Study On The Process And Mechanism Of High Modulus Carbon Fiber Prepared By Boron Catalyst

High modulus carbon fibers are finding wide application in airspace industry because of their high specific moduluds, low coefficient of thermal expansion, high dimension stability, heat resistance, etc. 1980s the high modulus carbon fibers have been used as structural materials making of artificial satellite, rocket, missile and so on in U. S. A. However, there are a little study on high modulus carbon fibers in our country.The production of PAN-based high modulus carbon fibers by catalytic graphiti-zation using boron as catalyst and mechanism of catalytic graphitization were studied in this paper. T-300 carbon fibers were treated with boride by three methods of electrochemical anodic oxidation, soaking and coating, and subsequent graphitized at 2500 ℃. The effect of treating condition (form of boron used, the concentration, temperature of the solution of boride, the heat-treatment temperature) on the mechanical properties of the resulting carbon fibers was investigated. In this work the method of coating has been used to introduce boron-containing group on the surface of carbon fibers for the first time.It was found that the soaking and coating of three methods achieve good results, and the method of coating is more fit in with the needs of the process of the continuous production. The Young's modulus of carbon fibers increased from 397GPa to 448GPa and the strength from 3.74GPa to 4.28 GPa when carbon fibers were soaked in mixed solution of boride A and activator a. The coating boron treatment could raise the Young's modulus of carbon fibers to 465Gpa and strength to 4.19Gpa.Before and after doping boron the surfacial micromorphology was characterized by STM. It was found that doped boron decreased defect on surface of carbon fibers and increased the degree of preferred orientation. The wide-angle X-ray diffraction...