PURPOSE: To improve the sinterability of alumina by adding seeds to precipitated Al(OH)3: particles, crushing the particles, classifying the crushed particles to separate coarse particles, calcining the fine particles and washing the product.
CONSTITUTION: An alkali aluminate is hydrolyzed to precipitate Al(OH)3 particles having a soda content of ≤500ppm in terms of Na, a silica content of ≤40ppm in terms of Si and a boehmite conversion ratio of ≤25%. The Al(OH)3 particles are incorporated with 0.1-8.0wt.% (based on the total crushing component) of α-Al2O3 having an average particle diameter of ≤0.5μm as a seed. The mixture is crushed and classified to obtain a fraction having an average particle diameter of ≤5×m and containing <0.1wt.% (based on the total fraction) of particles having particle diameter of ≥10μm. The Al(OH)3 particles are calcined at 1000-1200°C for several min to ten odd hours, washed with hot water or a mineral acid to remove the soda component, dried and crushed to obtain an extremely easily sinterable Al2O3 having a BET specific surface area of ≥10m2/g and consisting of the single phase of α-Al2O3.
ARAKAWA KAZUHISA
SUDA YASUNORI
SHIBUSAWA SUSUMU
Next Patent: PRODUCTION OF EASILY SINTERABLE ALUMINA FINE PARTICLE