Study On Carbon Film Were Prepared From Polyimide Film And Diamond-Like Carbon Film Were Deposiited On Carbon Film

Carbon films were prepared from polyimide (PI) films by the processes including piled up several PI films to form a sheaf and the sheaf of the films was carbonized and hot-pressed in a high temperature. Electrical conductivity and thermal conductivity properties of carbon films were improved by diamond-like carbon (DLC) films were deposited on carbon films. The structure and properties of carbon films were studied by XRD, element analysis, TG, DSC, IR, SEM, Raman, et al.The results show that carbonizing pressure and temperature rise rate were the most important factors which influenced the surface and performance of carbon films. High pressure and temperature rise rate will result in bad surface and crack. The changes of structure and its effect on performance of PI films have been studied at carbonization temperature range of 0℃～1000℃. The experimental results show that the weight of films decreases about 28% in a narrow temperature range of 500℃～650℃. The crystal structure of the sample starts to appear above 600℃and the formation and growth of hexagonal carbon layers were observed above 700℃. The electrical property has a transition around 700℃, which is consonant with structural conversion.The changes of structure and its effect on property of PI films were studied at carbonization temperature range of 1000℃～1600℃. Results show that with increasing carbonization temperature between 1000℃and 1600℃, the ordering degree of the structure of the sample increase. The content of carbon element increase with rising temperature while the content of nitrogen and oxygen decrease, which show that residual nitrogen and oxygen were released. Because the network lamellar structure with hexagonal rings of like graphite formed and increased gradually with the increasing carbonization temperature, the electrical property was improved.DLC films were deposited on carbon film that obtained from carbonization of PI films by plasma enhanced chemical vapor deposition method. It were found that with increasing of deposition time, electrical resistivity of carbon films decreased at first, then increased, the electrical resistivity of carbon films reached minimum value: 5.66×10^-5Ω·m at deposited 3 hours. With increasing content of H₂ in the carbon source gas, electrical resistivity of carbon film increases at first and electrical resistivity reach the maximum at content of H₂ of 70%, then decreased with further increasing content of H₂.