Improved Ceramic Heat Exchanger Materials.

Numerous compositions were developed and evaluated for potential application as heat exchanger structures in automative gas turbine engines. Test specimens in the form of small monolithic bars were evaluated for thermal expansion and dimensional stability before and after exposure to sea salt and sufuric acid, followed by short and long term cycling at temperatures up to 1200 C 2192 F. Materials which survived the screening tests were considered for fabrication into honeycomb form. The material finally selected, GE-7808, consists of the oxides, ZrO2-MgO-Al203-SiO2, and is described generically as ZrMAS. The original version on which the primary work was done was based on a commercially available cordierite MAS frit. Late in the program, however a claytalc mixture was demonstrated to be a satisfactory very low cost source of the cordierite MAS phase.