Precipitation Of Cu Research Articles

A simplified invariant line analysis for face-centred cubic/body-centred cubic precipitation systems

Several phenomenological crystallographic theories, including the invariant line model, O-line analysis and Δgparallelism rules, have been proposed and then successfully applied to the interpretation of crystallographic features for most face-centred cubic/body-centred cubic precipitation systems. However, the application of these methods requires the use of extra criteria and multiple rotations. A simplified invariant line analysis is proposed in this paper, to simplify the above theories from the well known confusions of additional criteria and multiple rotation around specific axes. One-step rotation dispenses with extra criteria or any input orientation relationship and so can deduce an invariant line when a Burgers vector is parallel to the habit plane. This simplified analysis makes the application of the theory more understandable, where it anticipates the invariant line, the habit plane, the orientation relationship between the matrix and the precipitate, and the distance between dislocations for which the Burgers vector is not inclined. The predictions are simplified, highly efficient and coincide well with experimental observations from lath-shaped precipitates in Cu–Cr and Ni–Cr alloys, as well as with the theoretical results obtained by O-line theory and Δgparallelism rules.

Use of liming in the remediation of soils polluted by sulphide oxidation: A leaching-column study

Pure CaCO 3 in ascending quantities was added to a soil to study the effect of liming after contamination by an acidic solution from the oxidation of pyrite tailings. The samples were placed in percolation columns, and soils and leachates were monitored. In the soil samples, the mineralogy, pH, CaCO 3, iron, and total content in Cu, Zn, As, Cd, and Pb were determined. The presence of CaCO 3 in the soils considerably limited their acidification, favouring the precipitation of Cu, Zn, and Cd, and promoting precipitation of iron and SO 4 2− ions in the form of iron hydroxysulphates and gypsum. The iron hydroxysulphates tended to retain the less mobile elements (As, and Pb) near the top of the soil. The more mobile elements (Zn, Cd and Cu) precipitated in deeper layers, directly related mainly to the CaCO 3 added and to pH. The CaCO 3 clearly did not reduce Zn and Cd toxicity effectively enough, given that the concentrations of both elements were above the toxic level in all leachates. The amounts of liming needs to be properly controlled, as excessively high pH limits As fixing, at the same time as the effectiveness of CaCO 3 is limited by coating precipitation, reducing its capacity to react with the acidic solution.

Modeling homogeneous precipitation with an event-based Monte Carlo method: Application to the case of Fe–Cu

A precipitation model for an event-based kinetic Monte Carlo (EKMC) method is presented. It is based on atomic-scale computations of the emission and absorption rates of monomers by clusters. Clusters are considered as single objects that emit monomers close to them, at higher rates than predicted by the mean field cluster dynamics method. We show that a law based on continuous diffusion equation can be used to account for absorption, provided the reaction distances between clusters are accurately computed. The model is shown to reproduce quantitatively results obtained by atomistic kinetic Monte Carlo methods when only monomers are mobile. The kinetics obtained by EKMC is faster than the one given by cluster dynamics, which highlights the limits of such a mean-field method, especially at high solute concentrations. When applied to the precipitation of Cu in Fe, which involves the mobility of clusters, the EKMC model shows good agreement with experimental results.

Influence of cluster mobility on Cu precipitation in α-Fe: A cluster dynamics modeling

A cluster dynamics model has been parametrized to quantitatively reproduce results obtained by atomistic kinetic Monte Carlo (AKMC) modeling on the precipitation of Cu in α-Fe under thermal aging. The cluster mobility, highlighted by AKMC, is shown to have a significant effect on the precipitation kinetics and can reconcile the experimentally observed fast kinetics with the relatively low diffusivity of Cu monomers.

TEM Study and Magnetic Measurements of Nano–Scale Particles Formed in Cu–Base Alloys

The precipitation behavior of nano–scale particles formed in Cu–base alloys was studied by means of transmission electron microscopy (TEM) and SQUID measurements. Linear arrangements of two or more nano–scale particles cubic in shape were observed in the <100> orientations of matrices in a Cu–Co alloy. Although the trend was less explicit in a Cu–Fe alloy, Fe precipitates accompanying twin–like lattice modulations were found in the decomposition, when no deformation was applied. The present SQUID measurements revealed several significant influences to magnetic properties were induced during the precipitation in Cu–base alloys. Lorentz electron microscopy confirmed that phase transformation from γ → α occurred at the stage that the Fe particles reach to 40~60nm in size.

Effect of ageing on the mechanical properties of directly quenched copper bearing microalloyed steels

The present work aims to study the ageing behaviour of directly quenched Cu-added microalloyed steels. Temperatures related to precipitation of Cu and recovery of dislocations retained in the microstructure after quenching of the steels from finish rolling temperature are determined by differential scanning calorimetric method. Ageing of the directly quenched steels has resulted in the reduction in hardness and strength with concomitant improvement of ductility. 1.5 wt% Cu-added Ti–B microalloyed steel has yielded the most attractive combination of strength and ductility. Presence of Ni in the 1.5 wt% Cu-added Ti–B microalloyed steel indicates sluggish kinetics of Cu precipitation. Ageing has generally deteriorated the impact toughness except for Ni containing Cu-added microalloyed steel above −25 °C temperature. Formation of recovered dislocation cells and fine ɛ-Cu precipitates during ageing have contributed to the microstructural softening and hardening, respectively.

Combined XBIC/μ‐XRF/μ‐XAS/DLTS investigation of chemical character and electrical properties of Cu and Ni precipitates in silicon

AbstractCombination of DLTS method and synchrotron‐based analytical microprobe techniques was used to study the precipitation of Cu and Ni atoms at two kinds of structural defects in silicon lattice: dislocation network created by direct wafer bonding and oxygen‐induced microdefects. Results of our measurements revealed the difference in the preferred precipitation places: Ni particles in form of NiSi2 were found only at the dislocation network, while Cu particles in form of Cu3Si were found both at the dislocation network and at the oxygen‐induced microdefects. DLTS measurements showed Ni acceptor levels in Ni contaminated sample and a broad band related to Cu precipitates in Cu contaminated one. In case of simultaneous Cu and Ni contamination NiSi2 and Cu3Si precipitates were found definitely at the same places indicating therefore that the metals interact during precipitation. DLTS showed the superposition of spectra for only Ni and for only Cu contaminated samples. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Separate recovery of copper and zinc from acid mine drainage using biogenic sulfide

Precipitation of metals from acid mine drainage (AMD) using sulfide gives the possibility of selective recovery due to different solubility product of each metal. Using sulfate reducing bacteria to produce sulfide for that purpose is advantageous due to in situ and on-demand sulfide production. In this study, separate precipitation of Cu and Zn was studied using sulfide produced in anaerobic baffled reactor (ABR). ABR fed with ethanol (1340 mg/L chemical oxygen demand (COD)) and sulfate (2000 mg/L) gave a stable performance with 65% sulfate reduction, 85% COD removal and around 320 mg/L sulfide production. Cu was separately precipitated at low pH (pH < 2) using sulfide transported from ABR effluent via N 2 gas. Cu precipitation was complete within 45–60 min and Zn did not precipitate during Cu removal. The Cu precipitation rate increased with initial Cu concentration. After selective Cu precipitation, Zn recovery was studied using ABR effluent containing sulfide and alkalinity. Depending on initial sulfide/Zn ratio, removal efficiency varied between 84 and 98%. The low pH of Zn bearing AMD was also increased to neutral values using alkalinity produced by sulfate reducing bacteria in ABR. The mode of particle size distribution of ZnS and CuS precipitates was around 17 and 46 μm, respectively.

Determination of the interface energies of spherical, cuboidal and octahedral face-centered cubic precipitates in Cu–Co, Cu–Co–Fe and Cu–Fe alloys

The coarsening theory of a spherical particle in a ternary alloy developed by Kuehmann and Voorhees (KV) has been generalized to any centro-symmetric particle. A classical thermodynamic analysis reveals that the generalized KV theory enables us to estimate the interface energy of a particle with a fixed shape, even if the shape of the particle is not controlled by minimization of the interface energy. Data on the coarsening of spherical, {001}-faceted cuboidal and {111}-faceted octahedral precipitates in a Cu–Co alloy, a Cu–Fe alloy, and three Cu–Co–Fe alloys with different Co and Fe contents during aging at 873–973K have been collected by transmission electron microscopy and electrical resistivity. By applying the generalized KV theory to the experimental data, the energies of sphere, {001} and {111} interfaces have been determined. Their energies increase with increasing the Fe composition in the alloys.

Effect of magnetism on precipitation of Cu in bcc Fe: Ab-initio based modeling

AbstractTheoretical modeling of the decomposition in bcc Fe-Cu alloys has been performed using a combined approach which includes ab-initio calculations of the effective cluster interactions and statistical-mechanical (Monte Carlo) simulations. We showed that the effective Cu-Cu and Cu-vacancy interactions in the bcc Fe matrix have a strong dependence on the global magnetic state of iron. As a result, all the related thermodynamic properties of the alloys (such as solubility limit and diffusivity) are expected to have a pronounced non-Arrhenius temperature behavior, originated from variation of the global magnetization with temperature. We find that strong Cu-vacancy interactions in the bcc Fe matrix lead to a remarkable effect of vacancies on the Cu precipitation and significantly modify the alloy decomposition kinetics under irradiation.

Small-angle X-ray scattering characterization of precipitates in Cu–Ti alloys

In order to understand the aging characteristics of Cu–Ti alloys, extended X-ray absorption fine structure (EXAFS) and small-angle X-ray scattering (SAXS) measurements were performed for characterizing changes in the local structure around titanium and the precipitate size in the Cu–Ti alloys by aging at approximately 720 K after solution treatment. Cu–1.3, 2.6, and 4.5 at.% Ti alloys were prepared using high-purity base metals. The amount of titanium dissolved in the copper matrix during aging was estimated from the electrical resistivity of the alloys. The aging characteristics showed that the precipitation rate of Cu–Ti intermetallic compounds in the copper matrix increased with increasing bulk titanium amount. The local structures of titanium in precipitates, presumably Cu 4Ti, are indistinguishable in the present alloys by EXAFS analysis because of the similarity of EXAFS functions for a Cu 4Ti intermetallic compound and a substitutional solid solution in copper. However, the EXAFS analysis revealed that the atomic distance of a Cu–Ti pair was significantly smaller than that estimated from the atomic radii of copper and titanium, implying that there is a strong atomic correlation in the pair. SAXS measurements were carried out for analyzing the growth behavior of precipitates in alloys during aging. The SAXS results revealed that a small amount of precipitates was formed in Cu–1.3 at.% Ti in the initial aging stage, whereas precipitates with approximately 2 nm radius were formed in Cu–2.6 and 4.5 at.% Ti alloys. By aging up to 2000 s, the precipitates in Cu–1.3, 2.6 and 4.5 at.% Ti alloys grew to approximately 3.5 nm in radius. These aging characteristics were discussed on the basis of the number density of precipitates calculated from the size of precipitates and the amount of super-saturated titanium in the copper matrix.

Selective precipitation of Cu from Zn in a pS controlled continuously stirred tank reactor

Copper was continuously and selectively precipitated with Na 2S to concentrations below 0.3 ppb from water containing around 600 ppm of both Cu and Zn in a Continuously Stirred Tank Reactor. The pH was controlled at 3 and the pS at 25 (pS = −log(S 2−)) by means of an Ag 2S sulfide selective electrode. Copper's recovery and purity were about 100%, whereas the total soluble sulfide concentration was below 0.02 ppm. X-ray diffraction (XRD) analysis showed that copper precipitated as hexagonal CuS (covellite). The mode of the particle size distribution (PSD) of the CuS precipitates was around 36 μm. The PSD increased by high pS values and by the presence of Zn. Depending on the turbulence, the CuS precipitates can grow up to 200 μm or fragment in particles smaller than 3 μm in a few seconds. Zn precipitation with Na 2S at pH 3 and 4, in batch, always lead to Zn concentrations above 1 ppm. Zn precipitated as cubic ZnS (spharelite).

Study on reaction kinetics and selective precipitation of Cu, Zn, Ni and Sn with H 2S in single-metal and multi-metal systems

Determination of reaction kinetics and selective precipitation of Cu, Zn, Ni and Sn with H 2S in single-metal and multi-metal systems were studied to develop a process of metal recovery from plating wastewater. As samples, single-metal model wastewaters containing Cu, Sn, Zn or Ni, and multi-metal model wastewater containing Cu–Zn–Ni or Sn–Zn mixtures were used. In both single-metal and multi-metal systems, the pH value was precisely controlled at a value of 1.5 for CuS and SnS precipitation, 4.5 for ZnS precipitation and 6.5–7.0 for NiS precipitation. Subsequently, the sulfidation of Cu, Sn, Zn and Ni was evaluated. It was found that an amount of H 2S equimolar to a given metal was sufficient to achieve almost complete precipitation of the particular metal. Further, the selectivity of metal precipitation was found to be higher than 95% in the Cu–Zn–Ni multi-metal system and higher than 91% in the Sn–Zn system. It was also found that the sulfidation reaction proceeded in accordance with Higbie’s penetration theory and reaction rate constants and mass-transfer coefficients under various experimental conditions were determined. Finally, the reaction rate constants obtained in single-metal and multi-metal systems were found to be almost the same indicating that the precipitation of a particular metal was not significantly affected by the presence of other components.

Comparative study of Cu 2+ adsorption on a zeolite, a clay and a diatomite from Serbia

The adsorption of a zeolite, clay and diatomite from Serbia toward aqueous Cu 2+ ions was studied, at different pH. The adsorbents were characterized with respect to phase composition, specific surface area and point of zero charge. The amounts of Cu 2+ removed from the solution, increased with increasing initial pH, reaching nearly 100% at pH > 7, regardless of the adsorbent type and metal concentration, due to precipitation of Cu(OH) 2. Relatively constant final pH values and less significant increase of Cu 2+ uptake observed in the initial pH range 4–6 have pointed out the role of buffering properties of investigated adsorbent materials. The maximum adsorption capacities decreased in the order zeolite (0.128 mmol/g) > clay (0.096 mmol/g) > diatomite (0.047 mmol/g). The Langmuir equation was most suitable for data fitting. The proportion of Cu 2+ desorbed in acidic media decreased with the increase of previously adsorbed amounts by zeolite and clay, while the opposite was true for diatomite. Ion exchange of exchangeable cations and protons were identified as main adsorption mechanisms, with latter being most apparent in the removal mechanism of diatomite. Considering low-cost, local availability and environmentally friendly materials, zeolite exhibited highest potential for environmental and health protection applications.

Diffusion-Temperature-Dependent Formation of Cu Centers in Cu-Saturated Silicon Crystals Studied by Photoluminescence and Deep-Level Transient Spectroscopy

Using photoluminescence (PL) and deep-level transient spectroscopy (DLTS) we observed the concentration changes of Cu-related centers in silicon crystals saturated with Cu at various temperatures (600–1000 °C), in which each sample was measured at the same location for both methods. The DLTS peak assigned to have the same origin as the 1.014 eV PL center (CuPL center) was by far the strongest component among the DLTS peaks, and no DLTS peak due to isolated substitutional Cu (Cus) was observed for any of the diffusion temperatures used. The PL and DLTS intensities of the CuPL center increased with increasing diffusion temperature of Cu from 600 to 700 °C, reached a maximum between 700 and 800 °C, then sharply decreased at higher temperatures than 800 °C. This behavior was reasonably explained by considering the outdiffusion and precipitation of Cu in addition to the solubility of Cu. The maximum DLTS concentration of the CuPL center (∼1014 cm-3) observed in the present study far exceeded the estimated concentration of Cus formed through a vacancy-mediated reaction. From this finding we concluded that a model containing Cus was invalid for the CuPL center and that another model containing unique Cu atom at the center of the Si–Si bond was realistic.

Anhydrite pseudomorphs and the origin of stratiform Cu–Co ores in the Katangan Copperbelt (Democratic Republic of Congo)

The stratiform Cu–Co ore mineralisation in the Katangan Copperbelt consists of dispersed sulphides and sulphides in nodules and lenses, which are often pseudomorphs after evaporites. Two types of pseudomorphs can be distinguished in the nodules and lenses. In type 1 examples, dolomite precipitated first and was subsequently replaced by Cu–Co sulphides and authigenic quartz, whereas in type 2 examples, authigenic quartz and Cu–Co sulphides precipitated prior to dolomite and are coarse-grained. The sulphur isotopic composition of the copper–cobalt sulphides in the type 1 pseudomorphs is between −10.3 and 3.1‰ relative to the Vienna Canyon Diablo Troilite, indicating that the sulphide component was derived from bacterial sulphate reduction (BSR). The generation of $${\text{HCO}}_3^ - $$ during this process caused the precipitation and replacement of anhydrite by dolomite. A second product of BSR is the generation of H2S, resulting in the precipitation of Cu–Co sulphides from the mineralising fluids. Initial sulphide precipitation occurred along the rim of the pseudomorphs and continued towards the core. Precipitation of authigenic quartz was most likely induced by a pH decrease during sulphide precipitation. Fluid inclusion data from quartz indicate the presence of a high-salinity (8–18 eq. wt.% NaCl) fluid, possibly derived from evaporated seawater which migrated through the deep subsurface. 87Sr/86Sr ratios of dolomite in type 1 nodules range between 0.71012 and 0.73576, significantly more radiogenic than the strontium isotopic composition of Neoproterozoic marine carbonates (87Sr/86Sr = 0.7056–0.7087). This suggests intense interaction with siliciclastic sedimentary rocks and/or the granitic basement. The low carbon isotopic composition of the dolomite in the pseudomorphs (−7.02 and −9.93‰ relative to the Vienna Pee Dee Belemnite, V-PDB) compared to the host rock dolomite (−4.90 and +1.31‰ V-PDB) resulted from the oxidation of organic matter during BSR.

Microstructure and Mechanical Property of Copper Bearing Eutectoid Steel

Isothermal heat treatment was performed for austenitized Cu bearing eutectoid steels (Fe–0.8%C–Cu alloys). Microstructural observations revealed that the pearlite transformation is significantly retarded by the addition of Cu, but the morphology of pearlite, such as lamellar spacing and block size, are hardly influenced by the Cu addition. From the result of chemical analysis for cementite phase, it was found that the redistribution of Cu had occurred between ferrite and cementite through the interfacial diffusion during pearlite transformation and then the precipitation of Cu takes place simultaneously within ferrite phase. Furthermore, in the 2% Cu steel, age hardening behavior was found at the same temperature applied to the isothermal pearlite transformation. This means that the precipitation of Cu does not complete on pearlite transformation and the ferrite in pearlite structure is in the supersaturated state. Yield strength and tensile strength of the pearlite steels depend on not only lamellar spacing but also the dispersion of Cu particles within the ferrite phase. For example, 2% Cu addition increases yield strength and tensile strength by about 250 MPa without reducing ductility so much.

Effect of prestrain on aging behaviour of directly air cooled copper added titanium–boron microalloyed steels

The present investigation concerns effect of prestrain on the precipitation of Cu during aging of directly air cooled Ti–B microalloyed steels. The differential scanning calorimetry studies allow to identify that precipitation of Cu is most prominent between 350 and 500°C. Prestraining of the directly air cooled samples has broadened the temperature range for Cu precipitation with perceptible overlapping with the peaks due to other low temperature reactions like recovery and/or tempering. Fifty per cent prestraining of 1·5 wt-%Cu added steel before aging triggered the precipitation reaction at a temperature ∼320°C with pronounced decrease in the activation energy values from 172 to 116 kJ mol−1. Microstructural changes due to prestraining are evident in the micrographs obtained from transmission electron microscope as deformed ferrite laths and formation of cell structures therein. While 15–50% prestraining has increased the strength without much deterioration in ductility; aging of the prestrained samples has improved the strength and ductility concomitantly.

Copper concentration dependence of structure, morphology and optical properties of ZnS:Cu,Cl phosphor powder

ZnS:Cu,Cl phosphors were prepared by firing ZnS powder with 1 wt% NaCl and CuS nanocrystallites in the range of 40–5000 ppm at 900 °C for 2 h in an atmosphere of 3% H 2/Ar and sulfur vapor. The particle size and structure of the ZnS:Cu,Cl powders were found to depend on the Cu concentration. The powders with Cu⩾400 ppm exhibited a cubic structure and were approximately 5 μm in size as compared to the hexagonal structure of those with less Cu additions (∼2 μm). The difference, resulting from the precipitation of Cu x S in the powders as determined by X-ray photoelectron and diffuse reflectivity analyses, revealed that the powders with Cu>400 ppm showed the Cu 2p main peaks and higher absorbance in the UV–vis region due to the wide range of the bandgap energy of Cu x S (1.2–1.75 eV). Electroluminescence (EL) consisting of blue, self-activated (SA) and green emission peaking at 440, 470 and 510 nm, was observed only in the powders with Cu⩾400 ppm. Besides the activator concentration quenching effect, the variation of EL intensity with the Cu concentration was elucidated to result the from amount of Cu x S precipitates as well as charge carriers in the powders.

Biosorption properties of extracellular polymeric substances (EPS) towards Cd, Cu and Pb for different pH values

The aim of this study was to assess the influence of pH on the metal biosorption of extracellular polymeric substances (EPS) extracted from two different activated sludges called A and B. The composition and physico-chemical characteristics of EPS were determined. The biosorption capacities of the EPS were examined at pH 4, 6, 7 and 8 successively with three metals Cu, Pb and Cd using differential pulse polarography (DPP) as an investigation tool and Ruzic's model was used to produce polarographic titration curves. Two apparent p K a were obtained, the first were 6.6 (EPS A) and 5.7 (EPS B), attributed to carboxylic and phosphoric groups whereas the second was 8.7 for EPS A and 9.4 for B and these were attributed to phenolic and amino functional groups. Whatever the EPS and the metal considered, the conditional binding constant did not show significant differences in the strength of complex formed between the EPS and metals. But for all metals, the number of EPS binding sites was significantly lowered by a decrease in the pH of the medium. At pH 4, the metal biosorption capacity of EPS is very low. At pH 6, the number of EPS binding sites increased in the following order: Pb > Cu > Cd whereas at pH 7 and 8, this order changed and was: Cu > Pb ≫ Cd. Simulations of the speciation states of Cu, Pb and Cd at the different pH values in ultra-pure water (25 °C, ionic strength 0.045 M) were performed with MINEQL 4.5 software and indicated the presence of hydroxylated forms and sometimes solid forms for Pb and Cu. But the polarographic titration curves revealed precipitation of Cu only at the end of the experiments at pH 8.