Magnetically oriented Fe3O4@BN/self-healing polyurethane composites with vertically aligned structure for enhanced thermal conductivity and self-healing performance

The increasing power density of electronic devices demands materials that combine efficient thermal management with autonomous damage repair. In this study, a magnetic hybrid filler (Fe 3 O 4 @BN) was prepared by loading Fe 3 O 4 particles onto boron nitride (BN) surfaces via a coprecipitation method. The Fe 3 O 4 @BN filler was then incorporated into a self-healing polyurethane (SHPU) matrix, and an external magnetic field was applied to induce a vertically oriented filler network. Results showed that at Fe 3 O 4 @BN contents of 20 wt% and 25 wt%, the ordered structure effectively suppressed phonon scattering, increasing the out-of-plane thermal conductivity of the composite to a maximum of 0.76 W/m·K. Meanwhile, the SHPU matrix provided a thermally triggered self-healing function based on the synergy of reversible Diels–Alder bonds, disulfide bonds, and hydrogen bonds. After healing at 135 °C for 10 min followed by 12 h at 70 °C, cracks were completely repaired. The healed composites recovered most of their original tensile strength, elastic modulus, elongation at break, and thermal conductivity, demonstrating high healing efficiency for both mechanical and thermal transport properties. The enhanced thermal conductivity not only improved heat dissipation but also accelerated the healing process by rapidly delivering thermal energy to damaged regions. This work offers a promising strategy for developing long-life thermal management materials.