▎ 摘　　要

NOVELTY - A unitary graphene matrix composite comprises: unitary graphene matrix having closely packed and chemically bonded graphene planes having inter-graphene plane spacing of 0.335-0.40 nm and oxygen content of 0.001-10 wt.%, which unitary graphene matrix is obtained from heat-treating graphene oxide gel at higher than 100 degrees C and contains no discrete graphene platelets derived from gel; and carbon or graphite filler phase selected from e.g. carbon or graphite fiber/nanofiber, carbon nanotube, meso-phase carbon particle, carbon black or acetylene black particle and/or activated carbon particle. USE - As unitary graphene matrix composite (claimed) for heat dissipation applications; for thermal management applications (e.g. for use as a heat spreader) in a microelectronic device, such as a mobile phone (including a smart phone), a notebook computer, a tablet, an e-book, a telecommunication device, and any hand-held computing device or portable microelectronic device. ADVANTAGE - The unitary graphene matrix contains no complete grain boundary in it. The unitary graphene matrix composite has a physical density of at least 1.5 g/cm3 or a porosity level lower than 20 wt.%; or has a physical density of at least 1.7 g/cm3 or a porosity level lower than 10 wt.%. The composite exhibits a combination of exceptional thermal conductivity, electrical conductivity, mechanical strength, surface hardness, and scratch resistance. The composite has a thermal conductivity greater than 400 W/mK and/or electrical conductivity greater than 1000 S/cm when the heat-treating temperature is 100 degrees C to 1000 degrees C. The composite has a thermal conductivity greater than 600 W/mK and/or electrical conductivity greater than 2000 S/cm, when the heat-treating temperature is 1000 degrees C to 1500 degrees C. The composite has a thermal conductivity greater than 1000 W/mK and/or electrical conductivity greater than 3000 S/cm, when the heat-treating temperature is 1500 degrees C to 2500 degrees C. The composite has a thermal conductivity greater than 1500 W/mK and/or electrical conductivity greater than 5000 S/cm when the heat-treating temperature is 2500 degrees C to 3250 degrees C. The unitary graphene matrix composite has Rockwell hardness value greater than 80. The unitary graphene matrix composite has an electrical conductivity greater than 1500 S/cm, a thermal conductivity greater than 600 W/mK, a physical density greater than 1.8 g/cm3, and/or a tensile strength greater than 80 MPa; or has electrical conductivity greater than 3000 S/cm, a thermal conductivity greater than 1000 W/mK, a physical density greater than 1.9 g/cm3, and/or a tensile strength greater than 120 MPa; or has electrical conductivity greater than 5000 S/cm, a thermal conductivity greater than 1500 W/mK, a physical density greater than 2.0 g/cm3, and/or a tensile strength greater than 150 MPa. The composite exhibits a combination of exceptionally high thermal conductivity, high electrical conductivity, high mechanical strength, good surface scratch resistance, and good hardness. The composite exhibits a combination of exceptional thermal conductivity, electrical conductivity, mechanical strength, surface smoothness, surface hardness, and scratch resistance unmatched by any thin-film material of comparable thickness range. The composite overcomes all the major problems associated with the flexible graphite foil produced by re-compression of exfoliated graphite worms or exfoliated graphite flakes of natural graphite and/or artificial graphite. DETAILED DESCRIPTION - A unitary graphene matrix composite comprises: (a) a unitary graphene matrix containing closely packed and chemically bonded graphene planes having an inter-graphene plane spacing of 0.335 to 0.40 nm and an oxygen content of 0.001 wt.% to 10 wt.%, which unitary graphene matrix is obtained from heat-treating a graphene oxide gel at a temperature higher than 100 degrees C and contains no discrete graphene platelets derived from the graphene oxide gel; and (b) a carbon or graphite filler phase selected from a carbon or graphite fiber, carbon or graphite nanofiber, carbon nanotube, carbon nano-rod, meso-phase carbon particle, meso-carbon micro-bead, exfoliated graphite flake with a thickness greater than 100 nm, exfoliated graphite or graphite worm, coke particle, needle coke, carbon black or acetylene black particle, and/or activated carbon particle, where the carbon or graphite filler phase occupies a weight fraction of 0.01 wt.% to 99 wt.% based on the total composite weight and the carbon or graphite filler phase is in a particulate, filamentary, or rod-like form dispersed in the unitary graphene matrix. An INDEPENDENT CLAIM is included for a process for producing the unitary graphene matrix composite involving: either a1) preparing a graphene oxide gel having graphene oxide molecules dispersed in a fluid medium, where the graphene oxide gel is optically transparent or translucent; b1) mixing the carbon or graphite filler phase in the graphene oxide gel to form a slurry; c1) dispensing the slurry onto a surface of a supporting substrate or a cavity of a molding tool; d1) partially or completely removing the fluid medium from the slurry to form a composite precursor; and e1) heat-treating the composite precursor to form the unitary graphene composite at a temperature higher than 100 degrees C; or a2) preparing a graphene oxide gel having graphene oxide molecules dispersed in a fluid medium, where the graphene oxide gel is optically transparent or translucent; b2) forming the carbon or graphite filler phase into a desired porous shape having pores in it, and impregnating the graphene oxide gel into the pores of the desired porous shape to form an impregnated shape; c2) partially or completely removing the fluid medium from the impregnated shape to form a composite precursor; and d2) heat-treating the composite precursor to form the unitary graphene composite at a temperature higher than 100 degrees C; or a3) preparing a graphene oxide gel having graphene oxide molecules dispersed in a fluid medium, where the graphene oxide gel is optically transparent or translucent; b3) combining the carbon or graphite filler phase and the graphene oxide gel to form a graphene oxide gel-impregnated shape of fiber yarns or bundles; c3) partially or completely removing the fluid medium from graphene oxide gel-impregnated shape to form a composite precursor; and d3) heat-treating the composite precursor to form the unitary graphene composite at a temperature higher than 100 degrees C.