A versatile chemical strategy for ultrafine AIN and Al-O-N powders

A versatile low-temperature chemical approach utilizing an alkoxide-based h ydrazide process was developed for the synthesis of nanometer-size aluminum nitride, oxynitride, and composite powders. The process consists of reacti ng aluminum tri-sec-butoxide and anhydrous hydrazine in acetonitrile at 80 degrees C to yield solid precipitates, which, when dried and heated in argo n, nitrogen, or ammonia, yielded nanosize powders of the desired chemistry. The precursors and products of the reactions were identified by gas chroma tography (GC), chemical analyses, and X-ray diffraction (XRD), while the mo rphology and particle size of the powders were determined by scanning elect ron microscopy (SEM) and transmission electron microscopy (TEM). GC reveale d the release of butyl alcohol due to the reaction of the alkoxide with anh ydrous hydrazine, suggesting the partial replacement (56.5%) of alkoxy grou ps by hydrazide groups (i.e., formation of Al-NHNH2 species). Fourier trans form infrared (FTIR) and Al-27 magic-angle-spinning-nuclear-magnetic-resona nce (MAS-NMR) spectroscopy provided structural insights regarding the chang es in molecular linkages during heating of the precursor and the role of hy drazine in the subsequent nitridation reaction. Hydrazine's critical functi on as a nitride former in the initial stages of formation of the precursor, as well as during heat treatment, was further confirmed by studying its re action with the alkoxide in the presence of controlled amounts of deionized (DI) water. Hydrolysis of the alkoxide while limiting the hydrazide reacti on was found to promote the formation of versatile precursors that lead to oxide, oxynitride, or composite powders containing nanoparticles of the nit ride phase in an oxynitride matrix.