Editorial

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4 pages, 179 KiB

Open AccessEditorial

Advances in Metal-Containing Magnetic Materials and Magnetic Technologies

by Zhongwu Liu

Metals 2023, 13(7), 1318; https://doi.org/10.3390/met13071318 - 24 Jul 2023

Viewed by 855

Abstract

Magnetic materials generally refer to materials with ferromagnetic or ferrimagnetic ordering [...] Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

Research

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14 pages, 4524 KiB

Open AccessArticle

Enhanced Magnetic Properties and Thermal Conductivity of FeSiCr Soft Magnetic Composite with Al₂O₃ Insulation Layer Prepared by Sol-Gel Process

by Qintian Xie, Hongya Yu, Han Yuan, Guangze Han, Xi Chen and Zhongwu Liu

Metals 2023, 13(4), 813; https://doi.org/10.3390/met13040813 - 21 Apr 2023

Cited by 3 | Viewed by 1276

Abstract

FeSiCr soft magnetic composites (SMCs) were fabricated by the sol-gel method, and an Al₂O₃/resin composite layer was employed as the insulation coating. By the decomposition of boehmite (AlOOH) gel into Al₂O₃ in the temperature range of [...] Read more.

FeSiCr soft magnetic composites (SMCs) were fabricated by the sol-gel method, and an Al₂O₃/resin composite layer was employed as the insulation coating. By the decomposition of boehmite (AlOOH) gel into Al₂O₃ in the temperature range of 606–707 °C, a uniform Al₂O₃ layer could be formed on the FeSiCr powder surface. The Al₂O₃ insulation coating not only effectively reduced the core loss, increased the resistivity, and improved the quality factor, but it also increased the thermal conductivity of SMCs. The best overall properties with saturation magnetization M_s = 188 emu/g, effective permeability μ_e = 39, resistivity ρ = 8.28 × 10⁵ Ω·cm, quality factor Q = 94 at 1 MHz, and core loss = 1173 mW/cm³ at 200 kHz and 50 mT were obtained when the SMC was prepared with powders coated by 0.5 wt.% Al₂O₃ and resin. The optimized SMC exhibited the lowest core loss with 27% reduction compared to the resin only-insulated sample and 71% reduction compared to the sample without insulation treatment. Importantly, the thermal conductivity of the SMCs is 5.3 W/m·K at room temperature, which is higher than that of the samples prepared by phosphating and SiO₂ coating owing to the presence of a high thermal conductive Al₂O₃ layer. The high thermal conductivity is beneficial to enhancing the high temperature performance, lifetime, and reliability of SMCs. This work is expected to be a valuable reference for the design and fabrication of SMCs to be applied in high-temperature and high-frequency environments. Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

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14 pages, 6096 KiB

Open AccessFeature PaperArticle

Properties Optimization of Soft Magnetic Composites Based on the Amorphous Powders with Double Layer Inorganic Coating by Phosphating and Sodium Silicate Treatment

by Pan Luo, Hongya Yu, Ce Wang, Han Yuan, Zhongwu Liu, Yu Wang, Lu Yang and Wenjie Wu

Metals 2023, 13(3), 560; https://doi.org/10.3390/met13030560 - 10 Mar 2023

Cited by 4 | Viewed by 1383

Abstract

Core-shell structured amorphous FeSiBCr@phosphate/silica powders were prepared by phosphating and sodium silicate treatment. The soft magnetic composites (SMCs) were fabricated based on these powders. The effects of phosphoric acid (H₃PO₄) concentration and annealing temperature on their properties were investigated. [...] Read more.

Core-shell structured amorphous FeSiBCr@phosphate/silica powders were prepared by phosphating and sodium silicate treatment. The soft magnetic composites (SMCs) were fabricated based on these powders. The effects of phosphoric acid (H₃PO₄) concentration and annealing temperature on their properties were investigated. During the phosphating process, the powder coated with a low concentration of H₃PO₄-ethanol solution leads to uneven phosphate coating, while the peeling of phosphate coating occurs for the high H₃PO₄ concentration. Using 0.5 wt.% phosphoric solution, a uniform and dense insulation layer can be formed on the surface of the powder, resulting in increased resistivity and the reduced eddy current loss of the amorphous soft magnetic composites (ASMCs). This insulation layer can increase the roughness of the powder surface, which is beneficial to the subsequent coating of sodium silicate. By optimizing sodium silicate treatment, a complete and uniform SiO₂ layer can be formed on the phosphated powders well, leading to double layer core-shell structure and excellent soft magnetic properties. The magnetic properties of amorphous SMCs can be further improved by post annealing due to the effectively released residual stress. The enhanced permeability and greatly reduced core loss can be achieved by annealing at 773 K, but the deterioration of magnetic properties occurs as the annealing temperature over 798 K, mainly due to the increase of α-Fe(Si) and Fe₃B phases, which hinder the domain wall displacement and magnetic moment rotation. The excellent soft magnetic properties with permeability μ_e = 35 and core loss P_s = 368 kW/m³ at 50 mT/200 kHz have been obtained when the SMCs prepared with the powders coated by 0.5 wt.% H₃PO₄ and 2 wt.% sodium silicate were annealed at 773 K. Full article

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9 pages, 2087 KiB

Open AccessArticle

Effect of Ho Substitution on Magnetic Properties and Microstructure of Nanocrystalline Nd-Pr-Fe-B Alloys

by Caihai Xiao, Weiwei Zeng, Yongli Tang, Cifu Lu, Renheng Tang, Zhigang Zheng, Xuefeng Liao and Qing Zhou

Metals 2022, 12(11), 1922; https://doi.org/10.3390/met12111922 - 09 Nov 2022

Cited by 3 | Viewed by 1015

Abstract

The inevitable thermal demagnetization of magnets at high-temperatures is a key issue for Nd-Fe-B based permanent magnetic materials, especially for electric motors. Here, we report the effect of partially substituting the element Holmium (Ho) on the magnetic properties and microstructure of nanocrystalline melt-spun [...] Read more.

The inevitable thermal demagnetization of magnets at high-temperatures is a key issue for Nd-Fe-B based permanent magnetic materials, especially for electric motors. Here, we report the effect of partially substituting the element Holmium (Ho) on the magnetic properties and microstructure of nanocrystalline melt-spun [(NdPr)_1−xHo_x]_14.3Fe_76.9B_5.9M_2.9 (x = 0–0.6; M = Co, Cu, Al and Ga) alloys. It shows that Ho can enter into the main phase and significantly enhance the coercivity (H_cj). A large coercivity of 23.9 kOe is achieved in the x = 0.3 alloy, and the remanent magnetization (M_r) remains in balance. The abnormal elevated temperature behavior of M_r is observed in the alloys with a high amount of Ho substitution, in which the M_r of the x = 0.6 alloy increases with rising temperature from 300 K to 375 K owing to the antiparallel coupling between Ho and Fe moments. As a result, the positive value (0.050%/K) of temperature coefficient α of M_r is achieved in the x = 0.6 alloy within the temperature range of 300–400 K, in excess of that of existing Nd-Fe-B magnets. The temperature coefficient β of H_cj is also improved by Ho substitution, indicating the introduction of Ho in Nd-Fe-B magnets is beneficial for thermal stability. The microstructure observation of x = 0, 0.3 and 0.6 alloys confirmed the grain refinement by Ho substitution, and Ho prefers to remain in the 2:14:1 phase than Nd and Pr. The present finding provides an important reference for the efficient improvement of the thermal stability of Nd-Fe-B-type materials. Full article

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8 pages, 1832 KiB

Open AccessFeature PaperArticle

Enhancing the Properties of FeSiBCr Amorphous Soft Magnetic Composites by Annealing Treatments

by Hongya Yu, Jiaming Li, Jingzhou Li, Xi Chen, Guangze Han, Jianmin Yang and Rongyin Chen

Metals 2022, 12(5), 828; https://doi.org/10.3390/met12050828 - 11 May 2022

Cited by 11 | Viewed by 1678

Abstract

Fe-based amorphous powder cores (AMPCs) were prepared from FeSiBCr amorphous powders with phosphate–resin hybrid coating. The high-frequency magnetic properties of AMPCs annealed at different temperatures were systematically studied. After annealing at low temperatures, the effective permeability and core loss improved due to the [...] Read more.

Fe-based amorphous powder cores (AMPCs) were prepared from FeSiBCr amorphous powders with phosphate–resin hybrid coating. The high-frequency magnetic properties of AMPCs annealed at different temperatures were systematically studied. After annealing at low temperatures, the effective permeability and core loss improved due to the internal stress of the powder cores being released. The sample annealed at 480 °C exhibits the lowest hysteresis loss of about 29.6 mW/cm³ at 800 kHz as well as a maximum effective permeability of 36.4, remaining stable until 3 MHz, which could be useful for high-frequency applications. Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

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12 pages, 3928 KiB

Open AccessArticle

Correction Method of Three-Axis Magnetic Sensor Based on DA–LM

by Li Yang, Caihong Li, Song Zhang, Chaoqun Xu, Hun Chen, Shuting Xiao, Xiaoyu Tang and Yongxin Li

Metals 2022, 12(3), 428; https://doi.org/10.3390/met12030428 - 28 Feb 2022

Cited by 3 | Viewed by 2016

Abstract

The fluxgate magnetometer has the advantages of having a small volume and low power consumption and being light weight and is commonly used to detect weak magnetic targets, including ferrous metals, unexploded bombs (UXOs), and underground corrosion pipelines. However, the detection accuracy of [...] Read more.

The fluxgate magnetometer has the advantages of having a small volume and low power consumption and being light weight and is commonly used to detect weak magnetic targets, including ferrous metals, unexploded bombs (UXOs), and underground corrosion pipelines. However, the detection accuracy of the fluxgate magnetometer is affected by its own error. To obtain more accurate detection data, the sensor must be error-corrected before application. Previous researchers easily fell into the local minimum when solving error parameters. In this paper, the error correction method was proposed to tackle the problem, which combines the Dragonfly algorithm (DA) and the Levenberg–Marquardt (LM) algorithm, thereby solving the problem of the LM algorithm and improving the accuracy of solving error parameters. Firstly, we analyzed the error sources of the three-axis magnetic sensor and established the error model. Then, the error parameters were solved by using the LM algorithm and DA–LM algorithm, respectively. In addition, by comparing the results of the two methods, we found that the error parameters solved by using the DA–LM algorithm were more accurate. Finally, the magnetic measurement data were corrected. The simulation results show that the DA–LM algorithm can accurately solve the error parameters of the triaxial magnetic sensor, proving the effectiveness of the proposed algorithm. The experimental results show that the difference between the corrected and the ideal total value was decreased from 300 nT to 5 nT, which further verified the effectiveness of the DA–LM algorithm. Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

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16 pages, 8356 KiB

Open AccessArticle

One-Step Sintering Process for the Production of Magnetocaloric La(Fe,Si)₁₃-Based Composites

by Xi-Chun Zhong, Xu-Tao Dong, Jiao-Hong Huang, Cui-Lan Liu, Hu Zhang, You-Lin Huang, Hong-Ya Yu and Raju V. Ramanujan

Metals 2022, 12(1), 112; https://doi.org/10.3390/met12010112 - 06 Jan 2022

Cited by 7 | Viewed by 1527

Abstract

A one-step sintering process was developed to produce magnetocaloric La(Fe,Si)₁₃/Ce-Co composites. The effects of Ce₂Co₇ content and sintering time on the relevant phase transformations were determined. Following sintering at 1373 K/30 MPa for 1–6 h, the NaZn₁₃ [...] Read more.

A one-step sintering process was developed to produce magnetocaloric La(Fe,Si)₁₃/Ce-Co composites. The effects of Ce₂Co₇ content and sintering time on the relevant phase transformations were determined. Following sintering at 1373 K/30 MPa for 1–6 h, the NaZn₁₃-type (La,Ce)(Fe,Co,Si)₁₃ phase formed, the mass fraction of α-Fe phase reduced and the CeFe₇-type (La,Ce)(Fe,Co,Si)₇ phase appeared. The mass fraction of the (La,Ce)(Fe,Co,Si)₇ phase increased, and the α-Fe phase content decreased with increasing Ce₂Co₇ content. However, the mass fraction of the (La,Ce)(Fe,Co,Si)₇ phase reduced with increasing sintering time. The EDS results showed a difference in concentration between Co and Ce at the interphase boundary between the 1:13 phase and the 1:7 phase, indicating that the diffusion mode of Ce is reaction diffusion, while that of Co is the usual vacancy mechanism. Interestingly, almost 100 % single phase (La,Ce)(Fe,Co,Si)₁₃ was obtained by appropriate Ce₂Co₇ addition. After 6 h sintering at 1373 K, the Ce and Co content in the (La,Ce)(Fe,Co,Si)₁₃ phase increased for larger Ce₂Co₇ content. Therefore, the Curie temperature increased from 212 K (binder-free sample) to 331 K (15 wt.% Ce₂Co₇ sample). The maximum magnetic entropy change (−ΔS_M)^max decreased from 8.8 (binder-free sample) to 6.0 J/kg·K (15 wt.% Ce₂Co₇ sample) under 5 T field. High values of compressive strength (σ_bc)^max of up to 450 MPa and high thermal conductivity (λ) of up to 7.5 W/m·K were obtained. A feasible route to produce high quality La(Fe,Si)₁₃ based magnetocaloric composites with large MCE, good mechanical properties, attractive thermal conductivity and tunable T_C by a one-step sintering process has been demonstrated. Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

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9 pages, 6591 KiB

Open AccessArticle

Surface Investigation of Ni₈₁Fe₁₉ Thin Film: Using ARXPS for Thickness Estimation of Oxidation Layers

by Zongsheng He, Ziyu Li, Xiaona Jiang, Chuanjian Wu, Yu Liu, Xinglian Song, Zhong Yu, Yifan Wang, Zhongwen Lan and Ke Sun

Metals 2021, 11(12), 2061; https://doi.org/10.3390/met11122061 - 20 Dec 2021

Cited by 4 | Viewed by 2374

Abstract

This work demonstrates the dependence between magnetic properties and the thickness of NiFe thin films. More importantly, a quantitative study of the surface composition of NiFe thin film exposed to atmospheric conditions has been carried out employing angle-resolved X-ray photoelectron spectroscopy (ARXPS). In [...] Read more.

This work demonstrates the dependence between magnetic properties and the thickness of NiFe thin films. More importantly, a quantitative study of the surface composition of NiFe thin film exposed to atmospheric conditions has been carried out employing angle-resolved X-ray photoelectron spectroscopy (ARXPS). In this study, we fabricated Ni₈₁Fe₁₉ (NiFe) thin films on Si (100) substrate using electron beam evaporation and investigated their surface morphologies, magnetic properties, and the thickness of the surface oxide layer. The coexistence of metallic and oxidized species on the surface are suggested by the depth profile of ARXPS spectra. The thickness of the oxidized species, including NiO, Ni(OH)₂, Fe₂O₃, and Fe₃O₄, are also estimated based on the ARXPS results. This work provides an effective approach to clarify the surface composition, as well as the thickness of the oxide layer of the thin films. Full article

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12 pages, 5420 KiB

Open AccessArticle

Researching a Moving Target Detection Method Based on Magnetic Flux Induction Technology

by Chaoqun Xu, Li Yang, Kui Huang, Yang Gao, Shaohua Zhang, Yuting Gao, Lifei Meng, Qi Xiao, Chaobo Liu, Bin Wang and Zhong Yi

Metals 2021, 11(12), 1967; https://doi.org/10.3390/met11121967 - 07 Dec 2021

Cited by 3 | Viewed by 1973

Abstract

The ocean is a very important arena in modern warfare where all marine powers deploy their military forces. Due to the complex environment of the ocean, underwater equipment has become a very threatening means of surprise attack in modern warfare. Therefore, the timely [...] Read more.

The ocean is a very important arena in modern warfare where all marine powers deploy their military forces. Due to the complex environment of the ocean, underwater equipment has become a very threatening means of surprise attack in modern warfare. Therefore, the timely and effective detection of underwater moving targets is the key to obtaining warfare advantages and has important strategic significance for national security. In this paper, magnetic flux induction technology was studied with regard to the difficulty of detecting underwater concealed moving targets. Firstly, the characteristics of a magnetic target were analyzed and an equivalent magnetic dipole model was established. Secondly, the structure of the rectangular induction coil was designed according to the model, and the relationship between the target’s magnetism and the detection signal was deduced. The variation curves of the magnetic flux and the electromotive force induced in the coil were calculated by using the numerical simulation method, and the effects of the different motion parameters of the magnetic dipole and the size parameters of the coil on the induced electromotive force were analyzed. Finally, combined with the wavelet threshold filter, a series of field tests were carried out using ships of different materials in shallow water in order to verify the moving target detection method based on magnetic flux induction technology. The results showed that this method has an obvious response to moving targets and can effectively capture target signals, which verifies the feasibility of the magnetic flux induction detection technology. Full article

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8 pages, 4192 KiB

Open AccessEditor’s ChoiceArticle

Effects of La on Thermal Stability, Phase Formation and Magnetic Properties of Fe–Co–Ni–Si–B–La High Entropy Alloys

by Jiaming Li, Jianliang Zuo and Hongya Yu

Metals 2021, 11(12), 1907; https://doi.org/10.3390/met11121907 - 26 Nov 2021

Cited by 7 | Viewed by 2281

Abstract

The microstructure, phase formation, thermal stability and soft magnetic properties of melt-spun high entropy alloys (HEAs) Fe₂₇Co₂₇Ni₂₇Si_10−xB₉La_x with various La substitutions for Si (x = 0, 0.2, 0.4, 0.6, 0.8, and [...] Read more.

The microstructure, phase formation, thermal stability and soft magnetic properties of melt-spun high entropy alloys (HEAs) Fe₂₇Co₂₇Ni₂₇Si_10−xB₉La_x with various La substitutions for Si (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) were investigated in this work. The Fe₂₇Co₂₇Ni₂₇Si_10−xB₉La_0.6 alloy shows superior soft magnetic properties with low coercivity H_c of ~7.1 A/m and high saturation magnetization B_s of 1.07 T. The content of La has an important effect on the primary crystallization temperature (T_x1) and the secondary crystallization temperature (T_x2) of the alloys. After annealing at relatively low temperature, the saturation magnetization of the alloy increases and the microstructure with a small amount of body-centered cubic (BCC) phase embedded in amorphous matrix is observed. Increasing the annealing temperature reduces the magnetization due to the transformation of BCC phase into face-centered cubic (FCC) phase. Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

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Review

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27 pages, 50279 KiB

Open AccessReview

Recent Advances in Magnetostrictive Tb-Dy-Fe Alloys

by Zijing Yang, Jiheng Li, Zhiguang Zhou, Jiaxin Gong, Xiaoqian Bao and Xuexu Gao

Metals 2022, 12(2), 341; https://doi.org/10.3390/met12020341 - 15 Feb 2022

Cited by 7 | Viewed by 2591

Abstract

As giant magnetostrictive materials with low magnetocrystalline anisotropy, Tb-Dy-Fe alloys are widely used in transducers, actuators and sensors due to the effective conversion between magnetic energy and mechanical energy (or acoustic energy). However, the intrinsic brittleness of intermetallic compounds leads to their poor [...] Read more.

As giant magnetostrictive materials with low magnetocrystalline anisotropy, Tb-Dy-Fe alloys are widely used in transducers, actuators and sensors due to the effective conversion between magnetic energy and mechanical energy (or acoustic energy). However, the intrinsic brittleness of intermetallic compounds leads to their poor machinability and makes them prone to fracture, which limits their practical applications. Recently, the addition of a fourth element to Tb-Dy-Fe alloys, such as Ho, Pr, Co, Nb, Cu and Ti, has been studied to improve their magnetostrictive and mechanical properties. This review starts with a brief introduction to the characteristics of Tb-Dy-Fe alloys and then focuses on the research progress in recent years. First, studies on the crystal growth mechanism in directional solidification, process improvement by introducing a strong magnetic field and the effects of substitute elements are described. Then, meaningful progress in mechanical properties, composite materials, the structural origin of magnetostriction based on ferromagnetic MPB theory and sensor applications are summarized. Furthermore, sintered composite materials based on the reconstruction of the grain boundary phase also provide new ideas for the development of magnetostrictive materials with excellent comprehensive properties, including high magnetostriction, high mechanical properties, high corrosion resistance and high resistivity. Finally, future prospects are presented. This review will be helpful for the design of novel magnetostrictive Tb-Dy-Fe alloys, the improvement of magnetostrictive and mechanical properties and the understanding of magnetostriction mechanisms. Full article

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17 pages, 2846 KiB

Open AccessReview

Grain Boundary Diffusion Sources and Their Coating Methods for Nd-Fe-B Permanent Magnets

by Jiayi He, Jiali Cao, Zhigao Yu, Wenyue Song, Hongya Yu, Mozaffar Hussain and Zhongwu Liu

Metals 2021, 11(9), 1434; https://doi.org/10.3390/met11091434 - 10 Sep 2021

Cited by 19 | Viewed by 4466

Abstract

Nd-Fe-B magnets containing no heavy rare earth (HRE) elements exhibit insufficient coercivity to withstand the demagnetization field at elevated temperatures. The grain boundary diffusion (GBD) process provides the best route to fabricate high-coercive Nd-Fe-B magnets with low consumption of expensive HRE resources. Here [...] Read more.

Nd-Fe-B magnets containing no heavy rare earth (HRE) elements exhibit insufficient coercivity to withstand the demagnetization field at elevated temperatures. The grain boundary diffusion (GBD) process provides the best route to fabricate high-coercive Nd-Fe-B magnets with low consumption of expensive HRE resources. Here we give a special review on the grain boundary diffusion sources and their coating methods. Up to now, various types of grain boundary sources have been developed, starting from the earliest Tb or Dy metal. The HRE-M eutectic alloys were firstly proposed for reducing the cost of the diffusion source. After that, the diffusion sources based on light rare earth and even non rare earth elements have also been proposed, leading to new understanding of GBD. Now, the diffusion sources including inorganic compounds, metals, and alloys have been employed in the industry. At the same time, to coat the diffusion source on the magnets before diffusion treatment, various methods have been developed. Different from the previous review articles for GBD, this review gives an introduction of typical types of diffusion sources and their fabrication approaches. The effects of diffusion source on the microstructure and magnetic properties are summarized briefly. In particular, the principles and applicability of different coating approaches were discussed in detail. It is believed that this review can provide a technical guidance for the industry for designing the diffusion process and products meeting specific requirements. Full article

(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)

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