Abstract
For modern switching power supplies, current bulk magnetic materials, such as ferrites or magnetic metal alloys, cannot provide both low loss and high magnetic saturation to function with both high power density and high efficiency at high frequencies (10-100 MHz). Magnetic nanocomposites comprised of a ferrite and magnetic metal alloy provide the opportunity to achieve these desired magnetic properties, but previously investigated thin-film fabrication techniques have difficulty achieving multi-micrometer film thicknesses which are necessary to provide practical magnetic energy storage and power handling. Here, we present a versatile technique to fabricate thick magnetic nanocomposites via a two-step process, consisting of the electrophoretic deposition of an iron oxide nanoparticle phase into a mold on a substrate, followed by electro-infiltration of a nickel matrix. The deposited films are imaged via scanning electron microscopy and energy dispersive X-ray spectroscopy to identify the presence of iron and nickel, confirming the infiltration of the nickel between the iron oxide nanoparticles. A film thickness of ∼7 μm was measured via stylus profilometry. Further confirmation of successful composite formation is obtained with vibrating sample magnetometry, showing the saturation magnetization value of the composite (473 kA/m) falls between that of the iron oxide nanoparticles (280 kA/m) and the nickel matrix (555 kA/m). These results demonstrate the potential of electrophoretic deposition coupled with electro-infiltration to fabricate magnetic nanocomposite films.
Highlights
As electronic devices continue to be miniaturized there is a corresponding need for smaller on-chip power converters, and it is necessary to ensure that performance does not suffer as the size of the underlying power components decreases.1 Many of the current magnetic materials used for these power components are single phase materials, such as ferrites or magnetic metal alloys.2 At high frequency operation, eddy current losses become significant and higher permeability materials such as magnetic metal alloys result in less efficient components.1,3,4 To retain high magnetic saturation and permeability but incorporate the low loss of ferrites, magnetic nanocomposites show promise for producing materials with these desired magnetic properties
The peaks seen at 2θ = 30.1, 35.4, 53.4, 56.9, and 62.5○ are indicative of a inverse spinel crystal structure, which was expected from this phase of iron oxide
Iron oxide nanoparticles were synthesized via co-precipitation to be used for the low loss magnetic phase for the iron oxide nanoparticle/nickel magnetic nanocomposites
Summary
As electronic devices continue to be miniaturized there is a corresponding need for smaller on-chip power converters, and it is necessary to ensure that performance does not suffer as the size of the underlying power components decreases. Many of the current magnetic materials used for these power components are single phase materials, such as ferrites or magnetic metal alloys. At high frequency operation, eddy current losses become significant and higher permeability materials such as magnetic metal alloys result in less efficient components. To retain high magnetic saturation and permeability but incorporate the low loss of ferrites, magnetic nanocomposites show promise for producing materials with these desired magnetic properties. Electro-infiltration, a process that electroplates a magnetic metal through a porous layer of nanoparticles, has been explored for use in these kinds of applications, but the deposition of the magnetic nanoparticle films have exclusively been accomplished via drop-casting.. By using a low loss magnetic phase (e.g., iron oxide nanoparticles) and a high magnetic saturation phase (e.g., nickel), this work demonstrates the potential of EPD coupled with electro-infiltration for the fabrication of these magnetic nanocomposite films for on-chip power components. This method of coupilng EPD with electroinfiltration presents a versatile tool to fabricate a wide range of nanoparticle-based composites for functional applications
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