Electrically insulating thermal interface materials with magnetic field-aligned alumina-coated carbon fibers

Polymer composites with high through-plane thermal conductivity and electrical insulation properties are in high demand as thermal interface materials (TIMs) for highly integrated electronics to enhance heat dissipation. However, technical difficulties in pre-controlling the alignment of fillers limit the effective enhancement of thermal conductivity in composite TIMs. Additionally, achieving both high thermal conductivity and electrical insulation performance presents a significant challenge due to their inherent incompatibility. In this study, vertical alignment of O 2  plasma treated mesophase pitch-based carbon fibers coated with Al 2 O 3 (V-Al 2 O 3 @PCF) within polyvinyl alcohol (PVA) was successfully achieved, which integrates functionalities of high through-plane thermal conductivity and electrical insulation. The resulting V-Al 2 O 3 @PCF/PVA composite exhibited an impressive through-plane thermal conductivity of 22.5 W m -1  K -1 , which is 150 times higher than that of pure PVA. This enhancement is attributed to the effective alignment of PCF, which, due to their diamagnetism-induced anti-magnetic forces, overcome gravitational energy and realign vertically. The Al 2 O 3 coating effectively reduces electronic migration between the PCF, allowing the V-Al 2 O 3 @PCF/PVA composite to exhibit a high electrical resistivity of 1.5 × 10 3 Ω·cm. In the application for cooling high-power electronics, the V-Al 2 O 3 @PCF/PVA composite reduced the temperature of LED by 10.2 °C, indicating its significant potential for applications in electronic packaging.