| 摘要 |
PURPOSE:To obtain tough abrasive grains by coating alumina particles contg. water of crystallization limited to a prescribed amt. or less with fine powder of a specified oxide or suboxide and by heating the coated particles. CONSTITUTION:Alumina gel is dried or calcined to obtain alumina particles contg. water of crystallization limited to <=30% of the amt. of Al2O3. The alumina particles are coated with fine powder of at least one of salts of Cr, Ti, Fe, V, Mg, Ga and Rh or impregnated with a soln. of at least one of the salts and heated to 1,150-1,400 deg.C. By this heating, the element forms a solid soln. In the alumina and tough abrasive grains of alumina are obtd. The diffusion coefft. of the element relates to a temp. exponentially and the formation of the solid soln. decelerates remarkably at <1,150 deg.C. When the element has a large ionic radius, it forms no solid soln. at <1,150 deg.C because of insufficient activation energy. The grain size of the abrasive grains is made excessively large at >1,400 deg.C. The pref. heating time is about <1.5hr. The grain size of the abrasive grains is made excessively large by heating for >=1.5hr. |
