NMR characterization of postcure temperature effects on the microstructures of Blackglas (TM) resin and ceramic

Blackglas(TM) is a novel siliconoxycarbide ceramic material with high level s of carbon incorporated in the atomic structure. This material has potenti al in the fabrication of low cost ceramic matrix composites with high tempe rature capability. Here we study the relationship between the microstructur e of Blackglas(TM) resins and ceramics and the postcure temperature using s olid-state NMR to determine explicitly the microstructure evolution from re sin to ceramic. In this study, Si-29 solid-state NMR reveals a dependence b etween the postcure temperature and the microstructure of the resin. which then effects the resulting ceramic structure. The postcure temperature that appears to give optimal mechanical and oxidative properties of Blackglas(T M) ceramic is around 150 degrees C. For a resin postcured at 250 degrees C, the incorporation of oxygen into the resin network, and thermal redistribu tion reactions between Si-H and Si-O bonds, results in a dramatic and detri mental change of microstructure compared to that of resins postcured at 100 degrees C and 150 degrees C. (C) 2000 Elsevier Science B.V. All rights res erved.