As is known, rare-earth metals (REMs) are promising magnetocaloric materials. The magnitude of the magnetocaloric effect (MCE) of REMs significantly depends on their purity. This paper presents results of studies of the magnetic and magnetocaloric properties of sublimed dysprosium, prepared in the course of the present study, with an emphasis on its impurity and structure perfection. The comprehensive analysis of the chemical composition of sublimed dysprosium, which was performed for the first time by atom probe tomography, showed that the metal corresponds to high-purity rare-earth metals (3N+). The MCE effect was studied using direct measurements of the adiabatic temperature change (ΔTad) in pulsed (up to 50 T) and steady (up to 14 T) magnetic fields. The studies of the MCE of polycrystalline sublimed Dy by direct method showed that the high ΔTad value for sublimed Dy are comparable with that for magnetic fields of 5 T. The vacuum sublimation, which is more economical and technologically advanced in contrast to single crystal growing, can be used to create magnetocaloric REM-based materials with high MCE values.

Owing to the high temperature stability of hysteretic characteristics and corrosion resistance under external actions, (Sm,Zr)(Co,Cu,Fe)z-based magnets are widely used in devices operating at high temperatures, most critical constructions of aerospace engineering and defense technology, and in traction electric motors for transport engineering. A number of modern research methods are used to study in detail the structure and phase composition of the (Sm,Zr)(Co,Cu,Fe)z alloys with z = 5.5 – 7.0 in as-cast state and after heat treatment, which includes the solid solution treatment at 1150 – 1180 °С for 5 h, subsequent water quenching, isothermal aging at 800 °С for 20 h, and cooling (stepped aging) from 800 to 400 °С at an average cooling rate of 100 °С/h. The results obtained allowed us to suggest the schematic diagram of grain-boundary constituent transformation at different stages of heat treatment of (Sm,Zr)(Co,Cu,Fe)z permanent magnets prepared by powder metallurgy. The formation mechanism of high-coercivity state of (Sm,Zr)(Co,Cu,Fe)z permanent magnets in the course of complete heat treatment cycle is given as the sequence of phase transformations accompanied by redistribution of a number of alloy components.

The finite element micromagnetic simulation is used to study the role of complex composition of 2:17R-cell boundaries in the realization of magnetization reversal processes of (Sm, Zr)(Co, Cu, Fe)z alloys intended for high-energy permanent magnets. A modified sandwich model is considered for the combinations of 2:7R/1:5H phase and 5:19R/1:5H phase layers as the 2:17R-cell boundaries in the alloy structure. The results of the simulation represented in the form of coercive force vs. total width of cell boundary showed the possibility of reaching the increased coercivity at the expense of 180°-domain wall pinning at the additional barriers within cell boundaries. The phase and structural states of the as-cast Sm1-xZrx(Co0.702Cu0.088Fe0.210)z alloy sample with x = 0.13 and z = 6.4 are studied, and the presence of the above phases in the vicinity of the 1:5H phase was demonstrated.

We show here that palladium-lutetium foil Pd–11.2 wt

In present study, X-ray diffraction and local electron probe microanalysis are used to identify microstructural and phase features of as-cast (Sm,Zr)(Co,Cu,Fe)z alloys used for manufacturing high-coercivity permanent magnets. The structure of the as-cast alloys, which were prepared in the wide composition range corresponding to the coexistence of the 2:17 and 1:5 phases, is studied in detail. The 2:17R, 1:7H, 1:5H, 5:19R, 2:7R, 2:7H, 1:3R, and 1:3H phases were identified and are shown to be simultaneously present in the as-cast state owing to the nonequilibrium phase transformations occurred upon solidification of the ingots.

In the present study, the domain structure of high-coercivity and high-performance Nd–Fe–B-based permanent magnets, which were prepared by the binary mixture blending technology in using rare-earth metal hydrides, is studied by atomic force microscopy. The domain structure is observed both perpendicular and parallel to the magnet texture axis; these surfaces are shown to be characterized by maze-like domain structure with spike domains and strip domains, respectively. The domain structure is analyzed with 3D images. Substantial changes in the domain structure of Nd–Fe–B magnet prepared with DyH x hydride addition are demonstrated and analyzed; the formation of single-domain grains is demonstrated. The domain structure of Ce-containing magnets with the high coercive force is studied.

The hard magnetic (Sm,Zr)(Co,Fe,Cu)z alloys intended for the application as powder filler in bonded magnets are considered. The microstructure and intrinsic coercive force of the Sm0.87Zr0.13(Co0.702Cu0.088Fe0.210)6.7, Sm0.81Zr0.19(Co0.702Cu0.088Fe0.210)6.3, and Sm0.85Zr0.15(Co0.690Cu0.070Fe0.240)6.8 alloys, the structural and magnetic states of which were prepared at different aging temperatures and cooling rates, are studied. The formation of the high coercive force and adequate squareness of the magnetic hysteresis loop for alloy powders under study was observed at grain and subgrain sizes of the 2:17 phase of 10 – 20 μm. It is shown that the anisotropic powders of the Sm0.87Zr0.13(Co0.702Cu0.088Fe0.210)6,7 alloy can be prepared for manufacturing bonded magnets with a coercive force of 14 – 20 kOe and higher, which are intended for the application in electric machines.

X-ray diffraction and differential thermal analyses are used to study multicomponent Nd–R–Fe–B (R = Pr, Ce, La) alloys prepared by induction melting in an inert gas atmosphere and subsequent forced cooling upon casting in a massive cast iron mold. The effect of substitution of light rare-earth metals for neodymium on the phase composition and morphology of the cast alloys with 0–6.9 wt % Pr, 0–10.0 wt % Ce, and 0–9.0 wt % La, which are used as precursors in manufacturing sintered permanent magnets with high hysteretic characteristics, is studied. The main structural constituents of the alloys are shown to be a magnetic phase with the Nd2Fe14B-type structure and Nd-rich, R1.1Fe4B4, and R2Fe17 phases. The phase transformation temperatures of the alloys are determined, which allow us to correct the sintering temperatures of permanent magnet powder blanks prepared from the cerium- and lanthanum-containing alloys.

The wide application of Nd-Fe-B permanent magnets in addition to the rare-earth metal resource constrains determine the necessity of their recycling. One of approaches to magnet-to-magnet recycling consists in using the grain boundary modification of sintered magnet material, which includes the grain-boundary diffusion (GBD) and grain-boundary structuring (GBS). The preparation of magnets with the modified structure determines a need for research their corrosion resistance. The corrosion resistance of magnets prepared by powder blending techniques, namely, magnets, which were recycled from hard-disk drivers, in using Dy/NdH 2 additions in the powder mixture and magnets, which were prepared from strip-casting alloy, in using TbH2 hydride in the powder mixture, is studied. The corrosion potential and polarization resistance were measured, and the average corrosion rate was estimated based on polarization measurements of the magnet samples in the aqueous solution 0.1 M NaCl. Furthermore, a pitting resistance corrosion test was conducted and the values of pitting and repassivation potential were determined. The corrosive properties of the magnet samples are discussed from the viewpoint of the phase compositions of the material.

The purity of hydrogen, which is an alternative energy carrier in powder sources of distributed energy resource systems and, in particular, is the feed stock for fuel cells, should be no less than 99.9999 vol % purity High-purity hydrogen can be prepared only via its separation as a result of selective diffusion through metallic membranes manufactured from specific membrane palladium-based alloys prepared in the form of thin foils. In the present work, the combination of deformation and annealings under different conditions is used to prepare the Pd–7.70 wt % Lu alloy in the form of foil 50 µm thick, whose specific hydrogen permeability is studied in the course of cyclic heating and cooling in a hydrogen atmosphere in a temperature range of 300–500°С. The Pd–7.70 wt % Lu membrane is shown to demonstrate high and stable hydrogen permeability. The evolution of the surface structure of the membrane in the course of its operation in the hydrogen atmosphere is studied by atomic force microscopy using the phase contrast mode.

The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.

The application of powder blending procedure shows promise in manufacturing Nd-Fe-B magnets; in this case, hydrides, oxides, intermetallic compounds, etc. are used as one of the mixture components. The application of these additions allows one to increase the hysteretic characteristics of Nd-Fe-B magnets at the expense of realized grain-boundary diffusion and grain-boundary structuring processes since these characteristics of the magnets are highly sensitive to their microstructure, composition of phases, and distribution of alloy components as well. This study is focused on the possibility of using the Pr3Co0.6Cu0.4Hx composition as the addition to the powder mixture for manufacturing Nd-Fe-B magnets and on the processes occurred during hydrogen treatment of the addition. The base alloy having the composition Nd-24.0, Pr-6.5, Dy-0.5, B-1.0, Al-0.2, Fe-balance was prepared by strip-casting and subjected to hydrogen decrepitation at 270 degrees C for 1 h. The Pr3Co0.6Cu0.4 alloy was prepared by arc melting in an argon atmosphere and subjected to homogenizing annealing at 600 degrees C for 90 h and subsequent hydrogenation under the conditions used for the strip-cast alloy. The phase composition of Pr(3)Co(0.6)Cu(0.4)Hx was studied by X-ray diffraction analysis, DTA, scanning electron microscopy, and electron microprobe analysis. The Pr(3)Co(0.6)Cu(0.4)Hx composition was shown to undergo the hydrogenolysis with the formation of PrHx hydride (or hydrogen solid solution in Pr), Co+Cu fine mixture, and PrCu compound. The behavior of the additions in manufacturing sintered permanent magnets is analyzed from the viewpoint of the grain-boundary structuring effect of the addition. The sintered magnet prepared from the hydrogenated mixture Nd-Fe-B strip-cast alloy + Pr-3(Co,Cu) compound exhibits the following hysteretic parameters: B-r = 1.35 T, j(Hc) = 1008 kA/m, and (BH)(max) = 349 kJ/m(3).

Palladium membranes have a high selectivity for hydrogen, which is coupled with their temperature and mechanical stability. Such a selectivity of palladium membranes makes the membrane method the single procedure that allows one to prepare the high-purity hydrogen (no less than 99.9999 vol%) being the main energy carrier in hydrogen power engineering. Palladium-rare earth metal solid solutions are possible hydrogen diffusion membrane alloys, since they exhibit the mechanical stability during the permeation along with the high hydrogen permeability characteristic. Palladium-samarium alloys of nominal compositions Pd-2.6, 3.2, 5.2, 6.8, 8.3, 9.5, and 11 at% Sm were prepared by arc melting; ingots were subjected to free forging and cold rolling to a thickness of 50 mu m with intermediate annealing. Vickers hardness, ultimate tensile strength, and relative elongation, were determined and the hydrogen permeability was measured. Within the solid-solution compositions, the strengthening takes place; the ultimate strength increases from 200 MPa (for Pd) to 830 MPa for Pd-8.3.t% Sm. In this case, the relative elongation remains close to that of pure Pd (21 %). Such mechanical characteristics favor the manufacturing ultrathin foils and show promise for using them in high-performance membranes and membrane elements. The alloys demonstrate the high hydrogen permeability at 300 - 600 K, which is higher substantially as compared to that of Pd alloys alloyed with other elements. Variations of mechanical properties and hydrogen permeability are discussed from the viewpoint of the possible ordering of the solid solutions and formation of hydride phases.

Abstract The development of advanced technologies is related to the preparation and application of rare-earth metals. The tendency of development of rare-earth metal (REM) industry in Russia consists in tending to shed its dependence on the importation of REMs, to organize their production and products based on them in the required quantities, and to find new application fields for REMs. The aim of the present study is to elaborate the purification technologies of scandium and scandium hydride and to approbate its application as breakable additions to powder mixtures for the preparation of Nd-Fe-B permanent magnets. It is demonstrated the possibility to control the grains size of the 2-14-1 phase in Nd-Fe-B with the ScH∼2 addition. Moreover, our systematic studies are aimed at the development of corrosion-resistant Ag-free Pd-based REM-containing alloys with the high hydrogen permeability for the separation of high-purity hydrogen from hydrogen-containing mixtures. In the present study, the hydrogen permeability and mechanical properties of Pd-Sc thin foils prepared with special-purity scandium are discussed

X-ray diffraction analysis, scanning electron microscopy, and atomic force microscopy are used to study the phase composition, texture, and peculiarities of the morphology of R–Fe–B (R = Nd, Pr, Dy) alloys prepared by strip-casting technology. Along with the traditional structural components of the alloys, namely, areas characterized by randomly oriented fine grains of the main magnetic phase with the Nd 2 Fe 14 B-type structure (which are formed near the contact surface of flakes) and coarse extended textured grains of the phase (in the volume of flakes), wide areas characterized by uniform distribution of rare-earth metal-rich phase with a period of 2–4 µm were also found. The formation of these areas takes place in the absence of coarse dendritic crystallites and, according to the suggested mechanism, is related to the solidification of the melt under conditions of its motion upon quenching on a cooled cylindrical surface. Data indicating the melt twisting upon solidification, which favors the formation of the structure with the aforementioned distribution of intergranular phase, are reported. The data obtained are discussed from the viewpoint of their practical utility for the improvement of the structure of alloys prepared by strip-casting and powders for manufacturing Nd–Fe–B permanent magnets.

The possibility of applying the Kolmogorov-Avrami equation to describe the kinetics of crystallization of Nd2Fe14B-based alloys is discussed; for the estimation of the fraction of the transformed volume, the results of magnetic measurements are used. A significant influence of zirconium additives on the kinetics of crystallization is revealed.

X-ray structural analysis, scanning electron microscopy, x-ray photoelectron spectroscopy, atomic force microscopy are used to study the structure of compacted specimens of steel 12Kh12M1BFP, modified with additions of fullerenes and carbon nanotubes. The effect of additions on the microhardness of compacted specimens is established.

The methods of x-ray diffraction analysis, Mössbauer spectroscopy, and transmission and scanning electron microscopy are used for studying structural transformations that occur in high-energy milling of steel 12Kh12M1BFR with additives of fullerenes and carbon nanotubes.