Guien Zhou

Growth of SiC nanorods at low temperature

Cubic-phase SiC (β-SiC) nanorods were synthesized through a one-step reaction under pressure at 400 °C by which the crystalline product can be obtained directly without annealing at high temperature. The reaction was carried out in an autoclave by using SiCl4 and CCl4 as reactants and metal Na as coreductant. The x-ray diffraction pattern indicates the formation of β-SiC and x-ray photoelectron spectra display the stoichiometric relation between Si and C. Transmission electron microscopy images reveal that the product consists of nanorods with diameters from 10 to 40 nm and lengths up to several micrometers.

Preparation of ultrafine powders of TiO2 by hydrothermal H2O2 oxidation starting from metallic Ti

Ultrafine powders of Nb2O5 were prepared by hydrothermal H2O2 oxidation of metallic Nb, resulting in the formation of the high pressure pseudo-hexagonal phase. After annealing at 600 degrees C for 24 h, a transformation to the orthorhombic L-phase Nb2O5 occurred, which is also a high pressure phase.

Preparation and characterization of nanocrystalline powders of cuprous oxide by using γ-radiation

Abstract The γ-radiation method has been firstly used to prepare nanocrystalline powders of cuprous oxide from cupric sulfate aqueous solution in the presence of CH 3 COOH CH 3 COONa buffer pair. X-ray powder diffraction reveals that the product is single phase of cuprous oxide. Electron microscopy shows that the average particle size of cuprous oxide prepared is about 14 nm. Influences of experimental conditions on particle size of cuprous oxide and the mechanism of the formation of cuprous oxide are discussed.

Hydrothermal preparation of α-MnS nanorods from elements

A simple and convenient elemental-direction-reaction route has been successfully developed to prepare α-MnS nanorods under hydrothermal conditions using manganese and sulfur powder as starting materials in the temperature range of 240–260°C. It was found that the temperature was a key factor influencing the phase purity of the titled compound. A possible formation mechanism of the α-MnS nanorods was proposed on the basis of our contrast experimental results, which revealed that α-MnS nanorods were formed via an in situ sulfiding Mn(OH)2 nanorods produced by the reaction of manganese and water.

HYDROTHERMAL EPITAXY OF HIGHLY ORIENTED TIO2 THIN FILMS ON SILICON

Highly oriented thin films (0.15 μm) of titania on Si (100) substrates have been prepared first by hydrothermal treatment of TiO42− solution (0.6–1.2M) at relatively low temperatures. Films made at 100–200 °C contain only the anatase phase with (112) orientation, adhere well to the substrates. The hydrothermal temperature, time, and the pH value of TiO42− solution are the critical parameters determining the formation of films.

A hydrothermal synthesis of orthorhombic nanocrystalline cobalt diselenide CoSe2

Abstract Nanocrystalline CoSe 2 was successfully synthesized in the temperature range 90–170°C through a hydrothermal method. All the reflections in the XRD pattern of CoSe 2 could be indexed as an orthorhombic system with cell parameters a = 3.589, b = 4.838, and c = 5.713 A. TEM images of the products showed a rod-like morphology. Disproportionation products of selenium in alkaline aqueous solution provide a convenient chalcogen source and make possible the synthesis of transition-metal selenides under hydrothermal conditions. The mechanism of the formation of CoSe 2 is proposed.

A hydrothermal reaction to synthesize CuFeS2 nanorods

Abstract A hydrothermal reaction route has been developed to prepare chalcopyrite phase CuFeS2 nanorods at 200–250°C. X-ray powder diffraction and transmission electron microscopy results reveal that the CuFeS2 synthesized displays nanorods with diameters of 20–40 nm and lengths of up to several micrometers. Elemental analysis gives the atomic ratio of Cu:Fe:S of 1:1.04:2.11. The 57Fe Mossbauer spectrum exhibits a six-peak hyperfine magnetic spectrum and a like-splitted line non-magnetic peak. The factors influencing the formation of the CuFeS2 nanorods were discussed.

Preparation of TiO2 powders with different morphologies by an oxidation-hydrothermal combination method

Ultrafine powders of TiO2 with different morphologies were prepared by a combination method of Ti-H2O2 oxidation-hydrothermal growth. Both oxidation and gel (TiO2·xH2O) formation were performed at room temperature. Hydrothermal treatment was carried out at 140 to 200 °C. The results show that the pH value, reaction temperature and time, and the nature of additives can affect the particle shapes. The effects of hydrothermal parameters on the formation of crystalline phase are also discussed.

Novel polyol route to nanoscale tin sulfides flaky crystallines

Abstract A novel mild solution route, polyol route, was developed to synthesize nanoscale tin sulfides (SnS and SnS 2 ) flaky crystallines. XRD procedure reveals that the products are well crystallized. TEM observation shows that the products are of uniform flaky structure with irregular drapes. And the possible formation mechanism is also discussed.

Hydrothermal deposition of magnetite (Fe3O4) thin films

Magnetite (Fe3O4) thin films (0.2 μm) have been prepared by hydrothermal treatment of iron(III) nitrate solution in the presence of reduced iron powder and urea in the temperature range 140–200 °C for 2–6 h. The resulting films with a black appearance are homogeneous without visible pores, and the average grain size for Fe3O4 on Si(100) and α-Al2O3 is 50 and 150 nm, respectively. The films deposited on Si(100) and α-Al2O3 have saturation magnetization 456 and 448 emu/cm3, and coercivity 470 and 450 Oe, respectively.