Catalytic effect of nickel under carbonization of polyimide films

In attempt to produce graphite films with high crystallinity by heat-treatment at temperatures lower than 3000 °C, the catalytic effect of nickel was investigated for carbonization of polyimide films prepared by mixing polyamic acid with nickel particles. The three-layered polyimide film was prepared to obtain graphite films with thickness beyond 100 μm. The middle layer composed of polyimide with nickel particles. The thickness of each layer was 50 μm and the film thickness became 150 μm. The carbonization was done at ca. 1600 °C for 5 h. The morphology of the carbonized films was observed by scanning electron microscopy. The graphitization degree was investigated on the basis of X-ray diffraction intensity distribution from the (0 0 2) plane. The analysis was done in terms of the comparison between the experimental and theoretical diffraction intensity curves. The theoretical calculation was carried out by using a concept for the para-crystalline theory proposed by Hoseman and Bagchi from the viewpoint of the lattice fluctuation of the c-axis.