Enhanced specific surface area and thermal conductivity in ultrathin graphite foams grown by chemical vapor deposition on sintered nickel powder templates

Abstract

The specific surface area and effective thermal conductivity of ultrathin graphite foams (UGFs) grown by chemical vapor deposition (CVD) have been limited by the large pore sizes of reticulated nickel foam templates. Here we show that nickel templates formed by sintering of low-cost nickel powder can reduce pore size and increase specific surface area. Accordingly, the effective density of a free-stranding graphite foam grown on the high-surface area templates can be increased by an order of magnitude relative to one grown on a reticulated nickel foam template. This increase is accomplished without increasing the thickness of the CVD graphite or decreasing the structural quality of the graphite. Based on experiments with nickel powder with and without the reticulated nickel template present, we found that both the particle size and sintering temperature influenced template morphology. Because of a 68-times increase in the volumetric specific surface area of a graphite foam synthesized on a sacrificial sintered powder template compared to a UGF grown on a reticulated template, we have been able to increase the relative graphite density and effective thermal conductivity from 0.87 ± 0.09% to 8.4 ± 0.3% and from 2.1 ± 0.3 Wm−1K−1 to 16.3 ± 1.1 Wm−1K−1, respectively.