▎ 摘　　要

NOVELTY - Graphene oxide is grafted on surface-modified carbon fiber by oxidizing graphite; peeling oxidized graphite in solvent (S) to obtain graphene oxide; functionalizing graphene oxide; functionalizing carbon fiber surface; and processing the graphene oxide on the carbon fiber surface. USE - Method for grafting graphene oxide on surface-modified carbon fiber (claimed). ADVANTAGE - The method can solve technical problems associated with existing carbon fiber having low surface activity, reduced surface tension and poor wettability with resin substrate, as well as the problem associated with carbon composite material having reduced interlaminar shear strength. The graphene oxide uniformly covers the surface of the carbon fiber, thus greatly improving the surface roughness of the carbon fiber. Further, the interfacial performance of the carbon fiber-reinforced composite material can be improved through anchoring action. The interfacial shear strength of the graphene oxide-grafted surface-modified carbon fiber/carbon composite material is improved by 25 % compared with that of the untreated carbon fiber/carbon composite material. DETAILED DESCRIPTION - Graphene oxide is grafted on surface-modified carbon fiber by: (1) oxidizing graphite; (2) peeling oxidized graphite in solvent (S) to obtain graphene oxide; (3) functionalizing graphene oxide; (4) functionalizing carbon fiber surface; and (5) processing the graphene oxide on the carbon fiber surface. Step (1) is performed by adding graphite into a mixture of strong oxidizing acid and nitrate; cooling to - 5-0 degrees C; stirring at 50-200 revolutions/minute (rpm); adding with potassium-containing strong oxidizing agent; continuously stirring for 4-12 hours; pouring the mixed liquid into water bath at 10-50 degrees C; continuously reacting for 40-60 minutes; adding with hot water at 90-100 degrees C; boiling for 20-40 minutes; adding with hydrogen peroxide solution having a volume concentration of 40-60 %; stirring at 100-500 rpm to completely dissolve; washing with ultrapure water for 3-6 times; filtering to obtain a filter cake that is free of sulfate ion (SO42-); and freeze-drying at - 35 degrees C to obtain oxidized graphite. In step (1), the mass ratio of graphite to strong oxidizing acid is 1:(0.025-5); the mass ratio of graphite to nitrate is 1:(0.2-8); the mass ratio of graphite to potassium-containing strong oxidizing agent is 1:(0.1-4); and the mass ratio of graphite to hydrogen peroxide is 1:(0.125-4). Step (2) is performed by dissolving the oxidized graphite obtained in step (1) in a solvent (S); ultrasonically oscillating for 0.5-12 hours under an ultrasonic power of 100-1000 W; centrifuging in a centrifugal machine at 3000-10000 rpm; and freeze-drying at - 35 degrees C to obtain graphene oxide powder. Step (3) is performed by adding tetrahydrofuran (THF) solution (200 mL), sodium borohydride (NaBH4) (8 g) and iodine (I2) (0.1 g) into a flask; stirring to dissolve; adding with graphene oxide powder obtained in step (2) (0.5 g); reacting for 2 hours; freeze-drying for 24 hours to obtain carboxylated graphene oxide; adding the carboxylated graphene oxide (0.0025 g) and distilled water (15 mL) into a flask; adding with silane coupling agent KH-550 (5 mL); reacting for 6 hours in water bath at 75 degrees C; centrifuging for 10 minutes at 12000 rpm; discarding supernatant liquid; adding with THF; centrifuging for 10 minutes at 12000 rpm; discarding supernatant liquid to obtain aminated graphene oxide-containing viscous fluid; and freeze-drying to obtain aminated graphene oxide. Step (4) is performed by winding the carbon fiber on square glass frame; soaking the resulting glass frame in mixed acid (A) contained in a flask; placing magnetic stirred into the flask; reacting for 8 hours under normal temperature; washing with deionized water until the washed liquid becomes neutral; drying for 24 hours at 100 degrees C under vacuum condition to obtain acid-oxidized carbon fiber; fixing the acid-oxidized carbon fiber with glass fiber wire; adding the acid-oxidized carbon fiber, thionyl chloride (160 mL) and dimethylformamide (20 mL) into three-mouth flask; reacting for 48 hours in water bath at 70 degrees C; washing with acetone until the washed liquid becomes neutral; and drying for 24 hours at 70 degrees C under vacuum condition to obtain acyl-chlorinated carbon fiber. The mixed acid (A) is composed of concentrated nitric acid and concentrated sulfuric acid with a volume ratio of 3:1. Step (5) is performed by dissolving the aminated graphene oxide obtained in step (3) in dimethylformamide; pouring into three-mouth flask; adding with acyl-chlorinated carbon fiber obtained in step (4) (based on 1:1 mole ratio of aminated graphene oxide to acyl-chlorinated carbon fiber); heating for 48 hours in water bath at 70 degrees C; washing with acetone until the washed liquid becomes neutral to obtain grafted carbon fiber; refluxing the grafted carbon fiber with acetone (150 mL); and drying for 24 hours at 60 degrees C under vacuum condition to obtain graphene oxide surface-grafted carbon fiber.