| 摘要 |
Sub-micron sized powders of the ceramic metal oxides such as zirconia, alumina, titania, etc. are produced by precipitation upon mixing aqueous or aqueous/organic solutions of salts of the corresponding metal(s) with substantially 95% solutions of ammonia donors such as hexamethylenetetramine which are capable of reacting with water to give ammonia. The precipitates are treated with an alkali metal hydroxide to remove adsorbed organic matter, neutralized after completion of this treatment with acid, then washed with ammoniated water to remove any residual soluble salt and/or organic matter, dried, and calcined. The powders thus produced are readily sintered to high density ceramic bodies after conventional pressing or casting into a desired shape. The process is especially suited to the production of zirconia powders, either pure or doped with conventional stabilizing oxides such as yttria, magnesia, or lime. In a typical example, a zirconia powder doped with about 5% by weight of yttria is prepared by adding a solution of zirconium oxychloride and yttrium chloride in water to a solution of hexamethylenetetramine in 95% ethanol. After alkali treatment, neutralization, and washing as described above, drying at 105 DEG C., and calcining at 800 DEG C. for two hours, the powder is pressed at 5000 psi (34 MPa) into a green body, which after one hour of sintering at 1600 DEG C. has a density of 98.9% of theoretical. |
