Sequential Dual Alignments Introduce Synergistic Effect on Hexagonal Boron Nitride Platelets for Superior Thermal Performance

Abstract

Planarly aligning two‐dimensional (2D) platelets is challenging due to their additional orientational freedom compared to one‐dimensional materials. This study reports a sequential dual‐alignment approach, employing an extrusion printing‐induced shear force and rotating magnetic field‐induced force couple for platelet planarly alignment in a yield‐stress support bath. It is hypothesized that the partial alignment induced by a directional shear force facilitates subsequent axial rotation of the platelets for planar alignment under an external force couple, resulting in a synergistic alignment effect. This sequential dual‐alignment approach achieves better planar alignment of 2D modified hexagonal boron nitride (mhBN). Specifically, the thermal conductivity of the 40 wt% mhBN/epoxy composite is significantly higher (692%) than that of unaligned composites, surpassing the cumulative effect of individual methods (only 133%) with a five‐time more synergistic effect. For 30, 40, and 50 wt% mhBN composites, the thermal conductivity values (5.9, 9.5, and 13.8 W m−1 K−1) show considerable improvement compared to the previously reported highest values (5.3, 6.6, and 8.6 W m−1 K−1). Additionally, a three‐dimensional (3D) mhBN/epoxy heat sink is printed and evaluated to demonstrate the feasibility of device fabrication. The approach will enable the planar alignment of electrically or thermally conducting 2D fillers during 3D fabrication.This article is protected by copyright. All rights reserved