Influence of Carbon Source on the Synthesis of AlN Powder from Aluminum Polynuclear Complexes

Abstract

Effect of carbon on the synthesis of AlN powder from aluminum polynuclear complexes was investigated. Aqueous solutions of basic aluminum chloride and glucose were used as starting materials. C/Al molar ratio was varied to investigate the effect on the reactivity of nitridation and particle size of synthesized AlN powder. The structure of the solution was investigated by ²⁷Al and ¹³C-NMR spectroscopy. It was found that reactivity of nitridation took a maximum value at 1.8-2.0 of C/Al molar ratio and thereafter decreased gradually. This indicates that excess carbon inhibits the transportation of reaction gases at a gap among the particles. In this reaction system, C/Al molar ratio for the maximum reactivity nitridation is much smaller than that in the alumina-carbon black mixture system. Furthermore, this value is closer to the theoretical value for a complete nitridation reaction. These results suggest that carbon in our system is distributed more homogeneously than that in the alumina-carbon black mixture system. The particle size of the synthesized AlN powder decreases with increasing C/Al molar ratio. Obviously, carbon has a strong effect on the particle size of γ-alumina, which is formed as an intermediate in the nitridation process, and prevents the grain growth of the synthesized AlN particles. It was found that aluminum polynuclear complex and glucose formed a precursor in the solution.