This study investigated the microstructure and hydrogen absorption properties of a rare-earth high-entropy alloy(HEA),YGdTbDyHo.Results indicated that the YGdTbDyHo alloy had a microstructure of equiaxed grains,with t...This study investigated the microstructure and hydrogen absorption properties of a rare-earth high-entropy alloy(HEA),YGdTbDyHo.Results indicated that the YGdTbDyHo alloy had a microstructure of equiaxed grains,with the alloy elements distributed homogeneously.Upon hydrogen absorption,the phase structure of the HEA changed from a solid solution with an hexagonal-close-packed(HCP)structure to a high-entropy hydride with an faced-centered-cubic(FCC)structure without any secondary phase precipitated.The alloy demonstrated a maximum hydrogen storage capacity of 2.33 H/M(hydrogen atom/metal atom)at 723 K,with an enthalpy change(ΔH)of-141.09 kJ·mol^(-1)and an entropy change(ΔS)of-119.14 J·mol^(-1)·K^(-1).The kinetic mechanism of hydrogen absorption was hydride nucleation and growth,with an apparent activation energy(E_(a))of 20.90 kJ·mol^(-1).Without any activation,the YGdTbDyHo alloy could absorb hydrogen quickly(180 s at 923 K)with nearly no incubation period observed.The reason for the obtained value of 2.33 H/M was that the hydrogen atoms occupied both tetrahedral and octahedral interstices.These results demonstrate the potential application of HEAs as a high-capacity hydrogen storage material with a large H/M ratio,which can be used in the deuterium storage field.展开更多
High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of th...High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical current.In this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench.The temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature.The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result.The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC.The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC.Finally,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed.These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.展开更多
To overcome the limitation in formability at room temperature,manufacturers have developed magnesium alloys with remarkable properties by adding rare-earth elements.The rare-earth magnesium alloys behave differently f...To overcome the limitation in formability at room temperature,manufacturers have developed magnesium alloys with remarkable properties by adding rare-earth elements.The rare-earth magnesium alloys behave differently from the conventional alloys,especially with respect to their coupled anisotropic and strain rate sensitive behavior.In the current work,such behavior of the rare-earth Mg alloy ZEK100 sheet at room temperature is investigated with the aid of the elastic viscoplastic self-consistent polycrystal plasticity model.Different strain rate sensitivities(SRSs)for various deformation modes are employed by the model to simulate the strain rate sensitive behaviors under different loading directions and loading rates.Good agreement between the experiments and simulations reveals the importance and necessity of using different SRSs for each deformation mode in hexagonal close-packed metals.Furthermore,the relative activities of each deformation mode and the texture evolution during different loadings are discussed.The anisotropic and strain rate sensitive behavior is ascribed to the various operating deformation modes with different SRSs during loading along different directions.展开更多
Ion-absorbed rare-earth ore is an important mineral resource which is widely extracted by in-situ leaching process. And such process generates a significant amount of impurities such as aluminum and iron ions in leach...Ion-absorbed rare-earth ore is an important mineral resource which is widely extracted by in-situ leaching process. And such process generates a significant amount of impurities such as aluminum and iron ions in leaching solution simultaneously. The surface characteristics and interactions by infrared spectroscopy and X-ray diffraction were studied to optimize the leaching conditions. It is found that the environment-friendly depressant LG-01 can react with the impurity ions through the formation of a new complex on the surface of leaching residues. Thus, it reduces significantly the concentration of impurity ions in leaching solution and improves the leaching rate of rare-earth ore. Moreover, a leaching rate of 95.6% and an impurity removal rate of 92% have been achieved under the optimized conditions.展开更多
During the past decades,with the increasing demands in lightweight structural materials,Mg alloys with low density and high performance have been extensively investigated and partly applied in some industries.Especial...During the past decades,with the increasing demands in lightweight structural materials,Mg alloys with low density and high performance have been extensively investigated and partly applied in some industries.Especially when rare earth(RE)elements are added as major alloying elements to Mg alloys,the alloy strength and creep resistance are greatly improved,which have promoted several series of Mg-RE alloys.This paper reviews the progress and developments of high-performance Mg-RE alloys in recent years with emphasis on cast alloys.The main contents include the alloy design,melt purification,grain refinement,castability,novel liquid casting and semisolid forming approaches,and the industrial applications or trials made of Mg-RE alloys.The review will provide insights for future developments of new alloys,techniques and applications of Mg alloys.展开更多
Throught fusion of the mechanism modeling and the neural networks modeling,a compo- nent content soft-sensor,which is composed of the equilibrium calculation model for multi-component rare earth extraction and the err...Throught fusion of the mechanism modeling and the neural networks modeling,a compo- nent content soft-sensor,which is composed of the equilibrium calculation model for multi-component rare earth extraction and the error compensation model of fuzzy system,is proposed to solve the prob- lem that the component content in countercurrent rare-earth extraction process is hardly measured on-line.An industry experiment in the extraction Y process by HAB using this hybrid soft-sensor proves its effectiveness.展开更多
Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy p...Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.展开更多
The hadal zone represents one of the last great frontiers in modern marine science,and deciphering the provenance of sediment that is supplied to these trench settings remains a largely unanswered question.Here,we exa...The hadal zone represents one of the last great frontiers in modern marine science,and deciphering the provenance of sediment that is supplied to these trench settings remains a largely unanswered question.Here,we examine the mineralogical and geochemical composition of a sediment core(core CD-1)that was recovered from the southwestern margin of the Challenger Deep within the Mariana Trench.Major element abundances and rare-earth element patterns from these sediments require inputs from both terrigenous dust and locally sourced volcanic debris.We exploit a two-endmember mixing model to demonstrate that locally sourced volcanic material dominates the sediment supply to the Challenger Deep(averaging^72%).The remainder,however,is supplied by aeolian dust(averaging^28%),which is consistent with adjacent studies that utilized Sr-Nd isotopic data.Building on a growing database,we strengthen our understanding of Asian aeolian dust input into the northwestern Pacific,which ultimately improves our appreciation of sedimentation in,and around,the hadal zone.展开更多
A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of ...A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both∑REE and∑LREE （LREE is short for light-group REEs） fluctuate in a relatively wide range, while∑HREE （HREE is short for heavy-group REEs） maintains a relatively stable level. With the stratigraphic chronology becoming newer, both∑REE and∑LREE show a gradually rising trend overall. The∑REE of the core is relatively high from the bottom of Yacheng Formation （at a well depth of 4 207 m） to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China＇s neritic sediments and loess, with significant ＂continental ori-entation＂. The∑REE of the core is relatively low in the lower part of Yacheng Formation （at a well depth of 4 207-4 330 m）, as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrich-ment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift ar-eas; the continental margin materials from the north contributed only insignificantly; the provenance devel-oped to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement （34-25 Ma BP, early expansion of the South China Sea）, Baiyun Movement （23 Ma BP）, late expansion movement （23.5-16.5 Ma BP）, expansion-settlement transition, and other important events are all clearly recorded by the geochemi-cal characteristics of REEs in the core.展开更多
Structural and mechanical properties of several rare-earth diborides were systematically investigated by first principles calculations. Specifically, we studied XB2 , where X=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu in ...Structural and mechanical properties of several rare-earth diborides were systematically investigated by first principles calculations. Specifically, we studied XB2 , where X=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu in the hexagonal AlB2 , ReB2 , and orthorhombic OsB2 -type structures. The lattice parameters, bulk modulus, bond distances, second order elastic constants, and related polycrystalline elastic moduli （e.g., shear modulus, Young’s modulus, Poisson’s ratio, Debye temperature, sound velocities） were calculated. Our results indicate that these compounds are mechanically stable in the considered structures, and according to ＂Chen’s method＂, the predicted Vickers hardness shows that they are hard materials in AlB2 - and OsB2 -type structures.展开更多
Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catal...Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal＇s dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.展开更多
Due to their low symmetry in crystal structure,low elastic modulus(~45 GPa)and low yielding stress,magnesium(Mg)alloys exhibit strong inelastic behaviors during unloading.As more and more Mg alloys are developed,their...Due to their low symmetry in crystal structure,low elastic modulus(~45 GPa)and low yielding stress,magnesium(Mg)alloys exhibit strong inelastic behaviors during unloading.As more and more Mg alloys are developed,their unloading behaviors were less investigated,especially for rare-earth(RE)Mg alloys.In the current work,the unloading behaviors of the RE Mg alloy ZE10 sheet is carefully studied by both mechanical tests and crystal plasticity modeling.In terms of the stress-strain curves,the inelastic strain,the chord modulus,and the active deformation mechanisms,the substantial anisotropy and the loading path dependency of the unloading behaviors of ZE10 sheets are characterized.The inelastic strains are generally larger under compressive Loading-Un Loading(L-UL)than under tensile L-UL,along the transverse direction(TD)than along the rolling direction(RD)under tensile L-UL,and along RD than along TD under compressive L-UL.The basal slip,twinning and de-twinning are found to be responsible for the unloading behaviors of ZE10 sheets.展开更多
A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. T...A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.展开更多
This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma...This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.展开更多
The structure of LiSrY2（BO3）3 has been solved by single-crystal X-ray diffraction analysis at 298 and 113 K on different diffractometers.It crystallizes in trigonal with space group P-3m1（No.164）.The cell paramete...The structure of LiSrY2（BO3）3 has been solved by single-crystal X-ray diffraction analysis at 298 and 113 K on different diffractometers.It crystallizes in trigonal with space group P-3m1（No.164）.The cell parameters at room temperature are as follows：a = 10.3345（9）,c = 6.4049（11） ,V = 592.41（13） 3,Z = 3,Mr = 448.81,F（000） = 618,μ = 21.327 mm-1 and Dc = 3.774 g/cm3.The crystal structure consists of gear-like [BY6O33] groups which are linked together by corner-sharing to form a two-dimensional layer parallel to the ab plane.These layers are connected one after another by sharing oxygen atoms with B（2） atoms along the c direction to construct a three-dimensional framework.Li and Sr atoms just occupy the cavities formed by oxygen atoms.In addition,the vibrational spectroscopy of LiSrY2（BO3）3 and photoluminescence properties of the Eu3＋ doped LiSrY2（BO3）3 were also studied.展开更多
Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stab...Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stability, and mechanical properties of Cu46Zr47-xA17Mx were investigated. The GFA of Cu46Zr47-xA17Mx （M = Ce, Pr） alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47-xA17Thx（X = 2, 4, and 5） amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47-xA17Gdx（x = 2, 4, and 5） increases with increasing Gd. Tx and Tp of all decrease. Tg is dependent on the rare-earth element and its content. ATx for most of these alloys decreases except the Cu46Zra2Al7Gd5 alloy. The activation energies △Eg, △Ex, and △Ep for the Cu46Zr42A17Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respec- tively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43A17Pr4 alloy presents the least, Hv 479. The compressive strength （at.f.） of the Cu46Zra3A17Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.展开更多
The corrosion resistance of three Mg alloys containing rare-earth elements(WE43,EV31 and ZE41)was studied and compared to that of two Mg-Al alloys(AZ31 and AZ91)and of pure Mg(99.95 wt.%).Current-voltage curves and el...The corrosion resistance of three Mg alloys containing rare-earth elements(WE43,EV31 and ZE41)was studied and compared to that of two Mg-Al alloys(AZ31 and AZ91)and of pure Mg(99.95 wt.%).Current-voltage curves and electrochemical impedance measurements were performed with rotating disk electrodes in an aerated 0.1 M Na_(2)SO_(4)solution.For all the alloys,it was confirmed that the intermetallic particles acted as local cathodes and that more protective films were formed on the alloys surface by comparison with the pure Mg.Corrosion rates were determined from inductive coupled plasma-optical emission spectroscopy measurements and from the electrochemical measurements.Higher corrosion rates were observed for the rare-earth Mg alloys compared to the AZ series alloys.These data allowed the corrosion mechanisms to be discussed.展开更多
The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can b...The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can be easily produced between these three elements in the filler metal, which greatly limited the formation of the isolated phase Pb or Bi and also eliminated the bad effect of impurity elements Pb and Bi on the spreading property of Ag-based filler metal. The metallurgical and quantum-mechanical bond formation analysis show that a strong chemical affinity was existed between the rare-earth element Ce and impurity elements Pb and Bi, which was proved by the XRD analysis results.展开更多
Magnetic separation of iron in rare-earth tailings was achieved by magnetizing roast process with coal as reductant. Effects of the temperature, carbon to oxygen ratio, and cooling type on magnetic susceptibility and ...Magnetic separation of iron in rare-earth tailings was achieved by magnetizing roast process with coal as reductant. Effects of the temperature, carbon to oxygen ratio, and cooling type on magnetic susceptibility and composition of rare-earth tailings were investigated. The results show that roast conditions with the temperature of 650℃, carbon to oxygen ratio of 3.85, and holding time of 2.5 h are in favor of reduction of Fe_2O_3 to Fe_3O_4 when the roasted rare-earth tailings is cooled along with furnace. Under these roast conditions, magnetic susceptibility of rare-earth tailings is 2.36 that is very close to theoretical value（2.33）. However, magnetic separation results of iron in rare-earth tailings cooled along with furnace are not satisfactory. Through comparing magnetic separation results of iron in rare-earth tailings cooled by different ways, it is found that water cooling is more favored of magnetic separation of iron in the roasted rare-earth tailings than furnace cooling and air cooling. Grade and recovery of iron in concentrate from rare-earth tailings cooled by water are 45.00%-49.00% and 65.00%-77.50%, respectively.展开更多
The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis aci...The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice.According to the results of several complementary techniques,i.e.,temperature-programmed surface reactions,in situ diffuse reflectance infrared Fourier transform spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail.Density functional theory calculations revealed that aldol dehydration was the rate-limiting step.The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration.Lewis acidic Y(OSi)(OH)2 stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.21171018 and 51271021)the State Key Laboratory for Advanced Metals and Materials。
文摘This study investigated the microstructure and hydrogen absorption properties of a rare-earth high-entropy alloy(HEA),YGdTbDyHo.Results indicated that the YGdTbDyHo alloy had a microstructure of equiaxed grains,with the alloy elements distributed homogeneously.Upon hydrogen absorption,the phase structure of the HEA changed from a solid solution with an hexagonal-close-packed(HCP)structure to a high-entropy hydride with an faced-centered-cubic(FCC)structure without any secondary phase precipitated.The alloy demonstrated a maximum hydrogen storage capacity of 2.33 H/M(hydrogen atom/metal atom)at 723 K,with an enthalpy change(ΔH)of-141.09 kJ·mol^(-1)and an entropy change(ΔS)of-119.14 J·mol^(-1)·K^(-1).The kinetic mechanism of hydrogen absorption was hydride nucleation and growth,with an apparent activation energy(E_(a))of 20.90 kJ·mol^(-1).Without any activation,the YGdTbDyHo alloy could absorb hydrogen quickly(180 s at 923 K)with nearly no incubation period observed.The reason for the obtained value of 2.33 H/M was that the hydrogen atoms occupied both tetrahedral and octahedral interstices.These results demonstrate the potential application of HEAs as a high-capacity hydrogen storage material with a large H/M ratio,which can be used in the deuterium storage field.
基金Project supported by the National Natural Science Foundation of China(Nos.12302278,U2241267,12172155,and 11932008)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2022-48)the Natural Science Foundation of Gansu Province of China(No.24JRRA473)。
文摘High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical current.In this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench.The temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature.The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result.The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC.The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC.Finally,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed.These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.
基金supported by the National Natural Science Foundation of China(No.51975365)the Shanghai Pujiang Program(18PJ1405000)+1 种基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)the Province of Ontario
文摘To overcome the limitation in formability at room temperature,manufacturers have developed magnesium alloys with remarkable properties by adding rare-earth elements.The rare-earth magnesium alloys behave differently from the conventional alloys,especially with respect to their coupled anisotropic and strain rate sensitive behavior.In the current work,such behavior of the rare-earth Mg alloy ZEK100 sheet at room temperature is investigated with the aid of the elastic viscoplastic self-consistent polycrystal plasticity model.Different strain rate sensitivities(SRSs)for various deformation modes are employed by the model to simulate the strain rate sensitive behaviors under different loading directions and loading rates.Good agreement between the experiments and simulations reveals the importance and necessity of using different SRSs for each deformation mode in hexagonal close-packed metals.Furthermore,the relative activities of each deformation mode and the texture evolution during different loadings are discussed.The anisotropic and strain rate sensitive behavior is ascribed to the various operating deformation modes with different SRSs during loading along different directions.
基金Project(51164010)supported by the National Natural Science Foundation of ChinaProject(2010GZC0048)supported by the Natural Science Foundation of Jiangxi Province,China
文摘Ion-absorbed rare-earth ore is an important mineral resource which is widely extracted by in-situ leaching process. And such process generates a significant amount of impurities such as aluminum and iron ions in leaching solution simultaneously. The surface characteristics and interactions by infrared spectroscopy and X-ray diffraction were studied to optimize the leaching conditions. It is found that the environment-friendly depressant LG-01 can react with the impurity ions through the formation of a new complex on the surface of leaching residues. Thus, it reduces significantly the concentration of impurity ions in leaching solution and improves the leaching rate of rare-earth ore. Moreover, a leaching rate of 95.6% and an impurity removal rate of 92% have been achieved under the optimized conditions.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.51775334,51821001 and 51701124)National Key Research and Development Program of China(Grant No.2016YFB0701205)+3 种基金China Postdoctoral Science Foundation(Grant No.2020M671360)Natural Science Foundation for Young of Jiangsu Province(Grant No.BK20190863)Jiangsu“Mass Innovation and Entrepreneurship”Talent Program(Shuang Chuang Ph.Ds,2018)Open Research Fund of the State Key Laboratory of Metal Matrix Composites(Grant No.sklmmc-kf18-08).
文摘During the past decades,with the increasing demands in lightweight structural materials,Mg alloys with low density and high performance have been extensively investigated and partly applied in some industries.Especially when rare earth(RE)elements are added as major alloying elements to Mg alloys,the alloy strength and creep resistance are greatly improved,which have promoted several series of Mg-RE alloys.This paper reviews the progress and developments of high-performance Mg-RE alloys in recent years with emphasis on cast alloys.The main contents include the alloy design,melt purification,grain refinement,castability,novel liquid casting and semisolid forming approaches,and the industrial applications or trials made of Mg-RE alloys.The review will provide insights for future developments of new alloys,techniques and applications of Mg alloys.
基金Supported by National Natural Science Foundation of P.R.China(50474020,60534010,60504006)
文摘Throught fusion of the mechanism modeling and the neural networks modeling,a compo- nent content soft-sensor,which is composed of the equilibrium calculation model for multi-component rare earth extraction and the error compensation model of fuzzy system,is proposed to solve the prob- lem that the component content in countercurrent rare-earth extraction process is hardly measured on-line.An industry experiment in the extraction Y process by HAB using this hybrid soft-sensor proves its effectiveness.
基金supported by the National Basic Research Program of China(No.2010CB934601)the National Natural Science Foundation of China(NSFC)(Nos.51125001,51172005,and 90922033)+1 种基金the Doctoral Program(No.20120001110078)the Natural Science Foundation of Beijing(No.2122022)
文摘Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB06020204)the National Key Basic Research and Development Program of China(Nos.2017YFC0307704,2017YFC0307600)the Marine Geological Survey Program of China Geological Survey(No.DD20160218)
文摘The hadal zone represents one of the last great frontiers in modern marine science,and deciphering the provenance of sediment that is supplied to these trench settings remains a largely unanswered question.Here,we examine the mineralogical and geochemical composition of a sediment core(core CD-1)that was recovered from the southwestern margin of the Challenger Deep within the Mariana Trench.Major element abundances and rare-earth element patterns from these sediments require inputs from both terrigenous dust and locally sourced volcanic debris.We exploit a two-endmember mixing model to demonstrate that locally sourced volcanic material dominates the sediment supply to the Challenger Deep(averaging^72%).The remainder,however,is supplied by aeolian dust(averaging^28%),which is consistent with adjacent studies that utilized Sr-Nd isotopic data.Building on a growing database,we strengthen our understanding of Asian aeolian dust input into the northwestern Pacific,which ultimately improves our appreciation of sedimentation in,and around,the hadal zone.
基金The National Major Project of Science and Technology of China under contract No.2011ZX05025-002-03
文摘A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both∑REE and∑LREE （LREE is short for light-group REEs） fluctuate in a relatively wide range, while∑HREE （HREE is short for heavy-group REEs） maintains a relatively stable level. With the stratigraphic chronology becoming newer, both∑REE and∑LREE show a gradually rising trend overall. The∑REE of the core is relatively high from the bottom of Yacheng Formation （at a well depth of 4 207 m） to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China＇s neritic sediments and loess, with significant ＂continental ori-entation＂. The∑REE of the core is relatively low in the lower part of Yacheng Formation （at a well depth of 4 207-4 330 m）, as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrich-ment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift ar-eas; the continental margin materials from the north contributed only insignificantly; the provenance devel-oped to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement （34-25 Ma BP, early expansion of the South China Sea）, Baiyun Movement （23 Ma BP）, late expansion movement （23.5-16.5 Ma BP）, expansion-settlement transition, and other important events are all clearly recorded by the geochemi-cal characteristics of REEs in the core.
文摘Structural and mechanical properties of several rare-earth diborides were systematically investigated by first principles calculations. Specifically, we studied XB2 , where X=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu in the hexagonal AlB2 , ReB2 , and orthorhombic OsB2 -type structures. The lattice parameters, bulk modulus, bond distances, second order elastic constants, and related polycrystalline elastic moduli （e.g., shear modulus, Young’s modulus, Poisson’s ratio, Debye temperature, sound velocities） were calculated. Our results indicate that these compounds are mechanically stable in the considered structures, and according to ＂Chen’s method＂, the predicted Vickers hardness shows that they are hard materials in AlB2 - and OsB2 -type structures.
基金supported by the National Natural Science Foundation of China (No. 20776016 and 21006005)
文摘Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal＇s dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.
基金the support of the National Natural Science Foundation of China(Nos.51775337,51675331,51975365)Major Projects of the Ministry of Education(No.311017)+5 种基金the Program of Introducing Talents of Discipline to Universities(Grant No.B06012)sponsored by the Shanghai Pujiang Program(18PJ1405000)the University of Sydney-Shanghai Jiao Tong University Partnership Collaboration Awardssupported by the Natural Sciences and Engineering Research Council of Canada(Nos.RGPIN-201606464)partly supported by the Materials Genome Initiative Center,Shanghai Jiao Tong UniversityThe University of Michigan and Shanghai Jiao Tong University(UM-SJTU)joint research project(AE604401)。
文摘Due to their low symmetry in crystal structure,low elastic modulus(~45 GPa)and low yielding stress,magnesium(Mg)alloys exhibit strong inelastic behaviors during unloading.As more and more Mg alloys are developed,their unloading behaviors were less investigated,especially for rare-earth(RE)Mg alloys.In the current work,the unloading behaviors of the RE Mg alloy ZE10 sheet is carefully studied by both mechanical tests and crystal plasticity modeling.In terms of the stress-strain curves,the inelastic strain,the chord modulus,and the active deformation mechanisms,the substantial anisotropy and the loading path dependency of the unloading behaviors of ZE10 sheets are characterized.The inelastic strains are generally larger under compressive Loading-Un Loading(L-UL)than under tensile L-UL,along the transverse direction(TD)than along the rolling direction(RD)under tensile L-UL,and along RD than along TD under compressive L-UL.The basal slip,twinning and de-twinning are found to be responsible for the unloading behaviors of ZE10 sheets.
基金Supported by the 985 Foundation of Central University for Nationalities（CUN985-3-3） the National Natural Science Foundation of China（90305011）
文摘A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.
文摘This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.
基金supported by the Major Research Project of Xi’an University of Arts and Science (No.zd200906)the Special Fund of Education Committee of Shaanxi Province (No.09JK743)
文摘The structure of LiSrY2（BO3）3 has been solved by single-crystal X-ray diffraction analysis at 298 and 113 K on different diffractometers.It crystallizes in trigonal with space group P-3m1（No.164）.The cell parameters at room temperature are as follows：a = 10.3345（9）,c = 6.4049（11） ,V = 592.41（13） 3,Z = 3,Mr = 448.81,F（000） = 618,μ = 21.327 mm-1 and Dc = 3.774 g/cm3.The crystal structure consists of gear-like [BY6O33] groups which are linked together by corner-sharing to form a two-dimensional layer parallel to the ab plane.These layers are connected one after another by sharing oxygen atoms with B（2） atoms along the c direction to construct a three-dimensional framework.Li and Sr atoms just occupy the cavities formed by oxygen atoms.In addition,the vibrational spectroscopy of LiSrY2（BO3）3 and photoluminescence properties of the Eu3＋ doped LiSrY2（BO3）3 were also studied.
文摘Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stability, and mechanical properties of Cu46Zr47-xA17Mx were investigated. The GFA of Cu46Zr47-xA17Mx （M = Ce, Pr） alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47-xA17Thx（X = 2, 4, and 5） amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47-xA17Gdx（x = 2, 4, and 5） increases with increasing Gd. Tx and Tp of all decrease. Tg is dependent on the rare-earth element and its content. ATx for most of these alloys decreases except the Cu46Zra2Al7Gd5 alloy. The activation energies △Eg, △Ex, and △Ep for the Cu46Zr42A17Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respec- tively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43A17Pr4 alloy presents the least, Hv 479. The compressive strength （at.f.） of the Cu46Zra3A17Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.
基金The authors gratefully acknowledge the IRT Saint-Exupery Surfinnov project partners,especially Mapaero and Prodem companies,for the financial support.
文摘The corrosion resistance of three Mg alloys containing rare-earth elements(WE43,EV31 and ZE41)was studied and compared to that of two Mg-Al alloys(AZ31 and AZ91)and of pure Mg(99.95 wt.%).Current-voltage curves and electrochemical impedance measurements were performed with rotating disk electrodes in an aerated 0.1 M Na_(2)SO_(4)solution.For all the alloys,it was confirmed that the intermetallic particles acted as local cathodes and that more protective films were formed on the alloys surface by comparison with the pure Mg.Corrosion rates were determined from inductive coupled plasma-optical emission spectroscopy measurements and from the electrochemical measurements.Higher corrosion rates were observed for the rare-earth Mg alloys compared to the AZ series alloys.These data allowed the corrosion mechanisms to be discussed.
文摘The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can be easily produced between these three elements in the filler metal, which greatly limited the formation of the isolated phase Pb or Bi and also eliminated the bad effect of impurity elements Pb and Bi on the spreading property of Ag-based filler metal. The metallurgical and quantum-mechanical bond formation analysis show that a strong chemical affinity was existed between the rare-earth element Ce and impurity elements Pb and Bi, which was proved by the XRD analysis results.
基金Project(2012CBA01205)supported by National Basic Research Program of ChinaProjects(50934004,51274061)supported by the National Natural Science Foundation of ChinaProject(N110502002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Magnetic separation of iron in rare-earth tailings was achieved by magnetizing roast process with coal as reductant. Effects of the temperature, carbon to oxygen ratio, and cooling type on magnetic susceptibility and composition of rare-earth tailings were investigated. The results show that roast conditions with the temperature of 650℃, carbon to oxygen ratio of 3.85, and holding time of 2.5 h are in favor of reduction of Fe_2O_3 to Fe_3O_4 when the roasted rare-earth tailings is cooled along with furnace. Under these roast conditions, magnetic susceptibility of rare-earth tailings is 2.36 that is very close to theoretical value（2.33）. However, magnetic separation results of iron in rare-earth tailings cooled along with furnace are not satisfactory. Through comparing magnetic separation results of iron in rare-earth tailings cooled by different ways, it is found that water cooling is more favored of magnetic separation of iron in the roasted rare-earth tailings than furnace cooling and air cooling. Grade and recovery of iron in concentrate from rare-earth tailings cooled by water are 45.00%-49.00% and 65.00%-77.50%, respectively.
文摘The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice.According to the results of several complementary techniques,i.e.,temperature-programmed surface reactions,in situ diffuse reflectance infrared Fourier transform spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail.Density functional theory calculations revealed that aldol dehydration was the rate-limiting step.The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration.Lewis acidic Y(OSi)(OH)2 stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.
