Process for producing unitary graphene matrix composites containing carbon or graphite fillers

A process for producing a unitary graphene matrix composite, said process comprising:

• (a) preparing a graphene oxide gel having graphene oxide molecules dispersed in a fluid medium, wherein the graphene oxide gel is optically transparent or translucent;
• (b) mixing a carbon or graphite filler phase in said graphene oxide gel to form a slurry;
• (c) dispensing said slurry onto a surface of a supporting substrate or a cavity of a molding tool;
• (d) partially or completely removing said fluid medium from the slurry to form a composite precursor;
• and (e) heat-treating the composite precursor to form said unitary graphene composite at a temperature higher than 100° C.;
• wherein said unitary graphene matrix composite contains 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% to 10% by weight, and said carbon or graphite filler phase is selected from a carbon or graphite fiber, carbon or graphite nano-fiber, carbon nano-tube, 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, activated carbon particle, or a combination thereof.