Hard magnetic materials

Wohlfarth, E.P.

doi:10.1080/00018735900101178

Cited by 112 publications

(16 citation statements)

References 225 publications

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“…According to [2] the volume fraction of particles in a material with an organic coating is 0.6-0.61, which is in good agreement with [9]. Comparing the properties of powder magnets [8] with the reference magnetic properties [9] shows that the achieved level of magnetic parameters is no more than 70-75%.…”

supporting

confidence: 64%

“…This is because perfect anisotropic particles cannot be obtained by electrolysis in a two-layer bath due to uncontrolled treeing, which decreases coercive force and magnetic energy. The current results are no more than 10-15% of the calculated data [2,10]. Nevertheless, by improving the electrolysis in combination with other techniques, one may substantially improve the shape and increase the anisotropy of particles, and improve the quality of powder and, thus, the properties of permanent powder magnets.…”

mentioning

confidence: 70%

“…It is shown that magnetic materials produced by powder metallurgy methods can compete with YUNDK-15.18 industrial cast alloys.Keywords: permanent powder magnets, polymer binder, coercive force, specific magnetic energy, pressing.The properties of permanent powder magnets (PPMs) depend on manufacturing techniques, amount of binder, powder production technology, etc.Depending on the requirements imposed on PPMs, they can be produced using conventional pressing followed by the polymerization of the binder, warm pressing combining forming and polymerization in one cycle, or pressing of magnetically oriented particles followed by the polymerization of the binder in a heated mold [1,2].The objective of this paper is to establish characteristics of PPMs with a binder to find the most efficient use of these materials. To characterize the stability of magnetic properties, we used α, the ratio of residual flux density B r to saturation flux density B s .…”

mentioning

confidence: 99%

“…Depending on the requirements imposed on PPMs, they can be produced using conventional pressing followed by the polymerization of the binder, warm pressing combining forming and polymerization in one cycle, or pressing of magnetically oriented particles followed by the polymerization of the binder in a heated mold [1,2].…”

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confidence: 99%

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Effect of different production methods on the properties of permanent magnet powders

Nepomnyashchii

Mosina

Radchenko

et al. 2009

Powder Metall Met Ceram

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The paper examines how the properties of permanent powder magnets depend on their chemical and phase composition and production methods. It is shown that magnetic materials produced by powder metallurgy methods can compete with YUNDK-15.18 industrial cast alloys.Keywords: permanent powder magnets, polymer binder, coercive force, specific magnetic energy, pressing.The properties of permanent powder magnets (PPMs) depend on manufacturing techniques, amount of binder, powder production technology, etc.Depending on the requirements imposed on PPMs, they can be produced using conventional pressing followed by the polymerization of the binder, warm pressing combining forming and polymerization in one cycle, or pressing of magnetically oriented particles followed by the polymerization of the binder in a heated mold [1,2].The objective of this paper is to establish characteristics of PPMs with a binder to find the most efficient use of these materials. To characterize the stability of magnetic properties, we used α, the ratio of residual flux density B r to saturation flux density B s . This paper studies how methods of producing PPMs with a polymer binder influence their properties. The materials were made of quasi-single-domain iron particles and iron-cobalt alloy with an organic coating.To produce PPMs, we used superfine powders electrolyzed in a two-layer bath, which were subjected to recovery annealing as described in [3,4]. The methods previously outlined in [5][6][7] were used to make reference samples of these powders, examine their magnetic and mechanical characteristics, and determine their chemical composition.Particles in powder mixtures used for forming PPMs were of different content and orientation per unit volume. Figure 1 shows the specific magnetic energy (W max ) of materials produced with different methods.Cold pressing is appropriate for large-scale production of simple-shape parts whose magnetic properties are not subject to heavy demands. In cold pressing, a binder acts as a filling agent and its cohesiveness shows up only in subsequent heating. If heating is insufficient, the binder is not polymerized completely, resulting in inadequate strength. When materials are required to have good magnetic properties, warm pressing with or without a magnetic field should be used. These methods produce materials with a higher density as the binder is plasticized and with

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confidence: 64%

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confidence: 70%

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confidence: 99%

mentioning

confidence: 99%

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Effect of different production methods on the properties of permanent magnet powders

Nepomnyashchii

Mosina

Radchenko

et al. 2009

Powder Metall Met Ceram

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“…Wohlfarth (1959) states that single crystals of r Fe203 do not exist, which suggests that the r phase is a oxidation product of a Q phase. In Class II rocks the j to r alteration is' not completed since a a phase remains even after the r to a transition.…”

Section: Resultsmentioning

confidence: 99%