University of Minnesota

Ut-Battelle, Inc.

The University of Tennessee Research Foundation

Yanfeng Jiang

Jian-Ping Wang

Bin Ma

Jinming Liu

Shihai He

Yiming Wu

Md Aminul Mehedi

Orlando Rios

Michael P Brady

Edgar Lara-Curzio

Craig A Bridges

Lawrence F Allard

Gerard Michael Ludtka

Delin Zhang

Xiaowei Zhang

Mahdi Jamali

Yang Lv

Fan Zhang

Roberta A Meisner

Example nanoparticles may include an iron-based core, and a shell. The shell may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example alloy compositions may include an iron-based grain, and a grain boundary. The grain boundary may include a non-magnetic, anti-ferromagnetic, or ferrimagnetic material. Example techniques for forming iron-based core-shell nanoparticles may include depositing a shell on an iron-based core. The depositing may include immersing the iron-based core in a salt composition for a predetermined period of time. The depositing may include milling the iron-based core with a salt composition for a predetermined period of time. Example techniques for treating a composition comprising core-shell nanoparticles may include nitriding the composition.

Iron-based nanoparticles and grains

A permanent magnet may include a FeNphase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a <001> crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a FeNphase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

Iron nitride permanent magnet and technique for forming iron nitride permanent magnet

The disclosure is directed to an iron-nitride material having a polycrystalline microstructure including a plurality of elongated crystallographic grains with grain boundaries, the iron-nitride material including at least one of an α″-FeNphase and a body-center-tetragonal (bct) phase comprising Fe and N. The disclosure is also directed a method producing an iron-nitride material. The method includes some combinations of preparing a raw material comprising iron, carrying out a microstructure build-up by annealing the prepared raw material at an elevated temperature and subsequently quenching the prepared raw material to produce a microstructure build-up material, annealing the microstructure build-up material, reducing the microstructure build-up material in a hydrogen environment, nitriding the reduced material to produce a nitrided material and subsequently quenching the nitrided material to a martensitic transformation temperature, stress annealing the nitrided material, and magnetic field annealing the stress-annealed material.

Iron-rich permanent magnet

An example composition may include a plurality of grains including an iron nitride phase. The plurality of grains may have an average grain size between about 10 nm and about 200 nm. An example technique may include treating a composition including a plurality of grains including an iron-based phase to adjust an average grain size of the plurality of grains to between about 20 nm and about 100 nm. The example technique may include nitriding the plurality of grains to form or grow an iron nitride phase.

Iron nitride compositions

A permanent magnet may include a FeNphase constitution. In some examples, the permanent magnet may be formed by a technique that includes straining an iron wire or sheet comprising at least one iron crystal in a direction substantially parallel to a &#x3c;001&#x3e; crystal axis of the iron crystal; nitridizing the iron wire or sheet to form a nitridized iron wire or sheet; annealing the nitridized iron wire or sheet to form a FeNphase constitution in at least a portion of the nitridized iron wire or sheet; and pressing the nitridized iron wires and sheets to form bulk permanent magnet.

A permanent magnet may include a FeNphase in a strained state. In some examples, strain may be preserved within the permanent magnet by a technique that includes etching an iron nitride-containing workpiece including FeNto introduce texture, straining the workpiece, and annealing the workpiece. In some examples, strain may be preserved within the permanent magnet by a technique that includes applying at a first temperature a layer of material to an iron nitride-containing workpiece including FeN, and bringing the layer of material and the iron nitride-containing workpiece to a second temperature, where the material has a different coefficient of thermal expansion than the iron nitride-containing workpiece. A permanent magnet including an FeNphase with preserved strain also is disclosed.

Preservation of strain in iron nitride magnet

Techniques are disclosed for milling an iron-containing raw material in the presence of a nitrogen source to generate anisotropically shaped particles that include iron nitride and have an aspect ratio of at least 1.4. Techniques for nitridizing an anisotropic particle including iron, and annealing an anisotropic particle including iron nitride to form at least one &#x3b1;&#x2033;-FeNphase domain within the anisotropic particle including iron nitride also are disclosed. In addition, techniques for aligning and joining anisotropic particles to form a bulk material including iron nitride, such as a bulk permanent magnet including at least one &#x3b1;&#x2033;-FeNphase domain, are described. Milling apparatuses utilizing elongated bars, an electric field, and a magnetic field also are disclosed.

Iron nitride powder with anisotropic shape

Techniques are disclosed concerning applied magnetic field synthesis and processing of iron nitride magnetic materials. Some methods concern casting a material including iron in the presence of an applied magnetic field to form a workpiece including at least one ironbased phase domain including uniaxial magnetic anisotropy, wherein the applied magnetic field has a strength of at least about 0.01 Tesla (T). Also disclosed are workpieces made by such methods, apparatus for making such workpieces and bulk materials made by such methods.

Applied magnetic field synthesis and processing of iron nitride magnetic materials

The disclosure describes techniques for forming hard magnetic materials including &#x3b1;&#x2033;-FeNusing chemical vapor deposition or liquid phase epitaxy and hard materials formed according to these techniques. A method comprises heating an iron source to form a vapor comprising an iron-containing compound; depositing iron from the vapor comprising the iron-containing compound and nitrogen from a vapor comprising a nitrogen-containing compound on a substrate to form a layer comprising iron and nitrogen; and annealing the layer comprising iron and nitrogen to form at least some crystals comprising &#x3b1;&#x2033;-FeN.

Forming iron nitride hard magnetic materials using chemical vapor deposition or liquid phase epitaxy

A bulk permanent magnetic material may include between about 5 volume percent and about 40 volume percent FeNphase domains, a plurality of nonmagnetic atoms or molecules forming domain wall pinning sites, and a balance soft magnetic material, wherein at least some of the soft magnetic material is magnetically coupled to the FeNphase domains via exchange spring coupling. In some examples, a bulk permanent magnetic material may be formed by implanting N+ ions in an iron workpiece using ion implantation to form an iron nitride workpiece, pre-annealing the iron nitride workpiece to attach the iron nitride workpiece to a substrate, and post-annealing the iron nitride workpiece to form FeNphase domains within the iron nitride workpiece.

A permanent magnet may include a Fe16N2 phase in a strained state. In some examples, strain may be preserved within the permanent magnet by a technique that includes etching an iron nitride-containing workpiece including Fe16N2 to introduce texture, straining the workpiece, and annealing the workpiece. In some examples, strain may be preserved within the permanent magnet by a technique that includes applying at a first temperature a layer of material to an iron nitride-containing workpiece including Fe16N2, and bringing the layer of material and the iron nitride-containing workpiece to a second temperature, where the material has a different coefficient of thermal expansion than the iron nitride-containing workpiece. A permanent magnet including an Fe16N2 phase with preserved strain also is disclosed.

The disclosure describes techniques for forming nanoparticles including FeNphase. In some examples, the nanoparticles may be formed by first forming nanoparticles including iron, nitrogen, and at least one of carbon or boron. The carbon or boron may be incorporated into the nanoparticles such that the iron, nitrogen, and at least one of carbon or boron are mixed. Alternatively, the at least one of carbon or boron may be coated on a surface of a nanoparticle including iron and nitrogen. The nano particle including iron, nitrogen, and at least one of carbon or boron then may be annealed to form at least one phase domain including at least one of FeN, Fe(NB), Fe(NC), or Fe(NCB).

Iron nitride magnetic material including coated nanoparticles

A method may include annealing a material including iron and nitrogen in the presence of an applied magnetic field to form at least one FeNphase domain. The applied magnetic field may have a strength of at least about 0.2 Tesla (T).

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Minneapolis, MN, United States of America

Yanfeng Jiang