Study On The Processing And Properties Of Natural Flake Graphite-based Graphite Foam And Its Application In PCMs Materials

Graphite foams are widely used in the fields of electronics,communication,aerospace and military industry due to its characteristics of high thermal conductivity,high electrical conductivity,low density,large specific surface area and high temperature and corrosion resistance.In order to solve the problems of high energy consumption,high cost and complex process caused by high temperature graphitization of graphite foams prepared by traditional methods.In this thesis,the graphite foams were prepared by template method and foaming method,and the natural flake graphite with high crystallinity was used as the main raw material,with sucrose and phenolic resin as the binder,sodium bicarbonate as the foaming agent,and sodium chloride as the template agent.After that,X-ray fluorescence spectrometer,X-ray crystal diffractometer,laser thermal conductivity instrument,scanning electron microscope,transmission electron microscope and electronic universal testing machine were used to test the element composition,phase composition,thermal conductivity,microstructure and mechanical properties of the samples.Graphite foams were prepared by foaming method,the effects of graphite particle size and binder type on the properties of graphite foams were studied.The results showed that the best binder was sucrose and phenolic resin,and the best graphite size was 200 mesh.The graphite foams were prepared with sucrose as the binder to study the forming effect of foam and template method.The particle binding models of graphite foams were put forward and proved.The results show that the samples prepared by foaming method have better perforation and thicker wall,and the samples prepared by template method have higher repeatability and more stable performance.Steam is beneficial to the formation of pores,and the closer contact of graphite particles is,the better the thermal conductivity is.Graphite foams were prepared by template method using phenolic resin as binder and the preparation process was optimized.The effects of template content,molding pressure,binder concentration and mixing sequence on foam properties were studied.The results showed that the foam channel increased with the increase of binder content,and the thermal conductivity increased with the decrease of binder concentration.The obtained graphite foams show excellent performance,the maximum thermal diffusivity is 26.01mm~2/s,the maximum compressive strength is 3.5MPa,the maximum apparent porosity is 81.05%and the minimum bulk density is 0.362 g/cm~3.Composite phase change energy storage materials(PCMs)were prepared by using graphite foams with the best comprehensive performance as the carrier to adsorb the polyethylene glycol with a molecular weight of 2000(PEG2000).The results showed that the thermal conductivity of the PCMs material was 91 times higher than that of pure PEG2000,and its adsorption capacity was at least the same as the foam mass,and the highest adsorption capacity was more than twice the mass of the foam.