High-Temperature Reactions in the B-Al-Si-N-C System
Boron, in its tetragonal and rhombohedral forms, is characterized by an ability to incorporate a wide spectrum of metals (e.g Si,Y,Zr,Ln,U) and non-metals (C,O,P,As) into the crystal structure whilst still retaining the basic structure type. The present work has extended this by studying the incorporation of nitrogen into boron carbide,and at temperatures in the range 800–1100°C, the solubility is ≈3.8 w/o. At these and higher temperatures, there is a competing reaction whereby the B4C structure is broken down and an amorphous B-N-C product is formed. This resists crystallization even at temperatures as high as 1500°C.
Oxygen is always present as a surface layer on carbide and nitride powders used in high-temperature reactions. Its role in the densification of nitrogen ceramics is well known; the present work describes its role in the formation and densification of Al4SiC4 ceramics.
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- 5.Oscroft, R.J., Korgul, P. and Thompson, D.P., in Proc. 3rd Int. Symp. αCeramic Materials and Components for Enginesβ, ed. V.J. Tennery, pub. The American Ceramic society, 1989, pp. 661–670.Google Scholar
- 6.Perrotta, A.J., Townes, W.D. and Potenza, J.A., Acta cryst., B25, 1223–1229.Google Scholar
- 8.Schwetz, K.A. and Lipp, A, Sci. Ceram., 1980, 10, 149–158.Google Scholar