| Graphene is well known for its excellent physical properties.However,achieving large-scale and high quality graphene in large quantity is very difficult,which also strict the wide application of graphene.Numerous researchers have reported that liquid exfoliation is an effective method to obtain high quantity graphene and it is promising for large amount of preparation of mono or few layer graphene nanosheets.The products of liquid exfoliation are always suspension,slurry and powder of graphene nanosheets.The solid contents of graphene suspension and slurry are usually very low,which means the solvents occupy most of the volume and mass,leading to ultra-high transportation cost and serious security issue.Meanwhile,the density of graphene powder is usually very low,which also increased the transportation cost.In order to overcome the issues above,a graphene block with high density,high graphene weight content and excellent redispersion property is urgently needed.Surfactant is necessary because it will enhance the re disperse ability of graphene block and the suspension stability.Otherwise,it can be intercalated between graphene nanosheets and further improve the redispersion ability.Therefore,the investigation of effect of surfactants on redispersibility of graphene is of vital importance.Therefore,in this study,graphene was taken as the research object.Firstly,five graphene/planck dispersions with different molecular weight and mass ratio were prepared.Graphene solids were obtained by drying in different ways.The effect of Planck on the redispersibility of graphene was studied.The redispersibility rule and mechanism of graphene/surfactant aqueous dispersion were summarized.Secondly,a kind of graphene effervescent tablet with high graphene content and rapid redispersion in water was obtained by fully grinding the graphene solid and effervescent tablet with the idea of effervescent tablet.On this basis,the method of sodium deoxycholate-assisted construction and vacuum filtration was also explored to successfully prepare three-dimensional graphene skeleton and graphene/epoxy resin composites with complete thermal conductivity,which greatly improved the thermal conductivity of epoxy resin and was another application of surfactant-assisted preparation of graphene blocks.The following conclusions are obtained by means of ultraviolet spectroscopy,contact angle measurement and laser thermal conductivity instrument.(1)Graphene with high dispersion rate can be successfully prepared by using 5 kinds of Planick as dispersant.Among them,P123 has the best redispersion effect on graphene and F108 is the worst.In freeze-drying process,P123 has the best redispersion performance on graphene and L61 is the worst.Graphene solid graphene treated by freeze-drying has high mass fraction and good redispersibility.At the same time,sedimentation experiments show that the absorbance value of graphene/P123 water redispersion solution decreases by 0.2,which can effectively reduce the surface tension of water and increase the spacing of graphene layers,and maximize the dispersion performance of graphene redispersion solution.(2)When the mass percentages of citric acid,Na2CO3,NaHCO 3 and F108 in effervescent tablets were 1.29:0:0.74:0.3,the graphene effervescent tablets through effervescent tablets were the easiest to re-disperse in water,and the mass fraction of graphene was as high as 30%.In addition,the concept of effervescent tablets is applicable not only to graphene,but also to other two-dimensional nanomaterials(MoS2,BN,MXene).(3)Graphene/epoxy resin composites were prepared by ultrasonic treatment and vacuum filtration.The 3D graphene skeleton with 9 cm diameter,3 cm thickness and complete thermal conductivity was successfully prepared.Moreover,when the content of graphene is 13.6 wt%,the in-plane and out-of-plane thermal conductivities of three-dimensional graphene/epoxy composites are 12.4 W/m.K and 6.26 W/m.K,respectively,which are about 68 times and 34 times higher than those of pure epoxy resin. |
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