The Investigation Of The Magnetoresistance Character Of C/C Composite

C/C (Carbon / Carbon) composite is a sort of advanced material that has excellent thermal and mechanical properties. It is widely used in many engineering areas. With internal spaceflight industry developing, C/C brake must be produced independently. So, the structure,preparation techniques and properties of C/C composites should be investigated .Four kinds of C/C composites with different preparation techniques were graphitized at 2400 - 2880℃. The relations between magneto -resistance and orientation (the angle between surface of samples and magnetic field ), measure temperature,the intensity of magnetic field (B) were studied for each sample. The micro-structure and X-ray diffraction pattem were investigated too. Investigation results conclusions are as follows:1) The magnetoresistance - orientation curves have discrepancy that just is angle for different orientation carbon fibres. The magneto -resistance - orientation curve of C/C composite is occur repeatedly that The magnetoresistance - orientation curve of different orientation carbon fibres. the orientaton of maximal magnetoresistance( (Δρ/ρ)max) varies with the structure of materials.2) The magnetoresistance of low graphitization degree samples is negative while it is positive for high graphitization degree samples. Positive magnetoresistance linearly reduce and negative magneto -resistance linearly increase as measure temperature increase. 3) Some low graphitization degree samples' magnetoresistance is 0 when measure temperature is enough high.3) In low intensity of magnetic field, the curve of Δρ/ρ0 - B is parabola. In high intensity of magnetic field, The magnetoresistance of C/C composites doesn't change with the intensity of magnetic field. Themagnetoresistance of C/C composites is quantum in enough low temperature.Through synthetic analysis, this study consider (Δρ/ρ)max ,not (Δρ/ρ)cr is parameter of C/C composite's magnetoresistance property. Ideal measurement parameter is 70-100K for measurement temperature and 1-1.2T for the intensity of magnetic field. the slope (k) of magnetoresistance - temperature Regressed curves is a structure parameter, it falls linearly with g ( the graphitization degree) increases. k can be useed to measure the graphitization degree of C/C composite.