PTFE, an effective additive on the combustion synthesis of silicon nitride

Combustion synthesis (CS) Of Si3N4 with the addition of polytetrafluoroethylene (PTFE) was carried out at a relatively low N-2 pressure of 2 MPa. It was found that the additive PTFE promoted the nitridation of Si. The alpha-Si3O4 contents in the periphery of the combustion-synthesized products showed great dependence on the contents of PTFE added in the reactants, which reached 77.7 wt.% with 4 wt.% PTFE addition. The residual silicon in the center of the combustion-synthesized products could be completely nitrided by further heat treatment at 1300 degrees C for 1 h in N-2. The temperature difference between the center and the edge of the samples was responsible for the discrepancy in both phase composition and morphology of the products. (c) 2007 Elsevier Ltd. All rights reserved.