SUBJECT: Ph.D. Dissertation Defense
BY: Robert Gill
TIME: Tuesday, August 17, 2021, 2:00 p.m.
PLACE:, Online
TITLE: Determination of the Rate Limiting Mechanism(s) for the Thermal Reduction of Reduction/Oxidation-Active Mixed Ionic-Electronic Conducing Materials
COMMITTEE: Dr. Peter Loutzenhiser, Chair (ME)
Dr. Sheldon Jeter (ME)
Dr. Matthew McDowell (ME/MSE)
Dr. Nazanin Bassiri-Gharb (ME)
Dr. Jye-Chyi Lu (ISyE)


Many solar power towers utilize a fluidized media to store absorbed energy for later use. Currently, molten salts and metals are used as storage mechanisms, but their temperature limitations adversely impact the efficiency of solar power plants. Perovskite oxides can be used to overcome the temperature limitations as well as add a chemical energy storage component due to their mixed ionic-electronic conducting (MIEC) properties. After thermodynamic metrics are characterized, the on-sun performance of perovskite oxides need to be examined in order to design full-scale reactors and storage systems. The chemical kinetics of the thermal reduction of Ca(Al,Ti)0.2Mn0.8O3-δ (CAM28) and CaTi0.2Mn0.8O3-δ (CTM28) were investigated in an upward flow reactor coupled to a high-flux solar simulator for ultra-fast heating rates. A heat and mass transfer model was used to determine spatial and temporal temperatures profiles, and O2 evolution measured by a combination of mass spectrometry and gas chromatography was coupled to the modeling to determine appropriate kinetic rate law. First-order apparent kinetics to the reduction reaction accurately captured the thermal reductions of both CAM28 and CTM28 . Apparent pre-exponential factors for CAM28 and CTM28 of 1.00 ± 0.46 s-1 and 0.86 ± 0.39 s-1 respectively, were determined with corresponding apparent activation energies of 49.1 ± 9.6 kJ/mol and 28.4 ± 6.5 kJ/mol respectively. The results will help guide future reaction design and lay a foundation for other perovskite oxides to be tested.