Preparation Of High Thermal-conductivity Flake Graphite/Al Composites

The rapid ascension of highly integrated electronic devices led to the inevitable generates heat. If you want to improve the performance and reliability of electronic products, thermal management materials must be coming put forward higher requirements. Traditional thermal management materials have been unable to meet the development of modern packaging technology requirement for heat dissipation, composite and lightweight materials has become an inevitable trend. Aluminum carbon composites as the representative of new lightweight composites with high thermal conductivity show the strong performance in the aspect of the thermal physical properties, including high thermal conductivity flake graphite/aluminum composites because of its excellent workability and low prices attracted wide attention.In this study, high thermal conductivity flake graphite/aluminum composites was prepared by Spark Plasma Sintering method. By optical microscope(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD), transmission electron microscopy(SEM) and other testing means, the microstructures of the flake graphite and flake graphite/aluminum composites was analyzed and characterized. Using density balance, LFA laser flash method tester, thermal expansion analyzer, electronic universal material testing machine and other equipment, the performance of high thermal conductivity flake graphite/aluminum composites was tested. The milling process, the sintering process and volume fraction of graphite in the composites were studied on the influence of the flake graphite/aluminum composites’ structure, thermal physical properties and mechanical properties.The results show that choose the flake graphite with 95.3% of degree of graphitization and 900±10W/m?K of thermal conductivity on the x-y plane as experimental material. When using Spark Plasma Sintering to prepare high thermal conductivity flake graphite/aluminum composites, an appropriate increase in the sintering temperature and pressure will help improve the relative density of the composites, but it is likely to cause an overflow of molten aluminum at the too high sintering temperature and pressure. Right sintering temperature of 600℃ and the sintering pressure of 50 MPa conducive to prepare the composites with high relative density. The interface bonding of high thermal conductivity flake graphite/aluminum composites is closely tight, section is clean, and there was not observed the formation of Al4C3. With the increase of graphite content, the density of the composites is reduced, however the relative density is maintained at more than 99%. As the graphite content from 40% to 60%, the thermal conductivity of the composites increase from 249 W/m·K to 440W/m·K. The directional alignment and high thermal conductivity of the graphite flake is beneficial to the heat transfer along the x-y plane. On the z-plane, thermal conductivity of the composites reduces with the increase of graphite content. With the increase of graphite content, the thermal expansion coefficient of thes is reduced and good agreement with the predicted values of hybrid model.