基于低共熔溶剂稀土金属钇、钐、铽的电沉积研究

低共熔溶剂是一种新型离子液体类似物,具有宽的电化学窗口和独特的物理化学性质,在电沉积领域有着潜在的应用前景。本研究提出以氯化胆碱-尿素基低共熔溶剂为介质,系统研究3种稀土金属(钇、钐、铽)在该介质中的电沉积行为,并采用循环伏安法和恒电位法成功实现了稀土金属(钇、钐、铽)的电沉积。研究结果表明,60℃时,在该低共熔溶剂中钇、钐、铽的电沉积过程为扩散控制过程,扩散系数分别为7.3744×10^-13、1.1032×10^-12和9.2936×10^-13 cm²·s^-1,沉积获得的稀土金属钇、钐、铽具有二维纳米网络结构。本研究为稀土金属的电沉积及提炼提供新的策略。     

Accumulation and diffusion of radiogenic helium in beryllium

Accumulation of radiogenic helium isotope ⁴He, its diffusion characteristics, and microstructure of beryllium have been studied after irradiation at 70 and 200°C by neutrons with an energy of E > 0.1 MeV to fluences of (1.0–13.3) × 10²² cm^?2. Experimental results concerning the concentration of radiogenic helium in beryllium after irradiation and subsequent isothermal annealings for 1 h in a temperature range of 700–1200°C have been obtained. The accumulation of helium corresponds to a linear dependence up to a neutron fluence of ～6 × 10²² cm^?2 (E > 0.1 MeV); at fluences from 6 × 10²² to 13 × 10²² cm^?2 (E > 0.1 MeV), a deviation from the linear dependence toward the decrease in the rate of accumulation is observed. The diffusion of radiogenic helium in beryllium at annealing temperatures of 70–200°C is low; intense diffusion and degassing of helium from beryllium start at an annealing temperature of 700°C. At annealing temperatures of 1100–1200°C, virtually all helium escapes from the irradiated beryllium.     

Interdiffusion in the f.c.c. Phase of Cu-Mn Binary Alloys

Interdiffusion coefficients are calculated in the Cu-Mn binary system from 450 to 925?°C. Starting from the diffusion couples between pure Cu and Mn, the solubility limit of the manganese in copper is determined and the interdiffusion characteristics in the f.c.c. solid solution of Cu-Mn alloys are analysed. The interdiffusion coefficients in this binary system are calculated by the den Broeder method. The interdiffusion coefficients are strongly dependent on the composition: their values lie between approximately 10^?14 and 4?×?10^?9?cm²?s in this temperature range. The Vignes and Birchenall method is used to determine the impurity diffusion coefficients of manganese in pure copper. These coefficients are compared with the tracer diffusion coefficients of Mn⁵⁴ in copper from the literature. Activation energies, which lie from 155 to 180?kJ/mol, are of a vacancy controlled diffusion mechanism.     

In-situ synthesis of silicide coatings on molybdenum substrates by electrodeposition in chloride-fluoride molten salts

Silicide coatings including MoSi₂ and Si-MoSi₂ were prepared on molybdenum substrates by electrodeposition in NaCl-KCl-NaF-K₂SiF₆ molten salt. The experimental was conducted under different cathodic current densities at the temperature of 1073 K. The effect of the current density on the microstructure, phase composition, cross-section morphologies and elemental distribution of the as-prepared coatings were investigated by means of SEM, XRD and EDX. The results revealed that the type of the silicide coatings was strongly dependent on the current density and the relevant deposition mechanism was discussed. Besides, the electrochemical behavior of silicon ion in the chloride-fluoride molten salts was also studied using cyclic voltammetry and chronopotentiometry to reveal the electroreduction mechanism. The reduction of Si(IV) to Si was proved to be a quasi-reversible or irreversible diffusion-controlled single-step reaction and the diffusion coefficient of Si(IV) calculated from chronopotentiograms was (1.28 ± 0.25) × 10⁻⁵ cm²·s⁻¹.     

Electrochemical deposition of aluminum on W electrode from AlCl_3-NaCl melts

Electrochemical deposition of aluminum on W electrode from AlCl3-NaCl melts was studied by cyclic voltammetry and chronopotentiometry. The results show that Al ( Ⅲ) is reduced in two consecutive steps, i.e., 4Al2Cl7-+3e-→Al+7AlCl4- and then AlCl4-+3e-→Al+4Cl-. The electrochemical reaction of 4Al2Cl7-+3e-→Al+7AlCl4- is reversible. Certain nucleation overpotential is required during the deposition of aluminum on W electrode. Chronopotentiometry analysis also shows that Al (Ⅲ ) is reduced in two consecutive steps under certain current density, which is in reasonable agreement with cyclic voltammograms. By using constant current deposition, the electrodeposits on Al substrate obtained at between 50 and 100 mA/cm2 are quite dense and well adherent to the Al substrate. The electrochemical deposition of aluminum on Cu substrate in AlCl3-NaCl melts indicates that the intermetallic compounds are formed. The intermetallic compounds are AlCu and Al2Cu.     

Corrosion mechanism of a NiCoCrAlTaY coated Mar-M247 superalloy in molten salt vapour

A mechanism of corrosion is proposed relating to a NiCoCrAlTaY coated Mar-M247 superalloy exposure in molten Na₂SO₄ salt vapour at 900 °C. The corrosion process indicates the parabolic “diffusion controlled” region I at rate of 4.6 × 10^?6 mg² cm^?4 s^?1, the combination of parabolic and linear “reaction–diffusion controlled” region II at rate of 2.28 × 10^?5 mg² cm^?4 s^?1 and 4.35 × 10^?5 mg cm^?2 s^?1, and finally the complete “reaction controlled” region III at the same rate of 3.92 × 10^?4 mg cm^?2 s^?1 as the uncoated superalloy. The corrosion kinetics of each region and of the whole process are formulated rationally associated with the corrosion mechanism.     

Self-dispersed polyaniline derivative extending electrochemical activity to neutral media

Self-dispersed poly-N-[5-(8-quinolinol)ylmethyl]aniline, which can be easily dispersed in some organic solvents without any dispersant, has been prepared by oxidative polymerization of 5-(anilinomethyl)-8-hydroxyquinoline. Although its conductivity only reaches 1.45 × 10^?3 S cm^?1, it possesses good redox reversibility in aqueous electrolyte ranging from pH 1.0 to 7.0, and its cyclic voltammetry curves also show good cycling stability in the aqueous medium of pH 5.0. It will be a promising material for several applications such as biosensors due to increasing the operating pH window in aqueous media.     

Microstructure and Oxidation Behavior of Al and Al/NiCrAlY Coatings on Pure Titanium Alloy

To improve the oxidation resistance of Ti alloys, a NiCrAlY coating was deposited as diffusion barrier between aluminum overlay coating and pure Ti substrate by air plasma spraying method. The microstructure and oxidation behavior of Al coatings with and without NiCrAlY diffusion barrier were investigated in isothermal oxidation tests at 800 °C for 100 h. The results indicate that the weight gain of the Al/NiCrAlY coating was 4.16 × 10^?5 mg² cm^?4 s^?1, whereas that of the single Al coating was 9.52 × 10^?5 mg² cm^?4 s^?1 after 100 h oxidation. As compared with single Al coating, the Al/NiCrAlY coating revealed lower oxidation rate and excellent oxidation resistance by forming thin Al₂O₃ + NiO scales at overlaying coating/diffusion barrier and diffusion barrier/substrate interfaces. Meanwhile, the inward diffusion of Al and the outward diffusion of Ti were inhibited effectively by the NiCrAlY diffusion barrier.     

AZ41镁合金超塑性成形特性

研究AZ41镁合金在热轧(无后续热变形)条件下的显微组织变化,以确定其在超塑性成形工艺中的适用性,并确定最佳成形参数.采用高温拉伸试验和热气体胀形试验对材料在不同应变速率(1×10?1～1×10?3 s?1)和温度(350～450℃)下的成形性进行评估.利用GOM Aramis相机进行圆形网格分析,了解峰值应变和材料减...     

Research and Development Techniques 1: Potentiodynamic Studies of Copper Metal Deposition

The electrochemistry of copper (II)/(I) ions in aqueous chloride solution, at pH2, is used to demonstrate the application of voltammetry techniques in characterising electrode processes. The electrolyte used is 1.5 M sodium chloride containing 20 to 50 × 10^?3 M cupric chloride at 20°C, in which both Cu(II) and Cu(I) ions are stable. A platinum rotating disc electrode (RDE, radius 0.365 cm) is used to provide controlled mass transport under laminar flow conditions. Cyclic voltammetry, at a stationary disc electrode, is used to characterise the general electrochemistry. Four current peaks due to reduction of Cu(II) ions to Cu(I) ions, deposition of Cu from Cu(I) ions, anodic stripping of Cu to form Cu(I) ions and oxidation of Cu(I) ions to Cu(II) ions are seen. Analysis of the Cu(II)/Cu(I) couple indicates a reversible process. A potential sweep rate experiment allows the diffusion coefficient of Cu(II) ions to be calculated. The anodic stripping peak in the cyclic voltammogram is used to estimate the amount of copper deposited. Reduction of Cu(II) to Cu(I) then to Cu is examined at a range of rotation speeds (150–1870 rpm) using linear sweep voltammetry at the RDE. Mass transport data are obtained in the form of limiting current density as a function of the RDE speed, allowing the diffusion coefficients of Cu(II) and Cu(I) ions to be calculated.     

Electrodeposition of dixanthogen（TETD） on pyrite surface

The electrochemical reaction of xanthate on the surface of pyrite was studied using cyclic voltammogrametry, chronopotentiometry and rotating-disc electrode measurements.Experimental results demonstrate that the first step in the reaction is electrochemical adsorption of xanthate ion,and then the adsorbed ion associates with a xanthate ion from the solution and forms a dixanthogen on the pyrite electrode surface.The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.09×10- 6cm2/s.Using the galvanostatic technique,the kinetic parameters of oxidation of the butyl xanthate ion on the pyrite surface are calculated as Ja=200μA/cm2 ,β=0.203 and J0=27.1μA/cm2.     

Electrochemical behavior of tantalum in ethylene carbonate and aluminum chloride solvate ionic liquid

To investigate the electrochemical reduction mechanism of Ta(V) in ethylene carbonate and aluminum chloride (EC−AlCl₃) solvate ionic liquid, cyclic voltammetry experiments were conducted on a tungsten working electrode. Four reduction peaks were observed in the cyclic voltammogram of the EC−AlCl₃−TaCl₅ ionic liquid. The reduction peaks at −0.55, −0.72, and −1.12 V (vs Al) were related to the reduction of Ta(V) to tantalum metal by three stages including the formation of Ta(IV) and Ta(III) complex ions. The reduction of Ta(III) to tantalum metal was an irreversible diffusion-controlled reaction with a diffusion coefficient of 3.7×10⁻⁷ cm²/s at 323 K, and the diffusion activation energy was 77 kJ/mol. Moreover, the cathode products at 323 K were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. The results showed that tantalum metal and tantalum oxides were obtained by potentiostatic electrodeposition at −0.8 V for 2 h.     

Electrochemical behavior of zirconium in molten NaCl-KCl-K<Subscript>2</Subscript>ZrF<Subscript>6</Subscript> system

The electrochemical reduction of Zr4+(complex) ions in NaCl-KCl-K2ZrF6 molten salt on Pt electrode was investigated using cyclic voltammetry and square wave voltammetry at 1023 K.Two cathodic reduction peaks related to Zr4+/Zr2+ and Zr2+/Zr steps were observed in the cyclic voltammograms.The result was also confirmed by square wave voltammetry.The diffusion coefficient of Zr4+(complex) ions at 1023 K in NaCl-KCl-K2ZrF6 melt,measured by cyclic voltammetry,is about 4.22×10-6 cm2/s.The characterization of the deposits obtained by potentiostatic electrolysis at different potentials was investigated by XRD,and the results were well consistent with the electrochemical reduction mechanism of Zr4+(complex) ions.     

Temperature-Dependent Properties of Spray-Deposited ITO Thin Films

Sprayed indium tin oxide (ITO) thin films are synthesized by mixing adequate quantities of ethanolic solutions of indium trichloride and stannic chloride at different substrate temperatures. The pyrolytic decomposition temperature affects the properties and morphology of ITO samples. X-ray diffraction results showed that the films are polycrystalline with cubic structure and exhibit preferential orientation along (222) plane. The SEM and AFM studies indicated that the surface morphology of the samples increases with substrate temperature. The typical I₅₀₀ sample is composed of cubic grains and has carrier concentration of 3.26 × 10²⁰ cm^?3 and mobility of 9.77 cm²/V s. The electrical resistivity of ITO films decreased with increasing deposition temperature. The highest figure of merit of film is 4.4 × 10^?3 Ω^?1. Optical absorption studies reveal that films are highly transparent in the visible region and band gap increases with substrate temperature owing to Moss-Burstein effect.     

Diffusion of Calcium Ion in Liquid Slag

A simple radioactive tracer technique is used to measure the diffusion coefficient of calcium ion in molten slags. In a slag of 40 pet CaO-40 pet SiO₂-20 pet AL₂O₃, D_Ca⁺⁺ at 1450°C is 1.3×10^?6 cm² sec^?1.     

Photorefractive and nonlinear optical properties of indium(III) tetra(15-crown-5)phthalocyaninate-based composites

Photoelectric, nonlinear optical, and photorefractive properties of hybrid composite materials based on polyvinylcarbazole (PVK) and indium(III) 2,3,9,10,16,17,23,24-tetra(15-crown-5)phthalocyaninate [(15C5)₄Pc]In(OH) are studied in detail. Field dependence of the quantum efficiency in a 7.8 μm-thick layer containing 5 at % [(15C5)₄Pc]In(OH) is measured. The best approximation of the quantum efficiency with Onsager’s equation corresponds to a quantum yield of thermalized electron-hole pairs φ₀ = 0.01 at initial separation r ₀ = 9.8 Å. Z-scan measurements in a nanosecond range showed that the electric susceptibility of [(15C5)₄Pc]In(OH) solution in tetrachloroethane (TCE) with a concentration of 7 × 10^?4 mol/L is χ⁽³⁾ = 1.34 × 10^?9 esu. The maximum coupling gain coefficient found for the material composed of PVK and 5 wt % [(15C5)₄Pc]In(OH) at an electric-field intensity of 200 V/μm is Γ = 80 cm^?1, and the difference between the coupling gain and absorption coefficients is Γ ? α = 70 cm^?1. The dependence of the coupling gain coefficient on the intensity ratio of interfering beams 1 and 2 (β = I ₁(0)/I ₂(0)) in a composite containing 3 wt % [(15C5)₄Pc]In(OH) is measured. An increase in β was attained by decreasing intensity of the signal beam I ₂(0) at constant intensity of the pump beam I ₁(0) = 0.15 W/cm² and E ₀ = 214 V/μm. Within the initial segment of the curve, the coupling gain coefficient increases from 30 to 60 cm^?1; then, the coefficient drops almost to the initial value. The data obtained show that the composite materials studied can be used in practice for correcting faded images. The combined analysis of the results obtained and similar data for gallium and ruthenium tetra-15-crown-5-phthalocyaninate complexes revealed the regularities in the change of the quantum yield of thermalized electron-hole pairs and the photorefractive coupling gain coefficient in a series of complexing metals: gallium(III), ruthenium(II), and indium(III). An increase in the molecular weight of the central metal atom is found to result in a substantial decrease in Γ and φ₀ due to the increase in the spin-orbit coupling constant.     

Diffusion von Wasserstoff durch Titan

Diffusion of hydrogen through titanium The diffusion coefficient of hydrogen in titanium determined by an electrochemical method is D_{24 °} ～ 7 × 10^?12 cm² /s at a cathodic polarisation of 10 mA/cm² . The variation of the diffusion coefficient with temperature enables the activation energy to be calculated (6,9 kcal/Mole). The diffusion takes place with intermediary titanium hydride formation. The diffusion is measured using an electrochemical method with a metallic membrane where the hydrogen generated at the one side is ionized, after diffusion at the other side. It is then possible to establish a relation between the ionization current and the diffused quantity, also as a function of time.     

Diffusional stability of ferritic–martensitic steel composite for service in advanced lead–bismuth cooled nuclear reactors

Abstract

To combat liquid metal corrosion from lead–bismuth eutectic coolant in the fuel cladding and coolant piping of generation IV fast fission reactors, a composite that employs a Fe–Cr–Si steel layer weld clad on a structural layer of alloy T91 (Fe–9Cr–1Mo) is being developed. Diffusion of Si away from the cladding during service can compromise corrosion resistance, whereas carbon redistribution will affect mechanical properties and phase stability. Diffusion of silicon and carbon in a manufactured sample of the composite has been investigated both experimentally and by modelling. The diffusion coefficient for silicon in the T91/Fe–12Cr–2Si system was found to be 1·36 × 10^?12 cm² s^?1 at 650°C, implying that concentration in the clad layer should not drop below 1·25%Si at a distance of 51 μm from the interface after 50 years' service at 650°C. The rapid carbon diffusion observed should be helpful during processing and operation. The two layers will have similar properties once carbon diffuses into the cladding, reducing the probability of mechanical property mismatch based errors during processing. The increased hardness of the carbon enriched clad layer will result in higher strength during operation, reducing the likelihood of damage or abrasion.     

Covalent linking of ethylene amine functionalized single-walled carbon nanotubes to cobalt (II) tetracarboxyl-phthalocyanines for use in electrocatalysis

In this paper, we report on the use of ethylene amine (EA) side-wall functionalized single-walled carbon nanotubes (SWCNT) in the synthesis of covalently linked cobalt (II) tetracarboxyl-phthalocyanine complex (CoTCPc–EA–SWCNT(linked)), the characterization of the linked complex and the application of this complex in the electrocatalytic oxidation of amitrole. UV–vis, FTIR, TEM, Raman and XRD spectroscopies were used in characterization of CoTCPc–EA–SWCNT complex, while cyclic voltammetry, rotating disc electrode (RDE) voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used during the characterization of amitrole on the modified glassy carbon electrode. Thermogravimetric analysis (TGA) was used to confirm the extend of functionalisation of of SWCNTs. The catalytic rate constant was 1.2 × 10³ M^?1 s^?1 and the apparent electron rate transfer constant was 3.0 × 10^?5 cm s^?1. The linear dynamic range was 1.0 × 10^?5–1.6 × 10^?4 M, with a sensitivity of ～0.76 A mol^?1L cm^?2 and a limit of detection of 0.1 μM using the 3δ notation.     

Electrodeposition of Li and electrochemical formation of Mg–Li alloys from the eutectic LiCl–KCl

The electrochemical behavior of Li⁺ was studied at the inert and active electrodes in the molten LiCl–KCl eutectic. Transient electrochemical techniques, such as cyclic voltammetry, chronoamperometry and chronopotentiometry were used in order to explore the deposition mechanism of Li. The reduction process of Li⁺ is irreversible and the diffusion coefficient of Li⁺ at 723 K was determined as 6.68(±0.07) × 10⁻⁶ cm² s⁻¹. During the electrodeposition process of Li, the electrocrystallization played an important role. The chronoamperometric studies indicated that instantaneous nucleation existed during the electrodeposition process of Li metal. At a Mg electrode, the electroreduction of Li⁺ takes place at a less cathodic potential values than that at Mo electrode which indicated the formation of Mg–Li alloy. The Mg–Li alloy films with different crystal phase were obtained by potentiostatic electrolysis, and the samples were characterized by X-ray diffraction and scanning electron microscopy.