Thermal Conductivity and Interface Thermal Conductance in Composites of Titanium With Graphene Platelets

Composite films of graphene platelets (GPs) in titanium matrix were prepared on silicon (001) substrates by physical vapor deposition of titanium using magnetron sputtering and dispersion of graphene platelets. The graphene platelets were dispersed six times after each deposition of titanium film to form the composite film. Samples of titanium film and titanium film with a single layer of dispersed graphene platelets were also prepared by the same procedure. The distribution of the graphene platelets in the film was analyzed by scanning electron microscopy. Energy dispersive spectrometry was used to infer the absence of interstitial elements. The thermal conductivity of the composite and the interface thermal conductance between titanium and silicon or titanium and graphene platelets was determined by three-omega and transient thermo reflectance (TTR) techniques, respectively. The results indicate that the thermal conductivity of the composite is isotropic and improved to 40Wm(-1)K(-1) from 21 Wm(-1)K(-1) for Ti. The interface thermal conductance between titanium and silicon is found to be 200 MWm(-2)K(-1) and that between titanium and graphene platelets in the C-direction to be 22 MWm(-2)K(-1). Modeling using acoustic and diffuse mismatch models was carried out to infer the magnitude of interface thermal conductance. The results indicate that the higher value of interface thermal conductance between graphene platelets in the ab plane and titanium matrix is responsible for the isotropic and improved thermal conductivity of the composite. Effective mean field analysis showed that the interface thermal conductance in the ab plane is high at 440 MWm(-2)K(-1) when GPs consist of 8 atomic layers of graphene so that it is not a limitation to improve the thermal conductivity of the composites.