聚酰亚胺基石墨膜的制备、高温结构演变及其导热性能研究

Preparation,High-temperature Structural Evolution and Thermal Conductivity of Polyimide Films

目的系统研究聚酰亚胺(PI)膜在高温碳化、石墨化过程中的微观结构演变,以及PI膜厚对石墨膜结构和导热性能的影响机制。方法采用二步法制备2种不同厚度的PI薄膜,对其进行高温碳化、石墨化和压延处理,并系统研究薄膜高温结构演变规律和及其导热性能。结果涂布法制备出的PI膜膜厚分别为32、67.5μm,经1000℃碳化后,薄膜从无序结构转变无定形碳,并在2800℃高温石墨化过程中转变为高度有序的层状石墨结构,经压延工艺处理后,其石墨膜厚度分别为17、40μm,压延工艺减少了石墨膜疏松孔洞和片层间间距,显著提高了石墨膜面内导热系数。结论在一定范围内,薄膜越薄,越有利于杂质元素脱除和提升石墨化程度。所制得的17μm石墨膜面内热导率可达1465 W/(m·K)。

The paper aims to systematically study the microstructure evolution of polyimide(PI)films during carbonization and graphitization at high temperature and the influence mechanism of PI film thickness on the structure and thermal conductivity of the graphene films.Two kinds of polyimide(PI)films with different thickness were prepared by two-step method,and were further processed by high temperature carbonization,graphitization and calender to obtain graphite films with high thermal conductivity.The high temperature structure evolution and thermal conductivity of the films were systematically studied.The results showed that the thicknesses of PI films prepared by plate-coating method were 32 and 67.5μm,respectively.After carbonization at 1000℃,the film transformed from disordered structure to amorphous carbon,and turned into highly ordered graphite structure during graphitization at 2800℃.After calender,the thicknesses of graphite film were 17 and 40μm,respectively.It reduced the porosity and interlaminar spacing of graphite layers.In a certain range,thinner film led to easier removal of impurity elements and enhancement of graphitization,resulting in significantly improved in-plane thermal conductivity of the graphite film.The in-plane thermal conductivity of 17μm graphite film can reach to 1465 W/(m·K).