Being the hot stabilization succession forma alumina and the succession forma

摘要

PROBLEM TO BE SOLVED: To provide a transition-type alumina stable at high temperature and resistant to the transformation to α-alumina even at a high temperature exceeding 1300°C and provide its production process. ;SOLUTION: A block of aluminum metal is placed on an α-alumina block composed of Al₂O₃ and about ≤1wt.% of MgO based on the Al₂O₃ and the assembly is intensely heated by applying a combustion gas flame to the boundary of the α-alumina and the metallic aluminum or thereabout. The aluminum and a relatively small amount of magnesium evaporated by this process are reacted with oxygen in air to form a transition-type alumina containing a small amount of magnesium in the crystal structure. The transition-type alumina produced by this process is essentially a single crystal resistant to the transformation to α-alumina even at a high temperature exceeding 1300°C, especially exceeding 1400°C and keeps the transition-type crystal form such as δ-alumina or θ-alumina.;COPYRIGHT: (C)1998,JPO