Study On The Characterition Of Nitrogen Release And Effects On The Sructure And Properity Of PAN Fiber

Carbonization is the important stage for the structure and property forming of PAN-CF.In this process, the release of non-Carbon elements due to the content of C element in the fiber was increased,mostly was N element, and the desorption of N element is all-important to the carbonization of PAN fiber. Therefore the research on the release character of N element has an important academically significance to fully understand the process mechanism of carbon fibers.The change of combination states of N is the most important character in the course of the release of N.But at present, the research on the evolution of N was few and not detailed. In this paper several technologies, such as EA, TG-MS, XPS, Raman s, XRD, Volume Density and Mechanical testing were used to investigate the evolution of the combination state of N with temperature and time in high temperature carbonization, speculate about the reaction mechanism, and set up the correlation of the combination state of N and the evolution of the fibers structure and property. The results showed that:1. The evolution of the combination state of N in PAN fiber relied on temperature and time.The relative and absolute content of the combination state of N in PAN fibers were changed with temperature and time,and the effect of temperature was more obvious than the effect of time.The time effect is more obvious with a higher temperature.2. N existed in three combination states as the pyridine nitrogen, amino (or imino) and graphite-like nitrogen in carbonization with high temperature. N in graphite-like nitrogen is more conducive to carbonization.3. With the increase of heat-treatment temperature, the pyridine nitrogen and amino (or imino) content decreased, graphite-like nitrogen content increased at first and then decreased when the temperature higher than 1000℃.The content of these three combination states all changed a little at 700℃.The pyridine nitrogen and graphite-like nitrogen content decreased obviously at 1100℃,while amino (or imino) content changed little.4. The evolution of N in combination states made a development of the fiber structure and improve the fiber property, that is the parameters such as graphitization degree, the crystallite size, volume density, tensile strength and modulus changed with temperature and time.5. The decomposition of graphite-like nitrogen caused a turning point in the value chang of R and volume density between 1000℃～1100℃.