Precipitation Of Cu Research Articles

AlCu-Al2O3 metal matrix composites studied by thermoelectric power measurements

Metal matrix composite materials Al-4%Cu reinforced with different volumetric fractions of Al 2 O 3 (Saffil) fibers were produced by «squeeze casting». The composites were characterized by thermoelectric power measurements, in order to identify the effect of the fibers on the precipitation of Cu and the microstructure of the alloy. The formation of Guinier-Preston zones was found to be slowed down by the presence of fibers, while the formation of θ'precipitates was favoured in the composites. A TTT diagram of Cu precipitation in the composites was drawn, which well characterized their different response to ageing compared to that of the unreinforced matrix

Organic matter and copper mineralization at White Pine, Michigan, U.S.A.

Indigenous and exogenous organic matter in sediments of the North American Midcontinent Rift were involved in precipitation of Cu-bearing minerals during main- and second-stage mineralization events at White Pine, Michigan. Samples of the Proterozoic Nonesuch Formation from the White Pine mine and adjacent areas were investigated petrographically and geochemically in order to determine the influence of organic matter on the precipitation of Cu and to determine whether mineralization influenced thermal maturity of organic matter. During main-stage mineralization, introduction of cupriferous fluids into the lower Nonesuch Fm. formed Cu-bearing sulfides by replacement of pyrite. Sulfur may have been added to the system via abiogenic sulfate reduction, with organic matter providing a direct source of reducing potential. In basal ore horizons where all sulfide had been incorporated into chalcocite during main-stage mineralization, native Cu also precipitated locally, with organic matter presumably acting as a direct reductant. Later compressional faulting at White Pine provided conduits for additional cupriferous fluids; these fluids deposited second-stage Cu mineralization. Inclusions of liquid petroleum and solid pyrobitumen in veins filling fractures associated with compressional faults record migration of petroleum into the White Pine district from the deeper, hotter, axis of the rift penecontemporaneous with second-stage fluids. Some of this petroleum may have acted as a reductant during precipitation of native Cu in basal ore horizons. Biomarker compositions of bitumens and isotopic compositions of individual n-alkanes from petroleums and bitumens suggest that these materials were all derived from organic matter deposited during sedimentation of the Nonesuch Fm.. Biomarker data demonstrate that bitumens from the White Pine area have significantly higher levels of thermal maturity than bitumens from unmineralized strata outside the mine area. Therefore, Cu mineralization at White Pine coincides with a thermal anomaly. Seep petroleums from the northeast and southwest domains of the mine contain different n-alkane distributions; we propose that this difference reflects elevated thermal maturity of seep petroleums spatially associated with second-stage mineralization in the southwestern domain of the mine.

Hydrothermal geochemistry and ore genesis of sea-floor volcanogenic copper-bearing oxide ores

The term copper-bearing mineralization is proposed to describe exhaled sea-floor chemical sediments, which are dominated by magnetite, quartz, and hematite, with subordinate chalcopyrite, pyrite, and in some cases, gold; they occur within or close to volcanic piles.Three Australian examples (the Starra, Osborne, and Big Cadia deposits) form the basis for a more general volcanogenic copper-bearing oxide model. The shapes of the deposits vary from massive mounds and pods (Cadia) with no laterally developed sedimentary iron-formation, through to extensive well-banded stratiform examples (Osborne). The orebody style of the deposits correspondingly varies from small high-grade Cu-Au lenses such as Area 251 at Starra (2.6 Mt at 6.7 g/t Au, 3.4% Cu), to large lower grade deposits such as Osborne (13.6 Mt at 1.9% Cu and 1.0 g/t Au, including a higher grade pod). In all cases intense footwall alteration is present (a hallmark of vent-proximal exhalative sediments), varying from albite-iron oxide-chlorite, to massive quartz-iron oxide, to muscovite-epidote-chlorite, depending on the salinity and pH of the ore fluid, and the presence or absence of boiling solutions. At Osborne, three stratigraphic ore positions record three episodes of hydrothermal activity in a stacked system, with evidence of overprinting in the earlier exhalites. At Starra and Cadia, there is evidence that the most proximal exhalites are dominated by magnetite, quartz, and chalcopyrite, whereas the distal portions are hematite dominated and variably pyritic.Ore formation is attributed to precipitation from the oxidized and H 2 S-deficient version of a volcanic-hosted massive sulfide fluid, in an oxidized water column. Such fluids must be buffered by hematite and/or magnetite during deep footwall fluid-rock reaction below vent complexes, to provide a sink for H 2 S produced by the reduction of seawater sulfate. Thus the ore type is favored in intracontinental basins which are common hosts for the requisite oxidized fluvial and shallow-marine sediments. A second possible source of oxidized metal-bearing fluids is highly fractionated magnetite series granites; in the Australian Proterozoic these are particularly prevalent in rift settings. To achieve Cu-Au solubility as chloride complexes, and to account for the ore mineral assemblages, the ore fluids must have had a T = 260 degrees to 380 degrees C, a log f (sub O 2 ) = -27.5 to -30, a pH = 3.9 to 6, and an Sigma S approximately 10 (super -3) M. High salinities are not an essential condition but serve to greatly enhance the efficiency of metal transport by increased chloride ion pair metal solubility. Higher salinities favor the transport of the elements Au, W, Sn, Mo, and Co, which constitute a distinct secondary element association. Salinity is also the strongest control on ore deposit shape by determining the behavior of the fluid after it exits from the vent; for instance, modeling suggests that a high-salinity fluid cooling at constant pH can explain the Si/Fe ratio and thickness of some Starra ore lenses.An important geochemical feature of volcanic copper-bearing oxide mineralization is a distinct depletion of Pb and Zn (usually less than 10 ppm of each occurs in ore zones). This is attributed to the very low H 2 S content of the ore fluid and water column, which permits precipitation of Cu and Fe as chalcopyrite and pyrite at temperatures greater than approximately 280 degrees C, removing all H 2 S prior to galena and sphalerite saturation. A volcanic copper-bearing oxide brine, from which Cu was removed at the vent, could migrate across a sea floor and precipitate Pb and Zn distally in localized biogenic H 2 S-bearing deeps. By this means, or by slightly increasing the exhaled H 2 S concentration, Pb-Zn-rich iron oxide ores with greater Pb-Zn contents could be produced, mineralogically transitional between volcanic copper-bearing oxide Cu-Au banded iron-formation and Broken Hill-Pegmont-style Pb-Zn banded iron-formation ores.

Estudio de inclusiones fluidas de las mineralizaciones epitermales de Ag.Baritina.metales de base de Hiendelaencina y de Baritina de Atienza (Sistema Central Español)

Fluid inclusion studies on quartz and barite samples from the Hiendelaencina Ag-base metals epithermal deposit (late Hercynian) suggest that this mineralization was formed during four hydrothermal stages. Ore stage I was characterized by aqueous-carbonic fluids from which pyrite and arsenopyrite were precipitated. The interaction between probably magmatic-derived fluids (aqueous solutions; Th = 320 – 200o C, 12 eq. wt. % NaCl) and meteoric waters (of lower temperature and salinity) caused a generalized decrease in both, T and salinity (from 12 eq. wt. % NaCl to 3 eq. wt. % NaCl), thus probably inducing the precipitation of Cu and Zn minerals (ore stage 11). Ore stage 111 (silver stage) was characterized by the interaction between fluids of low temperature and contrasted salinities (Th = 100 – 150o C; 3 eq. wt. % NaCl to 18-22 eq. wt. % NaCl). A final and «barren stage » (stage IV) resulted in the precipitation of a late generation of quartz and barite.

Analysis of 2D and 3D defects associated with precipitation of Cu in silicon

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.

Interface analysis of Y-Ba-Cu-O films on Al-coated Si substrates

Y-Ba-Cu-O films were deposited on Al-coated Si substrates by the plasma-spray method. The Al buffer layer appears to be effective in yielding crack-free adhesive Y-Ba-Cu-O films. Resistance measurements indicate that the films exhibit a superconducting phase below 90 K. Results of x-ray microanalysis and x-ray photoelectron spectroscopy confirm that the Al buffer forms an Al2O3 layer and prevents precipitation of Cu at the film/substrate interface.

Atomic growth mechanisms for lamellar structures

The pearlite transformation product is composed of alternating plates resulting from a eutectoid transformation whereas the discontinuous or cellular transformation is also composed of alternating plates due to relief of supersaturation. This paper will describe the relationship between the growth interface and interlamellar structure that results from the pearlite and cellular structures. Some important similarities will be noted that relate to both types of phase transformations.The Cu—4w/o Ti alloy was made by induction melting high purity materials and homogenizing. Samples were then solutionized at 900 C and isothermally transformed at 740 C for 60 m. Details of the experimental procedure for the Fe—.8w/o C—12 w/o Mn alloy are given elsewhere.Cellular precipitation in Cu—Ti alloys consists of the synchronous growth of lamallae of less saturated fcc Cu and an ordered orthorhombic Cu4Ti β phase. The conjugate habit planes between the depleted matrix and β phase is (010)β//(111)α with [001]β//[110]α.

ChemInform Abstract: The Influence of Chloride Ions on the Stress Corrosion Cracking of Al‐Brass in Acidic Sulphate Solutions

Abstractis found to be either stimulating or inhibitive depending on the Cl‐ concentration, the pH and the Cu2+ content of the electrolyte.

Thermometric titration of several transition metal ions with sodium diethyldithiocarbamate.

The reactions of copper(II), nickel(II), lead(II), cadmium(II), zinc(II), silver(I) and thallium(I) ions with sodium diethyldithiocarbamate (DDTC) were examined by thermometric titration for the determination of these metal ions. The divalent metal ions reacted with DDTC in a molar ratio of 1 : 2 and monovalent thallium ion reacted in that of 1 : 1. But the titration of silver(I) ion exhibited a nonstoichiometric end point before the equivalence point. The divalent metal ions in the range of 40120 μmol can be determined within 1% error in acetate buffer solution at pH 5.0. The heats of precipitation of Cu(II)-, Ni(II)-, Pb(II)-, Cd(II)- and Zn(II)-DDTC were measured.

Kinetics of cellular dissolution in a CuIn alloy

The dissolution of lamellar precipitates by cell boundary migration has been studied in a Cu-15 wt.% In alloy in the temperature range 778–853 K, primarily by optical microscopy. Microstructural observations indicated that the process of dissolution in this alloy is a cellular mode of transformation. By approximating the tip radius at the α-δ interface as equal to half the width of a δ lamella, the interface composition during dissolution was determined using the Gibbs-Thomson relation. The boundary diffusivities were calculated using the theories of Tu and Turnbull and of Petermann and Hornbogen modified for dissolution and a formulation applying balance of fluxes at the edge of a receding cell boundary similar to the formulation of Aaronson and Liu for the cellular precipitation reaction. The diffusivity values calculated from the experimental data fall within a range of two orders of magnitude for these theories but in all cases are four to five orders of magnitude higher than the volume diffusivity. For this alloy, there exists a critical temperature at which the driving forces for cellular precipitation and dissolution are equal. The value lies approximately 23 K below the equilibrium solvus temperature. An activation energy in the range 148–159 kJ mol −1 for different models has been obtained which agrees well with the Q values reported for cellular precipitation in CuIn alloys.

Extrinsic gettering via the controlled introduction of misfit dislocations

As an alternative to existing gettering techniques, extrinsic gettering by misfit dislocations is described and gettering efficiency evaluated. Uniform arrays of misfit dislocations were generated at epitaxial Si interfaces by incorporation of 0.1–1% of Ge. The dislocations were shown to be confined to the interface by means of optical and electron microscopies. The misfit dislocations were used as extrinsic gettering sinks for metallic impurities deliberately introduced and diffused towards the dislocations. Transmission electron microscopy and secondary ion mass spectrometry analyses showed the preferential precipitation of Cu and Au at the misfit dislocations.

Chemisorption of Copper on Hydroxy-Aluminum-Hectorite: An Electron Spin Resonance Study

Copper adsorption on a hydroxy-aluminum-hectorite complex (OH-Al-hectorite) at pH 4.5, 5.7, 7.4, and 7.8 was examined by means of electron spin resonance. The spectra of these samples were compared to those of Cu2+-hectorite and various aluminum hydrous oxides. Copper on the OH-A1- hectorite in aqueous gels occurred as mobile Cu(HzO)62§ and chemisorbed to discrete sites of the OH-A1 interlayer. As pH was increased, the ratio of chemisorbed to mobile Cu 2§ increased. At pHs above 7 the solubility product of Cu(OH)2 was exceeded, but chemisorbed Cu 2§ remained as the dominant species. These results contrast with the precipitation of Cu observed on microcrystaUine gibbsite above pH 5 and indicate that the interlayer OH-AI retained more Cu 2§ on discrete sites. The greater adsorption capacity probably resulted in part from a higher specific surface area. Electron spin resonance spectra of Cu 2§ in air-dried films of the OH-Al-hectorite at pH 4.5 and 7.4 showed Cu 2§ in square planar symmetry, oriented with the z-axis perpendicular to the OH-Al-hectorite a-b plane. At the higher pH, the spectrum resembled that of Cu(OH)4 :- on alumina, suggesting a ligand exchange mechanism for Cu 2~ adsorption on the complex.

Binding of cadmium and copper(II) ions to oligogalacturonic acids

The binding of Cu2+ and Cd2+ ions to potassium oligogalacturonates of polymerization degree DP 1 to 9 was investigated by ion-specific electrodes and by the metallochromic indicator method. The interaction was evaluated on the basis of degree of association β of cations (M2+) with carboxyl groups of the compounds examined and the single-ion activity coefficients of counterions γM2+. The results were compared with values corresponding to an electrostatic bond of Ca2+ ions to these oligomers. The Cd2+, and especially Cu2+ ions were bound in a considerable measure already to mono- and oligogalacturonates of a low polymerization degree very probably by a chelate bond. Precipitation of Cu- and Cd-oligogalacturonates takes place at a polymerization degree DP 5 and 8, respectively. Interpretation of results by the multiple equilibria theory evidenced that the Cu2+ ions were stoichiometrically bound to mono- and oligogalacturonates (one cation to two carboxyl groups) similarly, as with polymeric D-galacturonan. The results revise the early conception concerning the formation of a positively charged complex of Cu2+ ions (similarly also of Cd2+ and Pb2+ ions) with monogalacturonic acid of (MA)+ type, where A- is the anion of uronic acid. The results are a contribution to the elucidation of the elimination mechanism of these toxic cations from human body involving the oligomeric fragments of pectin as products of its enzymic degradation in the digestive tract.

Notes. Activation of dioxygen and catalytic oxidation of ethanol to acetaldehyde and hydrogen peroxide by copper(I) complexes containing 2,2′-bipyridyl and tertiary phosphine ligands

Reactions of [Cu(bipy)Ll](bipy = 2,2′-bipyridyl; L = PPh3, PMePh2, PBun3, or PEt3) with O2 alone in dimethylformamide and SO2 plus O2 in dichloromethane lead to the formation of [Cu2(bipy)2(OH)2]l2 and precipitation of Cu[SO4]. The complex [Cu(bipy)Ll] catalyses the oxidation of ethanol by dioxygen to acetaldehyde and H2O2 in the presence of equimolar quantities of Na[OC2H5]. Added phosphine acts as a strong inhibitor and the catalytic decomposition of H2O2 by the complexes leads to their deactivation. A tentative reaction mechanism is discussed.

Enhanced diffusion and precipitation in Cu: In alloys due to low energy ion bombardment

The effects of low energy Ar + ion bombardment on supersaturated Cu: 10at%-In alloys at room temperature were investigated using scanning transmission electron microscopy and Auger electron spectroscopy. Both 1 and 3 keV Ar + bombardment resulted in the preferential sputter removal of In. The surface and altered layer remained supersaturated however, and ion bombardment enhanced diffusion was sufficient to allow the precipitation of In-rich δ-phase (~30 at% In) particles in the near-surface region. The average precipitate size and number density in samples bombarded with 3 keV Ar + ions were ~200 Å and 10 10 cm −2 as compared to 150 A and 10 9 cm −2 in samples bombarded at 1 keV. The ion bombardment induced precipitates nucleated within the grains rather than, as was observed for thermally induced precipitates, at grain boundaries.

Enhanced diffusion and precipitation in Cu : In alloys due to low energy ion bombardment

Enhanced diffusion and precipitation in Cu : In alloys due to low energy ion bombardment

1 : 2 : 4-triazole as a corrosion inhibitor for copper

The solution chemistry of 1 : 2 : 4-triazole ( TRZ) is investigated in the range of solution concentrations in which the compound acts as a corrosion inhibitor for copper. Parallel photo-electron spectroscopic studies show that although a surface layer of Cu(I) complex is formed at low TRZ concentrations, this is ineffective as an inhibitor until at a critical concentration a Cu(II) complex appears which provides effective protection. It is suggested that the precipitation of Cu(II) hydroxychloride is which the TRZ is attached provides the protective layer. Comparison is made between triazole and benztriazole as corrosion inhibitors for copper.

The effect of Ni on the decomposition of austenite in Fe-Cu alloys

This paper is concerned with the effect of ternary additions of Ni on the decomposition of austenite in Fe-Cu alloys. It is shown that the transformation kinetics, transformation structures and associated precipitate morphologies are sensitive functions of the Ni content. Specifically the results show that the addition of nickel increases the transformation times and also leads to a change in resultant ferrite morphology from equiaxed to Widmanstatten, with a concomitant increase in the partially coherent interphase boundary growth mode. The increase in transformation time allows precipitation of Cu to occur on the interphase boundary and in the matrix. It is also shown that the exact details of the ∈-Cu dispersion is controlled both by the nature of the austenite/ferrite interface and the kinetics of the transformation.

Thermodynamics of Copper-Oxygen System Dissolved in a Glass—Relation to Copper Ruby Formation

The Cu2O(glass)-Cu(glass) equilibrium was studied in 25Na2O, 10Al2O3, 65B2Os glass at varied partial pressures of oxygen (pO2=10−12 to 10−17 atmosphere) and temperatures in contact with solid metallic copper. On heat-treatment, the best ruby was formed in glass melted at pO2=10−14 atmosphere, at higher pO2's no ruby colour developed, and at pO2 ≤10−15 atmosphere the glass produced progressively poorer rubies. Using the thermodynamic data estimated for the Cu2O(glass)-Cu(glass) system, possibilities for the precipitation of Cu (solid) and Cu2O (solid) are discussed. It is concluded that Cu2O (solid) is primarily responsible for the bright red ruby colour in this glass.

Reaction Products between Phosphoryl Triamide and Some Transition Metal Chlorides in Aqueous Solution

The reactions between phosphoryl triamide and MCl2 {M = Mn(II), Co(II), Cu(II) (as trace nutrient)} in aqueous solutions were studied, and the products were examined by chemical analysis, ion-exchange chromatography, paper chromatography, X-ray powder diffraction method, IR spectroscopy, etc.M {PO(NH2)3}2Cl2(M = Mn(II), Co(II)) complexes that contained a small amount of diamidophosphate (6-11%) were obtained by adding acetone to the mixture of MCl2(M = Mn, Co) and PO(NH2)3 (P/M atomic ratio 1.5-2.0) at room temperature. On the other hand, PO(NH2)3 was hydrolyzed rapidly in the initial stage of its reaction with Cu(II), resulting in a precipitation of Cu(II) phosphates. Further, when a solid mixture of PO(NH2)3 and MCl2(M = Mn(II), Co(II)) with a molar ratio of 2:1 was dried in a vacuum desiccator after it had been wetted with a small amount of water and mixed thoroughly, it also yielded M{PO(NH2)3}2Cl2 complexes as major constituent.In the reaction of PO(NH2)3 with MCl2(M = Mn(II), Co(II), Cu(II), though it was hydrolyzed as the reaction time became longer (-72hr) and at higher temperature (-60°C), metal salts were precipitated that consisted of mainly amidophosphate, orthophosphate and diphosphate. The percentage of diphosphate in the hydrolysis products were 27%, 33% and 25% for Mn(II), Co(II) and Cu(II), respectively.The hydrolysis process of PO(NH2)3 in the reaction with MCl2 is discussed.