MATERIALS SCIENCE AND ENGINEERING

DMSE Colloquia, Fall 2009

Tuesday, October 06, 2009 | 10:00 AM | 411 White Building

Advanced Inductor Materials for Naval Compact Power Applications

Matthew A. Willard

Multifunctional Materials Branch
U. S. Naval Research Laboratory
Washington, D.C.
U.S.A.

Abstract:

The synthesis and characterization of soft magnetic materials with nanocrystalline microstructures has been an intense field of research in recent years. In an effort to improve their soft magnetic performance by controlling the microstructure, novel techniques and alloying element combinations have been used. The resulting materials show unique combinations of magnetic properties that are possible only when the magnetic exchange correlation length (~(A/K₁)^1/2)and structural correlation length (grain size) are similar. Nanocrystalline soft magnetic alloys were first developed in 1988 when Yoshizawa, et al. added small amounts of Nb and Cu simultaneously to a typical Fe-Si-B amorphous alloy. The improved magnetic properties of nanocrystalline alloys, including large relative permeability (above 100,000) and saturation magnetization (1.3 T), stem from their combination of refined grain size, intergranular amorphous matrix phase, and the composition of each phase. In this seminar, I will discuss the influence of composition, kinetics, and microstructure on the magnetic properties of (Fe,Co,Ni)-Zr-B-Cu alloys. Differential thermal analysis, thermomagnetic analysis, x-ray diffraction, and transmission electron microscopy will be used to describe the phase transformations and the resulting processing/structure/property relationships.

Speaker Biography:

Matthew Willard received his Ph.D. in Materials Science and Engineering from Carnegie Mellon University in 2000. His dissertation entitled, “Structural and Magnetic Characterization of HITPERM Soft Magnetic Materials for High Temperature Applications” provided a broad characterization of the first (Fe,Co)-based nanocrystalline soft magnetic alloy. For this work, he was the recipient of the Graduate Student Gold Metal Award in the in the spring of 1999, the Materials Research Society’s highest graduate student honor. After graduation, Dr. Willard received a National Research Council Associateship sponsored by the director of the Naval Research Laboratory in Washington, DC, where he continued to work on nanocrystalline soft magnetic materials. In 2003, Dr. Willard accepted a position as a research scientist at the Naval Research Laboratory (NRL) where he is currently principal investigator for a magnetic materials research group. His duties in this capacity include planning and conducting research, while managing a small group of contractors, postdocs, and students. He has been productive in the field of nanocrystalline soft magnetic alloys, with 30 publications in this field. This work has garnered international interest in his research. Dr. Willard was the Acting Section Head of the Microstructural Evolution Section at NRL during the spring of 2007. Previously, he has conducted research at Ames National Laboratory, Brookhaven National Laboratory, and Los Alamos National Laboratory.

Coffee and doughnuts will be served from 9:30 AM.

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