Alpha-alumina-coated substrates for sepn. membranes etc. - by coating with colloidal solns. of hydrolysed aluminium beta-di:ketone complexes, and heating to at least 900 deg. C

摘要

Prodn. of alpha-alumina-coated substrates (I) involves coating the substrates with colloidal solns. (II) of condensed Al/beta-diketone complexes. These solns. are obtd. by reaction of hydrolysable Al cpds. of formula RR'R''Al (III) (with R, R', R''' = 1-8C alkyl, alkoxy or acyl, or anions, pref. nitrate, perchlorate, chloride or sulphate) with beta-diketones of formula R1-CO-CHR2-CO-R3 (IV) (with R1, R2, R3 = H, or 1-4C alkyl or alkoxy) in inert solvent, followed by hydrolytic condensn. of the complex obtd. using at least the amt. of water required for complete hydrolysis and sufficient solvent to give a colloidal soln.; the coated substrate is dried and heated to at least 900 deg.C to produce crystallisation. USE/ADVANTAGE - (I) are useful as microporous coated substrates for the prodn. of ultrafiltration or gas-sepn. membranes, or support materials for catalysts and enzyme indicators. The process enables substrates of various types and surface structures to be coated with alpha-alumina particles with narrow particle size distribution and controlled size, even in the sub-micron range; the regular arrangement of the particles gives a narrow pore size distribution, with dia. in the range below 10 nm for sepn. membranes.