Hydrothermal synthesis of Y(OH)3, Y(OH)3:Eu3+ nanotubes and the photoluminescence of Y(OH)3:Eu3+,Y2O3:Eu3+

The phase and morphology transformation during the hydrothermal treating process of Y2O3 was evaluated with X-ray diffcrcnce (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size and specific surface area determination.The results showed that the cubic Y2O3 did not transfer into hexagonal Y(OH)3 in pure water. Therefore, pure hexagonal Y(OH)3 with nanotube and microrod morphologies were obtained by hydrothermal treating Y2O3 at 150℃ for 12 h in 15 ml of 2 mol/L NaOH solution with and with-out PVA or PEG It was suggested that the characteristic preferential growth of Y(OH)3 was attributed to the structure anisotropy of hexahedron Y(OH)3. The addition of PVA or PEG could promote the forming process of nanotubes by selective adsorption on different crystal planes,which altered the growth rate along different directions and resulted in the diffusion limit of constructing ions in the center top of rods. Finally,Y(OH)3:Eu and Y2O3:Eu nanotubes were also synthesized by using this method, and their photoluminescence properties were evaluated.     

Separation and Recovery of Copper,Nickel and Cobalt from the Copper Converter Slag by Solvent Extraction

An attempt has been made to develop a simple SX flowsheet to recover Ni, Cu and Co separately using alkyl phosphonic acid PC 88A diluted with kerosene. Process parameters such as phase ratio. pH of the feed solution and number of stages for extraction, scrubbing and stripping have been optimised. A computer program in FORTRAN has been developed to determine the process parameters for producing pure solutions of Ni. Cu and Co simultaneously in a counter-current set up. Conventional approach of separating individual metals in the order of their extraction affinities has also been studied. Both the processes have been found to yield Co, Cu and Ni sulphate solutions of purities required for downstream metal winning steps. This paper presents the salient data collected along with the optimised flowsheets.     

Study on Red Long-Time Luminescent Material Y2O2S:Eu,M (M = Mg,Ca, Sr,Ba)

The red long-time luminescent material Y₂O₂S:Eu³⁺, M (M = Mg, Ca, Sr, Ba) was prepared by high temperature solid-state method. The XRD result of the sample showed that the crystal phase was Y₂O₂S, which belong to hexagonal system, and no new crystal phase were by doping different amount of Mg, Ca, Sr, Ba. The excitation spectrum was a broad band within 200 × 400 nm region, the characteristic peaks of emission spectrum were located at 583, 595, 597, 617, 627, 707 nm. There was no marked change in excitation spectra, emission spectra and maximum of their wavelengths of the luminescent materials by doping with different ions. The luminescent intensity of the phosphors were stronger when the concentration of doping ions was Mg/Y = 6%, Ca/Y = 4%, Sr/Y = 8%, Ba/Y = 2.5%, respectively. Its sequence of luminescent intensity from high to low is Sr > Ba > Mg > Ca.     

Thermal Shock Resistance of Al2 O3/ZrO2 (Y2O3) Composites

ZrO₂ containing 2% (mol fraction) Y₂O₃ and 3% (mol fraction) Y₂O₃ were added into Al₂O₃ matrix, compositing composites with 15% volume fraction of addictives mentioned above. The testing of property and analysis of SEM presented that, after vacuum sintering at 1550 °C, thermal shock resistance of two composites was superior to Al₂O₃ ceramic. The experiment showed that the properties of Al₂O₃ composites was higher than Al₂O₃ ceramic, and Al₂O₃/ZrO₂(3Y) was higher than Al₂O₃/ZrO₂(2Y) in thermal shock resistance. Improvement of thermal shock resistance of composites was attributed to many toughness machanisms of ZrO₂(Y₂O₃). By calculation, the fracture energy of Al₂O₃, Al₂O₃/ZrO₂ (2Y) and Al₂O₃/ZrO₂(3Y) was 38100.8 and 126.2 J·m⁻², respectively. Cracks initiation resistance (R') of Al₂O₃/ZrO₂(3Y) and Al₂O₃/ZrO₂(2Y) was higher than Al₂O₃ ceramic by 1.57 and 1.41 time, respectively, and cracks propagation resistance (R″″) was higher than Al₂O₃ ceramic by 1.46 and 1.38 time, respectively, which was corresponding to the results of residual strength.     

Investigation on the amounts of Na2CO3 and sulphur to obtain pure Y2O2S and up-conversion luminescence of Y2O2S:Er

The process to prepare pure phase of hexagonal Y2O2S was investigated. Effect of mixed flux of Na2CO3 and S amounts was studied. The phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the single phase of Y2O2S with smooth morphology could not be obtained as the molar ratio of Y2O3, Na2CO3 and S was in the range of 1:(0.5-1):(2-3) until the molar ratio was increased to 1:1.5:4. Different Er3+ concentration doped Y2O2S...     

Cathodic reduction process of Al–Cu–Y alloy in fluoride-oxide eutectic system via molten salt electrolysis

Al-Cu-Y alloys were prepared by molten salt electrolysis in fluoride-oxide system composed of electrolyte(Na_3 AlF_6-AlF_3-LiF-MgF_2) and oxide(Al_2 O_3-CuO-Y_2 O_3). Cathodic reduction process of Al_2 O_3,CuO and Y_2 O_3 were analyzed by cyclic voltammetry and chronoamperometry. Components and phase composition of alloy samples prepared by potentiostatic electrolysis were characterized by scanning electron microscopy and energy dispersive spectroscopy. The results show that the Al-Cu-Y alloy can be prepared in the AIF_3-NaF-5 wt%LiF-5 wt%MgF2(NaF/AlF_3 = 2.2, molecular ratio) eutectic system with mixed oxide(Al_2 O_3-CuO-Y_2 O_3) through 2 h at the conditions of a temperature of 1208 K, cell voltage3.0 V, cathode current density 0.7 A/cm~2. Al(Ⅲ) and Cu(Ⅱ) ions can be reduced to zero valence Al(0) and Cu(0) directly on carbonaceous electrode surface by instantaneous nucleation, respectively, the reduction process is controlled by diffusion. The reduction potential of Y(Ⅲ) ions is close to the active ions of fluoride melts, but strengthened phase AI3 Y can be formed through electrochemical reduction and alloyed process with active Al(Ⅲ) and Cu(Ⅱ) ions, meanwhile, the Al_2 Cu and Al_3 Y phases are distributed at the grain boundary of Al matrix.     

Application of annular centrifugal contactors in the extraction flowsheet for producing high purity yttrium

Compared with mixer-settlers applied widely in the hydrometallurgical industry of rare earths (RE), centrifugal contactors have several advantages such as low hold-up volume, excellent phase separation, high mass transfer efficiency, compact and short pieces of equipment, etc., and have been successfully used in some industrial fields. Yttrium (Y) is an important element and in great demand in many industries. For a variety of uses in many specialized areas, the high purity Y is often required. However, the separation and purification of Y by solvent extraction from RE mixture is widely known to be difficult due to their similar chemical properties. This paper studied both the separation factors of RE ions in the 32% HA (naphthenic acid) − 20% iso-octylalcohol–48% kerosene–RECl system and the distribution ratios of RE ions in the 32% HEHEHP (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) − 68% kerosene–RECl system. Based on these studies, an extraction flowsheet for producing high purity Y with HA and HEHEHP as extractants has been developed. Both the bench scale test and the pilot-plant test of the flowsheet have been performed with ϕ20 mm and ϕ120 mm centrifugal contactors respectively. It is shown that Y₂O₃ with 99.99% purity was obtained, and the total recovery of Y was about 95%.     

Production of high purity cobalt oxalate from spent ammonia cracker catalyst

A process was developed to produce > 99.9% pure cobalt oxalate from spent ammonia cracker catalyst pellets containing ∼ 20% Co generated at heavy water plants. A pilot plant for producing kilograms of cobalt oxalate of required purity has been set up. The process consists of leaching, oxidation, solvent extraction, ion exchange and oxalate precipitation. The major impurities present in the leach liquor after nitric acid oxidation were Fe³⁺, Al³⁺ and Ni²⁺. Fe³⁺ and Al³⁺ were separated from the leach liquor by using a solvent extraction (SX) process employing a mixed extractant system consisting of D2EHPA and TBP. Ni²⁺ was separated by ion exchange (IX) employing Dowex M4195 resin.     

First-principles study of structure,mechanical and optical properties of La-and Sc-doped Y_2O_3

The electronic,mechanical and optical properties of La-and Sc-doped Y_2O_3 were investigated using firstprinciples calculations.Two doping sites of Sc and La in Y_2O_3 were modeled.The calculated values of the energy of formation show that the most energetically favorable site for a La atom in Y_2O_3 is a d-site Y atom,while for Sc a b-site Y atom is the more stable position.The calculated band gap shows a slight decrease with increasing La or Sc concentration.The calculated results for the mechanical and optical properties of Y_(2-x)R_xO_3(R = Sc or La,0x ≤ 0.1875)show that La-or Sc-doped Y_2O_3 would have enhanced strength,and thus an ability of resisting external shocks,and increased hardness and mechanical toughness.These improved mechanical properties are achieved without sacrificing the optical properties of the doped compounds.So the doping of La or Sc in Y_2O_3 is permissible in the preparation of Y_2O_3 transparent ceramics,of course,doping of La or Sc will benefit the sintering of transparent ceramics.     

Continuous preparation of composition-controllable Y–Ni alloy in LiF–YF3–Y2O3 molten salt

The Y–Ni alloy is a primary precursor for the preparation of high-performance La–Y–Ni-based hydrogen storage materials. However, it cannot be produced continuously at low cost, which limits the wide popularization and application of La–Y–Ni-based materials. In this paper, this problem was solved perfectly using electrochemical reduction of Y₂O₃ in the LiF-YF₃ system. It is found that the reversible reduction from Y³⁺ to Y on the W electrode takes only one step, namely a significant soluble–soluble reaction controlled by Y³⁺ diffusion throughout the melt. Four typical signals of square wave voltammetry (SWV) corresponding to different kinds of Y–Ni intermetallic compounds are observed in LiF−YF₃ and LiF–YF₃–Y₂O₃ melts, and reduction potential can become positive with the addition of Y₂O₃, probably because of the formation of more complexes in the melts. Homogeneous Y–Ni alloy samples were produced continuously and prepared via galvanostatic electrolysis by using bargain-price raw material (Y₂O₃) and setting the current density at 10 A/cm² on the nickel electrode, before they were collected into a bottom receiver. A series of analyses including scanning electron microscopy-energy idspersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS), demonstrate that concentration of yttrium in Y–Ni alloy is adjustable within the wide range of 44 wt% to 72 wt% by fine-tuning the electrolysis temperature (875–1060 °C) in the LiF-YF₃ system to ensure the optimal hydrogen storage performance and economic efficiency of La–Y–Ni-based hydrogen-storage materials.     

Investigation of the structure of neodymium-di-(2-ethylhexyl) phosphoric acid combinations using electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry and nuclear magnetic resonance spectroscopy

Neodymium-di-(2-ethylhexyl) phosphoric acid (DEHPA) species forming in the organic phase during solvent extraction of neodymium with solutions of DEHPA have been studied. Two samples were prepared: one with a low molar ratio of neodymium to DEHPA, which is liquid and clear, and the other with a high molar ratio of neodymium to DEHPA (complete loading), which has the consistency of a gel. Electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometric investigations show numerous compounds, in addition to the generally assumed species dimeric DEHPA and Nd(DEHP-DEHPA)₃, in the liquid sample. The nuclear magnetic resonance (NMR) spectroscopic investigation of pure DEHPA and of completely loaded sample confirm the formula of pure DEHPA and of the organic part of Nd(DEHP)₃. Furthermore, chemical analysis of a dried, completely loaded sample also proves the existence of the species Nd(DEHP)₃. Results of X-ray powder diffraction measurements of this sample agree well with literature data.     

Current PM literature for engineers and users

Abstract

Transmission electron microscopy (TEM) as well as corresponding analytical techniques, such as high resolution TEM (HRTEM), energy dispersive X-ray (EDX) analysis, electron energy loss spectroscopy (EELS) and elemental mapping via a Gatan imaging filter (GIF), have been used to study the complex precipitation morphology of the commercial Fe–Cr–Al based oxide dispersion strengthened (ODS) alloy PM 2000. Formation of homogeneously distributed Y–Al–O ODS particles from Y₂O₃ added to the metal powder is shown. Besides these ODS particles, a large amount of complex Y–Al–O/Al₂O₃ and Y–Al–O/TiC as well as pure Al₂O₃ inclusions with sizes significantly larger than ODS particles have been identified. A typical feature is the growth of Al₂O₃ and Y–Al–O particles on the surface of small Ti(C,N) nuclei. Some implications of the results obtained from the mechanical properties of PM 2000 steel are discussed.     

Preparation of Al2O3/Y2O3 composite coating for deuterium permeation reduction

A tritium permeation barrier is required in fusion blankets for the reduction of fuel loss and radiological hazard. In this study, an Al₂O₃/Y₂O₃ composite coating was prepared on 316L stainless steel by radio-frequency magnetron sputtering in order to improve the tritium permeation resistance. The microstructure and the phase composition of the Al₂O₃/Y₂O₃ composite coating are observed by scanning electron microscopy, transmission electron microscopy and grazing incidence X-ray diffraction. Moreover, Auger electron spectroscopy was used to characterize the depth profiles of Al, Y and O elements. The results clearly indicate that the Al₂O₃/Y₂O₃ composite coating is fully dense and the total thickness is approximately 340 nm. The Al₂O₃/Y₂O₃ coating consists of an amorphous Al₂O₃ and the cubic Y₂O₃, in which Al, Y and O elements are homogeneously distributed in the vertical base direction. Furthermore, the deuterium permeation property of the Al₂O₃/Y₂O₃ composite coating was measured by the gas phase permeation method. The results show that the introduction of an interface and the existence of a tiny amount of micro-defects improve the deuterium resistance of the Al₂O₃/Y₂O₃ coating, and its deuterium permeation reduction factor is 536–750 at 873–973 K. Therefore, it is concluded that the Al₂O₃/Y₂O₃ composite coating as deuterium permeation barrier can significantly enhance the deuterium permeation resistance property.     

Technology of deep removal of impurities from scandium oxide with the acquisition of high-purity scandium oxide

A new production process for processing off-grade scandium oxide (98%) and scandium oxides 99.0 and 99.9 and the removal of impurities from them with the acquisition of high-purity scandium oxide 99.99% is developed and tested. This process is based on various solubilities of scandium formates and elements of impurities; it involves the dissolution of starting (98–99.8%) Sc₂O₃ in HCl, the processing of the solution with NH₄OH to pH = 5–7, filtering and washing the Sc(OH)₃ precipitate with water, repulpation in formic acid, separating the precipitate of scandium formate from the mother liquor, washing scandium formate with formic acid, and drying and calcinating it with the acquisition of Sc₂O₃ of the OS-99.99 grade.     

Chloride leaching of chalcopyrite

Two new process flowsheets have been developed which combine chloride leaching of copper from chalcopyrite with solvent extraction, to selectively transfer copper to a conventional sulfate electrowinning circuit. Chloride leaching with copper(II) as oxidant offers significant advantages for copper including increased solubility and increased rates of leaching. Both process flowsheets were similarly designed with a two stage counter-current leach but differ with respect to iron deportment. The goethite model flowsheet includes sparging of air or oxygen to the second leach stage to aid precipitation of iron as goethite (FeOOH). The hematite model flowsheet precipitates iron as hematite (Fe₂O₃) downstream from the leach in a dedicated autoclave. A mass balance has been completed for both process flowsheets and this determined the concentrations of copper and iron species in feed liquor returning to the leach following copper solvent extraction.The optimum leach extraction conditions were determined by varying grind size, temperature and residence time for both leach model scenarios. Leach tests were conducted using a chalcopyrite concentrate from Antamina in northern Peru, which contains a low to moderate amount of gangue material. The hematite model was also examined using a Rosario concentrate from Chile which contained chalcocite in addition to chalcopyrite and significant pyrite. Leach tests based on the hematite model were successful in achieving copper extractions > 95% in 4–6 h at 95 °C after fine grinding the concentrate (P₉₀ = 41 μm). However, copper extraction exceeded 99% from the finely ground Rosario concentrate (P₉₀ = 37 μm). In the goethite model leach tests, 89% copper extraction was achieved under optimum conditions in the atmospheric conditions tested.     

Preparation of Orange-Red Long Afterglow Phosphors Y2O2S:Sm3+, Mg2+, Ti4+

The orange-red long afterglow phosphors Y₂O₂S:Sm³⁺, Mg²⁺, Ti⁴⁺ was prepared by high temperature solid-state method. By XRD analysis, the crystal phase of the sample was Y₂O₂S, belonging to hexagonal system, and no new crystal phase arose when doping Sm³⁺, Mg²⁺, Ti⁴⁺. The characteristic peaks of excitation spectrum were located at 373, 388, 417, 430, 475 and 491 nm, and the characteristic peaks of emission spectrum were located at 571, 609 and 657 nm. The content of Sm³⁺ and doped ions Mg²⁺, Ti⁴⁺ affected the luminescent properties obviously, and Sm³⁺ affected the luminescent brightness mainly. Mg²⁺ and Ti⁴⁺ could deepen properly trap energy of Y₂O₂S crystal and strengthen its afterglow properties, the brightness and afterglow properties of sample were better when the mole ratio of Sm/Y, Mg/Y and Ti/Y is 1.4%, 1.25% and 0.9%, respectively.     

Preparation of Nano Y2O2 S：Eu Phosphor by Ethanol Assisted Combustion Synthesis Method

Y2O2S：Eu nano crystallines were prepared by a new ethanol assisted combustion synthesis method using sulfurcontained organic fuel in an ethanol-aqueous solution. The as-prepared nanocrystallines were characterized by X-ray diffraction, transmission electron microscope, photoluminescence spectra and X-ray luminescence spectra. It is shown that the assistant fuel ethanol has the effect of decreasing the water needed, simplifying the experiment procedure by dissolving rare earth nitrate and sulfur-contained organic fuel into an even solution, and prompting the formation of rare earth oxysulfide by igniting firstly during heating that leads to combustion decomposition reaction. Y2O2S ： Eu nano crystallines with strong photoluminescence and X-ray luminescence are obtained using thioacetamide as organic fuel. Mixtures of Y2O3 ： Eu and Y2O2S ： Eu are acquired using thiourea as fuel, and the content of Y2O2S ： Eu increases until reaches to about half of the Y2O3 ： Eu with the increasing amount of thiourea. Y2O2SO4 ： Eu emerges when S/Y = 6 and increases with increasing thiourea amount.     

Studies on the recovery of uranium from phosphoric acid medium using synergistic mixture of (2-Ethyl hexyl) Phosphonic acid,mono (2-ethyl hexyl) ester (PC88A) and Tri-n-butyl phosphate (TBP)

This paper describes the extraction of uranium from aqueous phosphoric acid medium using (2-Ethyl hexyl) Phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and tri-n-butyl phosphate (TBP) individually as well as their synergistic mixture in different diluents. The various experimental parameters are investigated to optimize optimise the suitable extraction conditions. Results indicate that a synergistic mixture of 0.90 M PC88A + 0.15 M TBP in xylene, can be used for the extraction of uranium from low phosphoric acid medium. Back extraction studies reveals that among all the common strippants used, 0.50 M solution of (NH₄)₂CO₃ was most suitable. The synergistic mixture of 0.90 M PC88A + 0.15 M TBP as extractant system and 0.5 M (NH₄)₂CO₃ as strippant is used to recover uranium from a conditioned wet process phosphoric acid and from actual radioanalytical waste generated during uranium analysis by modified Davies–Gray method. The recovery is found to be around 80% from conditioned WPA whereas better than 90% from modified Davies–Gray waste.     

Rare earth application for heat-resisting alloys

High-temperature oxidation resistance of Al₂O₃- and Cr₂O₃-forming heat-resisting alloys with rare earths (yttrium-implanted FeCrAl, -added FeCrAl, -added FeCrAlPt alloys, Y₂O₃- or CeO₂-coated NiCrSi, yttrium- or lutetium-added NiCr and NiCrSi) was studied in oxygen at high temperatures, by mass gain measurements, mass change measurements, amount of spalled oxide, observation of surface appearance, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe X-ray microanalysis (EPMA) and transmission electron microscopy (TEM). After oxidation at 1573 K for 18 ks in oxygen, oxide scale on FeCrAl alloy spalled from the entire surface, however, yttrium-implanted FeCrAl alloys showed good oxide adherence. After oxidation at 1473 K for 18 ks in oxygen, mass gain of FeCrAlY alloys decreased with increasing yttrium of up to 0.1 wt.% follwed by an increase with the yttrium content, and the mass gain of FeCrAl0.005Pt0.05Y alloy with appropriate additions of platinum and yttrium was lower than that of FeCrAl0.1Y alloy. Yttrium-added FeCrAl alloys showed good oxide adherence. TEM analysis revealed that the alumina/alloy interface of FeCrAl0.005Pt0.05Y alloy showed good coherency. The scale surface of FeCrAl alloy was rough, however, those of FeCrAlY and FeCrAlPtY alloys were smooth. Cyclic oxidation of NiCrSi, Y₂O₃- or CeO₂-coated NiCrSi alloys was studied up to 10 cycles (1 cycle: 300 s) at 1523 K in oxygen. Mass change of NiCrSi alloy increased up to 3 cycles and then decreased up to 10 cycles because of oxide spallation during cooling. On the other hand, mass change of Y₂O₃- or CeO₂-coated NiCrSi alloy increased up to 10 cycles, and these alloys showed good oxide adherence. Granular Cr₂O₃ particles on Y₂O₃-coated NiCrSi alloy were in size smaller than these on CeO₂-coated NiCrSi alloy. This result suggested that oxidation rate of Y₂O₃-coated NiCrSi alloy was lower than that of CeO₂-coated NiCrSi alloy. After oxidation at 1473 and 1573 K for 18 ks in oxygen, mass gain of yttrium- or lutetium-added NiCr and NiCrSi alloys decreased. Oxide scales on NiCrSi alloy markedly spalled along with alloy grain boundaries during cooling. On the other hand, yttrium- or lutetium-added NiCrSi alloys showed good oxide adherence. Granular Cr₂O₃ particles on yttrium- or lutetium-added NiCr and NiCrSi alloys decreased in size with increasing yttrium or lutetium, and increased with increasing oxidation temperature.     

Effect of Superficially Applied Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Coating on High-Temperature Corrosion Behavior of Ni-Base Superalloys

Inhibitors and oxide additives have been investigated with varying success to control high-temperature corrosion. Effect of Y₂O₃ on high-temperature corrosion of Superni 718 and Superni 601 superalloys was investigated in the Na₂SO₄-60 pct V₂O₅ environment at 1173 K (900 °C) for 50 cycles. Y₂O₃ was applied as a coating on the surfaces of the specimens. Superni 601 was found to have better corrosion resistance in comparison with Superni 718 in the Na₂SO₄-60 pct V₂O₅ environment. The Y₂O₃ superficial coating was successful in decreasing the reaction rate for both the superalloys. In the oxide scale of the alloy Superni 601, Y and V were observed to coexist, thereby indicating the formation of a protective YVO₄ phase. There was a distinct presence of a protective Cr₂O₃-rich layer just above the substrate/scale interface in the alloy. Whereas Cr₂O₃ was present with Fe and Ni in the scale of Superni 718. Y₂O₃ seemed to be contributing to better adhesion of the scale, as comparatively lesser spalling was noticed in the presence of Y₂O₃.