Method of manufacturing an object of silicon nitride
US4112143A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 18, 1977 |
| Grant date | Sep 5, 1978 |
| Priority date | — |
| Expiry date | Jan 18, 1997 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC04B35/6455
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A method for manufacturing an object of silicon nitride by isostatic pressing of a preformed body of silicon nitride powder utilizing a pressure medium at a temperature sufficiently high to sinter the silicon nitride. The preformed body is subjected to a degassing operation before isostatic pressing. An inner porous layer of a first material and then an outer porous layer of a second material are applied on the preformed powder body. The inner porous layer is transformable, at a temperature below the sintering temperature for silicon nitride, into a pressure medium impermeable layer. The outer porous layer is also transformable into a pressure medium impermeable layer, but at a temperature which is lower than the temperature when the inner porous layer is converted into its pressure medium impermeable form. Thus, the preformed body is first subjected to a degassing and to a heating to the temperature for transforming the outer porous layer into a pressure medium impermeable layer while the inner porous layer is maintained in a porous form. Thereafter the preformed body and the surrounding layers are heated further to the temperature for converting the inner porous layer into its pr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.