High Thermal Conductivity in Multiphase Liquid Metal and Silicon Carbide Soft Composites

Thermal interface materials based on room temperature liquid metals (LMs) are promising candidates for improving thermal management of flexible electronics, microelectronics packaging, and energy storage devices. However, use of these materials is limited by their corrosivity and reactivity. Here, the fabrication and thermal characterization of multiphase soft composites consisting of LM and non-reactive silicon carbide (SiC) particles that are either uncoated or Ag-coated (Ag-SiC) are demonstrated. The LM-SiC (and LM-Ag-SiC) mixtures show thermal conductivities approaching 50 W m^–1 K^–1 at 40 vol% particles. Corrosion issues with aluminum-based components are addressed through a multiphase composite consisting of hybrid LM-Ag-SiC fillers in a silicone oil matrix. This composite achieves an effective thermal conductivity of 9.9 W m^–1 K^–1 with a particle:LM:oil volumetric ratio of 30:20:50 (or intrinsic thermal conductivity of 17 W m^–1 K^–1 when accounting for contact resistance). It is shown that the Ag-coating plays a critical role in these oil-based composites by preventing LM de-wetting during blending. Upon mechanical compression, the LM thermally-bridges the solid fillers together within the oil matrix and thereby improves thermal performance. This insight into processing of LM-based materials opens additional avenues for designing thermally conductive soft composites.