Surface NH2-functionalized by C doping of boron nitride nanotube to improve the thermal conductivity of epoxy composites

Abstract To reduce the interfacial thermal resistance between boron nitride nanotubes (BNNTs) and epoxy resin, we report a novel method to obtain NH2-functionalized BNNTs with a perfect crystal structure by C doping to construct chemically active sites on the BNNT surface (BNNT-A), and compare it with the conventional method of NH2-functionalized BNNTs by breaking the B–N bond (BNNT-B). The results show that the insulation properties and thermal conductivity of BNNT-A were better than those of BNNT-B. When the NH2-functionalized ratio was 5%, the thermal conductivity of BNNT-A was improved by 12.21 W/(m·K) compared with that of BNNT-B. NH2 functionalization had little effect on the insulation properties of BNNT-A/epoxy resin (BNNT-A-EP), and BNNT-B/epoxy resin (BNNT-B-EP) comparing with BNNT/epoxy resin (BNNT-EP). The thermal conductivity of BNNT-A-EP was 2.52 W/(m·K), which was improved by 23.5% and 77.5% compared with BNNT-B-EP and BNNT-EP, respectively. In addition, the volume change rate of BNNT-A-EP was reduced by 27.6% and 50% relative to BNNT-EP and BNNT-B-EP. The functionalization of NH2 on the surface of BNNTs by C doping can establish an effective heat transfer "bridge" between BNNTs and epoxy resin, which is beneficial for improving the thermal conductivity of epoxy composites. This work presents a strong potential method to reduce the interfacial thermal resistance of electronic packaging materials.