The Study Of High Modulus Carbon Fibers By Catalytic Using Boron As Catalyst And Mechanism Of Graphitization

High Modulus Carbon Fiber(HMCF) is an important variety of carbon fiber. Owing to its high performances such as high modulus, high dimension stability,low coefficient of thermal expansion, heat resistance and low density ,HMCF is extensively used in artificial satellite ,the building up of national defense and national economy.The way of solution-coating for doping boron is a simple and feasible, low-priced and easily successively industrialized process. The production of PAN-based high modulus carbon fibers by catalytic graphitization using boron as catalyst and mechanism of catalytic graphitization were studied in this paper. T-300 carbon fibers were treated with 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. It is fit in treatment could raise the Youngs modulus of carbon fiber to 452 Gpa and the strength to 4.29 Gpa.The mechanixm of enhancing modulus and catalyticgraphitization by doping boron are to be raised and improved through characteristic analysises(SEM,XPS,X-ray etc.)of boron-undoped CF and boron-doped CF contains a series of big and regular fraphitic crystallite layers which arrange along the fiber axis and have few fracture defects and hifhly ordered degree, as a result, the modulus of CF is higher . Boron can accelerate the graphitization process, the chemical changes as followings: the decompose of boride, the formation decompose of BN, the formation of boron. In the end , a very small amount of boron remains in the carbon fiber. Boron is effective catalysises for the carbon fraphitizaation,which has been proved by the variation of crystallite parameters(La, Lc andCarbon fiber; doping boron; catalytic graphitization; mechanical properties...