(Invited) The Effect of Heat-Treatment on Mechanical Property and Wetting Behavior of α-LiAlO2

Tuesday, 30 May 2017: 17:10
Grand Salon B - Section 9 (Hilton New Orleans Riverside)
L. Gao, J. R. Selman, and P. Nash (Illinois Institute of Technology, Thermal Processing Technology Center)
α-LiAlO2 is widely used as membrane structural material to support electrolyte in molten carbonate fuel cell (MCFC) stacks. The α-LiAlO2 electrolyte matrix always experiences mechanical and thermal stress during the initial start-up and operation (550-650oC) due to (1) insufficient mechanical strength of non-sintered α-LiAlO2, (2) thermal expansion coefficient difference between the α-LiAlO2 matrix and carbonate electrolyte, and (3) high capillary force, which may cause cracking of the matrix. A non-sintered/heat-treated pure α-LiAlO2 matrix has low mechanical strength. In this study, heat-treatment was used to enhance the mechanical strength of the α-LiAlO2 matrix. It has been found that the mechanical strength of the α-LiAlO2 matrix was increased four folds (2.72MPa) after heat-treated at 800oC for 5h to that of pure α-LiAlO2 matrix (0.57MPa). The porosity of those matrices was not changed significantly after the heat-treatment. The XRD results showed that the crystal structure of α-LiAlO2 did not change during the heat-treatment at 800oC. The wetting behavior and carbonate electrolyte distribution of those pure α-LiAlO2 matrix and heat-treated α-LiAlO2 matrix was investigated. Non-heat-treated and heat-treated α-LiAlO2 matrices were all completely wetted by liquid carbonate electrolyte. Non-heat-treated α-LiAlO2 sample cracked during the melting and wetting process of carbonate electrolyte, however, the heat-treated α-LiAlO2 matrices did not crack due to enhanced mechanical strength.