Abstract
Kapton-type polyimide films containing 0.1 at% Ni (PI-0.1Ni) and 0.5 at% Fe (PI-0.5Fe) were prepared from polyamic acid and each metallocene, and carbonized at a heat treatment temperature (HTT) of 400 -1600°C in flowing argon. Nickelocene was reduced to Ni metal particles of less than 20 nm in diameter at 450°C by 1h treatment. The PI-0.1Ni started to decompose by about 200K lower than the film without additives (PI), while with PI-0.5Fe such effect was not observed. Further, with PI-0.1Ni a sharp carbon 002 peak around 2θ=26° was developed markedly with raising HTT from 1000 to 1600°C. With PI-0.5Fe, the 002 peak became sharp at HTT =1050°C, but the peak intensity and profile changed only slightly in a range of 1100 1600°C. In the 1600°C treated PI-0.1 Ni, fairly large areas with oriented hexagonal carbon layers and those with entangled ribbon-like structure were observed in the lattice images by TEM. A small number of tunnel-like holes (1-2 μm in diameter) were observed by SEM in the cross-section of the film, which suggested the movement of Ni metal particles during the heat treatment. The 1000°C treated PI-0.1Ni was not graphitized by 1 h treatment at 3000°C, suggesting the formation of so-called “TS carbon.” The present results showed that very small amounts of Ni are effective to the initial thermal decomposition of the polyimide and subsequent formation of turbostratic carbon, whereas Fe seemed to enhance the development of turbostratic carbon less effectively.
