CONDENSATION POLYMERIZATION OF TETRAKIS(ETHYLAMINO)SILANE AND ITS THERMAL-DECOMPOSITION TO SI3N4/SIC CERAMICS

The polymer obtained from condensation polymerization of Si(NHEt)4 has been characterized by using Si-29 and C-13 solid-state NMR spectroscopy, FTIR, and elemental analysis and by analysis of the condensation products. The decomposition of this polymer to ceramic products has been studied by heating the polymer to 500 and 800-degrees-C in vacuo and characterizing the solid products by using Si-29 MAS, C-13 MAS, and H-1 CRAMPS solid-state NMR spectroscopy, FTIR, and elemental analysis. The condensable gaseous products of the decomposition were isolated and analyzed quantitatively by using FTIR. The solid-state NMR studies suggest a predominantly (SiN4) local environment for the silicon atoms as well as free carbon in the 800-degrees-C product. After heating to 1500-degrees-C for 4 h in an argon atmosphere, beta-SiC, alpha-SiC, and graphite were the eventual crystalline products. Heating at 1600-degrees-C in N2, however, produced mainly alpha-Si3N4 and graphite.