Diffusion Coefficient Of Cu Research Articles

Modelling wide gap TLP bonding of Ti–48 at.-%Al–2 at.-%Cr–2 at.-%Nb alloys

Modelling of the wide gap transient liquid phase (TLP) bonding of a Ti–48 at.-%Al–2 at.-%Cr–2 at.-%Nb (48–2–2) alloy with 48–2–2+Cu composite interlayers is examined. The role of the 48–2–2 powder particles in the composite interlayers during the isothermal solidification process was studied. This work was based on a high apparent diffusion coefficient of Cu in the multiphase γTiAl/α2 Ti3Al 48–2–2 alloy, combined with a low Cu solubility in 48–2–2. The redistribution, during bonding and post-bond heat treatment, of the Cu placed into the original composite interlayer is discussed. The model is used to account for the observed behaviour of 48–2– 2+Cu composite interlayer bonds.

Impurity diffusion through Nafion and ceramic separators used for electrolytic purification of spent chromium plating solutions

In this study, diffusion coefficients of cations (Cu(II), Ni(II), and Fe(III)) through a Nafion membrane were measured with a two-compartment cell and using a technique that monitored pH change during ion exchange. In the cell experiments the single ion diffusion coefficients of Cu(II), Ni(II), and Fe(III) were 1.04×10 −6, 8.36×10 −7, and 4.24×10 −7 cm 2/s, respectively. In the pH monitoring experiments they were similar (1.26×10 −6 and 6.23×10 −7 cm 2/s for Cu(II) and Ni(II), respectively). As expected, the trivalent cations diffused slower than the divalent cations through the membrane. Diffusion coefficients increased with decreasing pH especially when pH was below 1. The Arrhenius equation well characterized the variations in the diffusion coefficients through the Nafion membrane measured at different temperatures. In the presence of other ions the measured diffusion coefficients increased slightly. In the ceramic membrane diffusion coefficients were larger than in the Nafion membrane (3.64×10 −6, 3.04×10 −6, and 1.68×10 −6 cm 2/s for Cu(II), Ni(II), and Fe(III), respectively). The approximate tortuosity factors of the Nafion membrane and ceramic membrane were 5 and 1.6 for Cu(II), respectively. The species concentration variation in the system was accurately predicted using a model based on Fick’s second law.

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

SummaryThe 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.

Diffusion Analysis across Grain Boundary in Al-3.7 mass%Cu Alloy Using Analytical Electron Microscopy

An Al–3.7 mass%Cu alloy was subjected to aging treatment at selected temperatures in the range from 453 to 548 K. Diffusion coefficients of Cu in the alloy were then determined from Cu concentration profiles measured across the grain boundary. A high spatial resolution analytical electron microscope (AEM) capable of forming a 1 nm probe was used to measure the concentration profiles. As the aging temperature is lower, the diffusion coefficients tend to deviate from the values extrapolated from the higher annealing temperatures. It is suggested that this deviation is due to the presence of quenched-in excess vacancies. The concentration profiles were also measured for the boundaries having different misorientation angles. It is shown that the concentration profiles are essentially the same regardless of the misorientation angles and of the boundary characters except for the misorientation angles smaller than a few degrees.

Measurements of Cu Atoms Diffusion Coefficients in He and Ne - Optimalisation of a Novel Method

A novel method based on two-pulse excitation of a hollow cathode discharge to determine metal atoms diffusion coefficients in noble gases was tested in Cu-He and Cu-Ne systems. The excitation conditions such as time duration of the discharge current pulses and configurations of the hollow cathode discharge were checked. Measurements carried out over the wide range gas pressures allowed obtaining the Cu atoms time-decay curves from which the diffusion coefficients were calculated. The values for Cu atom diffusion coefficients of 570 and 310 cm 2 s - 1 mbar in He and Ne, respectively were in a good agreement with earlier reported data achieved by using the absorption spectroscopy method. The diffusion coefficient of Cu in 3 He, the lighter isotope of helium, was also found to be 670 cm 2 s - 1 mbar that agreed well with the kinetic theory of gases. To authors believe this value was not reported previously.

Diffusion coefficients of Cu(II) complexes with ligands used in alkaline electroless copper plating solutions

The diffusion coefficient values of the Cu(II) complex compounds with EDTA, DTPA, NTA, Quadrol, glycerol, saccharose, (+)- and (±)-tartaric acid, OH− ions obtained by polarographic measurements in alkaline solutions lie in the range (1.2–5.7) × 10−6 cm2 s−1 (at 20 ∘C and J = 3) depending on the size of complex species, and are less than those of free (hydrated) Cu(II) ions and methanediol anion (H2C(OH)O−) determined under the same conditions which are 7.0 × 10−6 and 10 × 10−6 cm2 s−1, respectively. The linear dependence of the polarographically determined diffusion coefficient values on the inverse radius of Cu(II) complex species is observed.

イオンビームスパッタリング法により形成したＡｇ‐Ｃｕ合金薄膜を用いたＴｉの接合

A novel bonding process, which is a kind of diffusion bonding with cleaning the bonding surface followed by deposition of Ag-28mass% Cu alloy thin layer using ion beam sputtering, was applied to joining of commercial pure titanium (CPTi) under atmospheric pressure. The deposition of the Ag-Cu layer after removing the oxide film of the bonding surface successfully improve bondability of CPTi. The joint strengths depend on the thickness of the Ag-Cu deposited layer. A maximum joint strength close to the base metal strength is obtained using the optimum thickness of Ag-Cu deposited layer, 0.3μm, under the conditions of a bonding temperature of 1153K and bonding time of 300s or more. The thicker Ag-Cu deposited layer of 1.0μm in thickness results in a hardened microstructure including Ti2 (Cu, Ag) intermetallic precipitates and thereby lower strength and lower ductility after bonding at 1153K for 1800s. The joint with the thinner Ag-Cu deposited layer of 0.1μm in thickness is not bonded at all.The Ag-Cu deposited layers having 0.3μm or more in thickness become enriched in Ag during heating in the bonding process because of a greater diffusion coefficient of Cu than that of Ag in titanium. As a result a almost pure Ag layer is formed on the bonding surface after heating above 973K. The bonding is, therefore, considered to proceed via solid state diffusion bonding between the surface layers enriched in Ag and be completed after homogenization of the solute elements of Ag and Cu.

Infinite-Dilution Diffusion Coefficients of Complex Ions from Solution Conductivity Data

A technique is presented for determining infinite-dilution diffusion coefficients of complex ions from solution conductivity data. The method involves measuring the conductivities of dilute solutions in which the distribution of complex ions is systematically varied and statistically regressing the data to an equation that effectively relates individual ion diffusion coefficients to solution conductivity. The procedure is simple and requires no specialized equipment to perform. Unlike methods that require a concentration gradient, the solution composition is homogeneous and at equilibrium during measurements, which is a significant advantage when labile complexes are being studied. In this paper, diffusion coefficients of cuprous cyanide complexes are determined. Statistical analysis yields the infinite-dilution diffusion coefficients of Cu(CN)(2)(-), Cu(CN)(3)(2-), and Cu(CN)(4)(3-) at 25 °C as 1.43 × 10(-5) ± 9%, 1.08 × 10(-5) ± 9%, and 6.21 × 10(-6) ± 22% cm(2)/s, respectively.

Ion exchange on resins with temperature-responsive selectivity: II. Thermo-induced concentration waves in ion-exchange column

The kinetics of H +–Cu 2+, H +–Zn 2+, Zn 2+–Cu 2+, and Cu 2+–Zn 2+ exchanges on iminodiacetic resin Lewatit TP-207 at 293 K has been studied. The effective diffusion coefficients of Cu 2+ and Zn 2+ have been determined to be 2.6×10 −8 and 1.4×10 −7 cm 2/s, respectively, for the given conditions. The kinetics of Cu 2+ and Zn 2+ thermostripping from the resin preequilibrated with a mixture of zinc and copper sulfates at pH 1.8 have been shown to be influenced by the different metal ion diffusivities and by the presence of a third component (H +) in the system so that an oscillation of ion concentration is observed. This phenomenon is observed more clearly with the increase of resin beds when studying the dynamics of the column thermostripping process. Formation of a concentration wave results in the enrichment of the first halfwave with Zn 2+ while the second halfwave appears to be enriched with Cu 2+. A mathematical model of ion-exchange dynamics of components with dissimilar diffusivities has been developed. The phenomenon of formation of concentration waves is interpreted within the model as a result of the influence of a local electrical field, arising in the resin phase, from the difference on fluxes of exchanging ions. The results of computer simulation of the thermostripping process within the frame of the model proposed are in a good agreement with those obtained in thermostripping experiments.

Effect of copper diffusion on photovoltaic characteristics of CuGaSe 2–GaAs cells

CuGaSe 2–GaAs heterojunctions were fabricated by fast evaporation of polycrystalline CuGaSe 2 from a single source on n-type GaAs substrates. The best CuGaSe 2–GaAs photocell (without an antireflective coating) exhibited an efficiency of 11.5%, J sc=32 mA/cm 2, V oc=610 mV and FF=0.60. The spectral distribution of photosensitivity of CuGaSe 2–GaAs junctions extends from 400 to 900 nm. The CuGaSe 2 films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. XRD analysis indicated that the thin films were strongly oriented along the (1 1 2) plane. SEM studies of CuGaSe 2 films showed nearly stoichiometric composition with grain size about 1–2 μm. The energy dispersive X-ray spectroscopy (EDX) analysis of Cu concentration distribution in n-type GaAs showed that Cu diffused from the film into n-type GaAs during the growth process resulting in formation of the latent p–n homojunction in substrate. The diffusion coefficient of Cu in GaAs at growth temperature (520°C) estimated from EDX measurements was 6×10 −8 cm 2/s.

Mechanism and kinetics of the electrochemical reduction of Cu(II) at gold in pyridine and water-pyridine mixtures

The cathodic reduction of Cu(II) ions at a gold electrode has been studied in waterpyridine mixtures containing NaClO4 as background electrolyte by means of rotating disc (RDE) and ring-disc electrode voltammetry (RRDE), coulometry, and potentiometry. The voltammetric curves obtained at the RDE split into two waves of nearly the same height which correspond to two successive reactions: Cu(II) + e− → Cu(I) and Cu(I) + e− → Cu. The diffusion coefficients of Cu(II) as well as the formal potentials and kinetic parameters of the Cu(II)/Cu(I) electrode reaction were evaluated and are discussed. In addition, some experiments with an electrochemical quartz crystal microbalance (EQCM) were performed in order to explain the pyridine adsorption on polycrystalline gold.

Effects of Al on the glass-forming ability of Zr-Cu based alloys

Effects of Al on the glass-forming ability (GFA) of Zr-Cu alloys were investigated by studying the solidification characteristics of the Zr 65Cu 27.5Al 7.5 alloy in comparison with those of the Zr 65Cu 35 alloy. It is presumed that the much higher GFA of the Zr 65Cu 27.5Al 7.5 alloy than that of the Zr 65Cu 35 alloy is due to the much lower diffusion coefficient of Cu and Al in the Zr 63Cu 27.5Al 7.5 melt, the low nucleation rate of the Zr 2(Cu, Al) nucleating phase due to its small nucleation driven force and long nucleation reduction time resulting from the addition of Al. The higher GFA of the Zr 65Cu 27.5Al 7.5 alloy does not result from the crystal growth difficulty caused by the long-range redistribution of Al at the solid-liquid interface. In fact, Al does not have long-range redistribution at the solid-liquid interface but is trapped by the growing solid to form Zr 2(Cu,Al) and Zr(Cu,Al) phases under rapid quenching conditions.

Characterization of Cu–Na ion-exchanged glass waveguides

Copper–sodium ion-exchanged glass waveguides are fabricated and characterized. Optical absorption and m-lines spectroscopy analyses are presented. No stress-induced birefringence is observed from refractive index profiles reconstruction, and the Cu+ oxidation state is shown to mostly determine the refractive index change. Comparison between compositional in-depth profiles and index profiles is allowed to obtain the variation in the electronic polarizability due to the Cu+–Na+ exchange. The diffusion coefficient of Cu+ in soda-lime glass is also calculated.

Current versus Potential Studies for Copper Electrodeposition at a Rotating Disc Electrode

A series of experiments has been carried out using a rotating disc electrode for use in an undergraduate experiment. A range of CuSO 4 solutions (0.5 to 10 mmol dm -3 ) in 0.5 mol dm -3 Na 2 SO 4 was studied at pH 2.0 and 298 K. Conditions for steady state were determined and limiting currents were measured. In accordance with the Levich equation it is shown that plots of limiting current versus concentration of copper and limiting current versus the square root of rotation rate are linear for concentrations betweeen 0.5 and 10.0 mmol dm -3 CuSO 4 . A value of 5.0 x 10 -6 cm 2 s -1 was measured for the diffusion coefficient of Cu 2+ in the mmol dm -3 solution.

Thermoconvection‐Enhanced Deposition of Copper

Thermal gradients and thermoconvective flow in the vicinity of the electrode are shown to enhance mass transport of the electroactive species during reduction of copper. The transport‐limited current of the copper reduction reaction is more than doubled under conditions of positive and negative thermal gradient in comparison with isothermal conditions. Furthermore, thermal gradients affect strongly the potential dependence of the current. Kinetic and thermodynamic parameters for electrodeposition of copper were determined from polarization curves analyzed with Butler‐Volmer, Tafel, and Levich expressions. Under isothermal conditions the exchange current density for the copper reduction reaction was found to be given by ( in mA cm−2 and in K) under conditions of in . The diffusion coefficient of Cu(II) at 298 K under the same conditions was found to be 5.36 · 10−6 cm2 s−1. Decrease of the effective thickness of the diffusion layer due to thermoconvection in the vicinity of the cathode is responsible for the effect of the gradient on transport‐limited current.

The Off‐Center Effect on the Diffusion Coefficient of Cu+ and Li+ in the KCl Lattice

AbstractIt is well‐known that the diffusion coefficients of the Cu+ cation in the NaCl and KCl lattices exceed by three or four orders of magnitude the corresponding self‐diffusion coefficients in the intrinsic temperature regions. This fast diffusion of the Cu+ has been explained in many papers as an interstitial diffusion although the optical spectra do not confirm the existence of interstitial Cu+. In this paper a new mechanism for fast diffusion is proposed. The model assumes that the equilibrium positions of the cationic impurities are noncentral and that the diffusion proceeds by hopping across the potential barrier along the nonlinear paths with the highest probability. The main result shows that the off‐center position considerably enhances the diffusion. Theoretical diffusion coefficients are obtained by modelling the potential barrier. Changes of the configuration entropy and the vibration spectra due to the presence of the noncentral impurity are included in the model. The numerical results of the diffusion coefficient computed in this way are in agreement with the experimental data and it is shown that if the impurity is placed close to the central site the due diffusion coefficient is close to that for the cationic self‐diffusion. The Li+ cation case is dealt with as the case of the Cu+ cation.

Selective permeation of metal ions through cation exchange membrane carrying N-(8-quinolyl)-sulfonamide as a chelating ligand

A cation exchange membrane carrying N-(8-quinolyl)-sulfonamide was prepared by attaching the chelating reagent to side chains of a polymer. The chelating reagent was known to have selectivity for Cu 2+ over Fe 3+. Acrylic acid was also introduced to add a hydrophilic property. All compounds were identified by mp, elemental analyses, IR, 1H NMR, 13C NMR and GC-MS. The ratio of the chelation monomer to the acrylic acid was varied between 1:7 and 1:1. The molecular weight of the prepared polymer, determined by gel permeation chromatography, was between 5×10 5 and 10 7. The above polymer diluted with Me 2SO was impregnated into a porous Teflon membrane and then the solvent was evaporated. The membrane had enough hydrophilicity even after the above operation. The membrane was sandwiched between 2 glass cells filled with a Cu 2+ and Fe 3+ mixture solution at a pH of 2.0 (extraction side) and with 1 N sulfuric acid (stripping side), respectively. The apparent diffusion coefficient of Cu 2+ through the present membrane was almost comparable or a little smaller than that of the commerical one, while that of Fe 3+ was suppressed remarkably. Thus, the selectivity of Cu 2+ over Fe 3+ became 2.6, i.e., ca. double that of the commercial membrane.

Diffusion of copper and silver in zirconium

B.c.c. zirconium (/3-Zr) is one of the well-known anomalous b.c.c, metals, which show a significant upward curvature in the Arrhenius plot of the self-diffusion coefficients [1]. H.c.p. zirconium (cr-Zr) also shows peculiar self-diffusion behaviour, i.e. downward curvature in the Arrhenius plot [2]. Furthermore, it is well known that impurity atoms with small size such as Fe and Co are fast diffusers in both fl-Zr [3] and cr-Zr [3]. However, according to a recent compilation of a vast amount of experimental data on diffusion in solid metals and alloys [4], a large scatter in the diffusion parameters (the preexponential factor Do and the activation energy Q) for impurity diffusion of some elements in/3-Zr and ol-Zr is reported. For example, the values of the activation energy for the diffusion of Ag in o~-Zr by various researchers lie in a wide range between 174 and 245 kJ mol -I, all of which have been obtained by the radiotracer method. Thus, use of another experimental method may be helpful to elucidate the diffusion behaviour. On the other hand, no data on the diffusion of Cu in/3-Zr have been compiled [4]. The atomic radius of Ag (0.1406 nm) is larger than that of Cu (0.1244 nm) but smaller than that of Zr (0.1558 nm) in the b.c.c, structure [5]. Thus, diffusion experiments of Cu and Ag in Zr are effective for confirming the size effect for the impurity diffusion. In the work reported here, interdiffusion experiments with couples of pure Zr and dilute binary alloys containing Cu and Ag were carried out. The impurity diffusion coefficients of Cu and Ag in Zr were determined by applying Darken's relation [6], i.e. the extrapolated value of the interdiffusion coefficient to the infinite dilution of the solute can be regarded as the impurity diffusion coefficient of the solute in Zr. This method avoids problems such as chemical reaction on the surface of reactive Zr specimen that occur with the radiotracer diffusion experiments. A pure Zr rod 7 mm in diameter was made by Ar arc melting of Zr sponge of 99.6% purity supplied by Nippon Mining Co. Ltd. The main impurities in this material were (ppm): 852 O, 393 Fe, 38 Mg, 100 Cr, <60 Si and <50 Hr. The grain size in the rod was 1-2 mm. The Zr rod was cut to make disc specimens 5mm in thickness. Rods of Zr-1.57 at% Cu, Zr-0.34 at % Ag and Zr l .27 at % Ag alloys were made by Ar arc melting of the pure Zr sponge with Cu oxygen-free chips of 99.99% purity and Ag

Diffusivity of Cu2+ in calcium alginate gel beads

A linear absorption model (LAM) is used to describe the process of metal binding to spherically shaped biopolymers particles. The LAM was solved using a numerical algorithm which calculates diffusivities of metal ion in biopolymer gels. It assumes attainment of rapid metal-biopolymer binding equilibrium accompanied by rate limiting diffusion of the metal ions through the gel. The model was tested using batch experiments in which copper (Cu(2+)) binding with calcium alginate beads was investigated. Biopolymer density in the beads was varied between 2% and 5%. The diffusion coefficient of Cu(2+) calculated from the LAM ranged from 1.19 x 10(-9) to 1.48 x 10(-9) m(2) s(-1) (average 1.31 +/- 0.21 x 10(-9) m(2) s(-1)), independent of biopolymer density. The LAM has theoretical advantages over the shrinking core model (shell progressive model). The latter calculated an unreasonable exponential increase in the diffusion coefficient as density of alginate polymer in the bead increased.

Secondary ion mass spectroscopic characterization of silver and aluminum diffusion in parylene

Aluminum and silver on parylene-n (PA-n) were explored as metallization options. The low resistivity of silver (1.6 μΩ cm) makes it suitable for interconnection applications. Al is a well studied and utilized metal. Al and Ag diffusion have been compared to that of Cu. The Al, Ag, and Cu were deposited by partially ionized beam (PIB) technique. PA-n, a low dielectric constant polymer, was vapor deposited. Diffusion of the metals was studied at anneal temperatures/time of 573–623 K/0.5 Hr using secondary ion mass spectrometry and Rutherford backscattering techniques. The metal diffusion in the PA-n was found to be very small. The Cu diffusion profiles were of low concentration but fairly deep. It was observed that the Ag diffused less than the Al, both in atomic concentration and diffusion depth. For these annealing temperatures and time, it was estimated that the diffusion coefficients for Al was about 0.4 × 10−13 cm2/s; for Ag was about 0.8 × 10−14 cm2/s at 573 K; and for Cu was about 0.6 × 10−13 cm2/s at 623 K. The diffusion coefficient of Cu in PA-n was found to be comparable to the diffusion coefficient in polyimides. A substantial reduction of diffusion due to higher ion acceleration (1–3 kV) during PIB metal deposition was observed. It was found that there was significant diffusion when Ag/Pa-n was annealed at 648 K.