AC complex impedance spectroscopy studies were conducted on symmetrical cells of the type [gas, electrode/LSGM electrolyte/electrode, gas]. The electrode materials were slurry-coated on both sides of the LSGM electrolyte support. The electrodes selected for this investigation are candidate materials for SOFC electrodes. Cathode materials include La{sub 1-x}Sr{sub x}MnO{sub 3} (LSM), LSCF (La{sub 1-x}Sr{sub x}Co{sub y}Fe{sub 1-y}O{sub 3}), a two-phase particulate composite consisting of LSM + doped-lanthanum gallate (LSGM), and LSCF + LSGM. Pt metal electrodes were also used for the purpose of comparison. Anode material investigated was the Ni + GDC composite. The study revealed important details pertaining to the charge-transfer reactions that occur in such electrodes. The information obtained can be used to design electrodes for intermediate temperature SOFCs based on LSGM electrolyte.

Colloids have the potential to transport strongly sorbing radionuclide contaminants in soils and groundwater aquifers. Recent studies from the Nevada Test Site have indicated the enhanced mobility plutonium, albeit in minute quantities, associated with various silicate minerals (Kersting et al., 1999); however, significant colloidal transport of thorium (Th) and rare earths (RE) in nature, considered to be chemical analogs for plutonium, is rare. Yet, the current Yucca Mountain model for colloids would have predicted extensive Th- and RE migration, given these phases' association with clay minerals. Several studies have pointed to the effect of water flow rate on colloid and particulate migration. In this paper, we examine the benefit of relating water flow rate and the wasteform alteration structure to colloid release.