TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The unitary graphene material further contains a filler or reinforcement phase dispersed in unitary graphene material to form a unitary graphene matrix composite structure. The filler or reinforcement phase contains metal, ceramic, glass, polymer, carbon and/or graphite in the form of particle, filament, nano-tube, nano-wire and/or nano-rod. The filler phase is chosen from carbon or graphite fiber, carbon or graphite nano-fiber, carbon nano-tube, carbon nano-rod, meso-phase carbon particle, meso-carbon micro-bead, expanded graphite flake having thickness of more than 100 nm, single-layer graphene sheet, multi-layer graphene platelet having thickness of less than 100 nm, exfoliated graphite or graphite worm, coke particle, needle coke, carbon black or acetylene black particle and/or activated carbon particle. The content of carbon, graphite, or graphene filler phase is 0.01- 99 wt.% based on total weight of composite structure. The inorganic coating contains ceramic material, diamond, semiconductor element or compound chosen from silicon, germanium, gallium, gallium nitride, gallium phosphide, gallium arsenide, aluminum nitride, aluminum phosphide, aluminum arsenide, boron nitride, boron phosphide and/or boron arsenide. The ceramic material is chosen from metal nitride, metal phosphide, metal arsenide, metal antimonite, metal oxide, metal sulfide, metal selenide, metal telluride and/or metal halogenide. The unitary graphene material has oxygen content of less than 5%. The graphene oxide gel is a homogeneous solution comprising graphene oxide molecules dispersed in liquid acidic medium having pH value of 5 or less. Preferred Property: The inorganic coating layer has thermal conductivity of more than 30 W/mK. The unitary graphene material has thermal conductivity of 100 W/mK or more, electrical conductivity of less than 3000 S/cm, degree of graphitization of 40% or more and mosaic spread value of less than 0.7. The unitary graphene matrix composite has physical density of 1.8 g/cm3 or more, porosity level of less than 5% and tensile strength of more than 40 MPa. The graphene oxide molecules have molecular weight of less than 4000 g/mole.