Lifetime of Sodium Beta-Alumina Membranes in Molten Sodium Hydroxide
Final rept. 1 Apr 2007-1 Apr 2008
ICELAND UNIV REYKJAVIK TECHNOLOGICAL INST OF ICELAND
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Sodium metal can be made by electrolysis of molten sodium hydroxide in sodium Beta-alumina membrane electrolysis cells. However, there are some uncertainties about the lifetime of the sodium Beta-alumina membranes in contact with molten sodium hydroxide. The main objective of this project is to address these uncertainties and to study if the properties of the membrane degrade upon long term contact with molten sodium hydroxide. Electrolysis cells were designed, but it proved impossible to test them because the potentiostat that was to be used was designed for low current density. It therefore turned out to be impossible to do electrolysis tests with this experimental set-up. Instead, samples of sodium Beta-alumina disk were aged in molten sodium hydroxide for up to 149 day. Mass loss was only 0,15 in the first 108 days, but in the next 41 days mass loss accelerated considerably, or up to 0,33 in 41 days. No change in the phase composition of the material was observed in the 149 days. Investigation of aged samples with SEM Scanning electron microscopy revealed that the molten sodium hydroxide preferably dissolved material at grain boundaries, which most likely resulted in freeing of grains 1 - 3 microns diameter from the bulk of the material.
- Inorganic Chemistry
- Electrical and Electronic Equipment
- Electrochemical Energy Storage