Thermodynamics of Materials in Extreme Environments: Thermodynamics at the Nanoscale and Interfaces
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
Thursday 8:00 AM
November 5, 2020
Room: Virtual Meeting Room 29
Location: MS&T Virtual
Session Chair: Kristina Lilova, Arizona State University
8:00 AM Invited
Ab-initio Studies of Point Defects in Alumina under Electrochemical Conditions: Aditya Sundar1; Liang Qi1; 1University of Michigan
The anti-corrosion performance of passive oxides, such as Al2O3, highly depends on the thermodynamics and kinetics of point defects in the bulk and on surfaces of these oxides under electrochemical conditions. Here I would like to present two examples of ab-initio studies of these point defects. First, we combined empirical interatomic potential and density functional theory (DFT) calculations to search the accurate structures and energetics of point defects in bulk α-Al2O3. It suggests that, at the electrochemical conditions where liquid water is thermodynamically stable, the point defect formation reactions in the crystalline α-Al2O3 can be exothermic. It naturally explains the amorphous structures of alumina at the Al/water interfaces. Second, we studied the stability of point defects at the interface between alumina and electrolyte that contains chlorine under different local chemical and structural conditions, which can be helpful for the design of passive oxide layers with high resistance to localized corrosions.
8:30 AM
Nanomaterials from Geopolymer, a Low-temperature Ceramics: Dong-Kyun Seo1; 1Arizona State University
Aluminosilicate geopolymer is a low-temperature ceramics with an immense potential in sustainability applications. Recent innovations in geopolymer synthesis have enabled previously unforeseen levels of control over the nanoscopic morphologies and porosity and have demonstrated that the resulting nanomaterials can show performances far superior to other classes of materials. This talk will illustrate some of these advances with examples relevant to sustainability applications. For example, nanoporous geopolymer materials could be produced and used as an excellent arsenic absorbent for ground water purification and as a highly effective biodiesel catalyst. High-structure geopolymer nanoaggregates can be synthesized with controlled zeolicity for polymer nanocomposite applications with excellent energy-saving performances. Highly-crystalline hierarchical zeolites have been discovered to show an exceptional CO2 capacity, sorption kinetics, selectivity and regeneration capability essential for cost-effective CO2 separation. Superior ion exchange kinetics of the material has been observed for silver-ion zeolite with a superb antibacterial efficacy against antibiotics-resistant MRSA bacteria.
8:50 AM
Pressure-induced Anomalous Phase Transition Behavior in Layered Tellurene: Arunima Singh1; Han Li1; Kedi Wu1; Sijie Yang1; Tara Boland1; Bin Chen1; Sefaattin Tongay1; 1Arizona State University
Recent studies have demonstrated that tellurene is a van der Waals two-dimensional material with potential optoelectronic and thermoelectric applications as a result of its pseudo-one-dimensional structure. Using density-functional theory simulations and experimental characterization of high quality single crystalline Te nanoribbons we find that Te undergoes a pressure-dependent phase transition with a large pressure hysteresis and with multiple competing phases [1]. During compression, a phase transition from the trigonal to the orthorhombic phase occurs at 6.5 GPa and is sudden. In contrast, a gradual phase transition occurs during decompression, where its orthorhombic and trigonal phases co-exist between 6.9 to 3.4 GPa. Grüneisen parameter calculations further confirm the presence of co-existing phases and suggest hysteretic phase change behavior. [1] Nanoscale 11, no. 42 (2019): 20245-20251.
9:10 AM
Stabilities and Ultrafast Dynamics of Sub-nanometer Metal Oxide Clusters: Scott Sayres1; 1Arizona State University
Research on isolated clusters in the gas-phase, serving as model systems to mimic the active sites of bulk surfaces, has provided a wealth of information on fundamental photochemical reaction dynamics. Here, I will present our recent experimental results showing the ultracold distributions of neutral TinOm, FenOm, and NinOm oxide clusters (where n < 10) as produced through the extreme conditions provided by gas-phase supersonic expansion. Research on this sub-nanometer size regime enables insights into the energy transfer, relaxation dynamics, and thermodynamic stability for a whole range of materials that differ from standard bulk stoichiometries and change with the addition or subtraction of a single atom. Specifically, I will show our ultrafast pump-probe spectroscopy measurements on the direct ionization, dissociation, and energy transfer dynamics for these cluster systems, and highlight how both the cluster size and oxidation state play important roles in driving photocatalytic performance.