Thermal stability of surface modified Sm2Co17-type high temperature magnets

Wang, Qingyun; Liu, Zheng; An, Shizhong; Zhang, Tianli; Jiang, Chengbao

doi:10.1016/j.jmmm.2012.11.013

Cited by 40 publications

(5 citation statements)

References 17 publications

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“…Chen et al (2004Chen et al ( , 2006 found that a pure Ni film with a best thickness of 15 μm can offer a good protection against oxidation in air at 500°C to a Sm 2 Co 17 -type magnet, preventing it from a considerable magnetic property loss. This result is well consistent with the work of Wang et al (2013), who indicated that the deposition of a ∼20-μm-thick Ni coating sharply decreased the mass gain of Sm( Co bal Fe 0.1 Cu 0.1 Zr 0.033 ) 6.93 magnet exposed for 500 h at 500°C, leading to a loss of the maximum energy product (BH) max from a normal 40.8% for the uncoated magnet down to only 4.0% in the presence of coating. Pragnell et al (2012) reported that the oxidation of a Sm(Co 0.74 Fe 0.1 Cu 0.12 Zr 0.04 ) 8.5 in air at 550°C was significantly suppressed by a 1.5-to 5-μm-thick Pt coating and a paint-like 5-to 10-μm-thick overlay coating containing Ti and Mg oxides, but their processing, composition, and microstructure are not presented in detail.…”

Section: Oxidation Protectionsupporting

confidence: 94%

“…Besides physical reasons (e.g., microstructural defects), chemical variation within the magnets by surface oxidation has been recently proposed to be a decisive (if not an exclusive) factor leading to the collapse of their cellular precipitations structure. Oxidation of the 2:17-type magnets has been investigated by some authors (Chen et al, , 2001Kardelky et al, 2004;Kardelky, (110) Gebert, Gutfleisch, Hoffmann, & Schultz, 2005;Liu & Walmer, 2005;Liu, Marinescu, Vora, Wu, & Harmer, 2009;Mao et al, 2014;Pauw et al, 1997;Pragnell, Williams, & Evans, 2008;Pragnell, Evans, & Williams, 2009;Wang, Zheng, An, Zhang, & Jiang, 2013;Yang et al, 2012Yang et al, , 2013a. The unacceptable coercivity loss may be prevented by adding appropriate surface coatings that can effectively offer oxidation protection to the magnets.…”

Section: Introductionmentioning

confidence: 99%

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On high-temperature oxidation and protection of 2:17-type SmCo-based magnets

et al. 2015

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Sm 2 (Co,Cu,Fe,Zr) 17 are the best high-temperature permanent magnets because of their high Curie temperature (800°C-850°C). However, irreversible and unacceptable coercivity losses retard their use in applications at temperatures over 550°C. The coercivity loss has been correlated with poor oxidation resistance at high temperatures. The current research progress on the effect of oxidation and its prevention, for 2:17-type magnets, is reviewed. Oxidation in air at 500°C-700°C causes the magnets to form three regions: (1) an external oxide scale mainly consisting of (Co x Fe 1-x ) 3 O 4 , (2) a thicker internal oxidation zone where the typical cellular precipitation (2:17R cell and 1:5H cell boundary) structure has been completely collapsed due to the Sm oxidation into Sm 2 O 3 , and (3) an oxidation-free zone where the cellular precipitates remain unchanged in lattice structure. No unacceptable coercivity loss is seen in the oxidation-free zone. Its thickness can be impressively increased within the magnets at high temperature, when they are covered with surface diffusion barriers for oxygen from the atmosphere, such as thin films of Cr 2 O 3 , Al 2 O 3 , and the metals with the ability to thermally grow these oxides.

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Section: Oxidation Protectionsupporting

confidence: 94%

Section: Introductionmentioning

confidence: 99%

On high-temperature oxidation and protection of 2:17-type SmCo-based magnets

et al. 2015

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“…However, these alloys have the disadvantage that a nanometric grain size is required to generate optimal magnetic properties, and this implies the use of drastic and complex processing conditions such as high potential application or the use of non aqueous solvents. [13][14][15][16] The primary way to prepare rare earth-transition metal alloy thin films has been the vacuum deposition by sputtering, being the main drawback of this procedure the difficulty of deposition onto recessed, high aspect substrates and the high cost. Electrodeposition is an alternative way to achieve the same objective with lower cost equipment and higher fabrication rates.…”

mentioning

confidence: 99%

Very Low Potential Electrodeposition of Sm-Co Nanostructures in Aqueous Medium Using Hard Templates

Herrera

Riva

López

et al. 2019

J. Electrochem. Soc.

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Arrays of SmCo nanowires (NW) and nanotubes (NT) with a diameter of 200 nm and different lengths are synthesized by electrodeposition into the nanopores of an alumina membrane. The potential applied during the synthesis largely determines the nanostructure morphology, its crystallinity and composition. Potentials investigated are between −0.8 V and −3.0 V; in the potential range between −0.8 V and 1.0 V, long and perfectly ordered nanowires are obtained with a composition close to that of the equilibrium Sm 2 Co 17 phase in the binary alloy. For higher potentials, above −1 V, samples are nanotubes, 195 nm in external diameter and wall thickness of 30 nm with an equiatomical composition. Magnetic characterization reveals that all the nanostructures are soft ferromagnetic, with coercivity values below 60 mT. From the angular dependence of coercivity and the relative remanence it may concluded that in both, nanowires and nanotubes the magnetization reversal mechanism undergoes a transition from one at smaller angles, involving localized nucleation by curling, and further expansion of vortex-like domain walls. At higher angles, where the applied field is almost perpendicular to the NW/NT long axis, the mechanism changes to one involving nucleation by localized coherent rotation and further expansion of transverse Bloch-like walls.

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“…A common strategy applied to stabilize SmCo NPs is to coat the preformed NPs with a layer of protecting materials to prevent the NPs from fast and deep oxidation. The protective coating material can be a metal (such as Ni or Cr) − or an inorganic oxide, but this coating tends to lower magnetic performance of the SmCo NPs due to the large fraction of nonmagnetic contribution from the coating material. Here, we report a new process to prepare SmCo NPs by chemical reduction method and to stabilize these NPs against fast air oxidation by a layer of nitrogen-doped graphitic carbon (NGC).…”

Section: Introductionmentioning

confidence: 99%

Stabilizing Hard Magnetic SmCo₅ Nanoparticles by N-Doped Graphitic Carbon Layer

Yue

Liu

et al. 2020

J. Am. Chem. Soc.

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We report a chemical method to synthesize size-controllable SmCo5 nanoparticles (NPs) and to stabilize the NPs against air oxidation by coating a layer of N-doped graphitic carbon (NGC). First 10 nm CoO and 5 nm Sm2O3 NPs were synthesized and aggregated in reverse micelles of oleylamine to form SmCo-oxide NPs with a controlled size (110, 150, or 200 nm). The SmCo-O NPs were then coated with polydopamine and thermally annealed to form SmCo-O/NGC NPs, which were further embedded in CaO matrix and reduced with Ca at 850 °C to give SmCo5/NGC NPs of 80, 120, or 180 nm, respectively. The 10 nm NGC coating efficiently stabilized the SmCo5 NPs against air oxidation at room temperature or at 100 °C. The magnetization value of the 180 nm SmCo5/NGC NPs was stabilized at 86.1 emu/g 5 days after air exposure at room temperature and dropped only 1.7% 48 h after air exposure at 100 °C. The stable SmCo5/NGC NPs were aligned magnetically in an epoxy resin, showing a square-like hysteresis behavior with their H c reaching 51.1 kOe at 150 K and 21.9 kOe at 330 K and their Mr stabilized at around 84.8 emu/g. Our study demonstrates a new strategy for synthesizing and stabilizing SmCo5 NPs for high-performance nanomagnet applications in a broad temperature range.

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Thermal stability of surface modified Sm2Co17-type high temperature magnets

Cited by 40 publications

References 17 publications

On high-temperature oxidation and protection of 2:17-type SmCo-based magnets

On high-temperature oxidation and protection of 2:17-type SmCo-based magnets

Very Low Potential Electrodeposition of Sm-Co Nanostructures in Aqueous Medium Using Hard Templates

Stabilizing Hard Magnetic SmCo₅ Nanoparticles by N-Doped Graphitic Carbon Layer

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Thermal stability of surface modified Sm2Co17-type high temperature magnets

Cited by 40 publications

References 17 publications

On high-temperature oxidation and protection of 2:17-type SmCo-based magnets

On high-temperature oxidation and protection of 2:17-type SmCo-based magnets

Very Low Potential Electrodeposition of Sm-Co Nanostructures in Aqueous Medium Using Hard Templates

Stabilizing Hard Magnetic SmCo5 Nanoparticles by N-Doped Graphitic Carbon Layer

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Product

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Stabilizing Hard Magnetic SmCo₅ Nanoparticles by N-Doped Graphitic Carbon Layer