Neutron Diffraction Study of Self-Curing and Self-Crystallization Phenomena of Low-Temperature Dehydrogenating Products of Powder Crystals of Rare-Earth Metals Trihydroxides

The phenomenon of hydrogen thermoemission out of a crystal lattice of powder rare-earth metals trihydrooxides R(OH)3 (R is La, Pr, Nd) was found. The hydrogen thermoemission out of a crystal lattice is partial or full removal of hydrogen out of the crystal lattice of powder hydrogen-containing crystal without change of symmetry of such crystal at continuous evacuation of high vacuum at evacuation temperature of Тev. which is lower than recrystallization Тrecrys. or disintegration (Tdisinteg.) temperature of this crystal: Тev. Тrecrys. Tdisineg.. By neutron diffraction it is found that low- temperature (Тevacuation = 400 - 420 K ) removal of hydrogen (by hydrogen thermoemission) out of a crystal lattice of trihydrooxide R(OH)3 under continuous high vacuum evacuating makes possible to obtain metastable “trioxide” R[O]3. Existence of such substance contradicts to the valence law (oxygen is bivalent and Pr is trivalent in hydroxides). Such “trioxide” has a superfluous negative charge: R3+O6-. So they aspire to “capture” three more protons (hydrogen ions) from a water molecules. Obviously, this substance can be stable at low temperatures and in the mediums, which are not containing hydrogen. In the air at room temperature this substance, most likely, interacting with water molecules, gradually again turns into trihydroxide R(OH)3, compensating the superfluous negative charge by three hydrogen atoms. From this it follows that substance R[O3] can simultaneously be an absorber of hydrogen and generator of oxygen at atmospheric conditions and in any mediums which contains water molecules, without any prior processing like heating or high pressure. Thus, the obtained material, without any prior processing like heating or high pressure, can simultaneously be oxygen generator and hydrogen accumulator in any mediums characteristic of R[O3] to transform into stable form R(OH)3 by selective bonding of hydrogen from the hydrogen-containing environment allowing implication of Pr[O3] as the hydrogen selective absorber. Separation (by low-temperature removal) of hydrogen out of R(OH)3 lattice can again lead to restoration of its capabilities to be a simultaneous hydrogen accumulator and oxygen generator in a medium containing water molecules.

Infrared Polarizabilities of 3d-Transition and Rare-Earth Metals

A transition or rare-earth metal is modeled as the atom immersed in a jellium at intermediate electron gas densities specified by? rs=4.0. The ground states of the spherical jellium atom are constructed based on the Hohenberg-Kohn-Sham density-functional formalism with the inclusion of electron-electron self-interaction corrections of Perdew and Zunger. Static and dynamic polarizabilities of the jellium atom are deduced using time-dependent linear response theory in a local density approximation as formulated by Stott and Zaremba. The calculation is extended to include the intervening elements In, Xe, Cs, and Ba. The calculation demonstrates how the Lindhard dielectric function can be modified to apply to non-simple metals treated in the jellium model.

Mechanism of interaction relation between the rare-earth element Ce and impurity elements Pb and Bi in Ag-based filler metal

The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can be easily produced between these three elements in the filler metal, which greatly limited the formation of the isolated phase Pb or Bi and also eliminated the bad effect of impurity elements Pb and Bi on the spreading property of Ag-based filler metal. The metallurgical and quantum-mechanical bond formation analysis show that a strong chemical affinity was existed between the rare-earth element Ce and impurity elements Pb and Bi, which was proved by the XRD analysis results.

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu_(46)Zr_(47-x)Al_7M_x(M = Ce,Pr,Tb,and Gd) bulk metallic glasses

Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stability, and mechanical properties of Cu46Zr47-xA17Mx were investigated. The GFA of Cu46Zr47-xA17Mx （M = Ce, Pr） alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47-xA17Thx（X = 2, 4, and 5） amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47-xA17Gdx（x = 2, 4, and 5） increases with increasing Gd. Tx and Tp of all decrease. Tg is dependent on the rare-earth element and its content. ATx for most of these alloys decreases except the Cu46Zra2Al7Gd5 alloy. The activation energies △Eg, △Ex, and △Ep for the Cu46Zr42A17Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respec- tively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43A17Pr4 alloy presents the least, Hv 479. The compressive strength （at.f.） of the Cu46Zra3A17Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.

Influence of rare-earth metal doping on the catalytic performance of CuO-CeO_2 for the preferential oxidation of CO in excess hydrogen

Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enhanced the catalytic activity of CuO-CeO2 for PROX. For example, the CO conversion over the above catalyst for PROX was higher than 99% at 120 °C. Especially, the doping of Pr widened the temperature window by 20 °C over CuO-CeO2 with 99% CO conversion. For Nd, Y, and La, the doping depressed the catalytic activity of CuO-CeO2 for PROX. However, the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.

Synthesis of pyrrolidinyl-ethylene fluorenyl rare-earth metal complexes and catalysis for 2-vinylpyridine polymerization

The metathesis reaction between pyrrolidinyl-ethylene fluorenyl lithium salts with in situ prepared cationic rare-earth metal dialkyl species[Ln(CH_(2)SiMe_(3))_(2)(THF)_(x)][BPh_(4)]afford efficiently the corresponding constrained-geometry complexes L^(1)Ln(CH_(2)SiMe_(3))_(2)(L^(1)=FluCH_(2)CH_(2)NC_(4)H_(8),Ln=Y(1a),Lu(1b),Sc(1c))and L^(2)Ln(CH_(2)SiMe_(3))_(2)(L^(2)=(2,7-di-tert-butyl)FluCH_(2)CH_(2)NC_(4)H_(8),Ln=Y(2a),Lu(2b),Sc(2c))in good yields.All these complexes were characterized by NMR spectroscopy,and the solid-state molecular structure of yttrium complex 1a was defined with single-crystal X-ray diffraction analysis.The catalytic performance of these complexes towards 2-vinylpyridine polymerization was investigated,where these complexes alone can efficiently promote the polymerization of 2-vinylpyridine giving isotactic poly(2-vinylpyridine).Upon the activation with[Ph_(3)C][B(C_(6)F_(5))_(4)],the yttrium and lutetium complexes also afford isotactic poly(2-vinylpyridine),while the scandium complexes produce syndiotactic poly(2-vinylpyridine).

Recovery of rare-earth metals from aqueous solutions by bio/adsorption using non-conventional materials:a review with recent studies and promising approaches in column applications

The recovery of rare-earth metals(REMs)is of great economic and environmental interest,because of their high market prices and various industrial applications.Recently,with the increasing demand for high-purity rare-earth compounds,the separation and purification of these elements have gained considerable attention.The bio/adsorption process has been considered an alternative to recover these elements,by its simplicity,low cost and efficiency for recovery of REMs at low concentrations.This review article presents the recent progress regarding REM bio/adsorption published literature in batch system by different non-conventional bio/adsorbents,as well as a critical analysis of the technological challenges to be faced and future prospects.For this purpose,the best application model(isotherm,kinetics),thermodynamic quantities and selection of eluents for desorption studies are also discussed.Additionally,in this review,the application of different bio/adsorbent materials were reviewed extensively in terms of the removal and recovery of REMs in continuous fixed-bed adsorption and regeneration cycles.Finally,future aspects in bio/adsorption research and prospects for commercial applications were discussed.

Unusual selective reactivity of the rare-earth metal complexes bearing a ligand with multiple functionalities

Ligands play a key role in controlling activity of organometallic complexes so that development of new ligands to overcome the challenge is the main topic of modern chemistry.The first example of 1,1-hydride migratory insertion and intramolecular redox reaction has been realized in this work by applying a new ligand in rare-earth metal chemistry.The novel rare-earth metal complexes L^(Mes)RECH2TMS(THF)(RE=Y(1a),Dy(1b),Er(1c),Yb(1d),L^(Mes)=1-(3-(2,6-iPr_(2)C_(6)H_(3)N=CH)C8H4N)-CH_(2)CH_(2)-3-(2-CH2–4,6-Me_(2)C_(6)H_(2))-(N(CH)_(2)NC),THF=tetrahydrofuran)bearing a ligand with imino,indolyl,NHC(N-heterocyclic carbene)multiple functionalities were synthesized and characterized.Treatment of complexes 1 with silanes(PhSiH3or PhSiH2Me or PhSiD3)selectively produced the unprecedented 1,1-hydride(or deuterated H)migratory insertion of the indolyl moiety of the novel unsymmetrical dinuclear rare-earth metal complexes 2.The complex 2a reacts with Ph_(2)C=O to give the selective C=O double bond insertion to the RE–Co-methylene-Mesbond product 3a which further reacts with another Ph_(2)C=O(or DMAP,4-N,N-dimethylaminopyridine)affording the novelμ-η^(2):η^(3)-dianionic 3-iminoindolyl dinuclear rare-earth metal complex 4a.The latter is formed through an unusual intramolecular redox reaction(through electron migration from the 2-carbanion of the indolyl ring to the imino motif)resulting in the re-aromatization of the indolyl ring.

Correlated perovskite nickelates with valence variable rare-earth compositions

While the metal to insulator transition(MIT)of d-band correlated perovskite nickelates(RENiO_(3))are widely adjustable via their rare-earth composition,the roles of potential valence variabilities associated with the rare-earth elements were rarely concerned.Herein,we demonstrate the material synthesis and MIT properties of RENiO_(3) containing valence variable rare-earth compositions,such as Ce,Pr,Sm,Eu and Tb.The metastable perovskite structure of SmNiO_(3) and EuNiO_(3) with a rare-earth valence states variable towards+2 can be effectively synthesized under high oxygen pressures as it is necessary to reduce their formation free energies.This is in contrast to Ce and Tb,in which situations the variable rare-earth valence state towards+4 reduces their ionic radius and prohibits their occupation or co-occupation of the rare-earth site within the perovskite structured RENiO_(3).Nevertheless,PrNiO_(3) with MIT properties can be effectively synthesized at lower oxygen pressures,owing to the higher stability to form a fully occupied 6s orbit associated Pr3+compared to the half-filled one related to Pr4+.The present work provides guidance for regulating the MIT properties of RENiO_(3).

Substituent Effects of Pyridyl-methylene Cyclopentadienyl Rare-earth Metal Complexes on Styrene Polymerization

Salt metathesis reactions between pyridyl-methylene-cyclopentadienyl lithium salt and LnCl_3 followed by the addition of two equivalents of LiCH_2SiMe_3 afforded a series of constrained-geometry-configuration rare-earth metal bis(alkyl) complexes(Cp′CH_2-Py)Ln(CH_2SiMe_3)_2(THF)_n(Py = C_5H_4N, Cp′ = C_5H_4(Cp), Ln = Sc, n = 0(1); Cp′ = C_9H_6(Ind), Ln = Sc, n = 0(2); Cp′ = 3-Me_3Si-C_9H_5(3-Me_3Si-Ind), Ln = Sc, n = 0(3a), Ln = Lu(3b), Y(3c), n = 1; Cp′ = 2,7-(~tBu)_2C_(13)H_8(2,7-(~tBu)_2-Flu), Ln = Sc(4 a), n = 0, Ln = Lu(4b),Y(4c), n = 1) in moderate to good yields, which were characterized by NMR spectroscopy and single-crystal X-ray diffraction(for complex 3a). In the presence of [Ph_3C][B(C_6F_5)_4] and Al^iBu_3, these complexes displayed different performances towards styrene polymerization. Rare-earth metal bis(alkyl) precursors bearing Cp, Ind, and 3-Me_3Si-Ind segments exhibited very low catalytic activity to afford syndiotactic polystyrene. All electron-donating t Bu substituted complexes 4 a, 4 b, and 4 c showed very high activity and perfect syndiotactivity(rrrr > 99%), producing high molecular weight polystyrene(up to 54.1 × 10~4) with relatively narrow molecular distribution(PDI = 1.28-2.49).

Recovery of rare-earth metal neodymium from aqueous solutions by poly-γ-glutamic acid and its sodium salt as biosorbents:Effects of solution pH on neodymium recovery mechanisms

For recovery of metals from low-concentration sources, biosorption is one of promising technologies and poly-γ-glutamic acid（γ-PGA） has been known as a potential biosorbent for recovery of heavy metals from aqueous solutions. Effects of solution pH on recovery of rare-earth metal Nd are systematically examined to clarify mechanisms of Nd recovery by y-PGA and its sodium salt（y-PGANa）. The recovery efficiency of Nd by y-PGA increases from 2.4 to 19.6% as pH increases from 2 to 4. Subsequently the Nd recovery efficiencies for y-PGA and y-PGANa remain almost constant in the range of pH from 4 to 7. For pH 〉 7 the increase in Nd recovery is significant and 100% recovery of Nd is achieved at pH 9. The pH dependency on Nd recovery by y-PGANa is similar to that by y-PGA. Contributions of adsorption and precipitation/coagulation to Nd recovery process are quantified. Whereas the adsorption dominates Nd recovery at lower pH（〈～4）, the precipitation/coagulation controls Nd recovery process for pH 〉 7. At higher pH, purple gel precipitates are observed. The maximum adsorption capacities for γ-PGA and yPGANa are 215 mg-Nd/（g-γ-PGA） at pH 4 and 305 mg-Nd/（g-y-PGANa） at pH 3, respectively. From the spectra of FT-IR and XPS, the biosorption of Nd onto y-PGA and y-PGANa via electrostatic interaction with carboxylate anions at pH 3 is verified. The Nd complexation with amide and carboxylate anion groups on γ-PGA and γ-PGANa may also contribute to the Nd recovery. The biosorption isotherms for Nd recovery by γ-PGA and γ-PGANa can be satisfactorily fitted by the Langmuir model. The thermodynamic studies suggest that the biosorptions of Nd by γ-PGA and γ-PGANa are endothermic. The utilization of γ-PGA and γ-PGANa as potential and eco-friendly biosorbents for the highly effective recovery of Nd from aqueous solution is confirmed.

Research progress in rare earths and their composites based electrode materials for supercapacitors

Supercapacitor is an imminent potential energy storage system,and acts as a booster to the batteries and fuel cells to provide necessary power density.In the last decade,carbon and carbonaceous materials,conducting polymers and transition metal oxide/hydroxide based electrode materials have been made to show a remarkable electrochemical performance.Rare-earth materials have attracted significant research attention as an electrode material for supercapacitor applications based on their physicochemical properties.In this review,rare earth metals,rare earth metal oxides/hydroxides,rare-earth metal chalcogenides,rare-earth metal/carbon composites and rare-earth metal/metal oxide composites based electrode materials are discussed for supercapacitors.We also discuss the energy chemistry of rare-earth metal-based materials.Besides the factors that affect the performance of the electrode materials,their evaluation methods and supercapacitor performances are discussed in details.Finally,the future outlook in rare-earth-based electrode materials is revealed towards its current developments for supercapacitor applications.

Synthesis and characterization of aminophenolate-ligated rare-earth metal amide complexes and their catalytic activity for lactides polymerization

Amine elimination of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with aminophenol H[ON]{H[ON]=2-(CH2 NC5 H10)-4,6-tBu2-C6 H3OH}in 1:2 molar ratio in THF gave the monometallic rare-earth metal amide complexes[ON]2 LnN(SiMe3)2(Ln=Yb(1),Y(2),Gd(3),Sm(4),Nd(5))in 57%-73%isolated yields.All these complexes were characterized by elemental analysis.The molecular structures of complexes 1-4 were determined by single crystal X-ray diffraction.These complexes are highly active for L-Iactide polymerization to give high molecular weight polymers with unimodal molecular weight distributions.In addition,these complexes can also initiate rac-lactide polymerization with high activity to afford heterotactic-rich polylactides.

Rare-earth metal catalysts for alkene hydrosilylation

Rare-earth metal catalyzed hydrosilylation of alkenes has emerged as a powerful and selective strategy for the synthesis of organosilanes. This transformation can offer distinctive catalytic sequences and reaction patterns from other catalysts because of the high electropositivity and lack of oxidative-addition process of rare-earth metal. This review summarizes the rare-earth metal catalysts for hydrosilylation of alkene according to the type of ligands. The synthesis and structure of rare-earth metal catalysts,the substrate scope as well as some preliminary structure-activity relationship and mechanism are discussed.

REVIEW OF THE RESEARCHES ON MAGNETOSTRICTIVE MATERIALS

The recent evolution in researeh on the magnetostrictive materials is briefly reviewed.A cotnpaboon of the relative preperties between bulk and thin film materialS, and theeNcts of addition of elements on the magnetic properties are alSo given.

Syndiotactic Polymerization of Styrene and Copolymerization with Ethylene Catalyzed by Chiral Half-sandwich Rare-earth Metal Dialkyl Complexes

The syndiotactic polymerization of styrene（St） and the copolymerization of St with ethylene（E） were carried out by using a series of chiral half-sandwich rare-earth metal dialkyl complexes（Cp^x＊） as the catalysts. The complexes are Ln（CH2SiMe3）2（THF）（1-4： Ln = Sc（1）, Ln = Lu（2）, Ln = Y（3）, Ln = Dy（4）） bearing chiral cyclopentadienyl ligand containing bulky cylcohexane derivatives in the presence of activator and AliBu3. For the St polymerization, a high activity up to 3.1 × 10^6 g of polymer mol Ln^-1·h^-1 and a high syndiotactic selectivity more than 99% were achieved. The resulting syndiotactic polystyrenes（sPSs） have the molecular weights（Mn） ranging from 3700 g·mol^-1 to 6400 g·mol^-1 and the molecular weight distributions（Mw/Mn） from 1.40 to 5.03. As for the copolymerization of St and E, the activity was up to 2.4 × 10^6 g of copolymer mol Sc^-1·h^-1·MPa^-1, giving random St-E copolymers containing syndiotactic polystyrene sequences with different St content in the range of 15 mol%-58 mol%. These results demonstrate that the bulky cyclopentadienyl ligands of the chiral half-sandwich rare-earth metal complexes effectively inhibit the continued insertion of St monomers into the（co）polymer chain to some extent in comparison with the known half-sandwich rare-earth metal complexes.

Rare-Earth Metal Boroxide with Formal Triple Metal-Oxygen Orbital Interaction:Synthesis from B(C_(6)F_(5))_(3)·H_(2)O and Radical-Anion Ligated Rare-Earth Metal Amides

Rare-earth metal boroxides are not only rare and of great synthetic challenge but also important theoretically due to their unrevealed bonding characteristics.In this paper,we report the synthesis,characterization,and bonding characteristics of the 4f-block metal boroxide complexes ^(Mes)DAD_(2)LuOB(C_(6)F_(5))X(4-Lu,X=C_(6)F_(5);5-Lu,X=NC_(13)H_(10))with two chelating radical-anionic 1,4-diazabutadiene(DAD)ligands.The synthesis of 4-Lu or 5-Lu involved three steps,during which the radical-anionic DAD ligands could be kept stable:(1)the reaction of LuCl_(3),^(Mes)DAD,and potassium graphite(KC8)afforded the diradical rare-earth metal chloride ^(Mes)DAD_(2)LuCl·tetrahydrofuran(THF)(1-Lu);(2)the salt metathesis of 1-Lu with two alkali metal amides gave lutetium bis(diazabutadiene)amides 2-Lu or 3-Lu,respectively;and(3)2-Lu or 3-Lu reacted with B(C_(6)F_(5))_(3)·H_(2)O,resulting in the formation of rare-earth metal boroxides 4-Lu or 5-Lu.The radical-anionic nature of DAD ligands in these complexes were proven by their bond lengths and coordination modes in single-crystal structures.DFT calculations clearly show the bonding of 4-Lu can be divided into three major types of Lu-O orbital interactions,which can be categorized asσ-donation,π-donation,and d-π-conjugation.The triple Lu-O orbital interactions cooperatively make a Lu-O single bond and contribute to the linear Lu-O-B structure.

Preparation & Properties Research of Two Indium Phthalocyanine Materials

Two iodo（phthalocyainato） indium complexes were synthesized and mixed with polymer solution（PMMA/chloroform）to prepare iodo（phthalocyainato）indium/PMMA compound film materials on a glass slice by the method of dipping film.Two materials have typical B-band and Q-band absorption of Phthalocyanine compounds in the UV-Vis spectrum.The reverse saturable absorption experiments show that two materials have better reverse saturable absorption properties while they have higher linear transmissivity.In addition,the highest transmittance of visible light is over 70%（tetrakis（cumylphenoxy）phthalocyainate indium/OMMA compound film material）.The initial threshold is 127.1mJ/cm^2.The dynamic range is 1.43.It can be concluded that introduction of the substituted groups having bigger steric hindrance and conjugative effect in the Phthalocyanine ring may increase the reverse saturable absorption effect of the Phthalocyanine indium material.

Rare-earth Metal Dialkyl Complexes Supported by 1,3-Disubstituted Indolyl Ligand: Synthesis, Characterization and Catalytic Activity for Isoprene Polymerization

Rare-earth metal dialkyl complexes[1-Bn-3-(DippN=CH)C_(8)H_(4)N]RE(CH_(2)SiMe_(3))2(thf)2(Dipp=2,6-iPr_(2)C_(6)H_(3),RE=Y(1)and Er(2))were prepared through the cyclometalation reactions of the N-Bn-3-imino-functionalized indolyl ligand 1-Bn-3-(DippN=CH)C8H5N with one equivalent of rare-earth metal trialkyl precursors.The structures of compounds 1 and 2 were confirmed by X-ray crystal analyses and characterized by elemental analysis,IR,NMR spectroscopy wherein applicable.In the presence of cocatalysts,these rare-earth metal dialkyl complexes initiated isoprene polymerization with a high activity(95% conversion of 2000 equivalent of isoprene in 360 min),producing polymers with high regioselectivity(1,4-polymers up to 91%).

Langmuir-Blodgett film formation of rare-earth metal di-,triphthalocyanine complexes and observation of their thin film by means of TEM and STM

Three different kinds of rare-earth metal phthalocyanine complexes(Pc_2LuH,Pc_3Gd_2, R_(12) Pc_3Dy_2)were synthesized.Their ultra-thin films were prepared by the Langmuir-Blodgett techni- que.Crystallites were observed in Langmuir film of Pc_3Gd_2 by means of transmission electron micros- copy.The limiting molecular areas of the phthalocyanine derivatives on pure water increased in the order mono-,di-and triphthalocyanine,implying that these phthalocyanine molecules are stacked with a face-to-face orientation and edge-on to the water surface.By using scanning tunneling mic- roscopy individual molecules of lutetium diphthalocyanine adsorbed on graphite surfaces were imaged for the first time.