高导热石墨膜的制备及表征

Preparation and characterization of graphite films with high thermal conductivity

将不同厚度杜邦聚酰亚胺(PI)薄膜进行压制炭化、石墨化处理得到PI石墨膜。采用扫描电镜、X射线衍射、、拉曼光谱等测试手段分析了PI薄在高温热处理过程中的结构演变。研究结果表明,50μm厚PI膜经3 000℃高温石墨化后能形成三维有序堆积的石墨层状结构和较为完整的石墨晶体,其石墨片层间距为0.336nm,层片堆积高度达到65.94nm,石墨化度高达93%,室温面向电阻率为0.48μ!·m,实测面向热导率达到了994 W/(m·K)。随着热处理温度的提高,PI膜微晶由无定型向有序类石墨结构转变,其结晶度和层片取向程度提高,石墨晶体逐渐完善。PI膜厚度越大,其类石墨晶体生长发育越困难,层片择优取向程度越低。

Graphite films were prepared from DuPon polyimide films with different thicknesses by carbonization and graphitization treatments at a certain press.The micro-structural evolution of PI films during the process of high-temperature treatments was characterized by polarized light microscope,scanning electron microscope,Xray diffraction and Raman spectrum.The results show that the PI graphite films(with a thickness of 50μm for raw films)possess a three-dimensional structure of graphite layers with preferred orientation and prefect graphite crystals after graphitization at 3 000 ℃.The corresponding interlayer spacing and stacking height of(002)crystal plane of the PI graphite film are 0.336 and 65.94 nm,respectively.The degree of graphitization of the PI graphite film is as high as 93%,and the electrical resistivity and thermal conductivity of the PI graphite films at room temperature in the main plane direction are measured to be 0.48μ!·m and 994 W/(m·K),respectively.The higher heat-treated temperature,the more easily transformation from the turbostratic carbon to ordered graphite,resulting in the better growth and crystallization of graphite microcrystals,and the more orientation of graphite layers.However,the microcrystals in the thick PI graphite films grow and crystallize difficultly,and their preferred orientation of carbon layers is very low.