▎ 摘　　要

NOVELTY - A multilayer composite thermally conductive film has a nanocellulose film as intermediate layer, and nanocellulose/graphene film layer or nanocellulose/boron nitride film layer coated on the upper and lower surfaces of nanocellulose film. The layer-to-layer is formed by hydrogen bond between cellulose substrates to form composite thermally conductive film of ABA three-layer structure. The mass of each layer of the film is 15-30 mg. The doping amount of graphene in nanocellulose/graphene film layer is 6-10 wt.%. The doping amount of boron nitride in nanocellulose/boron nitride film layer is 6-10 wt.%. USE - Multilayer composite thermally conductive film is used in heat dissipation component. ADVANTAGE - The multilayer composite thermally conductive film has high thermal conductivity, mechanical property and electrical insulation property. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of multilayer composite thermally conductive film. Nanocellulose and graphene are dispersed in an aqueous solution in the mass ratio of 100:6-10 to form a dispersion (a) having concentration of 1.5-2 mg/mL. Nanocellulose and boron nitride are dispersed in an aqueous solution in the mass ratio of 100:6-10 to form dispersion (b) having concentration of 2-2.5 mg/mL.The obtained dispersion (a) is poured onto a filter until it is dried to obtain nanocellulose/graphene film or nanocellulose/boron nitride film. The nanocellulose dispersion having concentration of 2 mg/mL, is poured on the obtained film, and drained to obtain nanocellulose film and nanocellulose/graphene film or composite film of nanocellulose/boron nitride film. The obtained dispersion (a) is further subjected to layer of nanocellulose film of composite film, and dried to obtain composite thermally conductive film of ABA three-layer structure. The composite thermal conductive film of ABA three-layer structure, is compressed, placed on two steel plates, and vacuumizing at 40-60 degrees C to obtain symmetrical three-layer composite thermal conductive film.