Fabrication of graphite/Cu composite foils with ultrahigh thermal conductivity by adding an intermediate nickel layer and vacuum hot pressing treatment

Abstract Copper/nickel coated graphite film/copper sandwich composite foils were fabricated by electro-deposition and subsequent vacuum hot pressing treatment. Intermediate nickel layers with different volume faction (5%, 10%, 15%, and 20%), which was calculated corresponds to the proportion between graphite film and Ni coating, were introduced to modify the interfacial bonding between graphite film and deposited copper. The effect of the vacuum hot pressing (VHP) parameters on the in-plane thermal conductivity (TC) was investigated systemically. The results showed that the existence of intermediate nickel layer could improve the interfacial bonding between graphite and copper, thus enhance the thermal conductivity of the fabricated composite foils. The maximum TC value of the composite foil (graphite volume fraction of 50 vol% with 10 vol% intermediate nickel layers) reached up to 1042.4 W m−1 K−1 after VHP treatment at the optimal process parameters (800 ℃, 60 min and 40 MPa). These composites possess higher in-plane thermal conductivities than graphite flake/copper composites due to well-controlled graphite/copper interfacial bonding and fabrication parameters.