Preparation Of Graphene By Graphite Intercalation Expansion Stripping And Its Application In Conducting Materials

Flake graphite is a typical non-metallic ore with excellent electrical conductivity,thermal conductivity,high temperature resistance and other characteristics.Thus it has broad application prospects in the fields of electrical conductivity,anticorrosion and flame retardancy.According to the development demand of graphite deep processing industry,this paper systematically carried out the research on the deep processing technology of graphite-expanded graphite-graphene-graphene conductive coatings,which provided a certain theoretical basis for the deep processing of graphite and the development of high-end graphite materials.The oxidation intercalation of graphite was studied with peracetic acid as oxidant and concentrated sulfuric acid as intercalator intercalating agent.The results showed that the expanded volume of expandable graphite could reach 200 mL/g under the conditions of concentrated sulfuric acid and flake graphite volume mass ratio of 16:1,peroxyacetic acid to graphite volume mass ratio of 3:1,and reaction time of 2 h.Its main technical indicators meet the KP300-?type superior product indicators in GB10698-89.Expansion conductivity research showed that its electrical conductivity had a negative correlation with the graphite expansion volume.The larger the graphites expansion volume,the lower its order,the more pores it has,the greater the contact resistance,and the lower the electrical conductivity of the flexible graphite.Using K₂S₂O₈-H₂SO₄ as the expansion system,an experimental study was carried out to prepare expanded graphite at room temperature in one-step.The results showed that expanded graphite with an expansion volume of 150 mL/g was obtained with a solid-liquid ratio of 9%to concentrated sulfuric acid,a mass ratio of potassium persulfate to flake graphite of 7:1,and a reaction time of 90 min.The preparation of expanded graphite by rapid expansion under low temperature heating showed that under the conditions of the ratio of flake graphite to concentrated sulfuric acid of 5%,and the mass ratio of potassium persulfate to flake graphite of 7:1,the expanded graphite was heated in water bath for 5 min,and the expanded volume of graphite can reach 150 mL/g.The main technical indicators of the prepared expanded graphite meet the KP300-?type requirements in the national standard GB10698-89.The process of preparing expanded graphite in the K₂S₂O₈-H₂SO₄ system was simpler,and the process without high temperature was more energy saving.Potassium persulfate had a very low degree of oxidation of graphite and did not cause graphite peroxidation.With the expanded graphite as the raw material,the experimental studied on the preparation of graphene by stripping expanded graphite by chemical one-step method was carried out.The results showed that the yield of graphene could reach 74%under the optimized conditions of the mass volume ratio of expanded graphite to concentrated sulfuric acid was0.5:40,the mass ratio of expanded graphite to potassium persulfate was 0.5:8,and the reaction time was 5 h.About 90%of the obtained graphene was oligospheric graphene,and about 88%of the graphene sheet size was less than 12?m.About 12%of graphene sheet size was greater than 12?m.The conductivity of graphene was 1.85×10⁴ S/m,and the ash content was 1.01%.The method can effectively preserve the perfect crystal structure of graphite.The study on the preparation of graphene by exfoliating expanded graphite by ultrasonic method showed that the graphene obtained under the condition of 4 times of expansion and 20 min of ultrasonic time.The yield of graphene was 80%,and the sheet size was mainly distributed in 2¹0?m,among which the content of oligoskeletal graphene accounted for 80%.The ash content of the sample was 4.94%,and its conductivity was 3.52×10⁴ S/m.After the expansion of graphite,its tight lamellar structure was damaged,and easy to peel off.Graphite was easier to exfoliate after expansion,and increasing the times of graphite expansion can effectively improve the degree of graphite peeling.The obtained graphene was used as a raw material,and a graphene/waterborne polyurethane conductive coating application research was carried out.The results showed that as the amount of graphene added increased,the resistivity of the coating gradually decreased.When the content of graphene reaches 14wt%,the resistivity of the coating changes little.When the concentration of the graphene dispersion was 0.06 mg/ml and the thickness of the coater was 200?m,the resistivity of the prepared coating was 43.8?·cm.The conductive behavior of conductive coatings was in accordance with the percolation theory,and there were contact and tunnel conduction.