METASTABLE EXTENSION OF SOLID SOLUBILITY OF RARE-EARTH ELEMENTS IN Al

The splat folis of Al-RE(RE=Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Er and Yb)binary alloys of 0.04—0.06 mm thickness were made by are-melting and hammer-anviltechnique,the.cooling rate is in 10~6 K/s order of magnitude.The metastable extendedsolid solubilities of these RE elements have been evaluated by measurements of the latticespacings of the rapidly solidified(RS)Al-RE alloys,they are 0.4,0.15,0.21,0.21,0.3,0.5,0.1,0.6,0.65,0.7,0.75,0.2 at.-% for above individual RE clements,respectively.Thesecondary phase in RS Al-RE alloys were identified to be Al_4RE for alloys containinglight RE and Eu elements and Al_3 RE for alloys containing heavy RE and Y elements.Some factors influencing the extension of solid solubility of Al-RE alloy were discussed.     

稀土元素在Al中固溶度亚稳扩展研究

采用锤—砧技术制备了厚0.04—0.06mm快速凝固Al—RE(RE=Y,La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Er,Yb)合金箔试样,冷却速度达10~6K/s,用点阵参数法测得上述稀土元素在Al中亚稳扩展固溶度分别为0.4,0.15,0.21,0.21,0.3,0.5,0.1,0.6,0.65,0.7,0.75和0.2at.—%测定了Al—轻稀土(包括Eu)系中第二相是Al_4RE;Al—重稀土(包括Y)系中第二相是Al_3RE,原子尺寸因素是控制RE在Al中固溶度亚稳扩展的主要因素。     

RE-X二元合金相图的热力学数据库

利用CALPHAD方法,采用亚正规溶体模型、亚点阵模型以及理想气体模型来描述RE-X(Ag,Bi,Cr,Mn,Mo,V,Zn)中二元系各相的Gibbs自由能,并结合相平衡及热力学性质的实验结果,对Ag-RE(RE:Sc,Y Nd,Sm,Gd,.Tb,Ho,Er)、Bi-RE(RE:Nd,Tm,Er,Ho,Pr,Gd)、...     

Microstructure of Al3Sc with ternary rare-earth additions

The microstructure of ternary L1₂-Al₃(Sc_1?yRE_y) intermetallics, where RE is one of the rare-earth elements selected from five light (La, Ce, Nd, Sm or Eu) or two heavy lanthanoids (Yb or Lu), was investigated as a function of RE concentration for 0.02 ≤ y ≤ 0.75. Alloys with light RE show two phases: L1₂-Al₃(Sc,RE) and D0₁₉-Al₃(RE,Sc) (or C11_b-Al₄(Eu,Sc)). Alloys with heavy RE exhibit a single L1₂-Al₃(Sc,RE) phase. The maximum RE solubility in the L1₂ phase is very low (<0.4 at.%) for La, Ce, Nd and Eu, low (3.2 at.%) for Sm and complete solid-solution for Yb and Lu. Both lattice parameter and hardness of the L1₂-Al₃(Sc,RE) phases increase linearly with Sm, Yb or Lu concentration, and the magnitude of both effects correlates with the atomic size mismatch between Sc and RE.     

山西孝义铝土矿矿床地球化学特征

孝义铝土矿床的地球化学研究显示,矿床中Al2O3与TiO2含量成正相关关系,与SiO2、CaO、Fe2O3含量成负相关关系;微量元素B、Li、Pb、Bi、Sb、Nb、Th、U不断富集;Sr/Ba、Th/U比值和B、Be、Ga元素的特征值表明沉积环境以海相为主,间或有陆相堆积特征;不同岩、矿石的稀土总量(∑REE)含量变化大,LREE/HREE均大于1,显示轻稀土较富集,δEu、δCe均显负异常.氢、氧、硫同位素组成说明本矿成矿母岩在成矿初期曾经历过红土风化作用,形成于泻湖海湾环境封闭半封闭环境.     

A new partitioning process for high-level liquid waste by extraction chromatography using silica-substrate chelating agent impregnated adsorbents

To separate the long-lived minor actinides (MA(III) = Am(III), Cm(III)) and some specific fission products (FP) such as Pd(II), Mo(VI), Cs(I) and Sr(II) from high-level liquid waste (HLLW), we have been studying a new partitioning process by extraction chromatography using several novel silica-based extraction resins. In this work, we examined the separation behavior of the elements contained in a simulated MA-effluent by the CMPO/SiO₂P packed column. In addition, as an attempt to further isolate Am(III) and Cm(III) from the heavy RE(III) such as Eu(III), Gd(III) and Dy(III) contained in the MA-effluent, we investigated the possibility of separation by using a silica-based cationic exchange resin. Furthermore, to isolate Sr(II) from the HLLW, adsorption and separation performances of Sr(II) and some other FP elements were studied by using a novel silica-based crown ether extraction resin, DtBuCH18C6/SiO₂P. The experimental results demonstrated that the elements in the simulated MA-effluent can be successfully separated to (1) Pd, (2) MA-hRE and (3) Zr–Mo, by CMPO/SiO₂P packed column using water and a dilute DTPA solution as eluents. Am(III) and Cm(III) are expected to be effectively separated from light RE(III) and Y(III) by the SiSCR cationic resin. However, more effective separation between Am(II), Cm(III) and heavy RE(III) such as Eu(III), Gd(III) and Dy(III) needs further approach. DtBuCH18C6/SiO₂P showed a highly selective adsorption for Sr(III) so that the Sr(II) could be completely separated from other FPs except a portion of Ba(II).     

Critical Systematic Evaluation and Thermodynamic Optimization of the Fe-RE System: RE = Gd,Tb, Dy,Ho, Er,Tm, Lu,and Y

As the second part of the thermodynamic study of binary Fe-RE system, critical evaluations and optimizations of all available phase diagrams and thermodynamic data for the Fe-heavy RE (heavy RE = Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y) systems were conducted to obtain reliable thermodynamic functions of all the phases in the systems. In the thermodynamic modeling of the heavy RE systems, systematic variations in the phase diagrams and thermodynamic properties such as the enthalpy of mixing in the liquid state and enthalpy of formation of solid compounds with the atomic number of lanthanide series were observed. These systematic trends were incorporated in the optimization of the Fe-heavy RE system to resolve inconsistencies between available experimental data and to estimate unknown thermodynamic properties. The systematic trends in thermodynamic properties of solid and liquid phases and phase diagram of the entire Fe-RE systems were summarized.     

Partitioning properties of rare earth ores in China

1 IntroductionChinese rare earth resources are dominant in theworld with a total amount up to 80% of the wholeworld resources. Rare earth resources in China notonly have high grade and various types, but also dis-tribute reasonably. There are many rare ea…     

稀土元素对Pd的再结晶特性之影响

用半硬度法和金相观察测定了Pd与若干Pd-RE合金的再结晶温度,用图象法测定了上述合金的再结晶晶粒度。试验结果表明,所有稀土元素明显提高Pd的再结晶温度和细化晶粒,并计论相关的机制。     

Y、Gd对ZA63镁合金组织和力学性能的影响

通过合金制备、微观分析和力学性能测试等方法研究了Y、Gd复合稀土对ZA63镁合金组织和力学性能的影响。结果表明,添加适量RE元素后,ZA63合金中的τ相由半连续网状分布转变为针状或棒状且分布较均匀,ε相由岛状变为细小颗粒状,部分RE元素固溶于τ相中形成Mg-Al-Zn-RE相。随着RE含量的增加,经T6处理后的合金在室温、150℃和175℃下的抗拉强度和伸长率基本都呈先升高后降低的趋势。当RE含量为1.5%时,合金在3个温度下的抗拉强度和伸长率都达到最大值。     

A simulation study of the shape of β′ precipitates in Mg–Y and Mg–Gd alloys

The metastable β′ phase is a key strengthening precipitate phase in a range of Mg–RE (RE: rare-earth elements) based alloys. The morphology of the β′ precipitates changes from a faceted and nearly equiaxed shape in Mg–Y alloys to a truncated lenticular shape in Mg–Gd alloys. In this work, we study effects of interfacial energy and coherency elastic strain energy on the morphology of β′ precipitates in binary Mg–Y and Mg–Gd alloys using a combination of first-principles calculations and phase-field simulations. Without any free-fitting parameters and using the first-principles calculations, CALPHAD databases and experimental characterizations as model inputs (lattice parameters of the β′ phase, elastic constants and chemical free energy of Mg matrix and interfacial energies of the coherent β′/Mg matrix interfaces), the phase-field simulations predict equilibrium shapes of β′ precipitates of different sizes that agree well with experimental observations. Factors causing the difference in the equilibrium shape of β′-Mg₇Y and β′-Mg₇Gd precipitates are identified, and possible approaches to increase the aspect ratio of the β′ precipitates and thus to enhance the strength of Mg–RE alloys are discussed.     

Rare earth ion modified TiO2 sols for photocatalysis application under visible light excitation

TiO2 sols modified by rare earth (RE) ions (Ce^4 , Eu^3 , or Nd^3 ) were prepared by coprecipitation-peptizationmethod. The photocatalysis activity was studied by investigating the photodegradation effects of active brilliant red dye X-3B. It is found that TiO2 sols modified by Ce^4 , Eu^3 , or Nd^3 have the anatase crystalline structure, which are prepared at 70℃. All RE^n -TiO2 sol samples have uniform nanoparticles with similar morphology, which are homogenously distributed in aqueous colloidal systems. The particle sizes are 10.8, and 12 nm for Nd^3 -TiO2, Eu^3 -TiO2, and Ce^4 -TiO2, respectively. The character of ultrafine and positive charge sol particles contributes to the good adsorption of X-3B dye molecule on the surface of titania (about 30% X-3B adsorption amount). Experimental results exhibit that RE^n -TiO2 sol photocatalysts have the capability to photodegrade X-3B under visible light irradiation. Nd^3 -TiO2 and Eu^3 -TiO2 show higher photocatalytic activity than Ce^4 -TiO2, which is due to the difference of standard redox potential of RE^n /RE^(n-1) . RE^n -TiO2 sols demon-strate more excellent interfacial adsorption and photodegradation effects to X-3B than P25 TiO2 crystallites. Moreover, the degradation mechanism of X-3B is proposed as dye photosensitization and electron scavenging by rare earth ions.     

稀土对真空熔结镍基金属陶瓷复合层成分和硬度分布的影响

研究了真空熔结镍基金属陶瓷复合涂层纵截面的微观组织形态、化学组成、相结构，及合金元素与显微硬度的分布特征。结果表明：稀土（Ce＋La）消除了Ni60＋WC涂层中的针状相，改变了析出相的分布形态，增加了熔合带的宽度。稀土改变了涂层的化学组成，提高了Ni、Cr、Si和W的含量；降低了Fe的含量。Ni60＋WC＋RE涂层还析出了新的Cr3Ni5Si2相。两种Ni60＋WC复合涂层显微硬度的最大值都出现在距涂层表面的0．2mm处，稀土明显地提高了复合涂层的显微硬度。     

微量Ca添加对铸造Mg-Sm-Gd基合金显微组织与力学性能的影响（英文）

主要通过透射电子显微镜、高角度环形暗场扫描透射电子显微镜和拉伸测试研究微量Ca元素对Mg-Sm-Gd-Zn-Zr合金显微组织和力学性能的影响。结果表明,Mg-Sm-Gd-Zn-Zr合金中主要第二相为Zn元素富集的Mg₃RE相,Ca元素添加不仅可以细化晶粒,还可以促进Mg₅RE相和溶质原子富集的层错形成。此外,共格界面表明Mg₃RE相可以作为Mg₅RE相的形核位点,这些均有利于合金力学性能的提高。     

Influence of RE elements on the performances of Ni-P coelectrodeposition bath

Through adding the chlorides of La and Ce into Ni-P coelectrodeposition bath, the effects of rare earth （RE） elements on the performances of the bath have been investigated by hull cell tests, far and near cathodes tests, and so on. It is shown that the optimum contents of CeCl3, LaCl3 and their mixture are all 2 g/L. The bright zones of the Ni-P coelectrodeposition bath are greatly widened by the addition of RE, and this effect is more obvious in the low current density range. By the addition of RE, the current efficiency of the Ni-P coelectrodeposition bath is greatly increased. The results also show that RE elements can improve the dispersing capacity of the bath. It can be theoretically deduced that RE ions improve the cathodic polarization degree of Ni-P codeposition. This deduction has been confirmed by the cathodic polarization curves measured in the baths.     

Column leaching process of rare earth and aluminum from weathered crust elution-deposited rare earth ore with ammonium salts

In order to better understand the leaching process of rare earth (RE) and aluminum (Al) from the weathered crust elution-deposited RE ore, the mass transfer of RE and Al in column leaching was investigated using the chromatographic plate theory. The results show that a higher initial ammonium concentration in a certain range can enhance the mass transfer process. pH of leaching agent in the range of 2 to 8 almost has no effect on the mass transfer efficiency of RE, but plays a positive role in the mass transfer efficiency of Al under strong acidic condition (pH<4). There is an optimum flow rate that makes the highest mass transfer efficiency. The optimum leaching condition of RE is the leaching agent pH of 4–8, ammonium concentration of 0.4 mol/L and flow rate of 0.5 mL/min. The mass transfer efficiencies of RE and Al both follow the order: (NH₄)₂SO₄<NH₄Cl<NH₄NO₃, implying the complexing ability of anion.     

掺杂稀土类催化剂对LiAlH4放氢性能和相结构的影响

采用球磨的方式在LiAlH4中分别掺入3种稀土催化剂LaCl3、CeCl3和Ce(SO4)2,研究了稀土催化剂对LiAlH4的相结构和放氢性能的影响。结果表明,在球磨过程中,掺杂Ce(SO4)2对LiAlH4的分解基本没有影响,而掺杂LaCl3和CeCl3则造成LiAlH4部分分解,产生了LiCl和Al3RE（RE=La,Ce）相。在LiAlH4放氢反应中,稀土催化剂的加入均使LiAlH4初始放氢温度降低,特别是Ce(SO4)2使第1步的放氢温度降低了约25 ℃。稀土催化剂有助于加快LiAlH4分解反应速率,提高LiAlH4的放氢性能。     

球墨铸铁中稀土残余量测定的两个问题

球墨铸铁中稀土残余量测定包括测定稀土总量和各个单一稀土元素在总量中所占的比例。阐述了几种常用测量方法的原理,说明稀土总量的测定主要是光度法,应选择对轻重稀土有等吸点的显色剂,从而避免由于试样中稀土组分的不同而带来的误差;而测定单一稀土含量,电感耦合等离子体光谱法更为准确可靠。     

Effects of Gd Addition on the Microstructure and Tensile Properties of Mg-4Al-5RE Alloy Produced by Three Different Casting Methods

This work deals with the effect of 0.67 wt％ Gd addition on the microstructure and tensile properties of Mg-4Al-5RE (where RE represents LaCe mischmetal) alloy produced by sand casting (SC),permanent mold casting (PMC),and high-pressure die casting (HPDC).The results show that Gd addition could refine the grains,but its efficiency decreases by increasing the cooling rate due to the shifting from SC to PMC and finally to the HPDC method.Meanwhile,the acicular Al11RE3 phase is modified into the short-rod or granular-like shape under the three casting conditions.Such refined and modified micro-structures are due to the Al2(Gd,RE) phases,which act as the nucleation sites in both the α-Mg matrix and Al11RE3 phase.Also,the weakening grain refinement effect in the increased cooling rates can be attributed to the narrow constitutional undercooling zone.After Gd addition,the 0.2％ proof strength of the SC and PMC alloys increases by about 16.9％ and 12.7％,respectively,while in the HPDC alloy,it decreases by about 5.9％.The main factor in the strength increment of the SC and PMC alloys is the grain boundary strengthening due to grain refinement which is proved by modeling the related mechanisms,whereas weak secondary phases and grain boundary strengthening mechanisms in the HPDC alloy lead to strength reduction.After Gd addition,the elongation to failure of the SC,PMC,and HPDC alloys is significantly enhanced by about 34.8％,20.2％,and 12.3％,respectively,due to the crack resistance nature of the modified short-rod/granular Al11(RE,Gd)3 phase compared to the acicular one.