| 摘要 |
1367763 Titanium-tungsten mixed oxide sols and gels; titanium-tungsten carbide UNITED KINGDOM ATOMIC ENERGY AUTHORITY 1 Oct 1971 [5 Oct 1970] 47314/70 Heading C1A A sol or gel containing tungsten and titanium oxides is prepared by mixing freshly precipitated tungstic acid or a tungstate with an aqueous solution of a titanium salt. The tungstic acid may be prepared by dissolving the commercial acid cake in, e.g. ammonia and precipitating the acid in the cold. Alternatively ammonium tungstate may be used either in aqueous solution or as a solid. The preferred titanium salt is titanium tetrachloride. The temperature of reaction is not critical and may range from 0‹ to 100‹ C. or higher if an autoclave is used. It is preferred to use ammonium tungstate as the salt source since on drying the sol or gel a homogeneous mixed oxide free from sodium, calcium or other undesirable metals is obtained. Other refractory metals, e.g. tantalum, niobium, chromium and vanadium or non- refractory metals such as cobalt and bismuth may be incorporated into the sol by addition, e.g. as a chloride at any convenient stage in the preparation of the sol. The amount of added metal is not in general above 20% by weight of the titanium and tungsten. The sol may be dried and calcined to form a mixed oxide system. Finely divided carbon may also be introduced into the sol preferably as an aqueous dispersion or as a powder mixed with a wetting agent, prior to evaporation so that on calcining a mixed tungsten-titanium carbide is formed. |
