Design And Fabrication Of Thermal Interface Materials Based On Pitch-based Carbon Fiber

The rapid development of technologies such as high-power chips,high-energy density cells,wireless charging,AI and the Internet of Things are all supported by thermal management technology.The thermal interface material is filled between the heating element and the heat trap and is the key component of the thermal management device.Asphalt based carbon fiber not only has the advantages of high thermal conductivity,high strength,low thermal expansion coefficient and high aspect ratio,but also has a perfect industrial foundation and scientific research investment,is one of the best choice of thermal conductivity filler of thermal interface materials.However,how to overcome the high conductivity of graphite fiber,realize the directional arrangement of fiber filler and nondestructive surface treatment of carbon fiber are still the key problems to be solved urgently.In this paper,the surface chemical environment of inert carbon fiber was improved by plasma surface treatment and non-covalent modification,and the high thermal conductivity insulating carbon fiber was prepared by impregnation method and magnetic field orientation technology,and the carbon fiber was directional filled.The specific research contents are as follows:1.The carbon fibers coated with boron nitride were prepared by impregnation method with low temperature oxygen plasma surface modification to improve the reactivity of high graphitized pitch carbon fibers.As a high thermal conductivity insulating ceramic,boron nitride can effectively block the conductive path of carbon fiber and improve the resistivity of composites.The thermal conductivity of the thermal interface material can reach 3.3 W/m K at the filling amount of 60 wt%,which is 20 times that of the pure silicone rubber（0.16 W/m K）.Meanwhile,the conductivity can be maintained at 4.98×10^-7 S/cm,which is two orders of magnitude lower than that of the pure carbon fiber filled silica gel.2.Using high graphitized pitch based carbon fibers as raw materials,the carbon fibers were given paramagnetism by PVP non-covalent modification and in situ growth of Fe₃O₄,and were orientated by external magnetic field to produce thermal interface materials.The effects of magnetic field intensity and loading fraction on fiber orientation were investigated by XRD,SEM and polarizing microscope.In the magnetic field of 400 m T,the thermal conductivity of the directed thermal interface material is significantly improved.The average surface temperature of the 90℃plate heated at constant temperature for 20 s is 79.72℃,4.67%higher than that of the undirected pure carbon fiber,and the conductivity is 1.49×10^-10 S/cm,two orders of magnitude lower than that of the contrast sample.Reflects the better insulation.