Simultaneous Quantification of Hydride Ions and Electrons Incorporated in 12CaO·7Al2O3 Cages by Deuterium-Labeled Volumetric Analysis

Abstract

An extended volumetric method, combined with quadrupole mass spectroscopy (QMS), is proposed. This method enables us to distinguish and simultaneously quantify hydride (H–) ions and electrons (e–) incorporated in cages of 12CaO·7Al2O3 (C12A7), which is accomplished upon annealing with CaH2. When a sample is dissolved in a deuterium chloride solution, most of the H– ions and electrons released from cages react to form HD and D2 molecules, respectively. These isotope-labeled molecules are then detected by QMS. We have used this method to follow the concentrations of H– ions and electrons in C12A7-treated CaH2 over the thermal treatment time. We found that during the initial seven days of treatment, both concentrations increased. Thereafter, the electron concentration begins to decrease, while the H– ion concentration continues to increase toward the theoretical maximum. This diverging behavior is due to differences in their diffusion ratios and thermodynamic stabilities.