牵伸石墨化对石墨纤维结构和力学性能的影响

The influence of stretching ratio between 02.5% on microstructure and mechanical properties of PANbased graphite fibers was investigated by XRD and mechanical testing for graphitization temperatures of 2400, 2700 and 3000℃. Results show that stretching ratios of 1.25, 1.5 and 2.20% yield a maximum tensile strength of 3.1, 2.55 and 2.25GPa at 2400, 2700 and 3000℃ respectively, and the maximum tensile strength is an increase of about 10-20% compared to the unstretched samples at the same temperature. The elasticity modulus of the graphite fibers increases with stretching ratio at the different temperatures investigated and is 15% larger than that of the unstretched samples at a stretching ratio of 2.5%. The size of crystallites Lc (3.612-7.094nm), La (12.90924.400nm) and orientation degree of crystallites (89.51-92.97%) increase, but d002 (0.3465-0.3418nm) decreases with the stretching. This contributes to the increase of tensile strength and modulus of the graphite fibers.