Copper Matrices Research Articles

Heat Sink Materials Processing by Pulse Plasma Sintering

A Pulse Plasma Sintering (PPS) process was employed to manufacture Cu-diamond composites with a 50% volume fraction of each constituent. Pure and Cr (0.8wt.%) alloyed copper matrices were used and commercial diamond powders. The composites were sintered at temperature of 900°C for 20 min and under pressure of 60 MPa. In these sintering conditions diamond becomes thermodynamically unstable. Cu0.8Cr-diamond and Cu-diamond composites with relative densities of 99,7% and 96% respectively were obtained. The thermal conductivity of Cu0.8Cr-diamond composite is equal to 640 W(mK)-1 whereas that of Cu-diamond is 200 W(mK)-1. The high thermal conductivity and relative density of Cu0.8Cr-diamond composite is due to the formation of a thin chromium carbide layer at the Cu-diamond interface.

Spin-dependent transport in cluster-assembled nanostructures: influence of cluster size and matrix material

Spin-dependent transport in granular metallic nanostructures has been investigated by means of a thermoelectric measurement. Cobalt clusters of well-defined size ( = 15 and 600), embedded in copper and silver matrices, show magnetic field responses of up to several hundred percent at low temperature. The experimental observations are identified as due to spin mixing. The influence of cluster size and matrix are discussed.

Monodispersed metal clusters in solid matrices: A new experimental setup

We describe a new experimental setup for the production of samples of metal clusters embedded in matrices stable at ambient conditions. The cluster ions are generated in the gas phase and codeposited fragmentation-free together with the evaporated matrix. Mean cluster sizes range from a few to many thousands of atoms. For small clusters (n<20) mass selection is possible; larger clusters are deposited in narrow size distributions. Matrix materials include metals (Cu and Ag) and oxides such as quartz. The performance of the apparatus as well as sample characterization procedures are described. We show first results on the magnetic properties of different cobalt cluster size distributions (⟨n⟩=15,600,2300,6500) embedded in copper matrices, demonstrating intercluster as well as cluster-lattice interactions.

Coprecipitation with yttrium phosphate as a separation technique for iron(III), lead, and bismuth from cobalt, nickel, and copper matrices

The coprecipitation behavior of 44 elements (47 ions because of chromium(III,VI), arsenic(III,V), and antimony(III,V)) with yttrium phosphate was investigated at various pHs. Yttrium phosphate could quantitatively coprecipitate iron(III), lead, bismuth, and indium over a wide pH range; however, 18 ions, including alkali metals and oxo anions, such as vanadium(V), chromium(VI), molybdenum(VI), tungsten(VI), germanium(IV), arsenic(III,V), selenium(IV), and tellurium(VI), were scarcely collected. In addition, 19 ions, including cobalt, nickel, and copper(II), were hardly coprecipitated at pHs below about 3. Based on these results, the separation of iron(III), lead, and bismuth from cobalt, nickel, and copper(II) matrices was investigated. Iron(III), lead, and bismuth ranging from 0.5 to 25 μg could be separated effectively from a solution containing 0.5 g of cobalt, nickel, or copper at pH 3.0. The separated iron(III), lead, and bismuth could be determined by inductively coupled plasma atomic emission spectrometry using internal standardization. The detection limits (3σ, n = 7) of iron(III), lead, and bismuth were 0.008, 0.137, and 0.073 μg, respectively. The proposed method was applied to the analyses of metals and chlorides of cobalt, nickel, and copper.

Formation and Critical Shear Stresses of Prismatic Dislocation Loops Observed around Spherical Precipitate in Single Crystalline Aluminum and Copper Matrices (Simulations by Molecular Dynamics)

Prismatic dislocation loops have so far been observed around the misfitting particle embedded in the matrix. They are generated from the precipitate-matrix interface on which the local shear stress in the maximum. In the present study, the dislocation emissions and the subsequent formation of the prismatic dislocation loop around the inclusion embedded in the single crystalline aluminum or copper matrix are simulated by molecular dynamics. At a result, the maximum shear stress occurs at the precipitate-matrix interface on the {1 1 1} plane intersecting the spherical precipitate at the height of Rp/√2. Afterwards, the prismatic dislocation loops, which have the same gliding direction but not on the same slip planes, are attained by energetically unstable interactions around the precipitate. The representative size of the prismatic dislocation loop is found to depend on the diameter of the precipitate.

Absolute methods of quantitation in glow discharge mass spectrometry with a time-of-flight mass analyzer

Several absolute quantitation strategies have been evaluated for multielemental analysis in glow discharge mass spectrometry. A method for standardless analysis is described that offers accuracy within an order of magnitude, without relying on any calibration factors or internal standards. However, the accuracy of this method can be improved by two- to four-fold through use of relative sensitivity factors (RSFs). These factors, determined from a global set of standards that included iron, nickel, cobalt, and copper matrices, were fairly independent of the matrix. Similar results were obtained using RSFs from the global set, RSFs from standards with a similar matrix, and RSFs from a single standard. When RSFs were employed, experimental results were determined with a mean accuracy of 5–12% for analyte concentrations greater than 1%.

Copper Electroplating from Vanadate- and Molybdate-Containing Electrolytes with Suspended Titanium Dioxide

Coatings with copper matrices, which are deposited from sulfate electrolytes modified by additions of either molybdate or vanadate ions and highly dispersed powder of titanium dioxide, are studied. The additives enhance the heat resistance of the coatings. The mentioned ions have a depolarizing effect on the cathodic deposition of copper and inhibit the codeposition of a dispersed phase of TiO2 . Molybdate ions in certain concentrations improve the brightness of the coatings, having been reduced to Mo compounds of lower oxidation degrees. The effect of the mentioned ions on the pH s during the copper deposition is studied. The pH of the near-cathode layer is shown to somewhat increase in the presence of both molybdate ions and titanium dioxide.

Extraction and recovery of cadmium using Cyanex 923

Studies have been carried out in the extraction of Cd(II) along with Al(III), Fe(III), In(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Hg(II) and Pb(II) from hydrochloric acid medium using Cyanex 923. The effect of different variables influencing the extraction of Cd(II) such as the concentration of acid, metal ion and extractant and the nature of the diluent has been investigated. The extracting species of Cd(II) is proposed. Based on the partition data, some binary separations of topical interest from Cd(II) have been achieved. The potential of the extractant for the recovery of pure cadmium from some zinc and copper matrices is assessed.

Ordered Monolayer Overstructures Formed on Cu Surfaces Through Segregation

The segregation kinetics of the metal dopants Sn, Sb and Ag in copper matrices were determined for three different low index orientations. In the Cu(Sn) and Cu(Sb) systems ordered submonolayer coverages were obtained following a t 1/2 dependence close to equilibrium values. The kinetics were found to be more complex in the case of Cu(Ag). where a relative high self interaction parameter led to a two step kinetic process. The diffusion parameters were determined in all cases by the appropriate Darken model fits and the results do suggest an orientation dependence of the diffusion coefficient D in the near surface region.

ICP–AES determination of small amounts of zinc in copper-base alloys after separation by adsorption of the zinc–TAN complex on Sep Pak C18 cartridges

The use of ICP/AES for the determination of zinc, in low concentration levels, in matrices containing high levels of copper is difficult because copper interferes in the zinc main emission wavelength (213.856 nm). In the present work, a separation of zinc from copper matrices was possible, using the reaction of zinc(II) cation with 1-(2-tiazolylazo)-2-naphthol (TAN), in the pH range of 6.5–8.0, resulting in a stable red complex. Copper also reacts with TAN but its interference was avoided by the addition of ascorbic acid and thiosulphate in the reaction medium. In this way, the aqueous solution was passed through a SEP PAK C18 cartridge, in which the zinc(II)–TAN complex was quantitatively retained, but it did not occur with copper which passes through the cartridge, as [Cu2(S2O3)2]2−, with the aqueous solution. The cartridge was washed with water and the complex eluted with ethanol. Then, the alcohol was evaporated and the complex decomposed by nitric acid. It results in both zinc pre-concentration and separation from copper. The zinc quantification was carried out by ICP/AES at 213.856 nm. The relative standard deviations, for ten different aliquots, were 5.7% and the average recovery found for zinc was 96%, even when the concentration ratio Cu/Zn was up to 500/1 (mg l−1:mg l−1). Other metals, like nickel, for example, can react with TAN in the same way as zinc but they do not interfere in the emission wavelength 213.856 nm.

Pressure infiltration casting of metal matrix composites

Pressure infiltration casting ∗ ∗ Pressure infiltration casting technologies are patent pending processes. is a unique form of liquid infiltration which utilizes pressurized inert gas to force liquid metal into a preform of reinforcement material. The methods and equipment used for pressure infiltration casting allow for inexpensive development of composite materials, prototypes, and net-shape component production. Pressure infiltration casting's use of an enclosed die chamber with controlled pressurization makes it possible to cast in low strength molds with high infiltration pressures. The development of a number of solidification systems has enabled parts to be infiltrated and directionally solidified, producing high quality composites. The basic principles behind pressure infiltration casting and its history will be discussed in this paper. Results of research in different methods for casting composites will also be presented. These methods include: 1. (1) top fill casting-liquid metal is forced downward by a pressurized gas into a preform; 2. (2) bottom fill casting-liquid metal is forced up a fill tube into a preform by pressurized gas acting on the surface of a melt; 3. (3) top pour casting-a method developed for infiltration of high temperature alloys where the reinforcement and melt must be prevented from reacting. The methods and apparatus illustrated include sample components with aluminum and copper matrices, their microstructures, and tolerancing for net shape component production.

Thermal expansion of graphite fiber-reinforced metals

The presence of graphite fibers in metal matrices greatly influences the properties of the composites. Graphite fibers have been used in conjunction with aluminum, magnesium, and copper matrices. The type of graphite fiber, layup of the fiber, and volume percentage of the fibers are all important parameters in controlling the properties of the composites. The present status, particularly in the case of graphite/copper, can be considered to be the original developmental stage and is definitely far-removed from a matured technology. The present paper focuses on thermal expansion behavior of several graphite-metal matrix composites from −60 to +200°C.

EXPLOSIVE PROCESSING OF BULK SUPERCONDUCTORS

ABSTRACT This paper describes the explosive fabrication of novel, bulk superconducting composites and monolithic prototypes which serve to explore a range of applications including superconducting tapes, two-terminal linear bus structures for solid-state switching applications, and planar arrays for microwave antenna and magnetic shielding. The systems explored include copper and silver matrices encapsulating Yba2Cu3O7 superconducting powder and metal powder mixtures (Cu and Ag), Bi7Pb3Sr10Ca10Cu15O7 in copper, and Y-Ba-Cu-O and Bi-Pb-Sr-Ca-Cu-O in copper/silver/6061 -T6 aluminum alloy composites. The optimization of the powder consolidation and metal-matrix welding as well as shock-pressure induced alterations in residual superconductivity are examined by measuring bulk resistance versus temperature (R-T) and microwave surface resistances, relative susceptibilities, and relative levitation heights (as an indication of magnetic flux exclusion) with peak shock wave pressures which characterize the explosiv...

Squeeze Cast Metal Matrix Composites: Evaluation of Their Strength, Damping Capacity and Corrosion Resistance

Several graphite fiber reinforced (planar random) metal matrix composites employing copper, aluminum, tin and babbitt matrices were fabricated by a newly devel oped high-pressure squeeze casting method. The fiber volume fraction of these composites ranged from 5 to 55%. These composites had relatively weak fiber-to-matrix bonding because of the near-absence of interfacial reaction between fiber and matrix materials. The tensile strength of these composites increased with fiber volume fraction up to about 25% followed by a gradual decrease for higher fiber volume fractions. Experiments were designed to evaluate various mechanical and physical properties of high pressure squeeze cast composites including the damping capacity and corrosion re sistance. Measurements of logarithmic decrement values at reasonant frequencies on can tilevered beam specimens have demonstrated that the damping capacity of the composites is much superior to that of wrought 6061-T6 Al and mechanically alloyed aluminum. Results on corrosion resistance of the composites in distilled water and 3.5% NaCl solu tion over a range of voltages and temperatures are presented and discussed.

Interfacial phenomena and microstructural connectivity in explosively fabricated Y-Ba-Cu-O superconductors

Measurements of supercurrent transport and current density in explosively fabricated superconducting prototypes have been erratic, with current densities measured to be in excess of 103 A/cm2. This erratic behavior appears to be related to the degree of consolidation achieved for Y-Ba-Cu-O powders and, more specifically, to the connectivity or interfacial structure at individual, contacting, superconducting particles. We have used SEM and TEM to characterize and illustrate some of these features in preliminary superconducting prototypes composed of Y-Ba-Cu-O powder channels consolidated and encapsulated in copper and aluminum matrices by explosively generated shock waves. Observations of grain boundaries and interface phase regions cast some light on the prospects for producing good connectivity through optimizing the consolidation process and process parameters as well as the elimination of surface reactions on particles prior to consolidation, or thermal effects during consolidation.

Shock-compression fabrication of high-temperature superconductor/ metal composite monoliths

In spite of the recent spectacular achievements in developing high-temperature (transition temperature Tc ≥ 77 K) superconductivity in systems generically represented by ABa2Cu3O7–x (where A = Y, La, Nd, Sm, Eu, Gd, Ho, Er, Lu)1,2, it has been difficult to prepare large powder sample batches (≥0.5 kg). More importantly, efforts to consolidate or sinter superconducting powder samples or to place powders (such as Y–Ba–Cu–O) in useful environments or monolithic structures which are not brittle and friable, and the fabrication of high-temperature superconducting products have been frustrating at best3. Based on the process integration of several fundamental principles involving shock-compression science4,5, we have successfully fabricated composite/laminate monoliths containing shock-compacted, consolidated and bonded Y–Ba–Cu–O superconducting powder channels (with Tc≥90K) in a solid copper matrix6. Using ammonium-nitrate-based explosives (with detonation velocities, VD, adjusted to be ∼1,800 m s–1), we have progressed from shock-consolidated, superconducting YBa2Cu3O7 powder-channel rings with mean diameters of 4.4cm and 4mm2 cross-sections in explosively (implosive shock-wave) clad solid copper matrices, to monoliths from which copper matrix rings have been cut containing shock-consolidated, superconducting YBa2Cu3O7 powder channels with mean diameters of 24 cm (with 2.5 cm width) and cross-sections of 1.85cm2.

Ｃｕ‐Ｔｉ‐Ｂ合金の反応焼結

Reaction-sintering of Cu-Ti-B alloys was investigated by heating the mixed powder compacts prepared from copper powder, TiH2 or Cu-Ti alloy powder, and boron powder at temperatures higher than the melting point of Cu.Cu-TiB2 two-phase alloys were obtained by sintering when the atomic ratio Ti: B in the green compacts was adjusted to 1 : 2 regardless the choice of raw powders.In the case of sintering the powder compacts prepared by the use of coarse boron powder of about 150 μm in particle size, thin fiber type TiB2, and thin and long needle type TiB2 crystals were precipitated in the copper matrices at the respective sintering temperatures of 1373K and 1473K.

The use of compacted metal discs to measure Raman spectra

AbstractCompacted discs prepared from a mixture of finely divided particles of a compound diluted in a large excess of metal powder facilitate the measurement of Raman spectra for some compounds which give poor scattering by conventional techniques. The method is most useful with coloured compounds. The advantages include simplicity, increased signal‐to‐noise ratio by factors of up to 1000 and decreased or altered fluorescence. The effect appears to be caused mainly by small crevices in the compacted metal surface which act as internal mirrors to produce many small multiple‐reflection cells, but there is also evidence of an electronic interaction with the metal surface. Silver, aluminium and copper matrices were studied, silver being found to be the most advantageous, although aluminium under certain conditions may also be effective.

Impurity diffusion constants and vacancy–impurity binding energies in solids

Activation energies for impurity diffusion in solids are discussed. New approaches based on elasticity are outlined to predict values of activation energy from the atomic size, surface energy, and elastic modulus of the matrix and impurity. The activation energy for self-diffusion in the matrix must also be known. It is shown that reasonable agreement between the theoretical and experimental values of activation energy are obtained for copper, aluminium, nickel, and iron matrices. The elastic strain energy model is extended to facilitate predictions of vacancy–impurity binding energies. Again good agreement between experiment and theory is obtained, except in the case of aluminium matrices.MST/211

Impurity diffusion constants and vacancy–impurity binding energies in solids

Activation energies for impurity diffusion in solids are discussed. New approaches based on elasticity are outlined to predict values of activation energy from the atomic size, surface energy, and elastic modulus of the matrix and impurity. The activation energy for self-diffusion in the matrix must also be known. It is shown that reasonable agreement between the theoretical and experimental values of activation energy are obtained for copper, aluminium, nickel, and iron matrices. The elastic strain energy model is extended to facilitate predictions of vacancy–impurity binding energies. Again good agreement between experiment and theory is obtained, except in the case of aluminium matrices.MST/211