Direct Reuse of Rare Earth Permanent Magnets—Coating Integrity

Stig Høgberg, Joachim Holbøll, Nenad Mijatovic, Bogi Bech Jensen, Flemming Buus Bendixen

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Rare earth permanent magnets can be reused directly as an alternative to traditional recycling methods, in which scrapped magnets are reprocessed into new magnets by undergoing many of the original energy-intensive and expensive production processes. Direct reuse entails using segmented magnet assemblies built by several small standard-sized magnets that can be reused directly in a number of different applications. A central part of the direct reuse strategy is to separate and demagnetize magnets by heating them to the Curie temperature. We investigated the validity of direct reuse as a rare earth magnet recycling strategy by evaluating the extent to which the heat-driven demagnetization cycles affected magnetic properties, as well as the integrity of the protective coating of Nd–Fe–B magnets. The experimental investigation consisted of four different tests, and was applied to 300 magnets that had either been heated once, five times, or none at all. The tests included $J$ – $H$ measurements, coating pull-off test, corrosion salt spray test, and optical microscopy of the interface between coating and magnet. Magnets coated with Zn, Epoxy, Ni–Cu–Ni, and Ni–Cu+Epoxy were investigated, of which Ni–Cu+Epoxy showed no degradation after heat treatment. Direct reuse as a recycling strategy could therefore be a valuable alternative to traditional recycling.
Original languageEnglish
Article number8000609
JournalIEEE Transactions on Magnetics
Volume53
Issue number4
Number of pages9
ISSN0018-9464
DOIs
Publication statusPublished - 2017

Keywords

  • Recycling
  • Coatings
  • Saturation magnetization
  • Magnetic separation
  • Magnetic flux
  • Torque
  • Heating
  • Recycling rare earth permanent magnet (REPM)
  • Direct drive wind turbine generator
  • Direct reuse
  • Experimental verification
  • Finite-element analysis

Cite this

Høgberg, Stig ; Holbøll, Joachim ; Mijatovic, Nenad ; Jensen, Bogi Bech ; Bendixen, Flemming Buus. / Direct Reuse of Rare Earth Permanent Magnets—Coating Integrity. In: IEEE Transactions on Magnetics. 2017 ; Vol. 53, No. 4.
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abstract = "Rare earth permanent magnets can be reused directly as an alternative to traditional recycling methods, in which scrapped magnets are reprocessed into new magnets by undergoing many of the original energy-intensive and expensive production processes. Direct reuse entails using segmented magnet assemblies built by several small standard-sized magnets that can be reused directly in a number of different applications. A central part of the direct reuse strategy is to separate and demagnetize magnets by heating them to the Curie temperature. We investigated the validity of direct reuse as a rare earth magnet recycling strategy by evaluating the extent to which the heat-driven demagnetization cycles affected magnetic properties, as well as the integrity of the protective coating of Nd–Fe–B magnets. The experimental investigation consisted of four different tests, and was applied to 300 magnets that had either been heated once, five times, or none at all. The tests included $J$ – $H$ measurements, coating pull-off test, corrosion salt spray test, and optical microscopy of the interface between coating and magnet. Magnets coated with Zn, Epoxy, Ni–Cu–Ni, and Ni–Cu+Epoxy were investigated, of which Ni–Cu+Epoxy showed no degradation after heat treatment. Direct reuse as a recycling strategy could therefore be a valuable alternative to traditional recycling.",
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Direct Reuse of Rare Earth Permanent Magnets—Coating Integrity. / Høgberg, Stig; Holbøll, Joachim; Mijatovic, Nenad; Jensen, Bogi Bech; Bendixen, Flemming Buus.

In: IEEE Transactions on Magnetics, Vol. 53, No. 4, 8000609, 2017.

Research output: Contribution to journalJournal articleResearchpeer-review

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T1 - Direct Reuse of Rare Earth Permanent Magnets—Coating Integrity

AU - Høgberg, Stig

AU - Holbøll, Joachim

AU - Mijatovic, Nenad

AU - Jensen, Bogi Bech

AU - Bendixen, Flemming Buus

PY - 2017

Y1 - 2017

N2 - Rare earth permanent magnets can be reused directly as an alternative to traditional recycling methods, in which scrapped magnets are reprocessed into new magnets by undergoing many of the original energy-intensive and expensive production processes. Direct reuse entails using segmented magnet assemblies built by several small standard-sized magnets that can be reused directly in a number of different applications. A central part of the direct reuse strategy is to separate and demagnetize magnets by heating them to the Curie temperature. We investigated the validity of direct reuse as a rare earth magnet recycling strategy by evaluating the extent to which the heat-driven demagnetization cycles affected magnetic properties, as well as the integrity of the protective coating of Nd–Fe–B magnets. The experimental investigation consisted of four different tests, and was applied to 300 magnets that had either been heated once, five times, or none at all. The tests included $J$ – $H$ measurements, coating pull-off test, corrosion salt spray test, and optical microscopy of the interface between coating and magnet. Magnets coated with Zn, Epoxy, Ni–Cu–Ni, and Ni–Cu+Epoxy were investigated, of which Ni–Cu+Epoxy showed no degradation after heat treatment. Direct reuse as a recycling strategy could therefore be a valuable alternative to traditional recycling.

AB - Rare earth permanent magnets can be reused directly as an alternative to traditional recycling methods, in which scrapped magnets are reprocessed into new magnets by undergoing many of the original energy-intensive and expensive production processes. Direct reuse entails using segmented magnet assemblies built by several small standard-sized magnets that can be reused directly in a number of different applications. A central part of the direct reuse strategy is to separate and demagnetize magnets by heating them to the Curie temperature. We investigated the validity of direct reuse as a rare earth magnet recycling strategy by evaluating the extent to which the heat-driven demagnetization cycles affected magnetic properties, as well as the integrity of the protective coating of Nd–Fe–B magnets. The experimental investigation consisted of four different tests, and was applied to 300 magnets that had either been heated once, five times, or none at all. The tests included $J$ – $H$ measurements, coating pull-off test, corrosion salt spray test, and optical microscopy of the interface between coating and magnet. Magnets coated with Zn, Epoxy, Ni–Cu–Ni, and Ni–Cu+Epoxy were investigated, of which Ni–Cu+Epoxy showed no degradation after heat treatment. Direct reuse as a recycling strategy could therefore be a valuable alternative to traditional recycling.

KW - Recycling

KW - Coatings

KW - Saturation magnetization

KW - Magnetic separation

KW - Magnetic flux

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KW - Direct drive wind turbine generator

KW - Direct reuse

KW - Experimental verification

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