THE INFLUENCE OF BORON MODIFICATION OF PAN-BASED CARBON FIBERS ON THE MICROSTRUCTURE

The boron modification of PAN based carbon fibers was studied. The HTA 3K carbon fibers were impregnated in borate solution and then heated in range of 1?900?℃～2?500?℃. The crystallite size and the degree of preferred orientation were characterized by X ray diffraction. The effect of boron on the mechanical properties and microstructure of carbon fiber was investigated. It was found that the tensile modulus of boron doped CF obviously increased, while the tensile strength did not decrease. It is shown that interplanar spacing (d 002 ) decreased and crystallite size (La, Lc) and the degree of preferred orientation increased after doping boron.