Boron nitride nanotubes （BN-NTs） with pure hexagonal BN phase have been synthesized by heating ball-milled boron powders in flowing ammonia gas at a temperature of 1200℃. The as-synthesized products were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron energy loss spectroscopy （EELS）. The diameters of nanotubes are in the rage of 40-120nm and the lengths are more than 10μm. EELS result identifies that the ratio of boron and nitrogen is almost 1：1 The growth temperature is a crucial growth parameter in controlling the structure and crystalline of BN-NTs. The nanotubes grown at 1100℃ possesses of a bamboo-like structure, while as the temperature increased to 1200℃, most of the nanotubes exhibited a cylindrical structure. In addition, changing the heating time can control the size of the nanotubes. The gas atmosphere has influence on the yield of BN-NTs during heating process. When heating atmosphere was replaced by nitrogen, the yield of nanotubes was remarkably decreased.
A solvothermal reaction of anhydrous C3N3Cl3 and Li3N using benzene as the solvent has been carried out to prepare crystalline carbon nitrides successfully at 350℃ and 5—6 MPa. X-ray diffraction (XRD) indicated that the major part of our brown sample was mainly composed of a-C3N4 and b-C3N4 with lattice parameters of a = 0. 65 nm, c = 0.47 nm for a-C3N4 and a = 0.644 nm, c = 0. 246 nm for b-C3N4, which match the latest ab-initio calculations quite well. The N/C ratio in the powder is about 0.66. The Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spec-troscopy (XPS) analyses suggested the presence of both sin-gle and double carbon-nitrogen bonds. The kinetics effects of our solvothermal reaction to prepare crystalline carbon ni-trides are also discussed chiefly.
L Qiang, CAO Chuanbao & ZHU Hesun Research Center of Materials Science, Beijing Institute of Technology, Beijing 100081, China
A new electrodeposition system, with a thin nickel wire as the anode, was used to deposit the CN x thin film on Si(100) substrate from a dicyandiamide-saturated solution in acetonitrile at a high potential. During the experiment, when a certain high potential was applied, spark occurred between the Ni wire anode and the Si(100) substrate. The films were characterized by X-ray photoelectron spectroscopy(XPS), Fourier-transform infrared spectroscopy(FTIR), scaning electron microscopy(SEM) and X-ray diffraction(XRD). It was indicated that multiphase of α-C 3N 4, β-C 3N 4 and g-C 3N 4 was obtained in the films. This work is the first attempt to deposit carbon nitride material through a thin nickel wire anode and might provide a new route for preparing pure crystalline C 3N 4.
