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Original Articles

Crystallisation kinetics of amorphous Si–C–N ceramics: Dependence on nitrogen partial pressure

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Pages 1485-1493 | Received 10 Jul 2009, Accepted 06 Oct 2009, Published online: 08 Apr 2010
 

Abstract

The crystallisation kinetics of amorphous precursor-derived ceramics of composition Si26C41N33 is investigated as a function of temperature and nitrogen partial pressure using X-ray diffractometry. Isothermal annealing at a pressure of 1 bar leads to simultaneous crystallisation of Si3N4 and SiC, while only crystalline SiC is formed with annealing at a reduced pressure of 1 mbar. Rate constants of crystallisation are determined using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism. For temperatures below 1700°C, crystallisation rates are significantly higher for annealing at 1 mbar compared to 1 bar. For an explanation of the results, a model is proposed, which is based on diffusion-controlled nucleation and growth of crystalline Si3N4 and SiC in an amorphous matrix combined with thermal decomposition of Si3N4 at high temperatures.

Acknowledgements

The authors thank P. Gerstel (MPI Stuttgart) for supplying the precursor ceramics and E. Ebeling for ceramographic preparation. Funding by the Deutsche Forschungsgemeinschaft (DFG) is gratefully acknowledged.

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