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13 pages, 10904 KiB

Open AccessArticle

Effect of High-Energy Ball Milling in Ternary Material System of (Mg-Sn-Na)

by Halit Sübütay and İlyas Şavklıyıldız

Crystals 2023, 13(8), 1230; https://doi.org/10.3390/cryst13081230 - 9 Aug 2023

Cited by 5 | Viewed by 1280

Abstract

In this study, the nature of the ball-milling mechanism in a ternary materials system (Mg-6Sn-1Na) is investigated for proper mechanical alloying. An identical powder mixture for this material system is exposed to different milling durations for a suitable mixture. First, the platelet structure [...] Read more.

In this study, the nature of the ball-milling mechanism in a ternary materials system (Mg-6Sn-1Na) is investigated for proper mechanical alloying. An identical powder mixture for this material system is exposed to different milling durations for a suitable mixture. First, the platelet structure formation is observed on particles with increasing milling duration, mainly formed in <200> direction of the hexagonal crystal structure of the Mg matrix. Then, the flake structure with texture formation is broken into smaller spherical particles with further ball milling up to 12 h. According to EDS analysis, the secondary phases in the Mg matrix are homogenously distributed with a 12-h milling duration which advises a proper mixture in this material system. The solid solution formation is triggered with an 8-h milling duration according to XRD analysis on 101 reflections. Conventional sintering is performed at 350 °C in 2 h for each sample. In bulk samples, XRD data reveal that secondary phases (Mg₂Sn) with island-like structures are formed on the Mg matrix for a milling duration of up to 8 h. These bigger secondary phases are mainly constituted as Mg₂Sn intermetallic forms, which have a negative effect on physical and mechanical properties due to a mismatch in the grain boundary formation. However, the homogenous distribution of secondary phases with a smaller particle size distribution, acquired with 12 h milling time, provides the highest density, modulus of elasticity, and hardness values for this ternary materials system. The ternary materials produced with the 12-h ball-milling process provide an improvement of about 117% in hardness value compared with the cast form. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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11 pages, 3937 KiB

Open AccessArticle

Room and Elevated Temperature Sliding Friction and Wear Behavior of Al_0.3CoFeCrNi and Al_0.3CuFeCrNi₂ High Entropy Alloys

by Dheyaa F. Kadhim, Manindra V. Koricherla and Thomas W. Scharf

Crystals 2023, 13(4), 609; https://doi.org/10.3390/cryst13040609 - 2 Apr 2023

Cited by 3 | Viewed by 1687

Abstract

In this study, processing–structure–property relations were systematically investigated at room and elevated temperatures for two FCC Al_0.3CoFeCrNi and Al_0.3CuFeCrNi₂ high-entropy alloys (HEAs), also known as complex concentrated alloys (CCAs), prepared by conventional arc-melting. It was determined that both [...] Read more.

In this study, processing–structure–property relations were systematically investigated at room and elevated temperatures for two FCC Al_0.3CoFeCrNi and Al_0.3CuFeCrNi₂ high-entropy alloys (HEAs), also known as complex concentrated alloys (CCAs), prepared by conventional arc-melting. It was determined that both alloys exhibit FCC single-phase solid solution structure. Micro-indentation and sliding wear tests were performed to study the hardness and tribological behavior and mechanisms at room and elevated temperatures. During room-temperature sliding, both alloys exhibit similar friction behavior, with an average steady-state coefficient of friction (COF) of ~0.8. Upon increasing sliding temperatures to 300 °C, the average COF decreased to a lowest value of ~0.3 for Al_0.3CuFeCrNi₂. Mechanistic wear studies showed this was due to the low interfacial shear strength tribofilms formed inside the wear tracks. Raman spectroscopy and energy dispersive spectroscopy determined the tribofilms were predominantly composed of binary oxides and multi-element solid solution oxides. While the tribofilms at elevated temperatures lowered the COF values, the respective wear rates in both alloys were higher compared to room-temperature sliding, due to thermal softening during 300 °C sliding. Thus, these single FCC-phase HEAs provide no further benefit in wear resistance at elevated temperatures, and likely will have similar implications for other single FCC-phase HEAs. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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11 pages, 2492 KiB

Open AccessArticle

The Effect of Cr Additive on the Mechanical Properties of Ti-Al Intermetallics by First-Principles Calculations

by Hui Wang, Fuyong Su and Zhi Wen

Crystals 2023, 13(3), 488; https://doi.org/10.3390/cryst13030488 - 11 Mar 2023

Cited by 1 | Viewed by 1445

Abstract

The structure, elastic properties and electronic structure of Ti-Al intermetallics including Ti₃Al (space group P63/mmc), TiAl (space group I4/mmm) and TiAl₃ (space group P4/mmm) are systematically studied by first-principles calculations. The results show that Ti-Al intermetallics can exist stably whether [...] Read more.

The structure, elastic properties and electronic structure of Ti-Al intermetallics including Ti₃Al (space group P63/mmc), TiAl (space group I4/mmm) and TiAl₃ (space group P4/mmm) are systematically studied by first-principles calculations. The results show that Ti-Al intermetallics can exist stably whether Cr replaces Ti or Al. The ductility of the alloy cannot be improved when Ti is replaced in Cr-doped TiAl and TiAl₃. However, when it replaces Al, the alloy has better ductility. In Ti₃Al, the ductility can be improved regardless of whether Cr replaces Ti or Al, and the effect is better when it replaces Al. The bond in Ti-Al intermetallics is mainly a Ti-Ti metal bond. The metal bond between Ti-Ti is strengthened and a solid metal bond is formed between Cr and Ti, inducing a better ductility of the material, after Cr replaces Al in Ti-Al intermetallics. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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10 pages, 404 KiB

Open AccessArticle

Ginzburg–Landau Analysis on the Physical Properties of the Kagome Superconductor CsV₃Sb₅

by Tianyi Han, Jiantao Che, Chenxiao Ye and Hai Huang

Crystals 2023, 13(2), 321; https://doi.org/10.3390/cryst13020321 - 15 Feb 2023

Cited by 3 | Viewed by 1871

Abstract

The kagome lattice consisting of corner-sharing triangles has been studied in the context of quantum physics for more than seventy years. For the novel discovered kagome superconductor CsV

_{3}

Sb

_{5}

, identifying the pairing symmetry of order parameter remained an elusive problem [...] Read more.

The kagome lattice consisting of corner-sharing triangles has been studied in the context of quantum physics for more than seventy years. For the novel discovered kagome superconductor CsV

_{3}

Sb

_{5}

, identifying the pairing symmetry of order parameter remained an elusive problem until now. Based on the two-band Ginzburg–Landau theory, we study the temperature dependence of upper critical field and magnetic penetration depth for this compound. All theoretical results are consistent with the experimental data, which strongly indicates the existence of two-gap s-wave superconductivity in this system. In addition, it is worth noting that the anisotropy of effective masses in the band with large (or small) gap is about 70 (or 2.4). With the calculation of the Kadowaki–Woods ratio as

0.58 \times 10^{- 5}

μ Ω cm {mol}^{2} K^{2} {mJ}^{- 2}

, the semi-heavy-fermion feature is suggested in the compound CsV

_{3}

Sb

_{5}

. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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12 pages, 5253 KiB

Open AccessArticle

Direct Evidence for Phase Transition Process of VC Precipitation from (Fe,V)₃C in Low-Temperature V-Bearing Molten Iron

by Lei Cao, Desheng Chen, Xiaomeng Sang, Hongxin Zhao, Yulan Zhen, Lina Wang, Yahui Liu, Fancheng Meng and Tao Qi

Crystals 2023, 13(2), 175; https://doi.org/10.3390/cryst13020175 - 19 Jan 2023

Viewed by 1584

Abstract

V-bearing molten iron was obtained by adding Na₂CO₃ in the smelting process of vanadium titanomagnetite at low temperature. Two forms of V-rich carbides ((Fe,V)₃C, VC) were detected in the V-bearing pig iron products. Once the smelting temperature was [...] Read more.

V-bearing molten iron was obtained by adding Na₂CO₃ in the smelting process of vanadium titanomagnetite at low temperature. Two forms of V-rich carbides ((Fe,V)₃C, VC) were detected in the V-bearing pig iron products. Once the smelting temperature was above 1300 °C, most of the V in the raw ore was reduced into molten iron. Owning to the high content of V, the unsteady (Fe,V)₃C solid solution decomposed along with the precipitation of graphite and VC during the solidification process. The presence of VC cluster and VC precursor in (Fe,V)₃C was detected by transmission electron microscopy, which confirmed the possibility of this transition process at the atomic perspective. The transformation dramatically affected the compositions and properties of V-bearing pig iron and had important guiding significance for the actual production process. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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13 pages, 3015 KiB

Open AccessArticle

GPU-Based Cellular Automata Model for Multi-Orient Dendrite Growth and the Application on Binary Alloy

by Jingjing Wang, Hongji Meng, Jian Yang and Zhi Xie

Crystals 2023, 13(1), 105; https://doi.org/10.3390/cryst13010105 - 6 Jan 2023

Cited by 1 | Viewed by 1779

Abstract

To simulate dendrite growth with different orientations more efficiently, a high-performance cellular automata (CA) model based on heterogenous central processing unit (CPU)+ graphics processing unit (GPU) architecture has been proposed in this paper. Firstly, the decentered square algorithm (DCSA) is used to simulate [...] Read more.

To simulate dendrite growth with different orientations more efficiently, a high-performance cellular automata (CA) model based on heterogenous central processing unit (CPU)+ graphics processing unit (GPU) architecture has been proposed in this paper. Firstly, the decentered square algorithm (DCSA) is used to simulate the morphology of dendrite with different orientations. Secondly, parallel algorithms are proposed to take full advantage of many cores by maximizing computational parallelism. Thirdly, in order to further improve the calculation efficiency, the task scheduling scheme using multi-stream is designed to solve the waiting problem among independent tasks, improving task parallelism. Then, the present model was validated by comparing its steady dendrite tip velocity with the Lipton–Glicksman–Kurz (LGK) analytical model, which shows great agreement. Finally, it is applied to simulate the dendrite growth of the binary alloy, which proves that the present model can not only simulate the clear dendrite morphology with different orientations and secondary arms, but also show a good agreement with the in situ experiment. In addition, compared with the traditional CPU model, the speedup of this model is up to 158×, which provides a great acceleration. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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7 pages, 1668 KiB

Open AccessArticle

First-Principles Calculations of Structural and Mechanical Properties of Cu–Ni Alloys

by Yun Wei, Ben Niu, Qijun Liu, Zhengtang Liu and Chenglu Jiang

Crystals 2023, 13(1), 43; https://doi.org/10.3390/cryst13010043 - 26 Dec 2022

Cited by 8 | Viewed by 2352

Abstract

Nanostructured Cu–Ni alloys have become the focus of public attention due to their better corrosion resistance and high hardness in experimental measurements. First-principles calculation based on the density functional theory (DFT) has been confirmed as an effective tool and used to illustrate the [...] Read more.

Nanostructured Cu–Ni alloys have become the focus of public attention due to their better corrosion resistance and high hardness in experimental measurements. First-principles calculation based on the density functional theory (DFT) has been confirmed as an effective tool and used to illustrate the mechanical properties of these alloys. In this paper, the DFT has been employed to calculate the mechanical properties of Cu–Ni alloys, including bulk modulus, shear modulus, Young’s modulus, anisotropic index, Poisson’s ratio, average velocity, and B/G. We find that the Ni-rich Cu–Ni alloys have relatively higher mechanical parameters, and the Cu-rich alloys have smaller mechanical parameters, which is consistent with previous experiments. This provides an idea for us to design alloys to improve alloy strength. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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9 pages, 324 KiB

Open AccessArticle

Boundary Effect and Critical Temperature of Two-Band Superconducting FeSe Films

by Chenxiao Ye, Jiantao Che and Hai Huang

Crystals 2023, 13(1), 18; https://doi.org/10.3390/cryst13010018 - 22 Dec 2022

Viewed by 1594

Abstract

Based on two-band Bogoliubov–de Gennes theory, we study the boundary effect of an interface between a two-gap superconductor FeSe and insulator (or vacuum). New boundary terms are introduced into two-band Ginzburg–Landau formalism, which modifies the boundary conditions for the corresponding order parameters of [...] Read more.

Based on two-band Bogoliubov–de Gennes theory, we study the boundary effect of an interface between a two-gap superconductor FeSe and insulator (or vacuum). New boundary terms are introduced into two-band Ginzburg–Landau formalism, which modifies the boundary conditions for the corresponding order parameters of superconductor. The theory allows for a mean-field calculation of the critical temperature suppression with the decrease in FeSe film thickness. Our numerical results are in good agreement with the experimental data observed in this material. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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12 pages, 7469 KiB

Open AccessArticle

Hyperbolic Behavior and Antiferromagnetic Order in Rare-Earth Tellurides

by Jonathan Gjerde and Radi A. Jishi

Crystals 2022, 12(12), 1839; https://doi.org/10.3390/cryst12121839 - 16 Dec 2022

Cited by 4 | Viewed by 2161

Abstract

Quasi-2D materials have received much attention in recent years for their unusual physical properties. Among the most investigated of these materials are the rare-earth tellurides, which are primarily studied because they exhibit charge density waves and other quantum phenomena and have a high [...] Read more.

Quasi-2D materials have received much attention in recent years for their unusual physical properties. Among the most investigated of these materials are the rare-earth tellurides, which are primarily studied because they exhibit charge density waves and other quantum phenomena and have a high degree of tunability. In this paper, we examine the optical and magnetic properties of several rare-earth tellurides and find that they are antiferromagnetic materials with hyperbolic dispersion. Hyperbolic materials have very promising applications in sub-diffraction-limit optics, nanolithography, and spontaneous emission engineering, but these applications are hampered by low-quality hyperbolic materials. Rare-earth tellurides may provide insight into solving these issues if their properties can be properly tuned using the large variety of techniques already explored in the literature. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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10 pages, 8368 KiB

Open AccessArticle

Dewetting Process in Ni-Mn-Ga Shape-Memory Heusler: Effects on Morphology, Stoichiometry and Magnetic Properties

by Milad Takhsha Ghahfarokhi, Federica Celegato, Gabriele Barrera, Francesca Casoli, Paola Tiberto and Franca Albertini

Crystals 2022, 12(12), 1826; https://doi.org/10.3390/cryst12121826 - 15 Dec 2022

Viewed by 1549

Abstract

In this work, dewetting process has been investigated in shape-memory Heuslers. To this aim, series of high-temperature annealing (1100–1150 K) have been performed at high vacuum (time is varied in the range of 55–165 min) in Ni-Mn-Ga epitaxial thin films grown on MgO(001). [...] Read more.

In this work, dewetting process has been investigated in shape-memory Heuslers. To this aim, series of high-temperature annealing (1100–1150 K) have been performed at high vacuum (time is varied in the range of 55–165 min) in Ni-Mn-Ga epitaxial thin films grown on MgO(001). The process kinetics have been followed by studying the evolution of morphology and composition. In particular, we report the initiation of the dewetting process by the formation of symmetric holes in the films. The holes propagate and integrate, leaving micrometric and submicron islands of the material, increasing the average roughness of the films by a factor of up to around 30. The dewetting process is accompanied by severe Ga and Mn sublimation, and Ni-Ga segregation, which significantly modify the magnetic properties of the films measured at each stage. The annealed samples show a relatively weak magnetic signal at room temperature with respect to the pristine sample. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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20 pages, 11517 KiB

Open AccessArticle

The Presence of Charge Transfer Defect Complexes in Intermediate Band CuAl_1−pFe_pS₂

by Christopher Dickens, Adam O. J. Kinsella, Matt Watkins and Matthew Booth

Crystals 2022, 12(12), 1823; https://doi.org/10.3390/cryst12121823 - 14 Dec 2022

Viewed by 1667

Abstract

Despite chalcopyrite (CuFeS

_{2}

) being one of the oldest known copper ores, it exhibits various properties that are still the subject of debate. For example, the relative concentrations of the ionic states of Fe and Cu in CuFeS

_{2}

can vary significantly [...] Read more.

Despite chalcopyrite (CuFeS

_{2}

) being one of the oldest known copper ores, it exhibits various properties that are still the subject of debate. For example, the relative concentrations of the ionic states of Fe and Cu in CuFeS

_{2}

can vary significantly between different studies. The presence of a plasmon-like resonance in the visible absorption spectrum of CuFeS

_{2}

nanocrystals has driven a renewed interest in this material over recent years. The successful synthesis of CuAl

_{1 - p}

Fe

_{p}

S

_{2}

nanocrystals that exhibit a similar optical resonance has recently been demonstrated in the literature. In this study, we use density functional theory to investigate Fe substitution in CuAlS

_{2}

and find that the formation energy of neutral

{[{Fe}_{Cu}]}^{2 +} + {[{Cu}_{Al}]}^{2 -}

defect complexes is comparable to

{[{Fe}_{Al}]}^{0}

antisites when

p \geq 0.5

. Analysis of electron density and density of states reveals that charge transfer within these defect complexes leads to the formation of local Cu

^{2 +}

/Fe

^{2 +}

ionic states that have previously been associated with the optical resonance in the visible absorption of CuFeS

_{2}

. Finally, we comment on the nature of the optical resonance in CuAl

_{1 - p}

Fe

_{p}

S

_{2}

in light of our results and discuss the potential for tuning the optical properties of similar systems. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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10 pages, 2173 KiB

Open AccessArticle

Investigation of Magnetocaloric Properties in the TbCo₂-H System

by Galina Politova, Irina Tereshina, Ioulia Ovchenkova, Abdu-Rahman Aleroev, Yurii Koshkid’ko, Jacek Ćwik and Henryk Drulis

Crystals 2022, 12(12), 1783; https://doi.org/10.3390/cryst12121783 - 8 Dec 2022

Cited by 3 | Viewed by 1483

Abstract

In this work the magnetocaloric effect in the TbCo₂-H system in the region of the Curie temperature was studied both by direct and indirect methods in external magnetic fields up to ~1.4 and 14 T, respectively. We have paid special attention [...] Read more.

In this work the magnetocaloric effect in the TbCo₂-H system in the region of the Curie temperature was studied both by direct and indirect methods in external magnetic fields up to ~1.4 and 14 T, respectively. We have paid special attention to the magnetic and magnetothermal properties of the TbCo₂–H with high hydrogen content. The mechanisms responsible for the change in the Curie temperature were established, and the field and temperature dependences of the magnetocaloric effect were analyzed in detail. In addition, the magnetocaloric properties (including critical parameters) for various systems based on the TbCo₂ compound were compared. The main regularities of the change in the MCE value and the Curie temperature depending on the composition are discovered and discussed. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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28 pages, 18274 KiB

Open AccessArticle

Hydrogen-Induced Order–Disorder Effects in FePd₃

by André Götze, Siobhan Christina Stevenson, Thomas Christian Hansen and Holger Kohlmann

Crystals 2022, 12(12), 1704; https://doi.org/10.3390/cryst12121704 - 24 Nov 2022

Cited by 4 | Viewed by 1615

Abstract

Binary intermetallic compounds, such as FePd₃, attract interests due to their physical, magnetic and catalytic properties. For a better understanding of their hydrogenation properties, both ordered FePd₃ and disordered Fe_0.25Pd_0.75 are studied by several in situ methods, [...] Read more.

Binary intermetallic compounds, such as FePd₃, attract interests due to their physical, magnetic and catalytic properties. For a better understanding of their hydrogenation properties, both ordered FePd₃ and disordered Fe_0.25Pd_0.75 are studied by several in situ methods, such as thermal analysis, X-ray powder diffraction and neutron powder diffraction, at moderate hydrogen pressures up to 8.0 MPa. FePd₃ absorbs small amounts of hydrogen at room temperature and follows Sieverts’ law of hydrogen solubility in metals. [Pd₆] octahedral voids are filled up to 4.7(9)% in a statistical manner at 8.00(2) MPa, yielding the hydride FePd₃H_0.047(9). This is accompanied by decreasing long-range order of Fe and Pd atoms (site occupancy factor of Fe at Wyckoff position 1a decreasing from 0.875(3) to 0.794(4)). This trend is also observed during heating, while the ordered magnetic moment decreases up to the Curie temperature of 495(8) K. The temperature dependences of the magnetic moments of iron atoms in FePd₃ under isobaric conditions (p(D₂) = 8.2(2) MPa) are consistent with a 3D Ising or Heisenberg model (critical parameter β = 0.28(5)). The atomic and magnetic order and hydrogen content of FePd₃ show a complex interplay. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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8 pages, 1190 KiB

Open AccessArticle

Field-Induced Transition in (Nd,Dy)₂Fe₁₄B in Ultrahigh Magnetic Fields

by N. V. Kostyuchenko, I. S. Tereshina, A. I. Bykov, S. V. Galanova, R. V. Kozabaranov, A. S. Korshunov, I. S. Strelkov, I. V. Makarov, A. V. Filippov, Yu. B. Kudasov, D. A. Maslov, V. V. Platonov, O. M. Surdin, P. B. Repin, V. D. Selemir and A. K. Zvezdin

Crystals 2022, 12(11), 1615; https://doi.org/10.3390/cryst12111615 - 11 Nov 2022

Viewed by 1342

Abstract

We demonstrate the peculiarities of the magnetization process in the ferrimagnetic intermetallic compound (Nd_0.5Dy_0.5)₂Fe₁₄B, which has been studied theoretically and experimentally using ultrahigh magnetic fields. We observe phase transition induced by external ultrahigh magnetic fields [...] Read more.

We demonstrate the peculiarities of the magnetization process in the ferrimagnetic intermetallic compound (Nd_0.5Dy_0.5)₂Fe₁₄B, which has been studied theoretically and experimentally using ultrahigh magnetic fields. We observe phase transition induced by external ultrahigh magnetic fields (up to 170 T) and also describe the magnetization process analytically in terms of critical transition fields. In this work, the first and second critical fields of the field-induced magnetic transitions, H_c1 and H_c2, were estimated, and the results were verified against experimental data for H_c1. Critical field H_c2 predicting the place of transition to the forced-ferromagnetic state was estimated for the first time for (Nd_0.5Dy_0.5)₂Fe₁₄B compound. A comparison of the magnetization behavior for (Nd_0.5Dy_0.5)₂Fe₁₄B with the basic systems Nd₂Fe₁₄B and Dy₂Fe₁₄B is also performed. We demonstrate that, in the Dy₂Fe₁₄B compound, the field-induced transition type is changed from the first to the second order due to the replacement of the Nd atom by Dy one. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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21 pages, 5864 KiB

Open AccessArticle

The Structural, Electronic, Magnetic and Elastic Properties of Full-Heusler Co₂CrAl and Cr₂MnSb: An Ab Initio Study

by Sara J. Yahya, Mohammed S. Abu-Jafar, Said Al Azar, Ahmad A. Mousa, Rabah Khenata, Doha Abu-Baker and Mahmoud Farout

Crystals 2022, 12(11), 1580; https://doi.org/10.3390/cryst12111580 - 6 Nov 2022

Cited by 3 | Viewed by 2617

Abstract

In this paper, the full-potential, linearized augmented plane wave (FP-LAPW) method was employed in investigating full-Heusler Co₂CrA1’s structural, elastic, magnetic and electronic properties. The FP-LAPW method was employed in computing the structural parameters (bulk modulus, lattice parameters, c/a and first pressure [...] Read more.

In this paper, the full-potential, linearized augmented plane wave (FP-LAPW) method was employed in investigating full-Heusler Co₂CrA1’s structural, elastic, magnetic and electronic properties. The FP-LAPW method was employed in computing the structural parameters (bulk modulus, lattice parameters, c/a and first pressure derivatives). The optimized structural parameters were determined by generalized gradient approximation (GGA) for the exchange-correlation potential, V_xc. Estimating the energy gaps for these compounds was accomplished through modified Becke–Johnson potential (mBJ). It was found that the conventional Heusler compound Co₂CrA1 with mBJ and CGA approaches had a half-metallic character, and its spin-down configuration had an energy gap. It was also found that the conventional and inverse Heusler Cr₂MnSb and tetragonal (139) (Co₂CrA1, Cr₂MnSb) compounds with a half-metallic character had direct energy gaps in the spin-down configuration. To a certain degree, the total magnetic moments for the two compounds were compatible with the theoretical and experimental results already attained. Mechanically, we found that the conventional and inverse full-Heusler compound Co₂CrAl was stable, but the inverse Cr₂MnSb was unstable in the ferromagnetic state. The conventional Heusler compound Cr₂MnSb was mechanically stable in the ferromagnetic state. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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8 pages, 1910 KiB

Open AccessArticle

Morphology and Growth Mechanism of β-Rhombohedral Boron and Pentagonal Twins in Cu Alloy

by Junqing Han, Wentao Yuan, Yihan Wen, Zuoshan Wei, Tong Gao, Yuying Wu and Xiangfa Liu

Crystals 2022, 12(11), 1516; https://doi.org/10.3390/cryst12111516 - 25 Oct 2022

Viewed by 2029

Abstract

In this work, boron particles with β-rhombohedral structure were prepared in Cu-4B alloy. The morphology and growth mechanism of β-B and pentagonal twins were analyzed. Results show that boron crystals possessed an approximate octahedral structure which consisted of two planes belonging to {001} [...] Read more.

In this work, boron particles with β-rhombohedral structure were prepared in Cu-4B alloy. The morphology and growth mechanism of β-B and pentagonal twins were analyzed. Results show that boron crystals possessed an approximate octahedral structure which consisted of two planes belonging to {001} facet and a rhombohedron formed by {101} planes. The morphology of the boron crystal was determined by the position and size of {001} planes. During growth, parts of boron crystal formed twins to reduce surface energy. Five particular single crystals can shape a pentagonal twin. The morphological distinction between pentagonal twins mainly came from the difference in morphology of single crystal. When the {001} exposed planes were large and showed a hexagonal shape, the boron crystal often formed parallel groupings and polysynthetic twins to reduce surface energy. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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Review

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21 pages, 5931 KiB

Open AccessReview

An Overview on Synthesis, Processing and Applications of Nickel Aluminides: From Fundamentals to Current Prospects

by Santosh Sampath, Vignesh Pandian Ravi and Srivatsan Sundararajan

Crystals 2023, 13(3), 435; https://doi.org/10.3390/cryst13030435 - 2 Mar 2023

Cited by 10 | Viewed by 3444

Abstract

Nickel aluminides have desirable properties for use in high-temperature applications. Nickel aluminides have certain desirable qualities, but for almost a decade in the 1990s, those benefits were overshadowed by the challenges of processing and machining at room temperature. Manufacturing improvements, increased knowledge of [...] Read more.

Nickel aluminides have desirable properties for use in high-temperature applications. Nickel aluminides have certain desirable qualities, but for almost a decade in the 1990s, those benefits were overshadowed by the challenges of processing and machining at room temperature. Manufacturing improvements, increased knowledge of aluminide microstructure and deformation processes, and developments in micro-alloying have all contributed to the development of nickel aluminides. Key developments in nickel aluminides, such as their microstructure, alloy addition and alloy development, are given and discussed at length. Methods of production from the past, such as ingot metallurgy and investment casting and melting are addressed, and developments in powder metallurgy-based production methods are introduced. Finally, the difficulties of producing nickel aluminides and possible solutions are examined. This paper gives an overview of the fundamentals, preparation, processing, applications and current trends in nickel aluminides. Full article

(This article belongs to the Special Issue Intermetallic Compound (Volume II))

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