(480c) Corrosion Performance of Ceramic Materials in High Temperature Sulfuric Acid Environments

The Sulfur-Iodide (SI) process has been investigated extensively as an alternate process to generate hydrogen through the thermo-chemical decomposition of water. The commercial viability of this process hinges on the durability and efficiency of heat exchangers/decomposers that operate at high temperatures under corrosive environments. In cooperation with the DOE and the University of Nevada, Las Vegas (UNLV), ceramic based micro-channel decomposer concepts are being developed and tested. The performance benefits of a high temperature, micro-channel heat exchanger are realized from the thermal efficiency due to improved effectiveness of micro-channel heat and mass transfer and the corrosion resistance of the ceramic materials. The success of these high temperature processes is dependent on the corrosion properties for the materials of construction. Super-alloys are often considered because of their ability to be manufactured into heat exchangers and reactors by traditional fabrication methods. The creep and oxidation properties of these metals remain problematic due to these extreme temperatures (900C) and corrosive environments. However, ceramic materials have been noted for their excellent corrosion resistance. In order to assess the viability of ceramic materials, extended high temperature exposure tests have been made to characterize the degradation of the mechanical strength and estimate the recession rates due to corrosion. These results indicate that the strength and recession rates for these ceramic materials were excellent, enabling the development and demonstration of the SI process for hydrogen generation. The results of these corrosion studies will be presented with additional analysis including surface and depth profiling was done using high resolution electron microscopy. These discussions will also compare the expected life and possible failure mechanisms of the candidate materials.