Papers by Keyword: Rare-Earth Metals

Abstract: Thermochromic properties were found in bimetallic hybrid inorganic-organic complex compounds of hexa (thiocyanate-N) chromates (III) of IIIb-group rare-earth metals and lanthanides complexes with dimethylsulfoxide [M(C₂H₆SO)₈]L, dimethylformamide [M (C₃H₇NO)₈]L, ε-caprolactam [M(εC₆H₁₁NO)₈]L and nicotinic acid [M(C₅H₅NCOO)₃(H₂O)₂]L·nH₂O, n=1,2, L=[Cr (NCS)₆]^3-, M=Sc³⁺, Y³⁺, Ln³⁺, obtained by means of direct synthesis from the aqueous solutions, the composition of substances was studied by methods of chemical and electron microscopic analyzes, solubility and chemical resistance were determined. Radiographic and thermogravimetric characteristics, IR spectra, magnetic properties are studied. The experimental data obtained indicate the antiferromagnetic nature of the interaction between paramagnetic centers in the studied ionic compounds, the crystallographic parameters of which were determined by the method of X-ray diffraction analysis of single crystals at low temperatures. In the temperature range of 383-493 K, substances, without changing the physicochemical characteristics, reversibly change color, withstanding many heating-cooling cycles.

Abstract: The paper presents the data obtained in the course of experimental studies on the production of rods from the Al-0.5% REM alloy using combined processing methods, such as combined rolling-extruding (CRE) and combined casting and rolling-extruding (CCRE). The variable parameters were the temperature of the ingot or melt, the degree of deformation and the strain rate. With the help of strain gauge equipment, experimental data were obtained on the forces acting on the rolls and the die of the CCRE-200 combined processing unit in the process of obtaining rods with a diameter of 5 and 9 mm. The estimation of the dependence of the mechanical properties of the rods on the variable factors has been carried out. The highest strength properties are possessed by a bar obtained by the CRE mode at a temperature T = 550 oC and a strain rate ξ = 0.74 s^-1. When comparing the temperature of pouring the metal, the highest strength properties are possessed by a rod with a diameter of 9 mm and 5 mm and a strain rate ξ = 0.74 s^-1. If compare in terms of the deformation rate, then the highest strength properties are possessed by a rod with a diameter of 5 mm and a deformation rate ξ = 1.49 s^-1. The plasticity of deformed semi-finished products in all modes is at a high level, which allows further processing.

Abstract: Analytical and experimental studies have been carried out, which made it possible to propose new technological modes of combined rolling-extruding for the production of rods from alloy 01417 for the further drawing of wire for electrical purposes. The force parameters on the rolls and the die are calculated when extruding a rod with a diameter of 5 mm on the laboratory unit CRE-200 and the industrial unit CRE-400. The obtained values of the forces on the rolls and the die do not exceed the permissible values of the power load of the units. Therefore the selected parameters are suitable for conducting experiments on the manufacture of prototypes of rods. To verify the conclusions made, experimental studies were carried out on the CRE-200 unit at a temperature of 320 oC and a drawing coefficient μ = 12.1. The results of experimental studies in comparison with the calculated data showed that the deviation of the calculated data does not exceed 15%.

Abstract: This paper proposed a recycling process for neodymium-iron-boron (NdFeB) magnet scrap from the end-of-life (EOL) of hard disk drives by using hydrometallurgical process. Initial chemical composition of NdFeB magnet scrap was consisted of 25.37%Nd, 6.53%Pr, 0.90%Co, 3.63%B and 63.57%Fe. After de-magnetization and crushing into proper size, magnet scraps were directly leached by H₂SO₄ solution. More than 90% dissolved into acid solution with remaining small amount of residuals and Ni-coated metal. Neodymium precipitated from leached solution by pH-control to the optimum condition at pH 0.6 using NaOH solution. Solid Nd-precipitates XRD pattern was observed in form of NaNd (SO₄)₂.(H₂O) and FeSO₄.(H₂O). Elemental analysis of Nd-precipitates by WD-XRF. The precipitates contained 26.50%Nd, 8.46%Pr and 1.19%Fe. In order to elimination of Fe, Nd-precipitates was leached by using H₂SO₄ solution to dissolve FeSO₄.(H₂O) into acid solution to obtain high concentration of Nd and rare-earth metals (REMs) compound. As a result, XRD pattern of Nd-compound after Fe-removal confirmed that the high purity NaNd (SO₄)₂.(H₂O) compound was obtained. The final composition of precipitates analyzed by WD-XRF was 26.36%Nd, 8.13%Pr with Fe as low as 0.14%Fe.

Abstract: The article presents the results of studies on the production of wire with a diameter of 0.5 mm from aluminum alloy 01417 with a content of rare-earth metals (REM) in the amount of 7-9% for aircraft construction needs. The deformation modes, the experimental technique and equipment for the implementation of the proposed technology described. The wire was obtained by drawing and bar rolling with subsequent drawing from a rod with a diameter of 5 mm, obtained previously using the process of combined rolling-extruding (CRE) from a continuous ingot with a diameter of 12 mm, cast in an electromagnetic mold (EMM). The wire obtained by the presented technology was subjected to 4 different heat treatment modes with annealing temperatures from 350 to 500 °C and holding time of 1 h in the furnace to achieve mechanical and electrophysical properties corresponding to TS 1-809-1038-2018. The level of strength and plastic properties obtained in the course of research required only one intermediate annealing. The microstructure of the wire was investigated and the modes were revealed that made it possible to obtain the required level of mechanical properties and electrical resistivity, satisfying TS 1-809-1038-2018.

Abstract: The differential scanning calorimetry and the method of cooling curves are used to obtain data on liquidus temperatures of oxide-chloride systems Gd₂O₃ – K Cl - GdCl₃. The solubility of gadolinium oxide in K Cl - GdCl₃ melts has been studied. This information can be used for a developing process of the reduction of solid rare-earth oxides into their metals in molten salts.

Abstract: The article presents the investigation results of the structure and properties of rods of aluminum alloys containing zirconium, cerium and lanthanum after ingotless rolling-extruding (IRE) and heat treatment. The patterns of changes in the microstructure, mechanical properties, electrical resistivity depending on the chemical composition of the alloys, processed by the IRE method and various modes of rods annealing are shown. A metallographic analysis of the grain structure of the samples in a deformed state and after annealing performed. The temperatures at which the alloy structure remains stable and maintains the level of operational properties revealed. The effect of chemical composition on the heat resistance of deformed semi-finished products represented. The study made it possible to evaluate the level of properties of experimental alloys after processing by the method of ingotless rolling-extruding and various modes of rods annealing.

Abstract: The double complex compounds - hexa (isothiocyanate) chromates (III) of lanthanide (III) complexes with ε-caprolactam and nicotinic acid [Ln (ε-C₆H₁₁NO)₈][Cr (NCS)₆] and [Ln (C₅H₅NCOO)₃(H₂O)₂][Cr (NCS)₆]·nH₂O, n=1,2 - were produced from the aqueous solutions by means of direct synthesis. The substances are studied by the spectroscopic method; their crystal structure is determined. It is found that all the complexes are of island ionic type. ε-C₆H₁₁NO complexes form triclinic system crystals - space group P ̄1, or monoclinic - space group С2/с. The nicotinic acid compositions crystallize in the monoclinic system, space group P2₁/n. The complexes have reversible heat-sensitive properties and can serve as the chemical sensors in the temperature-sensitive devices that are used for visual inspection of the thermal regime in various technological processes.

Abstract: This paper presents the results of development of ecological low-waste “dry” fluoride technology of magnetic material production on the basis of rare-earth metals of the Nd-Fe-B-system. The physicochemical fundamentals are stated and the basic stages of the proposed technology are experimentally examined: the fluorination of raw material with elemental fluorine, the production of compact ingot alloys and addition alloys by the calcium-thermal out-of-furnace reduction of fluorides, the production of magnets with the help of the powder metallurgy method using mechanical or hydride grinding, as well as waste processing.

Abstract: The stability of the microstructure and properties of the iron superalloys of the secondgeneration IN 519 (24% Cr, 24% Ni, 1.5% Nb) modified with 0.1 and 0.2 [wt.%] rare earthelements was investigated. The alloys underwent annealing at 825 oC for 10, 100 and 1000 h. Thefollowing techniques were used to evaluate the phase transformation: X-ray diffraction on crosssectionand isolates extracted from the as-cast and annealed alloys, microstructure analysis byoptical microscopy, hardness measurements by Brinell and nanoindentation with a Berkovich tipmethod. The analysis of changes in hardness distribution due to thermal processing of superalloyswas conducted with respect to the average hardness of matrix and phase precipitates.