Particles Of Cu Research Articles

Investigations on the corrosion resistance and microhardness of Cu–10Sn/SiC composite manufactured by powder metallurgy process

In this work, Cu–10Sn/SiC composite has been manufactured using powder metallurgy method and its microhardness and corrosion resistance have been evaluated. For this, Cu–10Sn and SiC powders with various ratios were mixed, molded and sintered. Optical microscope, SEM and EDX were applied for study of SiC particles distribution in Cu–10Sn matrix and interfaces between them. Results of microhardness and electrochemical measurements revealed that incorporation of silicon carbide particles in Cu–Sn bronze matrix increase the microhardness and corrosion resistance and the composite containing 10 wt% SiC has the highest microhardness and corrosion resistance in 3.5 wt% NaCl solution. High hardness and chemical stability of SiC particles, perfect matrix/second phase particles interfaces and acceleration in protective layer nucleation and formation by incorporation of SiC particles in bronze matrix were recognized as the main reasons for these properties improvements. Above 10 wt%, incorporation of SiC particles lowers the microhardness and corrosion resistance due to the agglomeration of these particles and incomplete sintering of the specimens.

Mode-locked thulium doped fibre laser with copper thin film saturable absorber

ABSTRACTWe demonstrate the generation of mode-locked Thulium-Doped Fibre Laser by employing a newly developed saturable absorber (SA) based on copper (Cu) thin film. The SA was prepared by depositing nano-sized particles of Cu onto the surface of polyvinyl alcohol (PVA) film through the E-Beam evaporation process. A stable mode-locking pulse train operating at 1951 nm was successfully generated by introducing the Cu PVA SA into a laser cavity. The laser generated a pulse train at the fundamental frequency of 8.5 MHz with a calculated minimum pulse width of 14.8 ps. This demonstration proves that the Cu PVA based SA is suitable for generating mode-locked fibre laser at 2 µm region.

Dissolution of Ag Precipitates in the Cu⁻8wt.%Ag Alloy Deformed by High Pressure Torsion.

The aim of this work was to study the influence of severe plastic deformation (SPD) on the dissolution of silver particles in Cu–8wt.%Ag alloys. In order to obtain different morphologies of silver particles, samples were annealed at 400, 500 and 600 °C. Subsequently, the material was subjected to high pressure torsion (HPT) at room temperature. By means of scanning and transmission electron microscopy, as well as X-ray diffraction techniques, it was found that during SPD, the dissolution of second phase was strongly affected by the morphology and volume fraction of the precipitates in the initial state. Small, heterogeneous precipitates of irregular shape dissolved more easily than those of large size, round-shaped and uniform composition. It was also found that HPT led to the increase of solubility limit of silver in the copper matrix as the result of dissolution of the second phase. This unusual phase transition is discussed with respect to diffusion activation energy and mixing enthalpy of the alloying elements.

Transformation of Commercial TiO₂ into Anatase with Improved Activity of Fe, Cu and Cu-Fe Oxides Loaded TiO₂.

In the present study copper and iron oxides loaded TiO₂ catalysts are prepared by the deposition-precipitation method (DP) and the photocatalytic efficiency of these catalysts are tested for the degradation of Rose Bengal dye (Acid Red 94) under sunlight. The catalysts are characterized by XRD, TEM and UV-vis diffuse reflectance spectral analysis. It is interesting to note that the rutile form of commercial TiO₂ is competently converted into anatase after loading oxides of Cu, Fe and Cu-Fe on TiO₂ as evident from XRD analysis. This result is consistence with the result obtained in UV-vis diffuse reflectance spectra. TEM analysis confirms the nano particles of Cu and Fe deposited on TiO₂. Photocatalytic studies were performed in a batch reactor under solar radiation. Preliminary studies are performed to understand the photocatalytic degradability of the dye and optimization of catalyst weight and dye concentration. Kinetic studies were done at different dye concentrations and it was found that the rate equation followed first order kinetics and obeyed Langmuir-Hinshelwood model. The comparison of the activity of blank TiO₂, copper or/and iron oxides loaded TiO₂ catalysts showed that the Cu and Fe oxide loaded catalysts are more active than pure TiO₂ and also the Cu-Fe oxides co-loaded TiO₂ catalysts showed much best activity. The order of activity of the catalysts is in the following order: Cu-Fe/TiO₂ > Fe/TiO₂ > Cu/TiO₂ > TiO₂. The enhanced activity of metal oxide loaded TiO₂ is attributed to the presence of TiO₂ in anatase form after loading, which enhanced the charge transfer from the TiO₂ to adsorbed molecules for reaction.

Microstructure characterization and strengthening behavior of dual precipitation particles in Cu[sbnd]Ti microalloyed dual-phase steels

Copper particles that directly nucleated on the interphase precipitated TiC within the ferrite matrix were found in the CuTi bearing dual-Phase (DP) steel after a multistep heat treatment process. The formation of dual precipitates within ferrite grains should be considered a separated phase transformation process because only titanium carbides form initially when austenite undergoes decomposition reaction; subsequently, copper particles heterogeneously nucleate on these carbides.The above separated precipitation behavior leads to a gentle tempering behavior of CuTi microalloyed DP steel. For example, in Cu microalloyed DP steel, the changes in the average Vickers hardness of ferrite and martensite after 9 h of tempering treatment were 165 to 210 and 407 to 278, respectively. However, in the CuTi microalloyed DP steel, the average Vickers hardness of ferrite and martensite increased from 235 to 249 and 339 to 353, respectively, after 9 h of tempering.Fractography analysis revealed the mixed mode fracture characteristic due to the DP steel consisting of soft ferrite and hard martensite. However, fewer brittle-feature cleavage facets were found in the CuTi microalloyed DP steel after 5 h of tempering treatment, indicating the suppression of damage due to ferrite and martensite interface decohesion.

Variations in drag and heat transfer at a vertical plate due to steady flow of a colloidal suspension of nano particles in a base fluid

MHD mixed convection flow of colloidal suspension of nano particles of Cu, CuO, Al2O3, Ag and TiO2 at an isothermal vertical surface is analyzed numerically by local non similarity method. Base fluids are taken as water, ammonia, two refrigerants and transformer oil. Some of the important observations of the analysis are: the drag coefficient as well as heat transfer coefficient increase with increasing values of the axial distance and the Richardson number; skin friction diminishes and Nusselt number increases as the Prandtl number of the base fluid increases.

Coarsening behavior of (Ni, Co)2Si particles in Cu–Ni–Co–Si alloy during aging treatment

The coarsening behavior of (Ni, Co)2Si particles in Cu–Ni–Co–Si alloy was investigated by experimental observations and coarsening kinetics calculations when aged at 450, 500, 550 and 600 °C for different durations. The results show that the critical particle radius for coherence mismatch is found to be 10.3 nm, and particles larger than 25 nm are generally semi-coherent. The relationship of (Ni, Co)2Si particles size and aging time follows Lifshitz, Slyosov and Wagner (LSW) theory. The particle size distributions fit well to the LSW theoretical distribution. The activation energy for (Ni, Co)2Si coarsening is accurately determined to be (216.21 ± 5.18) kJ·mol−1 when considering the effect of temperature on the solution concentrations in matrix. The coarsening of (Ni, Co)2Si particles in Cu–Ni–Co–Si alloy is controlled by diffusion of Ni, Co and Si in Cu matrix. The growth of particles for long durations suggests that vacancies can be trapped within the structure for long time despite their mobility.

Nano‐synthesis, characterization, modeling and molecular docking analysis of Mn (II), Co (II), Cr (III) and Cu (II) complexes with azo pyrazolone ligand as new favorable antimicrobial and antitumor agents

Novel nanosized Mn (II), Co (II), Cr (III) and Cu (II) complexes were synthesized with 2‐((5‐oxo‐1,3‐diphenyl‐4,5‐dihydro‐1H‐pyrazol‐4‐yl)diazenyl) benzoic acid, HL applying precipitation method. Their structures were characterized based on the elemental and thermal analyses, spectra (FT‐IR, UV–Vis, MS, ESR and XRD), conductivity and magnetic moment measurements. IR spectra offered that HL behaves as monobasic tri‐dentate ligand towards Mn (II), Cr (III) and Cu (II) and monobasic bi‐dentate towards Co (II). The XRD results unambiguously confirmed the crystalline nature and nano‐sized particles of Cu (II) complex while HL and other complexes exhibited amorphous phases. The magnetic moment data, UV–Vis and ESR spectra supported the formation of octahedral geometries for Mn (II), and Cr (III) complexes, whereas Co (II), and Cu (II) complexes showed tetrahedral arrangement. The activation parameters for the thermal degradation stages were theoretically calculated using TGA curves. The obtained data showed the inspected complexes as favorable antimicrobial drug candidates. The studied compounds were screened out for their antitumor and antimicrobial activities. The inspected compounds exhibited a reasonable antibacterial activity and weak antitumor efficacy. The in vitro results were confirmed using the in silico molecular docking analysis (docking server) applying x‐ray crystallographic structures of the proteins (4 m01, 3 t88, 1zap & 4ynt) from PDB (Protein Data Bank). HL and probably its complexes displayed adequate binding with the receptors of 4 m01, 3 t88, 1zap, and 4ynt microorganisms. The obtained data show the inspected complexes as favorable antimicrobial drug candidates.

Counting surface redox sites in carbon-supported electrocatalysts by cathodic stripping of O deposited from N2O

Methods of determining in situ the electrochemically active surface area of bulk noble metal electrodes (e.g., underpotential deposition of a strongly interacting sorbent followed by columbic stripping) may not be appropriate for certain base metals supported on electroactive supports, such as carbon, because of the difficulty of finding a metal-specific titrant and because the support itself can contribute a very large background current. For example, the coulometric stripping of metal-selective sorbates, like carbon monoxide, works for the in situ characterization of certain electrode-supported metals (e.g. Pt, Pd) if applied carefully, but not for base metals, like Cu that do not strongly adsorb the titrant. Moreover, in scoping studies, we found that underpotential deposition of Tl on carbon-supported Cu failed to be selective for the copper. Here we present the use of gentle oxidation of the metal domains using N2O as the oxidant, followed by cathodic stripping of the surface oxide. The method compares approximately with XRD line broadening for characterizing ∼10 nm particles of Cu supported on graphite felt. More significantly, we show that the method usefully normalizes the rates of two electrochemical hydrogenation reactions: conversion of nitrobenzene to aniline and conversion of benzaldehyde to benzyl alcohol.

Microwave-shielding behavior of silanized Cu and Cu–Fe3O4 compound particle-reinforced epoxy resin composite in E-, F-, I-, and J-band frequencies

In this work, microwave-shielding behavior of epoxy thermosetting plastic reinforced with silanized Cu and Cu–Fe3O4 compound particles were studied in frequency bands E, F, I, and J. The principal aim of this work is to evaluate the significant advantage of surface-modified magnetic and conductive fillers over as-received fillers in microwave shielding. The conductive and magnetic properties of epoxy resin were improved by additions of Cu and Fe3O4 particles. Compound particles of Cu–Fe3O4 were produced by mechanical alloying process (ball milling). The compound particles were surface treated by 3-Aminopropyltrimethoxysilane (APTMS) for better dispersion in epoxy resin matrix. Functional groups on particle’s surface after silane surface treatment were confirmed by FT-IR spectra analysis. The TEM images revealed that effective Cu–Fe3O4 particle compounding was formed at 1 h milling time. The maximum dielectric constant of 6.8 and magnetization of 675E−6 were observed for surface-modified compound particle-reinforced epoxy composite designation RCF2. Similarly, maximum microwave attenuation of 35% (44 dB) was observed for surface-modified compound particle-reinforced composite designation RCF2 in ‘J’-band frequency.

Precipitation priority in 5083 Al-alloys containing small amounts of Cu or Zn

ABSTRACTThis study investigated the precipitation priority in Al–Mg alloys modified by the addition of 0.8 wt-% Cu or Zn, revealing that both these alloys exhibit increased hardness and decreased corrosion resistance. Scanning electron microscopy, transmission electron microscopy, and high-angle annular dark field imaging show that the precipitation priority changed the main second-phase particles of Cu- and Zn-containing alloys. Additionally, thermodynamic data of these phases were calculated using a semi-empirical model, showing good agreement with the experimental results.This paper is part of a thematic issue on Light Alloys.

Influence of chemical leaching on Al-Cu-Co decagonal quasicrystals

In the present investigation, the chemical leaching of the poly-grain Al65Cu15Co20 and Al65Cu20Co15 decagonal quasicrystalline alloys have been studied. The polished surfaces of as-cast Al65Cu15Co20 and Al65Cu20Co15 alloys have been leached by 10 mol/litre (mol/L) concentrated NaOH alkaline solutions. The X-ray diffraction, Scanning electron microscopy and Transmission electron microscopy techniques have been used for the structural and microstructural characterization of the samples and the chemical composition were characterized using Energy-dispersive X-ray spectroscopy. Chemical leaching exclusively removes the Al from the surfaces of the Al65Cu15Co20 and Al65Cu20Co15 decagonal quasicrystalline alloys, consequentially the formation of porous structure containing nano size particles of Cu, Co and Co3O4 have been observed on the leached surface. The leached surface of Al65Cu15Co20was more porous compared to Al65Cu20Co15 alloy, however the size of the precipitated nano-particles i.e. Cu, Co and Co3O4 were smaller in the case of Al65Cu20Co15 alloy. The elemental mapping through energy dispersive X-ray spectroscopy suggests that the distribution of Cu and Co were formed on the leached surface, however in some regions the oxygen was also detected.

Influence of Zinc on Coarsening of δ-Ni2Si Particles, Aging Behavior and Hardness in a Cu-Ni-Si Alloy

In the present paper, the aging precipitation and coarsening of disk-like δ-Ni2Si particles in Cu and Cu-10Zn alloys aged at 450 °C have been investigated by hardness, electric resistivity measurement and transmission electron microscopy observation. The coarsening dynamics of the average diameter of the δ-Ni2Si particles coincides with the t 1/3 time law for both alloys. The coarsening of the diminution of supersaturation related to aging time t coincides with the t −1/3 time rule. Adding Zn to the Cu-Ni-Si alloy increases the growth and coarsening rate of the particles mainly because of the increased diffusivity D of the δ-Ni2Si particles in the matrix. The value of D of the δ-Ni2Si particles in the Cu-xZn (x = 0, 10 wt.%) matrix and the Cu/δ-Ni2Si interfacial energy γ are independently calculated by using the Lifshitz–Slyozov–Wagner theory which was extended to include disk-like particles by Boyd and Nicholson. The values of D and γ increase from 0.77 × 10−19 to 2.21 × 10−19 m2/s and 0.19 to 0.63 J/m2, respectively, when Zn is added to the Cu-Ni-Si alloy. These calculations and the analysis show that the properties of Cu-Ni-Si-Zn alloy can significantly be enhanced by reducing the aging temperature.

Green synthesized urchin like Pt/Cu bimetallic photonanocatalysts: Understanding composition effect

Nanometric urchin like monometallic and bimetallic alloy particles of Cu and Pt were tailored via a green aqueous approach utilizing starch, a well known green stabilizing agent and ascorbic acid at room temperature. The fabricated Pt and Cu monometallic and Pt/Cu bimetallic (B1 and B2) alloy nanoparticles are well crystalline and adopted identical average particle size of about 23nm as measured via transmission electron microscopy. The bimetallic systems display remarkable light promoted activities in degradation of organic pollutant, malachite green, to its mineralized products which was otherwise very slow. The photo degradation reaction follows first order kinetics and apparent rate constant for catalysis reaction follows the trend: k(app)B2NPs>k(app)B1NPs>k(app)PtNPs>k(app)CuNPs. Shifting of surface d band center and lower photo-induced electrons and holes recombination rate seem to play important roles in enhancing catalytic property of the bimetallic systems.

Charge-dependent anisotropic flow in Cu + Au collisions

We present the first measurements of charge-dependent directed flow in Cu+Au collisions at sNN=200 GeV. The directed flow has been measured as functions of the transverse momentum and pseudorapidity with the STAR detector. The results show a small but finite difference between positively and negatively charged particles. The difference is qualitatively explained by the patron-hadron-string-dynamics (PHSD) model including the effect of the electric field, but much smaller than the model calculation, which indicates only a small fraction of all final state quarks are created within the lifetime of the initial electric field. Higher-order azimuthal anisotropic flow is also presented up to the fourth-order for unidentified charged particles and up to the third-order for identified charged particles (π, K, and p). For unidentified particles, the results are reasonably described by the event-by-event viscous hydrodynamic model with η/s=0.08−0.16. The trends observed for identified particles in Cu+Au collisions are similar to those observed in symmetric (Au+Au) collisions.

Heat and mass transfer analysis for the MHD flow of nanofluid with radiation absorption

Abstract In this paper the effects of Diffusion thermo, radiation absorption and chemical reaction on MHD free convective heat and mass transfer flow of a nanofluid bounded by a semi-infinite flat plate are analyzed. The plate is moved with a constant velocity U 0 , temperature and the concentration are assumed to be fluctuating with time harmonically from a constant mean at the plate. The analytical solutions of the boundary layer equations are assumed of oscillatory type and are solved by using the small perturbation technique. Two types of nanofluids namely Cu-water nanofluid and TiO2-water nanofluid are used. The effects of various fluid flow parameters are discussed through graphs and tables. It is observed that the diffusion thermo parameter/radiation absorption parameter enhance the velocity, temperature and skin friction. This enhancement is very significant for copper nanoparticles. This is due to the high conductivity of the solid particles of Cu than those of TiO2. Also it is noticed that the solutal boundary layer thickness decreases with an increase in chemical reaction parameter. It is because chemical molecular diffusivity reduces for higher values of Kr.

Composition Control and Formation Pathway of CZTS and CZTGS Nanocrystal Inks for Kesterite Solar Cells

The ability to reproducibly synthesize nanocrystal (NC) inks with precisely controlled compositions is essential for making efficient kesterite solar cells from NCs. Here we present the results of a study on Cu–Zn–Sn–S NCs in which different particle size fractions were collected over a range of reaction times from various starting reagents. From this we have determined the temporal evolution of the NC ink and identified at least two distinct particle populations that form following injection: large particles containing primarily Cu and Zn, and small particles of Cu and Sn. For short reaction times, the extreme compositional heterogeneity between these size fractions makes the average ink composition highly sensitive to changes in reaction time and precipitation procedure. Longer synthesis times produce more consistent inks, with higher yield, and compositions closer to that of the starting reagents. The choice of metal precursor was found to have a minor impact on the composition of the resulting ink com...

Comparative Study on the Surface Dose of Some Bolus Materials

In order to investigate the possibility of using different materials as bolus in radiotherapy, five samples denoted by S2 - S6 were prepared and analyzed by comparison with one available commercial bolus denoted by S1. Sample S1 was a thermoplastic material from Qfix; S2 was a moldable silicon rubber (RTV-530 from Prochima); S3 and S4 were obtained by adding micrometric particles of Al and Cu respectively (at the same mass concentration of 5.5%); S5 was another moldable silicon rubber (GSP400 from Prochima) and S6 was a mixture of GSP400 and micrometric particles of Cu (at the mass concentration of 5.5%). The measurements of normalized transmitted dose as a function of sample thickness were performed for all samples (S1 - S6) at two values of electron beam energy (6 and 9 MeV) produced by a linear accelerator VARIAN 2100SC. The results showed that the maximum of the normalized transmitted dose of manufactured samples (S2 - S6) is registered at smaller sample thicknesses than for the analyzed commercial bolus (sample S1). The smallest sample thickness corresponding to normalized maximum point dose is obtained for sample S2 (RTV-530). Measurements performed for electron beam energy of 6 and 9 MeV have proven the possibility of using the manufactured samples as bolus in radiotherapy.

The bactericidal effect of dendritic copper microparticles, contained in an alginate matrix, on Escherichia coli.

Although the bactericidal effect of copper has been known for centuries, there is a current resurgence of interest in the use of this element as an antimicrobial agent. During this study the use of dendritic copper microparticles embedded in an alginate matrix as a rapid method for the deactivation of Escherichia coli ATCC 11775 was investigated. The copper/alginate produced a decrease in the minimum inhibitory concentration from free copper powder dispersed in the media from 0.25 to 0.065 mg/ml. Beads loaded with 4% Cu deactivated 99.97% of bacteria after 90 minutes, compared to a 44.2% reduction in viability in the equivalent free copper powder treatment. There was no observed loss in the efficacy of this method with increasing bacterial loading up to 106 cells/ml, however only 88.2% of E. coli were deactivated after 90 minutes at a loading of 108 cells/ml. The efficacy of this method was highly dependent on the oxygen content of the media, with a 4.01% increase in viable bacteria observed under anoxic conditions compared to a >99% reduction in bacterial viability in oxygen tensions above 50% of saturation. Scanning electron micrographs (SEM) of the beads indicated that the dendritic copper particles sit as discrete clusters within a layered alginate matrix, and that the external surface of the beads has a scale-like appearance with dendritic copper particles extruding. E. coli cells visualised using SEM indicated a loss of cellular integrity upon Cu bead treatment with obvious visible blebbing. This study indicates the use of microscale dendritic particles of Cu embedded in an alginate matrix to effectively deactivate E. coli cells and opens the possibility of their application within effective water treatment processes, especially in high particulate waste streams where conventional methods, such as UV treatment or chlorination, are ineffective or inappropriate.

Polymer antimicrobial coatings with embedded fine Cu and Cu salt particles

Many diseases spread due to the bacterial infections, which cause significant economic and personal losses. Contact with infected surfaces is likely to catch infections. Hence, antimicrobial surfaces play an important role in public sectors that can prevent the spreading of disease and infection. Coatings on contact surfaces have been used to provide antimicrobial function. Copper (Cu), as one of the commonly used metals, has long been known to possess germ-killing properties. However, metallic Cu or Cu coatings have not been widely used for the purposes of antimicrobial due to the heavy weight, relatively high cost, limited corrosion resistance and low compatibility of the metal with substrates of non-metallic materials. We have recently developed a polymer-based coating system containing mixtures of fine particles of Cu and Cu salt, which provides excellent antimicrobial properties. The results indicate that the coating with embedded fine Cu salt showed higher antimicrobial property than the coating with only Cu due to the release of more Cu ions. The elimination of 10(6) bacteria by contacting the polymer-Cu coatings needs 8 h, while contacting with the polymer-CuCl2 coatings took only 20 min to kill the same amount of bacteria. We have also used transmission electron microscopy and synchrotron infrared microscopy technique to study the degradation of bacterial cell membrane to understand the mechanism of the antimicrobial function of Cu coating.