| 摘要 |
A ceramic is used for the bodies of electromagnetic pumps for strongly reactive molten metals, offering an extremely low thermal conductivity and an enhanced resistance to the aggressive attack of very reactive molten metals such as aluminium and its refining alloys. The ceramic consists of a base with a very high porosity formed from silico-aluminous fibres incorporated in a mixture of tabular alumina and calcium aluminate in which the surface pores are closed by a double impregnation made up of a very thin layer itself coated with a glazed skin, both of which are resistant to attack by the molten metal.The process used for the application of the double protective layer onto the ceramic is also claimed and consists of applying a thin layer of boron nitride or molybdenum disulphide followed by a glazed skin coating of dilute phosphoric acid, mixed with an oxide of very high enthalpy such as alumina or chromium oxide. |
