Surface modification of hollow carbon fibres using plasma treatment

A plasma treatment is developed to modify the surfaces of micrometre sized hollow carbon fibres. After oxidisation and activation, hollow carbon fibres exhibit pores on the outer surfaces. With a further treatment in a mixed plasma of CH₄–H₂ at 3000 W for 2 h, many cavities of about 3–5 μm in size are formed by plasma etching on the outer and inner surfaces. Nanoscale whiskers are uniformly distributed inside the cavities by plasma deposition. The I_D/I_G Raman ratio increases from 2·09 to 5·93 after the plasma treatment, suggesting that graphite crystallite size has been reduced from 2·11 to 0·74 nm. The nanoscale whiskers are disorder graphite and are aligned inside the micrometre scale cavities. A whisker/cavity structure is generated on the outer and inner surfaces of the hollow carbon fibres.