Search

Titanium silicides were synthesized by co-reducing silicon tetrachloride and titanium tetrachloride with different metal reductants (Na, Mg, Zn and Al) in an autoclave at 650 °C. The X-ray diffraction patterns indicated that the obtained titanium silicides could adopt different structures. The orthorhombic titanium disilicide was obtained when the reductant was metallic sodium. However, the hexagonal titanium silicide (Ti5Si3) was obtained when using Mg, Zn and Al. Transmission electron microscope images showed that the average particle sizes of the samples were about 60, 40, 30 and 25 nm in diameters, respectively. It is suggested that the different reaction activities of the reductants resulted in the different titanium silicides. [Copyright &y& Elsevier]

Nanocrystalline chromium disilicide was synthesized by co-reducing anhydrous chromium trichloride and sodium fluorosilicate with metallic potassium at 650 °C in an autoclave. X-ray powder diffraction pattern indicated that the product was hexagonal CrSi2. Transmission electron microscope images showed that the sample consisted of particles with the diameters of 20–50 nm and an average diameter of about 35 nm. TGA and DTA indicated that the oxidation of CrSi2 began to proceed at 700 °C in air, and only about 8.6 wt.% of the sample was oxidized in the surfaces of the particles below 1000 °C. It had high thermal oxidation stability due to the formed protective layer. [Copyright &y& Elsevier]

Chromium silicide (Cr3Si) nanorods were successfully synthesized using anhydrous chromium trichloride and silicon tetrachloride as starting materials via a co-reduction route at 600 °C in an autoclave. X-ray powder diffraction pattern indicated that the product was cubic Cr3Si (a=4.555 Å). Transmission electron microscope images indicated that the sample consisted of single-crystalline nanorods with a diameter of 40–80 nm, an average length of about 600 nm and a maximum length of about 1.0 μm. The oxidation of Cr3Si began to proceed at the temperature of 650 °C in air, but the product had a high thermal oxidation stability below 1000 °C due to the formed protective layer. [Copyright &y& Elsevier]

Nano-crystalline vanadium disilicide was successfully synthesized using vanadium tetrachloride and silicon as starting materials via reduction–silication route at 650 °C in the molten salt solution of magnesium chloride and sodium chloride in an autoclave. X-ray powder diffraction patterns indicated that the product was hexagonal VSi2 (a=4.572 A˚, c=6.372 A˚). Transmission electron microscopy images showed that the particle size of the product was in the range of 40–60 nm in diameter. There was a strong absorption peak at 271 nm in the UV-Vis absorption spectra. The oxidation of nano-crystalline VSi2 began to proceed at the temperature of 400 °C in air. But the product had high thermal oxidation stability below 1000 °C. It can be used as an antioxidation coating material. [Copyright &y& Elsevier]

Nanocrystalline hafnium diboride (HfB2) has been prepared by the reaction of HfCl4 with NaBH4 at 600 °C in an autoclave. The X-ray powder diffraction (XRD) pattern can be indexed as hexagonal HfB2 with the lattice constants of a=3.146 and c=3.456 A˚. The transmission electron microscopy (TEM) image shows a particle morphology with an average size of 25 nm. The selected area electron diffraction (SAED) pattern confirms the presence of hexagonal HfB2. The oxidation behavior of HfB2 is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). [Copyright &y& Elsevier]

Titanium diboride (TiB2) has been synthesized via a benzene-thermal reaction of metallic sodium with amorphous boron powder and titanium tetrachloride at 400 °C in an autoclave; the temperature was much lower than that of traditional methods. The X-ray diffraction (XRD) pattern can be indexed with the hexagonal cell of TiB2 and the lattice constants a=3.027 and c=3.228 A˚. X-ray photoelectron spectroscopy (XPS) results show the mole ratio of Ti:B as 1:1.766. Transmission electron microscope (TEM) images indicate that the average particle size is in the range of 15–40 nm in diameter. [Copyright &y& Elsevier]

Abstract: V2O3 and VN nanocrystals have been synthesized by the decomposition of the precursor NH4VO3 and following nitridation in an autoclave with metallic Na flux at 450–600°C. X-ray powder diffraction (XRD) recorded the evolution process of the reaction from precursor NH4VO3 to hexagonal V2O3 and then to NaCl-type VN. In addition, the products were characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). [Copyright &y& Elsevier]