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Modeling and Characterization of Materials with Unique Magnetic, Electric and Mechanical Properties

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Materials Characterization".

Deadline for manuscript submissions: closed (20 April 2022) | Viewed by 31507

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Guest Editor
Department of Solid State Physics, Institute of Physics, University of Silesia, 75-Pułku Piechoty 1A, 40-500 Chorzów, Poland
Interests: magnetic and related properties of amorphous, nanocrystalline, and composite materials; solid state physics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Modern materials are a source of technology progress in many areas. There are well known applications in electronics, energetics (including the green technologies), motor and car industry.  For example, modern soft magnetic materials as a core of transformers or electric motors cause a significant increase of their energetic efficiency, saving energy in a global meaning. On the other hand, the hard magnetic materials are widely used in computer and energetic technologies as data storage media and high-efficiency electric generators, respectively. Between this two groups, one can observe a family of magnetic materials with excellent properties for broad application spectra (sensors, actuators, energy harvesting devices, magnetic refrigerators etc.). Other interesting property is electric transport in solids giving new conducting and semiconducting materials for modern electronic and computing machines. In this aspect, it is worth to mention topological insulators which sims to be a future for high efficiency electronic devices.

The progress in magnetic materials, not restricted to the mention above groups, would not be possible without basic science including technology, characterization and modeling in the atomic as well as large scale level. Such researches are useful for designing new systems with unique properties required for different applications.

The special issue entitled “Modeling and Characterization of Materials with Unique Magnetic, Electric and Mechanical Properties” refers to reviews and/or original research papers in the broad area of materials characterized by some unique features, leading to new application spectra.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are welcome.

Prof. Artur Chrobak
Guest Editor

Manuscript Submission Information

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Keywords

  • Magnetism
  • Magnetic materials
  • Electric transport
  • Electronic structure
  • Intermetallic compounds
  • Mechanical properties
  • Materials simulations

Published Papers (16 papers)

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9 pages, 3190 KiB  
Article
Effect of the Indentation Load on the Raman Spectra of the InP Crystal
by Dariusz Chrobak, Mateusz Dulski, Grzegorz Ziółkowski and Artur Chrobak
Materials 2022, 15(15), 5098; https://doi.org/10.3390/ma15155098 - 22 Jul 2022
Cited by 2 | Viewed by 1344
Abstract
Nanoindentations and the Raman spectroscopy measurements were carried out on the (001) surface of undoped and S-doped InP crystal. The samples were indented with the maximum load ranging from 15 mN to 100 mN. The phase transition B3→B1 was not confirmed by spectroscopic [...] Read more.
Nanoindentations and the Raman spectroscopy measurements were carried out on the (001) surface of undoped and S-doped InP crystal. The samples were indented with the maximum load ranging from 15 mN to 100 mN. The phase transition B3→B1 was not confirmed by spectroscopic experiments, indicating a plastic deformation mechanism governed by dislocations activity. Increasing the maximum indentation load shifts and the longitudinal and transverse optical Raman bands to lower frequencies reveals a reduction in the elastic energy stored in the plastic zone right below the indentation imprint. Mechanical experiments have shown that a shift in Raman bands occurs alongside the indentation size effect. Indeed, the hardness of undoped and S-doped InP crystal decreases as a function of the maximum indentation load. Full article
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11 pages, 906 KiB  
Article
Interatomic Potential for InP
by Dariusz Chrobak, Anna Majtyka-Piłat, Grzegorz Ziółkowski and Artur Chrobak
Materials 2022, 15(14), 4960; https://doi.org/10.3390/ma15144960 - 16 Jul 2022
Cited by 1 | Viewed by 1331
Abstract
Classical modeling of structural phenomena occurring in InP crystal, for example plastic deformation caused by contact force, requires an interatomic interaction potential that correctly describes not only the elastic properties of indium phosphide but also the pressure-induced reversible phase transition B3↔B1. In this [...] Read more.
Classical modeling of structural phenomena occurring in InP crystal, for example plastic deformation caused by contact force, requires an interatomic interaction potential that correctly describes not only the elastic properties of indium phosphide but also the pressure-induced reversible phase transition B3↔B1. In this article, a new parametrization of the analytical bond-order potential has been developed for InP. The potential reproduces fundamental physical properties (lattice parameters, cohesive energy, stiffness coefficients) of the B3 and B1 phases in good agreement with first-principles calculations. The proposed interaction model describes the reversibility of the pressure-induced B3↔B1 phase transition as well as the formation of native point defects in the B3 phase. Full article
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15 pages, 1334 KiB  
Article
Ironsand (Titanomagnetite-Titanohematite): Chemistry, Magnetic Properties and Direct Applications for Wireless Power Transfer
by Jérôme Leveneur, William J. Trompetter, Shen V. Chong, Ben Rumsey, Vedran Jovic, Seho Kim, Murray McCurdy, Emma Anquillare, Kevin E. Smith, Nick Long, John Kennedy, Grant Covic and John Boys
Materials 2021, 14(18), 5455; https://doi.org/10.3390/ma14185455 - 21 Sep 2021
Cited by 4 | Viewed by 2352
Abstract
Ironsand is an abundant and inexpensive magnetic mineral resource. However, the magnetic properties of unprocessed ironsand are often inadequate for any practical applications. In this work, the applicability of ironsand for use as a component in a soft magnetic composite for large-scale inductive [...] Read more.
Ironsand is an abundant and inexpensive magnetic mineral resource. However, the magnetic properties of unprocessed ironsand are often inadequate for any practical applications. In this work, the applicability of ironsand for use as a component in a soft magnetic composite for large-scale inductive power transfer applications was investigated. After magnetic separation, the chemical, structural and magnetic properties of ironsand sourced from different locations were compared. Differences observed in the DC magnetic properties were consistent with changes in the chemical compositions obtained from X-ray Absorption Near-Edge Spectroscopy (XANES), which suggests varying the titanohematite to titanomagnetite content. Increased content in titanomagnetite and magnetic permeability correlated well with the total Fe content in the materials. The best-performing ironsand with the highest permeability and lowest core losses was used alongside Mn,Zn-Ferrite particles (ranging from ∼100 μm to 2 mm) to fabricate toroid cores with varying magnetic material loading. It was shown that ironsand can be used to replace up to 15 wt.% of the magnetic materials with minimal impact on the composite magnetic performance, thus reducing the cost. Ironsand was also used as a supporting material in a single-rail wireless power transfer system, effectively increasing the power transfer, demonstrating potential applications to reduce flux leakage. Full article
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7 pages, 2785 KiB  
Article
On Incipient Plasticity of InP Crystal: A Molecular Dynamics Study
by Dariusz Chrobak, Grzegorz Ziółkowski and Artur Chrobak
Materials 2021, 14(15), 4157; https://doi.org/10.3390/ma14154157 - 26 Jul 2021
Cited by 2 | Viewed by 1525
Abstract
With classical molecular dynamics simulations, we demonstrated that doping of the InP crystal with Zn and S atoms reduces the pressure of the B3B1 phase transformation as well as inhibits the development of a dislocation structure. On this basis, [...] Read more.
With classical molecular dynamics simulations, we demonstrated that doping of the InP crystal with Zn and S atoms reduces the pressure of the B3B1 phase transformation as well as inhibits the development of a dislocation structure. On this basis, we propose a method for determining the phenomenon that initiates nanoscale plasticity in semiconductors. When applied to the outcomes of nanoindentation experiments, it predicts the dislocation origin of the elastic-plastic transition in InP crystal and the phase transformation origin of GaAs incipient plasticity. Full article
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15 pages, 3008 KiB  
Article
Study of the Structure, Magnetic, Thermal and Electrical Characterisation of ZnCr2Se4: Ta Single Crystals Obtained by Chemical Vapour Transport
by Izabela Jendrzejewska, Tadeusz Groń, Piotr Kwapuliński, Joachim Kusz, Ewa Pietrasik, Tomasz Goryczka, Bogdan Sawicki, Andrzej Ślebarski, Marcin Fijałkowski, Josef Jampilek and Henryk Duda
Materials 2021, 14(11), 2749; https://doi.org/10.3390/ma14112749 - 22 May 2021
Cited by 5 | Viewed by 1850
Abstract
The new series of single-crystalline chromium selenides, Ta-doped ZnCr2Se4, was synthesised by a chemical vapour transport method to determine the impact of a dopant on the structural and thermodynamic properties of the parent compound. We present comprehensive investigations of [...] Read more.
The new series of single-crystalline chromium selenides, Ta-doped ZnCr2Se4, was synthesised by a chemical vapour transport method to determine the impact of a dopant on the structural and thermodynamic properties of the parent compound. We present comprehensive investigations of structural, electrical transport, magnetic, and specific heat properties. It was expected that a partial replacement of Cr ions by a more significant Ta one would lead to a change in direct magnetic interactions between Cr magnetic moments and result in a change in the magnetic ground state and electric transport properties of the ZnCr2−xTaxSe4 (x = 0.05, 0.06, 0.07, 0.08, 0.1, 0.12) system. We found that all the elements of the cubic system had a cubic spinel structure; however, the doping gain linearly increased the ZnCr2−xTaxSe4 unit cell volume. Doping with tantalum did not significantly change the semiconductor and magnetic properties of ZnCr2Se4. For all studied samples (0 ≤ x ≤ 0.12), an antiferromagnetic order (AFM) below TN~22 K was observed. However, a small amount of Ta significantly reduced the second critical field (Hc2) from 65 kOe for x = 0.0 (ZnCr2Se4 matrix) up to 42.2 kOe for x = 0.12, above which the spin helical system changed to ferromagnetic (FM). The Hc2 reduction can lead to strong competition among AFM and FM interactions and spin frustration, as the specific heat under magnetic fields H < Hc2 shows a strong field decrease in TN. Full article
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11 pages, 10754 KiB  
Article
Enhancement of Hard Magnetic Properties in Fraktal-Like Nano and Mesoscopic Grains
by Grzegorz Ziółkowski, Dariusz Chrobak, Grażyna Chełkowska, Ondrej Zivotsky and Artur Chrobak
Materials 2021, 14(6), 1443; https://doi.org/10.3390/ma14061443 - 16 Mar 2021
Cited by 1 | Viewed by 1330
Abstract
The paper refers to Monte Carlo magnetic simulations for fractal-like nano and mesoscopic grains. The analyzed objects differed in the size, surface development, magnetic anisotropy and the spin values attributed to the system nodes inside the fractal. Such an approach allowed us to [...] Read more.
The paper refers to Monte Carlo magnetic simulations for fractal-like nano and mesoscopic grains. The analyzed objects differed in the size, surface development, magnetic anisotropy and the spin values attributed to the system nodes inside the fractal. Such an approach allowed us to determine their magnetization processes as well as optimization characteristics in the direction to enhancement of hard magnetic properties. As it was shown, the size effects depend on the chosen value of magnetic anisotropy. In the case of fractals with ultra-high coercivity, the decreasing of their size leads to deterioration of coercivity, especially for the high surface to volume ratio. Opposite effects were observed for soft magnetic fractals when the nanostructure caused an appearance of the coercive field, and the maximum of energy product was predictably significantly higher than for conventional rare earths’ free permanent magnets. Full article
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11 pages, 4343 KiB  
Article
Independently Tunable Multipurpose Absorber with Single Layer of Metal-Graphene Metamaterials
by Chen Han, Renbin Zhong, Zekun Liang, Long Yang, Zheng Fang, Yiqing Wang, Anchen Ma, Zhenhua Wu, Min Hu, Diwei Liu and Shenggang Liu
Materials 2021, 14(2), 284; https://doi.org/10.3390/ma14020284 - 8 Jan 2021
Cited by 6 | Viewed by 2309
Abstract
This paper reports an independently tunable graphene-based metamaterial absorber (GMA) designed by etching two cascaded resonators with dissimilar sizes in the unit cell. Two perfect absorption peaks were obtained at 6.94 and 10.68 μm with simple single-layer metal-graphene metamaterials; the peaks show absorption [...] Read more.
This paper reports an independently tunable graphene-based metamaterial absorber (GMA) designed by etching two cascaded resonators with dissimilar sizes in the unit cell. Two perfect absorption peaks were obtained at 6.94 and 10.68 μm with simple single-layer metal-graphene metamaterials; the peaks show absorption values higher than 99%. The mechanism of absorption was analyzed theoretically. The independent tunability of the metamaterial absorber (MA) was realized by varying the Fermi level of graphene under a set of resonators. Furthermore, multi-band and wide-band absorption were observed by the proposed structure upon increasing the number of resonators and resizing them in the unit cell. The obtained results demonstrate the multipurpose performance of this type of absorber and indicate its potential application in diverse applications, such as solar energy harvesting and thermal absorbing. Full article
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12 pages, 9193 KiB  
Article
Analysis of Magneto-Optical Hysteresis Loops of Amorphous and Surface-Crystalline Fe-Based Ribbons
by Ondřej Životský, Dmitry Markov, Kamila Hrabovská, Jiří Buršík and Yvonna Jirásková
Materials 2021, 14(1), 141; https://doi.org/10.3390/ma14010141 - 31 Dec 2020
Cited by 3 | Viewed by 1969
Abstract
Three Fe-based ribbon-type samples prepared by a conventional planar flow casting process are studied from the viewpoint of the amorphous Fe80Si4B16 and partially surface crystallized Fe80Si10B10, and Fe80.5Nb6.9B [...] Read more.
Three Fe-based ribbon-type samples prepared by a conventional planar flow casting process are studied from the viewpoint of the amorphous Fe80Si4B16 and partially surface crystallized Fe80Si10B10, and Fe80.5Nb6.9B12.6, microstructures. Surface magnetic properties are investigated by magneto-optical Kerr microscopy, allowing the measurement of a local hysteresis loop from a selected area on the ribbon surface, and simultaneously, a domain structure corresponding to a definite point at the loop. For an amorphous sample, the changes in the slopes of hysteresis loops are related either to the size of the selected surface area, from which the loop is measured, or to the type, width, and movement of magnetic domains through this area. In the first case, the resizing of the area simulates an effect of changing the diameter of the incident laser beam on the magneto-optical properties of the ribbon. In the latter case, the observed wide-curved and fingerprint domains are responsible for markedly different shapes of the hysteresis loops at lower magnetic fields. If the surface is crystallized, the magnetic properties are more homogenous, showing typical one-jump magnetization reversal with less dependence on the size of the surface area. The magneto-optical experiments are completed by transmission electron microscopy and magnetic force microscopy. Full article
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14 pages, 6851 KiB  
Article
Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound
by Marcin Sikora, Anna Bajorek, Artur Chrobak, Józef Deniszczyk, Grzegorz Ziółkowski and Grażyna Chełkowska
Materials 2020, 13(23), 5481; https://doi.org/10.3390/ma13235481 - 1 Dec 2020
Cited by 3 | Viewed by 1870
Abstract
We report on the comprehensive experimental and theoretical studies of magnetic and electronic structural properties of the Gd0.4Tb0.6Co2 compound crystallization in the cubic Laves phase (C15). We present new results and compare them to those reported earlier. The [...] Read more.
We report on the comprehensive experimental and theoretical studies of magnetic and electronic structural properties of the Gd0.4Tb0.6Co2 compound crystallization in the cubic Laves phase (C15). We present new results and compare them to those reported earlier. The magnetic study was completed with electronic structure investigations. Based on magnetic isotherms, magnetic entropy change (ΔSM) was determined for many values of the magnetic field change (Δμ0H), which varied from 0.1 to 7 T. In each case, the ΔSM had a maximum around room temperature. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that the compound undergoes a magnetic phase transition of the second type. From the M(T) dependency, the exchange integrals between rare-earth R-R (JRR), R-Co (JRCo), and Co-Co (JCoCo) atoms were evaluated within the mean-field theory approach. The electronic structure was determined using the X-ray photoelectron spectroscopy (XPS) method as well as by calculations using the density functional theory (DFT) based Full Potential Linearized Augmented Plane Waves (FP-LAPW) method. The comparison of results of ab initio calculations with the experimental data indicates that near TC the XPS spectrum collects excitations of electrons from Co3d states with different values of exchange splitting. The values of the magnetic moment on Co atoms determined from magnetic measurements, estimated from the XPS spectra, and results from ab initio calculations are quantitatively consistent. Full article
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17 pages, 20043 KiB  
Article
Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)z Permanent Magnets: II. Composition, Magnetization Reversal, and Magnetic Hardening of Main Structural Components
by Andrey G. Dormidontov, Natalia B. Kolchugina, Nikolay A. Dormidontov, Yury V. Milov and Alexander S. Andreenko
Materials 2020, 13(23), 5426; https://doi.org/10.3390/ma13235426 - 28 Nov 2020
Cited by 6 | Viewed by 1813
Abstract
Experimental series of alloys for (Sm,Zr)(Co,Cu,Fe)Z permanent magnets are presented in the concentration ranges that provide wide variations of (4f)/(4d)/(3d) ratios of comprising elements. Optical metallographic analysis, observation of the surface domain structure upon magnetization reversal [...] Read more.
Experimental series of alloys for (Sm,Zr)(Co,Cu,Fe)Z permanent magnets are presented in the concentration ranges that provide wide variations of (4f)/(4d)/(3d) ratios of comprising elements. Optical metallographic analysis, observation of the surface domain structure upon magnetization reversal (Kerr effect), electron microprobe analysis, and measuring the major hysteresis loops of samples at different stages of heat treatment are used to study processes related to the development of the highly coercive state of these samples. It was found that the volume fractions of two main structural components A and B, which comprise 90% of the total sample volume, rigorously control the coercivity at all stages of thermal aging. At the same time, structural components A and B themselves in samples being in the high-coercivity state differ qualitatively and quantitatively in the chemical composition, domain structure and its development in external magnetic fields and, therefore, are characterized by different morphologies of the phases comprising the structural components. Two stages of phase transformations in the sample structure are observed. During isothermal annealing, the cellular structure develops within the B component, whereas, during stepwise (slow) cooling or quenching from the isothermal aging temperature to 400 °C, a phase structure evolves within both the cell boundaries in B and the structural component A. The degree of completion of the phase transformations within micro- and nano-volumes of the components determines the ultimate hysteretic characteristics of the material. Full article
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18 pages, 5989 KiB  
Article
Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)Z Permanent Magnets: First Level of Heterogeneity
by Andrey G. Dormidontov, Natalia B. Kolchugina, Nikolay A. Dormidontov and Yury V. Milov
Materials 2020, 13(17), 3893; https://doi.org/10.3390/ma13173893 - 3 Sep 2020
Cited by 8 | Viewed by 2587
Abstract
An original vision for the structural formation of (Sm,Zr)(Co,Cu,Fe)Z alloys, the compositions of which show promise for manufacturing high-coercivity permanent magnets, is reported. Foundations arising from the quantitative analysis of alloy microstructures as the first, coarse, level of heterogeneity are considered. The [...] Read more.
An original vision for the structural formation of (Sm,Zr)(Co,Cu,Fe)Z alloys, the compositions of which show promise for manufacturing high-coercivity permanent magnets, is reported. Foundations arising from the quantitative analysis of alloy microstructures as the first, coarse, level of heterogeneity are considered. The structure of the alloys, in optical resolutions, is shown to be characterized by three structural phase components, which are denoted as A, B, and C and based on the 1:5, 2:17, and 2:7 phases, respectively. As the chemical composition of alloys changes monotonically, the quantitative relationships of the components A, B, and C vary over wide ranges. In this case, the hysteretic properties of the (Sm,Zr)(Co,Cu,Fe)Z alloys in the high-coercivity state are strictly controlled by the volume fractions of the A and B structural components. Based on quantitative relationships of the A, B, and C structural components for the (R,Zr)(Co,Cu,Fe)Z alloys with R = Gd or Sm, sketches of quasi-ternary sections of the (Co,Cu,Fe)-R-Zr phase diagrams at temperatures of 1160–1190 °C and isopleths for the 2:17–2:7 phase composition range of the (Co,Cu,Fe)–Sm–Zr system were constructed. Full article
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11 pages, 5685 KiB  
Article
From Atomic Level to Large-Scale Monte Carlo Magnetic Simulations
by Artur Chrobak, Grzegorz Ziółkowski, Dariusz Chrobak and Grażyna Chełkowska
Materials 2020, 13(17), 3696; https://doi.org/10.3390/ma13173696 - 21 Aug 2020
Cited by 4 | Viewed by 2296
Abstract
This paper refers to Monte Carlo magnetic simulations for large-scale systems. We propose scaling rules to facilitate analysis of mesoscopic objects using a relatively small amount of system nodes. In our model, each node represents a volume defined by an enlargement factor. As [...] Read more.
This paper refers to Monte Carlo magnetic simulations for large-scale systems. We propose scaling rules to facilitate analysis of mesoscopic objects using a relatively small amount of system nodes. In our model, each node represents a volume defined by an enlargement factor. As a consequence of this approach, the parameters describing magnetic interactions on the atomic level should also be re-scaled, taking into account the detailed thermodynamic balance as well as energetic equivalence between the real and re-scaled systems. Accuracy and efficiency of the model have been depicted through analysis of the size effects of magnetic moment configuration for various characteristic objects. As shown, the proposed scaling rules, applied to the disorder-based cluster Monte Carlo algorithm, can be considered suitable tools for designing new magnetic materials and a way to include low-level or first principle calculations in finite element Monte Carlo magnetic simulations. Full article
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10 pages, 3454 KiB  
Article
Blending Powder Process for Recycling Sintered Nd-Fe-B Magnets
by Pavel A. Prokofev, Natalia B. Kolchugina, Katerina Skotnicova, Gennady S. Burkhanov, Miroslav Kursa, Mark V. Zheleznyi, Nikolay A. Dormidontov, Tomas Cegan, Anna S. Bakulina, Yurii S. Koshkidko and Bedřich Smetana
Materials 2020, 13(14), 3049; https://doi.org/10.3390/ma13143049 - 8 Jul 2020
Cited by 12 | Viewed by 2228
Abstract
The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets [...] Read more.
The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment. Full article
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13 pages, 4230 KiB  
Article
New Constitutive Model for the Size Effect on Flow Stress Based on the Energy Conservation Law
by Chuanjie Wang, Haiyang Wang, Gang Chen, Qiang Zhu, Lingjiang Cui, Peng Zhang and Anping Dong
Materials 2020, 13(11), 2617; https://doi.org/10.3390/ma13112617 - 8 Jun 2020
Cited by 4 | Viewed by 2267
Abstract
In this study, a new model involving energy is established to characterize the size effect on flow stress. The new model treats the experimental machine and the specimen as an isolated system, and this isolated system satisfies the Energy Conservation Law. The total [...] Read more.
In this study, a new model involving energy is established to characterize the size effect on flow stress. The new model treats the experimental machine and the specimen as an isolated system, and this isolated system satisfies the Energy Conservation Law. The total work performed on the specimen by the experimental machine is nearly equal to the energy consumed by the specimen plastic deformation and the energy consumed by friction (which can be ignored when working without friction). The new model predicts the energy consumption of the specimen deformation by quantifying the total energy input to the specimen by the experimental machine and then obtaining the relevant parameters of the constitutive model. Through uniaxial tensile tests of pure nickel thin sheets with various thickness/average grain sizes (t/d), the new model was used to optimize the parameters of the existing constitutive model that predicts the flow stress of specimens with different t/d. The prediction accuracy of the optimized constitutive model is improved, especially for specimens with a t/d < 1. The new model is established from the perspective of energy input to avoid the analysis of the material deformation mechanism and improve the prediction accuracy. Full article
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11 pages, 2691 KiB  
Article
Mixed Valence of Ce and Its Consequences on the Magnetic State of Ce9Ru4Ga5: Electronic Structure Studies
by Andrzej Ślebarski, Józef Deniszczyk and Dariusz Kaczorowski
Materials 2020, 13(10), 2377; https://doi.org/10.3390/ma13102377 - 21 May 2020
Cited by 4 | Viewed by 2140
Abstract
We report on X-ray photoelectron spectroscopy (XPS) and ab initio electronic structure investigations of a novel intermetallic material Ce 9 Ru 4 Ga 5 . The compound crystallizes with a tetragonal unit cell (space group I4 m m ) that contains three inequivalent [...] Read more.
We report on X-ray photoelectron spectroscopy (XPS) and ab initio electronic structure investigations of a novel intermetallic material Ce 9 Ru 4 Ga 5 . The compound crystallizes with a tetragonal unit cell (space group I4 m m ) that contains three inequivalent Ce atoms sites. The Ce 3 d core level XPS spectra indicated an intermediate valence (IV) of selected Ce ions, in line with the previously reported thermodynamic and spectroscopic data. The ab initio calculations revealed that Ce1 ions located at 2 a Wyckoff positions possess stable trivalent configuration, whereas Ce2 ions that occupy 8 d site are intermediate valent. Moreover, for Ce3 ions, located at different 8 d position, a fractional valence was found. The results are discussed in terms of on-site and intersite hybridization effects. Full article
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16 pages, 4330 KiB  
Perspective
High and Ultra-High Coercive Materials in Spring-Exchange Systems—Review, Simulations and Perspective
by Artur Chrobak
Materials 2022, 15(19), 6506; https://doi.org/10.3390/ma15196506 - 20 Sep 2022
Cited by 6 | Viewed by 1400
Abstract
The paper refers to the spring-exchange magnetic systems containing magnetically soft and hard phases. This work consists of two parts. The first part is a brief review of hard magnetic materials, with special attention paid to ultra-high coercive compounds, as well as selected [...] Read more.
The paper refers to the spring-exchange magnetic systems containing magnetically soft and hard phases. This work consists of two parts. The first part is a brief review of hard magnetic materials, with special attention paid to ultra-high coercive compounds, as well as selected spring-exchange systems. The second part is a theoretical discussion based on the Monte Carlo micromagnetic simulations about the possible enhancement of the hard magnetic properties of systems composed of magnetically soft, as well as high and ultra-high coercive, phases. As shown, the analyzed systems reveal the potential for improving the |BH|max parameter, filling the gap between conventional and Nd-based permanent magnets. Moreover, the carried-out simulations indicate the advantages and limitations of the spring-exchange composites, which could lead to a reduction in rare earth elements in permanent magnet applications. Full article
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