Member, American Ceramic Socicty.
Role of Interfacial Carbon layer in the Thermal Diffusivity/Conductivity of Silicon Carbide Fiber-Reinforced Reaction-Bonded Silicon Nitride Matrix Composites
Article first published online: 11 JUL 2005
Journal of the American Ceramic Society
Volume 75, Issue 2, pages 334–340, February 1992
How to Cite
Bhatt, H., Donaldson, K. Y., Hasselman, D. P. II. and Bhatt, R. T. (1992), Role of Interfacial Carbon layer in the Thermal Diffusivity/Conductivity of Silicon Carbide Fiber-Reinforced Reaction-Bonded Silicon Nitride Matrix Composites. Journal of the American Ceramic Society, 75: 334–340. doi: 10.1111/j.1151-2916.1992.tb08183.x
W. K. Tredway—contributing editor
Supportcd jointly by the NAS/l-l.ewie Reeearch center, Cleveland, OH, and by thc I hermuphysical Rewarch Laboratory ul the Advanccd High Temperatiire Matet-ials Laboratory at Vlrginia Polytechnic Inalitu(e and State Unibcrsilv.
- Issue published online: 11 JUL 2005
- Article first published online: 11 JUL 2005
- Manuscript No. 196481. Received August 8. 1991; approved October 22, 1991. Supported jointly by the NASA-Lewis Research Center, Cleveland, OH, and by the Thermophysical Resarch Laboratory of the Advanced High Temperature Materials Laboratory at Virginia Polytechnic Institute and State University.
- silicon nitride;
- thermal conductivity;
- thermal diffusivity;
The role of an interfacial carbon coating in the heat conduction behavior of a uniaxial silicon carbide nitride was investigated. For such a composite without an interfacial carbon coating the values for the thermal conductivity transverse to the fiber direction agreed very well with the values calculated from composite theory using experimental data parallel to the fiber direction, regardless of the ambient atmosphere. However, for a composite made with carbon-coated fibers the experimental values for the thermal conductivity transverse to the fiber direction under vacuum at room temperature were about a factor of 2 lower than those calculated from composite theory assuming perfect interfacial thermal contact. This discrepancy was attributed to the formation of an interfacial gap, resulting from the thermal expansion mismatch between the fibers and the matrix in combination with the low adhesive strength of the carbon coating. In nitrogen or helium the thermal conductivity was found to be higher because of the contribution of gaseous conduction across the interfacial gap. On switching from vacuum to nitrogen a transient effect in the thermal diffusivity was observed, attributed to the diffusion-limited entry of the gas phase into the interfacial gap. These effects decreased with increasing temperature, due to gap closure, to be virtually absent at 1000°C.