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

Powders of nanocrystalline aluminum nitride (AlN) and boron nitride (B N) were prepared via a chemical route. Precomposite gels, which were o btained from ammonolysis of aqueous solutions of boric acid, urea, and aluminum chloride hexahydrate, were thermally processed to produce Al N-BN nanocomposite powders with a wide range of compositions. These po wders were characterized by x-ray diffraction (XRD), transmission elec tron microscopy (TEM), high resolution transmission electron microscop y (HRTEM), scanning electron microscopy (SEM), and Fourier transform i nfrared spectroscopy (FTIR). The structure, morphology, and crystallit e size of the powders are correlated with the compositions and process ing temperature. Normal and abnormal grain growth are discussed.