Copper Samples Research Articles

Коррозионная усталость меди в водных средах

The failure of the cooling systems of engines and propellers of the ship poses the serious hazard to passengers and crew. Damage to these units is often caused by corrosion, with localized corrosion being the most dangerous. In the case under consideration, when the metal is simultaneously affected by a corrosive environment and alternating mechanical loads, conditions arise for the behaviour (occurrence) of corrosion fatigue. The prospects of cathodic electrochemical protection of these units are considered in the paper. Since the cooling systems and propellers are made of copper alloys, the effect was studied concerning the potential and composition of the solution on the corrosion of the main component of the structural material — copper. Copper samples with a smooth mechanical pressure concentrator cantilevered in a fluoroplastic electrochemical cell were tested. Alternating bending loads were applied to them, and the number of load cycles before the destruction of the sample (durability) was determined. The experiments were carried out in deaerated solutions of the surfactantly inactive electrolyte NaF, as well as fluoride solutions with additives of surfactants and organic surfactants - benzotriazole. At the same time, an interval of potentials was set, in which the only Faraday process is possible — the reduction of traces of dissolved oxygen. It was found that at potentials less than the zero charge potential, the durability of copper increases significantly. And the introduction of chloride ions and benzotriazole into the solution, on the contrary, leads to a strong decrease in its durability. The potential of zero charge of copper was determined from the measurement data of the differential capacitance of the metal in sodium fluoride solutions with different concentrations of fluoride. The increase in the durability of the metal is explained by the occurrence of hydrogen bonds between the water molecules adsorbed by the hydrogen atoms. This manifests the so-called negative Rebinder effect. For electrochemical protection, the potential range is recommended below the potential of zero charge of the metal, but above the potential of water decomposition. For cooling systems, it is recommended to use deionized water as a coolant.

Mitigation of ion-induced desorption for accelerator components by surface treatment and annealing

Ion-induced desorption is a serious limitation for beam intensity and life time in heavy ion accelerator facilities. To investigate how gas desorption is affected by surface conditions and bulk materials, oxygen-free copper, tungsten and aluminum samples were irradiated with 4.8 MeV/u Ca and Au ions. The surfaces were pretreated by various combinations of milling, lapping, polishing and etching, while the bulk is conditioned by thermal annealing. For all tested samples desorption yields of H2, H2O, CO and CO2 are presented. Diamond milling and polishing reduce ion-induced desorption to some extent, but most pronounced effects were achieved by ex-situ thermal annealing at 400 °C for about 4 h under ultra-high vacuum conditions. The decreased desorption persists for at least 9 months of storage in atmosphere. This is a strong indication that for the mitigation of desorption stimulated by high energy ion exposure, not only the surface properties have to be optimized, but also the treatment of the bulk material plays an important role. Storage of annealed samples in argon is favorable compared to storage in atmosphere.

Correlating topographical characteristics of relaxed layer to tribology in Cu-Gr-TiC composite system

The copper graphite composites are often being applied as bearing materials in various industries. In present investigation, the correlation between the topographical characteristics of relaxed layer to tribology in Cu-Gr-TiC composite system has been investigated. For this purpose, the flake powder metallurgy approach was used to fabricate Cu-Gr-TiC composites and the tribology of these composites was studied under lubricating (synthetic SAE 20W40 motor oil) condition. Variable loads of 10 N–70 N, sliding velocities of 0.75 m s−1–3 m s−1, and sliding distances of 2000 m–8000 m were the test parameters for sliding wear of composites under lubricating conditions. The worn surfaces were examined using SEM and EDS while topographical parameters were studied by AFM. The other properties like mechanical and physical properties were also studied for the sintered samples to better correlate the overall results of surface topography and tribology. The tests depict the successful fabrication of the composites. The composite having 4.5 wt% TiC particles exhibit maximum hardness and least wear and CoF under lubricating environment. The results of sliding wear test conducted under lubrications revealed that rise in the concentration of nano TiC particles in the matrix improves the composite’s tribological performance. The mechanism of wear for pure copper sample is abrasion whereas for TiC particle reinforced composite is smooth ploughing and delamination. The surface topographical parameters that are average surface roughness, area peak to valley height and skewness depicted less roughness values and better load bearing capacity for 4.5 wt% TiC reinforced Cu-Gr sample. The fabricated TiC reinforced copper graphite composites could be utilized as bearing materials in automotive industries.

Extruded 3D Printing Assisted Electrochemical Additive Manufacturing

This essay investigates an additive manufacturing technique of an extruded 3D printing-assisted electrochemical deposition. The effects of solutions with different additive (Cl− and brightener) concentrations on the surface micromorphology and deposition rate of the formed films were investigated by using characterization data from test tools such as an electrochemical workstation, X-ray diffractometer, and scanning electron microscope, as well as discussing the laws of interaction between these two additives during the electrodeposition process. The experimental results show that when the concentration of Cl− in the copper plating solution is 2×10−3 mol/L and the brightener concentration is 10 ml/L, the electrodeposition experiments yielded deposited copper films with a significantly preferred orientation on the (111) crystal plane, and the prepared copper film has thicker deposited film and better surface quality. To validate the additive manufacturing method for extruded 3D printing-assisted electrochemical deposition, deposition experiments of 25-layer copper samples were carried out utilizing the best process parameters.

Long-term repeatability improvement using beam intensity distribution for laser-induced breakdown spectroscopy

The relatively low measurement repeatability has long been considered as a major obstacle to the widespread use and commercialization of laser-induced breakdown spectroscopy (LIBS). Although many efforts have been made to improve the signal repeatability in the short term, how to improve the long-term signal repeatability is critical in practical applications and has rarely been studied. Moreover, the mechanisms behind the degradation of long-term repeatability are not fully revealed. This study proposes a new method to improve the long-term repeatability of LIBS measurement, which modifies the spectral intensity based on laser beam intensity distribution. It first pre-processes the beam intensity distribution profiles and spectral intensity. Then the relationship between the relative deviations of beam and spectral intensities is modelled using Partial Least Squares Regression (PLSR). The proposed method was tested on copper and silicon samples, and the spectra and laser beam intensity distribution were recorded for more than thirty days. Day-to-day variations in beam intensity distribution were observed. Such variations can lead to changes in spectral intensity, resulting in degraded signal repeatability. By modifying the spectral intensity, the long-term signal repeatability was improved. Specifically, in terms of day-mean spectral intensity, the valid correction rates were above 70% for both of copper silicon sample in most cases. Long-term RSD decreased from ∼13.5% to ∼4% for copper and decreased from ∼10.7% to 6.5% for silicon sample. These results indicate that the proposed method provides a viable method for improving the long-term repeatability of LIBS measurement.

Correlation between the developed layer's color and crystallographic orientation of pure copper during long-term color etching with Beraha˗I

In situ optical microscopy investigation was performed on a Cu99.9 copper sample during color etching with Beraha˗I etchant for approximately 48 min in a microfluidic cell. The color change of the individual grains was analyzed by measuring light intensity change for different (RGB) wavelengths. Using these values, the luminance was calculated and visualized as a function of time. Crystallographic orientations of the examined grains were also determined by electron backscatter diffraction so that the layer-developing mechanisms could have been assigned to specific directions. Our experiment showed that not only the resulting color depends heavily on the orientation, but the different grains' planar density also affects the etching characteristics. It was shown that besides the cyclic color change originating from thin film interference, a significant contribution of the developed film's color comes from the absorption properties of the layer. Relying on these characteristics, a method was proposed to differentiate grains based on their planar density. Our experiments showed that grains close to the more dense orientations, like (100) and (111) developed a bright white color and kept it during the whole etching process. In contrast, grains that were close to sparse orientations (i.e., farthest from (100) orientation), like (122) or (133) developed a dark brown color. Grains with more general directions demonstrated a similar cyclic color change as previously examined on other materials, such as ferrite in the case of low-carbon steel and cast iron.

Evaluation of the infill design on the tensile properties of metal parts produced by fused filament fabrication

Additive Manufacturing (AM) applications have expanded significantly from rapid prototyping to high-end products such as complex spare parts. AM has enabled advantages of reduced material usage, geometric freedom, and production automation, shaping the future of the manufacturing industries. With the rapid expansion of AM applications, feedstock materials have developed noticeably, from polymers and ceramics to metals and composites. The progress in metal feedstock material discoveries has empowered the exploration of implementing new AM technologies. Fused Filament Fabrication (FFF) is one of the most common and cost-effective material extrusion AM technologies. This study explores the effect of the infill pattern on the tensile mechanical properties of metal parts produced via FFF, using two feedstock materials, 17-PH stainless steel and copper. Two approaches are designed to investigate the results: experimental tensile test, and Finite Element Analysis (FEA) with digital twin reconstruction method. Results show that 17-4 PH Stainless Steel samples with a triangular infill exhibited a 42% drop in ultimate tensile strength compared to solid infill. However, it also revealed a 34% reduction in mass, cost saving of 36%, and a faster fabrication with a 25% reduction in lead time. At the same time, copper samples with triangular infill exhibited a 22% drop in ultimate tensile strength and a 12% mass reduction. However, it revealed a similar lead time with only a 3% reduction. A Scanning Electron Microscope (SEM) was used to investigate the parts’ internal structure and average pore size, to understand the failure mode of the test specimens.

An adhesion study in Ni and Cu nanocontacts from a molecular dynamics perspective

In this work, the effects of adhesion in nanoscale indentation tests with copper and nickel samples indented with a spherical diamond tip have been studied. The tests have been simulated by molecular dynamics, initially selecting the appropriate potentials according to the pair of materials put in contact. The force-displacement curves of a complete cycle of loading and unloading have been determined and a procedure for the simultaneously determination of the indentation modulus of elasticity and the adhesion energy of inelastic indentations have been developed. Likewise, a critical evaluation of the contact models available in the literature has been carried out, assessing their suitability for the cases analysed.

An optimized single-crystal to polycrystal model of the neutron transmission of textured polycrystalline materials

The attenuation coefficient of textured materials presents a complex dependence on the preferred orientation with respect to the neutron beam. Presented here is an attenuation coefficient model to describe textured polycrystalline materials, based on a single-crystal to polycrystalline approach, aiming towards use in full-pattern least-squares refinements of wavelength-resolved transmission experiments. The model evaluates the Bragg contribution to the attenuation coefficient of polycrystalline materials as a combination of the Bragg-reflected component of a discrete number of imperfect single crystals with different orientations, weighted by the volume fraction of the corresponding component in the orientation distribution function. The proposed methodology is designed to optimize the number of single-crystal orientations involved in the calculation, considering the instrument resolution and the statistical uncertainty of the experimental transmission spectra. The optimization of the model is demonstrated through its application to experiments on calibration samples presenting random crystallographic textures, measured on two imaging instruments with different resolutions. The capability of the model to simulate textured samples in different orientations is shown with a copper sample used as a reference in texture studies of archaeological objects and a 316L stainless steel sample produced by laser powder-bed fusion. The ability of the model to predict the attenuation coefficient of polycrystalline textured materials on the basis of a reduced number of texture components opens the possibility of including it in a least-squares fitting routine to perform crystallographic texture analysis from wavelength-resolved transmission experiments.

Study of Tribological Properties of Bulk Nanostructured Aluminum and Copper Samples Applicable in Automotive Bearing Application

Using lightweight systems and friction reduction approaches are two main contributors towards modern and efficient powertrains in the automotive industry. New materials and processes are required to achieve the demanding and ever-increasing performance requirement of automotive systems. Nanostructure induced by severe plastic deformation methods involves bimodal microstructures and hence, shows exceptional mechanical characteristics which can be exploited for automotive application. Through this study, samples were prepared using pure copper, aluminum alloy (series 7000) and were processed to attain bulk nanostructured samples using a Single Step High Pressure Torsion technique with appropriate dimensions applicable as the rolling elements of automotive bearings. The induced nanostructures resulted micro hardness and frictional characteristics of the bulk samples were assessed using transmission electron (TEM) and atomic force (AFM) microscopies as well as microhardness evaluations. The results revealed that a fully refined nanostructured samples were achieved with 90% increase in the hardness at the outer diameter of the sample. The AFM measurements indicated that the friction coefficient of nanostructured copper and aluminum samples were ~ 25 and ~ 45% less than that of both the unprocessed samples, respectively. Characteristics of treated samples suggest that these processes can be potentially used in demanding conditions of rolling element bearings with reduced weight and frictional losses.

Frictional behavior of severe plastic deformed copper sample by using friction calibration curves

Equal Channel Angular Pressing (ECAP) known as one of the most significant methods involving in severe plastic deformation. There are not many investigations which focus on the design of dies and its analysis by FEM, considering friction coefficients as die geometry parameters; likewise, only few studies have been reported in which the effect of die shape has been analyzed, for example. One of the challenging problems in industrialization of ECAP is designing and manufacturing of die. To avoid trial and error in the next designs, the measurement of right friction coefficient plays a key role, which is used in finite element method to prevent doing experimental test. The main objective of this study was to investigate and find generalized friction calibration curves utilizing the ring compression test. To perform the ring compression test, which is oxygen-free copper with 99.7%, (BS EN 15079 standard) the standard ring specimen ratio of 6:3:2 was used. With use of different lubricants during the ring compression test the relations between friction coefficients and changes of inner and outer diameters was revealed. To solve complicated plasticity equations with complex geometries and boundary conditions with various friction coefficients, finite element method was used. To use more accurate frictional coefficient values with considering different ECAP passes, friction calibration curves were updated.

Surface durability during high-speed spray impingement onto heat-exchanger materials and modified surfaces

Surface durability was investigated for materials used in electronics and heat exchangers during water spray impingement at ambient conditions. Smooth, rough, and modified copper and aluminium samples were tested with surface hardness, roughness and contact angle ranging from 52–100 HV, 0.53–79.28 μm and 48-153°, respectively. Although material loss and hardness alterations were insignificant after the high-speed droplet collisions, changes in surface morphology were observed. Both smooth and rough surfaces were resistant to 36-hour sprays with droplet velocities from 11–22 m s−1. However, sprays did cause changes in surface roughness and static contact angle, and the water repellent coatings were damaged, losing their low wettability.

Experimental–Numerical Study of the Effect of Per Pass Applied Strain on the Electrical and Mechanical Properties of Copper Samples in Twist Extrusion Process

Experimental–Numerical Study of the Effect of Per Pass Applied Strain on the Electrical and Mechanical Properties of Copper Samples in Twist Extrusion Process

3D printing for heat transfer: characterisation of additive manufactured copper

Recent technological advancements now allow for copper to be 3D printed, opening the doors for this technology to take a greater part in heat transfer applications. In this study, copper samples were additively manufactured through a print-debind-sinter process and thermally characterised in terms of thermal conductivity and specific heat capacity, and mechanically characterised in terms of Vickers hardness. The microstructure porosity levels appeared to control the thermal properties measured, with the thermal conductivity, while the specific heat was unaffected, while the heat treatment effect caused by the sintering process appeared to control the Vickers hardness measured.

Reduction of copper from oxides when heated in air

The paper presents the results of experiments on the reduction of copper oxides formed during the heat treatment of metallic copper samples in air. The necessary condition is the presence of a muffle made of a material with a higher electron affinity (lower standard electrode potential) compared to copper. Replacing nitrogen in the composition of the atmosphere with an equal proportion of argon does not change the observed redox pattern. Our results indicate an electrochemical mechanism for the reduction of copper oxides in a steel muffle, in which oxygen plays the role of a charge carrier. Keywords: oxidation of metallic copper, reduction of copper oxides, steel muffle, air, oxygen, electrochemistry.

Восстановление меди из оксидов при нагревании в воздухе

The paper presents the results of experiments on the reduction of copper oxides formed during the heat treatment of metallic copper samples in air. A necessary condition is the presence of a muffle made of a material with a higher electron affinity (lower standard electrode potential) compared to copper. Replacing nitrogen in the composition of the atmosphere with an equal proportion of argon does not change the observed redox pattern. Our results indicate an electrochemical mechanism for the reduction of copper oxides in a steel muffle, in which oxygen plays the role of a charge carrier.

The influences of ambient humidity on laser-induced breakdown spectroscopy

The effect of ambient humidity on the LIBS spectra of copper samples was explored. The Cu I line intensity decreased with humidity at low laser energy and increased with humidity at high energy.

The effect of simple shear extrusion on the mechanical properties and microstructure of copper

Simple Shear Extrusion is a recently designed Severe Plastic Deformation procedure capable of obtaining nanostructured materials. The effect of the number of passes on the copper sample has been investigated. Through tensile test and Scanning Electron Microscopy mechanical properties and grain size have been investigated. According to the Hall-Petch equation the yield strength (138–198 MPa) and microhardness (74–128 HV) of the annealed sample of copper after each pass of the SSE increased by reducing the grain size (39–16 µm).

Copper-Bearing Mineralisation in the Upper Devonian Limestones: A Case Study from the Historical Teresa Adit in the Świętokrzyskie Mountains, Poland

The studied copper ore deposit is located in Miedzianka Mountain (Świętokrzyskie Mountains, central Poland). This deposit was exploited from the 13th century to the 1950s; therefore numerous historical adits are currently present. One of these is Teresa adit (established in 1805), consisting of underground mining corridors and natural cave developed in the Upper Devonian limestones, partially transformed by mining works. Samples of copper- and rock-forming minerals in limestones collected at seven sites within the richest copper-bearing mineralisation in this adit were studied with petrographic investigation of thin sections, micro-area chemical analysis (EDS), and XRD. This study shows the presence of various minerals: (a) Cu-Fe sulphides (relics of chalcopyrite) and Cu sulphides (covellite, chalcocite), (b) Cu-Fe oxides (cuprite and hematite), (c) Ca and Cu carbonates (calcite, azurite, and malachite), (d) clay minerals (Fe-Mg illite), and (e) micro-crystalline silica (quartz). For the first time in the studied deposit, we described chalcopyrite relics in cuprite pseudomorphosis, hematite with admixture of vanadium in pinkish-creme veins in limestones, and the presence of an admixture of Fe-Mg illite and microcystaline silica within cracks of limestones. In addition, for the first time, unit cell parameters of malachite and azurite from Miedzianka Mountain were determined, indicating very low substitutions of atoms other than Cu in their structures. We suppose that the minerals studied were formed during three types of copper mineralisation processes: (a) hydrothermal (relics of chalcopyrite), (b) secondary weathering (chalcocite, covellite, cuprite, hematite), and (c) adsorptive mineralisation (azurite, malachite). The latter stage is related to residuum, which consists of a mixture of Fe-Mg illite and micro-crystalline quartz, which was formed during the dissolution of limestones in karst processes in some crevices. We proposed a model of the formation of copper carbonates in the adsorption stage of the copper-bearing mineralisation in Miedzianka Mountain deposits. Two generations of calcite veins (older—red calcite and younger—crème-pinkish calcite) were also detected. Mineralogical–petrographical studies of samples revealed a high scientific and educational value. Due to the fact that the Teresa adit is planned to be made available to geotourists, this work is worth presenting to the public either in the adit and/or in a local museum in Miedzianka village.

Physical and mechanical properties of ultrapure copper obtained by zone melting

This paper presents the results of studies on the electrical conductivity, macro- and microstructure of ultrapure copper (5N3) obtained after zone melting of refined copper (99.96% Cu). The effect of residual concentrations of impurity metals on the electrical conductivity of ultrapure copper has been established. To assess the effect of low concentration impurities on the electrical conductivity of copper, the authors used a linear dependence of the increase in resistivity on the concentration of impurities (Ci), which was determined by the Mathyssen-Fleming rule. It is shown that low residual concentrations of impurity metals obtained in copper after its zone melting refining, ppm (ppm = 10–4 %): 0.2As; 0.06Sb; 0.006Ag; 0.07Bi; 0.006Sn; 0.02Pb; 1,1Ni have practically no effect on the electrical conductivity of ultrapure copper. The maximum electrical conductivity of M00K industrial grade copper (99.99% Cu) is 59 MSm/m, while zonerefined copper with a copper content of 99.999% has the electrical conductivity of 60.2 MSm/m. The values of the electrical conductivity of the obtained samples can serve to control the quality of obtained copper. It is shown that, in contrast to the microstructure of the initial copper sample, the ultrapure copper microstructure is a densely packed structure consisting of fine grains. On the microstructure map of ultrapure copper, the presence of individual impurity metals in the form of rounded small balls was established. Elongated filaments in the form of continuous lines, which are associated with the formation of chemical compounds of impurity metals with each other, are also found. This phenomenon is clearly observed on the microstructure map of ultrapure copper, captured at a magnification of 1000x under conditions of etching of the sample under study. The values of macro- and microhardness of the initial copper sample and ultrapure copper sample are established. The hardness of the initial copper sample is 84.42 HB (according to Brinell). After zone melting refining of copper from impurities, the hardness of the resulting ultrapure copper was 59.85 HB. Measurements of the microhardness of samples of the initial copper sample and ultrapure copper obtained by zone melting showed the microhardness of 103.0 and 70.42, respectively.