Absorption/Scattering Coefficients and Scattering Phase Functions in Reticulated Porous Ceramics

Abstract

Spectral absorption and scattering coefficients and spectral scattering phase functions have been derived for partially stabilized zirconia (PS ZrO2) and oxide-bonded silicon carbide (OB SiC) reticulated porous ceramics (RPCs) across the wavelength range 0.4–5.0 μm. These spectral radiative properties were investigated and quantified for 10 ppi (pores/inch), 20 ppi, and 65 ppi materials. Radiative properties were recovered from spectral hemispherical reflectance and transmittance measurements using inverse analysis techniques based upon discrete ordinates radiative models. Two dual-parameter phase functions were investigated for these materials: one based on the physical structure of reticulated porous ceramics and the other a modified Henyey–Greenstein phase function. The modified Henyey–Greenstein phase function provided the most consistent spectral radiative properties. PS ZrO2 radiative properties exhibited strongly spectrally dependent behavior across the wavelength range studied. OB SiC radiative properties exhibited radiative behavior that was relatively independent of wavelength across the wavelength spectrum studied. OB SiC also demonstrated consistently higher absorption coefficients than PS ZrO2 at all wavelengths. Spectral scattering albedos of PS ZrO2 were discovered to be in the range 0.81–0.999 and increased as ppi rating increased, while those for OB Sic were lower in the range 0.55–0.888 and decreased as ppi rating increased. The average extinction efficiencies for 0.4–5.0 μm were discovered to be 1.45 for Ps ZrO2 and 1.70 for OB SiC. Extinction coefficients were discovered to correlate well with geometric optics theoretical models and electromagnetic wave/fiber interaction models based on independent scattering and absorption mechanisms.