SBIR Phase I: Preparation of Ultrapure Aluminum Nitride from a Preceramic Lewis Acid-Base Adduct Synthesized in an Ambient Temperature Chloroaluminate Molten Salt

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*** 9660631 Carter This Phase I Small Business Innovation Research project addresses the bulk synthesis of aluminum nitride (A1N) precursors utilizing acid-base chemistry in an ambient temperature chloroaluminate molten salt. The molten salt is composed of a mixture of aluminum chloride (AlCl3) and trimethylphenylammonium chloride (TMPACl) which forms a liquid tetrachloroaluminate below room temperature. AlN precursors will be formed as Lewis acid-base adducts containing 1:1 ratios of Al to N. Precursor stoichiometry will be fixed by the inherent nature of the Lewis acid-base interaction between nitrogenous bases such as ammonia and hydrazine and heptachlorodialuminate, the predominant Lewis acid in acidic melts. The proposed approach differs from those relying on formation of a polymeric precursor in that it will result in easily handlable solid preceramic materials of the exact stoichiometry required in the final product. The preceramic material is prepared such that no carbide or oxide contamination is introduced into the final product. The proposed technology for production of bulk aluminum nitride in highly pure form will find use immediately in electronics applications, where A1N is used as a heat dissipation medium and substrate material. It is also used in non-electronic applications, e.g., evaporation boats. Annual production of A1N was approximately 120-130 tons in 1993. A substantial driving force exists, therefore, to find alternative, cost-effective methods to produce this material. ***