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The synthesis and growth of hexagonal boron-nitride crystallites at low temperature were investigated by carrying out in a lithium bromide (LiBr) melt in 600°–700°C. Transmission electron microscopy study showed that the product obtained at 650°C was composed of two-dimensional plates having an average thickness of about 80 nm and widths from about 400 nm to several micrometers. The molten salt was found to have a strong effect on the crystal growth. The morphology of the crystallites changed from spherical particles to two-dimensional plates when LiBr was used as a crystallization medium. Products were also characterized by X-ray powder diffractions, Fourier Transformed infrared, FESEM/energy dispersive X-ray spectroscopy, and selected area electron diffraction. Possible formation mechanism was also discussed. [ABSTRACT FROM AUTHOR]

α-silicon nitride nanorods have been synthesized through solid-state reduction–nitridation of silica using NaNH2 as both a reductant and a nitriding reagent. X-ray powder diffraction patterns show that the products have a hexagonal phase with lattice parameters a=7.767 Å and c=5.630 Å. Transmission electron microscopy reveals that the as-synthesized products are pure nanorods with an average size about 30 nm in diameter and 400 nm in length. X-ray photoelectron spectra indicate that the molar ratio of Si/N is 2.988:4. Fourier-transform infrared spectrum yields a strong Si–N absorption at 926 cm−1 that may be a red shift due to size effect. [ABSTRACT FROM AUTHOR]