The Preparation Of High-quality Graphene And Properties Of Its Epoxy Composites

Graphene has been discussed heatedly by many scientists since 2004,based on its excellent performance,such as high thermal conductivity,extrahigh electrical conductivity and so on.However Most of excellent properties of graphene usually depend on its quality.In other word,only graphene without defects and other atoms can make a big difference in practical application.At the same time,faced with the fast development of electronics,heat dissipation of the main electron components is still a critical problem to be solved.The use of thermal interface materials is regarded as a good way to prolong life-span and improve efficiency of electronics.Hence,we try to prepare high-quality graphene without other atoms and defects and mix it with epoxy to obtain thermal interface materials with good thermal conductivity and electrical conductivity in our research.1.We fabricated two kinds of graphene oxide according to Hummers method and Staudenmaier method?S-GO,H-GO?,and thermally reduced them by muffle furnace at 1050??S-G1050,H-G1050?.Compared with H-G1050,S-G1050 preferred to be expanded at a high heating rate and was bigger at dimension.Therefore,we prepared thermally annealing graphene?TAG?at ultrahigh temperature based on S-G1050,because it was easier to repair.By means of analyzing characters of TAG,we obtained pristine graphene with C/O = 97,ID/IG = 0.04 and TH = 5 nm and the following conclusions:Firstly,the oxygen-containing functional groups of G-1050 was removed completely at 1500?;Secondly the defects of G-1050 were healed remarkably when temperature was rose to 2000?;Finally,with the rise of temperature,graphene began to stack layer by layer and specific surface area of TAG declined.2.We mixed graphene thermally annealed by different temperature with epoxy and succeeded in fabricating TAG@Epoxy nanocomposites.In same way as we had expected,the quality of graphene played a vital role at heat dissipation of composites.Graphene with few defects was conducive to phonon vibration.So electical conductivity of TAG2800@epoxy composites increased from 10-14 to 4546 S m-1 at 10 vol%and thermal conductivity of TAG2800@epoxy composites was much better to G-1050@epoxy,which reached to 4.43 W·m^-1·K?-1? and increased by 24 times than epoxy.3.We replaced anhydride curing agents by polyether amine?D230 and D2000?and designed some different formulas about D2000,graphene nanoplatelets?GNPs?and TAG2800 to prepare nanocomposites.Finally,we obtained some nanocomposites with high electrical and thermal conductivity,especially good toughness.At the same time,we discovered that the addition of D2000 was benefit of toughening pure epoxy.When D2000 was added to 40 fractions,epoxy became flexible and its notch impact strength increased to 127 kJ m-2.However,when the mass fraction of GNPs exceeded 30%,the toughness of nanocomposites was no longer improved with the addition of D2000.Notch impact strength of 40 wt%GNPs@flexible epoxy nanocomposites was only 2.64 kJ·m-2,which was even inferior to pure epoxy without D2000.On the other hand,the compounded system of GNPs and TAG2800 performed more efficient at heat conduction than single system of GNPs or TAG2800.Compared with Thermal conductivity of 30 wt%GNPs@epoxy nanocomposites,Thermal conductivity of GNPs/TAG2800@epoxy nanocpmposites extended 236%and reached to 7.783 W·m^-1·K?-1?.