Materials Engineering of Soft Magnets for Power and Energy Applications: Ferrites, Soft Magnetic Composites, and Bulk Soft Magnet Materials
Sponsored by: TMS Functional Materials Division, TMS: Energy Conversion and Storage Committee, TMS: Magnetic Materials Committee
Program Organizers: Paul Ohodnicki, National Energy Technology Laboratory; Francis Johnson, GE Global Research; Alex Leary, Carnegie Mellon University; Tanjore Jayaraman, University of Michigan; Lajos Varga, Wigner Research Center for Physics

Wednesday 2:00 PM
March 1, 2017
Room: 25B
Location: San Diego Convention Ctr

Session Chair: Francis Johnson, General Electric

2:00 PM  Invited
Advanced Magnetic Polymer Nanocomposites for High Frequency Device Applications: Hariharan Srikanth1; 1University of South Florida
    Magnetic nanoparticles are being developed for applications ranging from high density recording, spintronic devices to nanomedicine. Surface functionalization and shape anisotropy of nanoparticles are key factors that govern the magnetic response. Dispersion of ferrite nanoparticles into a polymer matrix creates a new class of low-cost, lightweight nanocomposite materials with enhanced and tunable microwave properties for use in high-performance RF and microwave devices, such as integrated high-Q inductors and filters. A challenging issue in polymer nanocomposites is particle agglomeration into non-uniform clusters during the processing stages of thick films. Our research over the years has led to overcoming this limitation through surface functionalization and fabrication of polymer-based superparamagnetic thick films. Microstrip patch antennas have been fabricated loaded with our magneto-dielectric polymer nanocomposites and show excellent performance and higher device miniaturization capability compared to similar structures made with dielectrics alone. Several possibilities in RF device applications witll be discussed.

2:30 PM  
Development of Mold Inductor for Power Conversion System: Hyungsuk Kim1; 1Hyundai Motors
    As regulations on carbon emissions are being strengthened, automakers are focused on developing lightweight and efficient automotive components. An inductor is a component in the power conversion system, which stores and transfers electrical energy and is composed of a magnetic core with electrical wires. While ferrite is a commonly used material for inductors, researching soft magnetic metallic alloy powders is required to make inductors smaller and lighter. In this letter, we present the research on the inductor in a 48/12V converter for 48v mild hybrid vehicles. The developed mold inductor, has embedded electrical wires inside of the inductor filled with a metallic alloy magnetic powder combined with epoxy. When compared with properties of ferrite inductor, the volume of the mold inductor has been reduced by 10% and core loss of the inductor has been decreased. The total efficiency of the 48/12V converter has been increased by 0.5%.

2:50 PM  
Development of Fe-based Bulk Metallic Glasses with Both High Saturation Flux Density and High Glass Forming Ability: Shuangqin Chen1; Kefu Yao1; 1Tsinghua University
    Fe-based soft magnetic metallic glasses have drawn substantial attention due to their high permeability, low coercivity (Hc) and low conductivity which contribute significantly to low core losses. However, inherent low saturation flux density (Bs) and/or low glass forming ability (GFA) of commercial Fe-based soft magnetic metallic glasses has hindered their further applications. In this work, Co was applied to partially replace Fe of Fe-Mo-P-C-B-Si system, then Fe-Co-Mo-P-C-B-Si alloy was obtained with GFA up to 1 mm and Bs better than 1.7 T, which is the highest Bs of Fe-based bulk metallic glasses reported so far. The Hc was also as low as 4.5 A/m. In addition, the 3050 MPa compression strength and better plasticity up to 1.2% also endow the alloys a better service performance. All these make them a promising candidate for commercial applications as magnetic functional and structural materials.

3:10 PM  
Ferrite-coated Fe Soft Magnetic Composites: Balance of Magnetic Permeability and Electrical Resistivity: Katie Jo Sunday1; Mitra Taheri1; 1Drexel University
    Soft magnetic materials are defined by high magnetic saturation and low coercivity; however, for soft magnetic composites, low hysteresis and eddy current losses are significant. Pushing curing temperature limits to properly stress relieve the ferromagnetic powder and maintain the insulating layer is only feasible with inorganic, thermally stable coatings. Soft ferrites allow for complete isolation of individual Fe particles, curing temperatures above 700oC, and minimal reduction in magnetic performance. This work compares three types of ferrites (NiZn-, MnZn-, and Fe-Fe2O4) applied via milling, compacting, and curing between 700 – 1000oC. The coating thickness and uniformity are explored via SEM, while grain structure with respect to temperature are determined via EBSD. Each coating material has different magnetic saturation and resistivity which will control hysteresis and eddy current losses, respectively. This work explores the coating-core interface via TEM/EELS for diffusion of oxygen along the particle boundaries and phase dependence on resistivity.

3:30 PM Break

3:45 PM  Invited
Candidate Coatings for Soft Magnet Composites: Insights Gained from Multiscale Electron Microscopy: Mitra Taheri1; Katie Sunday1; 1Drexel University
    Soft magnetic composites (SMCs) are attractive due to their 3D net-shaped cores and their suitability for electric motor applications. A key feature of SMCs is the thin coating on the base (iron) powder. Traditionally, this coating has been problematic due to non-uniformity, low temperature resistance, and related issues. In this presentation, the development of next-generation coatings for Fe powders is presented. Model coating materials developed in thin film form as well as bulk powder prototypes will be discussed. Magnetic properties as a function of coating-iron interfacial characteristics as determined by multiscale electron microscopy techniques will be reviewed.

4:15 PM  
Study of Temperature Dependent Magnetic Properties of Zr+4 and Ti+4 Substituted Cobalt Ferrites: Monaji Vinitha Reddy1; Sudhindra Rayaprol2; Shara Sowmya3; A. Srinivas3; Dibakar Das1; 1University of Hyderabad; 2UGC-DAE-Consortium for Scientific Research ; 3Defence Metallurgical Research Laboratory
    Substituted cobalt ferrites (CFO) have attracted research attention because of their potential for contactless stress sensing applications. This study demonstrates the variation in magnetic properties of Zr4+ and Ti+4 substituted cobalt ferrites under varying temperatures (5, 150 and 300K) and the results were compared. Polycrystalline Co1+xZrxFe2−2xO4 (CZFO) and Co1+xTixFe2−2xO4 (CTFO) (0 ≤ x ≤ 0.4) samples were prepared by conventional ceramic method. X-ray diffraction (XRD) confirmed the single phase cubic spinel structures, except for x = 0.4 composition. The magnetization (Mmax) and coercivity (Hc) were observed to increase with decrease in temperatures for all CZFO and CTFO samples. The magnetocrystalline anisotropy constant (K1) was increased substantially with decreasing temperatures both for Zr and Ti substituted samples. Maximum differential susceptibility (χ) increased with progressive Zr and Ti substitutions but decreased with increasing temperatures. Curie temperatures of Co1.2Zr0.2Fe1.6O4 and Co1.2Ti0.2Fe1.6O4 samples (~ 729K and 745K respectively) decreased compared to pure CFO (~787K).

4:35 PM  
Consolidation and Behavior of Bulk Iron Nitride Soft Magnets via Spark Plasma Sintering: Baolong Zheng1; Todd Monson2; Yizhang Zhou1; Jean-Pierre Delplanque3; Stanley Atcitty2; Enrique Lavernia1; 1University of California at Irvine; 2Sandia National Laboratories; 3University of California at Davis
    Iron nitrides (FexN) have magnetic moments well in excess of those achievable with currently available soft magnetic materials. There are, however, few reports involving the fabrication of dense FexN using powder, partly because of the relatively elevated sintering temperatures required which can lead to decomposition of FexN. In present study, fully dense bulk FexN was synthesized for the first time ever using spark plasma sintering (SPS) of FexN powders. The microstructure of consolidated bulk FexN was characterized with XRD, SEM, and TEM, and their magnetic properties were measured and will be discussed. The X-ray diffraction studies revealed a mixed phase composition. Finite element method (FEM) was also applied to investigate and explain localized heating and temperature distribution during SPS. The effects of processing on interface bonding formation and phase evolution were investigated and discussed in detail to provide insight into fundamental phenomena and microstructural evolution in SPSed FexN.

4:55 PM  
Consolidation of Bulk Ferrimagnetic Rare Earth Iron Garnets: Chad Warren1; Pathikumar Sellappan1; Yasuhiro Kodera2; Javier Garay1; 1University of California, San Diego; 2University of California, Riverside
    Rare earth (RE) iron garnets are a well-studied technologically important class of materials that exhibit tunable magneto-optic effects and high frequency properties. These materials are also ferrimagnetic, electrically insulating and stable across large temperature ranges, making them ideal candidates for spintronics based research. Despite the amount of literature available on RE iron garnets, the effects of microstructure on the electromagnetic properties are not well described, especially for the case of nano-sized grains. To this end, we present work on the synthesis and processing of rare earth iron garnets containing one or more rare earth elements. By first synthesizing the garnets through a chemical route, we first produce very fine, high purity powder with specific stoichiometries. We then use current-activated, pressure-assisted densification (CAPAD) to produce dense sample with highly controllable microstructure. Magnetic and structural characterization is performed to elucidate the effect of grain size on the properties.