Abstract
Electrically insulating and thermally conductive polymer matrix composites are desirable for industry applications as they improve the reliability of high-performance electronic devices, particularly via heat dissipation in devices loaded with several electronic components. In this study, an aggregated β-Si3N4 filler with randomly oriented grains was produced via combustion synthesis to improve the thermal conductivity of epoxy composites. The thermal conductivities of the prepared composites were investigated as a function of the filler content, and the values were compared to those of composites loaded with commercial β-Si3N4 (non-aggregated). Negligible difference was observed in the thermal conductivities of both types of composites when the Si3N4 content was below 40 vol%; however, above 40 vol%, the aggregated β-Si3N4 filler-loaded composites showed higher thermal conductivities than the commercial β-Si3N4-loaded composites. The aggregated β-Si3N4 filler-loaded composites exhibited isotropic thermal conductivities with a maximum value of 4.7 W m−1 K−1 at 53 vol% filler content, which is approximately 2.4 times higher than that of the commercial β-Si3N4-loaded composites, thereby suggesting that the morphology of the aggregated filler would be more efficient than that of the commonly used non-aggregated filler in enhancing the thermal conductivity of a polymer matrix composite.
Highlights
Insulating and thermally conductive polymer matrix composites are desirable for industry applications as they improve the reliability of high-performance electronic devices, via heat dissipation in devices loaded with several electronic components
boron nitride (BN) possesses a hexagonal crystal structure and exhibits a layerlike structure with a high aspect ratio. Such morphology makes it difficult to obtain a uniform dispersion of BN grains in a composite material, and the resulting composite loaded with BN tends to have an anisotropic thermal conductivity owing to its high aspect ratio[11,12,13,14]
Direction of thermal conductivity β-Si3N4 crystal along the a and c axes are 170 W m−1 K−1 and 450 W m−1 K−115, respectively, which indicates that β-Si3N4, along the c-axis, is theoretically comparable to BN and aluminum nitride (AlN) in terms of theoretical thermal conductivity
Summary
The thermal conductivity of the composites prepared by dispersing the aggregate Si3N4 filler in various proportions was evaluated. No silicon and silica peaks were observed in the inner or outer layers of the product, indicating that the silicon powder successfully reacted with nitrogen to form S i3N4 during the combustion process. The specific surface areas of both powders were observed to be similar the particle sizes differed by a factor of 5 This indicates that the individual β-Si3N4 grains are partially sintered with each other to form an aggregate structure, suggesting that it is this aggregate structure that allows the heat to pass more efficiently through the CA-SN filler compared to the commercially available β-Si3N4 powder. Thermal conductivity of the composites (Wm-1K-1) Relative density of the composites (%)
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