Articles de revues : « Rare-earth Based Intermetallic Compunds »

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Khazzan, S., N. Mliki, L. Bessais et C. Djéga-Mariadassou. « Rare-earth iron-based intermetallic compounds and their carbides : Structure and magnetic behaviors ». Journal of Magnetism and Magnetic Materials 322, n^o 2 (janvier 2010) : 224–29. http://dx.doi.org/10.1016/j.jmmm.2009.08.047.

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Li, Lingwei, et Mi Yan. « Recent progresses in exploring the rare earth based intermetallic compounds for cryogenic magnetic refrigeration ». Journal of Alloys and Compounds 823 (mai 2020) : 153810. http://dx.doi.org/10.1016/j.jallcom.2020.153810.

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Coey, J. M. D., et Hong Sun. « Improved magnetic properties by treatment of iron-based rare earth intermetallic compounds in anmonia ». Journal of Magnetism and Magnetic Materials 87, n^o 3 (juillet 1990) : L251—L254. http://dx.doi.org/10.1016/0304-8853(90)90756-g.

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Bazyleva, O. A., E. G. Arginbaeva, A. V. Shestakov et T. V. Fesenko. « Structure and properties of the intermetallide based on nickel aluminide microalloyed by rare-earth metals ». Voprosy Materialovedeniya, n^o 1(93) (6 janvier 2019) : 35–49. http://dx.doi.org/10.22349/1994-6716-2018-93-1-35-49.

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The paper studies the combined effects of rare earth metals such as praseodymium, neodymium and erbium, melting technologies on intermetallic alloy based on nickel aluminide and pure charge materials using 25, 50 and 75 wt. % of waste, the technology of casting single-crystals of crystallographic orientation [001] and their heat treatment combined with hot isostatic pressing (HIP), on mechanical properties and long-term strength at the level of passport data.

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Bessais, Lotfi. « Structure and Magnetic Properties of Intermetallic Rare-Earth-Transition-Metal Compounds : A Review ». Materials 15, n^o 1 (28 décembre 2021) : 201. http://dx.doi.org/10.3390/ma15010201.

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This review discusses the properties of candidate compounds for semi-hard and hard magnetic applications. Their general formula is R1−sT5+2s with R = rare earth, T = transition metal and 0≤s≤0.5 and among them, the focus will be on the ThMn12- and Th2Zn17-type structures. Not only will the influence of the structure on the magnetic properties be shown, but also the influence of various R and T elements on the intrinsic magnetic properties will be discussed (R = Y, Pr, Nd, Sm, Gd, … and T = Fe, Co, Si, Al, Ga, Mo, Zr, Cr, Ti, V, …). The influence of the microstructure on the extrinsic magnetic properties of these R–T based intermetallic nanomaterials, prepared by high energy ball milling followed by short annealing, will be also be shown. In addition, the electronic structure studied by DFT will be presented and compared to the results of experimental magnetic measurements as well as the hyperfine parameter determined by Mössbauer spectrometry.

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Easton, Mark, Katharina Strobel, Su Ming Zhu, Mark A. Gibson et Jian Feng Nie. « The Influence of Eutectic Morphology on the Impact Properties of High Pressure Die Cast Mg-Rare-Earth Alloys ». Materials Science Forum 654-656 (juin 2010) : 683–86. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.683.

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The impact properties of high-pressure die cast Mg-RE alloys were investigated. It was found that, for rare earth contents between 2-4 wt.%, the Mg-La and Mg-Nd alloys performed better than the Mg-Ce alloys in un-notched tests. The notched results appear to be related to the amount of intermetallic. In contrast, the un-notched results indicate that at some compositions the Mg-La alloys out-performed the other alloys when compared to the amount of intermetallic. It was apparent that a lamellar eutectic structure can improve the un-notched impact properties of Mg-RE based alloys even when this is not evidenced in tensile test or notched impact results.

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Pecharsky, V. K., et K. A. Gschneidner. « Structure, magnetism, and thermodynamics of the novel rare earth-based R5T4 intermetallics ». Pure and Applied Chemistry 79, n^o 8 (1 janvier 2007) : 1383–402. http://dx.doi.org/10.1351/pac200779081383.

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After approximately 30 years of dormancy, the binary, ternary, and multicomponent intermetallic compounds of rare earth metals (R) with the group 14 elements (T) at the R5T4 stoichiometry have become a goldmine for materials science, condensed matter physics, and solid-state chemistry. In addition to providing numerous opportunities to clarify elusive structure-property relationships, the R5T4 compounds may soon be developed into practical materials by exploiting their unique sensitivity toward a variety of chemical and physical triggers. The distinctiveness of this series is in the remarkable flexibility of the chemical bonding between well-defined, self-assembled, subnanometer-thick slabs and the resultant magnetic, transport, and thermodynamic properties of the R5T4 compounds that can be controlled by varying either or both R and T, including mixed rare earth elements on the R-sites and different group 14 (and 13 or 15) elements occupying the T-sites. In addition to chemical means, the interslab interactions are tunable by temperature, pressure, and magnetic field. Presently, a substantial, yet far from complete, body of knowledge exists about the Gd compounds with T = Si and Ge. In contrast, only a little is known about the physics and chemistry of R5T4 alloys with other lanthanides, while compounds with T = Sn and Pb remain virtually unexplored.

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Bazyleva, O. A., E. G. Arginbaeva, A. V. Shestakov et T. V. Fesenko. « Structure and Properties of the Intermetallic Alloy Based on Nickel Aluminide Microalloyed with Rare Earth Metals ». Inorganic Materials : Applied Research 10, n^o 6 (novembre 2019) : 1314–24. http://dx.doi.org/10.1134/s2075113319060066.

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Mukhachev, Roman D., et Alexey V. Lukoyanov. « Composition-Induced Magnetic Transition in GdMn1-xTixSi Intermetallic Compounds for x = 0–1 ». Metals 11, n^o 8 (17 août 2021) : 1296. http://dx.doi.org/10.3390/met11081296.

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Magnetic intermetallic compounds based on rare earth elements and 3d transition metals are widely investigated due to the functionality of their physical properties and their variety of possible applications. In this work, we investigated the features of the electronic structure and magnetic properties of ternary intermetallic compounds based on gadolinium GdMn1-xTixSi, in the framework of the DFT + U method. Analysis of the densities of electronic states and magnetic moments of ions in Ti-doped GdMnSi showed a significant change in the magnetic properties depending on the contents of Mn and Ti. Together with the magnetic moment, an increase in the density of electronic states at the Fermi energy was found in almost all GdMn1-xTixSi compositions, which may indicate a significant change in the transport properties of intermetallic compounds. Together with the expected Curie temperatures above 300 K, the revealed changes in the magnetic characteristics and electronic structure make the GdMn1-xTixSi intermetallic system promising for use in microelectronic applications.

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Micha, G. M., et L. Zhang. « Microstructural characterization of a cast RENi5-based alloy ». Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 août 1993) : 1176–77. http://dx.doi.org/10.1017/s0424820100151714.

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RENi5 (RE: rare earth) based alloys have been extensively evaluated for use as an electrode material for nickel-metal hydride batteries. A variety of alloys have been developed from the prototype intermetallic compound LaNi5. The use of mischmetal as a source of rare earth combined with transition metal and Al substitutions for Ni has caused the evolution of the alloy from a binary compound to one containing eight or more elements. This study evaluated the microstructural features of a complex commercial RENi5 based alloy using scanning and transmission electron microscopy.The alloy was evaluated in the as-cast condition. Its chemistry in at. pct. determined by bulk techniques was 12.1 La, 3.2 Ce, 1.5 Pr, 4.9 Nd, 50.2 Ni, 10.4 Co, 5.3 Mn and 2.0 Al. The as-cast material was of low strength, very brittle and contained a multitude of internal cracks. TEM foils could only be prepared by first embedding pieces of the alloy in epoxy.

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Carvalho, M. H., G. S. Freitas, J. C. Souza, R. B. Campanelli, H. B. Pizzi, S. G. Mercena, M. V. Puydinger dos Santos et al. « Possible routes for the synthesis of nanowires of intermetallic compounds : The case of CeIn₃ ». Journal of Physics : Conference Series 2164, n^o 1 (1 mars 2022) : 012041. http://dx.doi.org/10.1088/1742-6596/2164/1/012041.

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Abstract In this work, we investigated the role of different parameters in the synthesis of intermetallic nanowires of CeIn3 by the metallic-flux nanonucleation (MFNN) method such as template pore diameter, crystallization temperature, heat treatment temperature, and synthesis time. Depending on the growing parameters, we obtained CeIn3 nanowires (d ∼ 350 nm) or CeAlO3 nanotubes. For the nanowires, we observed a suppression of the CeIn3 antiferromagnetic transition from the bulk TN ∼ 10 K to the nanowire system TN ∼ 3 K, which may be associated with the dimensionality affecting the interplay between magnetic exchange interactions, crystalline electrical field, and Kondo effects. We assume that the CeAlO3 nanotubes may result from a reaction with the alumina template and consequent rare-earth oxidation. Our work shows that even it is a great challenge to find the correct growth path of a particular intermetallic compound, the MFNN method can be a promising route to obtain rare-earth based nanowires.

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SINGH, R. P., R. K. SINGH, SHALU et M. RAJAGOPALAN. « FIRST-PRINCIPLE STUDY ON STRUCTURAL, ELASTIC AND ELECTRONIC PROPERTIES OF BINARY RARE EARTH INTERMETALLIC COMPOUNDS : GdCu AND GdZn ». International Journal of Computational Materials Science and Engineering 01, n^o 01 (mars 2012) : 1250005. http://dx.doi.org/10.1142/s2047684112500054.

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First principle study on structural, elastic and electronic properties of binary copper and zinc based rare earth intermetallics have been carried out using the full-potential augmented plane waves plus local orbital (APW+ lo) within density functional theory (DFT). Results on elastic properties are obtained using generalized gradient approximation (GGA) for exchange correlation potentials. The equilibrium lattice parameter, bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameters have been calculated. From electronic calculations, it has been found that electronic conduction in copper and zinc based rare earth intermetallics is mainly attributed to 3d-orbital electrons of Cu and Zn .

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Kushkhov, Kh B., et M. R. Tlenkopachev. « Electrochemical Synthesis of Intermetallic and Refractory Compounds Based on Rare-Earth Metals in Ionic Melts : Achievements and Prospects ». Russian Journal of General Chemistry 91, n^o 2 (février 2021) : 251–72. http://dx.doi.org/10.1134/s1070363221020146.

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Hu, Jinyu, Kun Lin, Yili Cao, Chengyi Yu, Wenjie Li, Rongjin Huang, Henry E. Fischer et al. « Adjustable Magnetic Phase Transition Inducing Unusual Zero Thermal Expansion in Cubic RCo2-Based Intermetallic Compounds (R = Rare Earth) ». Inorganic Chemistry 58, n^o 9 (24 avril 2019) : 5401–5. http://dx.doi.org/10.1021/acs.inorgchem.9b00480.

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Mumbaraddi, Dundappa, Sumanta Sarkar et Sebastian C. Peter. « A review on the synthesis, crystal growth, structure and physical properties of rare earth based quaternary intermetallic compounds ». Journal of Solid State Chemistry 236 (avril 2016) : 94–115. http://dx.doi.org/10.1016/j.jssc.2015.10.032.

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Liu, Jiu Rong, Masahiro Itoh et Ken-ichi Machida. « Frequency dispersion of complex permeability and permittivity on iron-based nanocomposites derived from rare earth-iron intermetallic compounds ». Journal of Alloys and Compounds 408-412 (février 2006) : 1396–99. http://dx.doi.org/10.1016/j.jallcom.2005.04.028.

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Singh, Prashant. « Role of spin-orbit coupling on crystal-field splitting and phase-stability of rare-earth based layered intermetallic ». Scripta Materialia 236 (novembre 2023) : 115644. http://dx.doi.org/10.1016/j.scriptamat.2023.115644.

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Kolchugina, Natalia B., Mark V. Zheleznyi, Aleksandr G. Savchenko, Vladimir P. Menushenkov, Gennadii S. Burkhanov, Yurii S. Koshkid’ko, Jacek Ćwik et al. « Simulating the Hysteretic Characteristics of Hard Magnetic Materials Based on Nd2Fe14B and Ce2Fe14B Intermetallics ». Crystals 10, n^o 6 (17 juin 2020) : 518. http://dx.doi.org/10.3390/cryst10060518.

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The Ce2Fe14B intermetallic, like Nd2Fe14B, has the tetragonal Nd2Fe14B-type structure (space group P42/mnm), in which Ce ions have a mixed-valence state characterized by the coexistence of trivalent 4f1 and tetravalent 4f0 electron states. Despite the fact that the saturation magnetization, magnetic anisotropy field, and Curie temperature of the Ce2Fe14B intermetallic are substantially lower than those of Nd2Fe14B and Pr2Fe14B, Ce2Fe14B retains the capacity of being able to be used in the manufacturing of rare-earth permanent magnets. Moreover, at low temperatures, the anisotropy field of Се2Fe14B is higher than that of Nd2Fe14B, and Се2Fe14B does not undergo the spin-reorientation transition. In this respect, studies of (Nd, Ce)-Fe-B alloys, which are intended for the improvement of the service characteristics-to-cost ratio, are very relevant. A model and algorithm for calculating the hysteresis loops of uniaxial hard magnetic materials with allowance for the K1 and K2 (K2 > 0 and K1 > 0 and K1 < 0) magnetic anisotropy constants were developed and allowed us to obtain data on their effect on the parameters of hysteresis loops for a wide temperature range (0–300 K). The simulation and analysis of hysteresis loops of the quasi-ternary intermetallics (Nd1−хСех)2Fe14B (х = 0–1) was performed. Results of the simulation indicate that the alloying of the Nd2Fe14B intermetallic with Ce to x = 0.94 (1) does not completely eliminate the negative effect of spin-reorientation phase transition on the residual magnetization of the (Nd1−хCeх)2Fe14B intermetallic and (2) slightly decreases the slope of magnetization reversal curve.

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Song, Xiu, Lei Wang, Yang Liu et Hui Ping Ma. « Study on the Mechanical Performance of a Ni-Based Superalloy with Trace Rare Earth Element La Additions ». Advanced Materials Research 509 (avril 2012) : 177–81. http://dx.doi.org/10.4028/www.scientific.net/amr.509.177.

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The microstructures and mechanical properties of the Ni-22Cr-14W-2Mo superalloys with various La contents have been investigated. The results indicate that the grain diameters of the alloys with different La additions are similar to that of the alloy without La. It has also been found that the Vickers Hardness of the alloys increases with the increasing of the La content form 0.000% to 0.087%. The tensile properties of the alloys can be improved by La additions, whereas the σ0.2 proof strength and the elongations of the alloys first increase and then decrease with the increasing of the La content form 0.000% to 0.087%. The alloy with 0.026% La shows the best tensile properties. This result ascribes to the different types of the La-riched phases and the different sizes of them. The La-Ni intermetallic phases with large size precipitating in the alloys have deleterious effects on the improvement of the mechanical properties, if the La content is too high.

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Yoo, Hyo-Sang, Yong-Ho Kim et Hyeon-Taek Son. « Influence of Rare Earth and Fe Addition on the Microstructure and Mechanical Properties of Al-B Alloy ». Journal of Nanoelectronics and Optoelectronics 16, n^o 5 (1 mai 2021) : 806–11. http://dx.doi.org/10.1166/jno.2021.3008.

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In this study, changes in the microstructure, mechanical properties, and electrical conductivity of as-cast and as-extruded Al–B based alloys with the addition of Fe and rare earth (RE) were investigated. The melted aluminum alloy was maintained at 750 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod that was 12 mm in thickness with a reduction ratio of 39:1. The addition of Fe and RE resulted in the formation of Al11RE3 and Al3Fe intermetallic compounds and the area fraction of these inter-metallic compounds increased with increasing Fe and RE contents. As the amount of Fe and RE increased, the average grain size of the extruded Al alloy decreased to 798.6, 196.1, and 21.9 µm, and the high-angle grain boundaries fraction increased to 24.8, 27.9, and 60.7%. In the case of cast materials, low electrical conductivity was shown by porosity and fine casting defects. As the Fe and RE contents increased, the electrical conductivity of the extruded Al–B alloy decreased to 62.3, 59.6 and 55.0% International Annealed Copper Standard. As the Fe and RE content increased the ultimate tensile strength improved from 90.8 to 112.9 MPa which was attributed to the grain refinement and formation of Al11RE3 and Al3Fe intermetallic compounds by the addition of Fe and RE.

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Rosenberg, Elliott W., Jiun-Haw Chu, Jacob P. C. Ruff, Alexander T. Hristov et Ian R. Fisher. « Divergence of the quadrupole-strain susceptibility of the electronic nematic system YbRu2Ge2 ». Proceedings of the National Academy of Sciences 116, n^o 15 (21 mars 2019) : 7232–37. http://dx.doi.org/10.1073/pnas.1818910116.

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Ferroquadrupole order associated with local 4f atomic orbitals of rare-earth ions is a realization of electronic nematic order. However, there are relatively few examples of intermetallic materials which exhibit continuous ferroquadrupole phase transitions, motivating the search for additional materials that fall into this category. Furthermore, it is not clear a priori whether experimental approaches based on transport measurements which have been successfully used to probe the nematic susceptibility in materials such as the Fe-based superconductors will be as effective in the case of 4f intermetallic materials, for which the important electronic degrees of freedom are local rather than itinerant and are consequently less strongly coupled to the charge-carrying quasiparticles near the Fermi energy. In the present work, we demonstrate that the intermetallic compound YbRu2Ge2 exhibits a tetragonal-to-orthorhombic phase transition consistent with ferroquadrupole order of the Yb ions and go on to show that elastoresistivity measurements can indeed provide a clear window on the diverging nematic susceptibility in this system. This material provides an arena in which to study the causes and consequences of electronic nematicity.

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Zamora, J., I. Betancourt et I. A. Figueroa. « Coercivity mechanism of rare-earth free MnBi hard magnetic alloys ». Revista Mexicana de Física 64, n^o 2 (14 mars 2018) : 141. http://dx.doi.org/10.31349/revmexfis.64.141.

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In this work, we present and discuss results concerning the hard magnetic behavior of rare earth-free MnBi alloys obtained by suction casting technique. The physics of coercivity for these type of alloys is based on the nucleation process of reverse domains, which in turn is determined by the alloy microstructure features such as phase distribution, morphology, grain size and in particular, defects, which are characteristic ofreal materials. The microstructure of the as-cast alloy presented here comprises the formation of the Low Temperature Intermetallic Phase (LTIP)-MnBi, interspersed within Bi- and Mn-rich areas. A considerable intrinsic coercivity field of 238 kA/m together with a saturation magnetization of 0.04 T were observed. The nucleation controlled mechanism of this alloy was described in terms of the Kronm¨uller equation, which incorporates the detrimental effect of microstructure defects through fitting parameters associated to reduced intrinsic magnetic properties at grain size boundaries, interfaces and local demagnetizing fields. A notorious switching of coercivity mechanism associated with domain wall pinning was found to be produced upon annealing of the alloy at 583 K for 24 hrs, yielding a drastic reduction of coercivity (down to 16 kA/m). The key microstructural feature determining the switching of coercivity mechanism is the formation/suppression of Bi-rich areas, which promotes the nucleation and growth of LTIP.

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Itoh, Masahiro, Ken-ichi Machida, Hiroharu Nakajima, Kazuhiro Hirose et Gin-ya Adachi. « Nitrogen storage properties based on nitrogenation and hydrogenation of rare earth–iron intermetallic compounds R2Fe17 (R=Y, Ce, Sm) ». Journal of Alloys and Compounds 288, n^o 1-2 (juin 1999) : 141–46. http://dx.doi.org/10.1016/s0925-8388(99)00105-x.

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Starodubtseva, E. V., I. R. Konenko, �. A. Fedorovskaya, E. I. Klabunovskii et V. P. Mordovin. « Asymmetric properties of hydrides of intermetallic compounds based on rare-earth metals, Ni, and Co modified by (+)-tartaric acid ». Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 35, n^o 9 (septembre 1986) : 1781–85. http://dx.doi.org/10.1007/bf00954003.

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Braszczyńska-Malik, K. N. « Mg-Al-RE Magnesium Alloys for High-Pressure Die-Casting ». Archives of Foundry Engineering 14, n^o 2 (1 juin 2014) : 49–52. http://dx.doi.org/10.2478/afe-2014-0035.

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Abstract Experimental Mg-Al-RE type magnesium alloys for high-pressure die-casting are presented. Alloys based on the commercial AM50 magnesium alloy with 1, 3 and 5 mass % of rare earth elements were fabricated in a foundry and cast in cold chamber die-casting machines. The obtained experimental casts have good quality surfaces and microstructure consisting of an α(Mg)-phase, Al11RE3, Al10RE2Mn7 intermetallic compound and small amount of α+γ eutectic and Al2RE phases.

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Park, Sangmin, Dae-Kyeom Kim, Javid Hussain, Myungsuk Song et Taek-Soo Kim. « The Supported Boro-Additive Effect for the Selective Recovery of Dy Elements from Rare-Earth-Elements-Based Magnets ». Materials 15, n^o 9 (21 avril 2022) : 3032. http://dx.doi.org/10.3390/ma15093032.

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Liquid metal extraction (LME) for recycling rare-earth elements from magnets is studied, in the present study, to examine its suitability as an environmentally friendly alternative for a circular economy. While Nd (neodymium) extraction efficiency can easily reach almost 100%, based on the high reactivity of Mg (magnesium), Dy (dysprosium) extraction has been limited because of the Dy–Fe intermetallic phase as the main extractive bottleneck. In the present paper, the boro-additive effect is designed thermodynamically and examined in the ternary and quinary systems to improve the selectivity of recovery. Based on the strong chemical affinity between B (boron) and Fe, the effect of excess boron, which is produced by the depletion of B in FeB by Mg, successfully resulted in the formation of Fe2B instead of Dy–Fe bonding. However, the growth of the Fe2B layer, which is the reason for the isolated Mg, leads to the production of other byproducts, rare-earth borides (RB4, R = Nd and Dy), as the side effect. By adjusting the ratio of FeB, the extraction efficiency of Dy over 12 h with FeB addition is improved to 80%, which is almost the same extraction efficiency of the conventional LME process over 24 h.

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Carbonari, Artur Wilson, José Mestnik-Filho et Rajendra Narain Saxena. « Impurities in Magnetic Materials Studied by PAC Spectroscopy ». Defect and Diffusion Forum 311 (mars 2011) : 39–61. http://dx.doi.org/10.4028/www.scientific.net/ddf.311.39.

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Perturbed gamma-gamma angular correlation (PAC) spectroscopy is a precise and highly efficient tool to follow the temperature dependence of local magnetic fields in any material. Its resolution and efficiency does not depend on temperature and therefore can measure local fields at low as well as high temperature with the same accuracy. Due its versatility in using different probe nuclei it can sense the local magnetic fields at different sites in the crystalline structure of materials. In this review, important results obtained with PAC spectroscopy are shown in two classes of materials: transition metal and transition-metal based compounds and rare earth elements and rare-earth-element based compounds using mainly three different probe nuclei:111Cd,181Ta and140Ce. PAC spectroscopy has contributed to the systematic study of the magnetic hyperfine field in impurities in matrices of Fe, Co and Ni as well as in transition-metal based Heusler alloys. It has also provided important contribution to the investigation of magnetism in rare-earth elements and intermetallic compounds. An still open issue concerning the local fields in metallic magnetic compounds and elements is the exchange interaction between the magnetic ions of the host and a dilute magnetic impurity, which acts as a defect in the magnetic lattice. PAC spectroscopy has been contributing to study this problem with success. Also shown in this review is the crucial role of ab-initio first principle calculations in the interpretation of PAC results.

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Li, Jia Lian, Shu Liang Wang, Lu Jiang Zhou, Xiao Hong Wang, Yuan Hua Lin et Xing Jun Liu. « Thermodynamic Study of Ag-Au-Gd, Tb Ternary Systems ». Materials Science Forum 814 (mars 2015) : 313–18. http://dx.doi.org/10.4028/www.scientific.net/msf.814.313.

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The addition of the rare earth elements into the Ag-based filler alloy, which is typical and important, can control and eliminate the negative effect of impurity elements, and furthermore, it improves the spreading property of the Ag-based filler alloy. Phase diagram provides an important direction for materials design of the Ag-based filler alloy. Thus it is necessary to investigate the phase diagrams and construct the thermodynamic database. On the basis of this background, thermodynamic assessments of the Au-Gd, Tb binary systems were carried out by using the CALPHAD (Calculation of Phase Diagrams) method based on the experimental data including thermodynamic properties and phase equilibrium. The Gibbs free energies of the solution phases were described by sub-regular solution models with the Redlich-Kister equation, while all of the intermetallic compounds were described by sub-lattice models. A consistent set of thermodynamic parameters was derived from describing the Gibbs free energies of each solution phase and intermetallic compound. The calculated phase diagram achieved consistency with the available experiments. Then combined with the assessed relevant binary systems, the Ag-Au-Gd, Tb ternary systems have been predicted. The thermodynamic database of these ternary systems has been developed to present the significant information for the design of Ag-based filler alloys.

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Zada, Zeshan, Junaid Khan, Abdul Ahad Khan, Ali H. Reshak, Dania Ali, Fazal Ur Rehman, Inayat Urrahman, Muhammad Saqib, Muhammad Irfan et Muhammad M. Ramli. « Structural, Thermoelectric, Electronic, and Magnetic Properties of Pristine Intermetallic Rare-Earth-Based XMn₂Si₂ (X=Dy, Er) Compounds ». ECS Journal of Solid State Science and Technology 12, n^o 4 (1 avril 2023) : 043012. http://dx.doi.org/10.1149/2162-8777/acccaa.

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Detailed Structural, thermoelectric, electronic and magnetic properties of the ternary rare-Earth based XMn2Si2 (X=Dy, Er) Compounds, are investigated using the full-potential linearized augmented-plane wave (FP-LAPW) method with generalized gradient approximation (GGA+U) in ferromagnetic phase. The basic calculations of optimization are found with the support of (PBE-GGA) to realize theoretical consistency with existing experimental consequences, although for the enhancement of magneto-electronic part the (GGA+U) technique is employed. We have identified theoretically that the ferromagnetic is the most suitable phase among three studied phases for these compounds agree well with previous experimental works. The electronic band structure indicates that these compounds are metallic through both spin channels in the FM phase. A secure hybridization occurs between the elements Dy/Er-f and Mn-d states in the valence band and the Si-p state in the conduction band. The total magnetic moments verify that the rare-Earth based DyMn2Si2 ternary inter-metallic compound showcases stronger ferromagnetic behavior patterns than the ErMn2Si2 compound. We estimated the Seebeck coefficient S, electrical and thermal conductivities, and the ZT in this study over the temperature range of 0 to 800 K. The ErMn2Si2 is a viable contender for high-temperature applications in waste heat management because of its high ZT values in the high-temperature region in thermoelectric devices.

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Pagare, Gitanjali. « First Principles Based Study of Ground State and Electronic Properties of TmPb₃ Intermetallic Compound ». Journal of Metastable and Nanocrystalline Materials 28 (décembre 2016) : 43–46. http://dx.doi.org/10.4028/www.scientific.net/jmnm.28.43.

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The ground state behavior of rare earth intermetallic compound TmPb3, which crystallize in AuCu3 type structure, has been examined using first principles density functional theory based on full potential linearized augmented plane wave (FP-LAPW) method. Very few study on structural and electronic properties of TmPb3 compound has been available in the literature, which motivated us to perform the present study. The spin polarized calculations are carried out within the PBE-GGA and LSDA for the exchange correlation (XC) potential. Our calculated ground state properties such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B’) are in good agreement with the experimental results. The value of bulk modulus of TmPb3 is found to be 44.32 GPa and 55.01GPa by PBE-GGA and LSDA respectively. The electronic band structure (BS) and density of states (DOS) verify the metallic nature of this compound. The calculated density of states at the fermi level is found to be 0.16 states/eV and 19.50 states/eV for spin-up and spin-down modes respectively. The magnetic moment of TmPb3 is found to be 0.95.

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Perlepe, Panagiota, Itziar Oyarzabal, Aaron Mailman, Morgane Yquel, Mikhail Platunov, Iurii Dovgaliuk, Mathieu Rouzières et al. « Metal-organic magnets with large coercivity and ordering temperatures up to 242°C ». Science 370, n^o 6516 (29 octobre 2020) : 587–92. http://dx.doi.org/10.1126/science.abb3861.

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Magnets derived from inorganic materials (e.g., oxides, rare-earth–based, and intermetallic compounds) are key components of modern technological applications. Despite considerable success in a broad range of applications, these inorganic magnets suffer several drawbacks, including energetically expensive fabrication, limited availability of certain constituent elements, high density, and poor scope for chemical tunability. A promising design strategy for next-generation magnets relies on the versatile coordination chemistry of abundant metal ions and inexpensive organic ligands. Following this approach, we report the general, simple, and efficient synthesis of lightweight, molecule-based magnets by postsynthetic reduction of preassembled coordination networks that incorporate chromium metal ions and pyrazine building blocks. The resulting metal-organic ferrimagnets feature critical temperatures up to 242°C and a 7500-oersted room-temperature coercivity.

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Nunes, D., A. P. Gonçalves, J. Th M. De Hosson et P. A. Carvalho. « On the YFe11Mo intermetallic characterization ». Microscopy and Microanalysis 19, S4 (août 2013) : 135–36. http://dx.doi.org/10.1017/s1431927613001293.

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Rare-earth intermetallic compounds adopting the tetragonal ThMn12–type structure and containing high Fe concentrations have attracted considerable attention in the field of permanent magnets. Among them, the Y-Fe-Mo series has been extensively investigated, especially by X-ray diffraction (XRD), but the microstructural characterization was very limited.In the present work, Y:11Fe:Mo has been prepared by melting Y, Fe and Mo in an arc furnace followed by splat-quenching and/or annealing treatments. The structure, chemistry and magnetic domain configurations of the resulting polycrystalline aggregates have been investigated by XRD, scanning and transmission electron microscopies (SEM and TEM, respectively), energy dispersive X-ray spectroscopy (EDS) and Lorentz microscopy.A special emphasis was given to Lorentz microscopy, where contrast is based on the Lorentz deflection imposed on electrons by the passage through a magnetic specimen. The magnetic domains have been imaged by the intermediate lens in Fresnel mode, with the objective lens switched off. In these conditions the intermediate lens is defocused so that out-of-focus images of the specimen are formed: the magnetic domain walls are imaged as alternate bright (convergent) and dark (divergent) lines. For the overfocused image, bright lines occur at the position of domain walls for which the magnetisation on either side is deflecting the electrons towards the wall, whereas dark lines are observed at the walls for which the magnetisation on either side is deflecting the electrons away from the wall. The opposite contrast is observed at the underfocused image.The results have shown that the tetragonal YFe11-xMoy phase is predominant, with a cellular dendritic morphology (Figure 1), but a considerable presence of -Fe(Mo) could be inferred, forming a coarse intercellular eutectic mixture. Significant Fe segregation occurred during annealing. However, this composition variation corresponded to an extremely limited evolution of the lattice parameters, the Rietveld analysis pointing to Fe vacancies at the 8i sites on the annealed material. XRD and EDS results indicate that the fraction of point defects in the ThMn12-type structure adapts to the processing route and that the stable configuration depends on the temperature. The current study also showed that grain boundaries are usually associated with domain walls and that YFe11Mo grains present internal domain walls forming stripe/maze patterns characteristic of high anisotropy materials (Figure 2), while residual -Fe(Mo) grains exhibit vortex configurations (see arrows in Figures 2 (a-c)).The work was supported by the Portuguese Science Foundation through the CTM/48617/2002 and PEst-OE/CTM-UI0084/2011 grants.

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Du, Andong, Lucia Lattanzi, Anders Wollmar Eric Jarfors, Jinchuan Zheng, Kaikun Wang et Gegang Yu. « On the Hardness and Elastic Modulus of Phases in SiC-Reinforced Al Composite : Role of La and Ce Addition ». Materials 14, n^o 21 (21 octobre 2021) : 6287. http://dx.doi.org/10.3390/ma14216287.

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The use of silicon carbide particles (SiCp) as reinforcement in aluminium (Al)-based composites (Al/SiCp) can offer high hardness and high stiffness. The rare-earth elements like lanthanum (La) and cerium (Ce) and transition metals like nickel (Ni) and copper (Cu) were added into the matrix to form intermetallic phases; this is one way to improve the mechanical property of the composite at elevated temperatures. The α-Al15(Fe,Mn)3Si2, Al20(La,Ce)Ti2, and Al11(La,Ce)3, π-Al8FeMg3Si6 phases are formed. Nanoindentation was employed to measure the hardness and elastic modulus of the phases formed in the composite alloys. The rule of mixture was used to predict the modulus of the matrix alloys. The Halpin–Tsai model was applied to calculate the elastic modulus of the particle-reinforced composites. The transition metals (Ni and Cu) and rare-earth elements (La and Ce) determined a 5–15% increase of the elastic modulus of the matrix alloy. The SiC particles increased the elastic modulus of the matrix alloy by 10–15% in composite materials.

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Collins, Gary S., Qiao Ming Wang et John P. Bevington. « Impurity Diffusion in Highly-Ordered Intermetallic Compounds Studied by Nuclear Quadrupole Interactions ». Diffusion Foundations 2 (septembre 2014) : 95–105. http://dx.doi.org/10.4028/www.scientific.net/df.2.95.

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Diffusion of impurity atoms depends on the sublattices occupied, active diffusion mechanisms, and jump frequencies to neighboring sites. The method of perturbed angular correlation of gamma rays (PAC) has been applied over the past decade to study impurity diffusion through measurement of nuclear quadrupole interactions (NQI) at nuclei of 111In/Cd probe atoms. Extensive measurements have been made on highly-ordered compounds having the L12 crystal structure, including In3R, Sn3R, Ga3R, Al3R and Pd3R phases (R= rare-earth element). Measurements in thermal equilibrium at high temperature served to determine lattice locations of 111In parent probe-atoms, through characteristic NQIs, and to measure diffusional jump-frequencies of 111Cd daughter probe-atoms, through relaxation of the NQI. This paper summarizes results of the jump-frequency measurements and relates them to the conventional diffusivity that can be determined, for example, from penetration profiles of tracer species. In spite of chemical similarities of the series of rare-earth phases studied, remarkably large variations in jump frequencies have been observed especially along series of In3R and Pd3R phases. Most phases appear as “line compounds” in binary phase diagrams, but large differences in site-preferences and jump-frequencies were observed for samples prepared to have the opposing limiting phase boundary compositions. Comparisons of jump-frequencies measured at opposing boundary compositions can give insight into the predominant microscopic diffusional mechanisms of the impurity. A change in diffusion mechanism was proposed in 2009 to explain jump-frequency systematics for In3R phases. An alternative explanation is proposed in the present paper based on site-preferences of 111Cd daughter probes newly observed along the parallel Pd3R series. The diffusivity can be expressed as the product of a jump-frequency such as measured in these studies and a correlation factor for diffusion that depends on the diffusion mechanism. The correlation factor can be modeled for the L12 structure and diffusion sublattice of interest using a five-frequency model originally proposed for metals. Although the correlation factor is an essential parameter for the diffusion of impurities, it has never been measured. It is suggested that values of the correlation factor can be determined feasibly by combining results of jump-frequency measurements such as the present ones with diffusivity measurements made for the same host-impurity systems.

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Лушников, С. А., И. С. Терешина et В. Н. Вербецкий. « Магнитные свойства гидридов соединений RNi-=SUB=-1-x-=/SUB=-Si-=SUB=-x-=/SUB=- (R --- Dy, Gd, x=0.05, 0.02) ». Физика твердого тела 61, n^o 1 (2019) : 81. http://dx.doi.org/10.21883/ftt.2019.01.46897.189.

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AbstractThe magnetic properties of intermetallic compounds GdNi_0.98Si_0.02 and DyNi_0.95Si_0.05 and hydrides based on them have been studied. It is found that a partial substitution of Si atoms for Ni atoms does not cause significant changes in the magnetic characteristics such as the Curie temperature. At the same time, incorporation of hydrogen into the crystal lattice of the GdNi_0.98Si_0.02 and DyNi_0.95Si_0.05 compounds leads to significant decrease in the Curie temperature, attenuation of exchange interactions due to significant increase in the unit cell volume (more than 20%), and an increase in the distances between magnetoactive ions. The magnetism of the initial and also hydrogenated compositions are mainly determined by the contribution from the subsystem of the rare-earth ions.

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Wrona, Adriana, Agnieszka Sierczyńska, Katarzyna Bilewska, Małgorzata Kamińska et Mariusz Staszewski. « Stability of Thermally Processed LaNi₅-Based Alloys for Hydrogen Storage ». Solid State Phenomena 203-204 (juin 2013) : 423–26. http://dx.doi.org/10.4028/www.scientific.net/ssp.203-204.423.

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Hydrogen-absorbing compounds of AB5-type are widely studied in view of their application not only as anode material in fuel cells but also in high-energy Ni-MH cells. Within this work nanocrystalline MmNi3.55Al0.3Mn0.4Co0.75 compounds, where Mm is La–rich mixture of rare earth elements, synthesized by High-Energy Ball Milling (HEBM) of arc-melted alloy and AB5-type alloy/carbon composites prepared by CVD method were studied. As the compounds subjected to high temperature during preparation their thermal stability has been established after annealing at various temperatures. X-ray phase analysis has unambiguously proven that over 400°C single-phase MmNi3.55Al0.3Mn0.4Co0.75 starts to decompose into a multi-phase mixture with Ni-based solid solution as a main phase. Similar behaviour has been observed for composite material. Moreover, carbon distribution on surface of alloy particles is inhomogeneous as seen in microanalysis. Nevertheless, a substantial increase of hydrogen capacity has been observed for composite material in comparison with pure intermetallic compound, when used as anode material in direct borohydride fuel cell (DBFC).

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Michalski, Rafal, et Ryszard J. Radwanski. « Computer Calculations of the Thermally-Induced Magnetic and Electronic Properties of the Rare Earth Compounds RERu₂Si₂ ». Materials Science Forum 480-481 (mars 2005) : 617–22. http://dx.doi.org/10.4028/www.scientific.net/msf.480-481.617.

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The aim of this paper is to demonstrate the effectiveness of the calculation method, which takes into consideration the electrostatic ligands field as well as the the magnetic interactions. Our calculations method based on crystal field (CEF) together with the Zeeman effect in one Hamiltonian and allows calculating many of the temperature dependencies of the magnetic and electronic properties of the rare earth compounds. The result of the calculations shows the accuracy of the approach even for the intermetallic compounds. The obtained results for calculations of the compounds of the family in RERu2Si2 (RE – rare-earth element) are fully confirmed the experimental data such as: the easy magnetic direction of all the analyzed compounds, the thermal dependencies of magnetic properties; in particular the giant magnetocrystalline anisotropy of PrRu2S2 with the calculated anisotropy field BA>400T, in-plain anisotropy of ErRu2Si2, the cause of difficulty in magnetic ordering of compounds TmRu2Si2 and YbRu2Si2 as well as effects and dependencies not foreseen before. In this paper we have put together the elementary calculated magnetic properties for the chosen compounds of RERu2Si2 in the paramagnetic region. All Calculations are on the basis of the calculating computer package BIREC 1.51.

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Rong, M. H., S. D. Lin, Jiang Wang, H. Y. Zhou et G. H. Rao. « Thermodynamic Calculation of Phase Equilibria in the Mn-RE (RE=Nd, Gd, Dy) Binary Systems ». Materials Science Forum 898 (juin 2017) : 1036–41. http://dx.doi.org/10.4028/www.scientific.net/msf.898.1036.

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Ternary intermetallic compounds with rare earth elements and transition metals in the RE-Mn-X (X=Si, Ge, Sn etc.) ternary systems show interesting magnetic properties. As key sub-binary systems of the RE-Mn-X (X=Si, Ge, Sn etc.) ternary systems, the information of phase equilibria and thermodynamic properties of the Mn-RE (RE=Nd, Gd, Dy) binary systems are indispensable to explore the RE-Mn-X (X=Si, Ge, Sn etc.) alloys with better magnetic properties. In this work, the experimental data of phase equilibria and thermodynamic properties of the Mn-RE (RE=Nd, Gd, Dy) binary systems in the published literature were reviewed. Based on the available experimental information, thermodynamic calculation of phase equilibria of the Mn-RE (RE=Nd, Gd, Dy) binary systems was performed using the CALPHAD method. As a result, further experimental investigation and thermodynamic optimization would be still necessary in order to develop the self-consistent and compatible thermodynamic database of the RE-Mn-based alloy systems.

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Ryabov, O. B. « Relationship between the structure and properties for an example of the thermal desorption of hydrogen from selected intermetallic hydrides based on zirconium and rare-earth metals ». Materials Science 45, n^o 5 (septembre 2009) : 655–62. http://dx.doi.org/10.1007/s11003-010-9228-x.

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Князев, Ю. В., А. В. Лукоянов, Ю. И. Кузьмин et А. Г. Кучин. « Роль 3d-электронной подсистемы в эволюции зонной структуры, магнитных и оптических свойств соединений ErNi-=SUB=-5-x-=/SUB=-Co-=SUB=-x-=/SUB=- (x=0-4) ». Физика твердого тела 61, n^o 1 (2019) : 5. http://dx.doi.org/10.21883/ftt.2019.01.46888.173.

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AbstractThe evolution of the electronic structure and optical and magnetic properties of ErNi_5 – _ x Co_ x compounds ( x = 0–4), occurring upon substitution of nickel by cobalt atoms, has been investigated. Spin-polarization calculations of the band spectrum of these intermetallic compounds have been performed within the local spin density approximation with a correction for strong electron correlations in the 4 f shell of a rare-earth ion (method LSDA+U). The values of magnetic moments for erbium, nickel, and cobalt ions (located at different crystallographic sites) are obtained. The exchange-interaction parameters for the 3 d sublattice of transition metals are determined. The spectral properties of the compounds have been investigated in the wavelength range of 0.22–15 μm by optical ellipsometry. The experimental frequency dependences of the optical conductivity in the interband absorption region are compared with the corresponding characteristics calculated based on the density of electronic states.

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Веселова, С. В., И. С. Терёшина, В. Н. Вербецкий, А. Ю. Карпенков et А. Г. Савченко. « Влияние режимов измельчения порошковых материалов (Sm,Ho)-=SUB=-2-=/SUB=-Fe-=SUB=-17-=/SUB=-N-=SUB=-x-=/SUB=- (x=0 ; 2.4) на их структуру и магнитные свойства ». Журнал технической физики 90, n^o 7 (2020) : 1159. http://dx.doi.org/10.21883/jtf.2020.07.49451.412-19.

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The composition, structure, topology of the surface of a cast, homogenized, and nitrogenated alloy based on the Sm2Fe17 intermetallic compound by Ho substitution for Sm have been investigated by means of X-ray fluorescence, X-ray diffraction, and scanning electron microscopy using BSE/EDS detectors. Magnetic properties are presented for initial Sm1.2Но0.8Fe17 compound, Sm1.2Но0.8Fe17N2.4 nitride and its milled powders. It has been established that the partial substitution of Sm by Ho in the rare-earth sublattice in combination with the effect of introduction of nitrogen into the lattice of initial compound lead to an increase of such magnetic characteristics as specific magnetization and coercive force. Comparative analysis of the magnetic hysteresis properties of powder samples showed that an increase of the milling time Sm-Ho-Fe-N powders using high-energy ball milling (15, 30, 45 and 60 min) improves the main magnetic characteristics. The functional characteristics of Sm-Ho-Fe-N powders prepared by milling are an important for the development of new high-coercive permanent magnets based on them.

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SHEN, JIANG, PING QIAN et NAN-XIAN CHEN. « THEORETICAL INVESTIGATION ON THE PHASE STABILITY AND SITE PREFERENCE OF R(Co,T)12 AND R(Co,T)12Nx (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Ho, Er, Dy, T = Mo, Mn, Ni) ». Modern Physics Letters B 17, n^o 08 (10 avril 2003) : 329–38. http://dx.doi.org/10.1142/s021798490300524x.

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The phase stability and site preference of some ternary elements of ThMn12 type rare-earth intermetallic compounds R ( Co , T )12 and R ( Co , T )12 N x are evaluated based on ab initio converted interatomic potentials. The calculated results show that adding either Mo or Mn makes the crystal cohesive energy decrease markedly. It proved that these elements can stabilize R ( Co , T )12 with the ThMn12 structure. The systemic energy is the lowest when T atoms occupy symmetrically 8i sites. For T = Mo or Mn, the doped nitrogen atom does not affect the order of site preference of these stabilizing elements. Moreover, the nitrogen atom occupies 2b sites. According to the calculated results, it can be seen that lattice parameters and X-ray patterns are in good agreement with experiment. All the above results indicate that the ab initio converted pair potentials are effective for the calculation of these kinds of anisotropy materials and some related nitrides.

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Shen, Jiang, Ping Qian et Nan-Xian Chen. « Theoretical Investigation on the Phase Stability and Site Preference of R(Co,T)12 and R(Co,T)12Nx(R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Ho, Er, Dy, T=Mo, Mn, Ni) ». Modern Physics Letters B 17, n^o 17 (20 juillet 2003) : 897–907. http://dx.doi.org/10.1142/s0217984903005950.

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The phase stability and site preference of some ternary elements of ThMn 12 type rare-earth intermetallic compounds R(Co,T) 12 and R(Co,T) 12 N x are evaluated based on ab initio converted interatomic potentials. The calculated results show that adding either Mo or Mn makes the crystal cohesive energy decrease markedly. It proved that these elements can stabilize R(Co,T) 12 with ThMn 12 structure. The systemic energy is the lowest when T atoms occupy symmetrically 8i sites. For T=Mo or Mn, the doped nitrogen atom does not affect the order of site preference of these stabilizing elements. Moreover, the nitrogen atom occupies 2b sites. According to the calculated results, it can be seen that lattice parameters and X-rays are in good agreement with experiment. All the above results indicate that the ab initio converted pair potentials are effective for the calculation of these kinds of anisotropy materials and some related nitrides.

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Straumal, Boris, Kristina Tsoy, Aleksandr Druzhinin, Valery Orlov, Natalya Khrapova, Gregory Davdian, Gregory Gerstein et Alexander Straumal. « Coexistence of Intermetallic Complexions and Bulk Particles in Grain Boundaries in the ZEK100 Alloy ». Metals 13, n^o 8 (6 août 2023) : 1407. http://dx.doi.org/10.3390/met13081407.

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Magnesium-based alloys are highly sought after in the industry due to their lightweight and reliable strength. However, the hexagonal crystal structure of magnesium results in the mechanical properties’ anisotropy. This anisotropy is effectively addressed by alloying magnesium with elements like zirconium, zinc, and rare earth metals (REM). The addition of these elements promotes rapid seed formation, yielding small grains with a uniform orientation distribution, thereby reducing anisotropy. Despite these benefits, the formation of intermetallic phases (IP) containing Zn, Zr, and REM within the microstructure can be a concern. Some of these IP phases can be exceedingly hard and brittle, thus weakening the material by providing easy pathways for crack propagation along grain boundaries (GBs). This issue becomes particularly significant if intermetallic phases form continuous layers along the entire GB between two neighboring GB triple junctions, a phenomenon known as complete GB wetting. To mitigate the risks associated with complete GB wetting and prevent the weakening of the alloy’s structure, understanding the potential occurrence of a GB wetting phase transition and how to control continuous GB layers of IP phases becomes crucial. In the investigation of a commercial magnesium alloy, ZEK100, the GB wetting phase transition (i.e., between complete and partial GB wetting) was successfully studied and confirmed. Notably, complete GB wetting was observed at temperatures near the liquidus point of the alloy. However, at lower temperatures, a coexistence of a nano-scaled precipitate film and bulk particles with nonzero contact angles within the same GB was observed. This insight into the wetting transition characteristics holds potential to expand the range of applications for the present alloy in the industry. By understanding and controlling GB wetting phenomena, the alloy’s mechanical properties and structural integrity can be enhanced, paving the way for its wider utilization in various industrial applications.

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Kablov, E. N., V. P. Piskorskii, R. A. Valeev, S. A. Mel’nikov et A. V. Buzhenkov. « Comparison of the efficiency of effect of rare-earth-based intermetallic additions on the properties of the sintered magnets prepared from a Nd-Fe-Ti-Cu-B base alloy ». Russian Metallurgy (Metally) 2015, n^o 1 (janvier 2015) : 65–67. http://dx.doi.org/10.1134/s003602951501005x.

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Kołodziej, Mieszko, et Zbigniew Śniadecki. « Thermodynamic Modeling of Formation Enthalpies of Amorphous and Crystalline Phases in Zr, Nd, and Ce-Substituted Fe-Si Systems ». Applied Sciences 13, n^o 3 (2 février 2023) : 1966. http://dx.doi.org/10.3390/app13031966.

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The alloys that crystallize in a tetragonal ThMn12-type (space group I4/mmm) structure and are based on Fe and rare earth elements are believed to have a potential to plug the performance gap between ferrite and Nd-based magnets. Nevertheless, the progress is hindered by their poor structural stability, compared with other phases competing during the synthesis process, e.g., Th2Zn17-type. In this work, the enthalpies of the formation (and other thermodynamic parameters) of various phases in (Zr, Nd, Ce)-Fe-Si systems were calculated, with paramount focus on the Fe-rich compositions. We compared and discussed the stability range and stabilization routes for amorphous phases, solid solutions, and intermetallics. The beneficial influence of Zr and Si on the crystallization of intermetallic compounds was confirmed, simultaneously being valid for other phases. Among all of the analyzed Fe-rich phases, the lowest values for enthalpy of the formation of the amorphous phase and solid solution were determined for ZrFe10Si2 (−17.5 and −18.2 kJ/mol, respectively). Moreover, substitution by elements with a large atomic radius is indicated as a method for the introduction of topological disorder, giving possibility for the synthesis of metastable phases (even amorphous) and the utilization of more sophisticated synthesis routes in the future.

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Akashev, L. A., N. A. Popov, V. G. Shevchenko et A. I. Ananyev. « Ellipsometric study of optical properties and oxidation processes of compacted powders based on aluminum alloys ». Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Universitiesʹ Proceedings. Powder Metallurgy аnd Functional Coatings), n^o 2 (19 juin 2019) : 23–32. http://dx.doi.org/10.17073/1997-308x-2019-2-23-32.

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The paper presents the results of an ellipsometric study of compacted powders of aluminum-based binary alloys containing 1,5 wt.% of rare earth elements (Sc, La, Ce, Sm) and cast aluminum-silicon alloys with the following compositions: Al–10Si–0,5Mg– 0,3Fe–0,1Ca and Al–12Si–0,6Mg–0,5Fe–0,5Ca–0,45Na. An immersion method was used to determine the optical constants of massive polycrystalline alloys obtained by remelting these powders in vacuum, as well as their oxide films for a wavelength λ = 0,6328 μm. Using the optical constants of these alloys, the dependence of their reflectivity on the surface oxide film thickness was calculated. It was found that an increase in the amount of the alloying component and intermetallic phases in the alloy decreases its reflectivity. In addition, the optical constants were used in the construction of modified Δ–ψ nomograms calculated using the Maxwell-Garnett equation that make it possible to determine the thicknesses of oxide films on particles and the volume fractions of metal in compacted powders, and to study the processes of their oxidation in air. It was shown that oxidation of aluminum ASD-4 powders and Al–1,5% REM binary alloys at 600 °C is described by a simple model where a decrease in the metal fraction leads to an increase in the oxide film thickness. It turned out that the oxidation of aluminum-silicon alloys is much faster and not described by this model, which may be due to the appearance of a liquid phase in the powder. A large number of metal droplets on the surface of particles increase the amount of metal on the studied tablet surface in general. The high oxidation rate of aluminumsilicon alloys in air can be explained by the surface activity of magnesium in relation to liquid aluminum.

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Kraft, Rainer, Gunter Kotzyba, Rolf-Dieter Hoffmann et Rainer Pöttgen. « Structure and Magnetism of REPtMg (RE = Pr,Nd, Sm) ». Zeitschrift für Naturforschung B 57, n^o 5 (1 mai 2002) : 488–94. http://dx.doi.org/10.1515/znb-2002-0503.

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New magnesium based intermetallic compounds PrPtMg, NdPtMg and SmPtMg were synthesized from the elements by reaction in sealed tantalum tubes in a high-frequency furnace. The three compounds were investigated by X-ray powder and single crystal diffraction: ZrNiAl type, space group P6̄2m, a = 752.34(8), c = 412.66(4) pm, wR2 = 0.0668, 341 F2 values, 14 variables for PrPtMg, a = 748.80(8), c = 411.52(4) pm, wR2 = 0.0521, 196 F2 values, 14 variables for NdPtMg and a = 743.90(5), c = 409.80(3) pm, wR2 = 0.0489, 248 F2 values, 12 variables for SmPtMg. From a geometrical point of view these structures are composed of two types of platinum centered trigonal prisms, i. e. [Pt1Mg3RE6] and [Pt2Mg6RE3]. These prisms are condensed via common edges and faces. Together the platinum and magnesium atoms build three-dimensional [PtMg] networks in which the rare earth atoms are located in distorted pentagonal channels. Magnetic susceptibility data of PrPtMg show Curie-Weiss behaviour with an experimentalmagnetic moment of 3.59(2) μB and a paramagnetic Curie temperature of 7.5(5) K. Ferromagnetic ordering is detected at TC = 8.0(5) K with a magnetic moment of 1.75(5) μB/Pr at 4.5 K and 5 T. SmPtMg orders ferromagnetically below 52(1) K with a presumably complex spin structure in the ordered state.

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Gryc, Adam, Bartlomiej Dybowski, Robert Jarosz et Andrzej Kielbus. « MICROSTRUCTURE OF CAST MgBi6X0.5 (X = Ca, Mn, Zn) ALLOYS IN PEAK-AGED CONDITION ». Journal of Metallic Materials 73, n^o 3 (21 mars 2022) : 23–28. http://dx.doi.org/10.32730/imz.2657-747.21.3.3.

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Cast magnesium alloys are characterised by the lowest density among commercially used structural metals. They are applied mainly in the transportation industry and small, lightweight electronic devices. Due to the low operating temperature of the most widely used alloys from the Mg-Al system, alloys containing rare earth elements with the maximum working temperature reaching 300°C have been developed. However, these alloys are extremely expensive due to the low availability of RE elements. The Mg-Bi system is a promising candidate for the new magnesium-based alloys, as it reveals limited solubility of Bi in Mg enabling precipitation hardening and a high melting point of the Mg3Bi2 phase. The paper presents the results of the analysis of MgBi6 and MgBi6X0.5 (X = Ca, Mn, Zn) alloys’ microstructure in the peak-aged condition. The microstructure of the analysed alloys in the as-cast condition consists of α-Mg solid solution dendrites and Mg3Bi2+α-Mg eutectic compound. Solutionising conducted at 525°C for 8 h, followed by water quenching leads to the dissolution of the intermetallic phases in all of the investigated alloys apart of the MgBi6Ca0.5 alloy. In this case, fine intermetallic phases containing Mg, Bi, and Ca have been found after solutionising. The ageing of the alloys at 200°C results in peak hardness after 120–144 h. The heat treatment leads to the formation of fine strengthening phases within the α-Mg solid solution, characterised by a variety of morphologies – needle, platelet- or lathlike and cuboid. The needle- and platelet- or lathlike phases are found in two sizes – large, with length reaching hundreds of nanometres, and smaller, not exceeding 100 nm. Cuboid particles are found with sizes not higher than 100 nm. The addition of Mn and Zn increases precipitate volume fraction after the heat treatment. Additionally, in the case of the MgBi6Zn0.5 alloy, particles forming an angle of 120° were found, which indicates their presence at the prismatic planes of α-Mg HCP crystal lattice.

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Mondal, Suman, Pushpendra Yadav, Anan Bari Sarkar, Prabir Dutta, Saurav Giri, Amit Agarwal et Subham Majumdar. « Competing magnetic interactions and magnetocaloric effect in Ho₅Sn₃ ». Journal of Physics : Condensed Matter 34, n^o 2 (29 octobre 2021) : 025801. http://dx.doi.org/10.1088/1361-648x/ac2cf1.

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Abstract The rare-earth intermetallic compound Ho5Sn3 demonstrates fascinating magnetic properties, which include temperature-driven multiple magnetic transitions and field-driven metamagnetism. We address the magnetic character of this exciting compound through a combined experimental and theoretical studies. Ho5Sn3 orders antiferromagnetically below 28 K, and shows further spin reorientation transitions at 16 K and 12 K. We observe a sizable amount of low-temperature magnetocaloric effect (MEC) in Ho5Sn3 with a maximum value of entropy change ΔS = −9.5 J Kg−1 K−1 for an applied field of H = 50 kOe at around 30 K. The field hysteresis is almost zero above 15 K where the MEC is important. Interestingly, ΔS is found to change its sign from positive to negative as the temperature is increased above about 8 K, which can be linked to the multiple spin reorientation transitions. The signature of the metamagnetism is visible in the ΔS versus H plot. The magnetic ground state, obtained from the density functional theory based calculation, is susceptible to the effective Coulomb interaction (U eff) between electrons. Depending upon the value of U eff, the ground state can be ferromagnetic or antiferromagnetic. The compound shows large relaxation (14% change in magnetisation in 60 min) in the field cooled state with a logarithmic time variation, which may be connected to the competing magnetic correlations observed in our theoretical calculations. The competing magnetic ground states are equally evident from the small value of the paramagnetic Curie–Weiss temperature.

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