Microstructure and mechanical properties of twisted carbon nanofibre bundles developed from impregnated electrospun polyacrylonitrile films

Abstract

Impregnated polyacrylonitrile nanofibre bundles with specific twist level and relatively uniform diameter were developed from aligned electrospun nanofibres. Subsequent stabilization and multi-step carbonization treatment were carried out under tensile force. The effect of surface tension and polarity of polar solvents on the microstructure and mechanical properties of twisted nanofibre bundles was studied. The interspace and the surface roughness of the nanofibre bundles was reduced with rising solvent polarity, following reduction in diameter of the twisted nanofibre bundles. After the impregnating and twisting process, good alignment of nanofibres was achieved, and the mechanical properties of nanofibre bundles improved with increasing solvent polarity and twist level. Besides, the crystallization properties and the graphitization of carbonized nanofibre bundles could be strengthened through the twisting process. A high axial Young's modulus of 124 GPa can be attained for carbon nanofibre bundles with a nanofibre orientation angle of 39° (500 TPM, twist per meter). The experimental results indicated that the combination of impregnating and twisting process was a practicable approach to develop new-type carbon reinforcement with high mechanical performance.