Thermal Characteristics of CNF and Ni Hybrid Filler Thermal Interface Materials with Aligned Structure

Thermal interface materials are critical components for ensuring efficient heat dissipation in thermal management systems. The current research focus is to fabricate thermal interface materials (TIMs) that demonstrate high thermal conductivity while at low filler loadings. In this study, an aligned, thermally conductive skeleton was fabricated via the freeze casting method, utilizing carbon nanofibers (CNFs) and nickel (Ni) particles. This skeleton was subsequently infiltrated with silicone rubber (SR) to obtain the polymer composite. Within the aligned skeleton, CNFs and Ni particles are densely packed, with the Ni particles acting as conductive bridges between adjacent CNFs. This bridging effect facilitates a substantial enhancement in the overall thermal conductivity with only a minimal addition of Ni. By combining the skeleton’s microstructure with thermal performance, the effects of key parameters on thermal conductivity were systematically investigated. A maximum thermal conductivity improvement of 64.8% was achieved by hybridizing CNFs with a small amount of Ni (1.09 vol%) compared to the CNF-only counterpart. Furthermore, at a low total loading (8.02 vol% CNFs and 1.09 vol% Ni), the composite achieved a thermal conductivity of 3.30 W/(m·K). This value was 47.2% higher than that of a CNF-only TIM and 36.2% higher than that of a composite prepared by common freezing under the same filler composition. Additionally, the incorporation of Ni enhanced the composite’s thermal stability. Moreover, the composite exhibited a favorable combination of enhanced mechanical strength and excellent elasticity.