ホットプレス及びPECS焼結時にカーボンと接触していた窒化ケイ素のα/β転移の遅れ

概要

論文の詳細を見る
In the hot-pressing and pulse electric current sintering (PECS) of Si_3N_4, α to β transformation of Si_3N_4 was delayed in the surface of the sintered body.The thickness of the surface layer depended on the sintering conditions and was less than 0.5 mm in this experiment by X-ray analysis.Thin surface layers of 5-20μm including no nitrogen and 60-100μm layers in which the oxygen content changes gradually were observed by EPMA.The no nitrogen layer was thought to be formed by the decomposition of Si_3N_4 resulted from the reaction of Si_3N_4 with carbon or CO gas.The mechanism of the delayed α to β transformation was speculated as follows:A low oxygen partial pressure in the atmosphere vaporized oxygen from the grain boundary liquid phase.The decreased oxygen content in the grain boundary liquid phase made increase the viscosity of the phase.The increased viscosity of the liquid phase might decreased the dissolution/precipitation rate, that is α to β transformation rate, of Si_3N_4 in the surface region.
社団法人日本セラミックス協会の論文
1998-09-01