Preparation of Carbon fiber/Cement Composites from Surface-modified-carbon Fiber by Low Temperature Plasma

Abstract

Surface modification of PAN based carbon fiber (CF) by low temperature plasma was investigated to give high compatibility between CF and matrix in CF/cement composites (CFRC). The surface treatment of CF was carried out with O2, Ar and CF4 plasmas generated by radio frequency (13.56 MHz). The wettability of water on CF surface was remarkably modified to hydrophilic by O2 and Ar plasmas, and to hydrophobic by CF4 plasma. Furthermore, the CF surface was analyzed by ESCA and observed by SEM. It was found that the acidic group on the CF surface was formed by O2 plasma, and the surface fluorination on CF was carried out by CF4 plasma.Then, the CF paper after plasma treatment was used for the preparation of CFRC. CFRC plates (6 mm in thickness) were prepared by the lamination of 12 sheets of CF paper preimpregnated with alumina cement paste, and were cured in water.These CFRC's showed 2.0 g/cm3 in bulk density and 3.6 vol% in CF contents. The flexural strength of these CFRC's prepared from plasma-treated CF, was about 10-12 times higher than that of alumina cement hydrate. The CFRC plates prepared from CF paper pretreated in O2 and Ar plasmas exibited 1.8 times higher in flexural strength (60MPa) and 1.5 times larger in deflection compared with the CFRC without plasma treatment on CF. The flexural strength (74MPa) and deflection of CFRC plates prepared from CF4 plasma-treated CF, were the largest all.Accordingly the low temperature plasma treatment of CF is regarded as an effective modifying method of CF for CFRC.