Diffusion Coefficient Of Cu Research Articles

A Cu/Ni/Cu/Sn1.8Ag microbump structure for void-free interface under long time high-temperature storage

Microbumps play a crucial role in interlayer interconnections for advanced packaging. Among the prevalent microbump structures are Cu/Sn and Cu/Ni/Sn configurations. However, as the bump size continues to shrink, excessive Kirkendall voids tend to form in Cu/Sn microbumps, leading to potential reliability issues. While Cu/Ni/Sn structures can suppress Kirkendall void formation, Ni3Sn4 intermetallic compound (IMC) exhibits inferior physical properties compared to Cu3Sn and Cu6Sn5. In this study, a novel Cu/Ni/Cu/Sn1.8Ag (CNCT) Sn-rich microbump structure with controlled Cu thickness is proposed to suppress Kirkendall void formation while promoting Cu6Sn5 and Cu3Sn as interfacial IMCs. A Ni barrier layer is inserted to partition the Cu pillar and impede Cu atom replenishment from the bottom side. The remaining Cu pillar at the top is designed to be 3μm thick, which is intended to be fully consumed by 8μm Sn1.8Ag solder while simultaneously serving as redundant protection for the bottom Cu pillar against unexpected Sn spillage. The effects of high temperature storage (HTS) at 150°C on IMC evolution in CNCT microbump bonding were investigated for 1500 hours. No significant voids were observed at the bonding interface during HTS. Interfacial positions recorded from 0 to 500 hours show that the Cu3Sn IMC grows unidirectionally toward the Cu side but not toward the Sn side, indicating a greater diffusion flux of Sn atoms compared to Cu atoms. The diffusion coefficients of Cu in Cu3Sn (DCu,ε), Cu6Sn5 (DCu,η), and Sn in Cu3Sn (DSn,ε), Cu6Sn5 (DSn,η) at 150°C were calculated as 1.36×10−18 m2/s, 5.01×10−19 m2/s, 9.53×10−19 m2/s and 1.10×10−18 m2/s, respectively. The dramatic decrease of DCu,η suggests that the diffusion capacity of Cu atoms into Sn is significantly suppressed. The notable transformation of Cu3Sn to Cu6Sn5 occurred after 500 hours. By 1500 hours, Cu3Sn was greatly consumed, and the bonding interface tended to form a stable Cu/Ni/Cu6Sn5/Ni/Cu structure. Diffusion models were established and discussed to elucidate the mechanisms governing both stages.

Vacuum diffusion bonding of TC4 titanium alloy to T2 copper with VCrNi1.8 eutectic medium entropy alloy interlayer

A new eutectic medium entropy alloy VCrNi1.8 was designed for vacuum diffusion bonding TC4 titanium alloy (TC4) with T2 copper (T2). The influence of welding parameters on the microstructure and shear strength of joints was investigated. β-Ti/Ti3Ni/Ti3AlNi/Ti2Ni/TiNi/TiNi(V, Cr)2/BCC + FCC/Ni(V, Cr)2/Cu phases existed in sequence in the TC4/VCrNi1.8/T2 joint. The crystallographic orientations of Ti3AlNi, Ti2Ni, TiNi and TiNi(V, Cr)2 phases were (200), (020), (011) and (012), respectively. The zone axis of Ti3AlNi, Ti2Ni, TiNi and TiNi(V, Cr)2 phases was correspondingly [002¯], [202], [100] and [4¯00]. The maximum shear strength of joint made at 880 °C for 90 min reached 214 MPa. The growth activation energy of diffusion zones I and II on TC4/VCrNi1.8 side was 230 kJ/mol and 246 kJ/mol, respectively. The interplanar spacing of (200), (020), (011) and (012) was d(200) = 0.656 nm, d(020) = 0.375 nm, d(011) = 0.556 nm and d(012) = 0.225 nm, respectively. The crystal face mismatch of Ti3AlNi/Ti2Ni, Ti2Ni/TiNi and TiNi/TiNi(V, Cr)2 interface was calculated to be 54.5%, 58.3% and 84.8%, respectively, revealing non-coherent with high strain energy. When the bonding temperature increased and holding time prolonged, the joint fractured along the TC4/VCrNi1.8 interface. The fracture morphology of joint presented cleavage fracture characteristics. The average diffusion coefficient of Cu in VCrNi1.8 interlayer at 840 °C, 860 °C, 880 °C, and 900 °C was 0.9 × 10−15 m2/s, 1.2 × 10−15 m2/s,1.6 × 10−15 m2/s, and 2.5 × 10−15 m2/s, respectively.

Formation mechanism of copper-gilded coronet ornaments excavated from a Sui or early Tang tomb situated in Xi’an, Shaanxi

The formation of the gold layer in mercury gilding occurs through the heating a gold amalgam. As a result, the formation mechanism and technical characteristics of gilded products are closely related to the temperature at which they are heated. In this study, XRD and XPS analysis of a copper-gilded coronet from the Sui or Tang dynasties revealed that Au3Cu was one of the main phases of the gold layer. Therefore, base on the thermodynamic stability of ordered phases like Au3Cu, the estimated heating temperature for this copper-gilded coronet ranged from 240 to 285 ℃. Furthermore, SEM–EDS analysis of the cross-sectional concentration distribution of Cu indicated that the diffusion distance of Cu during heating did not exceed 2 μm. At 240–285 ℃, Cu diffused along the defects of the gold layer, and the diffusion process followed Fick’s second law. Previous research has indicated that the defect path diffusion coefficient of Cu is on the order of 10–12 cm2/s, and the heating time of the gilding process is typically considered to be 15 min. Using the diffusion equation, the calculated diffusion distance of Cu aligned with the diffusion behavior of Cu at 240–285 ℃, confirming the inferred heating temperature range. Additionally, at these temperatures, the gold layer was formed through the solid-state reaction of the gold amalgam and was bonded to the substrate through the diffusion of Cu.

Experimental and DFT study of Cu(II) removed by Na-montmorillonite.

The experimental and theoretical studies on the adsorption of Cu(II) on the surface of Na-montmorillonite (Na-Mt) were reported. Effects of batch adsorption experimental parameters were studied. Density functional theory and molecular dynamics simulations were used to study the adsorption of Cu(II) on montmorillonite (001) surface. The adsorption reached equilibrium within 80 min and the adsorption capacity was 35.23 mg·g-1 at 25 °C. The adsorption data of Cu(II) were consistent with pseudo-second-order kinetics and Langmuir isotherm models. The adsorption process was dominated by physical adsorption (Ea was 37.08 kJ·mol-1) with spontaneous endothermic behavior. The influence of coexisting cations on the adsorption capacity of Cu(II) was Mg(II) > Co(II) > Ca(II) > Na(I). The simulation results demonstrated that there were no significant differences in the adsorption energy of Cu(II) at the four adsorption sites on the montmorillonite (001) surface. Cu(II) had more electron transfer than Na(I). The diffusion coefficient of Cu(II) in the aqueous solution system containing montmorillonite was 0.85×10-10 m2·s-1. Considerable amounts of Cu(II) ions were adsorbed at a distance of 0.26 and 2.25 Å from the montmorillonite (001) surface. The simulation results provided strong supporting evidence for experimental conclusions.

Influence of high-current pulsed electron beam irradiation on elemental diffusion and mechanical properties of copper/316L stainless-steel bonded joints

In this paper, Cu and 316L stainless steel with abundant crystal defects are constructed on bonding surfaces using high-current pulsed electron beam (HCPEB), and direct bonding is carried out in vacuum. The bonding temperature was varied as 800 °C and 850 °C, while the bonding pressure of 5 MPa and the bonding time of 40 min was maintained. Microstructure observations revealed that the initial coarse grains of the 316L was significantly changed to fine grains with abundant crystal defects after HCPEB irradiation. After diffusion bonding, the bonded area of the initial joint is not completely joined. Comparatively, the joints pretreated by HCPEB displayed a well-bonded interface. The diffusion coefficient of Cu at interface is significantly increased as well, which is attributed to the acceleration of atomic diffusion. Bonding strength indicates that the shear strength of the joints prepared via HCPEB pretreatment is much higher than the initial joints.

Concurrent (Fe,Mo)2C carbides and Cu-rich clusters precipitation in ferritic steel containing copper during aging

ABSTRACT The concurrent (Fe,Mo)2C carbides and Cu-rich clusters precipitation in the ferritic steel containing copper after aging at 400°C for 4000 h have been investigated using transmission electron microscopy (TEM) and atom probe tomography (APT). The results show that spinodal decomposition and an atomic ordering reaction occur in the ferritic steel containing copper. After aging, the retained austenite decomposed by the spinodal mechanism into C-rich and C-lean regions. The C-rich phase transforms into the (Fe,Mo)2C carbides via the ordering reaction, while Cu-rich clusters formed in the C-lean regions. The experimental results can be interpreted on the basis of phase separation via spinodal decomposition followed by chemical ordering. The small size of Cu-rich clusters can be attributed to the lower diffusion coefficient of Cu in the retained austenite.

Investigation of interdiffusion behavior in the Ti–Zr–Cu ternary system

Abstract The interdiffusion behavior of diffusion couples Ti-25Zr/Cu, Ti-50Zr/Cu and Ti-75Zr/Cu (at.%) at 973–1073 K was investigated by using electron probe microanalysis. The results show that the diffusion paths in all diffusion couples deviate away from the faster-diffusing Cu–Ti side. The diffusion paths pass the tie-line, across or parallel to, corresponding to the different diffusion layer structures and phase morphologies. The average effective interdiffusion coefficients and activation energies of Cu in both solid solutions and intermetallic compounds were determined. The diffusion coefficients of Cu in β(Ti, Zr) solid solution increase slightly and then decrease with the increase in Zr content, while the diffusion coefficients of Cu in Cu(Ti,Zr)2 intermetallic compound decrease with the increase in Zr content. The diffusion coefficients of Cu in Cu51Zr14 are the largest among all the intermetallic compounds in diffusion couples.

The microstructures and mechanical properties of a highly alloyed Al-Zn-Mg-Cu alloy: The role of Cu concentration

The influence of Cu content on microstructures and mechanical properties of a highly alloyed Al-10.0Zn-2.6Mg-xCu-0.15Zr alloy with the Cu content in the range of 0 to 3.0 was studied by OM, SEM, TEM, tensile tests, XRD, and DSC. We determined that the Mg(Zn,Al,Cu)2 (σ) and Al2Mg3Zn3 (T) phases presented in all as-cast alloys, and Al2Cu (θ) phase was found in the alloys with Cu higher than 2.5 wt.%. Also, it is found that the volume fraction of the primary phase increased with the Cu increase. Further, the volume fraction of the residual eutectic phase (REP) increased gradually with the increase of Cu after solid solution, mainly attributed to the low diffusion coefficient of Cu and thus suppressed the dissolution of the second phase. The tensile testing of the aged alloys indicates that the strength of the studied alloys increased significantly with the Cu increase when Cu is lower than 1.0 wt.%, whereas further increase Cu content it decreases. The elongation increases to a peak value fast at low Cu content. After a critical Cu content (1.5 wt.%), a slight decrease is followed. The elongation of highly alloyed Al-Zn-Mg-Cu alloys should consider the coupling effect of grain refinement and REP.

Research on the Diffusion Behavior of Cu in Low-Carbon Steel under High Temperatures

The effective diffusion of Cu in Fe is the key to forming a stable transition layer between copper and low-carbon steel, but it is seriously affected by several factors, especially temperature, and the diffusion of Cu can only be completed at high temperatures. In order to analyze the diffusion coefficient of Cu in low-carbon steel under high temperatures, and to obtain the best diffusion temperature range of Cu in steel, the electrodeposition method was used to prepare the diffusion couple of copper and low-carbon steel, which would be annealed under different temperatures for 6 h; meanwhile, the MD models were also used to analyze the diffusion behavior of Cu in Fe at different temperatures. The results show that the diffusion of Cu in low-carbon steel could be realized by high-temperature annealing, and as the temperature increases, the thickness of the Cu/low-carbon steel transition layer shows an increasing trend. When the annealing temperature is between 900 °C and 1000 °C, the thickness of the transition layer increases the fastest. The results of the MD models show that, when the temperature is in the phase transition zone, the main restrictive link for the diffusion of Cu in Fe is the phase transition process of Fe; additionally, when the temperature is higher, the main restrictive link for the diffusion of Cu in Fe is the activity of the atom.

Study on the Bonding Mechanism of Copper-Low Carbon Steel for Casting Compounding Process

The casting compounding process for copper-steel composite material has broad prospects of application, but due to the lack of supporting theories (especially the bonding mechanism of copper-steel at high temperatures), it is developing slowly. In this research, copper-steel composite materials for different casting temperatures have been prepared by the casting compound process. The results show that, for the casting compound process, the stable copper-steel transition layer can be formed in a short time, and the bonding of copper and low carbon steel is the result of both the diffusion of Cu in low carbon steel and the dissolution of Fe in molten copper. The diffusion coefficient of Cu in the low carbon steel is mainly concentrated in the range of 4.0 × 10−15–8.0 × 10−14 m2/s. However, for casting compound process of copper-steel, as the temperature rises the thickness of the copper-steel transition layer gradually decreases, while the Fe content in the copper layer gradually increases. At the same time, the analysis of the glow discharge results shows that, during the solid-liquid composite process of copper-steel, the element C in steel has a great influence. As the temperature rises, the segregation of C intensifies seriously; the peak of the C content moves toward the copper side and its value is gradually increases. The segregation of C would reduce the melting point of the steel and cause irregular fluctuations of the diffusion of Cu in low carbon steel. Therefore, a relatively lower molten copper temperature is more conducive to the preparation of copper-steel composite materials.

Investigation of structural evolution in the Cu-Zr metallic glass at cryogenic temperatures by using molecular dynamics simulations.

In the present work, investigation of structural evolution of Cu33Zr67 specimen during the cooling process from 2500 down to the 300K, 200K, 150K, 100K, 50K, and 10K has been performed at cooling rate of 5K/ps using molecular dynamics simulation. The pair distribution function (PDF) reveals that Zr‒Zr pair causes the splitting of the first peak of the Cu33Zr67 glass at a lower temperature with an increase in height. Splitting of the first and second peaks supports the presence of the inhomogeneous structure with a statistical average of crystal-like and disordered structural regions in the Cu33Zr67 glass. Voronoi cluster analysis indicated that quasi icosahedral clusters such as < 284 > , < 0285 > , and < 0282 > ; mixed-type cluster such as < 0364 > ; and crystal-like clusters such as < 0446 > are responsible for stabilization of glassy phase at 300K, 200K, 150K, 100K, 50K, and 10K. Similarly, the maximum population of the Cu-centered and Zr-centered < 0286 > quasi icosahedral clusters support the stability of the glassy phase over the studied temperature range. Besides, the maximum population of Cu-centered < 0367 > and Zr-centered < 0364 > , < 0367 > , < 0363 > , and < 0365 > mixed-type clusters and Cu-centered < 0448 > and Zr-centered < 0448 > , < 0445 > , < 0446 > , and < 0444 > crystal-like clusters support the possibility of the presence of intermediate phase of CuZr2 at lower temperatures as observed from PDFs. Mean square displacement (MSD) for the Cu33Zr67 glass shows that the diffusion coefficient of Cu and Zr atoms reduces with decreasing temperature from 300 to 10K. Diversity parameter (d) was found to decrease with decreasing temperature.

Diffusion-controlled growth of Cu thin films electrodeposited directly on atomic-layer-deposited WC diffusion barrier for Cu interconnect

Direct copper (Cu) electrodeposition on a 10-nm atomic-layer-deposited (ALD) tungsten carbide (WC) diffusion barrier layer was investigated for building Cu interconnect in silicon (Si)-based microelectronic devices. The diffusion of Cu reducing species under potentiostatic Cu deposition was characterized according to applied cathodic potential in a neutral electrolyte with a concentration ratio of 1:10 for Cu to iminodiacetic acid (IDA) as a complexing agent. The diffusion-controlled nucleation and growth of Cu thin film on the ALD WC was figured out in relation to diffusion coefficients of Cu reducing species that were calculated from both modified current transient curves and more appropriately electrochemical impedance spectroscopy (EIS) analysis. At the end, the diffusion-controlled Cu fill of trenches with an aspect ratio of 6.3 and 15-nm bottom width was conducted by applying −1.4 V vs Ag/AgCl to an ALD-WC-covered, patterned Si wafer specimen.

Investigation of Cu Diffusivity in Fe by a Combination of Atom Probe Experiments and Kinetic Monte Carlo Simulation

In the present study, the diffusion coefficient of Cu in Fe was experimentally estimated from the precipitation kinetics down to 390°C. At this temperature, diffusion couples, which is a typical method to obtain diffusion coefficients, cannot be applied. The matrix Cu concentration and the number density of Cu precipitates in Fe–Cu alloy, which were the main parameters used to estimate the diffusion coefficient, were directly obtained using atom probe tomography. The temperature dependency of the diffusion coefficient of Cu in Fe estimated in the present study was more reliable than that obtained in a previous study, which also reported the diffusion coefficient of Cu in Fe from precipitation kinetics. This indicated that our estimation of the diffusion coefficient of Cu in Fe with atom probe tomography measurements yielded greater accuracy. In addition, the estimated diffusion coefficient of Cu in Fe tended to deviate to higher values from the extrapolated diffusion coefficient of Cu in Fe, which was obtained by diffusion couples, with decreasing temperature. This deviation is discussed by employing a kinetic Monte Carlo simulation.

Intermetallics Disappearance Rate Analysis in Double Multiphase Systems

Electric corrosion of aluminium and copper is investigated experimentally. It is found that the electric corrosion of copper is higher than the electric corrosion of aluminium. It is also clarified that the intrinsic diffusion coefficient of Cu is higher than the intrinsic diffusion coefficient of Al in each phase, so inert markers move to Cu. Copper has a higher electric conductivity, higher thermal conduction, and lower material cost than gold, so it is possible to use Cu instead of Au for wire bonding in microelectronics packaging, because the thin Al pad (1.2 μm thickness) can prevent gold and copper corrosion. Intermetallics disappearance and Kirkendall shift rates calculation methods are proposed. Methods involve mass conservation law and concentration profiles change during mutual diffusion. Intermetallics disappearance and Kirkendall shift rates in Al-Cu (Al is thin layer on Cu), Cu-Al (Cu is thin layer on Al), Al-Au, Zn-Cu, and Cu-Sn systems are analyzed theoretically using literature experimental data. Diffusion activation energies and pre-exponential coefficients for Cu-Sn system were calculated combining literature experimental results.

Swirl-like Cu-Sn phase formation and the effects on the ultrasonic spot welded joint of Sn-coated Cu plates

Previous studies have shown that sharp physical and chemical changes may induce the formation of swirl-like reaction phases in the ultrasonic spot welding (USW) of different materials. However, the mechanisms have not been well understood. In particular, swirl-like structures have seldom been discovered or discussed in the USW of Cu/Sn. In this study, swirl-like phases were observed in the USW of a Sn-coated T2 Cu plate with different welding energies (300−400 J). The evolution of the microstructure from the flat region to the swirl region was studied, the diffusion coefficient of Cu in Sn and the peak temperature of the interface during welding were theoretically calculated and experimentally verified, the formation mechanism of the swirl-like phases was discussed, and the relationship between the joint properties and welding energies was investigated. The results show that the content of Cu3Sn increases, while that of Cu6Sn5 decreases gradually from the flat region to the swirl region and that grain refinement of Cu and IMCs occurs near the swirl regions. The greatly enhanced diffusivity shows that intense atomic diffusion takes place during the welding process. When the welding energy exceeds 300 J, the experimentally measured peak temperatures in the welding processes are higher than the theoretical values. The formation of the swirl-like phase is attributed to the uneven distribution of interfacial stress and the collapse of cavitation bubbles. When the welding energy reaches 400 J, the peak lap shear load of the welded specimen reaches 1008 N, and the associated fractures indicate the combined characteristics of ductility and brittleness.

Study on Dissolution of Al2Cu in Al-4.3Cu and A205 Cast Alloys

Evolution of microstructure in a binary Al-Cu system (Al-4.3Cu) and a commercially alloyed Al-Cu system (A205) during solution heat treatment was investigated using optical microscopy (OM), scanning electron microscopy (SEM), wavelength-dispersive X-ray spectroscopy (WDS), and differential scanning calorimetry (DSC). The diversified coarseness of the microstructure was initiated by controlling the solidification rate. Different solution treatment temperatures were applied to identify a proper solutioning temperature. The larger microstructural scale required an increased solutioning temperature and prolonged holding time to obtain homogenized solutes in the α-Al matrix. The diffusion of Cu primarily controlled the solution heat treatment process. A diffusion-based model was applied and calibrated to determine the dissolution rate of an Al2Cu particle in the matrix. The model operates on a similar time scale with the experimental results for the Al-4.3Cu and A205 alloys with various microstructural scales, different chemical compositions, and at different solution treatment temperatures. Three-dimensional (3D) reconstructed images from SEM images and energy dispersive spectroscopy (EDS) map of elements showed that TiB2 particles shield the Cu-rich phases in the boundaries of α-Al grains, presumably acting as a physical barrier to the diffusion of Cu solutes toward α-Al grains. The model also suggests that the effective diffusion coefficient of Cu in Al, in the presence of TiB2 particles, reduced by a factor of 2.0–2.5 in the A205 alloy compared with the binary Al-Cu alloy.

Solution Chemistry of Alkaline Formaldehyde-Containing Electroless Copper Plating Systems and Kinetics of Electroless Copper Deposition

Electroless copper plating process using solutions containing formaldehyde as reducing agent is known from the middle of this century and are widespread in the practice up to now. However, the investigation of this system remains actual because of its complexity, e. g. alkaline medium, hydrated form of formaldehyde (methanediol), Cu(II) complex compounds with different ligands, additives which improve the properties of the coatings obtained and/or protect from the reduction of copper(II) in the solution bulk. Moreover, various equilibria are possible including deprotonation of methanediol, Cu(II) complex formation, additional interactions between components of the solution.The aims and tasksof this work were to investigate or define more precisely equilibria in conventional alkaline solutions of electroless copper deposition as well as influence of the nature of Cu(II) ligands on the copper deposition process. This research report deals with the results obtained by means of dc-polarography, vis-spectrophotometry, voltammetry, potentiometry, pH-metry, 1H and 13C NMR spectroscopy, scanning electron microscopy, X-ray diffractometry and gravimetry.The composition, stability and the values of the diffusion coefficient of Cu(II) complex compounds with ligands (EDTA, DTPA, pyridine-2,6-dicarboxylic acid and 4-hydroxypyridine-2,6-dicarboxylic acid, Quadrol, L(+)-, D(–)- and DL(-/+)-tartrate, glycerol, saccharose and OH- ions) which are used or usable in alkaline electroless copper deposition solutions were established. Formation of mixed complex compounds between Cu(II) complexonates andK4Fe(CN)6, as well as between Cu(II) tartrate complexes and methanediol was investigated. The interaction of methanediol with L(+)-tartrate alongside with the influence of the ionic strength and cation nature on the deprotonation of methanediol in alkaline solutions were studied.The kinetic data on electroless copper deposition from solutions containing above-mentioned ligands are presented and the influence of the ligand nature on the process of electroless copper deposition is discussed.

Copper and Li diffusion in plagioclase, pyroxenes, olivine and apatite, and consequences for the composition of melt inclusions

Silicate melt inclusions are an important tool to reconstruct original concentrations of volatiles and metals in silicate melts, as these constituents are partly lost during magma solidification. However, melt inclusions analyzed in co-precipitated minerals in volcanic rocks commonly show strongly divergent Cu contents, raising doubts about the validity of their composition. To understand the origin of this divergence a multiple approach was followed. First, the phenomenon was documented by recording petrographic details of five volcanic samples and analyzing 189 melt inclusions by laser-ablation ICP-MS. Second, diffusion experiments on gem-quality plagioclase, clinopyroxene, orthopyroxene, apatite and olivine were performed in a gas mixing furnace to constrain diffusion coefficients of Cu and to a lesser extent of Li. Third, re-equilibration experiments were performed on melt inclusions within plagioclase crystals to induce changes in their Cu and Li contents.The LA-ICP-MS analyses reveal that plagioclase-hosted and orthopyroxene-hosted melt inclusions in volcanic rocks commonly contain an order of magnitude more Cu than melt inclusions in co-precipitated clinopyroxene and olivine. Plagioclase-hosted melt inclusions in intrusive rocks, on the other hand, do not show this divergence. The diffusion experiments conducted on minerals find that Cu and Li diffusion in plagioclase is extremely fast (log D = −13.0 to −11.5 m2 s−1 at 1000 °C) and in both cases occurs via two separate diffusion mechanisms. Copper diffusion coefficients in apatite, clinopyroxene, orthopyroxene and olivine are 2–3 orders of magnitude lower but are still high compared to most other elements. Both the re-equilibration experiments on melt inclusions and quantitative modeling based on the measured diffusion coefficients demonstrate that at 1000 °C plagioclase-hosted melt inclusions can re-equilibrate their Cu and Li content with that of the surrounding magma within a few hours to a few weeks, whereas apatite-, clinopyroxene-, orthopyroxene- and olivine-hosted melt inclusions require tens of years to hundreds of years to do so. Abnormally high Cu contents of plagioclase- and orthopyroxene-hosted melt inclusions appear to result from postentrapmental Cu gain. In the case of orthopyroxene-hosted melt inclusions Cu seems to have been gained as a consequence of postentrapmental sidewall crystallization, which triggered the formation of sulfide globules that acted as a Cu sink. This process likely occurred at depth in magma chambers. Plagioclase-hosted melt inclusions, on the other hand, seem to have gained Cu in exchange for hydrogen that diffused out of the melt inclusions during or after volcanic eruption. Our results suggest that Cu (and also Li) concentrations measured in melt inclusions have to be generally treated with caution, and that particular prudence has to be used in the case of plagioclase and orthopyroxene hosts.

Comproportionation Reaction of Cu(II)/Cu(0) in Ethaline-Water Mixed Solvents

The comproportionation reaction of Cu(II) + Cu(0) → 2Cu(I) in ethaline-water mixed solvents has been studied by means of different electrochemical techniques such as cyclic voltammetry, linear sweep voltammetry and chronopotentiometry. The cyclic voltammograms of Cu(II) show two couples of redox peaks in all mixtures, which demonstrate that the comproportionation reaction is thermodynamically favorable. In order to clarify the reaction kinetics of this heterogeneous reaction, the diffusion coefficient of Cu(II) and the rate constant of the reaction were estimated. Results show that the apparent reaction rate constant mainly depends on the diffusion of the Cu(II) species in all the mixtures. Thus, adding water into ethaline can enhance the mass transfer of Cu(II) species and increase the reaction rate.

Micro/nanostructured porous ZnO as a new DGT binding phase for selective measurement of Cu(II) in water

Micro/nanostructured porous ZnO was first utilized as a new binding phase in DGT (diffusive gradients in thin film) devices for selective measurement of Cu(II) in water, on the basis of its selective adsorption performance. In this case, the accumulated heavy metal ions onto the binding phase could be easily determined by a simple complete acid-dissolution elution process without the complicated elution experiments including measurement of elution efficiency. The selective adsorption performance of the micro/nanostructured porous ZnO towards Cu(II) was evaluated in single- and ternary-component metal solutions [Cu(II), Ni(II) and Cd(II) ions]. It was found that the adsorption amount and adsorption rate of Cu(II) ions onto the porous ZnO were the highest by comparing with that of Ni(II) and Cd(II) ions, exhibiting strong adsorption and good selectivity toward Cu(II) ions. The adsorption of heavy metal ions on the ZnO can be well described by Pseudo-second-order model, implying chemical bonding related interaction between the porous ZnO and heavy metal ions. Importantly, the ZnO was utilized as binding phase of DGT device for heavy metal ions measurement, the diffusion coefficient of Cu(II) in the diffusive gel was calculated to be 6.13×10−6cm2s−1, implying such ZnO could be a new potential binding phase towards trace Cu(II) ions detection.