▎ 摘　　要

NOVELTY - A magnetorheological paste or gel comprises carbon dispersed in a polymer including graphene nanoflakes dispersed in polymer, where the paste or gel has a viscosity of 0.1-200 kPa-second under magnetic field of 0-1.2 T. USE - Magnetorheological paste or gel. ADVANTAGE - The magnetorheological paste or gel exhibits magnetic signals. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) a method of synthesizing a magnetorheological paste or gel comprising graphene nanoflakes and polymer, comprising mixing a polymer with deionized water; adding synthesized graphene nanoflakes to solvent polymer mixture and homogenizing to form raw colloids; heating the homogenous raw colloids at 85-95 degrees C under reflux for 1-3 hours to yield an intermediate gel; cooling and holding the intermediate gel at a reduced temperature for vaporizing water; and cooling the formed gel to room temperature to obtain homogenous gel; and (2) a method of synthesizing graphene nanoflakes comprising mixing the graphite powder with sulfuric acid and keeping at high temperature; adding potassium persulfate and phosphorus pentoxide to the reaction mixture and keeping for pre-oxidation of graphite; cooling the mixture and adding distilled water; centrifuging, collecting the particle phase, washing with distilled water and allowing to sediment overnight, collecting and drying the sediment (preoxidized graphite oxide); adding sulfuric acid to the dry pre-oxidized graphite oxide at ice-cold condition followed by addition of potassium permanganate to this mixture slowly under constant stirring; stirring the mixture at ice-cold conditions; adding distilled water and hydrogen peroxide and keeping the mixture for overnight; decanting the solution and washing the precipitate with hydrochloric acid, and centrifuging to collect graphene oxide; dispersing the graphene oxide in water and heating and adding finely powdered sodium borohydride under stirring; centrifuging the solution to collect the sediment, washing the sediment with water and drying; re-dispersing graphite oxide in deionized water and ultrasonicating using a probe ultrasonicator; heating the graphite oxide solution and adding hydrazine hydrate, stirring to obtain the black precipitate of reduced graphene oxide or graphene, collecting by centrifuging and washing with distilled water and drying to obtain powder.