Materials vs Minerals: Bridging the Gap between Materials Science and Earth and Planetary Science: On-Demand Oral Presentations
Sponsored by: ACerS
Program Organizers: Jessica Rimsza, Sandia National Laboratories; Krishna Muralidharan, The University of Arizona ; Thomas, The University of Arizona
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 7
Location: MS&T On Demand
Coupling Aberration Corrected STEM and DFT to Determine the Crystal Chemistry of Hibonite for Application to Early Solar System Thermodynamics: Pierre-marie Zanetta1; Venkat Manga2; Yao-Jen chang2; Tarunika Ramprasad3; Thomas Zega2; 1University of Arizona; 2Lunar and Planetary Laboratory, The University of Arizona; 3The University of Arizona
Hibonite, CaAl12O19, occurs in refractory inclusions of primitive chondritic meteorites. It is thermodynamically predicted to form at high temperature in the solar nebula gas. Hibonite can host significant amounts of 3d transition metals. In particular, Ti can substitute in multiple oxidation states, reflecting the thermodynamic conditions (temperature, oxygen fugacity; fO2) under which a hibonite grain formed or last equilibrated. Here we describe a study combining electron energy-loss spectroscopy (EELS) in an aberration-corrected scanning transmission electron microscope with first-principles density-functional theory (DFT). The aim is to determine the crystal chemistry as well as the Ti oxidation state and to computationally develop a model to relate Ti4+/ΣTi to the fO2. EELS data show that Ti mostly resides on Al4 sites and that atomic columns contain both Ti4+ and Ti3+. The Ti4+/ΣTi ratio varies over hundreds of nanometers, suggesting that the grain recorded local changes in the redox conditions when it last equilibrated.
Investigation of Variable Manganese and Nickel Content on Ductile Iron Castings Utilizing Ionic Liquids Isolated Iron and Bosch Carbon: Blake Stewart1; Haley Doude1; Jennifer Edmunson2; Eric Fox2; Morgan Abney3; Paul Hintze2; Jeffrey Mehan2; Hongjoo Rhee1; 1Mississippi State University; 2Marshall Space Flight Center; 3Langley Research Center
As research continues for missions beyond low-Earth orbit, in-situ resource utilization (ISRU) methods are critical. For Lunar and Martian colonization, the ability to manufacture mechanical and structural components with local resources is essential. Ionic liquids (IL) are being studied at NASA Marshall Space Flight Center to harvest elemental metals from meteorites and regolith oxides. In this investigation, the effect of nickel and manganese additions in casting ductile iron using IL sourced iron (IL DI) was explored given ductile iron’s range of applications and performance as an as-cast alloy. Ingots were produced using commercial elements to simulate the use of IL iron with carbon from the by-products of the Bosch process, a life support system currently tested at MSFC. Samples were evaluated using phase transformations, microstructures, and hardness. Results showed the addition of nickel and manganese to IL DI is a viable means to produce a range of IL DI alloys.
Modeling Thermodynamics of Condensation of Fe-Ti-bearing Byroxenes Relevant to the Early Solar System: Venkateswara Manga1; Thomas Zega1; 1Lunar and Planetary Laboratory/University of Arizona
Pyroxene, Ca(Mg,Ti,Fe)(Al,Si)2O6, is an important mineral group. In primitive meteorites it occurs as a constituent of major petrographic components such as chondrules and calcium-and-aluminum-rich inclusions, the latter which are reported to be the first solids to have condensed in our early solar system. Knowledge of pyroxene thermodynamics is therefore important to understanding the conditions (e.g. T and P) under which such phases condensed in the high-temperature region of the solar nebula. To this end we report first-principles driven thermodynamic modeling of the pyroxene within the CALPHAD framework. The enthalpies and entropies of mixing of the solid solutions at different compositions are calculated from first-principles calculations of special-quasirandom-structures. The condensation temperatures of the solution phase at different pressures of the nebular gas and the temperature-dependent evolution of its crystal chemistry are predicted. We will discuss the implications of the model predictions to the microstructural analysis of CAIs and their thermodynamic origins.
Chemical Pathways for Formation of Carbon Nanostructures from Graphite: Implications for Circumstellar and Solar-system Carbon: Abhishek Thakur1; Krishna Muralidharan1; Thomas Zega1; Lucy Ziurys1; 1University of Arizona
Using classical and ab-initio molecular dynamics, we investigate the effects of thermal and mechanical-shock stimuli on graphite. Specifically, for graphite, thermal effects lead to curling of edges of the individual sheets, ultimately leading to the formation of tubular structures at sheet edges. Further, depending on thickness of the graphitic system, we see the formation of both single wall and multiwall tubular structures, which then rearrange to form configurations that resemble single wall and multiwall carbon-nanotubes. The impact of mechanical shock stimulus is similar to thermal effects in terms of formation of tubular structures; however, we also see ejection of carbon fragments. Finally, using unsupervised machine learning, we analyze the trajectories of MD simulations and estimate the activation barriers and kinetics of formation of nanotubes and spherical fullerene molecules. This work has fundamental implications for analyzing meteoritic and planetary materials as well as for interpretation of currently unidentified diffuse interstellar bands.