COMPOSITIONAL AND THERMAL EFFECTS ON CHEMICALLY PROCESSED ALN-BN NANOCOMPOSITE POWDERS

Powders of nanocrystalline aluminum nitride (AlN) and boron nitride (BN) were prepared via a chemical route. Precomposite gels, which were obtained from ammonolysis of aqueous solutions of boric acid, urea, and aluminum chloride hexahydrate, were thermally processed to produce AlN-BN nanocomposite powders with a wide range of compositions. These powders were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The structure, morphology, and crystallite size of the powders are correlated with the compositions and processing temperature. Normal and abnormal grain growth are discussed.