Highly Thermally Conductive Boron Nitride Fiber

Innovative thermal management fiber materials have emerged as a solution to address thermal challenges across diverse fields, ranging from personal comfort and electronic device cooling to aerospace engineering. While graphene fiber is known for its higher thermal conductivity over conventional carbon fiber, boron nitride (BN) has received much less attention in its one-dimensional form, despite its combined high thermal conductivity and notable insulating properties. Previous studies have mainly focused on composite fibers with BN nanosheets embedded in a polymer matrix. In contrast, pure BN fibers and consequent thermal conductivity investigations on a single-fiber level have barely been reported. In this study, we report the fabrication of continuous, pure BN fibers via the polymer-derived ceramic approach and its studies as thermally conductive fillers. Comprehensive structural characterizations confirm fibers' high quality and purity without apparent contamination. With the big-MEMS method we developed, the thermal conductivity of the single BN fiber is precisely measured and reaches an impressive 54 W m-1 K-1. Furthermore, using a stacking-cutting method, the resulting vertically aligned BN fiber-reinforced epoxy composite demonstrates a thermal conductivity as high as 24 W m-1 K-1, showing immense potential for usage as a thermal interface material. This work explores the potential of pure BN fibers for electrically insulating thermal management applications.