.theta.-alumina powder, preparation thereof and magnetic recording medium
AssigneeSumitomo Chemical Company, Limited
InventorsShoji Sugimoto, Yoshiaki Takeuchi, Hiroshi Umezaki
Life of this patent
Estimating the term…
Abstract
Alumina powder having a .theta.-alumina content of at least 70% by weight and an average primary particle size at least 0.1 .mu.m and containing a tungsten compound in an amount of 0.1 to 5% by weight in terms of tungsten oxide based on alumina can be used as an abrasive for a magnetic recording medium having good properties.
Claims8
.theta.-Alumina powder having a .theta.-alumina content of at least 70% by weight and an average primary particle size of at least 0.1 .mu.m and containing a tungsten compound in an amount of 0.1 to 5% by weight in terms of tungsten oxide based on alumina.
A method for preparing .theta.-alumina powder which comprises calcining, at a temperature of 1100.degree. to 1300.degree. C., an aluminum compound containing tungsten or a tungsten compound in an amount which of 0.1 to 5% by weight in terms of tungsten oxide based on alumina after calcination to obtain alumina powder having a .theta.-alumina content of at least 70% by weight and an average primary particle size of at least 0.1 .mu.m and containing a tungsten compound in an amount of 0.1 to 5% by weight in terms of tungsten oxide based on alumina.
Dependencies are inferred from the claim text.