Thermally and electrically insulating porous SiC ceramics are attractive candidates for Flow Channel Inserts (FCI) in dual-coolant blanket concepts thanks to its relatively inexpensive manufacturing route. To prevent tritium permeation and corrosion by Pb-15.7 a dense coating has to be applied on the porous SiC. Despite not having structural function, FCI must exhibit sufficient mechanical strength to withstand strong thermal gradients and thermo-electrical stresses during operation. This work summarizes the results on the development of coated porous SiC for FCI. Porous SiC was obtained following the sacrificial template technique, using Al2O3 and Y2O3 as sintering additives and a carbonaceous phase as pore former. Sintering was performed in inert gas at 1850-1950 degrees C during 15 min to 3 h, followed by oxidation at 650 degrees C to eliminate the carbonaceous phase. The most promising bulk materials were coated with a similar to 30 mu m thick dense SiC by CVD. Results on porosity, bending tests, thermal and electrical conductivity are presented. The microstructure of the coating, its adhesion to the porous SiC and its corrosion behavior under Pb-17.5Li are also shown.

SiC is the primary candidate for the flow channel inserts in dual-coolant blanket concepts. Porous SiC ceramics are attractive candidates for this non-structural application, since they can satisfy the required properties through a low cost manufacturing route, compared to SiC(f)/SiC. This work shows first results of the manufacturing of porous SiC ceramics prepared with different amounts of Y(2)O(3) and Al(2)O(3) as sintering additives. C powders were used as pore-formers by their burnout during oxidation after sintering. Comparison of microstructure, porosity, flexural strength, thermal and electrical conductivity and corrosion under Pb-15.7Li of porous SiC without and with sintering additives is presented. The addition of 2.5 wt.% of Y(2)O(3) and Al(2)O(3) improves the mechanical properties, and reduces the thermal and electrical conductivity down to reasonable values. Preliminary corrosion tests under Pb-15.7 Li at 500 degrees C show that the absence of a dense coating on porous SiC leads to poor corrosion behavior. (C) 2011 Elsevier B.V. All rights reserved.