Thermal conductivity enhancement of platelets aligned composites with volume fraction from 10% to 20%

Abstract

Hexagonal boron nitride (hBN)-filled composites are widely used in electronics for thermal management. In order to enhance the materials heat transport capability, the hBN platelets are expected to be assembled into well-ordered structure. Such structure has been achieved in practice by the magnetic alignment approach. However, this approach is limited to the composites loaded with low volume fraction of platelets (<10%). In this paper, we report the use of combined mechanical and magnetic stimuli to fabricate the well-aligned composites at the volume fraction from 10% to 20%. The platelets in the resulting composites exhibit a high degree of alignment. For instance, in the 10vol.% composite, the angle of 95.3% of platelets is greater than 45°, only ∼5% of platelets falls into the horizontal direction. Thermal conductivity of the composites was investigated experimentally. It exhibited strong correlation with the platelets alignment. The measured thermal conductivity of 10vol.% aligned composite is 74% higher than that of unaligned composite. Thermal conductivity were also analyzed by a theoretical model. Thermal boundary resistance (Rb), arising at the platelets–matrix interface, was extracted by fitting the measured thermal conductivity to model prediction. Rb is found to decrease with the increase of alignment degree. This study suggests that assembling the platelets into well-ordered structure can greatly enhance the heat transport capability due to the formation of conductive networks and the reduction of Rb.