25 kA熔盐电解法制备稀土镨钕合金非稀土杂质有效控制的研究

为实现熔盐电解法制备稀土合金工艺大型化、低能耗和高效性,采用25 kA电解电流在氟化物体系中的熔盐电解工艺制备稀土镨钕合金.通过工业实践,探究了电解过程中电解槽结构、电解温度、电流密度、电解质组分、搅炉操作及坩埚材质对电解产品纯度的影响.实验研究确立了25 kA熔盐电解法制备稀土镨钕合金有效控制非稀土杂质含量的工艺参数.      

Na3AlF6-AlF3-Al2O3-CaF2-KCl系铝电解质初晶温度的研究

采用常用的步冷曲线法测量电解质的初晶温度。采用最小二乘法对实验数据进行二次拟合,得到了初晶温度的回归方程。同时,采用二次回归正交试验设计的方法,测定了Na₃AlF₆-AlF₃-3 %Al₂O₃-3 %CaF₂-KCl体系的初晶温度,并对测定数据进行回归分析,得到初晶温度的回归方程。研究结果表明,在铝电解质中添加氯化钾能够降低电解质的初晶温度。本文旨在获得铝电解质初晶温度的基础数据,为提高电流效率、降低生产成本服务。     

Evolution and deformability of inclusions in Al-killed steel with rare earth-alkali metals(Ca or Mg) combined treatment

The quality of stainless steel is closely related to the deformability of inclusions,which is significantly affected by their compositions.The present study first inve stigated the evolution of inclusion compositions in AI-killed steel with rare earth-alkali metals(Ca or Mg) combined treatme nt through four laboratory-scale experiments.The Ce contents in the final steel are 0.0080 wt%,0.015 wt%,0.016 wt% and 0.010 wt%,respectively.The Mg content is 0.0014 wt% in Ce-Mg combined treated steel,and ...     

Electrochemical co-reduction of Y(III) and Al(III) in a fluoride molten salt system and electrolytic preparation of Y–Al intermediate alloys

In this study, a molten salt co-reduction method was proposed for preparing Y–Al intermediate alloys and the electrochemical co-reduction behaviors of Y(III) and Al(III) and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques. The results show that the reduction of Y(III) at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons, which is controlled by the mass transfer rate. The diffusion coefficient of Y(III) in the fluoride salt at a temperature of 1323 K is 5.0238 × 10^?3 cm²/s. Moreover, the thermodynamic properties associated with the formation of Y–Al intermetallic compounds were estimated using a steady-state electrochemical method. Y–Al intermediate alloy containing 92 wt% yttrium was prepared by constant current electrolysis at 1323 K in the LiF–YF₃–AlF₃–Y₂O₃ (6 wt%)–Al₂O₃ (1 wt%) system at a cathodic current density of 8 A/cm² for 2 h. The Y–Al intermediate alloy is mainly composed of α-Y₂Al and Y phases. The development and application of this innovative technology have solved major technical problems, such as a long production process, high energy consumption, and serious segregation of alloy elements at this stage.     

Effect of carbon coating on electrochemical properties of AB3.5-type La-Y-Ni-based hydrogen storage alloys

The superlattice La-Y-Ni-based hydrogen storage alloys have high discharge capacity and are easy to prepare.However,there is still a gap in commercial applications because of the severe corrosion of the alloys in electrolyte and poor high-rate dischargeability(HRD).Therefore,(LaSmY)(NiMnAl)_3.5 alloy was prepared by magnetic levitation induction melting,and then the alloy was coated with different contents(0.1 wt%-1.0 wt%) of nano-carbons by low-temperature sintering with sucrose as th...     

Liquidus Temperatures of Cryolite Melts With Low Cryolite Ratio

The effect of calcium fluoride on liquidus temperatures of the cryolite melts with a low cryolite ratio (CR) was studied. The systems KF-NaF-AlF₃ and KF-LiF-AlF₃ with CRs of 1.3, 1.5, and 1.7 have been investigated. The liquidus curves of systems containing CaF₂ are different and depend on the K/(K + Na) and K/(K + Li) ratios. In potassium cryolite with CRs of 1.3 and 1.5, the calcium fluoride solubility is low and increases with NaF (LiF) concentration.     

Effects of trace ytterbium addition on microstructure,mechanical and thermal properties of hypoeutectic Al–5Ni alloy

Over the past decade, the cast aluminum alloys with excellent mechanical and conductivity properties have emerged as potential materials for thermal management. However, the traditional Al–Si based alloys are difficult to make significant breakthrough in conductivity performance. The hypoeutectic Al–5Ni alloy also possesses sound castability and is expected to be applied in thermal management applications. In this study, the effects of ytterbium (Yb element) at 0–0.5 wt% on the microstructures as well as the electrical/thermal conductivity and mechanical properties of the Al–5Ni alloy were systematically investigated. The experimental results indicate that the addition of Yb at a relatively low amount not only reduces the secondary dendrite arm spacing of the α-Al grains, but also modifies the morphology and distribution of eutectic boundary phase. Moreover, it is found that the dosage of Yb at 0.3 wt% in the Al–5Ni alloy can simultaneously improve the yield strength, ultimate tensile strength and electrical/thermal conductivity. The strengthening and toughening of the Al–5Ni alloy are mainly attributed to the decrease of secondary dendrite arm spacing and the improvement of eutectic phases. The transmission electron microscopy/selected area electron diffraction (TEM/SAED) analysis indicates that the ytterbium in Al–5Ni alloy will form Al₃Yb phase, which mainly agglomerates in the Al₃Ni phase region. This phase is helpful to decrease the solubility of impurity elements (e.g., Fe and Si) in the α-Al matrix, which is beneficial to electrical/thermal conductivity. The value of this study lays foundation for manufacturing Al–Ni alloys with high thermal conductivity and acceptable mechanical properties.     

Continuous preparation of composition-controllable Y–Ni alloy in LiF–YF3–Y2O3 molten salt

The Y–Ni alloy is a primary precursor for the preparation of high-performance La–Y–Ni-based hydrogen storage materials. However, it cannot be produced continuously at low cost, which limits the wide popularization and application of La–Y–Ni-based materials. In this paper, this problem was solved perfectly using electrochemical reduction of Y₂O₃ in the LiF-YF₃ system. It is found that the reversible reduction from Y³⁺ to Y on the W electrode takes only one step, namely a significant soluble–soluble reaction controlled by Y³⁺ diffusion throughout the melt. Four typical signals of square wave voltammetry (SWV) corresponding to different kinds of Y–Ni intermetallic compounds are observed in LiF−YF₃ and LiF–YF₃–Y₂O₃ melts, and reduction potential can become positive with the addition of Y₂O₃, probably because of the formation of more complexes in the melts. Homogeneous Y–Ni alloy samples were produced continuously and prepared via galvanostatic electrolysis by using bargain-price raw material (Y₂O₃) and setting the current density at 10 A/cm² on the nickel electrode, before they were collected into a bottom receiver. A series of analyses including scanning electron microscopy-energy idspersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS), demonstrate that concentration of yttrium in Y–Ni alloy is adjustable within the wide range of 44 wt% to 72 wt% by fine-tuning the electrolysis temperature (875–1060 °C) in the LiF-YF₃ system to ensure the optimal hydrogen storage performance and economic efficiency of La–Y–Ni-based hydrogen-storage materials.     

On some rare-earth germanides

Conclusions We have studied the conditions for obtaining the germanide phases Me₅Ge₃, MeGe, and MeGe₂ for lanthanum, cerium, praseodymium, and neodymium by arc melting in argon.The optimal ratios of the initial components have been established. To obtain digermanides of lanthanum, cerium, and praseodymium we must have a 1% excess of germanium in the initial mixture; to obtain neodymium germanides the initial mixture must have a deficit of 1–3% of Nd₅Ge₃ and NdGe₂ and 1–5% for NdGe.The pyconometric densities and microhardnesses of the germanides have been measured.Translated from Poroshkovaya Metallurgiya, No. 11 (59), pp. 92–96, November, 1967.     

<Emphasis Type="Italic">L</Emphasis><Subscript>3</Subscript>-XANES spectroscopy of the valence-unstable cerium in intermetallic compounds with 3<Emphasis Type="Italic">d</Emphasis> metals

The effective valence of cerium is studied by L ₃-XANES spectroscopy using synchrotron radiation in the following valence-unstable systems with different types of magnetic ordering: a CeNi matrix doped with neodymium, praseodymium, and gadolinium ions in the temperature range 5–300 K and the Ce₂Fe1_{7 − x} Mn _x intermetallic compound. The obtained dependences are discussed in terms of generally accepted models of states with an intermediate valence of rare-earth ions. Possible correlations between the effective valence of cerium and the magnetic properties of the substances are taken into account.     

Corrosion of 12Kh18N10T Steel in the LiCl–KCl–<Emphasis Type="Italic">n</Emphasis>NdCl<Subscript>3</Subscript> Melt

The high-temperature corrosion of a 12Kh18N10T steel in the melt of lithium and potassium chlorides and neodymium trichlorides is investigated at a temperature of 773 K. The NdCl₃ concentration is varied from 0.2 to 5 mol %. In this study, neodymium is an analog of uranium. The composition of the electrolyte is close to the composition of the electrolytes used for processing nitride spent nuclear fuel (SNF). The main investigation technique is gravimetry, which includes aging of the steel in the melt for 1–24 h. Atomic absorption and electron microprobe analyses are also used.     

Electrical and structural studies on (PEO)50-AgCF3SO3: SnO2 nanocomposite gel polymer electrolyte materials

The present work deals with a new series of silver-ion conducting nanocomposite gel polymer electrolytes based on poly (ethylene oxide)₅₀silver triflate, (PEO)₅₀AgCF₃SO₃ incorporated with a nano-sized inorganic filler namely, SnO₂ and a plasticizer, ethylene carbonate (EC) prepared using solution casting technique. Electrical conductivity measurements have been made on thin film polymer electrolyte systems containing (PEO₅₀AgCF₃SO₃: 2wt% SnO₂) + x wt% EC (x = 10, 15, 20, 25 and 30 respectively). It has been found that the room temperature ionic conductivity value enhanced from 3.1 × 10^?6 to 5.4 × 10^?5 S cm^?1 on addition of EC into the chosen nanocomposite system PEO₅₀AgCF₃SO₃: 2wt% SnO₂. The apparent surface morphology has been examined through scanning electron microscopic (SEM) analysis. The occurrence of a reduction in the degree of crystallinity of the plasticized system has also been revealed from the observed X-ray diffraction (XRD) data.     

Preparation and casting of metal-particulate non-metal composites

A new process for the preparation and casting of metal-particulate non-metal composites is described. Particulate composites of ceramic oxides and carbides and an Al-5 pet Si-2 pct Fe matrix were successfully prepared. From 10 to 30 wt pct of A1₂O₃, SiC, and up to 21 wt pct glass particles, ranging in size from 14 to 340 ώ were uniformly distributed in the liquid matrix of a 0.4 to 0.45 fraction solid slurry of the alloy. Initially, the non-wetted ceramic particles are mechanically entrapped, dispersed and prevented from settling, floating, or agglomerating by the fact that the alloy is already partially solid. With increasing mixing times, after addition, interaction between the ceramic particles and the liquid matrix promotes bonding. Efforts to mix the non-wetted particles into the liquid alloy above its liquidus temperature were unsuccessful. The composite can then be cast either when the metal alloy is partially solid or after reheating to above the liquidus temperature of the alloy. End-chilled plates and cylindrical slugs of the composites were sand cast from above the liquidus temperature of the alloy. The cylindrical slugs were again reheated and used as starting material for die casting. Some of the reheated composites possessed “thixotropy.” Distribution of the ceramic particles in the alloy matrix was uniform in all the castings except for some settling of the coarse, 340ώ in size, particles in the end-chilled cast plates.     

Preparation of hybrid perovskite-type Li0.33La0.56TiO3 by adding ionic liquids

Perovskite-type Li_0.33La_0.56TiO₃ (LLTO) shows greater advantages than organic liquid electrolytes to be used in all-solid-state lithium-ion batteries with high energy densities. Ionic liquid [BMIM][BF₄] was used to improve the properties of Li_0.33La_0.56TiO₃ by attrition milling in this study. The microstructure, crystallinity and lithium-ion conductivity of the samples were measured by scanning electron microscopy (SEM), X-ray diffraction (XRD), and impedance spectroscopy (IS). The total ionic conductivities of the samples LLTO + x wt% [BMIM][BF₄] increase upon adding [BMIM][BF₄] and the maximum conductivity reaches 4.71 × 10⁻⁴ S/cm when x = 12.5 wt%. The enhancement of the total conductivity is ascribed to the bridging role of the ionic liquid among grains, as evidenced by the low activation energy of 0.17–0.25 eV and the SEM observation. The Li⁺ transference numbers of the hybrid samples are all lower than that of the pure LLTO, indicating the existence of electronic conductions. The hybrid material with a mixed conductivity and good stability in the atmosphere can find uses in all-solid-state lithium-ion batteries to improve the interface contact between electrolytes and electrodes.     

Ultrasonic-Assisted Soldering of 5056 Aluminum Alloy Using Quasi-Melting Zn-Sn Alloy

To obtain sound butt-joints of 5056 aluminum alloy rods, ultrasonic-assisted soldering was conducted using Zn-18Sn and Zn-60Sn alloys. Each solder foil was inserted between rods of 5056 aluminum alloy. Ultrasonic vibration was propagated to faying surfaces at soldering temperatures below the liquidus temperature of the solder alloys, and then the samples were air cooled to room temperature. The optimum vibration time at the soldering temperature must be more than 2 seconds to have complete wetting and less than 4 seconds to avoid excessive dissolution of the 5056 alloy. The 5056 alloy joints soldered using quasi-melting. Zn-Sn alloys showed greater strength than the joints soldered at the temperatures over its respective liquidus temperature. As the soldering temperature was increased, the increased formation of the intermetallic compound Mg₂Sn or phases containing Mg generated by dissolution of 5056 into the solder layer decreased the joint strength. Ultrasonic-assisted soldering at an optimum temperature between solidus and liquidus of the Zn-Sn alloys is an important consideration for producing sound joints with sufficient strength.     

Effects of Indium Content on Microstructural,Mechanical Properties and Melting Temperature of SAC305 Solder Alloys

The present study investigated the effects of indium (In) addition on the microstructure, mechanical properties, and melting temperature of SAC305 solder alloys. The indium formed IMC phases of Ag₃(Sn,In) and Cu₆(Sn,In)₅ in the Sn-rich matrix that increased the ultimate tensile strength (UTS) and the hardness while the ductility (% EL) decreased for all In containing solder alloys. The UTS and hardness values increased from 29.21 to 33.84 MPa and from 13.91 to 17.33 HV. Principally, the In-containing solder alloys had higher UTS and hardness than the In-free solder alloy due to the strengthening effect of solid solution and secondary phase dispersion. The eutectic melting point decreased from 223.0°C for the SAC305 solder alloy to 219.5°C for the SAC305 alloy with 2.0 wt% In. The addition of In had little effect on the solidus temperatures. In contrast, the liquidus temperature decreased with increasing In content. The optimum concentration of 2.0 wt % In improved the microstructure, UTS, hardness, and eutectic temperature of the SAC305 solder alloys.     

Development of Wear-Resistant Cu-10Cr-3Ag Electrical Contacts with Nano-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Dispersion by Mechanical Alloying and High Pressure Sintering

Cu-10Cr-3Ag (wt pct) alloy with nanocrystalline Al₂O₃ dispersion was prepared by mechanical alloying and consolidated by high pressure sintering at different temperatures. Characterization by X-ray diffraction and scanning electron microscopy or transmission electron microscopy shows the formation of nanocrystalline matrix grains of about 40 nm after 25 hours of milling with nanometric (<20 nm) Al₂O₃ particles dispersed in it. After consolidation by high pressure sintering (8 GPa at 400 °C to 800 °C), the dispersoids retain their ultrafine size and uniform distribution, while the alloyed matrix undergoes significant grain growth. The hardness and wear resistance of the pellets increase significantly with the addition of nano-Al₂O₃ particles. The electrical conductivity of the pellets without and with nano-Al₂O₃ dispersion is about 30 pct IACS (international annealing copper standard) and 25 pct IACS, respectively. Thus, mechanical alloying followed by high pressure sintering seems a potential route for developing nano-Al₂O₃ dispersed Cu-Cr-Ag alloy for heavy duty electrical contact.     

Behavior of phase transformation of Baotou mixed rare earth concentrate during oxidation roasting

Based on the new process named “Combination Method” for metallurgy and separation of Baotou mixed rare earth concentrate (BMREC), the aim of this paper is to clearly elucidate the phase change behavior of BMREC without additives during oxidative roasting at 450–800 °C. The results indicate that the bastnaesite in BMREC is decomposed at 450–550 °C, the weight loss is about 10.3 wt%, and the activation energy (E) is 144 kJ/mol. The bastnaesite in BMREC is decomposed into rare earth fluoride, rare earth oxides (La₂O₃, Ce₇O₁₂, Pr₆O₁₁ and Nd₂O₃), and CO₂, particularly, with the increase of roasting temperature, bastnaesite in BMREC is more completely decomposed into LaF₃, which causes a decrease in leaching rate of La during the HCl leaching process. Additionally, the maximum cerium oxidation efficiency reaches about 60 wt% when the roasting temperature is equal to or above 500 °C, and the oxidation reaction rate of cerium increases with the increasing roasting temperature.     

Alumina Solubility in KF-NaF-AlF<Subscript>3</Subscript>-Based Low-Temperature Electrolyte

KF-NaF-AlF₃-based electrolyte is a promising low-temperature electrolyte for aluminum reduction. Alumina solubility in molten KF-NaF-AlF₃-based electrolyte was determined as a function of the melt composition and temperature by measuring the weight loss of a rotating corundum disk and by using a LECO RO500 oxygen analyzer (LECO Corporation, St. Joseph, MI). The investigated temperature range is 1023 K to 1073 K (750 °C to 800 °C), and the total cryolite molar ratio (CRt = ([KF] + [NaF])/[AlF₃]) is 1.3 to 1.5; the content of NaF ranges from 0 mol pct to 50 mol pct. The effect of temperature, CaF₂, and LiF on alumina solubility is discussed as well.     

Electrochemical behavior of dysprosium(III) in eutectic LiF-DyF3 at tungsten and copper electrodes

Electrochemical behavior of dysprosium (Dy) ions in LiF-DyF₃ (24 mol%) was investigated by cyclic voltammetry, chronoamperometry and chronopotentiometry. Dy‐Cu alloy samples were prepared by constant-potential electrolysis in LiF-DyF₃ (24 mol%) at the Cu electrode. The Cu₅Dy and Cu phases were characterized by an X-ray diffractometer and a scanning electron microscope equipped with an energy dispersive spectrometer. The results show that the reduction of Dy(III) ions in a LiF-DyF₃ (24 mol%) molten salt system is found to be a quasi-reversible diffusion-controlled process which occurs via a one-step reaction involving the transfer of three electrons. The electro-crystallization processes of the Dy metal at the W electrode and the mode of nucleation confirm that progressive nucleation is dominant at high concentrations of Dy ions in the LiF-DyF₃ salt. At lower concentrations, the instantaneous nucleation of Dy with three-dimensional growth of the nuclei is dominant.