Yunle Gu

A low temperature synthesis of crystalline B4C ultrafine powders

Abstract B 4 C ultrafine powders were successfully synthesized at 450 °C through a new co-reduction route. The synthesis was carried out in an autoclave by using BBr 3 and CCl 4 as the reactants and metallic Na as the co-reductant. The X-ray powder diffraction pattern and Raman spectra indicate the formation of B 4 C. An atomic ratio of B to C of 4.09:1.0 was determined from X-ray photoelectron spectra. Transmission electron microscopy images shows that typical B 4 C crystallites are composed of uniform ultrafine spherical and rod-like particles.

Low-temperature route to nanoscale P 3 N 5 hollow spheres

Nanoscale hollow spheres of amorphous phosphorus nitride (P 3 N 5 ) were synthesized by reacting PCl 3 with NaN 3 at 150-250 °C. Transmission electron microscope images show that the hollow spheres have a diameter of 150-350 nm, and the thickness of the shell is 20 nm. A very small amount of curly films were also found in the sample prepared at 150 °C. The infrared spectrum indicates a high degree of purity. X-ray photoelectron spectroscopy indicates the presence of P and N, with a molar ratio of 1:1.62 for P:N. Ultraviolet-visible absorption spectroscopy shows an absorption band at 265-315 nm. Under photoluminescent excitation at 230 nm, the P 3 N 5 emits ultraviolet light at 305 nm. With a band gap of 4.28 eV, the products may be a wide gap semiconductor. A possible mechanism and the influence of temperature on the formation of the hollow spheres are also discussed.

A co-reduction synthesis of superconducting NbC nanorods

NbC nanorods with diameters of 50–150 nm were successfully synthesized through a new chemical route by using NbCl5 and hexachlorobutadiene (C4Cl6) as Nb and C sources, and Na metal as the reductant at 600 °C in an autoclave. This reaction temperature is much lower than that used in traditional methods. The as-prepared NbC nanorods were characterized by x-ray powder diffraction, transmission electron microscopy and x-ray photoelectron spectra. Magnetization measurement indicated that the NbC nanorods have a superconducting transition at 12.3 K.