Enhancement of cross-plane thermal conductivity and mechanical strength via vertical aligned carbon nanotube@graphite architecture

A three-dimensional (3D) carbon nanotube/exfoliated graphite block (CNT/EGB) was prepared by growing vertical aligned carbon nanotube (VACNT) at the surface of SiO2-coated exfoliated graphite plate (EGP) through chemical vapor deposition followed by hot-pressing. In such 3D CNT/EGB, EGPs were bridged by the VACNTs in the cross-plane direction, and the interface between EGPs and VACNTs was covalently bonded by SiC which formed by reaction of SiO2 and the adjacent carbon of EGPs and VACNTs. The length and growth density of VACNTs were adjusted by the growth time and concentration of catalysts. Thermal conductivity and mechanical strength of CNT/EGB were controlled by the growth states of VACNTs and hot-pressing. CNT/EGB showed a maximum cross-plane thermal conductivity (k⊥) of 38 W/mK, which is more than twice as much as that of EGB (14 W/mK). A remarkable increase in k⊥ was attributed to the efficient heat flow of VACNTs bridging EGPs in the cross-plane direction and the thermal conductive SiC interface between VACNTs and EGPs. Additionally, the increased bending (76 MPa) and compressive strength (59 MPa) of CNT/EGB was due to the combination of strong pull-out effect of high-density nanotubes and the strong covalent interconnections between VACNTs and EGPs.