Dense alumina articles prodn - by de-aerating alumina suspension,moulding or coating substrate drying and sintering

摘要

Shaped articles for use as refractory materials and in electronics consisting of or coated with hih density Al2O3 are made by (a) removing air from a liquid esp. aq. suspension contg. 60-85 wt. % Al2O3 powder having a = 1 (2-15) m2/g surface and a deflocculant esp. HNO3, HCl, AcOH or oxalic acid, (b) moulding the suspension or applying it to a substrate, (c) drying the moulded suspension or coating at room or moderately raised temp. and (d) sintering the moulded or coated article at = 1100 (1250-1450) esp. 1400 degrees C until the density of the Al2O3 has reached =95% of the theoretical value. Pref. suspension is moulded and dried at least partly, in a porous mould or applied to an Al2O3, ZrO2 or Fe substrate as an opt. 3 mu thick layer. In a modified process, 2 substrates may be bonded through an Al2O3 layer.