DETERMINATION OF THE TYPE OF CHARGE-CARRIERS IN CARBON-FIBER POLYMER COMPOSITE

The Hall effect method has been used to determine the charge carriers' density in polycarbonate/carbon fibers composites. It was found that the measured Hall voltage varies almost linearly with Hall current. Th is behavior indicates that the majority of the charge carriers are of one type. The sign of the slope of this relation varies from positive to negative for composite specimens of about 18 wt% carbon fibers. Thi s suggests that composites of low fiber content are functioning as p-t ype material and then change to n-type with increasing carbon fiber co ntent. The observed anisotropic behavior of the charge carriers' densi ty makes it difficult to calculate the kinetic parameters, such as the carriers mobility of such composite materials, from the Hall effect a nalysis. (C) 1998 Elsevier Science Ltd. All rights reserved.