China is the global leader in rare earth （RE） production using hydrometallurgical processes. Advantageous extraction techniques of rare earths from Baotou mixed rare earth minerals, bastnaesite, and ion-adsorption c...China is the global leader in rare earth （RE） production using hydrometallurgical processes. Advantageous extraction techniques of rare earths from Baotou mixed rare earth minerals, bastnaesite, and ion-adsorption clays of rare earth deposits have been developed in China. The separation and purification technologies have also achieved rapid development. The industrial application processes for rare earth hydrometallurgy were summarized in the present paper. With the large demands and rapid development of rare earths, the issues of resources and environment are more prominent. This review gives an overview of the main processes that were developed in the past toward greener hydrometallurgy of rare earths in China. Based on the development of the rare earth industry, comprehensive utilization and cleaner production should still be focused on in the future, to support the sustainable development.展开更多
Higher strength is always the goal pursued by researchers for the structural materials,especially for the lightweight magnesium(Mg)alloys which generally have relatively low strength at present.From this aspect,the pr...Higher strength is always the goal pursued by researchers for the structural materials,especially for the lightweight magnesium(Mg)alloys which generally have relatively low strength at present.From this aspect,the present paper reviews the recent reports of a kind of Mg alloys,i.e.Mg-RE(RE:rare earths,mainly Gd or Y)casting and wrought alloys,which have been able to achieve high strength compared with common or commercial Mg alloys,from the viewpoint and content of the alloy system,alloying constitution,preparation process,tensile strength and each of the main strengthening mechanisms.This review of recent research and developments in high-strength Mg-RE alloys is beneficial for the further design of Mg alloys with higher strength as well as excellent comprehensive performance.展开更多
It is known to all that China is abundant in rare earth resources. But rare earth deposits are really not that rare in the earth crest. In the five continents, i.e. Asia, Europe, Australia, North and South America, an...It is known to all that China is abundant in rare earth resources. But rare earth deposits are really not that rare in the earth crest. In the five continents, i.e. Asia, Europe, Australia, North and South America, and Africa, there are about thirty four countries found to have rare earth deposits; Brazil might surpass China and rank the first in rare earth deposits. At present, investment in rare earth production was surged, there have been about 200 projects, and the total production for 25 of them would be more than 170 thousand tons after 2015, a multi-supply system on rare earths is being established worldwide. Cautions on the investment of rare earth production are involved.展开更多
Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of l...Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of laser claddings are relatively restricted when compared with well-established coating techniques because of their inherent defects identified as cracks, pores and inclusions. Substantial evidence suggests that the incorporation of an appropriate amount of rare earth in laser claddings can remarkably prevent these defects. Additionally, the presence of rare earth in laser claddings can notably enhance tribo-mechanical properties such as surface hardness, modulus of elasticity, fracture toughness, friction coefficient and wear rate. In this literature review, the effect of rare earth in reducing dilution and cracks susceptibility of laser claddings in addition to microstructural refinement attained was examined. Mechanical and tribological properties of these claddings along with their underlying mechanism were discussed in detail. Finally, this article summarizes current applications of laser claddings based on rare earth and was concluded with future research directions.展开更多
The existing state and partitioning of rare earth （RE） on weathered ores in Longnan County（LN）, Xingfeng County（XF） and Ninghua County（NH） were characterized systematically by standard geological analytical me...The existing state and partitioning of rare earth （RE） on weathered ores in Longnan County（LN）, Xingfeng County（XF） and Ninghua County（NH） were characterized systematically by standard geological analytical methods. It is found that RE in the weathered rare earth ores exist as four phases： （a） water soluble, （b） ion-exchangeable, （c） colloidal sediment （oxides）, （d） minerals, in which mainly as ion exchangeable phase, accounting for nearly 80% of total RE, with about 20% in the form of colloid sediment phase and mineral phase, but very little as aqueous soluble phase. These rare earth partitioning were mainly chosen mid-heavy RE elements, occupying above 60%, but not equal in the four phases. The mid-heavy RE elements were primarily enriched in the ion exchangeable phase up to 40%, while the containment of cerium dioxide is below 2 %. The cerium deficiency occurs in the ion exchangeable phase in weathered ore. It results from that the Ce^3＋ is oxidized into Ce^4＋ and changes into CeO2. For LN ore, the containment of Y is high in weathered ore because Y-minerals are abundant in original rock.展开更多
Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little...Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little or no rare earth(or heavy rare earth).Nd-Fe-B magnets have been painstakingly and skillfully optimized for a wide range of applications in which high performance is required at reasonable cost.Sm-Co is the material of choice when high-temperature stability is required,and Sm-Fe-N magnets are making their way into some niche applications.The scope for improvement in these basic materials by substitution has been rather thoroughly explored,and the effects of processing techniques on the microstructure and hysteresis are largely understood.A big idea from a generation ago-which held real potential to raise the record energy product significantly-was the oriented exchange-spring hard/soft nanocomposite magnet;however,it has proved very difficult to realize.Nevertheless,the field has evolved,and innovation has flourished in other areas.For example,electrical personal transport has progressed from millions of electric bicycles to the point where cars and trucks with electrical drives are becoming mainstream,and looks ready to bring the dominance of the internal combustion engine to an end.As the limitations of particular permanent magnets become clearer,ingenuity and imagination are being used to design around them,and to exploit the available mix of rare earth resources most efficiently.Huge new markets in robotics beckon,and the opportunities offered by additive manufacturing are just beginning to be explored.New methods of increasing magnet stability at elevated temperature are being developed,and integrated multifunctionality of hard magnets with other useful properties is now envisaged.These themes are elaborated here,with various examples.展开更多
In this paper, the recent advance of processes for treating Baotou mixed-type rare earths concentrate, bastnasite, and ionic adsorption deposit in China was reviewed. The R & D circumstance and new progresses in s...In this paper, the recent advance of processes for treating Baotou mixed-type rare earths concentrate, bastnasite, and ionic adsorption deposit in China was reviewed. The R & D circumstance and new progresses in separation and purification of individual and high purity RE compounds in China were introduced. Moreover, the development of RE hydrometallurgy was also predicted. So we suggest to enhance the research and development of products applying RE, especially Ce, Y, Gd, Sm etc., for keeping RE consumption equilibrium and extending applications, to increase enterprise's automatic control level for improving the stability and the consistency of the products, and to pay more attention to protection of environment.展开更多
TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of ac...TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of active brilliant red dye X-3B. It is found that TiO_2sols modified by Ce^(4+), Eu^(3+), or Nd^(3+) have the anatase crystalline structure, which areprepared at 70℃. All RE^(n+)-TiO_2 sol samples have uniform nanoparticles with similar morphology,which are homogenously distributed in aqueous colloidal systems. The particle sizes are 10, 8, and12 nm for Nd^(3+)-TiO_2, Eu^(3+)-TiO_2, and Ce^(4+)-TiO_2, respectively. The character of ultrafineand positive charge sol particles contributes to the good adsorption of X-3B dye molecule on thesurface of titania (about 30% X-3B adsorption amount). Experimental results exhibit thatRE^(n+)-TiO_2 sol photocatalysts have the capability to photodegrade X-3B under visible lightirradiation. Nd^(3+)-TiO_2 and Eu^(3+)-TiO_2 show higher photocatalytic activity than Ce^(4+)-TiO_2,which is due to the difference of standard redox potential of RE^(n+)/RE^((n-1)+). RE^(n+)-TiO_2sols demonstrate more excellent interfacial adsorption and photodegradation effects to X-3B thanP_(25) TiO_2 crystallites. Moreover, the degradation mechanism of X-3B is proposed as dyephotosensitization and electron scavenging by rare earth ions.展开更多
In order to intensify the leaching process of rare earth（RE） and reduce the impurities in the leachate, ammonium chloride（NH4Cl） and ammonium nitrate（NH4NO3） were mixed as a compound leaching agent to treat the ...In order to intensify the leaching process of rare earth（RE） and reduce the impurities in the leachate, ammonium chloride（NH4Cl） and ammonium nitrate（NH4NO3） were mixed as a compound leaching agent to treat the weathered crust elution-deposited RE ore. Effects of molar ratio of NH~＋_4Cl and NH_4NO_3, ammonium（NH_4） concentration, leaching agent pH and flow rate on the leaching process of RE were studied and evaluated by the chromatographic plate theory. Leaching process of the main impurity aluminium（Al） was also discussed in detail. Results showed that a higher initial ammonium concentration in a certain range could enhance the mass transfer process of RE and Al by providing a driving force to overcome the resistance of diffusion. pH almost had no effects on the mass transfer efficiency of RE and Al in the range of 4 to 8. The relationship between the flow rate and height equivalent to a theoretical plate（HETP） could fit well with the Van Deemter equation, and the flow rate at the lowest HETP was determined. The optimum conditions of column leaching for RE and Al were 1：1（molar ratio） of NH_4Cl and NH_4NO_3, 0.2 mol/L of ammonium concentration, pH 4–8 of leaching agent and 0.5 mL /min of flow rate. Under this condition, the mass transfer efficiency of RE was improved, but no change was observed for Al compared with the most widely used ammonium sulfate. Moreover, the significant difference value（around 20 mL） of retention volume at the peak concentration between RE and Al provided a possibility for their separation. It suggested the potential application of the novel compound leaching agent（NH_4Cl/NH_4NO_3）. It was found that the relative concentration of RE in the leachate could be easily obtained by monitoring the pH of leachate.展开更多
Phosphor-converted white light-emitting diode(LED) lighting has gained tremendous achievements since the invention of the InGaN blue LED by Nakamura et al., who won the Nobel Physics Prize in 2014.By far, a significan...Phosphor-converted white light-emitting diode(LED) lighting has gained tremendous achievements since the invention of the InGaN blue LED by Nakamura et al., who won the Nobel Physics Prize in 2014.By far, a significant challenge comes from the thermal quenching(TQ) behavior of the present LED phosphors during the high-power LED operation or the updated laser lighting. But systematic research or review on the luminescence quenching character and/or how to realize thermally stable luminescence are lacking. Since TQ is an inherent property of phosphors, it can be diminished by different approaches.This review proceeds from the mechanism of TQ, summarizes previous researches on improving the thermal stability of LED phosphors and also discusses future research opportunities in this field. The developments of the phosphors with properties of high luminance and thermal stability, as well as the improved strategies involved,will benefit the basic researches and applications in high power lighting or high-luminance laser lighting.展开更多
In last 10 years,extensive field inventories were carried out to investigate Polypore species, the major wood decaying fungi in the Changbaishan Nature Reserve of Northeastern China. The following 27 species were trea...In last 10 years,extensive field inventories were carried out to investigate Polypore species, the major wood decaying fungi in the Changbaishan Nature Reserve of Northeastern China. The following 27 species were treated as rare or threathened species: Amylocystis lapponica (Romell) Singer, Anomoporia albolutescens (Romell) Pouzar, Anomoporia bombycina (Fr.) Pouzar, Anomoporia vesiculosa Y.C. Dai & Niemel, Antrodia carbonica (Overh.) Ryvarden & Gilb., Antrodia crassa (P. Karst.) Ryvarden, Antrodiella citrinella Niemel & Ryvarden, Diplomitoporus flavescens (Bres.) Dománski, Donkioporia expansa (Desm.) Kotl. & Pouzar, Gloeophyllum carbonarium (Berk. & M.A. Curtis) Ryvarden, Haploporus odorus (Sommerf.) Bondartsev & Singer, Inonotopsis subiculosa (Peck) Parmasto, Nigroporus ussuriensis (Bondartsev & Ljub.) Y.C. Dai & Niemela, Oxyporus sinensis X.L. Zeng, Parmastomyces taxi (Bondartsev) Y.C. Dai & Niemela, Phellinidium sulphurascens (Pilat) Y.C. Dai, Phellinus vaninii Ljub., Polyporus vassilievae Thorn, Pycnoporellus fulgens (Fr.) Donk, Skeletocutis brevispora Niemela, Skeletocutis ochroalba Niemela, Skeletocutis perennis Ryvarden, Trechispora candidissima (Schwein.) Bondartsev & Singer, Wolfiporia dilatohypha Ryvarden & Gilb., Wolfiporia curvispora Y.C. Dai, Wrightoporia avellanea (Bres.) Pouzar and Wrightoporia lenta (Oveh. & J. Lowe) Pouzar. Polypores are richer in East Asia than in Europe and North America, not only because of destructive galciations and fewer hosts in the latters, but also because of the geography. NE Asia is a link between Europe and North America. Changbaishan Nature Reserve is very rich in polypores, and over 260 species were recorded in the reserve. Some rare species in North America and Europe, for instance, Anomoporia albolutescens, Antrodia crassa, Diplomitoporus flavescens, Inonotopsis subiculosa and Skeletocutis ochroalba etc. were found in Changbaishan Nature Reserve as well, and these species are in fact rare in the earth. Most of the 27 species occurred on fallen trunks or rot展开更多
Trace elements and rare earth elements（REE） of the sulfide minerals were determined by inductively-coupled plasma mass spectrometry.The results indicate that V,Cu,Sn,Ga,Cd,In,and Se are concentrated in sphalerite,Sb...Trace elements and rare earth elements（REE） of the sulfide minerals were determined by inductively-coupled plasma mass spectrometry.The results indicate that V,Cu,Sn,Ga,Cd,In,and Se are concentrated in sphalerite,Sb,As,Ge,and Tl are concentrated in galena,and almost all trace elements in pyrite are low.The Ga and Cd contents in the light-yellow sphalerites are higher than that in the brown and the black sphalerites.The contents of Ge,Tl,In,and Se in brown sphalerites are higher than that in light-yellow sphalerites and black sphalerites.It shows that REE concentrations are higher in pyrite than in sphalerite,and galena.In sphalerites,the REE concentration decreases from light-yellow sphalerites,brown sphalerites,to black sphalerites.The ratios of Ga/In are more than 10, and Co/Ni are less than 1 in the studied sphalerites and pyrites,respectively,indicating that the genesis of the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis associated with hydrothermal genesis.The relationship between LnGa and LnIn in sphalerite,and between LnBi and LnSb in galena,indicates that the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis.Based on the chondrite-normalized REE patterns,δEu is a negative anomaly（0.13-0.88）,andδCe does not show obvious anomaly（0.88-1.31）;all the samples have low total REE concentrations（〈3 ppm） and a wide range of light rare earth element/high rare earth element ratios（1.12-12.35）.These results indicate that the ore-forming fluids occur under a reducing environment.Comparison REE compositions and parameters of sphalerites,galenas,pyrites,ores,altered dolostone rocks,strata carbonates,and the pyrite from Lower Carboniferous Datang Formation showed that the ore-forming fluids might come from polycomponent systems,that is,different chronostratigraphic units could make an important contribution to the ore-forming fluids.Combined with the tectonic setting and previous isotopic geochemistry evidence,we conclude that the ore-deposit genesis展开更多
A series of a-based Mg-Li-A1-Zn-xRE alloys were prepared. These alloys have low density ranging from 1.5 to 1.7 g·cm^-3 and high strength properties. The influence of RE element on the microstructure and the mech...A series of a-based Mg-Li-A1-Zn-xRE alloys were prepared. These alloys have low density ranging from 1.5 to 1.7 g·cm^-3 and high strength properties. The influence of RE element on the microstructure and the mechanical properties of these alloys were studied. The results indicate that the addition of RE （La, Pr, Ce） leads to the formation of rodshaped intermetallic compound Al2Zn2La distributed in the matrix. Al2Zn2La induces reduction of the laminar spacing and causes refinement of the microstructure. Therefore, this compound improves the strength of alloys at a high temperature.展开更多
High-carbon chromium bearing steels with different rare earth (RE) contents were prepared to investigate the effects of RE on inclusions and impact toughness by different techniques. The results showed that RE additio...High-carbon chromium bearing steels with different rare earth (RE) contents were prepared to investigate the effects of RE on inclusions and impact toughness by different techniques. The results showed that RE addition could modify irregular Al2O3 and MnS into regular RE inclusions. With the increase of RE content, the reaction sequence of RE and potential inclusion forming elements should be O, S, As, P and C successively. RE inclusions containing C might precipitate in molten steel and solid state, but the precipitation tem perature was significantly higher than that of carbides in high-carbon chromium bearing steel. For experim ental bearing steels, the volume fraction of inclusions increased steadily with the increase of RE content, but smaller and more dispersed inclusions could be obtained by 0.018% RE content compared with bearing steel without RE, whereas the continuous increase of RE content led to an increasing trend for inclusion size and a gradual deterioration for inclusion distribution. RE addition could improve the transverse impact toughness and isotropy of bearing steel, and for modified highcarbon chrom ium bearing steel by RE alloying, the increase of RE content continuously increased both transverse and longitudinal im pact toughness until excessive RE addition.展开更多
The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by ...The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.展开更多
The differences in the leaching and mass transfer characteristics of ion-adsorption type rare earth ore between rare earth and non-rare earth impurities were investigated. It is determined that the leaching kinetics o...The differences in the leaching and mass transfer characteristics of ion-adsorption type rare earth ore between rare earth and non-rare earth impurities were investigated. It is determined that the leaching kinetics of rare earths （REs）, Mg and Ca could be described by the shrinking-core model. The leaching rate is controlled by inner diffusion and is in the order of Mg 〉 Ca 〉 RE. The apparent activation energy is 8.48, 6.79 and 6.32 kJ·mol^-1, respectively. In leaching system of Al, the leaching efficiency decreases with the increase in temperature because of hydrolysis reactions. The leaching efficiency of aluminum increases firstly and then decreases with the passage of time when the temperature is higher than 35 ℃. Besides, there is a good consistency in leaching characteristics and mass transfer, and the order of the time-to- peak is Mg 〈 Ca 〈 RE 〈 Al. Therefore, rare earth and non-rare earth may be partly separated by expanding the separation coefficient. The research could provide a theoretic basis for the separation of rare earth and non-rare earth impurities. Furthermore, compound leaching with magnesium salt and calcium salt is innovatively proposed to solve the problem of calcium and magnesium nutrient loss in the soil as well as eliminate ammonia-nitrogen emissions from the source.展开更多
Magnesium(Mg)alloys have received an increasing interest in the past two decades for their tremendous application potential.The strength and corrosion resistance levels of common Mg alloys are still relativity low,and...Magnesium(Mg)alloys have received an increasing interest in the past two decades for their tremendous application potential.The strength and corrosion resistance levels of common Mg alloys are still relativity low,and especially they are to be improved simultaneously.The addition of rare earth(RE)to Mg alloys is believed to be beneficial for both the strength and corrosion resistance,and some RE-modified traditional Mg alloys have been studied and some new RE-containing Mg alloys have been developed by now.However,further simultaneous improvements in both strength and anti-corrosion require a better understanding of the behavior and mechanism of RE in Mg alloys.In this review,the common influence mechanisms of RE on mechanical and anti-corrosion properties of Mg alloys are summarized,and the latest research progress of RE-containing Mg alloys with simultaneously improved strength and corrosion resistance are introduced.It is demonstrated that the research on high-strength and high corrosion resistant RE-containing Mg alloys is still immature,and some opinions and suggestions are put forward for the synergetic improvement of the strength and corrosion resistance of Mg alloys,so as to contribute to the further development of Mg alloys with higher performance.展开更多
Magnesium and its alloys are significant superior metallic materials for structural components in automobile and aerospace industries due to their excellent physicomechanical properties.The Mg–rare earth(RE)systems h...Magnesium and its alloys are significant superior metallic materials for structural components in automobile and aerospace industries due to their excellent physicomechanical properties.The Mg–rare earth(RE)systems have attracted great interests because RE additions can improve both the deformability and the strength of Mg alloys through solid solution strengthening and precipitation hardening mechanisms.This paper focuses on the interface stability,together with thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases in Mg–RE alloys.In this paper,the theory and recent advances on Mg–RE alloys,especially for the interface stability,thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases,together with their relationships with micro-structures,and macroscopic properties,are reviewed.By combining the thermodynamics/kinetics integrated simulations with various advanced experimental techniques,“reverse”design of Mg–RE alloys starting from the target service performance is put forward as a kind of scientific paradigm with rational design.展开更多
Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has b...Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy-saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging, heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence： materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR-emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris（8-hydroxyquinolinate） displayed a bright green emission suitable for organic light emitting diodes （OLEDs） was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time-resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such 展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.50934004 and 51404035)
文摘China is the global leader in rare earth （RE） production using hydrometallurgical processes. Advantageous extraction techniques of rare earths from Baotou mixed rare earth minerals, bastnaesite, and ion-adsorption clays of rare earth deposits have been developed in China. The separation and purification technologies have also achieved rapid development. The industrial application processes for rare earth hydrometallurgy were summarized in the present paper. With the large demands and rapid development of rare earths, the issues of resources and environment are more prominent. This review gives an overview of the main processes that were developed in the past toward greener hydrometallurgy of rare earths in China. Based on the development of the rare earth industry, comprehensive utilization and cleaner production should still be focused on in the future, to support the sustainable development.
基金supported by Natural Science Foundation of Heilongjiang Province of China(E2017030,ZD2017010)National Natural Science Foundation of China(51671063,51771060,51871069)+1 种基金Fundamental Research Funds for the Central Universities(HEUCFM181002)Foundation of State Key Laboratory of Rare Earth Resources Utilization(RERU2018017).
文摘Higher strength is always the goal pursued by researchers for the structural materials,especially for the lightweight magnesium(Mg)alloys which generally have relatively low strength at present.From this aspect,the present paper reviews the recent reports of a kind of Mg alloys,i.e.Mg-RE(RE:rare earths,mainly Gd or Y)casting and wrought alloys,which have been able to achieve high strength compared with common or commercial Mg alloys,from the viewpoint and content of the alloy system,alloying constitution,preparation process,tensile strength and each of the main strengthening mechanisms.This review of recent research and developments in high-strength Mg-RE alloys is beneficial for the further design of Mg alloys with higher strength as well as excellent comprehensive performance.
文摘It is known to all that China is abundant in rare earth resources. But rare earth deposits are really not that rare in the earth crest. In the five continents, i.e. Asia, Europe, Australia, North and South America, and Africa, there are about thirty four countries found to have rare earth deposits; Brazil might surpass China and rank the first in rare earth deposits. At present, investment in rare earth production was surged, there have been about 200 projects, and the total production for 25 of them would be more than 170 thousand tons after 2015, a multi-supply system on rare earths is being established worldwide. Cautions on the investment of rare earth production are involved.
基金Project supported by the University of Malaya Research Grant(UMRG,RP013A-13AET)University of Malaya Research Grant(UMRG,RP035A-15AET)
文摘Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of laser claddings are relatively restricted when compared with well-established coating techniques because of their inherent defects identified as cracks, pores and inclusions. Substantial evidence suggests that the incorporation of an appropriate amount of rare earth in laser claddings can remarkably prevent these defects. Additionally, the presence of rare earth in laser claddings can notably enhance tribo-mechanical properties such as surface hardness, modulus of elasticity, fracture toughness, friction coefficient and wear rate. In this literature review, the effect of rare earth in reducing dilution and cracks susceptibility of laser claddings in addition to microstructural refinement attained was examined. Mechanical and tribological properties of these claddings along with their underlying mechanism were discussed in detail. Finally, this article summarizes current applications of laser claddings based on rare earth and was concluded with future research directions.
文摘The existing state and partitioning of rare earth （RE） on weathered ores in Longnan County（LN）, Xingfeng County（XF） and Ninghua County（NH） were characterized systematically by standard geological analytical methods. It is found that RE in the weathered rare earth ores exist as four phases： （a） water soluble, （b） ion-exchangeable, （c） colloidal sediment （oxides）, （d） minerals, in which mainly as ion exchangeable phase, accounting for nearly 80% of total RE, with about 20% in the form of colloid sediment phase and mineral phase, but very little as aqueous soluble phase. These rare earth partitioning were mainly chosen mid-heavy RE elements, occupying above 60%, but not equal in the four phases. The mid-heavy RE elements were primarily enriched in the ion exchangeable phase up to 40%, while the containment of cerium dioxide is below 2 %. The cerium deficiency occurs in the ion exchangeable phase in weathered ore. It results from that the Ce^3＋ is oxidized into Ce^4＋ and changes into CeO2. For LN ore, the containment of Y is high in weathered ore because Y-minerals are abundant in original rock.
基金supported by Science Foundation Ireland as part of the ZEMS project(16/IA/4534).
文摘Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little or no rare earth(or heavy rare earth).Nd-Fe-B magnets have been painstakingly and skillfully optimized for a wide range of applications in which high performance is required at reasonable cost.Sm-Co is the material of choice when high-temperature stability is required,and Sm-Fe-N magnets are making their way into some niche applications.The scope for improvement in these basic materials by substitution has been rather thoroughly explored,and the effects of processing techniques on the microstructure and hysteresis are largely understood.A big idea from a generation ago-which held real potential to raise the record energy product significantly-was the oriented exchange-spring hard/soft nanocomposite magnet;however,it has proved very difficult to realize.Nevertheless,the field has evolved,and innovation has flourished in other areas.For example,electrical personal transport has progressed from millions of electric bicycles to the point where cars and trucks with electrical drives are becoming mainstream,and looks ready to bring the dominance of the internal combustion engine to an end.As the limitations of particular permanent magnets become clearer,ingenuity and imagination are being used to design around them,and to exploit the available mix of rare earth resources most efficiently.Huge new markets in robotics beckon,and the opportunities offered by additive manufacturing are just beginning to be explored.New methods of increasing magnet stability at elevated temperature are being developed,and integrated multifunctionality of hard magnets with other useful properties is now envisaged.These themes are elaborated here,with various examples.
基金Project supported by the National Science Foundation of China (50374015)
文摘In this paper, the recent advance of processes for treating Baotou mixed-type rare earths concentrate, bastnasite, and ionic adsorption deposit in China was reviewed. The R & D circumstance and new progresses in separation and purification of individual and high purity RE compounds in China were introduced. Moreover, the development of RE hydrometallurgy was also predicted. So we suggest to enhance the research and development of products applying RE, especially Ce, Y, Gd, Sm etc., for keeping RE consumption equilibrium and extending applications, to increase enterprise's automatic control level for improving the stability and the consistency of the products, and to pay more attention to protection of environment.
基金This work was financially supported by the Hi-Tech Research and Development Program (863 Program) of China (No. 2002AA302304)the National Natural Science Foundation of China (No. 60121101)the Education Department Foundation of Jiangsu Province (JHOl-
文摘TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of active brilliant red dye X-3B. It is found that TiO_2sols modified by Ce^(4+), Eu^(3+), or Nd^(3+) have the anatase crystalline structure, which areprepared at 70℃. All RE^(n+)-TiO_2 sol samples have uniform nanoparticles with similar morphology,which are homogenously distributed in aqueous colloidal systems. The particle sizes are 10, 8, and12 nm for Nd^(3+)-TiO_2, Eu^(3+)-TiO_2, and Ce^(4+)-TiO_2, respectively. The character of ultrafineand positive charge sol particles contributes to the good adsorption of X-3B dye molecule on thesurface of titania (about 30% X-3B adsorption amount). Experimental results exhibit thatRE^(n+)-TiO_2 sol photocatalysts have the capability to photodegrade X-3B under visible lightirradiation. Nd^(3+)-TiO_2 and Eu^(3+)-TiO_2 show higher photocatalytic activity than Ce^(4+)-TiO_2,which is due to the difference of standard redox potential of RE^(n+)/RE^((n-1)+). RE^(n+)-TiO_2sols demonstrate more excellent interfacial adsorption and photodegradation effects to X-3B thanP_(25) TiO_2 crystallites. Moreover, the degradation mechanism of X-3B is proposed as dyephotosensitization and electron scavenging by rare earth ions.
基金Project supported by the National Natural Science Foundation of China(51274152 and 41472071)the Program for Excellent Young Scientific and Technological Innovation Team of Hubei Provincial Department of Education,China(T201506)
文摘In order to intensify the leaching process of rare earth（RE） and reduce the impurities in the leachate, ammonium chloride（NH4Cl） and ammonium nitrate（NH4NO3） were mixed as a compound leaching agent to treat the weathered crust elution-deposited RE ore. Effects of molar ratio of NH~＋_4Cl and NH_4NO_3, ammonium（NH_4） concentration, leaching agent pH and flow rate on the leaching process of RE were studied and evaluated by the chromatographic plate theory. Leaching process of the main impurity aluminium（Al） was also discussed in detail. Results showed that a higher initial ammonium concentration in a certain range could enhance the mass transfer process of RE and Al by providing a driving force to overcome the resistance of diffusion. pH almost had no effects on the mass transfer efficiency of RE and Al in the range of 4 to 8. The relationship between the flow rate and height equivalent to a theoretical plate（HETP） could fit well with the Van Deemter equation, and the flow rate at the lowest HETP was determined. The optimum conditions of column leaching for RE and Al were 1：1（molar ratio） of NH_4Cl and NH_4NO_3, 0.2 mol/L of ammonium concentration, pH 4–8 of leaching agent and 0.5 mL /min of flow rate. Under this condition, the mass transfer efficiency of RE was improved, but no change was observed for Al compared with the most widely used ammonium sulfate. Moreover, the significant difference value（around 20 mL） of retention volume at the peak concentration between RE and Al provided a possibility for their separation. It suggested the potential application of the novel compound leaching agent（NH_4Cl/NH_4NO_3）. It was found that the relative concentration of RE in the leachate could be easily obtained by monitoring the pH of leachate.
基金Project supported by the National Natural Science Foundation of China(51722202,91622125,51572023)Natural Science Foundation of Beijing,China(2172036)
文摘Phosphor-converted white light-emitting diode(LED) lighting has gained tremendous achievements since the invention of the InGaN blue LED by Nakamura et al., who won the Nobel Physics Prize in 2014.By far, a significant challenge comes from the thermal quenching(TQ) behavior of the present LED phosphors during the high-power LED operation or the updated laser lighting. But systematic research or review on the luminescence quenching character and/or how to realize thermally stable luminescence are lacking. Since TQ is an inherent property of phosphors, it can be diminished by different approaches.This review proceeds from the mechanism of TQ, summarizes previous researches on improving the thermal stability of LED phosphors and also discusses future research opportunities in this field. The developments of the phosphors with properties of high luminance and thermal stability, as well as the improved strategies involved,will benefit the basic researches and applications in high power lighting or high-luminance laser lighting.
文摘In last 10 years,extensive field inventories were carried out to investigate Polypore species, the major wood decaying fungi in the Changbaishan Nature Reserve of Northeastern China. The following 27 species were treated as rare or threathened species: Amylocystis lapponica (Romell) Singer, Anomoporia albolutescens (Romell) Pouzar, Anomoporia bombycina (Fr.) Pouzar, Anomoporia vesiculosa Y.C. Dai & Niemel, Antrodia carbonica (Overh.) Ryvarden & Gilb., Antrodia crassa (P. Karst.) Ryvarden, Antrodiella citrinella Niemel & Ryvarden, Diplomitoporus flavescens (Bres.) Dománski, Donkioporia expansa (Desm.) Kotl. & Pouzar, Gloeophyllum carbonarium (Berk. & M.A. Curtis) Ryvarden, Haploporus odorus (Sommerf.) Bondartsev & Singer, Inonotopsis subiculosa (Peck) Parmasto, Nigroporus ussuriensis (Bondartsev & Ljub.) Y.C. Dai & Niemela, Oxyporus sinensis X.L. Zeng, Parmastomyces taxi (Bondartsev) Y.C. Dai & Niemela, Phellinidium sulphurascens (Pilat) Y.C. Dai, Phellinus vaninii Ljub., Polyporus vassilievae Thorn, Pycnoporellus fulgens (Fr.) Donk, Skeletocutis brevispora Niemela, Skeletocutis ochroalba Niemela, Skeletocutis perennis Ryvarden, Trechispora candidissima (Schwein.) Bondartsev & Singer, Wolfiporia dilatohypha Ryvarden & Gilb., Wolfiporia curvispora Y.C. Dai, Wrightoporia avellanea (Bres.) Pouzar and Wrightoporia lenta (Oveh. & J. Lowe) Pouzar. Polypores are richer in East Asia than in Europe and North America, not only because of destructive galciations and fewer hosts in the latters, but also because of the geography. NE Asia is a link between Europe and North America. Changbaishan Nature Reserve is very rich in polypores, and over 260 species were recorded in the reserve. Some rare species in North America and Europe, for instance, Anomoporia albolutescens, Antrodia crassa, Diplomitoporus flavescens, Inonotopsis subiculosa and Skeletocutis ochroalba etc. were found in Changbaishan Nature Reserve as well, and these species are in fact rare in the earth. Most of the 27 species occurred on fallen trunks or rot
基金supported by the National Basic Research Program of China(grant no.2007CB411402)
文摘Trace elements and rare earth elements（REE） of the sulfide minerals were determined by inductively-coupled plasma mass spectrometry.The results indicate that V,Cu,Sn,Ga,Cd,In,and Se are concentrated in sphalerite,Sb,As,Ge,and Tl are concentrated in galena,and almost all trace elements in pyrite are low.The Ga and Cd contents in the light-yellow sphalerites are higher than that in the brown and the black sphalerites.The contents of Ge,Tl,In,and Se in brown sphalerites are higher than that in light-yellow sphalerites and black sphalerites.It shows that REE concentrations are higher in pyrite than in sphalerite,and galena.In sphalerites,the REE concentration decreases from light-yellow sphalerites,brown sphalerites,to black sphalerites.The ratios of Ga/In are more than 10, and Co/Ni are less than 1 in the studied sphalerites and pyrites,respectively,indicating that the genesis of the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis associated with hydrothermal genesis.The relationship between LnGa and LnIn in sphalerite,and between LnBi and LnSb in galena,indicates that the Tianqiao Pb-Zn ore deposit might belong to sedimentary-reformed genesis.Based on the chondrite-normalized REE patterns,δEu is a negative anomaly（0.13-0.88）,andδCe does not show obvious anomaly（0.88-1.31）;all the samples have low total REE concentrations（〈3 ppm） and a wide range of light rare earth element/high rare earth element ratios（1.12-12.35）.These results indicate that the ore-forming fluids occur under a reducing environment.Comparison REE compositions and parameters of sphalerites,galenas,pyrites,ores,altered dolostone rocks,strata carbonates,and the pyrite from Lower Carboniferous Datang Formation showed that the ore-forming fluids might come from polycomponent systems,that is,different chronostratigraphic units could make an important contribution to the ore-forming fluids.Combined with the tectonic setting and previous isotopic geochemistry evidence,we conclude that the ore-deposit genesis
基金Project supported by Heilongjiang Province Key Technologies R&D Project (GC06A212)
文摘A series of a-based Mg-Li-A1-Zn-xRE alloys were prepared. These alloys have low density ranging from 1.5 to 1.7 g·cm^-3 and high strength properties. The influence of RE element on the microstructure and the mechanical properties of these alloys were studied. The results indicate that the addition of RE （La, Pr, Ce） leads to the formation of rodshaped intermetallic compound Al2Zn2La distributed in the matrix. Al2Zn2La induces reduction of the laminar spacing and causes refinement of the microstructure. Therefore, this compound improves the strength of alloys at a high temperature.
基金financially supported by the National Natural Science Foundation of China (Nos. U1508215 and U1708252)the National Key Research and Development Program (No. 2016YFB0300401)
文摘High-carbon chromium bearing steels with different rare earth (RE) contents were prepared to investigate the effects of RE on inclusions and impact toughness by different techniques. The results showed that RE addition could modify irregular Al2O3 and MnS into regular RE inclusions. With the increase of RE content, the reaction sequence of RE and potential inclusion forming elements should be O, S, As, P and C successively. RE inclusions containing C might precipitate in molten steel and solid state, but the precipitation tem perature was significantly higher than that of carbides in high-carbon chromium bearing steel. For experim ental bearing steels, the volume fraction of inclusions increased steadily with the increase of RE content, but smaller and more dispersed inclusions could be obtained by 0.018% RE content compared with bearing steel without RE, whereas the continuous increase of RE content led to an increasing trend for inclusion size and a gradual deterioration for inclusion distribution. RE addition could improve the transverse impact toughness and isotropy of bearing steel, and for modified highcarbon chrom ium bearing steel by RE alloying, the increase of RE content continuously increased both transverse and longitudinal im pact toughness until excessive RE addition.
基金Project supported by the National Basic Research Program of China(2004CB2178062005CB221402)+1 种基金the National NaturalScience Foundation of China(20373043)Young Scientists Innovation Foundation of CNPC(04E7025)
文摘The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.
基金financially supported by the National Science and Technology Support Program of China(No.2012BAE01B02)
文摘The differences in the leaching and mass transfer characteristics of ion-adsorption type rare earth ore between rare earth and non-rare earth impurities were investigated. It is determined that the leaching kinetics of rare earths （REs）, Mg and Ca could be described by the shrinking-core model. The leaching rate is controlled by inner diffusion and is in the order of Mg 〉 Ca 〉 RE. The apparent activation energy is 8.48, 6.79 and 6.32 kJ·mol^-1, respectively. In leaching system of Al, the leaching efficiency decreases with the increase in temperature because of hydrolysis reactions. The leaching efficiency of aluminum increases firstly and then decreases with the passage of time when the temperature is higher than 35 ℃. Besides, there is a good consistency in leaching characteristics and mass transfer, and the order of the time-to- peak is Mg 〈 Ca 〈 RE 〈 Al. Therefore, rare earth and non-rare earth may be partly separated by expanding the separation coefficient. The research could provide a theoretic basis for the separation of rare earth and non-rare earth impurities. Furthermore, compound leaching with magnesium salt and calcium salt is innovatively proposed to solve the problem of calcium and magnesium nutrient loss in the soil as well as eliminate ammonia-nitrogen emissions from the source.
基金This work was supported by National Natural Sci-ence Foundation of China(51871069)Domain Foundation of Equipment Advance Research of 13th Five-year Plan(61409220118)Science and technology innovation ma-jor project of Ningbo City(2019B10103).
文摘Magnesium(Mg)alloys have received an increasing interest in the past two decades for their tremendous application potential.The strength and corrosion resistance levels of common Mg alloys are still relativity low,and especially they are to be improved simultaneously.The addition of rare earth(RE)to Mg alloys is believed to be beneficial for both the strength and corrosion resistance,and some RE-modified traditional Mg alloys have been studied and some new RE-containing Mg alloys have been developed by now.However,further simultaneous improvements in both strength and anti-corrosion require a better understanding of the behavior and mechanism of RE in Mg alloys.In this review,the common influence mechanisms of RE on mechanical and anti-corrosion properties of Mg alloys are summarized,and the latest research progress of RE-containing Mg alloys with simultaneously improved strength and corrosion resistance are introduced.It is demonstrated that the research on high-strength and high corrosion resistant RE-containing Mg alloys is still immature,and some opinions and suggestions are put forward for the synergetic improvement of the strength and corrosion resistance of Mg alloys,so as to contribute to the further development of Mg alloys with higher performance.
基金This work was supported by the National Natural Foundation China(51671118 and 51871143)the Science and TechnologyCommittee of Shanghai(19010500400).
文摘Magnesium and its alloys are significant superior metallic materials for structural components in automobile and aerospace industries due to their excellent physicomechanical properties.The Mg–rare earth(RE)systems have attracted great interests because RE additions can improve both the deformability and the strength of Mg alloys through solid solution strengthening and precipitation hardening mechanisms.This paper focuses on the interface stability,together with thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases in Mg–RE alloys.In this paper,the theory and recent advances on Mg–RE alloys,especially for the interface stability,thermodynamics and kinetics of nucleation and growth of the key phases and matrix phases,together with their relationships with micro-structures,and macroscopic properties,are reviewed.By combining the thermodynamics/kinetics integrated simulations with various advanced experimental techniques,“reverse”design of Mg–RE alloys starting from the target service performance is put forward as a kind of scientific paradigm with rational design.
基金Project supported by the Swiss National Science Foundation
文摘Trivalent lanthanide ions display fascinating optical properties. The discovery of the corresponding elements and their first industrial uses were intimately linked to their optical properties. This relationship has been kept alive until today when many high-technology applications of lanthanide-containing materials such as energy-saving lighting devices, displays, optical fibers and amplifiers, lasers, responsive luminescent stains for biomedical analyses and in cellulo sensing and imaging, heavily rely on the brilliant and pure-color emission of lanthanide ions. In this review we first outlined the basics of lanthanide luminescence with emphasis on f-f transitions, the sensitization mechanisms, and the assessment of the luminescence efficiency of lanthanide-containing emissive molecular edifices. Emphasis was then put on two fast developing aspects of lanthanide luminescence： materials for telecommunications and light emitting diodes, and biomedical imaging and sensing. Recent advances in NIR-emitting materials for plastic amplifiers and waveguides were described, together with the main solutions brought by researchers to minimize non-radiative deactivation of excited states. The demonstration in 1999 that erbium tris（8-hydroxyquinolinate） displayed a bright green emission suitable for organic light emitting diodes （OLEDs） was followed by realizing that in OLEDs, 25% of the excitation energy leads to singlet states and 75% to triplet states. Since lanthanide ions are good triplet quenchers, they now also play a key role in the development of these lighting devices. Luminescence analyses of biological molecules are among the most sensitive analytical techniques known. The long lifetime of the lanthanide excited states allows time-resolved spectroscopy to be used, suppressing the sample autofluorescence and reaching very low detection limits. Not only visible lanthanide sensors are now ubiquitously provided in medical diagnosis and in cell imaging, but the feasibility of using NIR emission of ions such
