| Summary: | 碩士 === 逢甲大學 === 紡織工程研究所 === 83 === A continuous stabilization and two-stage carbonization process were used to prepare the polyacrylonitrile(PAN)-based carbon fibers. This study includes three parts. First, noibuming fibers, which were pre-carbonized at 300℃, were treated with nitric acid at 50 ℃ with different concentration(10-60 wt%) and various tirne(10-60 mins). Second, the pre-carbonized fibers were heat-treated fiom 400 to 1300℃. Third, the surface treatment of these carbon fibers were carried out in air(300-550℃), in CO2(400-900℃) and nitric acid (68 wt%, 0.5-12 hrs), respectively. After surface treatment, the mechanical properties and the surface properties of the final carbon fibers were improved.
In this article, the influence of microstructure was investigated by X-ray diffraction, element analysis, SEM, FTIR, ESCA. The analysis of physical properties were carried out with density, single fiber tensile test, DTA, Limited Oxygen lndex(LOI).
In the first field, when nonburning fibers were treated over 40wt% HNOa treatment, the core of the fibers were etched away. The new poresize were formed in cross-section of fibers. In the mild treatment(10 wt%, 10 & 20 mms), the disordered surface of fibers were etched by HNO3. This process is led to an increase in the mechanical properties, and a decrease in the LOI value. In the second one, from SEM and density analysis, when HTT was up to 800℃, it took place a large amount of micro-pores on fiber surface. The same phenomena were effect continuos up to 1300℃. When the fibers were carbonized at 1300℃, the tensile strength increased 28.3 times and modulus increased over 90 times. The third field, we found that the optimum treatment would improve the mechanical properties of the final carbon fibers. From ESCA analysis, three different process of surface treatment increased the functional groups riched in oxygen. When the carbon fibers were treated by HNO3, this process led to a remarkable functional groups on surface.
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