Single Copper Research Articles

Anisotropy-Related Machining Characteristics in Ultra-Precision Diamond Cutting of Crystalline Copper

Deformation behavior at grain levels greatly affects the machining characteristics of crystalline materials. In the present work, we investigate the influence of material anisotropy on ultra-precision diamond cutting of single crystalline and polycrystalline copper by experiments and crystal plasticity finite element simulations. Specifically,diamond turning and in situ SEM orthogonal cutting experiments are carried out to provide direct experimental evidence of the material anisotropy-dependent cutting results in terms of machined surface morphology and chip profile. Corresponding numerical simulations with the analysis of built stress further validate experimental results and reveal the mechanisms governing the material anisotropy influence.The above findings provide insight into the fabrication of ultra-smooth surfaces of polycrystalline metals by ultra-precision diamond turning.

NotchPUF: Printed Circuit Board PUF Based on Microstrip Notch Filter

Physical Unclonable Functions (PUFs) are primitives that are designed to leverage naturally occurring variations to produce a random bitstring. Current PUF designs are typically implemented in silicon or utilize variations found in commercial off-the-shelf (COTS) parts. Because of this, existing designs are insufficient for the authentication of Printed Circuit Boards (PCBs). In this paper, we propose a novel PUF design that leverages board variations in a manufactured PCB to generate unique and stable IDs for each PCB. In particular, a single copper trace is used as a source of randomness for bitstring generation. The trace connects three notch filter structures in series, each of which is designed to reject specific but separate frequencies. The bitstrings generated using data measured from a set of PCBs are analyzed using statistical tests to illustrate that high levels of uniqueness and randomness are achievable.

Effects of Ethanol Blending on the Formation of Soot in n-Heptane/Air Coflow Diffusion Flame

Laminar diffusion flame was used to study the effect of ethanol on n-heptane flame in terms of the morphology and microstructure of soot under atomization combustion. For the same carbon mass flux at the outlet of the burner, the ratio of ethanol doping in n-heptane was changed, and the soot was collected from the axial positions of the flame at different heights using the thermophoresis probe method. The results showed that the flame height increased significantly with the increasing ratio of ethanol doping. When the ratio of ethanol and n-heptane (CE/CN) was 1.5, the flame height increased by 10 mm compared with that of pure n-heptane flame. Besides, the temperature in the center of the flame decreased with the increasing ratio of ethanol doping, but the temperature in the low position was higher than that in the pure n-heptane flame, and the temperature in the high position was lower than that in the pure n-heptane flame. However, the flame temperature was the highest when the proportion of ethanol in the mixture was greater than that of n-heptane. The temperature at the flame center decreased with the increasing ratio of ethanol doping, while the temperature at the flame edge increased with the ratio. The primary particle size of soot (soot size hereafter) in all working conditions increased with the increase of flame height, which was in line with the general growth law of soot. Moreover, the soot size at the same height decreased with the increasing ratio of ethanol doping, and this trend was most obvious at the flame height of 20 mm and 30 mm. Compared with pure n-heptane, when CE/CN was 1.5, the soot size at 20 mm and 30 mm decreased by an average of 34.83%, indicating that ethanol could inhibit the surface growth of soot particle. Furthermore, the density of soot particles collected by a single copper net decreased significantly, indicating that ethanol could reduce the production amount of soot.

Modulating Location of Single Copper Atoms in Polymeric Carbon Nitride for Enhanced Photoredox Catalysis

Introducing single-atom metals (SAMs) is a promising strategy to improve photocatalysis of polymeric carbon nitride (PCN), but current studies are limited to loading SAMs on the surface of PCN to s...

Copper-doped induced ferromagnetic half-metal zirconium diselenide single crystals

Two-dimensional (2D) magnetic layered materials have attracted considerable attention in memory storage devices due to their exciting magnetic ordering. Herein, the electronic and magnetic properties of high-quality single crystals zirconium diselenide and copper (Cu)-doped zirconium diselenide as grown via chemical vapor transport technique combined with first principle density functional theory calculations were investigated. A semimetallic state is recognized for Cu0.052Zr0.93Se2 as measured through resistance versus temperature measurements and angle resolved photoemission spectroscopy (ARPES). The magnetic measurement shows diamagnetic semiconducting behaviour for ZrSe2, whereas Cu0.052Zr0.93Se2 exhibits ferromagnetic character via applying perpendicular magnetic field. Cu0.052Zr0.93Se2 reveals the room temperature magnetic moment ∼0.0125 emu g−1, while the Curie temperature is ∼363.49 K. Furthermore, first principle density functional theory (DFT) calculations show energetically long range ferromagnetic ordering in a half-metallic Cu-doped ZrSe2, while a diamagnetic state in case of ZrSe2 agrees well with experiment results. These results suggest that due to strong interaction elements at the octahedral site of zirconium atoms when replaced by copper atoms, which can change the spin ordering of electrons and make zirconium vacancy, while their magnetic moment is increased. Very importantly the half-metallic character of Cu0.052Zr0.93Se2 promotes much spin polarized electrons around the Fermi level, suggesting significant potential in future memory devices and spintronic applications.

Effect of single and combined Cu, NaCl and water stresses on three Atriplex species with phytostabilization potential

Phytostabilization of metal enriched substrates in arid and semiarid areas depends on the use of metal-tolerant or metallophyte plants in order to decrease metal mobilization and dispersion. However, the co-occurrence of other abiotic restrictions on plant growth, such as drought and salinity calls for a new perspective for plant selection. Since components of salt and drought tolerance traits of halophytes are also present in metal stress, Atriplex species, typical of dry and salty soils, emerge as good candidates for phytostabilization. But in order to confirm this potential, it is necessary to explore specific responses to increasing copper, salt and water stress.In this study, we compared the effect of single and combined copper, NaCl and PEG- induced water stresses on growth parameters of the Chilean Atriplex atacamensis, European A. halimus and Australian A. nummularia under controlled hydroponic assays. Results showed that increasing copper had severe effects on root development of all three species, with subsequent effects on their shoot biomass. Salt stress effects were mostly osmotic, with a decrease in shoot fresh weight and water content, and PEG- induced water stress had no clear effect on growth of roots and shoots. Combination of copper with NaCl and PEG further decreased plant growth, but this effect varied among Atriplex species. This shows that growth of Atriplex species responds differently to each individual stress and that stressor combination causes an overall negative effects in their growth parameters.

A multi-GPU implementation of a full-field crystal plasticity solver for efficient modeling of high-resolution microstructures

In a recent publication (Eghtesad et al., 2018), we have reported a message passing interface (MPI)-based domain decomposition parallel implementation of an elasto-viscoplastic fast Fourier transform-based (EVPFFT) micromechanical solver to facilitate computationally efficient crystal plasticity modeling of polycrystalline materials. In this paper, we present major extensions to the previously reported implementation to take advantage of graphics processing units (GPUs), which can perform floating point arithmetic operations much faster than traditional central processing units (CPUs). In particular, the applications are developed to utilize a single GPU and multiple GPUs from one computer as well as a large number of GPUs across nodes of a supercomputer. To this end, the implementation combines the OpenACC programming model for GPU acceleration with MPI for distributed computing. Moreover, the FFT calculations are performed using the efficient Compute Unified Device Architecture (CUDA) FFT library, called CUFFT. Finally, to maintain performance portability, OpenACC-CUDA interoperability for data transfers between CPU and GPUs is used. The overall implementations are termed ACC-EVPCUFFT for single GPU and MPI-ACC-EVPCUFFT for multiple GPUs. To facilitate performance evaluation studies of the developed computational framework, deformation of a single phase copper is simulated, while to further demonstrate utility of the implementation for resolving fine microstructures, deformation of a dual-phase steel DP590 is simulated. The implementations and results are presented and discussed in this paper.

Insights into the effects of single and combined divalent copper and humic acid on the performance, microbial community and enzymatic activity of activated sludge from sequencing batch reactor

The performance, microbial community and enzymatic activity of activated sludge from four identical sequencing batch reactors (SBRs) were compared by treating synthetic wastewater under the single and combined divalent copper (Cu2+) at 20 mg/L and humic acid (HA) at 20 mg/L. Compared with the absence of Cu2+ and HA, the single HA slightly enhanced the oxygen uptake rate (OUR), the nitrification and denitrification rates and the activities of dehydrogenase, nitrifying enzymes and denitrifying enzymes, whereas the single Cu2+ had the opposite results. The combined Cu2+ and HA inhibited the OUR, nitrogen removal rate and enzymatic activity of activated sludge almost the same as the single Cu2+. The single HA had no obvious effect on the balance between the microbial oxidative stress and antioxidant activity. However, the variations of microbial reactive oxygen species production, peroxidase activity, catalase activity, superoxide dismutase activity, and lactate dehydrogenase release demonstrated that the combined Cu2+ and HA and single Cu2+ produced obvious toxicity to microorganisms in activated sludge. The microbial richness and diversity had some obvious changes under the single and combined Cu2+ and HA. The relative abundances of Nitrosomonas, Nitrospira and some denitrifying genera (e.g. Zoogloea, Dokdonella, Denitratisoma, Flavobacterium and Thermomonas) under the combined Cu2+ and HA were less than those under the single Cu2+.

Copper-Catalyzed Photoinduced Enantioselective Dual Carbofunctionalization of Alkenes.

A photoinduced, copper-catalyzed, highly enantioselective dual alkylation/arylation and alkynylation of alkene is reported. A single chiral copper(I) complex serves to enable photoredox catalysis and induce enantioselectivity during the reaction. This reaction couples three different components under mild reaction conditions, exhibits a broad substrate scope, and provides facile access to chiral propargylic systems, including those featuring valuable fluorinated substituents.

Crystal anisotropy-dependent shear angle variation in orthogonal cutting of single crystalline copper

Shear deformation that dominates elementary chip formation in metal cutting greatly relies on crystal anisotropy. In the present work we investigate the influence of crystallographic orientation on shear angle in ultra-precision orthogonal diamond cutting of single crystalline copper by joint crystal plasticity finite element simulations and in-situ experiments integrated in scanning electron microscope. In particular, the experimental cutting conditions including a straight cutting edge are the same with that used in the 2D finite element simulations. Both simulations and experiments demonstrate a well agreement in chip profile and shear angle, as well as their dependence on crystallography. A series of finite element simulations of orthogonal cutting along different cutting directions for a specific crystallographic orientation are further performed, and predicated values of shear angle are used to calibrate an extended analytical model of shear angle based on the Ernst–Merchant relationship.

Exposure to multiple air pollutants and the incidence of coronary heart disease: A fine-scale geographic analysis

Geographical variations in cardiovascular disease rates have been linked to individual air pollutants. Investigating the relation between cardiovascular disease and exposure to a complex mixture of air pollutants requires holistic approaches. We assessed the relationship between exposure to multiple air pollutants and the incidence of coronary heart disease (CHD) in a general population sample. We collected data in the Lille MONICA registry (2008–2011) on 3268 incident cases (age range: 35–74). Based on 20 indicators, we derived a composite environmental score (SEnv) for cumulative exposure to air pollution. Poisson regression models were used to analyse associations between CHD rates on one hand and SEnv and each single indicator on the other (considered in tertiles, where T3 is the most contaminated). We adjusted models for age, sex, area-level social deprivation, and neighbourhood spatial structure. The incidence of CHD was a spatially heterogeneous (p=0.006). There was a significant positive association between SEnv and CHD incidence (trend p=0.0151). The relative risks [95%CI] of CHD were 1.08 [0.98–1.18] and 1.16 [1.04–1.29] for the 2nd and 3rd tertile of SEnv exposure. In the single pollutant analysis, PM10, NO2, cadmium, copper, nickel, and palladium were significantly associated with CHD rates. Multiple air pollution was associated with an increased risk of CHD. Single pollutants reflecting road traffic pollution were the most strongly associated with CHD. Our present results are consistent with the literature data on the impact of road traffic on the CHD risk in urban areas.

On physical basis of local current overload in vehicle electric mains

Introduction. The data presented in the article indicate that the problem of improving fire safety of vehicles is very topical. The aim of the article is to develop a scientifically based method for studying a copper conductor with signs of local current overload in order to establish the cause of its damage during a fire-technical examination. Materials and methods . The studies were carried out with a JSM-6390LV scanning electron microscope with an add-on device for energy dispersive microanalysis. The fracture surfaces of the copper conductor were analyzed without preliminary sample preparation. Theoretical foundations (theory and calculations). An updated model of ultimate stress-strain state of inelastic pure bending of a copper rod of circular cross section has been developed. The solution has been reduced to simple rating formulas that allow us to evaluate the bearing capacity of flexible single copper conductors. The applicability of the developed mathematical model during the fire-technical examination is shown by a specific example. Results and discussion . Examples of vehicle fires caused by critical bending of the wiring harness are given in the article. Experimental data confirmed that the copper conductor under current overload melts in the critical bend area. The need to clarify the wording of the term “local current overload” is justified. Conclusion. A method for determining the critical bending of a copper conductor at which its melting can occur under electric current has been proposed. The data presented in the article can be used by experts in an expert study of copper conductors from fire sites to establish the mechanism of their damage and, ultimately, the cause of a vehicle fire.

DFT analysis elementary reaction steps of catalytic activity for ORR on metal-, nitrogen- co-doped graphite embedded structure

Metal-nitrogen coordinated graphite coordination structures are becoming more and more attractive for its novel catalytic activity in oxygen reduction reaction (ORR) at the fuel cells. In this work, single copper atom on graphitic carbon nitride acting as electrocatalyst for ORR have been investigated by using the density functional theory method. Our study results that the Cu site is the active center for all the possible elementary steps of the ORR. Further studies the elementary reaction steps are used to explore the underlying mechanisms to gain insights into ORR. Both the O2 dissociation and O2 hydrogenation paths are probably to ORR on the CuN4-Gra surface. All the possible elementary reaction steps for the ORR are exothermic with small reaction barriers (less than 1.98 eV) for O2 hydrogenation. Meanwhile, with large reaction barrier (3.16 eV) for O2 dissociation to go through the rate-limiting steps. The Gibbs free energy for each elementary step of ORR is used to clarify which path determine the ORR/OER on the CuN4 co-doped graphene. Scaling relation and surface phase diagram are obtained by calculated Gibbs free energy of intermediates at surface active sites with various adsorption species. The different working potentials are also considered for the studied catalysts, as the overpotential of ORR is also an important indexes of the catalytic activities of the catalyst, we calculated the overpotential for each active site on the structures and determined the minimum overpotential for ORR.

Methane activation by a single copper center in particulate methane monooxygenase: A computational study

The coordinates of the copper site in the C subunit of particulate methane monooxygenases pMMO are used to optimize simplified structures of possible intermediates in the conversion of methane and dioxygen into methanol and water. The transition states for the hydrogen atom abstraction from methane or ethane by a copper oxo intermediate are located and found to have an energies consistent with a process occurring under ambient conditions and with the correct kinetic isotope effect. The fact that hydrogen atom abstraction from methanol has even a lower barrier indicates that the enzyme system utilizes other means of achieving selectivity for methane over methanol oxidation.

Amendment in sensing response of Single Walled Carbon nanotube (SWCNT) towards ammonia gas with copper phthalocyanine functionalization

The sensing of composite of two p-type materials; Single Walled Carbon nanotube (SWCNT) and Copper Phthalocyanine (CuPc) towards ammonia gas is studied. Maximum increase in response of SWCNT after CuPc functionalization has been found to be ≈ 56% with 83% increase in saturation responses. The average crystallite size corresponding to characteristic CuPc has been decreased with SWCNT doping by 44% with negligible shift in its characteristic peak corresponding to β phase. The successive intercalation of CuPc and strong π-π stacking interaction with SWCNT has been confirmed in structural, surface and spectroscopic results of SWCNT doped CuPc.

Performance enhancement of the triboelectric energy harvester by forming rough surface polymer film using poly-dimethyl-siloxane +25 wt% water solution

In this paper, an experimental study of performance enhancement of the triboelectric energy harvester (TEH) by using rough surface poly-dimethyl-siloxane (PDMS) polymer film as one of the tribo layer has been presented. A parallel plate vertical-separation mode type TEH has been fabricated with rough surface morphology PDMS polymer film. Rough surface morphology is formed by spin coating diluted PDMS formed of Dow Corning 10:1 PDMS solution +25wt% water on the FR4 PCB board. FR4 substrate with single side copper clad has been utilised to realise bottom electrode. A cantilever structure is implemented utilising 50 μm thin copper foil, as top electrode, attached beneath a Kapton film. The device performance measurements showed the peak output voltage of 39.69 V and peak to peak voltage of 53.75 V. As a proof of concept, self-powered light emitting diodes (LED) system with 26 serially connected LEDs has been demonstrated with manual tapping on the TEH device.

Asymmetric synthesis of γ-chiral borylalkanes via sequential reduction/hydroboration using a single copper catalyst.

The synthesis of γ-chiral borylalkanes through copper-catalyzed enantioselective SN2′-reduction of γ,γ-disubstituted allylic substrates and subsequent hydroboration was reported. A copper–DTBM-Segphos catalyst produced a range of γ-chiral alkylboronates from easily accessible allylic acetate or benzoate with high enantioselectivities up to 99% ee. Furthermore, selective organic transformations of the resulting γ-chiral alkylboronates generated the corresponding γ-chiral alcohol, arene and amine compounds.

Comparison of electrical wire explosion characteristics of single wire and wire array in air

In this paper, discharge characteristics of a planar copper wire array explosion driven by a microsecond pulsed current source (500 J stored energy) in atmospheric air medium were studied. Meanwhile, controlled experiments were performed with single wire cases. With a 2 cm distance between electrodes, 2-16 copper wires with a diameter of 100 μm were selected to form planar copper wire arrays, and single copper wires with diameter of 50-400 μm were selected for comparisons. Load voltage, circuit current and light radiation intensity were measured. Electric power and deposited energy were calculated. The experimental results show that for the single wire case, with the increase of mass (diameter), the process of vaporization and ionization become slower, manifested as a delay of the voltage peak and an increase of the full width half maximum (FWHM) of the voltage pulse from 0.07 μs to 0.64 μs. In contrast, although the explosion time of wire array load was delayed with the increase of mass, the duration of vaporization and ionization did not change significantly with a FWHM of 0.11 ± 0.01 μs. In addition, the deposited energy of wire array load before breakdown was lower than that of single wire load with the same mass. As for the optical radiation intensity, under three cases with the same mass, the peak intensity of wire array explosion is about 28%, 49% and 52% higher than that of single wire explosion. There may be two reasons which cause the difference between the single wire load and wire array load. First, the larger specific surface area of the wire array load makes faster phase transitions. Second, the development of thermal or magnetohydrodynamics for the two kinds of loads was different, which should be responsible for the differences in energy deposition and optical emission.

Dynamic single-site polysulfide immobilization in long-range disorder Cu-MOFs.

The structural transformation of MOFs in a polysulfide electrode process is poorly understood. We report the electrochemical amorphization of Cu3(BTC)2 MOFs in polysulfide electrolyte. We unveil the dynamic single-site polysulfide immobilization at the interconvertible Cu2+/Cu+ cation centres upon polysulfide adsorption and desorption, along with the reversible distortion of the Cu-O square planar unit.

Effect of carbon nanotube on radiation resistance of CNT-Cu nanocomposite: MD simulation

Carbon nanotubes are one of the candidates for the reinforcement of metals for numerous applications. In this study, the effect of CNT on the primary radiation damage of CNT-Cu nanocomposite was investigated using molecular dynamics simulations. The simulations were performed by considering primary knock-on atom with 3 and 6 keV kinetic energies in the radial velocity direction (perpendicular to the cylinder axis) at various distances from the armchair CNT with (28, 28) chirality. Equivalent simulations in the single copper crystal and crystal containing cylindrical nanovoid (“CNV”) were performed for comparison. The results represent an improvement in radiation tolerance of copper composed with CNT nanofiller. In this material, CNT not only plays a sink role for point defects, but also it acts as a barrier to extend the displacement cascade. Some fluctuations in the number of the bulk vacancy around CNT-Cu interface were observed. The reason for this behavior was discussed.