▎ 摘　　要

NOVELTY - Preparation of graphene-metal composite nanofluid involves preparing m-s-m-type Gemini surfactant containing two hydrophobic tail groups, two hydrophilic head groups, and a spacer to connect hydrophobic tail groups and hydrophilic head groups, preparing graphene oxide by Hummers method, ultrasonically dispersing graphene oxide in water or mixture of water and ethylene glycol to obtain graphene oxide suspension, adding m-s-m-type Gemini surfactant solution while dispersing to obtain surface-modified graphene oxide suspension, mixing the m-s-m-type Gemini surfactant solution with the metal precursor solution to obtain mixed solution, dripping mixed solution in surface-modified graphene oxide suspension, stirring at 50-80 degrees C, adding reducing agent, adjusting pH to 9-10 and reacting. The m-s-m-type Gemini surfactant is quaternary ammonium salt compound (I) or sulfonate compound (II). The quaternary ammonium salt compound is prepared from fatty alkyl dimethyl tert-amine and dibromoalkane. USE - Preparation of graphene-metal composite nanofluid for micro-pipeline blockage application. ADVANTAGE - The preparation method is simple and easy, and produces graphene-metal composite nanofluid with improved thermal conductivity and excellent thermal stability. The graphene-metal composite nanofluid can exist stably for long time and effectively prevent the sedimentation caused by the agglomeration of composite nanomaterials, and effectively solves the problem of micro-pipeline blockage in the application process. DETAILED DESCRIPTION - Preparation of graphene-metal composite nanofluid involves preparing m-s-m-type Gemini surfactant containing two hydrophobic tail groups, two hydrophilic head groups, and a spacer to connect hydrophobic tail groups and hydrophilic head groups, preparing graphene oxide by Hummers method, ultrasonically dispersing graphene oxide in water or mixture of water and ethylene glycol to obtain graphene oxide suspension, adding m-s-m Gemini surfactant solution while dispersing to obtain surface-modified graphene oxide suspension, mixing m-s-m-type Gemini surfactant solution with the metal precursor solution to obtain mixed solution, dripping the mixed solution in surface-modified graphene oxide suspension, stirring at 50-80 degrees C, adding reducing agent, adjusting pH to 9-10 and reacting for 1.5-3 hours. The m-s-m-type Gemini surfactant is quaternary ammonium salt compound of formula (I) or sulfonate compound of formula (II). The quaternary ammonium salt compound is prepared from fatty alkyl dimethyl tert-amine and dibromoalkane. The sulfonate compound is prepared from primary alkylamine, 1,3-propanesultone and dibromoalkane. The fatty alkyl dimethyl tertiary amine is one of N-decyl-N,N-dimethyl tert-amine, N-dodecyl-N,N-dimethyl tert-amine, N-tetradecyl-N,N-dimethyl tert-amine and N-hexadecyl-N,N-dimethyl tert-amine. The dibromoalkane is one of 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, and 1,6-dibromohexane. The primary alkylamine is one of decylamine, dodecylamine, tetradecylamine, and hexadecylamine. m = 10, 12, 14 or 16;and = 2, 3, 4 or 6.