Characterization of siloxane-infiltrated ceramics microstructure by spectral scattering in the near infrared

Abstract

The spectral scattering technique is considered to estimate the scatterers (pores) size distribution. It is based on the fitting of spectral scattering coefficients determined by Mie theory and radiative transfer inverse problem solution. The previously proposed method was improved for multiphase system analysis. The spectral directional-hemispherical reflectances of slabs of not less than two different geometrical thicknesses are used for inverse radiative transfer problem solution. Semitransparent ceramics with less than 10–15% of total porosity, that contains homogeneously distributed close to solid sphere scatterers, is the application object of the proposed technique. General expressions for multiphase systems were simplified to three-phase ones to reduce the number of optimization variables and adapted to the evaluation of semitransparent ceramics infiltrated by the polymer.The proposed technique was implemented for the evaluation of silica ceramics with 10% porosity before and after the infiltration by the methyl-phenyl-spirocyclosiloxanol followed by the polyfunctional condensation to obtain the polymethyl-phenyl-spirocyclosiloxane. Two techniques of ceramics infiltration with the low-molecular polymer viz by the solution and by the melt were compared. Size distributions of the polymer-filled pores was shown to be affected by the infiltration procedure and polymerization regime. It was shown that less than 25% of the initial pore volume appears to be polymer-filled in the case of ceramics infiltration by the solution. Infiltration from the melt fills not less than 80% of the pore volume. The mean pore diameter of air-filled pores was estimated by gas/mercury porometry and spectral scattering technique. Both methods are shown to be in a rather good agreement. By these techniques air-filled pores mean diameters were shown to be 0.37 and 0.44 µm respectively for ceramics before the infiltration and 0.54 and 0.55 µm for the ceramics infiltrated through the solution. The spectral scattering technique shows mean diameter of polymer-filled pores to be 0.11–0.17 and 0.49 µm in the cases of ceramics infiltration by the solution and by the melt respectively. Thus, sizes of polymer-filled pores are shown to be shifted to the higher values because of infiltration by the melt. The obtained data on polymer-filled pores sizes may be useful for the analysis of ceramics strengthening by the polymer infiltration and infiltration procedure optimization.