| 摘要 |
PURPOSE:To prevent the surface deterioration by forming the inner layer of a specific material and the outer layer containing metallic Si and a sintering auxiliary on the surface of the formed products. CONSTITUTION:A starting mixed powder consisting of 70 to 100wt.% of Si3N4 powder and 1 to 40wt.% of sintering auxiliaries are press compacted a formed product. Then, a ceramic powder such as boron nitride is dispersed in a dispersing agent such as ethanol to prepare a slurry and the formed product is dipped in the slurry to form coating film. Then, the dispersing agent is removed to provide the inner layer of 1 to 3 mm thickness. Further, 30 to 90wt.% of metallic Si and sintering auxiliaries are dispersed in the medium such as toluene and the formed product provided with the inner layer is immersed in the toluene dispersion to form the outer layer. The coated product is heated to decompose the organic substances, then heated in vacuum in N2 atmosphere at 1,000 to 1,500 deg.C to convert the metallic Si into Si3N4, then sintered at 1,500 to 2,000 deg.C. Then, the product is cooled down, the inner and outer layers are peeled off, thus the Si3N4 sintered product is obtained without surface deterioration. |
