Role of Interfacial Carbon layer in the Thermal Diffusivity/Conductivity of Silicon Carbide Fiber‐Reinforced Reaction‐Bonded Silicon Nitride Matrix Composites
作者:
Hemanshu Bhatt,
Kimberly Y. Donaldson,
D. P. II. Hasselman,
Ramakrishna T. Bhatt,
期刊:
Journal of the American Ceramic Society
(WILEY Available online 1992)
卷期:
Volume 75,
issue 2
页码: 334-340
ISSN:0002-7820
年代: 1992
DOI:10.1111/j.1151-2916.1992.tb08183.x
出版商: Blackwell Publishing Ltd
关键词: composites;silicon nitride;thermal conductivity;thermal diffusivity;interfaces
数据来源: WILEY
摘要:
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 100
点击下载:
PDF
(1228KB)
返 回