Production process of composite metal oxide
AssigneeToyota Jidosha Kabushiki Kaisha
InventorsShinichi Takeshima, Akio Koyama
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Abstract
A process for producing a composite metal oxide of an acidic metal oxide and a basic metal oxide, wherein the process comprises (a) providing an aqueous solution containing a colloidal particle of the acidic metal oxide and a salt of the basic metal, (b) adjusting the pH of the aqueous solution to a pH at which a part of the basic metal dissolves in the aqueous solution, the remaining of the basic metal precipitates as a hydroxide and has a positive zeta potential, and the colloidal particle of the acidic metal oxide is not dissolved and has a negative surface potential, and then maintaining this pH over a predetermined time to obtain a precursor of the composite metal oxide, and (c) drying and firing the precursor of the composite metal oxide obtained.
Claims9
A process for producing a composite metal oxide of an acidic metal oxide and a basic metal oxide, the acidic metal oxide having an electronegativity as a metal oxide of more than 2.80, and the basic metal oxide being an oxide of a basic metal selected from the group consisting of a rare earth and an alkaline earth metal, wherein the process comprises:
- (a) providing an aqueous solution containing a colloidal particle of said acidic metal oxide and a salt of said basic metal,
- (b) adjusting the pH of said aqueous solution to a pH of 7 to 9 at which 0.1 mol % to 5 mol % of said basic metal dissolves in said aqueous solution, the remaining of said basic metal precipitates as a hydroxide and has a positive zeta potential, and the colloidal particle of said acidic metal oxide is not dissolved and has a negative zeta potential, and then maintaining this pH over a predetermined time to obtain a precursor of said composite metal oxide, and
- (c) drying and firing the precursor of said composite metal oxide.
Dependencies are inferred from the claim text.