EFFECT FACTORS ON MAGNETORESISTANCE OF C/C COMPOSITE PREPARED USING PREFORM WITH NEEDLE-PUNCTURED CARBON FELT

The characteristic of magnetoresistance of C/C composite prepared by preform with needle-punctured carbon felt at different heat treatment temperatures(HTT) was investigated.The magnetoresistance of C/C composite at different treatment temperatures is the same at the orientation angles of 0°~180° and increases with the rise of HTT.The intensity of magnetic field H and measured temperature(MT) have no effect on the relationship between magnetoresistance and orientation.Magnetoresistance-MT curves for the studied samples are linear in the same magnetic field and at higher MT,less magnetoresistance.The magnetoresistance of samples has negative at lower HTT value and positive value at higher HTT.The magnetoresistance of the samples tends to zero in case of(enough) high MT. The regressing magnetoresistance-temperature curves and the slope fall with the rise of HTT,and the shape of the(slope-)HTT curve is similar to that of the d_(002)-HTT curve.The magnetoresistance of C/C composite increases with increasing the intensity of magnetic field at the same MT.The curves are quadratic function when H is less than 1.2×10~7A/m and the curves are linear when H is higher than 1.2×10~7A/m.The magnetoresistance increases with the rise of HTT in the magnetic field of any intensity.