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Dense silicon carbonitride ceramics by pyrolysis of cross-linked and warm pressed polysilazane powders



Journal of the European Ceramic Society 19 (1999), Nr.16, S.2789-2796
ISSN: 0955-2219
Fraunhofer INT ()
silicon carbonitride; precursors-organics; warm pressing; porosity; Si3N4; SiC

This study reports on the densification and pyrolysis behaviour of cross-linked poly(hydridomethyl)silazane powders. The influence such as cross-linking temperature and annealing time of the polymer powders on the compaction behaviour under cold and warm pressing conditions is discussed. The degree of cross-linking is determined by thermo-mechanical analysis (TMA). The pyrolysis behaviour is monitored by thermo-gravimetric measurements combined with mass spectroscopy (TG-MS). Pyrolysis at 1100°C in Ar results in crack free non-crystalline silicon carbonitride with varying compositions according to compaction / pressing conditions of the powders. The residual open porosity is significantly reduced from 10 - 15 vol% in the cold pressed samples to 1.3 - 5 vol% found in the warm pressed samples. Warm pressed samples also exhibit a by 5 wt% lower weight loss during pyrolysis up to 1300°C. This is explained by a reduced methane evolution during the polymer-to-ceramic conversion and is in accordance with the higher carbon content in the warm pressed samples.