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 NdH_x. 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.

Experimental series of alloys for (Sm,Zr)(Co,Cu,Fe)_Z permanent magnets are presented in the concentration ranges that provide wide variations of (4f)/(4d)/(3d) ratios of comprising elements. Optical metallographic analysis, observation of the surface domain structure upon magnetization reversal (Kerr effect), electron microprobe analysis, and measuring the major hysteresis loops of samples at different stages of heat treatment are used to study processes related to the development of the highly coercive state of these samples. It was found that the volume fractions of two main structural components A and B, which comprise 90% of the total sample volume, rigorously control the coercivity at all stages of thermal aging. At the same time, structural components A and B themselves in samples being in the high-coercivity state differ qualitatively and quantitatively in the chemical composition, domain structure and its development in external magnetic fields and, therefore, are characterized by different morphologies of the phases comprising the structural components. Two stages of phase transformations in the sample structure are observed. During isothermal annealing, the cellular structure develops within the B component, whereas, during stepwise (slow) cooling or quenching from the isothermal aging temperature to 400 °C, a phase structure evolves within both the cell boundaries in B and the structural component A. The degree of completion of the phase transformations within micro- and nano-volumes of the components determines the ultimate hysteretic characteristics of the material.

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 Nd₂Fe₁₄B-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 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.

Electron microscopy, X-ray fluorescence, gas, and X-ray diffraction analyses, and magnetometry are used to study the chemical and phase compositions and magnetic properties of a powder prepared by crushing and subsequent milling of end-of-life Nd–Fe–B sintered magnets, which is performed in an isopropyl alcohol medium. The milling processes used for the preparation of powder are among those comprising the manufacturing procedure of sintered NdFeB permanent magnets by powder metallurgy and should not change the phase composition of the alloy. The maximum powder particle size obtained after milling of the waste sintered permanent magnets is 50 μm. The prepared powder is found to be characterized by an increased oxygen content. The phase composition (wt %) comprises 82.0 % Nd₂Fe₁₄B, 9.7% Nd(OH)₃, 8.0% α-Fe, and 0.3% Nd₂O₃. The oxide phases are present at the powder particle surface. The powder material is shown to have the sufficiently high level of magnetic properties. The possibility of application of the powder in manufacturing sintered permanent magnets, in particular, by 3D printing technology is discussed.

We show here that palladium-lutetium foil Pd–11.2 wt % Lu membrane can be efficiently used for hydrogen separation via its diffusion at temperatures 300–500°С. Several correlations of the membrane structure morphology and the specific permeability of the membranes are considered. Particular attention is placed in analysis of the membrane surface studied by atomic force microscopy using the phase contrast mode. The studies performed are addressed the problem of the membrane durability for the cyclic operation up to 40 h in hydrogen atmosphere.