This study delved into the corrosion behavior of ZK60 Mg alloy in saturated NaCl solution,particularly focusing on the effects of the addition of rare earth oxide,namely CeO_(2)(forming ZKC alloy)and La_(2)O_(3)(formi...This study delved into the corrosion behavior of ZK60 Mg alloy in saturated NaCl solution,particularly focusing on the effects of the addition of rare earth oxide,namely CeO_(2)(forming ZKC alloy)and La_(2)O_(3)(forming ZKL alloy).The results indicate that the introduction of CeO_(2)and La_(2)O_(3)promotes the precipita-tion of T-(Mg_(1−x),Zn_(x))_(11)RE phases(Mg-Zn-RE phases,where RE represents Ce or La)at grain boundaries.The presence and distribution pattern of the T-phase have a profound impact on the corrosion resis-tance of the Mg alloy.Specifically,the ZKC alloy exhibits the most outstanding corrosion resistance.This superior performance is attributed to the uniform distribution of(Mg_(1−x),Zn_(x))_(11)Ce phase at grain bound-aries in ZK60-0.5 wt%CeO_(2),effectively hindering the penetration of corrosive media into the matrix.Additionally,scanning kelvin probe force microscopy(SKPFM)analysis reveals that the(Mg_(1−x),Zn_(x))_(11)Ce phase exhibits the smallest potential difference with the matrix,significantly mitigating the tendency for galvanic corrosion.In contrast,the ZKL alloy displays less precipitation and uneven distribution of the(Mg_(1−x),Zn_(x))_(11)La phase,resulting in inferior corrosion resistance compared to the ZKC alloy.The dispar-ities in the precipitation of the two phases,as derived from first-principles calculations,stem from the spontaneous reduction of CeO_(2)under Mg conditions,whereas the reduction reaction between La_(2)O_(3)and Mg cannot proceed spontaneously.Furthermore,SKPFM analysis and CALPHAD method found that as the addition of CeO_(2)/La_(2)O_(3)increases,the atomic ratio of Zn in the Mg-Zn-RE ternary phase rises,accompa-nied by an increase in the potential difference between the Mg-Zn-RE phase and the Mg matrix.This suggests that fine-tuning the addition of rare earth oxides can modify the atomic ratio of the Mg-Zn-RE ternary phase,thereby enhancing the corrosion resistance of the Mg alloy.In summary,this study not only unravels the specific mechanisms of how CeO_(2)and La_(2)O_(3)affect the corrosion behavior of ZK60 Mg alloy but also provides new strategies and insights for the development of low-cost,high-performance corrosion-resistant Mg alloy materials.展开更多
The flux cored wires with different amounts of rare earth （RE） oxides additions for hardfacing （harden-face-welding） the workpieces of high chromium cast iron were studied in this work.The morphology of carbides i...The flux cored wires with different amounts of rare earth （RE） oxides additions for hardfacing （harden-face-welding） the workpieces of high chromium cast iron were studied in this work.The morphology of carbides in hardfacing metal was observed,and the type of the carbides was determined by optical microscopy,scanning electron microscopy （SEM）,energy dispersive spectrometer （EDS） and X-ray diffraction （XRD）.Based on the data of effect of RE on carbides morphology,the refined reason for carbide by RE oxide was discussed with the misfit theory.The results showed that,the microstructure of hardfacing metal was composed of martensite,residual austenite and M7C3 carbides.With the increasing amount of RE oxide additions,the volume fraction and roundness of the carbides were increased,however,the area and perimeter of carbides were decreased.It indicated that carbides in hardfacing metal could be refined and spheroidized by adding RE oxides in flux cored wires.展开更多
The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive...The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...展开更多
Rare earth （La, Nd and Tb） oxides with one-dimensional micro/nanostmcatres were synthesized hydrothermally under facile and mild conditions with two surfactants, and characterized by X-ray diffraction （XRD）, therm...Rare earth （La, Nd and Tb） oxides with one-dimensional micro/nanostmcatres were synthesized hydrothermally under facile and mild conditions with two surfactants, and characterized by X-ray diffraction （XRD）, thermal gravimetry （TG）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and photoluminescence. The results showed that the synthesized rare earth oxides behaved regular nano- and micro-scale structures. And the morphologies of samples depended on the radii of rare earth ions, with the help of two sur- factants of sodium dodecyl sulfonic and PEG 600. Nanocrystalline La2O3：Eu^3＋ possessed good photoluminescence （PL） property and might be used as a nanosized phosphor, its PL intensity was akered by the doping Eu^3＋ concentration and the optimum concentration of Eu^3＋ was 3 mol.%. In comparison with bulk Eu^3＋/La2O3, Eu^3＋/nano-La2O3 showed better photoluminescence property, nearly equal to that of nanocrtstalline La2O3：Eu^3＋. Tb4O7 microwires showed interesting photoluminescence properties.展开更多
Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sin...Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sintering resistance,and thermo-physical properties of the doped hafnia ceramics were investigated.Results show that the Gd-Y,Yb-Y or Gd-Yb-Y co-doped hafnia ceramics remain the same defect fluorite(F)structure,while the La-Yb-Y co-doped hafnia revealing coexistence of pyrochlore(P)and fluorite structures.Yb-Y co-doped samples exhibited much better sintering resistance compared with Gd-Y and Gd-Yb-Y co-doped samples.The coexistence of P and F phases is beneficial to improved sintering capability.The thermal conductivities of the Gd-Y,Yb-Y and Gd-Yb-Y doped samples are relatively lower(1.4-1.7 W m^(-1)K^(-1)at 1200℃),but for the La-Yb-Y co-doped samples,the thermal conductivity increases dramatically with temperature due to increased thermal radiation at high-temperature.The average thermal expansion coefficients(TECs)of the Gd-Y,Yb-Y and Gd-Yb-Y co-doped samples are as high as10.3×10^(-6)K^(-1) in temperature range between 200-1200℃.展开更多
Effects of rare earth oxides（Y2O3,La2O3,and Er2O3） on the viscosity,thermal expansion,and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer,dilatometry and F...Effects of rare earth oxides（Y2O3,La2O3,and Er2O3） on the viscosity,thermal expansion,and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer,dilatometry and FT-IR absorption spectra.The results showed that the melting temperature of alkali-free boroaluminosilicate glasses decreased from 1 697.55 to 1 662.59,1 674.37 and 1 640.87 ℃ with the introduction of 1 mol%La2O3,Y2O3 and Er2O3,respectively.However,the glass transition temperature Tg,dilatometric softening temperature T_d and coefficient of thermal expansion of alkali-free boro-aluminosilicate glasses increased when adding the rare-earth oxides.At high temperatures,incorporating rare earth oxides into glass resulted in the peak at about 1 085 cm^-1 towards lower wavenumber and the absorption band in the region of 850-1 260 cm^-1 broader,which indicated that rare earths acted as network modifiers and increased the numbers of non-bridging oxygen in the glass melts.However,the rare earths had an opposite effect and accumulated the glass structure at low temperatures near Tg.展开更多
A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. The effects of rare earth oxide (La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Dy2O3) and Nd2O3 doping content on th...A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. The effects of rare earth oxide (La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Dy2O3) and Nd2O3 doping content on the microstructure and dielectric properties of Y2Ti2O7 ceramics were investigated. The experimental results showed that the rare earth ions were considered to dissolve in Y-sites of the pyrochlore structure, different rare earth oxides and concentration had different influences on Y2Ti2O7 cerami...展开更多
Lithium triborate （LiB3O5） was synthesized by high temperature solid-state reaction method, and then rare earth oxides were doped into LiB3O5 to enhance its thermoluminescent （TL） properties. The identification an...Lithium triborate （LiB3O5） was synthesized by high temperature solid-state reaction method, and then rare earth oxides were doped into LiB3O5 to enhance its thermoluminescent （TL） properties. The identification and characteristics of the obtained compounds were determined by X-ray diffraction （XRD）, Fourier transform infrared （FTIR） analyses, differential thermal analyses （DTA） and scanning electron microscopy （SEM）. The glow curves were obtained using a thermoluminescent （TL） reader. The results revealed that all the rare earth oxides were not good activators for lithium triborate and the obtained compounds could not be used for dosimetric applications.展开更多
Surface compositions,structures,and acidities of the Mo-Te-Fe-Ni catalysts added with La_2O_3,CeO_2, Pr_6O_(12),Nd_2O_3 and Sm_2O_3 were measured and related with the activities of the catalysts for selective oxidatio...Surface compositions,structures,and acidities of the Mo-Te-Fe-Ni catalysts added with La_2O_3,CeO_2, Pr_6O_(12),Nd_2O_3 and Sm_2O_3 were measured and related with the activities of the catalysts for selective oxidation of olefins.It was found that adding rare earth elements to the Mo-Te catalysts increases obviously their selectivities to methacrolein(MAL),and the yield percentage of MAL changes periodically with the increase of atomic numbers of rare earth elements added,and the highest yield was obtained with the catalyst containing CeO_2.The addition of CeO_2 to 9-component Mo-Te catalyst increases not only the activity of the catalyst, but also its thermostability remarkably.The mechanism of rare earth elements in the catalysts was discussed.展开更多
Fine powders of γ-Fe_2O_3,doped with Y_2O_3,CeO_2,Eu_2O_3 or Tb_2O_3 have been prepared by the chemical co-precipitation method.The sensitivity of gas sensation has been measured with respect to the relative resist- ...Fine powders of γ-Fe_2O_3,doped with Y_2O_3,CeO_2,Eu_2O_3 or Tb_2O_3 have been prepared by the chemical co-precipitation method.The sensitivity of gas sensation has been measured with respect to the relative resist- ance change in the ceramic matrix upon introduction of inflammable gases.The structure of the materials has been studied with X-ray diffraction spectroscopy(XRD),electron diffraction spectroscopy( ED) and transmis- sion electron microscopy(TEM).The addition of rare earth oxides,which improves ceramic microstructure of γ-Fe_2O_3,improves gas sensitivity of γ-Fe_2O_3.The stability can be increased because of the increase of phase transition temperature.In addition,the selectivity of gas sensation of γ-Fe_2O_3 can be improved because of the variation of rare earth oxides.展开更多
Volatile organic compounds(VOCs),methane,carbon monoxide,soot,automotive exhaust,and nitrogen oxides are harmful to the atmosphere and human health.It is urgent to strictly control their emissions.Heterogeneous cataly...Volatile organic compounds(VOCs),methane,carbon monoxide,soot,automotive exhaust,and nitrogen oxides are harmful to the atmosphere and human health.It is urgent to strictly control their emissions.Heterogeneous catalysis is an effective pathway for the removal of these pollutants,and the critical issue is the development of novel and high-performance catalysts.In this review,we briefly summarize the preparation methods,physicochemical properties,catalytic activities,and related reaction mechanisms for the above pollutants removal of the rare earth oxides,mixed rare earth oxide,rare earth oxidesupported noble metal,and mixed rare earth oxide-supported noble metal catalysts that have been investigated by our group and other researchers.It was found that catalytic performance was associated with the factors,such as specific surface area,pore structure,particle size and dispersion,adsorbed oxygen species concentration,reducibility,reactant activation ability or interaction between metal nanoparticles and support.Furthermore,we also envision the development trend of such a topic in future work.展开更多
Ultrafine oxide dispersion strengthening(ODS)-Mo and ODS-W alloy powders containing different types of oxide nanoparticles were successfully synthesized by spraying method(solid−liquid mixing method)combined with the ...Ultrafine oxide dispersion strengthening(ODS)-Mo and ODS-W alloy powders containing different types of oxide nanoparticles were successfully synthesized by spraying method(solid−liquid mixing method)combined with the reductions with carbon black and hydrogen in sequence.It is concluded that the solution concentration and type of rare earth oxide have no effect on the grain size of ODS-Mo alloy powder,but have obvious effect on that of ODS-W alloy powder.The higher the concentration of rare earth solution is,the smaller the average grain size of ODS-W alloy powder is.Furthermore,compared with doping with CeO_(2),the grain sizes of reduction products of La_(2)O_(3) and Y_(2)O_(3) doped WO_(3) are relatively larger.Compared with the undoped case,there is almost no change for grain size of ODS-Mo alloy powder,while the grain size of ODS-W alloy powder becomes much larger.This is probably due to the appearance of the composite oxide(such as La_(2)WO_(6))formed by the reaction between tungsten oxide and rare earth oxides,which promotes the heterogeneous nucleation and growth of tungsten grains during the reduction process of ODS-W,while there is no complex oxide composed of molybdenum and rare earth oxides in the reduction process of ODS-Mo.展开更多
Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing p...Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten ma-terials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing tempera-ture range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.展开更多
Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-te...Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-temperature phase stability limits its further application.In this work,four sets of TBCs high-entropy ceramics,(Sm_(1/5)Dy_(1/5)Ho_(1/5)Er_(1/5)Yb_(1/5))(Nb_(1/2)Ta_(1/2))O_(4)(5NbTa),(Sm_(1/6)Dy_(1/6)Ho_(1/6)Er_(1/6)Yb_(1/6)Lu_(1/6))(Nb_(1/2)Ta_(1/2))O_(4)(6NbTa),(Sm_(1/7)Gd_(1/7)Dy_(1/7)Ho_(1/7)Er_(1/7)Yb_(1/7)Lu_(1/7))(Nb_(1/2)Ta_(1/2))O_(4)(7NbTa),(Sm_(1/8)Gd_(1/8)Dy_(1/8)Ho_(1/8)Er_(1/8)Tm_(1/8)Yb_(1/8)Lu_(1/8))(Nb_(1/2)Ta_(1/2))O_(4)(8NbTa)are synthesized using a solid-state reaction method at 1650℃for 6 h.Firstly,the X-ray diffractometer(XRD)patterns display that the samples are all single-phase solid solution structures(space group C 2/c).Differential scanning calorimetry(DSC)and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400℃,which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O.Secondly,compared to high-entropy rare-earth niobates,the introduction of Ta atoms at B site substantially reduce thermal conductivity(re-duced by 44%,800℃)with the seven components high entropy ceramic as an example.The low thermal conductivity means strong phonon scattering,which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates(5–8NbTa)revealed by the first-principles calculations.Thirdly,the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions.The oxygen-ion conductivity of 8NbTa(3.31×10^(−6)S cm^(−1),900℃)is about 5 times lower than that of 8HERN(15.8×10^(−6)S cm^(−1),900℃)because of the sluggish diffusion effect,providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide(TGO)of TBCs.In addition,influenced by lattice dis-tortion and solid solution strengthening,the samples possess higher hardness(7.51–8.15 GPa)and TECs(9.78×10^(−6)K−1^(-1)0.78×10^(−6)K^(−1),1500℃)than the single rare-earth niobates and tantalates.Based on their excellent overall properties,it is considered that 5–8NbTa can be used as auspicious TBCs.展开更多
development of refractories with low reactivity to rare earth inclusions is an important direction to solve the problem of the nozzle clogging of rare earth steel.La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and LaAlO_(3)powde...development of refractories with low reactivity to rare earth inclusions is an important direction to solve the problem of the nozzle clogging of rare earth steel.La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and LaAlO_(3)powders were synthesized using the high-temperature solid-state method with La_(2)O_(3),CeO_(2),ZrO_(2),and Al2O_(3)(particle sizes of 5-10μm)as raw materials,firing at 1400℃for 2 h.Subsequently,La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and Y_(2)O_(3)powders were pressed intoφ30 mm×7 mm substrate samples with PVA as a binder;and equal amounts of La_(2)O_(3),La_(2)S_(3),and LaAlO_(3)powders were placed on their surfaces.The samples were then fired at 1550℃for 3 h with carbon embedded.The interfacial reaction of the three rare earth oxide refractories(La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and Y_(2)O_(3))with the main rare earth inclusions(La_(2)O_(3),La_(2)S_(3),and LaAlO_(3))in molten rare earth steel was studied.The results show that the La_(2)Ce_(2)O_(7)sample has poor structural stability and readily reacts with La_(2)S_(3),leading to cracking.The La_(2)Zr_(2)O_(7)sample reacts with La_(2)O_(3)and LaAlO_(3)weakly,but performs poor La_(2)S_(3)corrosion resistance.The Y_(2)O_(3)sample demonstrates the weakest interaction with the three rare earth inclusions as well as the most stable structure,indicating significant potential as a specialized anti-clogging lining material for rare earth steel.展开更多
Accurately quantifying rates of soil erosion requires capturing both the volumetric nature of the visible,convergent fluvial pathways(also known as rills)and the subtle nature of the less-visible,diffuse pathways(inte...Accurately quantifying rates of soil erosion requires capturing both the volumetric nature of the visible,convergent fluvial pathways(also known as rills)and the subtle nature of the less-visible,diffuse pathways(interrill areas).The aim of this study was to use Rare Earth Oxide(REO)tracers and Structure-from-Motion(SfM)photogrammetry to elucidate retrospective information about soil erosion rates and sediment sources during different soil erosion conditions,within a controlled laboratory environment.The experimental conditions created erosion events consistent with diffuse and convergent erosion processes.REO tracers allowed the sediment transport distances of over 2 m to be described,and helped resolved the relative contribution of diffuse and convergent soil erosion;interrill areas were also iden-tified as a significant sediment sources soil loss under convergent erosion conditions.While the potential for SfM photogrammetry to resolve sub-millimetre elevations changes was demonstrated,under some conditions non-erosional changes in surface elevation,such as compaction,exceeded volumes of soil loss via diffuse erosion.The discrepancies between SfM Photogrammetry calculations and REO tagged sediment export were beneficial,identifying that during soil erosion events sediment in both aggregate and particle form is deposited within the convergent features,even when the rill extended the full length of the soil surface.The combination of SfM photogrammetry and REO tracers has provided a novel platform for building a spatial understanding of patterns of soil loss and source apportionment between rill and interrill erosion.展开更多
Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A...Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.展开更多
Broadband transparent films play a pivotal role in various applications such as lenses and solar cells,particularly porous structured transparent films exhibit significant potential.This study investigates a porous Si...Broadband transparent films play a pivotal role in various applications such as lenses and solar cells,particularly porous structured transparent films exhibit significant potential.This study investigates a porous SiO_(2) refractive index gradient anti-reflective film prepared by atomic layer deposition(ALD).A porous SiO_(2) film with gradual porosity was obtained by phosphoric acid etching of Al_(2)O_(3)/SiO_(2) multilayers with gradient Al2O3 ratios,achieving a gradual decrease in refractive index from the substrate to the surface.The film exhibited an average transmittance as high as 97.8%within the wavelength range from 320 nm to 1200 nm.The environmental adaptability was further enhanced by surface modification using rare earth oxide(REO)La_(2)O_(3),resulting in formation of a lotus leaf-like structure and achieving a water contact angle of 100.0°.These data proved that the modification significantly improved hydrophobic self-cleaning capability while maintaining exceptional transparency of the film.The surface structure of the modified film remained undamaged even after undergoing wipe testing,demonstrating its excellent surface durability.展开更多
In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3O...In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3OH conversion and H_(2)yield,the reaction perfo rmance of the catalysts ranks as Cu/Sm_(2)O_(3)-M>Cu/Sm_(2)O_(3)-C>Cu/Gd_(2)O_(3)-M>Cu/Gd_(2)O_(3)-C>Cu/Eu_(2)O_(3)-M>Cu/Eu_(2)O_(3)-C.For the same kind of REO,Cu supported on the monoclinic support shows better performance than on the cubic one.Despite the phase structure difference,Sm_(2)O_(3) is the best support among all the three kinds of REOs.Compared with Cu/REO catalysts prepared with cubic supports,the corresponding catalysts prepared with monoclinic supports generally possess mo re surface oxygen vacancies,which can generate mo re surface active oxygen(O_(2)^(-)) and moderate basic sites.Moreover,the contents of Cu^(+) on the catalysts follow the same sequence.The reaction performance is positively related to the amount of these three types of surface sites.But metallic Cuo species is necessary to maintain the Cu^(+)■Cu^(0) redox cycle.Furthe rmore,on a catalyst with good perfo rmance,those vital surface reaction intermediates can be stabilized during the reaction.Cu/Sm_(2)O_(3)-M possesses the largest quantities of these surface sites,and has the appropriate amount of Cu^(+) and Cu^(0) after reduction,thereby displaying the optimal performance in all the catalysts.In conclusion,evident support crystal structure effect is observed for Cu/REO catalysts,and a monoclinic phase REO is a better support than the respective cubic phase one.展开更多
This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage(AMD)streams to recover rare earth elements(REEs).A life cycle assessment(...This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage(AMD)streams to recover rare earth elements(REEs).A life cycle assessment(LCA)study was done to evaluate the environmental impacts of rare earth production from deleterious material in the form of highly contaminated leachate(HCL)and low-contaminated leachate(LCL).The results indicate that the main contributors to environmental categories that produce RE-hydroxide stages are NaOH and electricity.Also,oxalic acid,Na_(2)CO_(3),and hydrochloric acid significantly contribute to the production stage of individual rare earth oxides(REOs),including solvent extraction(SX)and precipitation steps.The HCL route has higher environmental impacts than LCL due to higher chemical/energy and H_(2)SO_(4)usage,so 468 and 292 kg of carbon dioxide are generated to produce1 t of individual REOs from HCL and LCL routes,respectively.Moreover,the carbon dioxide emitted from the process,including the RE-hydroxide production,SX,and REOs production,is less than 10 t CO_(2).A sensitivity analysis was also performed to assess the changeability of the environmental footprints of the main inputs in the SX process,as the main stage has a higher contribution to the whole process.This LCA study is the first step toward understanding the environmental influence of new processing methods to produce REEs from coal by-products through a developed pilot-scale process.展开更多
基金financial support from the National Natural Science Foundation of China(No.52201104)the Natural Science Foundation of Hunan Province(No.2023JJ40032)the Education Department of Hunan Province of China(No.24B0321).
文摘This study delved into the corrosion behavior of ZK60 Mg alloy in saturated NaCl solution,particularly focusing on the effects of the addition of rare earth oxide,namely CeO_(2)(forming ZKC alloy)and La_(2)O_(3)(forming ZKL alloy).The results indicate that the introduction of CeO_(2)and La_(2)O_(3)promotes the precipita-tion of T-(Mg_(1−x),Zn_(x))_(11)RE phases(Mg-Zn-RE phases,where RE represents Ce or La)at grain boundaries.The presence and distribution pattern of the T-phase have a profound impact on the corrosion resis-tance of the Mg alloy.Specifically,the ZKC alloy exhibits the most outstanding corrosion resistance.This superior performance is attributed to the uniform distribution of(Mg_(1−x),Zn_(x))_(11)Ce phase at grain bound-aries in ZK60-0.5 wt%CeO_(2),effectively hindering the penetration of corrosive media into the matrix.Additionally,scanning kelvin probe force microscopy(SKPFM)analysis reveals that the(Mg_(1−x),Zn_(x))_(11)Ce phase exhibits the smallest potential difference with the matrix,significantly mitigating the tendency for galvanic corrosion.In contrast,the ZKL alloy displays less precipitation and uneven distribution of the(Mg_(1−x),Zn_(x))_(11)La phase,resulting in inferior corrosion resistance compared to the ZKC alloy.The dispar-ities in the precipitation of the two phases,as derived from first-principles calculations,stem from the spontaneous reduction of CeO_(2)under Mg conditions,whereas the reduction reaction between La_(2)O_(3)and Mg cannot proceed spontaneously.Furthermore,SKPFM analysis and CALPHAD method found that as the addition of CeO_(2)/La_(2)O_(3)increases,the atomic ratio of Zn in the Mg-Zn-RE ternary phase rises,accompa-nied by an increase in the potential difference between the Mg-Zn-RE phase and the Mg matrix.This suggests that fine-tuning the addition of rare earth oxides can modify the atomic ratio of the Mg-Zn-RE ternary phase,thereby enhancing the corrosion resistance of the Mg alloy.In summary,this study not only unravels the specific mechanisms of how CeO_(2)and La_(2)O_(3)affect the corrosion behavior of ZK60 Mg alloy but also provides new strategies and insights for the development of low-cost,high-performance corrosion-resistant Mg alloy materials.
基金Project supported by One Hundred Excellent Talents of Hebei Province of China and Key Project of Science and Technology of Hebei Province (09215106D)
文摘The flux cored wires with different amounts of rare earth （RE） oxides additions for hardfacing （harden-face-welding） the workpieces of high chromium cast iron were studied in this work.The morphology of carbides in hardfacing metal was observed,and the type of the carbides was determined by optical microscopy,scanning electron microscopy （SEM）,energy dispersive spectrometer （EDS） and X-ray diffraction （XRD）.Based on the data of effect of RE on carbides morphology,the refined reason for carbide by RE oxide was discussed with the misfit theory.The results showed that,the microstructure of hardfacing metal was composed of martensite,residual austenite and M7C3 carbides.With the increasing amount of RE oxide additions,the volume fraction and roundness of the carbides were increased,however,the area and perimeter of carbides were decreased.It indicated that carbides in hardfacing metal could be refined and spheroidized by adding RE oxides in flux cored wires.
基金the Natural Science Foundation of Jiangxi Province (No. 0650047)the Science and Technology Program of the Education Department of Jiangxi Province,China(No.GJJ08268).
文摘The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...
基金supported by National Basic Research Program of China (2010CB732300)the National High Technology Research and Development Program of China (2011AA03A406)the "ShuGuang" Project of Shanghai Municipal Education Commission and Shanghai Education Development Foundation (10GG23)
文摘Rare earth （La, Nd and Tb） oxides with one-dimensional micro/nanostmcatres were synthesized hydrothermally under facile and mild conditions with two surfactants, and characterized by X-ray diffraction （XRD）, thermal gravimetry （TG）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and photoluminescence. The results showed that the synthesized rare earth oxides behaved regular nano- and micro-scale structures. And the morphologies of samples depended on the radii of rare earth ions, with the help of two sur- factants of sodium dodecyl sulfonic and PEG 600. Nanocrystalline La2O3：Eu^3＋ possessed good photoluminescence （PL） property and might be used as a nanosized phosphor, its PL intensity was akered by the doping Eu^3＋ concentration and the optimum concentration of Eu^3＋ was 3 mol.%. In comparison with bulk Eu^3＋/La2O3, Eu^3＋/nano-La2O3 showed better photoluminescence property, nearly equal to that of nanocrtstalline La2O3：Eu^3＋. Tb4O7 microwires showed interesting photoluminescence properties.
基金supported financially by the National Natural Science Foundation of China(Nos.U1537212,51971013,51590894and 51425102)the National Key Research and Development Program of China(No.2016YFB0300901)。
文摘Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sintering resistance,and thermo-physical properties of the doped hafnia ceramics were investigated.Results show that the Gd-Y,Yb-Y or Gd-Yb-Y co-doped hafnia ceramics remain the same defect fluorite(F)structure,while the La-Yb-Y co-doped hafnia revealing coexistence of pyrochlore(P)and fluorite structures.Yb-Y co-doped samples exhibited much better sintering resistance compared with Gd-Y and Gd-Yb-Y co-doped samples.The coexistence of P and F phases is beneficial to improved sintering capability.The thermal conductivities of the Gd-Y,Yb-Y and Gd-Yb-Y doped samples are relatively lower(1.4-1.7 W m^(-1)K^(-1)at 1200℃),but for the La-Yb-Y co-doped samples,the thermal conductivity increases dramatically with temperature due to increased thermal radiation at high-temperature.The average thermal expansion coefficients(TECs)of the Gd-Y,Yb-Y and Gd-Yb-Y co-doped samples are as high as10.3×10^(-6)K^(-1) in temperature range between 200-1200℃.
基金Funded by the National Key Research and Development Program of China(No.2016YFB0303702)
文摘Effects of rare earth oxides（Y2O3,La2O3,and Er2O3） on the viscosity,thermal expansion,and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer,dilatometry and FT-IR absorption spectra.The results showed that the melting temperature of alkali-free boroaluminosilicate glasses decreased from 1 697.55 to 1 662.59,1 674.37 and 1 640.87 ℃ with the introduction of 1 mol%La2O3,Y2O3 and Er2O3,respectively.However,the glass transition temperature Tg,dilatometric softening temperature T_d and coefficient of thermal expansion of alkali-free boro-aluminosilicate glasses increased when adding the rare-earth oxides.At high temperatures,incorporating rare earth oxides into glass resulted in the peak at about 1 085 cm^-1 towards lower wavenumber and the absorption band in the region of 850-1 260 cm^-1 broader,which indicated that rare earths acted as network modifiers and increased the numbers of non-bridging oxygen in the glass melts.However,the rare earths had an opposite effect and accumulated the glass structure at low temperatures near Tg.
基金Project supported by the Key University Science Research Project of Jiangsu Province (08KJA430002)
文摘A series of Y2Ti2O7 microwave dielectric ceramics were synthesized by conventional solid-state method. The effects of rare earth oxide (La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3 and Dy2O3) and Nd2O3 doping content on the microstructure and dielectric properties of Y2Ti2O7 ceramics were investigated. The experimental results showed that the rare earth ions were considered to dissolve in Y-sites of the pyrochlore structure, different rare earth oxides and concentration had different influences on Y2Ti2O7 cerami...
基金Project supported by Scientific HR Development Program Program (BAP-08-11-DPT2002120510)National Boron Research Institution (2006-05-G11-05)
文摘Lithium triborate （LiB3O5） was synthesized by high temperature solid-state reaction method, and then rare earth oxides were doped into LiB3O5 to enhance its thermoluminescent （TL） properties. The identification and characteristics of the obtained compounds were determined by X-ray diffraction （XRD）, Fourier transform infrared （FTIR） analyses, differential thermal analyses （DTA） and scanning electron microscopy （SEM）. The glow curves were obtained using a thermoluminescent （TL） reader. The results revealed that all the rare earth oxides were not good activators for lithium triborate and the obtained compounds could not be used for dosimetric applications.
文摘Surface compositions,structures,and acidities of the Mo-Te-Fe-Ni catalysts added with La_2O_3,CeO_2, Pr_6O_(12),Nd_2O_3 and Sm_2O_3 were measured and related with the activities of the catalysts for selective oxidation of olefins.It was found that adding rare earth elements to the Mo-Te catalysts increases obviously their selectivities to methacrolein(MAL),and the yield percentage of MAL changes periodically with the increase of atomic numbers of rare earth elements added,and the highest yield was obtained with the catalyst containing CeO_2.The addition of CeO_2 to 9-component Mo-Te catalyst increases not only the activity of the catalyst, but also its thermostability remarkably.The mechanism of rare earth elements in the catalysts was discussed.
基金The project supported by the National Natural Science Foundation of China
文摘Fine powders of γ-Fe_2O_3,doped with Y_2O_3,CeO_2,Eu_2O_3 or Tb_2O_3 have been prepared by the chemical co-precipitation method.The sensitivity of gas sensation has been measured with respect to the relative resist- ance change in the ceramic matrix upon introduction of inflammable gases.The structure of the materials has been studied with X-ray diffraction spectroscopy(XRD),electron diffraction spectroscopy( ED) and transmis- sion electron microscopy(TEM).The addition of rare earth oxides,which improves ceramic microstructure of γ-Fe_2O_3,improves gas sensitivity of γ-Fe_2O_3.The stability can be increased because of the increase of phase transition temperature.In addition,the selectivity of gas sensation of γ-Fe_2O_3 can be improved because of the variation of rare earth oxides.
基金Project supported by National Natural Science Foundation of China(21677004,21876006,21622701)National Natural Science Committee of China-Liaoning Provincial People’s Government Joint Fund(U1908204)Foundation on the Creative Research Team Construction Promotion Project of Beijing Municipal Institutions(IDHT20190503)。
文摘Volatile organic compounds(VOCs),methane,carbon monoxide,soot,automotive exhaust,and nitrogen oxides are harmful to the atmosphere and human health.It is urgent to strictly control their emissions.Heterogeneous catalysis is an effective pathway for the removal of these pollutants,and the critical issue is the development of novel and high-performance catalysts.In this review,we briefly summarize the preparation methods,physicochemical properties,catalytic activities,and related reaction mechanisms for the above pollutants removal of the rare earth oxides,mixed rare earth oxide,rare earth oxidesupported noble metal,and mixed rare earth oxide-supported noble metal catalysts that have been investigated by our group and other researchers.It was found that catalytic performance was associated with the factors,such as specific surface area,pore structure,particle size and dispersion,adsorbed oxygen species concentration,reducibility,reactant activation ability or interaction between metal nanoparticles and support.Furthermore,we also envision the development trend of such a topic in future work.
基金financial support from the National Natural Science Foundation of China (No.51734002)。
文摘Ultrafine oxide dispersion strengthening(ODS)-Mo and ODS-W alloy powders containing different types of oxide nanoparticles were successfully synthesized by spraying method(solid−liquid mixing method)combined with the reductions with carbon black and hydrogen in sequence.It is concluded that the solution concentration and type of rare earth oxide have no effect on the grain size of ODS-Mo alloy powder,but have obvious effect on that of ODS-W alloy powder.The higher the concentration of rare earth solution is,the smaller the average grain size of ODS-W alloy powder is.Furthermore,compared with doping with CeO_(2),the grain sizes of reduction products of La_(2)O_(3) and Y_(2)O_(3) doped WO_(3) are relatively larger.Compared with the undoped case,there is almost no change for grain size of ODS-Mo alloy powder,while the grain size of ODS-W alloy powder becomes much larger.This is probably due to the appearance of the composite oxide(such as La_(2)WO_(6))formed by the reaction between tungsten oxide and rare earth oxides,which promotes the heterogeneous nucleation and growth of tungsten grains during the reduction process of ODS-W,while there is no complex oxide composed of molybdenum and rare earth oxides in the reduction process of ODS-Mo.
基金supported by the National Basic Research Program of China(973 Program)(2014CB660802)the National Natural Science Foundation of China(51474166)Natural Science Foundation of Hubei Province(2012FFA102)
文摘Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides (La2O3, Nd2O3 and Y2O3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten ma-terials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing tempera-ture range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.
基金support from Yunnan Major Scientific and Technological Projects(No.202302AG050010)Yunnan Fundamental Research Projects(Nos.202101AW070011 and202101BE070001–015)+1 种基金National Natural Science Foundation of China(No.52303295)Project Funds of“Xingdian Talent Support Program”.
文摘Improving and optimizing the target properties of ceramics via the high entropy strategy has attracted significant attention.Rare earth niobate is a potential thermal barrier coating(TBCs)material,but its poor high-temperature phase stability limits its further application.In this work,four sets of TBCs high-entropy ceramics,(Sm_(1/5)Dy_(1/5)Ho_(1/5)Er_(1/5)Yb_(1/5))(Nb_(1/2)Ta_(1/2))O_(4)(5NbTa),(Sm_(1/6)Dy_(1/6)Ho_(1/6)Er_(1/6)Yb_(1/6)Lu_(1/6))(Nb_(1/2)Ta_(1/2))O_(4)(6NbTa),(Sm_(1/7)Gd_(1/7)Dy_(1/7)Ho_(1/7)Er_(1/7)Yb_(1/7)Lu_(1/7))(Nb_(1/2)Ta_(1/2))O_(4)(7NbTa),(Sm_(1/8)Gd_(1/8)Dy_(1/8)Ho_(1/8)Er_(1/8)Tm_(1/8)Yb_(1/8)Lu_(1/8))(Nb_(1/2)Ta_(1/2))O_(4)(8NbTa)are synthesized using a solid-state reaction method at 1650℃for 6 h.Firstly,the X-ray diffractometer(XRD)patterns display that the samples are all single-phase solid solution structures(space group C 2/c).Differential scanning calorimetry(DSC)and the high-temperature XRD of 8NbTa cross-check that the addition of Ta element in 8HERN increases the phase transition temperature above 1400℃,which can be attributed to that the Ta/Nb co-doping at B site introduces the fluctuation of the bond strength of Ta-O and Nb-O.Secondly,compared to high-entropy rare-earth niobates,the introduction of Ta atoms at B site substantially reduce thermal conductivity(re-duced by 44%,800℃)with the seven components high entropy ceramic as an example.The low thermal conductivity means strong phonon scattering,which may originate from the softening acoustic mode and flattened phonon dispersion in 5–8 principal element high entropy rare earth niobium tantalates(5–8NbTa)revealed by the first-principles calculations.Thirdly,the Ta/Nb co-doping in 5–8NbTa systems can further optimize the insulation performance of oxygen ions.The oxygen-ion conductivity of 8NbTa(3.31×10^(−6)S cm^(−1),900℃)is about 5 times lower than that of 8HERN(15.8×10^(−6)S cm^(−1),900℃)because of the sluggish diffusion effect,providing better oxygen barrier capacity in 5–8NbTa systems to inhibit the overgrowth of the thermal growth oxide(TGO)of TBCs.In addition,influenced by lattice dis-tortion and solid solution strengthening,the samples possess higher hardness(7.51–8.15 GPa)and TECs(9.78×10^(−6)K−1^(-1)0.78×10^(−6)K^(−1),1500℃)than the single rare-earth niobates and tantalates.Based on their excellent overall properties,it is considered that 5–8NbTa can be used as auspicious TBCs.
文摘development of refractories with low reactivity to rare earth inclusions is an important direction to solve the problem of the nozzle clogging of rare earth steel.La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and LaAlO_(3)powders were synthesized using the high-temperature solid-state method with La_(2)O_(3),CeO_(2),ZrO_(2),and Al2O_(3)(particle sizes of 5-10μm)as raw materials,firing at 1400℃for 2 h.Subsequently,La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and Y_(2)O_(3)powders were pressed intoφ30 mm×7 mm substrate samples with PVA as a binder;and equal amounts of La_(2)O_(3),La_(2)S_(3),and LaAlO_(3)powders were placed on their surfaces.The samples were then fired at 1550℃for 3 h with carbon embedded.The interfacial reaction of the three rare earth oxide refractories(La_(2)Ce_(2)O_(7),La_(2)Zr_(2)O_(7),and Y_(2)O_(3))with the main rare earth inclusions(La_(2)O_(3),La_(2)S_(3),and LaAlO_(3))in molten rare earth steel was studied.The results show that the La_(2)Ce_(2)O_(7)sample has poor structural stability and readily reacts with La_(2)S_(3),leading to cracking.The La_(2)Zr_(2)O_(7)sample reacts with La_(2)O_(3)and LaAlO_(3)weakly,but performs poor La_(2)S_(3)corrosion resistance.The Y_(2)O_(3)sample demonstrates the weakest interaction with the three rare earth inclusions as well as the most stable structure,indicating significant potential as a specialized anti-clogging lining material for rare earth steel.
文摘Accurately quantifying rates of soil erosion requires capturing both the volumetric nature of the visible,convergent fluvial pathways(also known as rills)and the subtle nature of the less-visible,diffuse pathways(interrill areas).The aim of this study was to use Rare Earth Oxide(REO)tracers and Structure-from-Motion(SfM)photogrammetry to elucidate retrospective information about soil erosion rates and sediment sources during different soil erosion conditions,within a controlled laboratory environment.The experimental conditions created erosion events consistent with diffuse and convergent erosion processes.REO tracers allowed the sediment transport distances of over 2 m to be described,and helped resolved the relative contribution of diffuse and convergent soil erosion;interrill areas were also iden-tified as a significant sediment sources soil loss under convergent erosion conditions.While the potential for SfM photogrammetry to resolve sub-millimetre elevations changes was demonstrated,under some conditions non-erosional changes in surface elevation,such as compaction,exceeded volumes of soil loss via diffuse erosion.The discrepancies between SfM Photogrammetry calculations and REO tagged sediment export were beneficial,identifying that during soil erosion events sediment in both aggregate and particle form is deposited within the convergent features,even when the rill extended the full length of the soil surface.The combination of SfM photogrammetry and REO tracers has provided a novel platform for building a spatial understanding of patterns of soil loss and source apportionment between rill and interrill erosion.
基金Foundation ite ms:Project supported bythe Grant-in-Aidfor Scientific Research (C) (18560662) bythe Japan Societyfor the Promotion of Science
文摘Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.
文摘Broadband transparent films play a pivotal role in various applications such as lenses and solar cells,particularly porous structured transparent films exhibit significant potential.This study investigates a porous SiO_(2) refractive index gradient anti-reflective film prepared by atomic layer deposition(ALD).A porous SiO_(2) film with gradual porosity was obtained by phosphoric acid etching of Al_(2)O_(3)/SiO_(2) multilayers with gradient Al2O3 ratios,achieving a gradual decrease in refractive index from the substrate to the surface.The film exhibited an average transmittance as high as 97.8%within the wavelength range from 320 nm to 1200 nm.The environmental adaptability was further enhanced by surface modification using rare earth oxide(REO)La_(2)O_(3),resulting in formation of a lotus leaf-like structure and achieving a water contact angle of 100.0°.These data proved that the modification significantly improved hydrophobic self-cleaning capability while maintaining exceptional transparency of the film.The surface structure of the modified film remained undamaged even after undergoing wipe testing,demonstrating its excellent surface durability.
基金Project supported by the National Natural Science Foundation of China(22172071,22102069,22062013,22262021,21962009)Natural Science Foundation of Jiangxi Province,China(20202BAB203006,20212BAB203030)Key Laboratory Foundation of Jiangxi Province for Environment and Energy Catalysis,China(20181BCD40004).
文摘In this work,to study the phase structure effect,three groups of Cu/REO catalysts were prepared with cubic and monoclinic Gd_(2)O_(3),Eu_(2)O_(3)and Sm_(2)O_(3) supports for MSR reaction to produce H_(2).Based on CH3OH conversion and H_(2)yield,the reaction perfo rmance of the catalysts ranks as Cu/Sm_(2)O_(3)-M>Cu/Sm_(2)O_(3)-C>Cu/Gd_(2)O_(3)-M>Cu/Gd_(2)O_(3)-C>Cu/Eu_(2)O_(3)-M>Cu/Eu_(2)O_(3)-C.For the same kind of REO,Cu supported on the monoclinic support shows better performance than on the cubic one.Despite the phase structure difference,Sm_(2)O_(3) is the best support among all the three kinds of REOs.Compared with Cu/REO catalysts prepared with cubic supports,the corresponding catalysts prepared with monoclinic supports generally possess mo re surface oxygen vacancies,which can generate mo re surface active oxygen(O_(2)^(-)) and moderate basic sites.Moreover,the contents of Cu^(+) on the catalysts follow the same sequence.The reaction performance is positively related to the amount of these three types of surface sites.But metallic Cuo species is necessary to maintain the Cu^(+)■Cu^(0) redox cycle.Furthe rmore,on a catalyst with good perfo rmance,those vital surface reaction intermediates can be stabilized during the reaction.Cu/Sm_(2)O_(3)-M possesses the largest quantities of these surface sites,and has the appropriate amount of Cu^(+) and Cu^(0) after reduction,thereby displaying the optimal performance in all the catalysts.In conclusion,evident support crystal structure effect is observed for Cu/REO catalysts,and a monoclinic phase REO is a better support than the respective cubic phase one.
文摘This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage(AMD)streams to recover rare earth elements(REEs).A life cycle assessment(LCA)study was done to evaluate the environmental impacts of rare earth production from deleterious material in the form of highly contaminated leachate(HCL)and low-contaminated leachate(LCL).The results indicate that the main contributors to environmental categories that produce RE-hydroxide stages are NaOH and electricity.Also,oxalic acid,Na_(2)CO_(3),and hydrochloric acid significantly contribute to the production stage of individual rare earth oxides(REOs),including solvent extraction(SX)and precipitation steps.The HCL route has higher environmental impacts than LCL due to higher chemical/energy and H_(2)SO_(4)usage,so 468 and 292 kg of carbon dioxide are generated to produce1 t of individual REOs from HCL and LCL routes,respectively.Moreover,the carbon dioxide emitted from the process,including the RE-hydroxide production,SX,and REOs production,is less than 10 t CO_(2).A sensitivity analysis was also performed to assess the changeability of the environmental footprints of the main inputs in the SX process,as the main stage has a higher contribution to the whole process.This LCA study is the first step toward understanding the environmental influence of new processing methods to produce REEs from coal by-products through a developed pilot-scale process.
