Narrow Results

Several studies using Friction Stir Welding (FSW) on dissimilar Aluminium and Copper weld configurations and the mechanical and microstructure characteristics, as well as the identification of intermetallic phases that appear in the weld region, have been conducted. Indeed, earlier several studies had been conducted in both lap and butt FSW joint designs. Even so, Al–Cu lap welding has received further attention than butt–welding, which has attracted only a few studies thus far. The studies ended with varying findings and were unable to reach high strengths despite the fact that very few studies addressed tool placement factors. The present investigation starts with butt–welding of AA1050 and pure Cu sheet by employing the FSW procedure. Experimental trails were designed using the L16 array (Taguchi’s technique) with distinct combinations of tool spinning speed, tool offset, welding speed, and plunge depth. Weld parameters such as compressive strength (CS), ultimate tensile strength (UTS), and average hardness at nugget zone (AHNZ) were evaluated using three different optimization methodologies, i.e. the WASPAS method, Alibaba and the Forty Thieves algorithm, and the Taguchi–WASPAS method, to find out the best weld constraint arrangement for maximizing the welded joint mechanical characteristics. ANOVA test was also conducted, which revealed that welding speed is the most significant and influential FSW factor for Al–Cu butt–welding using FSW. Finally, confirmatory tests were piloted to check the consistency of the predicted FSW parameters.

An analysis to the characteristics of Co, Mg and Cu ferrites that were prepared using sol–gel method and annealed at $800^{\circ }$C for 1 hour, performed using X-ray diffraction and Raman spectroscopy for structural characteristics, while the Vibrating Sample Magnetometer (VSM), was used for the magnetic characteristics. The X-ray analysis of both cobalt and magnesium ferrites shows a reverse crystal structure of a cubic spinel, while copper ferrite shows a tetragonal crystal structure characteristic at this annealing temperature. The lattice constant (a) was found to be $a=8.186$ for CoFe₂O₄, $a=8.199$ for MgFe₂O₄ and $a=5.969$ for CuFe₂O₄. The Raman spectrum confirms a spinel crystalline form of the prepared ferrites where a likely distribution of cation is indicated at the tetrahedral and octahedral sites. The peaks of the Raman shift appear between 200–800cm${}^{-1}$. These peaks indicate the formation of ferrites. The hysteresis loop of CoFe₂O₄ indicates a hard magnet material. Cu ferrites have relatively lower remnants and magnetocrystalline anisotropy, which indicates soft magnetic characteristics even though it showed higher coercivity. The squareness ratio (Mr/Ms) values varied between 0.52, 0.13 and 0.57 for CoFe₂O₄, MgFe₂O₄ and CuFe₂O₄, respectively. These insights highlight the possibility of tuning the properties of ferrites using a cost-effective sol–gel method.

Two chemical solutions NH₄F:H₂O:C₃H₈O₃(sol${}_1)$ and NH₄F:H₂O:C₂H₆O₂(sol${}_2)$ with different fluoride ratios were used separately in an anodic process to study the morphological characteristics of the produced copper oxides. Glycerol and ethylene glycol were utilized as inhibitions to slow down the activity of fluoride ions. The rest of the anodization process parameters were constant. Scanning electron microscope (SEM) images showed the formation of Cu₂O microcubes when sol₁ was used. The utilization of sol₂ produced octahedral Cu₂O as well as cubes and spherical structures. The increase of NH₄F in sol₁ led to a reduction in the volumes of Cu₂O microcubes, and in sol₂, it produced incomplete octahedral Cu₂O. Since ethylene glycol has a lower viscosity than glycerol, copper corrodes more quickly in the presence of the former than in the latter. The findings indicate that sol₁ is experiencing a higher current flow than sol₂. The relationship between current and time is semi-constant at low applied voltage, but the two curves behave differently when applying high voltage in the early stages.

A mild and efficient method for the acid-promoted demetallation of functionalized metalloporphyrins is described. In contrast to the normally harsh conditions required, a variety of Cu porphyrins were rapidly demetallated in excellent yields using methanesulfonic acid in a chlorinated hydrocarbon solvent at room temperature or under microwave heating. Some Co, Ni, and Ag porphyrins could also be efficiently demetallated. Notably, the presence of a small amount of a coordinating solvent in the reaction mixture either completely inhibited the demetallation or significantly slowed it down. Electron withdrawing functionality also slowed down the demetallation time.

Due to their remarkable mechanical, thermal and electrical characteristics, silicon carbide (SiC) single-walled nanotubes (SWNTs) are an unusual and promising class of materials. Density functional theory (DFT) is used in this study to examine the electrical and structural characteristics of copper-doped SiC armchair SWNTs. It has been discovered that copper doping of SiC armchair SWNTs alters the materials’ electrical characteristics. SiC SWNTs band gap plays a significant role in influencing the electrical conductivity and optical characteristics of the substance. The energy bands i.e., valence band and conduction band of SiC armchair SWNTs overlapped as copper doping concentration increased, altering the materials’ electrical conductivity and optical characteristics. Additionally, a continuous density of states plot and a narrower band gap are frequently employed as markers of ferroelectric behaviour which indicates the existence of a polarizable and highly delocalized electronic system. The significance of copper doping in SiC SWNTs is understood by this study, along with the effects of the doping on the material’s electrical properties.

A total of 4269 beard samples were collected from the same person every day over a 12-year period and analyzed by PIXE using a standard-free method. It was found that the concentrations of copper and zinc showed certain short-term changes but did not show a noticeable long-term trend over the study period, with only iron showing a slightly decreasing tendency with age. All of these elements showed clear yearly variations with a cycle of a few years possibly due to periodic metabolic changes in the subject’s body or long-term changes in eating habits. In contrast, however, selenium showed clear seasonal variations. Its concentration significantly increased in the summer and decreased in the winter, just as was observed with arsenic and mercury. This suggests that most of the subject’s selenium intake was from marine products, whose supply and consumption were increased in the summer. These findings confirmed that beard analyses are useful not only for evaluating essential-element intake but also for estimating the relationship between the body-element concentrations and ingestion of certain foods.

The analysis of copper, iron, calcium, and other elements in livers of Long-Evans Cinnamon(LEC) rats by PIXE determination is described. The copper contents in the livers of LEC rats which were supplemented with 1g/100g, in the food of calcium chloride dihydrate and iron(II) chloride n-hydrate, respectively, for 5 weeks were determined before and after supplement by PIXE.

The experimental results showed that after supplement of the calcium- and iron-fortified food the copper content in the livers of LEC rats decreased with the supplement. The present data suggest that supplement of iron or calcium can be responsible for copper homeostasis in livers of LEC rats, and that the excessive accumulation of copper in livers of LEC rats can readily remove when high load of iron or calcium are supplemented.

We present molecular dynamics simulations of the influence of point defects on the shear elastic properties of copper. We find that vacancies do not influence these properties at all, while the introduction of interstitials causes a large reduction of the elastic coefficients. The simulations establish a phase diagram of the melting temperature as a function of the density of interstitials. A crystal having no free surface undergoes bulk mechanical melting as a result of the vanishing of C′ ≡ (C₁₁ - C₁₂)/2 once the specific volume reaches a critical value, equal to the experimental volume of liquid phase. This critical volume is history independent, in the sense that it does not depend on whether is it reached by heating the crystal or by adding defects at a constant temperature. These results generalize the Born model of melting for the case where point defects are present.

The Decoupling Transformation is applied to study various lattice dynamical properties of face-centred cubic metals after it is reformulated in terms of the Cyclic Region Group. The theory is established and illustrated with a running example — copper. Unique set of force constants representing interaction between intersublattices are tabulated and compared to the traditional least-squares fit results. A computer package is developed for deriving those force constants as well as for constructing the phonon spectrum based on the decoupling transformation approach. Further discussion on the approach and the results are also presented.

The grain growth kinetics of nanocrystalline copper thin film samples was investigated. The grain size of nanocrystalline copper samples was determined from the broadening of X-ray spectra. It was found that the grain size increased linearly with isothermal annealing time within the first 10 minutes, beyond which power-law growth kinetics is applied. The activation energy for grain growth was determined by constructing an Arrhenius plot, which shows an activation energy of about 21 – 30 kJ/mol. The low activation energy is attributed to the second phase particle drag and the porosity drag, which act as the pinning force for grain growth in nanocrystalline copper.

We report measurements of the copper plasma parameters generated by the fundamental, second and third harmonics of a Nd:YAG laser. The 3d⁹4s5s²D_3/2→3d⁹4 s4p²F_5/2 at 464.25 nm, 4p ²P_3/2→3d⁹4s²D_5/2 at 510.55 nm, 4d ² D_3/2→4p²P_1/2 at 515.32 nm 4d ² D_5/2→4p²P_3/2 at 521.82 nm and 4p ² P_3/2→3d⁹4s²D_3/2 at 570.02 nm transitions have been used to estimate the electron temperature through the Boltzmann plot method. The number density has been estimated from the Stark broadened profiles of the spectral lines. The spatial behaviour of the electron temperature and number density has been examined at different ambient air pressures and with laser irradiance. The temperature and number density are found to be in the range from 14700 to 13600 K and 2.1×10¹⁶ to 1.78×10¹⁶cm^-3 for the 1064 nm laser, from 14200 to 12800 K and 2.2×10¹⁶ to 1.8×10¹⁶cm^-3 for the 532 nm laser and from 14100 to 12500 K and 2.4×10¹⁶ to 1.9×10¹⁶cm^-3 for the 355 nm laser.

The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e²n_cτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, n_c the density of the conduction electrons, and τ the relaxation time. The density n_c depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

Copper and its alloys with high electrical and thermal conductivity are a group of widely used engineering materials in numerous applications. In order to improve the tribological properties of copper substrate, an electroplating nickel layer was firstly deposited on copper substrate, subsequently these electroplated specimens were treated by slurry pack cementation process at 900°C for 12 h using a slurry mixture composed of TiO₂ as titanizing source, pure Al powder as aluminzing source and also a reducer for titanizing, an activator of NH₄Cl and albumen (egg white) as cohesive agent. The effect of Al content on the microstructure and the properties of the coating has been studied. The results showed that an intermetallic Ni-Ti (Al) compound/Ni graded layer was formed on copper substrate after slurry pack cementation process. With the rise of Al content in slurry mixture, the microhardness of the graded coating increased and the friction coefficient decreased from 0.35 to 0.18, at the same time, the slurry pack process gradually transited from the titanizing process to an aluminizing one. Correspondingly the main phases of the coating were changed from Ni-Ti intermetallic compounds into Ni-Al ones.

In order to study the fatigue damage formation process of ultrafine grained copper, fatigue tests were carried out for two samples: oxygen-free copper and deoxidized low-phosphorous copper. After the processing by equal channel angular pressing (ECAP) using eight passes, equiaxed grains with an average size of 300 nm were formed for both the samples. The formation behavior of surface damage was monitored. The effects of trace impurities on surface damage formation behavior were discussed from the viewpoints of change in surface morphological feature during stressing.

A fully dense electrodeposited microcrystalline copper with nano-scale twins was synthesized by electrodeposition. The microstructure of this copper was analyzed X-ray diffractometer (XRD) and by transmission electron microscopy (TEM). The grains of mean size about 2mm were divided by high density of growth twins with mean lamellar thickness of about 90 nm. Tensile tests at different strain rates and room temperature showed that the strength increased from 379 MPa to 458 MPa with strain rate increasing from 10^-5 s^-1 to 0.1 s^-1. The elongations to fracture were in the range of 13.6~15.5%. So this Cu has good combination of strength and ductility. The strengths are much higher than that determined by Hall-Petch relation with the same grain size, which means that twin boundaries are effective in blocking dislocation motion. The strain rate sensitivity and activation volume estimated from the flow stress versus strain curves was 0.016 and 84 b³~69b³, respectively. Such a large activation volume indicates that the deformation of this copper was controlled by dislocation process.

We have developed a simplified molecular-dynamical model for simulating ablation of solid surfaces by laser pulses, and specifically investigated expansion of Cu cloud in vacuum vaporized on the surface, showing that the angular distributions of the plume depend on the shape of the laser spot on the surface. In particular, experimentally observed flipover effects have been obtained, and an adiabatic constant determined from our simulations via an adiabatic expansion model agrees well with previous measurements.

The LPG gas sensing response of polyethylene oxide (PEO)-Cu (Cu = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 wt. %) composite thick films prepared on alumina substrates by using novel screen printing technique are reported in present paper. The gas sensing responses of films were tested at 1000 ppm of LPG by using home-built static gas sensing system [between room temperature - 50 °C]. A very high value of SF = 1400 was obtained at an optimum temperature of 47 °C for a film with Cu = 0.7 wt.%. Further, better LPG sensing response, SF = 700 was obtained at low operating temperature = 36 °C for a film with Cu = 0.2 wt. %. The LPG sensing responses of the films were found to be strongly influenced by concentration level of Cu additive.

Electron beam physical vapor deposition (EBPVD) is being used in coating components for many applications such as for producing nanostructures and integrated circuits (ICs) coating in electronic industry. In this work, copper was deposited on the SiO₂/p-type Si(100). Thin film characteristics are investigated by scanning electron microscopy and X-ray diffraction (XRD). Then oxidation behavior of deposits was evaluated by Dektak Surface Profiler and weight gain method at 200 and 300°C. Results showed that thin film copper deposited by EBPVD has better oxidation characteristics in comparison with copper foil.

Separation and recovery of valuable metals including silver (Ag) and copper (Cu) from electronic waste mixtures are of great economic and environmental importance. Recent years, semiconductor photocatalysts have been investigated intensively for the removal of Ag from wastewater. Few studies have been carried out on the effect of pH and co-exist metal ions such as Cu on Ag. In this study, ZnO and TiO₂ were applied as photocatalysts to target on the selective recovery Ag and Cu from its mixtures under UV light. The effects of pH, catalyst, ethylene-diamine tetraacetic acid (EDTA) on the Ag and Cu photo-reduction were studied. Modeling of Ag${}^{+}$ and Cu${}^{2+}$ with and without EDTA distribution together with metal precipitations was plotted against pH to understand the chemistry involved in photocatalysis. Experimental results showed that Ag${}^{+}$ photo-reduction was nearly completed by ZnO and TiO₂ to Ag metal, while Cu${}^{2+}$ photo-reduction to Cu₂O only occurs by ZnO in the presence of EDTA. This work illustrates that semiconductor photocatalysts are suitable for selective recovery of Ag and Cu from wastewaters.

Nanocrystalline Co${}_{0.5-x}$Zn${}_{0.5}$Cu${}_x$Fe₂O₄ spinel ferrites were prepared by autocombustion method with citric acid as fuel. Paramagnetic divalent copper ions substituted in place of ferromagnetic cobalt ions resulted in the modifications of structural and magnetic properties of the system. All samples were characterized with X-ray diffraction technique for structure determination. Crystallite sizes were calculated using Williamson–Hall plot and size–strain plots. Cation distribution and all other structural parameters were presented. Transmission electron microscopy measurements were done for x = 0 and x = 0.15 and they showed well-developed spherical particles with average sizes of 35 nm and 48 nm. Morphological studies were performed and grain growth was observed to be increased with copper concentration. EDAX measurements revealed the stoichiometric proportions of the samples as per the chemical composition. Mid-IR spectroscopy was used to characterize the spinel phase and displayed two characteristic absorption bands in all samples with a slight shift. M–H loops were recorded using vibrating sample magnetometer at room-temperature and highest saturation magnetization was observed to be 50.2 emu/g for the base (x = 0) sample. Magnetocrystalline anisotropy was discussed with the help of magnetocrystalline anisotropy constant K₁.