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Nano-sized amorphous boron powders were synthesized by active dilution self-propagating high-temperature synthesis (SHS) method at temperatures ranging from 700°C to 850°C in a SHS furnace using Mg, B2O3 and KBH4 as raw materials. Samples were characterized by X-ray powder diffraction (XRD), Laser particle size analyzer, Fourier transform infrared spectra (FTIR), X-ray energy dispersive spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission TEM (HRTEM). The boron powders demonstrated an average particle size of 50nm with a purity of 95.64wt.%. The diluter KBH4 played an important role in the active dilution synthesis of amorphous nano-sized boron powders. The effects of endothermic reaction rate, the possible chemical reaction mechanism and active dilution model for synthesis of the product were also discussed. [ABSTRACT FROM AUTHOR]

Boron nitride hollow spheres were synthesized by the reaction of BBr3 and NaNH2 at room temperature; X-ray powder diffraction pattern could be indexed as hexagonal BN with the lattice constants of a=2.482 and c=6.701 A˚; high-resolution transmission electron microscopy image showed the hollow spheres consisted of BN nanoparticles, with diameter between 80 and 300 nm; a possible formation mechanism of BN hollow spheres was discussed. [Copyright &y& Elsevier]

Mn5Si3 nanocages and nanotubes were successfully synthesized by molten salt flux reaction at 650 °C. The samples were characterized with X-ray powder diffraction and transmission electron microscopy. The influence of the reactants molar ratio of MnCl2 to Mg2Si and reaction temperature on the phases and morphologies of the products were discussed. The possible mechanism of forming Mn5Si3 nanocages and nanotubes is discussed. [Copyright &y& Elsevier]

Nanocrystalline titanium diboride (TiB2) has been prepared by the reaction of TiCl4 with NaBH4 in the temperature range of 500–700 °C in an autoclave. X-ray powder diffraction (XRD) patterns can be indexed as hexagonal TiB2 with the lattice constants of a=3.032 and c=3.229 A˚. Transmission electron microscopy (TEM) image shows particle morphology, with average size of 15 nm for the powder obtained at 600 °C. Selected area electron diffraction (SAED) pattern confirms the prepared hexagonal TiB2. The oxidation behavior of TiB2 is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). [Copyright &y& Elsevier]

Nanocrystalline titanium diboride (TiB2) has been prepared through a reduction–boronation route by using Ti powders and BBr3 as titanium and boron sources, and metallic sodium as reductant at 400 °C. X-ray powder diffraction (XRD) pattern can be indexed as hexagonal TiB2 with the lattice constants of a=3.028 and c=3.223 A˚. Transmission electron microscopy images show particle morphology with average size of 15 nm. Selected area electron diffraction patterns confirm the preparation of the hexagonal TiB2. [Copyright &y& Elsevier]

B4C ultrafine powders were successfully synthesized at 450 °C through a new co-reduction route. The synthesis was carried out in an autoclave by using BBr3 and CCl4 as the reactants and metallic Na as the co-reductant. The X-ray powder diffraction pattern and Raman spectra indicate the formation of B4C. 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 B4C crystallites are composed of uniform ultrafine spherical and rod-like particles. [Copyright &y& Elsevier]

Abstract: Large quantities of boron nitride (BN) nanotubes were synthesized by annealing a catalytic boron-containing porous precursor in flowing NH3 gas at 1180°C. The porous precursor was prepared by self-propagation high-temperature synthesis (SHS) method at 800°C using Mg, B2O3 and amorphous boron powder (α-B) as the starting materials. The porous precursor played an important role in large quantities synthesis of BN nanotubes. The as-synthesized product was characterized by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), Raman, Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HRTEM). Characterization results indicated that the BN nanotubes displayed wave-like inner structures with diameters in the range of 50–300nm and average lengths of more than 10μm. The possible growth mechanism of the BN nanotubes was also discussed. [Copyright &y& Elsevier]