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.

Heavy metal free primers: Polymorphism of gadolinium and titanium in the context of GSR glass phase

The possibility of identifying gunshot residue (GSR) particles produced by non-toxic primers containing only titanium and zinc is a very difficult task using SEM/EDX analysis employed in the analysis of GSR originating from primers containing lead, barium and antimony. However, Bauer et al. demonstrated that non-toxic (TieZn) primers form a TiZn2O4 spinel crystalline structure using SEM/EDX with EBSD (Electron Back Scatter Diffraction) and TKD (Transmission Kikuchi Diffraction), whereas GSR originating from gadolinium-doped TieZn primers form a non-crystalline glass phase. Here, a possible explanation of these different phenomena is hypothesized.

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.

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.

Cycloaddition Reactions of Epoxides and CO_(2)Catalyzed by Bifunctional Rare-Earth Metal Complexes Bearing Amino-Bridged Tris(phenolato)Ligands

Eight zwitterionic rare earth metal complexes stabilized by amino-bridged tris(phenolato)ligands bearing quaternary ammonium side-arms were synthesized and characterized.These complexes were used as single-component catalysts for the cycloaddition of CO_(2)and epoxides,and their catalytic activities are obviously higher than those of their binary analogues.Further studies revealed that the halide anions(Cl^(–),Br^(–),I^(–))and the metal complexes influenced the catalytic activity,and the lanthanum complex bearing iodide anion showed the highest catalytic activity for this addition reaction.A variety of mono-substituted epoxides were converted to cyclic carbonates in good to excellent yields(55%—99%)with high selectivity(>99%)at 30℃and 1 bar CO_(2),whereas internal epoxides required higher both reaction temperatures(60—120℃)and catalyst loading(2 mol%)for high yields.The catalyst was recyclable for four times without noticeable loss of catalytic activity.Based on the results of kinetic studies and in℃situ IR reactions,a plausible reaction mechanism was proposed.

电感耦合等离子体光谱快速自动曲线校正技术测定铀钆氧化物中5种金属杂质

建立电感耦合等离子体发射光谱快速自动曲线校正技术(FACT)测定铀钆氧化物中微量金属杂质元素的分析方法。通过对分析物谱线、干扰物谱线以及空白谱线的分析,选择元素最佳分析线,利用谱线校正扣减干扰物谱线,实现在高含量钆基体条件下对目标元素分析线进行干扰校正,准确测定元素含量。样品用硝酸溶解后,以磷酸三丁酯萃淋树脂作为固定相,3 mol/L硝酸溶液为流动相将铀分离。采用标准曲线法,利用FACT模型校正钆基体干扰,准确测量溶液中目标元素的含量。对FACT模型的有效性进行了考察和验证,确定目标元素的测量范围,元素加标回收率为84%~109%,测定结果的相对标准偏差为0.56%~7.07%(n=6)。该方法可用于含钆铀氧化物中微量金属杂质的检测。

Kinetics of Glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk Metallic Glass

Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter （DSC） was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.

金属钆有机框架化合物的合成与显现手印的研究

本文是以溶剂热法合成铕金属有机框架化合物的实验为基础,实验将铕改成与其同一周期的金属钆和镨,分别将两者合成的化合物烘干、研磨,然后使用扫描电镜对合成的化合物SEM表征,再使用其对指纹进行刷显并且与传统荧光粉末进行比对。实验结果表明:合成的金属钆有机框架化合物呈黄褐色,且能够较好的显现指纹;金属镨有机框架化合物成淡绿色,且难以研磨成近似粉末状,所以无法使用其来刷显指纹。

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).

含钆聚酰亚胺中子屏蔽材料的制备及性能分析

通过硅烷偶联剂对氧化钆(Gd_(2)O_(3))进行表面改性处理制备了改性氧化钆(M-Gd_(2)O_(3));采用水热法合成了Gd-MOF[Gd_(4)(1,2,4,5-BTEC)_(3)];将聚酰亚胺(PI)分别与Gd_(2)O_(3)、M-Gd_(2)O_(3)、Gd-MOF耦合制备了Gd_(2)O_(3)/PI、M-Gd_(2)O_(3)/PI、Gd-MOF/PI 3种复合屏蔽材料。通过SEM、EDS、FT-IR、TGA对复合屏蔽材料进行表征,结果表明,成功实现了M-Gd_(2)O_(3)与Gd-MOF的合成;在钆质量分数为4%时,3种复合屏蔽材料的T_(5%)均在500℃以上;随着钆质量分数的进一步提高,3种复合屏蔽材料的热稳定性均出现不同程度的下降。拉伸试验结果表明,在钆质量分数为4%时,3种复合屏蔽材料的断裂强度相较于纯PI有不同程度的提升。通过现场实验测量和SuperMC模拟研究了复合材料的热中子屏蔽性能,Gd质量分数为4%的Gd-MOF具有高屏蔽性能、高耐热性。

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).

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.

氢等离子体电弧熔炼对稀土金属Gd凝固组织和硬度的影响

采用氢等离子体作热源熔化、精炼稀土金属钆(Gd),并采用双辊薄带连铸制备Gd金属带。研究了等离子气中氢气比例、双辊连铸角速度和轧制及热处理工艺对金属Gd凝固组织和硬度的影响。结果表明:增大等离子气中氢气比例、减小双辊连铸角速度,金属Gd中杂质去除率升高,凝固组织晶粒尺寸增大;延长退火保温时间,组织粗化、显微硬度降低。热处理后轧制,金属Gd组织明显细化、显微硬度升高,能满足靶材对晶粒尺寸的要求。

Gd对AZ81镁合金显微组织的影响

利用光学显微镜、电子扫描、X射线衍射分析方法研究Gd对AZ81镁合金显微组织的影响。结果表明,合金的显微组织主要由α-Mg基体、β-Mg17Al12相、Al2Gd相组成。Gd的加入使β-Mg17Al12相显著减少,Gd含量较低时AZ81镁合金的晶粒得到细化、组织较为均匀。随Gd的增加,β-Mg17Al12相有粗化、偏聚的趋势。

碳纳米管-Mg_(65)Cu_(25)Gd_(10)非晶复合材料玻璃转变的动力学性质

制备了Mg65Cu25Gd10大块非晶合金及其碳纳米管(CNTs)复合材料,对两种材料进行了不同扫描速率下的差热扫描量热分析,研究了加入CNTs对材料玻璃转变和晶化动力学效应的影响。结果表明:加入CNTs后,复合材料的玻璃转变和晶化行为仍然具有动力学效应,但加入的CNTs减小了材料晶化行为对升温速率的依赖程度;同时,加入CNTs加大了材料发生玻璃转变时需要克服的能量势垒,增大了峰值温度时的晶化反应速率常数,从而降低了材料的玻璃形成能力(GFA);对CNTs降低GFA的原因也进行了探讨。

用差示扫描量热法测定金属Gd的比热容

采用差示扫描量热(DSC)法测定了金属Gd的比热容,测量结果与已有文献的结果基本一致.根据德拜理论拟合比热容实验曲线确定Gd的晶格比热容,从而分离出Gd的磁比热容,得到相变点附近相对磁熵随温度的变化关系.室温附近Gd的最大磁熵变为4.7J·mol-1·K-1.

真空蒸馏法制备高纯金属钆

在10^-1～5×10^-3Pa真空条件下及2073—2173K温度范围内对金属钆的蒸馏速度进行了理论计算和试验测定，测试了不同坩埚材料的使用寿命，探讨了坩埚材料对蒸馏速度的影响及真空蒸馏法制备高纯钆的杂质去除效果。

金属钆中钨的演化迁移行为与调控

以氟化钆为原料,金属钙为还原剂,在真空感应炉内,用钙热还原和XRD法研究了金属钆中钨的来源、形态、分布、演化迁移行为和调控方法。结果表明,金属钆中钨主要来源于坩埚,以熔解态钨和夹杂物Gd_2(WO_4)_3两种形态存在。钨在金属钆铸锭的下表面中心区域位置发生偏聚,含量最高,上表面二分之一半径处含量最低。演化迁移行为主要有两条途径,单质钨经脱落、熔解、熔体中迁移再分配、铸模内向中心和底部迁移;单质钨被氧化为氧化钨后,进入熔体与钆结合为Gd_2(WO_4)_3、铸模内向中心和底部迁移。从钨坩埚致密性、熔炼氛围、炉内残余氧量、原辅料纯度和升降温制度等方面调控后,可获得平均钨含量为0.008%的金属钆。