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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.

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Synthesis and Oxidation of Nanocrystalline HfB 2 . -Nanocrystalline HfB 2 particles with the hexagonal structure are synthesized by reaction of liquid HfCl 4 with NaBH4 (autoclave, 600°C, 12 h). The samples having an average particle size of 25 nm are characterized by powder XRD, TEM, XPS, and TGA-DTA. The oxidation of nanocrystalline HfB2 in flowing air starts at a temperature of 400°C. -(CHEN, L.; GU, Y.; SHI, L.; YANG, Z.; MA, J.; QIAN*, Y.; J.

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