Directional Construction of Thermal Superhighways with Composite Phase Change Materials for Chip Thermal Management Application

Abstract The thermal management of highly integrated chips under high thermal flux density is hindered by disordered high‐thermal‐conductivity matrices that reduce phonon transport efficiency. To address this challenge, this study employs directional freezing to systematically align multi‐walled carbon nanotubes, thereby establishing efficient thermal conduction pathways. Subsequent vacuum impregnation with the CaCl 2 ·6H 2 O phase change material (PCM) yields a composite material with pronounced anisotropic thermal conductivity—6.86 W·m −1 ·K −1 along the axial direction and 0.08 W·m −1 ·K −1 along the radial direction. This structural design not only enhances axial heat transfer and accelerates thermal equilibrium, but it also significantly suppresses PCM leakage via nanoconfinement and capillary effects, accelerating its phase transition by reducing subcooling to 11.41 °C. When employed for the transient thermal management of CPUs, the proposed material effectively directs heat flow, resulting in a 24 °C reduction in peak core temperature and a 19.5 °C reduction in peak surface temperature. Furthermore, this material demonstrates excellent thermal stability over 20 thermal cycles, with a maximum temperature fluctuation of only 5.2 °C. This study thus presents an effective strategy for the development of high‐performance, structurally controllable PCM‐based thermal interface materials.