Desorption of H2O and H2 from steel and LiAlO2 by temperature programmed desorption

Temperature programmed desorption (TPD) measurements with a steel sample tube and helium sweep gas are in progress to provide data describing the kinetics of desorption of H2O(g) and H2(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H2O being consumed and H2 being evolved. There is also evidence of some dissolution of H2 in the steel. However, it is possible to stabilize the steel in the absence of added H2 so that useful desorption measurements with H2O(g) can be made. Initial work was on the LiAlO2-H2O(g) system. Fresh samples of LiAlO2 bear large amounts of adsorbed H2O. TPD spectra were measured for LiAlO2 that had been equilibrated in a helium stream with 200 ppm H2O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied, questions of possible peak overlap still remain to be resolved. An activation energy for desorption of H2O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. This result agrees with the value reported in the literature for decomposition of LiOH, and suggests that some sites on LiAlO2 might resemble sites on Li2O in their adsorptive properties. For a 773 K equilibration, the activation energy of desorption appears considerably higher.