Electrical Joining of Silicon Nitride Ceramics

Abstract

The electrical joining of sintered Si,N, ceramics by Joule heating was studied. A mixture of CaFJkaolinite (70/30 wt %) with excellent electroheating characteristics and reactivity with Si,N, ceramics was selected as a joining agent. The optimum conditions for electrical joining were determined using this joining agent. Analysis of the joint obtained under optimum conditions revealed that joining was accomplished by the formation of reaction zones and a joining layer through the mutual diffusion of the components in the joining agent and the sintering aids in the Si,N,. The joint layer was composed of a glassy substance consisting of Ca-AI-Si-Y-0-(F)-(N) and contained a few particles of P-Si,N,. Four-point bend tests indicated that joined bodies could be obtained which maintained a strength of about 300MPa up to 800°C. Finally, a comparative study was made with a joint obtained using furnace heating. These results indicated that the joints obtained using electrical joining were superior to those produced in the furnace.

Energy and environmental research emphasizing low-rank coal: Task 6.2. Joining of advanced structural materials

“…The sintering temperature can be reduced to 1850"-2000°C if Sic is sintered with the addition of small quantities of Al,03 and A1203 + Y203. 24 In addition, reaction sintering has been used by mixing Si and C with Sic powder and heating the mixture to 1400°C to cause the Si and C to react and form Sic, which bonds the aggregate together.…”