Papers by Keyword: Yttrium

Abstract: The effects of rare earth Y addition on microstructure and properties of pure copper were investigated. Mechanical test, electrical test, oxidation resistance test, metalloscope, scanning electronic microscope (SEM) and X-ray difffraction (XRD) were performed to study the properties, microstructure and constitution. The results showed that both the hardness and antioxidant properties obviously increased with the increase of Y, confirmed the successful refinement role of Y. A small amount of Y (less than 0.5 wt.%) could improve the electrical conductivity of pure copper. When the Y content reached 0.2 wt.%, pure coppers obtained optimum electrical conductivity which is 96.8% IACS. However, over-added Y (>0.5 wt.%) resulted in second phase of Cu₇Y coarsening and non-homogeneous microstructures forming, which reduces the conductivity of copper. In addition, Y can effectively purify the organization of molten copper.

Abstract: The thermodynamic characteristics of processes in the liquid metal system Fe–Y–Cr–C–O are considered as applied to low-carbon and low-alloy metal. The critical parameters for the state diagram of the oxide system Y₂O₃–Cr₂O₃ were established based on the values quoted in literature. The temperature dependence of the melting reaction constant Y₂O₃·Cr₂O₃ was determined. The coordinates of eutectic transformation points for the system Y₂O₃–Cr₂O₃ were calculated. In accordance with subregular solution theory, the energetic parameters which are necessary to calculate the activities Cr₂O₃ and Y₂O₃ of oxide melts in the system Y₂O₃–Cr₂O₃ were determined. The energetic parameters of subregular solution theories for the oxide system FeO–Cr₂O₃–Y₂O₃ were determined based on the values for the binary systems FeO–Y₂O₃, FeO–Cr₂O₃ and Y₂O₃–Cr₂O₃. The view of this diagram, as coupled with the existence domain of liquid metal within the framework of the quaternary system Fe–Y–Cr–O–С, suggests that low-carbon chromic liquid metal when injected with yttrium can form the following non-metallic inclusions: |Cr₂O₃|, |Y₂O₃|, |FeO·Cr₂O₃|, |Y₂O₃·Cr₂O₃| or oxide melt (FeO, Y₂O₃, Cr₂O₃). Oxide melt may contain up to 2 % of divalent chrome (Cr2+). The equilibrium constants for the main reactions of steel deoxidation with the formation of liquid, solid and gas products of chemical reactions were also established. The activity of components dissolved in metal was calculated using interaction parameters. The set of derived expressions for the activity of components and the dependences of equilibrium constants of chemical reactions and phase transformations allowed us to diagram the surface of component solubility in liquid metal (SCSM). SCSM diagrams show the compositions of liquid metal and indicate oxide phases which are in equilibrium with liquid metal.

Abstract: The effect of the rare earth (RE) element Y on the microstructure and hardness of (Mg–0.5Zn–0.5Zr–2.8Nd –1.5Gd) wt% Mg alloy investigated. 1 wt. % Y was added and compared with the base alloy. The microstructure results show the refinement of the grain by the addition of Y and the grains became smaller about 31.8 % and the volume fraction was increases 11.1% %, which led to the increment of hardness from 48.33 HV (as-cast EV31A) to 53.71 HV (as-cast EV31A +1 Y). Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) results showed that the base alloy mainly contained α-Mg matrix and Mg-(Nd, Gd) as a second phase crystallized along the grain boundaries and addition of (Y) yttrium resulted in the formation of the new phase, Mg-Zn-Y-phase was found as a new ternary phase, where Y combined with the original second phase.

Abstract: In order to design a solvent for high-purity SiC solution growth, the impurity incorporation and the carbon solubility of various solvent materials have been investigated. Among the transition metal elements, the impurity elements of Cr, Ti, V and Hf are more readily incorporate during the solution growth than the other transition metal elements. The thermodynamic calculation revealed that the Y-Si solvent has relatively large carbon solubility, which is comparable to the Cr-Si and Ti-Si solvents often used in the solution growth of bulk SiC crystals. From these results, the Y-Si solvent is expected to be a suitable solvent for the high-purity SiC solution growth. Furthermore, we have demonstrated that the Y-Si solvent can achieve lower incorporation of metal impurity in the grown crystal than the Cr-Si solvent maintaining the growth rate.

Abstract: Highly porous crystalline luminescent metal Organic Frameworks (MOFs) were synthesized by conjugating Yttrium nitrate and Benzene Tri Carboxylate (BTC) in the presence of surfactant Cetyl Tri methyl Ammonium Bromide. A characteristic blue emission peak around 400 nm of Y upon excitation with UV light and peaks through Infra-Red spectroscopy revealed the formation of co-ordinate bond between Y and BTC, thereby confirming the formation of MOF nanoparticles (NPs). The nanoparticles were studied for potential removal of pollutants by encapsulation of the dye methylene blue (MB). Optical analysis affirmed the encapsulation of dye particles within the porous MOF NPs as dye absorption decreased around 600nm. This study offers great promise of using MOF NPs as platform for sensing of analytes in solution and removal of pollutant materials.

Abstract: For highly loaded parts, such as medical implants as well as for engineering application, high strength and good ductility are indispensable, but also the fatigue resistance plays an important role. For both, quasi static and fatigue properties, a fine microstructure is essential. Furthermore, especially for titanium alloys the control of interstitial impurities like oxygen and nitrogen is very important. In a former study additions of several oxides of rare earth elements were tested with respect to their effect on the microstructure of MIM processed Ti-6Al-4V. Yttrium oxide has shown the strongest effect on the colony size of Ti-6Al-4V.In this study elementary yttrium powder was added to Ti-6Al-4V. During sintering, the yttrium scavenges oxygen out of the titanium matrix, increasing the ductility. The yttrium oxide, which is formed, leads to a colony refinement and therefore to a higher strength.For preliminary tests cylindrical samples consisting of Ti-6Al-4V powder blended with coarse yttrium powder and a wax and polyethylene-based binder were manufactured by uniaxial pressing and sintering. The addition of yttrium led to a slight decrease of the colony size: specimens sintered at a high temperature of 1400 °C show a stronger dependency of yttrium content on the colony size than those sintered at 1300 °C.Tensile test specimens were produced by MIM using gas atomized Ti-6Al-4V-powder with additions of yttrium powder between 0.1 and 0.5 wt.-%. Sintering took place at temperatures between 1300 °C and 1400 °C with two different dwell times (2 and 4 hours). Tensile tests were conducted in air at room temperature. The microstructures were observed by SEM and light optical microscope. Oxygen and nitrogen contents were analysed by a melt extraction technique.

Abstract: Mg-1Mn-0.6Ce-3Y alloy was prepared by metal mould casting method. The as-cast ingot was homogenized and then hot-extruded by an extrusion ratio of 16:1 at 380 °C. Microstructure and mechanical properties of the as-cast and hot-extruded samples were investigated. The results showed that the as-cast sample mainly consisted of α-Mg, Mg₁₂Ce, and Mg₂₄Y₅ phases. The average grain size of the sample homogenized at 380 °C was about 100μm, and it was greatly refined to about 6μm by dynamic recrystallization for the hot-extruded sample. The ultimate tensile strength, 0.2% yield strength and elongation of the hot-extruded sample were 244 MPa, 178 MPa and 37.5%, respectively. They were enhanced by 82%, 197% and 400%, correspondingly compared with those of the as-cast sample. The improvement of the strengths was attributed to the grain refinement, breakup of the precipitates and increase of the dislocation density.

Abstract: In this study, the wear behavior of AM60 alloys adding different amounts of yttrium (0, 0.5, 1, 1.5, and 2 wt%) during dry sliding has been investigated. The microstructure observation and EDS analysis demonstrated that adding yttrium in AM60 alloy formed a new phase Al₂Y and minimized the precipitation of Mg₁₇Al₁₂ phase. The wear rate and friction coefficient of AM60 alloys adding yttrium were lower than that AM60 alloy under the same condition. The worn surface was covered with long continuous grooves parallel to the sliding direction. The wear resistance of AM60 alloy was improved when yttrium was added due to the formation of uniformly is tribute finer and harder Al₂Y precipitates. The harder Al₂Y precipitates increased the hardness and wear resistance of the AM60 alloy and reached the maximum at 1 wt% Y.

Abstract: Colossal permittivity (CP) in BaTiO₃ (BT)-based polycrystalline ceramics with normal grain sizes has been successfully obtained in yttrium (Y) doped BT ceramics (BYT) via a simple and effective method. Considering the necessary factors for CP formation mechanism, well designed doping condition and sintering procedure were carried out in the sample preparation. Characterizations show that BYT is with a pure tetragonal perovskite structure and the grain growth is depressed under the action of Y donor doping. The frequency independence of permittivity and Debye-like relaxation related to Maxwell-Wagner relaxation which occurred at the interfaces between semiconducting grains and insulating grain boundaries can be detected. These are induced by an internal barrier layer capacitance (IBLC)-type structure which formed under an overall and carefully designed synthesis procedure. But the temperature independence of permittivity does not arise because of the particular tetragonal structure and micron dimension grain sizes of BYT.

Abstract: Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the concentrations of rare earth elements and yttrium (REY) in coal and associated rock samples from the Guanbanwusu Mine, Jungar Coalfield, Northern China. The Guanbanwusu coals have a similar vitrinite reflectance and sulfur content, and a slightly higher ash yield. The concentration of REY (from La to Lu plus Y) in the 6 coal of the Guanbanwusu Mine varies from 72 μg/g to 396 μg/g and averages 186 μg/g, higher than that in normal Chinese coal (136 μg/g) and much higher than that in average world hard coals. The H-type distribution patterns in the No. 6 coal (W9-2 and W9-9) were probably caused by stronger water influences than those in the other coalfield. The coal bench (W2 and W9) with L-type is because terrigenous input influence.