Fe-Si/ZrO2 composites with core-shell structure and excellent magnetic properties prepared by mechanical milling and spark plasma sintering

Fe–6.5 wt.% Si powder coated with 10 wt.% MnZn(Fe2O4)2 (MnZn ferrite) was successfully prepared by using dry-type stirring ball milling. The Fe–6.5 wt.% Si/MnZn(Fe2O4)2 soft magnetic composites were prepared by subsequent spark plasma sintering. This paper aims at analyzing the microstructure and magnetic properties of Fe–6.5 wt.% Si/MnZn(Fe2O4)2 soft magnetic composites (sintering temperature: 750[Formula: see text]C, sintering pressure: 50 MPa, holding time: 8 min, heating rate: 60 K/min). Based on X-ray diffraction and scanning electron microscopy, microstructure and powder morphology were examined and magnetic measurements on bulk samples were conducted by vibrating sample magnetometer and impedance analyzer. According to the experiments results, Fe–6.5 wt.% Si/MnZn(Fe2O4)2 composites displayed a core-shell structure, and ceramic phase was observed after sintering. The Fe–6.5 wt.% Si/MnZn(Fe2O4)2 composites achieved high resistivity ([Formula: see text] m[Formula: see text]/cm) while maintaining excellent magnetic properties ([Formula: see text] emu/g). Core losses especially at medium and high frequencies were significantly reduced.

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Fabrication of high strength and plasticity of Zn-Mg composites with core–shell structure by spark plasma sintering

Materials Letters ◽

10.1016/j.matlet.2020.128525 ◽

2020 ◽

Vol 279 ◽

pp. 128525

Author(s):

Zeqin Cui ◽

Mengda Luo ◽

Yakai Zhang ◽

Dianqing Gong ◽

Wenxian Wang ◽

...

Keyword(s):

Spark Plasma Sintering ◽

Shell Structure ◽

High Strength ◽

Core Shell ◽

Plasma Sintering ◽

Spark Plasma ◽

Core Shell Structure ◽

Strength And Plasticity

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Fe-Si/MnZn(Fe2O4)2 Core-shell Composites with Excellent Magnetic Properties by Mechanical Milling and Spark Plasma Sintering (SPS)

Metals ◽

10.3390/met8070553 ◽

2018 ◽

Vol 8 (7) ◽

pp. 553 ◽

Cited By ~ 6

Author(s):

Liang Yan ◽

Biao Yan

Keyword(s):

Magnetic Properties ◽

Spark Plasma Sintering ◽

Mechanical Milling ◽

Core Shell ◽

Magnetic Composite ◽

Soft Magnetic ◽

Magnetic Composites ◽

Plasma Sintering ◽

Soft Magnetic Composites ◽

Spark Plasma

The Fe-Si/MnZn(Fe2O4)2 composite powders are synthetized by means of the mechanical milling, and Fe-Si/MnZn(Fe2O4)2 soft magnetic composites are prepared by spark plasma sintering (SPS). The impact of milling time on particle size, phase structure and magnetic properties of the investigative core-shell structure powders along with that of sintering temperature on microstructure and magnetic properties of FeSi-MnZn(Fe2O4)2 soft magnetic composite are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The experimental results demonstrate a layer of MnZn(Fe2O4)2 forming a coating on the surface of Fe-Si powder after mechanical milling, and the soft magnetic composites exhibiting excellent magnetic performance at 900 °C: 212.49 emu/g for saturation magnetization, with 6.89 Oe for coercivity, 3 × 10−4 Ω.m for electrical resistivity and stable amplitude permeability and low core loss over a wide frequency range. Therefore, SPS offers a convenient and swift way to enhance performance of soft magnetic composites using magnetic materials as insulting layer.

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Special microstructure evolution and enhanced magnetic properties of Ce-Fe-B-based spark plasma sintered magnets with core-shell structure by NdCu addition

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2018.10.114 ◽

2019 ◽

Vol 775 ◽

pp. 449-456 ◽

Cited By ~ 13

Author(s):

Qingzheng Jiang ◽

Weikai Lei ◽

Lunke He ◽

Qingwen Zeng ◽

Sajjad Ur Rehman ◽

...

Keyword(s):

Magnetic Properties ◽

Microstructure Evolution ◽

Shell Structure ◽

Core Shell ◽

Sintered Magnets ◽

Spark Plasma ◽

Core Shell Structure

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Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments

Materials ◽

10.3390/ma12091498 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1498 ◽

Cited By ~ 3

Author(s):

Awais Ikram ◽

M. Farhan Mehmood ◽

Zoran Samardžija ◽

Richard Stuart Sheridan ◽

Muhammad Awais ◽

...

Keyword(s):

Magnetic Properties ◽

Thermal Treatment ◽

Spark Plasma Sintering ◽

Treatment Time ◽

Weight Fraction ◽

Single Step ◽

Core Shell ◽

Shell Microstructure ◽

Plasma Sintering ◽

Spark Plasma

The magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF3 nanoparticles, were investigated. Spark plasma sintering (SPS) was used to consolidate the recycled Nd-Fe-B powder blends containing 1, 2, and 5 wt.% of DyF3 grounded powder. Different post-SPS sintering thermal treatment conditions (600, 750, and 900 °C), for a varying amount of time, were studied in view of optimizing the magnetic properties and developing characteristic core-shell microstructure in the HDDR powder. As received, recycled HDDR powder has coercivity (HCi) of 830 kA/m, and as optimally as SPS magnets reach 1160 kA/m, after the thermal treatment. With only 1–2 wt.% blended DyF3, the HCi peaked to 1407 kA/m with the thermal treatment at 750 °C for 1 h. The obtained HCi values of the blend magnet is ~69.5% higher than the starting recycled HDDR powder and 17.5% higher than the SPS processed magnet annealed at 750 °C for 1 h. Prolonging the thermal treatment time to 6 h and temperature conditions above 900 °C was detrimental to the magnetic properties. About ~2 wt.% DyF3 dopant was suitable to develop a uniform core-shell microstructure in the HDDR Nd-Fe-B powder. The Nd-rich phase in the HDDR powder has a slightly different and fluorine rich composition i.e., Nd-O-F2 than in the one reported in sintered magnets (Nd-O-F). The composition of reaction zone-phases after the thermal treatment and Dy diffusion was DyF4, which is more abundant in 5 wt.% doped samples. Further doping above 2 wt.% DyF3 is ineffective in augmenting the coercivity of the recycled HDDR powder, due to the decomposition of the shell structure and formation of non-ferromagnetic rare earth-based complex intermetallic compounds. The DyF3 doping is a very effective single step route in a controlled coercivity improvement of the recycled HDDR Nd-Fe-B powder from the end of life magnetic products.

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