High Boron-Doping-Induced Electrical and Thermal Conductivities of a Pan-Based Carbon Fiber

Abstract

The boron doping of carbonaceous materials is an attractive methodology for enhancing their electrical properties by modulating the chemical structures of pristine carbons. In this study, polyacrylonitrile-based carbon fibers (CFs) with highly developed microstructures were prepared by boron doping. Hydrothermally immersed CFs in boric acid were heat-treated up to 2700℃, and their chemical structures were traced to investigate the boron doping mechanism. Boron from the gasified boron-related functional groups of CFs diffused into the CFs to form boron carbide, B4C. The boron-doped CFs exhibited a highly developed crystalline structure that could not be achieved by heat treatment alone, indicating that boron accelerated the graphitic carbon structure. As a result, boron doping at 2700℃ simultaneously enhanced the electrical and thermal conductivities of CFs, with values of 3677.8 S/cm and 365.9 W/mK, respectively, which were 2.8 and 4.5 times higher than those of heat-treated CFs at 2700℃. In addition, CFs were used to prepare CF papers using a wet-laid process, and their heat generation and thermal management capabilities were evaluated. Considering affordable CFs compared to nanomaterials, we believe that our study provides a feasible approach for fabricating heating elements and heat sinks.

Keywords: boron doping, Carbon fiber, electrical and thermal conductivities, graphitization, heating element.