Technology assessment of ceramic joining applicable to heat exchangers. Technical planning study TPS-77-748. Final report

The use of metal heat exchangers for heat recovery in utility combined-cycle and indirect-fired gas turbine power plants is limited to a maximum temperature range of 800 to 900/sup 0/C. The use of ceramic heat exchangers offers the potential of higher operating temperatures and thus a higher efficiency. Joining ceramics was identified as a potential problem; this study confirms that the present state of the art of joining ceramics must be improved to obtain the full benefits of high-temperature ceramic heat exchangers. Mechanical joining, brazing, and solid-state bonding appear to be the most promising methods. Mechanical joining is limited to application with low applied stresses. Brazing, mainly using silicon metal, limits the maximum temperature to 1200 to 1300/sup 0/C. Solid-state bonding requires a high sintering temperature and is difficult to do under field conditions.