We have investigated several methods to reduce reflectance and scattering levels from a selected group of highly absorbing materials. Each material has vastly different morphologies but similar reflectance and scattering levels. The highly absorbing materials considered in this study include: fibrous black appliques, carbon aerogels, Martin Black, and Enhanced Martin Black. Our investigation reveals that for the fibrous appliques, the fiber area density and length are the dominant factors in determining their absorption properties. For the porous materials that utilize cavities to absorb and trap incident radiation, our results indicate that the cavity geometry and surface pore density are the dominant factors in determining the effectiveness of a porous applique in absorbing light. With regards to the carbon aerogels, the aerogel porosity has the largest impact on its absorption levels. Finally, in order to reduce the reflectance properties of the anodized surfaces requires modifying the surface structure and dye characteristics.
We present comparisons of the optical, surface, and physical properties of morphologically variant black materials used to suppress reflected and scattered stray light. The black materials in this study include: carbon aerogel, black appliqués, and anodized surfaces. Each material utilizes a different geometry and material properties to absorb incident radiation. The optical measurements in this paper cover the ultraviolet to the infrared spectral regions and include: Bi-directional Reflectance Distribution Function (BRDF), Directional Hemispherical Reflectance (DHR) as a function of incidence angle and incident polarization state, and infrared reflectance microscopy. In addition, the surface and constituent properties of the black materials are measured by scanning electron microscopy (SEM), stylus profilometry, and energy dispersive spectroscopy (EDS). Finally, we present optical constant estimates for two of the black materials studied.
We have investigated the degree of polarization (DOP) of infrared radiation reflected from rough white and black materials. Mueller matrices for these materials have been measured with an out-of-plane scatterometer with full polarization optics. We have compared the Mueller matrix data to the microfacet model. These results may have applications for stray light coatings for imaging polarimetric instruments.
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