEM）, and its electrochemical per- formance was investigated by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. The Sb-Fe-CF composite shows a better cycling stability than the Sb-amorphous-carbon composite prepared by the same CVD method but using Sb2O3 as the precur- sor. Improvements in cycling stability of the Sb-Fe-CF composite can be attributed to the formation of three-dimensional network structure by CFs, which can connect Sb particles firmly. In addition, the CF layer can buffer the volume change effectively.

Fabrication of Syringe-Shaped GaN Nanorods

Syringe-shaped GaN nanorods are synthesized on Si（111） substrates by annealing sputtered Ga2O3/BN films under flowing ammonia at temperature of 950℃. Most of the nanorods consist of a main rod and a top needle, looking like a syringe. X-ray diffraction and selected-area electron diffraction confirm that the syringe-shaped nanorods are hexagonal wurtzite GaN. Scanning electron microscopy and high-resolution transmission electron microscopy reveal that these nanorods are as long as several micrometres, with diameters ranging from 100 to 300nm. In addition to the BN intermediate layer, the proper annealing temperature has been demonstrated to be a crucial factor for the growth of syringe-shaped nanorods by this method.

Millimeter-sized few-layer graphene sheets with aligned channels for fast lithium-ion charging kinetics

Assembly of the top-down graphene units mostly results in 3D porous structure with randomly organized pores.The direct bottom-up synthesis of macroscopic 2D graphene sheets with organized pores are long sought in materials chemistry field,but rarely achieved.Herein,we present a self-catalysisassisted bottom-up route usingL-glutamic acid and iron chloride as starting materials for the fabrication of the millimeter-sized few-layer graphene sheets with aligned porous channels parallel to the 2D direction.The amino-and carboxyl-functional groups inL-glutamic acid can coordinate with iron cations,thus allowing an atomic dispersion of iron cations.The pyrolysis thus initiated the growth of graphene catalyzed by in-situ generated iron nanoparticles,and a dynamic flow of iron nanoparticles eventually led to the formation of millimeter-sized few-layer graphene sheets with aligned channels(60-85 nm in diameter).Used as anodes in lithium-ion batteries,these graphene sheets showed a good rate capability(142 m A h g^(-1) at 2 A g^(-1))and high capacity retention of 93%at 2 A g^(-1) after 1200 cycles.Kinetic analysis revealed that lithium ions storage was dominated by diffusion behavior and capacitive behavior together,in that graphene sheets with aligned channels could accelerate electron transfer and shorten lithium ions transport pathway.This work provides a novel approach to prepare unique porous graphene materials with specific structure for energy storage.

In-situ One-pot Preparation of LiFePO_4/Carbon-Nanofibers Composites and Their Electrochemical Performance

A novel in-situ route was employed to synthesize LiFePO4/carbon-nanofibers （CNFs） composites. The route combined high-temperature solid phase reaction with chemical vapor deposition （CVD） using Fe2O3 and LiH2PO4 as the precursors for LiFePO4 growth and acetylene （C2H2） as the carbon source for CNFs growth. The composites were characterized by X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） specific surface area, field emission scanning electron microscopy （FE-SEM）, and transmission electron microscopy （TEM）. The electrochemical performance of the composites was studied by galvanostatic cycling and cyclic voltammetry （CV）. The results showed that the in-situ CNFs growth could be realized by the catalytic effect of the Fe2O3 precursor. The sample after 80 min CVD reaction showed the best electrochemical performance, indicating a promising application in high-power Li-ion batteries.

Synthesis of Monodisperse CdS Nanorods Catalyzed by Au Nanoparticles

Semiconductor nanocrystals(dots,rods,wires,etc.)exhibit a wide range of electrical and optical properties that differ from those of the corresponding bulk materials.These properties depend on both nanocrystal size and shape.Compared with nanodots,nanorods have an additional degree of freedom,the length or aspect ratio,and reduced symmetry,which leads to anisotropic properties.In this paper,we report the Au nanoparticle-catalyzed colloidal synthesis of monodisperse CdS nanorods.Based on systematic high resolution transmission electron microscopy studies,we propose a growth mechanism for these nanorods.

One-pot In-situ Synthesis of Sn/Carbon-fibers Nanocomposite by Chemical Vapor Deposition and Its Li-storage Properties

Sn/carbon-fibers（CFs） nanocomposite has been prepared by chemical vapor deposition with in-situ catalytic growth of CFs.The nanocomposite has been characterized by X-ray diffraction（XRD）,field emission scanning electron microscopy（FE-SEM）,transmission electron microscopy（TEM） and Raman spectrum.The electrochemical performance of the nanocomposite has been investigated by galvanostatic cycling and cyclic voltammetry（CV）.It has been found that a three-dimensional conductive network forms by the interconnected CFs,which offers conductive channels for the Sn nanoparticles.The nanocomposite gives a first charge capacity of 385 mAh.g-1 and exhibits an improved cycling stability than bare Sn.