Thermal Evolution of Three Selected Preceramic POSSs Into Ceramic Materials

摘要

Three polyhedral oligomeric silsesquioxanes (POSSs), OctaTetraMethylAmmonium-POSS (OTMAP), DodecaPhenyl-POSS (DPP), and OctaMethyl-POSS (OMP) were heated to explore their potential as preceramic POSSs for ceramic materials, under a three-step pyrolysis technique (25-500 A degrees C/4 h, 500-1000 A degrees C/6 h and 1000-1500 A degrees C/8 h, 10 A degrees C/min in N-2). The chemical and structural evolutions were carefully characterized by TG-DTA, XRD, FTIR and SEM. The OTMAP system was crystalline at all steps, and was mostly transformed into cristobalite at 1500 A degrees C. While, the other two systems produced amorphous silica-based phases (ASBPs) in the first and second steps. In the third step, the DPP with Si-C and Si-O bonds was transformed into crystalline SiC and ASBPs, and OMP with Si-C and Si-O bonds was converted to only ASBPs. Such different transformations between DPP and OMP could be ascribed to their distinct original molecular structures and POSS-dependent chemical evolution.