Carbon aerogel: a new nonreflective material for the infrared

摘要

We present directional hemispherical reflectance (DHR) and bidirectional reflectance distribution function (BRDF) measurements of a carbon aerogel in the 2.5-14.3-μm infrared spectral region. The measured DHR is 1.0-1.2±0.2% throughout the 2.5-14.3-μm infrared wavelength region. When the incidence angle is increased from 8° to 30° off normal, the DHR increases by only 0.2%; i.e., performance does not significantly degrade as a result of illumination by off-normal infrared radiation. BRDF measurements, obtained at a wavelength of 10.6 μm, indicate that carbon aerogel exhibits Lambertian behavior. The carbon aerogel's BRDF value of 4×10~(-3) sr~(-1) is consistent with its measured DHR values. Gas adsorption and transmission-electron microscopy indicate a structure dominated by particles and pores of≤10-nm dimension. Scanning-electron microscopy reveals surface roughness on a scale of tens of nanometers. The DHR and BRDF of carbon aerogel compare favorably with those of Martin Black and Rippey, two widely used nonreflective materials.