Publications

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Significant reductions recently seen in the size of wide-bandgap power electronics have not been accompanied by a relative decrease in the size of the corresponding magnetic components. To achieve this, a new generation of materials with high magnetic saturation and permeability are needed. Here, we develop gram-scale syntheses of superparamagnetic Fe/FexOy core-shell nanoparticles and incorporate them as the magnetic component in a strongly magnetic nanocomposite. Nanocomposites are typically formed by the organization of nanoparticles within a polymeric matrix. However, this approach can lead to high organic fractions and phase separation; reducing the performance of the resulting material. Here, we form aminated nanoparticles that are then cross-linked using epoxy chemistry. The result is a magnetic nanoparticle component that is covalently linked and well separated. By using this 'matrix-free' approach, we can substantially increase the magnetic nanoparticle fraction, while still maintaining good separation, leading to a superparamagnetic nanocomposite with strong magnetic properties.

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Measure the total quantity of tritium in the sample by heating to high temperatures for protracted periods of time. This increases the mean migration distance of a triton (at 700 °C held for 90 minutes) to be larger than the thickness of the sample.

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Iron nanoparticles have a number of magnetic properties that make them a potentially useful material for transformer applications. These desirable traits include high saturation magnetization, high susceptibility, and very low magnetic hysteresis. Before iron nanoparticles can even be tested for applicability, however, a number of scientific hurdles must be overcome. First an affordable and scalable synthetic approach must be developed, and the results of these large scale reactions must be fashioned into a solid material. To be of use, this solid material must have very high loading of iron nanoparticles and must be relatively easy to form into desired shapes. To achieve these goals, iron nanoparticles were synthesized by the thermal decomposition of iron pentacarbonyl in the presence of dodecylamine which bound to the surface of the particles. This reaction was scaled up to a multi-gram scale with only minor changes in size and shape control. These particles were then fashioned into “matrix-free nanocomposites”, where the particles were cross-linked to each other. This was achieved by first exchanging the surface coating for a combination of hexylamine and 1,6-diaminohexane. The diamine provided primary amines on the particle surface that were available for further reaction. These were shown to be capable of reacting with a triepoxide cross-linker to form a hard, solid material, analogous to the cure of a common epoxy adhesive. Loading of up to 80% iron by mass (about 43% by volume) was achieved.

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