Copper Inclusions Research Articles

Copper and Tenorite Inclusions in Cuprian-Elbaite Tourmaline from Paraíba, Brazil

Copper and Tenorite Inclusions in Cuprian-Elbaite Tourmaline from Paraíba, Brazil

Ultrasonic backscattering from solid cylindrical inclusions in solid elastic matrices: A comparison of theory and experiment

The problem of ultrasonic backscattering of longitudinal and shear waves normally incident on a solid cylindrical scatterer embedded in a solid matrix is studied both theoretically and experimentally. Calculations of the backscatter form function, f∞(θ,ka), as a function of ka are compared in the range 2.0<ka<9.0 with experimental measurements (using a short pulse-echo technique) in the same range for both copper and steel inclusions embedded in an epoxy matrix. The results show very good agreement between theory and experiment highlighting NDE and material characterization applications.

Origin and mode of copper enrichment in biotite from rocks associated with porphyry copper deposits; a transmission electron microscopy investigation

This paper presents results of a systematic transmission electron microscopy (TEM) study of biotites from a suite of core samples from the Cyprus Casa Grande porphyry copper deposit, Arizona. The primary purpose of this study was to determine the mode and timing of copper enrichment in biotite and to compare the results to TEM observations of biotites from other porphyry copper deposits. The core samples represent both oxidized and unoxidized rock. Biotites and chlorites from unoxidized protore contain less than 200 ppm copper as measured by electron microprobe and are free of copper-enriched expanded interlayers and the native copper inclusions described by Ilton and Veblen (1988); biotites and chlorites from oxidized ore are commonly copper enriched. The mode of copper incorporation in biotites and chlorites in oxidized rock is complex and varies with depth. Biotites from the goethite zone contain submicroscopic native copper inclusions and both copper-enriched expanded interlayers and submicroscopic iron oxide inclusions. Biotites and chlorites from the chrysocolla zone contain copper-enriched expanded interlayers, amorphous Al-Si intergrowths with dense arrays of copper- and iron-rich inclusions, and copper-rich inclusions that rapidly evaporate under the electron beam and hence have yet to be identified. It is possible that copper is incorporated into the brucite layer in chlorite. Biotites from the native copper zone contain native copper inclusions, as expected, but they also contain copper-rich expanded interlayers. Biotites associated with atacamite mineralization contain high concentrations of copper that are associated with expanded interlayers. In the chalcocite zone, biotites appear relatively unweathered and contain minor concentrations of copper that are associated with infrequent expanded interlayers.A comparison of observations from oxidized and unoxidized rock indicates that the occurrence of copper-rich biotites and both copper-enriched expanded interlayers and native copper inclusions in biotite are restricted to oxidized rock. We conclude that the native copper inclusions and copper-rich expanded interlayers in biotite from Cyprus Casa Grande formed during weathering and not during the hydrothermal event.Native copper inclusions and copper-rich expanded interlayers in biotites have been documented from a variety of porphyry copper deposits. Earlier studies of the same samples have suggested that copper in copper-rich biotites was representative of magmatic hydrothermal events and that the difference between mineralizing and barren intrusions was recorded by differences in copper concentrations in biotite. The present study, together with previous experimental work, suggests that the copper-rich biotites became copper enriched during weathering and that copper concentrations in copper-rich biotites do not reflect magmatic hydrothermal processes.

A model of the cathode spot glow discharge for a cathode with inclusions of low work function material

A model that describes the self-maintained glow discharge for a composite cathode in which cathode spots are formed on low work function material inclusions is presented. Based on this model, expressions are obtained for the radius of the spot, the cathode voltage, and the spot current as functions of Pd (where P is the gas pressure and d is the thickness of the cathode layer), the parameters of the inclusions, and the basic material matrix are obtained. Numerical results for the case of a glow discharge in 75 torr neon gas with a copper cathode matrix and inclusions of LaB/sub 6/ are presented. The average radii of inclusions were 0.05 and 0.015 mm. Conditions under which the glow discharge migrates from the inclusions and begins to spread onto the surface of the basic matrix are obtained. The transition of the glow discharge into a contracted state, depending on the structure of the composite material, is also considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reaction of some trioctahedral micas with copper sulfate solutions at 25 degrees C and 1 atmosphere; an electron microprobe and TEM investigation

Reaction of biotite and phlogopite with acidic, CuSO 4 -rich aqueous solutions at 25 degrees + or - 3 degrees C and 1 atm, produced submicroscopic inclusions of a copper-rich, sulfur-absent phase, identified by electron diffraction and analytical electron microscopy as native copper. The copper inclusions lie in the interlayer region of the mica and are associated with copper-enriched, expanded (hydrated) interlayers and potassium depletion. The inclusions, and associated biotite textures and compositions produced in the experiments, are similar to those documented in naturally occurring biotites from rocks associated with porphyry copper deposits (Ilton and Veblen, 1988). The experiments support the suggestion of Ilton and Veblen (1990, 1992) that this mode of copper enrichment in biotite is produced during weathering of rocks with copper sulfide mineralization, such as porphyry copper systems.Electron microprobe analyses of reacted micas show that phlogopite becomes more enriched in copper than biotite but that both phlogopite and biotite become enriched in silica relative to all other cations. A combination of transmission electron microscopy (TEM) observations and electron microprobe analyses indicates that copper is absorbed into the interlayer region of the micas where it exchanges for potassium. We propose that octahedrally coordinated ferrous iron reduces absorbed copper ions to metallic copper. It appears that biotite retains potassium more tenaciously than phlogopite. Higher fluorine concentrations in biotite relative to phlogopite may stabilize potassium in biotite relative to phlogopite. This, in turn, could explain why phlogopite appears to absorb copper more readily than biotite.The results of these experiments indicate that biotite may absorb copper during in situ and heap leach mining, which could result in lowered recoveries. This is relevant to research on in situ leach mining by the U.S. Bureau of Mines, Advanced Mining Division. Biotite in mine tailings and in other types of mine workings could also act as a copper sink, which would lower copper concentrations in acidic mine drainage from some mining regions.

Copper inclusions in sheet silicates from porphyry Cu deposits

Economic geologists have studied the Cu contents of biotite for at least a quarter of a century as potential guides for exploration and as clues to the genesis of porphyry copper deposits1–12. These earlier studies used bulk analytical techniques, and a common, although cautious, assumption was that Cu substituted for Fe in the octahedral sites of the biotite. Here we report data from high-resolution and X-ray analytical transmission electron microscopy which demonstrate that anomalous Cu in biotite is present primarily as submicrometre inclusions of pure native Cu in the interlayer regions of the mica. The inclusions occur with greatest density and size in mixed-layer sheet silicate domains which form by alteration of biotite and chlorite. Less abundant and smaller Cu inclusions are associated with biotites that show subtle alteration only on the high-resolution transmission electron microscopy scale. The association of Cu inclusions with alteration domains, coupled with mass-balance considerations, suggests that these sheet silicates act as Cu sinks, and not as sources for primary mineralization.

Modelling of degradation i n black copper photothermal collector coatings

The degradation mechanism in black copper photothermal collector coatings was investigated through the use of kinetic analysis, microstructural determinations and optical modelling. The initial structure of black copper was identified using reflection electron diffraction, scanning electron microscopy and Auger electron spectroscopy sputter profiles. These results were used to develop an optical model of the as-deposited coatings. In this model, the coatings was best described as a two-layer film. The layer next to the substrate consists of dense copper oxide with metallic copper inclusions, while the rough outer layer is modelled as copper oxide dispersed in air. A substantial decrease in the solar absorptance (from 0.96 to 0.80) of coatings exposed to temperatures above 150°C in air was found to occur within 30 min and was explained by a decrease in the surface roughness of the coatings. After longer exposures, an increase in the thickness of the oxide layer near the substrate occurs at the expense of the surface layer. Incorporating this change in the model, the optical properties after thermal ageing were predicted.

The Effect of Welding Cables on Production Schedules and Costs: A Case Study

A detailed study of present welding cable production/repair operations was performed in an attempt to reduce the costs associated with production downtime due to defective manual arc welding cable resulting from copper inclusions in the cable and connectors. The paper discusses surveys used to obtain information from 14 commercial and naval shipyards concerning their present methods of manufacturing/repairing and management of manual arc welding cable sections. The results of the surveys and shipyard visits are summarized. The paper presents a detailed analysis of the various welding cable connectors used by the 14 shipyards responding to the survey. The connectors were evaluated from the standpoints of automation potential and economic life. In regard to cable manufacture/repair and procedures, and the welding support organization, general management practices observed in various shipyards visited are reported. A few general comments on methods engineering aspects of the procedures involved in the manufacture/repair of cable sections are given. While welding cable may seem to be a trivial part of the production process, the mismanagement of this area can have a significant impact on production schedules and costs.

Coarsening of SiO2 particles in copper and MnS inclusions in steel

A model to simulate the diffusion-controlled coarsening and dissolution kinetics of particles within a metallic matrix is formulated. With an arbitrary size distribution of particles, the model can be used to calculate the change in the size distribution of particles during coarsening or dissolution. Other system parameters, such as average radius of particles, volume fraction, average distance between particles, surface area, and matrix composition are also calculated. An important result is that kinetics do not generally obey the often-applied Lifshiftz-Slyozov-Wagner theory for diffusion controlled coarsening based upon concentration profiles around isolated spheres. In such a formulation, the direct effect of the surrounding particles is neglected. In our model, which is a modification of the coarsening kinetics described by Weins and Cahn, the effect of surrounding particles is incorporated because the system is taken to be a system of point potentials, each with a potential according to its radius of curvature. Calculations are on silica particles in a copper matrix and on manganese sulfide inclusions in iron, with emphasis on the latter, in order to predict their behavior during homogenization or soaking treatments. The effect of the composition of manganese, from 0.1 to 1.2 wt pct, on the coarsening of sulfides in a “high” sulfur (0.017 wt pct) steel and a “low” sulfur (0.003 wt pct) steel was investigated. As expected, the model predicts that manganese strongly reduces the rate of coarsening, particularly for times of ten hours or less in the temperature range of 1100 to 1400 °C. Calculated results also indicate that the rate of dissolution is very low at temperatures greater than the solvus for manganese sulfide inclusions in austenite.

Optical absorption of Cu2O in the near infrared and the role of metallic inclusions

We have measured the optical absorption characteristics of copper oxide single crystals in the range from 1.1 to 2.0 eV. The crystals were annealed at various oxygen pressures at high temperatures and quenched to room temperature. A major, broad, previously unknown absorption peak was found at 1.6 eV which we relate to the formation of copper inclusions in the oxide. Although experimental data on thin copper films agree with our assumptions, we cannot reconcile our results with scattering theory of small metal spheres embedded in a dielectric. Agreement between scattering theory and optical absorption may be achieved for nonspherical particles for which as yet no other experimental evidence exists.

The thermal conductivity of fibre-reinforced concrete

The effect of copper and steel fibre inclusions on the thermal conductivity of mortar and concrete is investigated. The experimental technique is based on the conventional steady-state method using desiccated specimens. The results indicate that copper fibres significantly increase thermal conductivity while steel fibres have a lesser effect. Vibration of the fresh concrete, during specimen manufacture, produces some fibre alignment. As a result, it is found that theoretical methods based on the assumption of a random fibre distribution under-estimate the experimental values.

Some Rationale for the Unusual Behavior of the Dielectric Constant of Cu2O

The very low frequency dielectric constant in Cu2O varies over wide limits and is highly temperature dependent. At sufficiently low temperatures the dielectric constant for all samples reduces to the high frequency value of about 7.5. Small variations in the high frequency value are easily explained as being due to the known presence of copper crystals embedded in the semiconducting material. The low frequency and temperature variations will be related to the variation in the depletion layer formed around each copper inclusion. Calculations are based on highly oversimplified size, shape, and distribution of the copper inclusions.

Theory and technique of manufacture of electrode-tool materials for electroerosion machining

In the earlier parts of this investigation [1-3], an examination was made of the electroerosion wear of cathode and anode materials and a description was given of a technique for the manufacture of new composite materials of increased erosion resistance. In the present work, a study was made of the structure of composite alloys based on scrap of VK alloys (WC + Co) with copper, nickel, and boron nitride additions. Test specimens, made in the form of electrode tools for electroerosion machining, were subjected to microstructural analysis at magnifications of 100-1150 diameters (optical microscopy) or higher (electron microscopy). Mierosections were examined both before and after etching. Examination of the results obtained shows that the number and size of copper inclusions in WC- Co - Cu alloys increase with rise in copper content of the materials (Fig. la and b). It is interesting to note that the distribution of copper inclusions is nonuniform in specimens obtained by mechanical mixing of charge components, the degree of this nonuniformity increasing with rising copper concentration in the materials (Fig. lb). Figure l c shows the microstructure of a synthetic alloy obtained from hard alloy scrap with a copper addition. Together with the usual structural constituents of hard alloys - tungsten carbide