Improving through-plane thermal conductivity of PDMS-based composites using highly oriented carbon fibers bridged by Al₂O₃ particles

Efficient thermal interface materials (TIMs) are urgently needed for heat dissipation of high-power density electronics. In this study, vinyl polydimethylsiloxane (PDMS) composites with the spatial alignment of carbon fibers (CFs) bridged by Al₂O₃ particles were fabricated by the flow field. The through-plane thermal conductivity (TPTC) of the composites with 24 vol% CFs and 47 vol% Al₂O₃ loading reached 38.0 W m⁻¹ K⁻¹. The oriented CFs bridged by Al₂O₃ acted as the efficient through-plane thermal conductive network. Furthermore, the effects of shape factor (b/a), spatial angle (γ) of CFs, and CF loading (V_f) on the TPTC were quantitatively discussed by steady-state finite element simulation combined with micro-computed tomography and machine learning. The positive contribution of the increased V_f to TPTC was in competition with the negative contribution of b/a and γ, both of which increased with the increase of V_f. Moreover, b/a exerted more negative effects than γ. The PDMS composites demonstrated excellent thermal stability (T_d = 407.5 °C, CTE = −55.3 × 10⁻⁶ K⁻¹), low compress modulus (1.71 MPa), and hardness (47 (Shore C)), which made them potential candidates for TIMs. This work offers a feasible method to prepare TIMs on large scale and refreshes the thermal conduction mechanism of TIMs by introducing the influencing factors (b/a and γ).