膨胀石墨基复合材料的制备及其导热性能的研究

Preparation and thermal conduction property of expanded graphite matrix composites

以中间相沥青和聚酰胺酸为黏结剂和增密剂,用两种不同方法与预压膨胀石墨进行复合。再经过模压炭化,得到高密度、高取向和高导热的炭/石墨复合材料。同时研究了不同沥青含量和不同聚酰胺酸溶液浓度下复合材料的致密性和导热性能。结果表明,随着沥青用量增加,复合材料的密度增加,并在沥青含量占30%时密度达到最大值。热导率在沥青用量为15%时达到最大,为530.64 W/m·K,比铜的热导率高33%。液相浸渍法下,浸渍溶液浓度为12%时,浸渍效果最好,复合材料的热导率和密度达到最大值。相比而言,中间相沥青比聚酰胺酸对膨胀石墨的密度和热导率提升效果更好,这主要是由于在热压条件下,沥青的软化和流动性造成的,流动的沥青能够更好地填充膨胀石墨的孔隙。

Expanded graphite matrix composite was fabricated by mechanical mixing, mold pressing and liquid impregnation meth- ods with mesophase pitch and polyamide acid（PAA） as additives. The density and thermal conductivity of the composites were investigated. The results showed that the sample with pitch content of 15% had the highest thermal conductivity, and the composite achieved maximum density when pitch content was 30%.The maximum thermal conductivity achieved 530.64 W/m·K, which was higher 30% than that of the pure copper, and the maximum density is 1.72 g/em3.For liquid impregnation method, the sample impregnated with 12% PAA solution achieved the maximum value of the thermal conductivity of 331.20 W/m. K and density of 1.64 g/ cm^3, respectively. The SEM images revealed different compactness and orientation characteristics of the samples from different methods. Composites fabricated with mechanical mixing and mold pressing had higher densification and filler orientation than those from liquid impregnation method, leading to better thermal conductivity and density performances. The main reason may be due to the induced fluidic motion of mesophase pitch during the hot-press process, which flushes the gaps between graphite flakes more effectively.