Amtec power output optimization by investigating the grain size effect on its electrode materials

The Alkali Metal Thermal-to-Electric Converter (AMTEC) is perhaps one of the most desirable devices for directly converting heat into electrical energy, particularly for space applications. There has been a lot of research in the past for improving this device. Since AMTEC has been intended for deep space use its stability is expected to last a long time, 15 years or more. The two major components responsible for power output of AMTEC are the electrolyte and the electrode. In this work we focus research on the AMTEC electrodes, which could be improved further to reduce the power degradation as the time goes by in using the AMTEC.

This study aims at improving the performance of the electrode by looking into the changes of the material properties inherent to it with respect to time. These parameters refer to the grain growth involved in the grain mobility model for electrode materials. If the grain size of the electrode material reaches a certain dimension, about 750 nm, the power output starts degrading fast. This is very important because this condition should not occur until after 15 years and corresponds to a power degradation percentage of 10 % for different electrode materials. The electrode materials studied in this work are Mo, TiN, RhW, and . It was found that adjusting four different paramters for these electrode materials gave a power degradation between 3 % to 22 %.