Meier S R, Korwin M L, Merzbacher C I
Optical Sciences Division, US Naval Research Laboratory, Washington, DC 20375, USA.
Appl Opt. 2000 Aug 1;39(22):3940-4. doi: 10.1364/ao.39.003940.
We present directional hemispherical reflectance (DHR) and bidirectional reflectance distribution function (BRDF) measurements of a carbon aerogel in the 2.5-14.3-microm infrared spectral region. The measured DHR is 1.0-1.2 +/- 0.2% throughout the 2.5-14.3-microm infrared wavelength region. When the incidence angle is increased from 8 degrees to 30 degrees 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 microm, indicate that carbon aerogel exhibits Lambertian behavior. The carbon aerogel's BRDF value of 4 x 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 <or=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.
我们给出了碳气凝胶在2.5 - 14.3微米红外光谱区域的定向半球反射率（DHR）和双向反射分布函数（BRDF）测量结果。在整个2.5 - 14.3微米红外波长区域，测得的DHR为1.0 - 1.2 +/- 0.2%。当入射角从与法线偏离8度增加到30度时，DHR仅增加0.2%；也就是说，由于非垂直红外辐射的照射，性能不会显著下降。在10.6微米波长处获得的BRDF测量结果表明，碳气凝胶呈现朗伯特性。碳气凝胶4×10^(-3) sr^(-1)的BRDF值与其测得的DHR值一致。气体吸附和透射电子显微镜表明，其结构以尺寸小于或等于10纳米的颗粒和孔隙为主。扫描电子显微镜揭示了尺度为几十纳米的表面粗糙度。碳气凝胶的DHR和BRDF与两种广泛使用的非反射材料马丁黑和里皮相比具有优势。
