Novel plate‐type heat exchangers (HXs) with high‐power densities are proposed based on novel integrated flow channel designs. Net‐shape plates were achieved by the molding of powder mixtures to wood‐based composites (WBC's). HX stacks are built by plate‐to‐plate joining followed by pyrolysis and silicon melt infiltration. The C/SiSiC provided with PyC–SiC coating was gas‐tight to helium up to 5.5 MPa. Corrosion tests with coupons were performed using a ternary eutectic fluoride salt (FLiNaK) as the intermediate heat transfer fluid. While SiC is vulnerable to corrosion by the salt, the coating offers a high degree of protection to the ceramic substrate.

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Non-oxide SiC ceramics can withstand high temperatures ~1400 °C in severe combustion environments. Therefore such ceramics are interesting candidates for advanced combustion technologies, e.g. sophisticated porous burners. For the fabrication of porous SiSiC ceramics the DLR developed a new technology based on carbon sheets and lamellae. These basic materials can be combined to lightweight 3D C/C stacks. Through the variation of the amplitude and number of lamellae per inch, the open porosity and orientation of the pore channels could be tailored in a wide range. By using the pyrolysis followed by the liquid silicon-melt infiltration process the carbon stack could be directly converted into SiC in one shot. The residual open porosity can easily be filled with pure silicon to obtain 3D SiSiC structures with adequate mechanical strength and sufficient damage tolerance. Best results from durability tests were obtained with structures which are composed of oriented pore channels. Suitable structures should have angles (α) of about α = ± 60° or less. The results from burner rig tests at LSTM with improved components have been very promising, since a lifetime up to 500 hours and 2000 start-ups could be obtained with α = ± 50° as well as with α = ± 60° sample. So far, no significant oxidation or degradation could be observed after 1939 h/10800 start-ups with α = ± 45° sample. These proof tests are ongoing and show that these novel cardboard like structures have a high potential for industrial applications.

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