Papers by Keyword: Yttrium

Abstract: In the present investigation, Y³⁺ doped (5 wt. %, 10 wt. %, and 12 wt. %) cerium sesquisulfides (Ce₂S₃) nanoparticles (NPS) were synthesized by a simple chemical precipitation method. Thin films of Y³⁺:Ce₂S₃ NPs achieved on ITO (indium tin oxide) substrate. XRD (X-ray diffraction) patterns were used to estimate the size of the NPS, morphology index, texture coefficient, and lattice constants. The crystallite size was found to be in the range of 18-34 nm. UV-visible spectral studies were carried out in order to understand optical absorptivity, and optical band (E_g) of the as-synthesized nanostructures (NS). It has been observed that the red shift in the optical absorptivity and E_g value varies between 3.45 eV to 2.59 eV. Morphology and the presence of Y⁺³ were investigated by scanning electron microscope (SEM) and energy dispersive X-ray studies (EDX). However, agglomerated spherical-shaped NPs and homogeneous dispersion of Y³⁺ were observed in EDX analysis. Chemical constituents and nature of the doped NS were examined by X-ray photoelectron spectroscopy (XPS), and binding energies matched with Y 3d_3/2, Y 3d_5/2, Ce 3d_3/2, Ce 3d_5/2, O1s, C1s peaks. Y³⁺: Ce₂S₃ (12 wt. %) NS subjected for dielectric property studies in the frequency range of 10 Hz-10 MHz at room temperature (RT). High dielectric permittivity (Ɛ), and very low dielectric loss (tan δ) were observed at low frequency for 12 wt. % Y³⁺:Ce₂S₃ NS as compared with other doped NS. The as-synthesized NS can be used for high dielectric permittivity, low dielectric loss, and capacitor-related applications.

Abstract: The major problems that facing sustainability is the heat production with electricity transmission. The research and engineering communities hope that superconductive materials will be employed in the power transmission, without any losses along the way. Solid-state reaction is a one of the methods for preparing compound samples. This method was used to prepare the nominal chemical formula Y₂Ba₄Cu₇O₁₅. The calcining of the mixed powder at constant temperature of 800C0, followed by compressing the mixed, under (7, 8, 9) tons/cm2 pressures, as pallets shape with diameter 1.5 cm and thickness (0.2-0.3) cm inducing. The prepared samples were encounter many sintering processes through constant temperature. The sintering processes were done in the furnace by rising and cooling temperature with Oxygen rate 0.5 L/min. The samples were measured electrically to determine the resistivity changes in different temperatures (77–300) K, using four-probe technique. The results for the samples A, B and C shows the onset superconducting transition temperatures (Tc (onset)) at 88 K, 93 K, and 99 K respectively. The XRD data illustrated a polycrystalline structure for all samples. The transition temperature, oxygen content (δ) and the lattice parameter increase with increasing the pressure.

Abstract: The current work deals the phenomenon of non-metallic inclusions as a result of the addition of Yttrium as an alloying component. The order of introducing individual components determines its final content in steel. This problem was analyzed using the WYK_Stal program developed at AGH-UST. Individual cases were considered using the accepted thermodynamics models based on Wagner’s formalism. The study of Y₂O3 and Y₂S₃ phase precipitation and the relationship between the addition of Y, Al, Ca, O and S in molten steel was studied using the thermodynamic models. Based on the simulation, the authors stated that, the introduction of aluminum as the final deoxidizer into the liquid steel before the yttrium, results in the formation of non-metallic oxide inclusions. The low oxygen content in the metal bath promotes the formation of yttrium sulphide. In the case of calcium dosing, it is reasonable that, the yttrium is introduced after this element, which limits the losses on the formation of the yttrium sulphide phase.

Abstract: The research results on the effect of small additions of yttrium 0-0.3 wt.% on the structure, hardness, microhardness and distribution of elements in various structural components of chromium white cast iron are presented. It has been established that small additions of yttrium contribute to the grain refinement of the carbide phase and the formation of trigonal chromium carbide (Fe,Cr)₇C₃ in the structure of chromium white cast iron.

Abstract: We report the results of studies on the electronic state of the hole-doped Y-based pyrochlore iridate, (Y_1-x-yCu_xCa_y)₂Ir₂O₇. We carried out the resistivity, Muon Spin Relaxation (μSR), X-ray Photoemission Spectroscopy (XPS) measurements and Density Functional Theory (DFT) calculations on the non-doped (x=y=0) and doped (x=0.05, y=0.15) systems. We found in the non-doped system that the magnetic ordering of Ir spins which was accompanied by the metal-insulator transition (MIT) occurred at around 157 K and disappeared in the doped system in which MIT seems to disappear or smeared out. We suggest from the current study that a quantum critical point which shows a change in the electronic ground state from insulating to metallic to exist between those two systems.

Abstract: As-cast (Fe_0.83Ga_0.17)_100-xY_x (x=0, 3, 6 and 9) alloys were prepared by non-consumable vacuum arc melting furnace under a protective argon atmosphere. The crystal structures and surface morphologies of the alloys were studied by X-ray diffraction (XRD), optical microscope (OM) and scanning electron microscopy (SEM), combined with energy dispersive spectroscopy (EDS), respectively. The surface domain structures were observed by atomic force microscopy (AFM). The magnetostriction coefficients of the alloys were measured by strain gauging method. The results showed that the as-cast Fe₈₃Ga₁₇ alloy was composed only of a single phase of A2 with bcc structure, whereas the ternary Fe-Ga-Y alloys contain multiphase structure, besides the A2 phase, (FeGa)₁₇Y_1.76 new phases are observed as well, and an elemental yttrium phase appeared when the yttrium content increased to x=6 and x=9. Doping with yttrium have an effect on the change of magnetic domain structure of the binary alloy. With increasing x, the magnetostriction coefficient of the (Fe_0.83Ga_0.17)_100-xY_x alloys decreased sharply. The minimum magnetostriction coefficient is reduced to 12 ppm at the magnetic field of 426kA/m when x=9.

Abstract: When bauxites from the Middle Timan and Severouralsk deposits are processed into alumina by the low-temperature sintered process the high-iron content red mud can be obtained. The red mud contain up to 58 % of iron and are a potential raw material for ferrous metallurgy. Rare earth elements (REEs) such as Sc, Y and La are converted from bauxites to red mud in the form of hydroxides during processing and are easily leached by weak acid solutions. In this work, the red mud is treated with a solution of sulfuric acid (pH = 2.5–5), the REEs pass into solution, and then the solution is neutralized to obtain a precipitate, i.e. a concentrate of rare elements. The recovery of REEs is about 75–90 % (Sc, Y, La). The high-iron content red mud is converted to the naturally-doped cast iron and titanium slag (up to 50 wt.% TiO₂). As a result of processing bauxite, alumina (Al₂O₃), the naturally-doped cast iron, concentrate of REEs (Sc, Y, La, etc.) and titanium slag (TiO₂) are obtained. The flowsheet of the proposed complete processing of the high-iron content red mud is given.

Abstract: In this study, to investigate effects of yttrium and other elements for non-basal slips, magnesium alloy single crystals were stretched parallel to basal plane in various temperatures, and polycrystalline magnesium alloys were also tested to estimate contribution of non-basal slips to their tensile deformation behaviour. In pure magnesium single crystals, second order pyramidal (c+a) slip (SPCS) was observed at 298K. Above room temperature, first order pyramidal (c+a) slip (FPCS) was active. In the Mg - (0.6-0.9) Y alloy single crystals, FPCS was observed at 77K to 298K, while yield stress of the Mg-Y alloy single crystals was higher than that of pure magnesium. In tensile test of polycrystalline specimen, slips lines of non-basal slip systems such as SPCS, FPCS and prismatic slip were observed even at yielding in addition to basal slip lines. Among the non-basal slips, activities of FPCS and prismatic slips were increased with increasing strain in Mg - Y alloy polycrystals. Our study suggested that active non-basal slip system in tension parallel to basal plane is (c+a) pyramidal slip and enhanced ductility of magnesium - yttrium alloy would be caused from increased activity of FPCS by yttrium addition.

Abstract: Dry methane reforming (DRM) has recently received considerable attention as a perspective CO₂ utilization technology allowing the valorization natural gas and biogas. The commercialization of the DRM process depends on the use of more stable and active catalysts. The nickel-based catalysts are commonly used in the DRM reaction as they are effective in hydrogen production and nickel is a less expensive material compared to noble metals. However, Ni-based catalysts undergo fast deactivation. The stability of nickel catalysts in DRM reaction may be enhanced by introduction of supports or promoters with basic and/or redox properties. Thus, in this work, Ceria-Zirconia supports were modified by rare earth metals such as Lanthanum, Praseodymium and Yttrium in order to stabilize the raw materials and to promote the catalytic activity. Nickel was then impregnated on such supports and the modified catalysts were tested in dry methane reforming for syngas production since it was already reported that a promotion with nickel and yttrium lead to better activity in DRM catalytic tests over mesoporous materials. All promoted catalysts were characterized by the means of S_BET, XRD, TEM, H₂-TPR, CO₂-TPD in order to define the physical, textural and chemical properties. The influence of basicity on the catalytic activity was clearly evidenced. Moreover, the influence of Nickel loading was also studied. It was evidenced that an optimal Ni loading is needed in order to reach higher activity and stability in DRM.

Abstract: The granular structure of ceramic material influences the electrical properties. Ceramics of YMNO (Y₂NiMnO₆) doped with Nd were produced by compression and sintering. Grain size was determined from SEM image analysis. Generally, As the Nd dopant concentration was increased, the grain size increased with sintering time. However, at the highest dopant levels of 30% and 20% Nd, a large range in grain size was observed with regions of defective growth. In contrast, a more uniform grain growth was seen for the 10% Nd doped ceramic at all sintering times.