Laboratory Synthesis of Tetrataenite Aimee Goncalves University of Massachusetts Amherst Department of Mechanical and Industrial Engineering
Motivation Tetrataenite Diffusion Enhancement
Cold Rolling Diagram A global scarcity of rare-earth metals has provided a need for new • Tetrataenite is a meteoritic mineral with the ideal formula of • Phosphorus addition magnetic materials to synthesize powerful, cost efficient, rare-earth • small amounts proven to accelerate 1 FeNi with the L10 structure, which forms by chemical ordering of diffusion process5 metal-free magnets . It is known that tetrataenite, a structure formed 2,4 from iron (Fe) and nickel (Ni) atoms (50%-50%) found in iron meteorites, Fe and Ni atoms in taenite . • different weight percent (wt %) P samples • The formation of tetrataenite takes millions of years due to: used in this study: has the desired strong magnetic properties due to the L10 ordering of • a low ordering temperature (320oC)2 • higher and medium wt % samples were the atoms. However, the FeNi system has a very slow diffusion rate. provided by General Motors (GM) 2,3 Tetrataenite Rim • the slow rate of diffusion of iron and nickel atoms • lower wt % sample synthesized at UMass Extraterrestrial Materials Laboratory Cloudy Zone Iron-Nickel Phase Diagram 5 Kamacite • Metal Working Heat Treatment of Samples 6 Transformation of FCC into L10 • induce defects in the material which Homogenize in high temp. Tetrataenite are beneficial for diffusion furnace 500 μm 100 μm • Heat Treatment (HT) Recrystallization above ordering Hold below temperature ordering Optical Microscopy Images of Estherville Meteorite • HT 1: formation of small grains by temperature for Purpose recrystallization long time • diffusion is enhanced on grain HT 1 HT 2 The goal of this research is to observe on a lab scale the effects of Taenite Tetrataenite boundaries due to their high energy6 Face-Centered Cubic (FCC) L1 phosphorus addition and cold rolling on the diffusion rate of FeNi to 0 • HT 2: held for several days to order form tetrataenite. the L10 crystal structure
Laboratory Process Results and Discussion Conclusions Cold Rolled Low Temp As Cast Homogenized • During homogenization, phosphorus was not Heat Treatment High Temp • homogenization of samples medium P content sample completely absorbed into the high P content sample Furnace Furnace • to ensure even distribution of 500 μm Phosphide Deformation while all phosphorus went into the matrix in the elements Bands • electron probe to verify medium and low P content samples. Phosphide homogenization • Heat Treatment 1 failed to form recrystallized • cold rolled and heat treat structure. A higher temperature heat treatment samples suggested. • metallurgical sample preparation high P content sample 1.0 mm Future Work Bucket of water between each step of treatment 5 μm 5 μm for quenching 500 μm Phosphide • Further high resolution SEM study to compare small samples • optical and SEM microscopy to phosphide precipitates after final heat treatment. observe changes in structure Deformation bands formed along rolling direction (left) Phosphide elongated along rolling direction forming cracks (right) • Electron diffraction study: transmission electron microscopy (TEM) to verify L10 formation in the Electron Probe Results Heat Treatment 1 Heat Treatment 2 synthesized materials. of the matrix medium P content sample 1.0 mm medium P content sample medium P content sample • Redo process using a higher recrystallization average standard average standard temperature during heat treatment. wt % Ni deviation wt % P deviation Phosphide 500 μm References wt % Ni wt % P Phosphide (1) Lewis, Laura H, and Felix Jimenez-Villacorta. “Perspective on Permanent Magnetic Materials FNP001 as cast 49.779 0.7676 1.172 2.8025 for Energy Conversion and Power Generation.” Metallurgical and Materials Transactions A, v. 44A FNP001 H 49.679 0.1329 0.636 0.0194 (2012). Print. (2) Clarke, Roy S. Jr, and Edward R. D. Scott. “Tetrataenite – ordered FeNi, a new mineral in meteorites.” American Mineralogist, v. 65 (1980): 624-30. Print. (3) “2012 Student FNP003 as cast 50.321 0.3674 0.257 0.3321 Summaries & Posters: Frank May.” The College of Engineering at UMass Amherst. N.p., n.d. Web. 2 FNP003 H 49.884 0.3798 0.263 0.0211 July 2013
Acknowledgements This project is funded by grants from the Massachusetts Space Grant Consortium ARPA-E REACT. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect those of NASA or the Massachusetts Space Grant Consortium. A special thanks to Dr. Arif Mubarok and Dr. Joseph Goldstein for guidance and support during this opportunity.