针刺毡预制体炭/炭复合材料磁电阻特性的影响因素

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

研究了针刺毡预制炭/炭复合材料(C/C)经不同温度石墨化处理后的磁电阻特性.结果表明:实验材料磁电阻于各位向(0°～180°)均相等,且石墨化处理温度越高,材料的磁电阻越大,外磁场强度、测量温度等因素不影响磁电阻-位向关系;在同一磁场强度下,石墨化处理温度高的材料磁电阻为正值,石墨化处理温度低时磁电阻为负值,且磁电阻与测量温度(5～300 K)呈线性关系变化,高于一定测量温度后,磁电阻稳恒为0;磁电阻-测量温度曲线回归方程的斜率随热处理温度的增加而降低,且斜率-热处理温度的变化曲线与材料的晶面间距d(002)随热处理温度的变化曲线形状类似;测量温度相同时,磁电阻随外加磁场强度的增大而增大,在低场强(低于1.2×107A/m)下,呈现二次函数关系,当场强高于1.2×107A/m,磁电阻-磁场强度关系为线性;不同场强下,随石墨化处理温度的提高,磁电阻也增大.

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 S 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 d002-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.