Thermal management with a highly emissive and thermally conductive graphite absorber

Abstract

Thermal management on a variety of length scales is essential for many industrial, solar and computational systems. Here we explore the thermal properties of a nearly perfect graphite absorber with both high emissivity and thermal conductivity which is fabricated by simple one-step etching. The hemispherical reflectance of the absorber is around 1% in the visible range and the normal specular reflectance is less than 1% from 1.5 μm to 10 μm. The thermal conductivity of the absorber is measured above 630 Wm-1K-1, which is 2.5 times larger than the aluminum used in commercial heat sinks. Heat dissipation testing indicates that a device is 3.7 ± 2 degrees cooler with the graphite absorber as the heat spreader than a pristine graphite sheet and 9.1 ± 2 degrees cooler than an Au-coated graphite sheet, primarily due to improved radiation cooling. A theoretical analysis accounts for the results. Further analysis suggests that the radiative heat dissipation is more prominent in the low-convection environment, especially for a convection coefficient below 10 Wm-2K-1.