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Magnets Jeffrey E. Shield, University of Nebraska-Lincoln, DMR 0804744 Many modern technologies such as consumer electronics and hybrid/electric vehicles require the use of high-energy permanent magnets. Higher energy densities can be achieved by assembling two different kinds of magnetic materials at the nanoscale, as short-range interactions (“exchange coupling”) result in superior magnetic properties. One way to promote nanostructuring is through alloying. However, the nanostructure that develops during solidification depends on the alloying addition. We are investigating the microstructural selection with different alloying additions. In some cases, we retain a fibrous nanocomposite (“eutectic structure”), while in others we obtain primary formation The addition of aluminum does not inhibit eutectic growth but does refine the scale by about 1/3. This scanning electron micrograph showing the eutectic structure of rods of one phase in a matrix of another. However, the addition of Molybdenum ruins the eutectic structure and results in a coarse “dendritic” (tree-like_ 1 mm 100 mm
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Novel Nanostructures for High-Energy Permanent Magnets Jeffrey E. Shield, University of Nebraska-Lincoln, DMR 0804744. - PowerPoint PPT Presentation
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Novel Nanostructures for High-Energy Permanent Magnets
Jeffrey E. Shield, University of Nebraska-Lincoln, DMR 0804744
Many modern technologies such as consumer electronics and hybrid/electric vehicles require the use of high-energy permanent magnets. Higher energy densities can be achieved by assembling two different kinds of magnetic materials at the nanoscale, as short-range interactions (“exchange coupling”) result in superior magnetic properties. One way to promote nanostructuring is through alloying. However, the nanostructure that develops during solidification depends on the alloying addition. We are investigating the microstructural selection with different alloying additions. In some cases, we retain a fibrous nanocomposite (“eutectic structure”), while in others we obtain primary formation of cobalt that results in coarse structures and poor exchange coupling. Through this, we are understanding solidification behavior in these alloys in order to produce improved permanent magnets.
The addition of aluminum does not inhibit eutectic growth but does refine the scale by about 1/3. This scanning electron micrograph showing the eutectic structure of rods of one phase in a matrix of another.
However, the addition of Molybdenum ruins the eutectic structure and results in a coarse “dendritic” (tree-like_ structure.
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This grant has supported M.S. students Wendy Keeler and Brian Dick and current Ph.D. student Hellen Jiang, as well as visiting scientist Dr. Shampa Aich from IIT-Kharagpur. REU and RET supplements support undergraduate student Miranda Barr and high school science teacher Pam Rasmussen. REU Site participant Joy Chao also worked on the processing/structure relationships in rare earth permanent magnets. She is pictured by the poster she presented at the summer Research Symposium, and with Ph.D. student Hellen Jiang.
Summer researcher Joy Chao from the University of Illinois by her poster at the Research Symposium
Ph.D. Student Hellen Jiang (right) with summer researcher Joy Chao
Novel Nanostructures for High-Energy Permanent Magnets
Jeffrey E. Shield, University of Nebraska-Lincoln, DMR 0804744
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