Evaluation of porous silicon carbide monolithic honeycombs as volumetric receivers/collectors of concentrated solar radiation

Porous monolithic multi-channeled silicon carbide (SiC) honeycombs employed as open volumetric receivers of concentrated solar radiation, were evaluated with respect to their porous structure and thermomechanical properties before and after long-time operation. Proper "tuning" of porosity, pore size distribution and microstructure can provide SiC honeycombs with improved mechanical properties (higher bending and compressive strength) in the "as-manufactured" state. Exposure under solar irradiation was found to affect both their pore structure and their mechanical characteristics. During the first stages of exposure, a re-structuring of the porous structure takes place shifting the mean pore size to higher values and slightly decreasing the total porosity; this re-structuring ceases after some "characteristic" exposure time. After solar exposure the honeycombs become harder and exhibit significantly higher compressive strength. Extension of anticipated lifetime can be achieved by materials with enhanced mechanical properties like silicon-infiltrated (sificonized) SiC. (c) 2006 Elsevier B.V. All rights reserved.