Plasma sprayed Nd–Fe–B permanent magnets

Willson, M. C.; Bauser, S.; Liu, S.; Huang, Mei

doi:10.1063/1.1558590

Cited by 8 publications

(2 citation statements)

References 2 publications

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“…However, thermal spraying can make REEs prone to oxidation during processing and operation, and oxidation can lead to brittle coatings and deterioration of magnetic properties. [ 163 ] Therefore, with certain microstructure formation limitations, spraying performed within a vacuum chamber to minimize oxidation, [ 168 ] as well as application of CS, can be a way forward. [ 169 ]…”

Section: Special Considerations For Enhanced Em Wave Propagation Char...mentioning

confidence: 99%

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

et al. 2022

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This review aims to consolidate scattered literature on thermally sprayed coatings with nonionizing electromagnetic (EM) wave absorption and shielding over specific wavelengths potentially useful in diverse applications (e.g., microwave to millimeter wave, solar selective, photocatalytic, interference shielding, thermal barrier‐heat/emissivity). Materials EM properties such as electric permittivity, magnetic permeability, electrical conductivity, and dielectric loss are critical due to which a material can respond to absorbed, reflected, transmitted, or may excite surface electromagnetic waves at frequencies typical of electromagnetic radiations. Thermal spraying is a standard industrial practice used for depositing coatings where the sprayed layer is formed by successive impact of fully or partially molten droplets/particles of a material exposed to high or moderate temperatures and velocities. However, as an emerging novel application of an existing thermal spray techniques, some special considerations are warranted for targeted development involving relevant characterization. Key potential research areas of development relating to material selection and coating fabrication strategies and their impact on existing practices in the field are identified. The study shows a research gap in the feedstock materials design and doping, and their complex selection covered by thermally sprayed coatings that can be critical to advancing applications exploiting their electromagnetic properties.

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Section: Special Considerations For Enhanced Em Wave Propagation Char...mentioning

confidence: 99%

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

et al. 2022

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“…Most studies on the fabrication of permanent magnet films have focused on low temperature processes such as sputtering: a thin film method that has technical limitations with regard to processing time, restrictions concerning the geometry and size of the component, and a cost penalty. In cases where thermal spray has been employed, spraying has been mostly performed within a vacuum chamber to minimize oxidation (Ref [10][11][12]. Recent studies have examined the low temperature cold spray process (Ref 13).…”

Section: Introductionmentioning

confidence: 99%

Review on the Oxidation of Metallic Thermal Sprayed Coatings: A Case Study with Reference to Rare-Earth Permanent Magnetic Coatings

Gan

Berndt

2013

J Therm Spray Tech

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Thermal spray fabrication of rare-earth permanent magnetic coatings (PMCs) presents potential manufacturing routes for micro-magnetic devices. Despite this potential, thermal spray of PMCs is still not widely explored due to oxidation concerns. It was established that oxidation leads to the loss of ferromagnetic phases in these materials and results in deterioration of magnetic performance. Although this review focuses on a specific class of material, i.e., magnetic materials, there is significant technical crossover to all classes of feedstocks that are employed in thermal spray processing. The oxidation mechanisms and the associated influencing factors are explored in this work to implement effective processing techniques during the deposition process. This paper reviews the various stages and mechanisms of oxidation in thermal spray processes. The factors that influence the extent of oxidation depend on the type of oxidation that is dominant and rely on the type of spray system, powder injection position, and the particle size of feedstock. Among the aspects that are reviewed include the oxygen-fuel ratio for high velocity oxygen-fuel (HVOF), current intensity, gas flow rate, particle size, spray distance, and substrate temperature. Protection strategies to minimize oxidation in thermal spray processes, such as gas shrouding and shielding, are presented.

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Rare‐earth Transition‐metal Magnets

Rodewald¹

2007

Handbook of Magnetism and Advanced Magnetic Materials

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Most of the SmCo or NdFeB magnets are produced by powder metallurgy in a large variety of shapes. The basic production processes and their impact on the magnetic properties are reported. Alternative production routes and the achieved magnetic properties are reviewed. The magnetization of rare‐earth transition‐metal (RE–TM) magnets and the different coercivity mechanisms are presented in order to assist in proper application. Commercial NdFeB magnets can be operated at temperatures up to 230 °C. Owing to the higher Curie temperatures, sintered SmCo 5 magnets can be applied up to 250 °C, standard Sm 2 (Co,Cu,Fe,Zr) 17 magnets up to 350 °C, and newly developed Sm 2 (Co,Cu,Fe,Zr) 17 magnets even up to 550 °C. The basic features, which determine the temperature stability of RE–TM magnets, are discussed in detail. Sometimes, RE–TM magnets need to be operated in hot and humid climates. The RE‐rich constituents of sintered NdFeB magnets are sensitive to corrosion by oxidation and hydrogen embrittlement, which may result in a disintegration of surface layers. The corrosion stability of advanced NdFeB magnets could be improved significantly by replacing corrosion‐sensitive constituents by more noble compounds. In aggressive climates, however, NdFeB magnets need protection by proper coatings. In contrast, SmCo 5 or Sm 2 (Co,Cu,Fe,Zr) 17 magnets hardly suffer any corrosion in hot and humid climates. In applications, sintered magnets may experience mechanical stress. Some mechanical properties of sintered NdFeB magnets, for instance, the compression and the bending strength, the fracture toughness, the Young's modulus, and the Vickers hardness are reviewed, depending on the average grain size.

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Plasma sprayed Nd–Fe–B permanent magnets

Cited by 8 publications

References 2 publications

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

Thermal Spray Coatings for Electromagnetic Wave Absorption and Interference Shielding: A Review and Future Challenges

Review on the Oxidation of Metallic Thermal Sprayed Coatings: A Case Study with Reference to Rare-Earth Permanent Magnetic Coatings

Rare‐earth Transition‐metal Magnets

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