Thermodynamics of Materials in Extreme Environments: Thermodynamics and Stability of Mateirals for Fuel Cells and Other Energy Applications
Sponsored by: ACerS Basic Science Division, ACerS Energy Materials and Systems
Program Organizers: Xiaofeng Guo, Washington State University; Kristina Lilova, Arizona State University; Kyle Brinkman, Clemson University; Alexandra Navrotsky, Arizona State University; Jake Amoroso, Savannah River National Laboratory; Xingbo Liu, West Virginia University; Gustavo Costa, NASA Glenn Research Center
Wednesday 2:00 PM
November 4, 2020
Room: Virtual Meeting Room 29
Location: MS&T Virtual
Session Chair: Xingbo Liu, West Virginia University
2:00 PM Invited
Helium Irradiation of Gd2Zr2O7 Defect-fluorite Ceramics: Interfacial Phenomena and Radiation Resistance: Zhangyi Huang1; Jianqi Qi1; Xiaofeng Guo2; Tiecheng Lu1; Di Wu2; 1Sichuan University; 2Washington State University
Gd2Zr2O7 ceramics with different grain sizes from nanoscale to submicron scale (55 – 634 nm) were synthesized and irradiated at room temperature under helium ions (190 keV) with dose up to 5 × 1017 ions/cm2. The pre- and post-irradiation samples were carefully studied using GIXRD, SEM, HRTEM and AFM as the grain size and degree of irradiation vary, in which amorphization, cell volume expansion, helium bubble formation, lattice distortion and surface blistering phenomena were interpreted and discussed. The results suggest grain boundary plays a critical role in minimizing the structural and morphological defects and inhibiting the multi–stage He bubble formation. Moreover, thenanograin samples have better radiation resistance and are more stable compared with submicron Gd2Zr2O7.
2:30 PM
Density Functional Theory Modeling on the Positive Effect of H2O in Hydrogen Oxidation Reaction on Perovskite Anode for Solid-oxide Fuel Cells: Yueh-Lin Lee1; Qi He2; Tao Yang1; Wenyuan Li2; Wei Li2; Liang Ma2; Shanshan Hu2; Yuhua Duan3; Xingbo Liu2; Gregory Hackett3; 1Leidos Research Support Team at National Energy Technology Laboratory; 2West Virginia University; 3National Energy Technology Laboratory
The electrochemical performances of the perovskite Sr2Fe1.5Mo0.5O6-δ (SF1.5M) in dry and humidified H2 are investigated by DFT based thermodynamic modeling, electrical conductivity relaxation (ECR), and electrochemical impedance spectroscopy (EIS) techniques. Both the ECR and EIS measurements indicated promoted electrochemical performances of SF1.5M in humidified H2. The DFT based modeling revealed the nonstoichiometry of SF1.5 (001) BO2 slab models significantly alters the HOR energy landscape and reduces the energy of the plateau intermediate state – the step of H2O plus surface oxygen vacancy formation, which couples with increment of the oxygen chemical potential and decrement of the free electron concentration upon increasing humidity. Furthermore, comparing HOR on the dry surface and on the hydrated surface, the H2O plus surface oxygen vacancy formation energies are lower in the latter case. These factors responsible for the positive effect of humidity on the enhanced HOR activities will be discussed for the perovskite-based SOFC anode materials.
2:50 PM
Molecular Modeling of Surface Exchange Mechanisms in Solid Oxide Fuel Cell Cathodes: Dane Morgan1; Yipeng Cao1; 1University of Wisconsin-Madison
Solid Oxide Fuel Cell (SOFC) cathodes in use today generally use perovskite oxides to efficiently catalyze the oxygen reduction reaction, O2(gas) +2e- → 2O2- (solid). For many of the most active materials this process is strongly correlated to the surface exchange coefficient, k*, which measures how easily oxygen enters and leaves the material. In this talk we discuss our work using atomistic simulations to model the steps in the oxygen reduction reaction on ABO3 perovskite surfaces. We focus on (001) surfaces of (La,Sr)CoO3 and (La,Sr)MnO3, two widely studied SOFC cathode materials. We primarily find that the step of O adatoms finding surface vacancies is rate limiting, and find large differences between AO and BO2 surfaces in (La,Sr)CoO3 but not (La,Sr)MnO3. These results provide a foundation for interpreting experiments and guiding materials design of highly active and stable cathodes.
3:10 PM
Ellingham Diagram to Assess Synthesis Conditions and Chemical Stability of Ceramic Membranes under Operational Conditions: Armin Feldhoff1; 1Leibniz University Hannover
An Ellingham diagram is useful to both synthesis and application of ceramic membrane material. Dense ceramic oxygen-transporting membranes rely on mixed ionic-electronic conductors (MIECs), which are complex oxides with an oxygen non-stoichiometry. Often these oxides have more than three different cations incorporated. Alkaline-earth metals among the cations make the ceramic membrane potentially vulnerable to the formation of oxygen impermeable carbonate scales on its surface, if the membrane is operated in CO2-containing atmosphere. Here it is shown that an Ellingham diagram, which includes not only the temperature-dependent equilibrium carbon dioxide chemical potential over a mixture of a metal’s carbonate and its oxide, but also of the surrounding atmosphere, allows identify save operational conditions for a given MIEC. Moreover, the Ellingham diagram allows identify cations to build a MIEC for specific operational conditions. For synthesis of MIECs, minimum applicable calcination temperature, to decompose carbonate intermediates, can be read from the Ellingham diagram.
3:30 PM
Thermodynamics and Elastic Properties of Cerium Doped Yttrium Aluminum Garnets: Vitaliy Goncharov1; Nian Wei2; Miu Lau3; Albert Migliori4; Hongwu Xu4; Min Long3; Xiaofeng Guo1; 1Washington State University; 2Sichuan University; 3Boise State University; 4Los Alamos National Laboratory
Cerium doped yttrium aluminum garnet (Y3-xCexAl5O12, Ce:YAG) is a promising yellow-light emitting component of solid state white-light emitting diode. In this work, we investigate the effects of Ce doping on the elastic properties of Ce:YAG. Resonant ultrasound spectroscopy (RUS) was employed to determine the elastic constants of Ce:YAG at x = 0.025, 0.1 and 1 at. %. Through the calculation of elastic moduli and utilization of the Mie-Grüneisen EOS approach Cp at room temperature was successfully obtained for Ce:YAG. Debye Temperature (𝜃𝐷) was determined with RUS measured sound velocities and was in excellent agreement to values obtained from neutron scattering and theoretical methods. Lastly, RUS application and reliability towards extrapolation of further thermodynamic parameters is discussed.