Huagui Zheng

Optical and electrochemical properties of nanosized NiO via thermal decomposition of nickel oxalate nanofibres

Nickel oxide nanoparticles with an average diameter of about 9 nm were synthesized via thermal decomposition of NiC2O4 precursor at 450 °C. The nanoparticles were investigated using XRD, TEM, TGA, and UV–vis spectrophotometry. The optical absorption spectrum indicates that the NiO nanoparticles have a direct band gap of 3.56 eV. The electrochemical tests show that the ultrafine NiO nanoparticles, as a promising electrode material, can deliver a large reversible discharge capacity of about 610 mA h g−1.

Synthesis of β-FeOOH and α-Fe2O3 nanorods and electrochemical properties of β-FeOOH

β-FeOOH nanorods with a tunnel-type structure were synthesized via a hydrothermal method at low temperature and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and galvanostatic tests. From TEM bright-field images, a rodlike morphology with an average diameter of 30 ± 5 nm and an average length of 400 nm (aspect ratio ≈ 13) is observed. Electrochemical tests show that thesew nanorods deliver a large discharge capacity of 275 mA h g−1vs. Li metal at 0.1 mA cm−2 (voltage window 1.5–4.2 V). α-Fe2O3 nanorods with a regular pore structure were obtained by calcining the as-synthesized FeOOH at 520 °C.

Preparation of nickel nanopowders in ethanol-water system (EWS)

PVP-protected nanoscale Ni powders are prepared in ethanol-water system (EWS). The product was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). X-ray photoelectroscopy (XPS) was utilized to determine the surface state of the sample. The product can be isolated in solid state and stabilized for months. The powders are dispersed homogeneously shown in TEM figure.

Citric acid-assisted sol-gel synthesis of nanocrystalline LiMn2O4 spinel as cathode material

Nanocrystalline LiMn2O4 spinel was synthesized by a sol–gel method using citric acid as a chelating agent at the calcination temperature of 600 � C for 10 h. The as-prepared LiMn2O4 was investigated by a variety of techniques, including X-ray powder diffraction, transmission electron microscopy (TEM), and X-ray photoelectron spectra. TEM images indicated that the average crystallite size is about 40 nm with a fairly narrow size-distribution. Results showed that the calcination temperature and the calcination time played significant roles in the formation of nanocrystalline LiMn2O4. A possible mechanism on the formation of the nanocrystallites was also discussed. r 2003 Elsevier Science B.V. All rights reserved.

Changeable position of SPR peak of Ag nanoparticles embedded in mesoporous SiO2 glass by annealing treatment

Small Ag particles or clusters doped mesoporous SiO2 composite glass were prepared by the sol–gel process combined girradiation at room temperature and in ambient pressure. High-resolution transmission electron microscope (HRTEM) has revealed the existence of Ag nanoparticles and their growing through annealing treatments. With the particle size changing, an interesting reversible peak shift effect of the surface plasma resonance (SPR) was observed in the optical absorption measurement, which is explained as a comprehensive competitive result of both intrinsic property (size effect) and extrinsic influence from the matrix or the surrounding medium (interface interaction and its induced spill-out effect). # 2002 Elsevier Science B.V. All rights reserved.

Preparation of nanosized particles of FeNi and FeCo alloy in solution

FeNi and FeCo alloys of different compositions are prepared at room temperature in solution by surface catalysis or high-pressure inducement. Their sizes and morphologies are analyzed with X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). The phase transformations of these alloys are similar to the reported phase diagrams of FeNi and FeCo alloys. HRTEM image of FeCo4 alloy shows the presence of rods. Their magnetic properties are studied. Surprisingly, the coercivity of FeCo4 alloy reaches as high as 718 Oe.

Synthesis of cobalt nanoparticles in ethanol hydrazine alkaline system (EHAS) at room temperature

Abstract Hydrazine, used as reducing agent in ethanol hydrazine alkaline system (EHAS) at room temperature, reduced cobalt salts (CoCl 2 ·6H 2 O or CoSO 4 ·7H 2 O) to FCC phase and HCP phase cobalt nanoparticles that were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry (TG) and differential thermal analysis (DTA). After the nanoparticles were heated in argon at 200 °C for 2 h, the HCP phase cobalt nanoparticles grow more regular and larger, and the coercivity of the sample is increased from 480 to 680 Oe.

Low temperature synthesis of metastable lithium ferrite: magnetic and electrochemical properties

Ultrafine ?-LiFe5O8 nanoparticles were successfully synthesized at the low temperature of 140??C through a hydrothermal method. The average particle size is about 5?nm with a fairly narrow size distribution. The saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) could be determined to be 25.23?emu?g?1, 3.95?emu?g?1, and 301?Oe, respectively. The Teflon cell using the prepared nanoparticles as active cathode material shows an initial discharge capacity of about 162?mA?h?g?1. The as-prepared ultrafine ?-LiFe5O8 nanoparticles exhibit higher capacity than any other known lithium ferrites, which may be ascribed to the unique microstructure and smaller particle size achieved by the hydrothermal synthesis procedure.

Synthesis of MnWO4 nanofibres by a surfactant-assisted complexation–precipitation approach and control of morphology

Single-crystal MnWO(4) nanofibres with diameters as small as 3-4 nm and length up to 800-1000 nm have been successfully synthesized by a novel surfactant-assisted complexation-precipitation method. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electron diffraction (ED) were employed to study the crystal structure and morphologies of the products. Experiments show that the complexation and the surfactant are the crucial factors affecting the morphology of the products. The possible formation process and growth mechanism have been proposed.

A benzene-thermal synthesis of powdered cubic zirconium nitride

Abstract Powdered zirconium nitride (ZrN) has been prepared via a benzene-thermal synthesis via the reaction of anhydrous zirconium tetrachloride (ZrCl4) and lithium nitride (Li3N) at a temperature of 380–400 °C. The product was analyzed by X-ray photoelectron spectroscopy (XPS), and the results show the mole ratio of Zr/N is 1:0.87. X-ray diffraction (XRD) pattern can be indexed to the cubic cell of ZrN with the lattice constant a=4.5675 A. Transmission electron microscope (TEM) images indicate that average particle size is about 180 nm in diameter.