Synthesis and Mechanism of Nanosized AlN from an Aluminum Oleic Emulsion Using Carbothermal Reduction at Low Temperatures

Abstract

Nanosized Al2O3 particles homogeneously dispersed in a matrix of amorphous carbon (a‐C) were prepared by decomposition of an aluminum oleic emulsion at 600°C in Ar. Nanosized aluminum nitride (AlN) grains were prepared by carbothermal reduction and nitridation (CRN) of this Al2O3–a‐C mixture in NH3 using graphite, BN, and alumina crucibles or boats. The phases formed by CRN were identified by X‐ray diffraction analysis. The morphology and grain size of the AlN were determined by transmission electron microscopy. The formation of single‐phase AlN was achieved at temperatures as low as 1150°–1200°C in NH3 using a cylindrical graphite crucible with holes in its two flat faces. Mass spectroscopy (MS) showed that a significant amount of HCN and a minor amount of C2H2 are formed at 500°C by reaction of NH3 with carbon at the decomposition temperature of NH3. A most probable formation mechanism of the AlN from nanosized Al2O3 and a‐C in NH3 is discussed on the basis of MS results and thermodynamic considerations.