ABSORPTION SCATTERING COEFFICIENTS AND SCATTERING PHASE FUNCTIONS IN RETICULATED POROUS CERAMICS

Spectral absorption and scattering coefficients and spectral scatterin g 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 mu m. These spect ral radiative properties were investigated and quantified for 10 ppi ( pores/inch), 20 ppi, and 65 ppi materials. Radiative properties were r ecovered from spectral hemispherical reflectance and transmittance mea surements using inverse analysis techniques based upon discrete ordina tes radiative models. Two dual-parameter phase functions were investig ated for these materials: one based on the physical structure of retic ulated porous ceramics and the other a modified Henyey-Greenstein phas e function. The modified Henyey-Greenstein phase function provided the most consistent spectral radiative behavior that was relatively indep endent of wavelength across the wavelength spectrum studied. OB SiC al so demonstrated consistently higher absorption coefficients than PS Zr O2 at all wavelengths. Spectral scattering albedos of PS ZrO2 were dis covered to be in the range 0.81-0.999 and increased as ppi rating incr eased, while those for OB SiC were lower in the range of 0.55-0.888 an d decreased as ppi rating increased. The average extinction efficienci es for 0.4-5.0 mu m were discovered to be 1.45 for PS ZrO2 and 1.70 fo r OB SiC. Extinction coefficients were discovered to correlate well wi th geometric optics theoretical models and electromagnetic wave/fiber interactions models based on independent scattering and absorption mec hanisms.