Conductivity Of Cu Research Articles

Mixed Cu2 Se Hexagonal Nanosheets@Co3 Se4 Nanospheres for High-Performance Asymmetric Supercapacitors.

Rational designing and constructing multiphase hybrid electrode materials is an effective method to compensate for the performance defects of the single component. Based on this strategy, Cu2 Se hexagonal nanosheets@Co3 Se4 nanospheres mixed structures have been fabricated by a facile two-step hydrothermal method. Under the synergistic effect of the high ionic conductivity of Cu2 Se and the remarkable cycling stability of Co3 Se4 , Cu2 Se@Co3 Se4 can exhibit outstanding electrochemical performance as a novel electrode material. The as-prepared Cu2 Se@Co3 Se4 electrode displays high specific capacitance of 1005 F g-1 at 1 A g-1 with enhanced rate capability (56 % capacitance retention at 10 A g-1 ), and ultralong lifespan (94.2 % after 10 000 cycles at 20 A g-1 ). An asymmetric supercapacitor is assembled applying the Cu2 Se@Co3 Se4 as anode and graphene as cathode, which delivers a wide work potential window of 1.6 V, high energy density (30.9 Wh kg-1 at 0.74 kW kg-1 ), high power density (21.0 Wh kg-1 at 7.50 kW kg-1 ), and excellent cycling stability (85.8 % after 10 000 cycles at 10 A g-1 ).

Boosting the Tunable Microwave Scattering Signature of Sensing Array Platforms Consisting of Amorphous Ferromagnetic Fe2.25Co72.75Si10B15 Microwires and Its Amplification by Intercalating Cu Microwires.

The following work addresses new configurations of sensing array platforms that are composed of Co-based amorphous ferromagnetic microwires (MWs) to obtain an enhanced modulation of the microwave scattering effects through the application of low strength DC or AC magnetic fields. An amorphous MW is an ultrasoft ferromagnetic material (coercivity ~0.2 Oe) with a circumferential magnetic anisotropy that provides a high surface sensitivity when it is subjected to an external magnetic field. Firstly, microwave scattering experiments are performed as a function of the length and number of MWs placed parallel to each other forming an array. Subsequently, three array configurations are designed, achieving high S21 scattering coefficients up to about −50 dB. The influence of DC and AC magnetic fields on S21 has been analyzed in frequency and time domains representation, respectively. In addition, the MWs sensing array has been overlapped by polymeric surfaces and the variations of their micrometric thicknesses also cause strong changes in the S21 amplitude with displacements in the frequency that are associated to the maximum scattering behavior. Finally, a new concept for amplifying microwave scattering is provided by intercalating Cu MWs into the linear Co-based arrays. The designed mixed system that is composed by Co-based and Cu MWs exhibits a higher S21 coefficient when compared to a single Co-based MW system because of higher electrical conductivity of Cu. However, the ability to modulate the resulting electromagnetic scattering is conferred by the giant magneto-impedance (GMI) effects coming from properties of the ultrasoft amorphous MWs. The mixed array platform covers a wide range of sensor applications, demonstrating the feasibility of tuning the S21 amplitude over a wide scattering range by applying AC or DC magnetic fields and tuning the resonant frequency position according to the polymeric slab thickness.

Investigation of Counterflow Microchannel Heat Exchanger with Hybrid Nanoparticles and PCM Suspension as a Coolant

The effect of the hybrid suspension on the intrinsic characteristics of microencapsulated phase change material (MEPCM) slurry used as a coolant in counterflow microchannel heat exchanger (CFMCHE) with different velocities is investigated numerically. The working fluid used in this paper is a hybrid suspension consisting of nanoparticles and MEPCM particles, in which the particles are suspended in pure water as a base fluid. Two types of hybrid suspension are used (Al2O3 + MEPCM and Cu + MEPCM), and the hydrodynamic and thermal characteristics of these suspensions flowing in a CFMCHE are numerically investigated. The results indicated that using hybrid suspension with high flow velocities improves the performance of the microchannel heat exchanger while resulting in a noticeable increase in pressure drop. Thereupon, it causes a decrease in the performance index. Moreover, it was found that the increment of the nanoparticles’ concentration can rise the low thermal conductivity of the MEPCM slurry, but it also leads to a noticeable increase in pressure drop. Furthermore, it was found that as the thermal conductivity of Cu is higher than that for Al2O3, the enhancement in heat transfer is higher in case of adding Cu particles compared with Al2O3 particles. Therefore, the effectiveness of these materials depends strongly on the application at which CFMCHE is employed.

Effects of Ni content on microstructure and properties of aged Cu−0.4Be alloy

Abstract The effects of Ni content (0−2.10 wt.%) on the precipitated phase, strength and electrical conductivity of Cu−0.4wt.%Be alloy were investigated, and the influencing mechanism was analyzed. The results showed that the addition of Ni promoted the precipitation of strengthening phase in the alloy and remarkably enhanced the strengthening effect. When the Ni content was increased from 0 to 2.10 wt.%, the strength of the aged alloy initially increased and then decreased, and approached the maximum when the Ni content was 1.50 wt.%. The peak-aging parameters of the alloy containing 1.50 wt.% Ni were the aging temperature of 400 °C and the aging time of 60 min, where the tensile strength and yield strength of the aged alloy were 611 and 565 MPa, respectively, which were 2.8 times and 6.1 times those of the alloy without Ni. The electrical conductivity of the alloy with Ni increased with the aging time, and decreased with the increase of Ni content. With an increase of the aging time at 400 °C, phase transition sequence of the Cu−0.4Be−1.5Ni alloy was γ″ phase →γ′ phase →γ phase. For the aging time of 60 min, a large number of dispersed nano-scale coherent γ″ phase and γ′ phase formed in the alloy with a remarkable strengthening effect, which was mainly responsible for the high strength of the alloy.

3D heterostructure of 2D Y-doped Cu(OH)2 nanosheet supported by nickel foam as advanced electrodes for high performance supercapacitor

Herein, the 3D structure of 2D Y-doped Cu(OH)2 nanosheet supported by nickel foam was successfully synthesized by simple solvent thermal reaction. Interwoven nanosheet structures are anchored to the nickel foam skeleton, which makes full use of its electrochemical active sites and speeds up ion and electron transport. Meanwhile, Y-doped can also improve the inherent conductivity of Cu(OH)2 electrode materials. According to the electrochemical test, the specific capacitance of Y-doped Cu(OH)2/NF was 2775 F/g at 1A/g, which shows good charge and discharge rate and cycling stability (86.2% retention over 6000 cycles). In addition, the Y-doped Cu(OH)2/NF//AC device also provides good specific capacitance (192.53 F/g at 1A/g) and has an energy density of 60.16 Wh/kg at a power density of 749.98 W/kg.

On the investigation of reuse potential of SnPb-solder affected copper subjected to work-hardening and thermal ageing

The reuse potential of SnPb-solder affected old/waste copper is investigated under the influence of work hardening and thermal treatments. In fact, the urge of using old copper to manufacture new components necessitates useful characterization of various properties to explore its reuse potential. In this context, a number of physico-mechanical properties of interest, namely, hardness, conductivity, thermal stability, structure, etc. are chosen here to characterize the solder-affected copper materials as well as analyze their possible changes/improvements under the influence of work-hardening and thermal treatments. Since the old/waste copper usually contains little amount of lead and tin, three additional sample materials, such as, copper ingots, copper‑tin alloy, and copper‑lead alloy are taken into consideration to ascertain the influence of individual solder elements on the properties of the copper alloy. It is observed that addition of trace amount of tin and lead can significantly influence micro-hardness, conductivity, thermal capacity, etc. Micro-hardness values of all four sample materials have been found to be increasing in curvilinear pattern with the rise of cold-rolling level up to 50– 55% and then get flatten, and cold-rolled work-hardening level of ~35% is found to be a critical deformation level where the hardness of CuPb alloy supersedes pure Cu and Cu-Sn-Pb alloy supersedes CuSn alloy. Electrical conductivity of Cu falls drastically with the addition of only about 1% Sn or 1% Pb, which increases little initially after cold-rolled deformation up to ~35% and start falling again with the rise of deformation levels. Shifting of endothermic peak has occurred and thereby recrystallization temperature of Cu is transformed as an effect of alloying due to inclusion of SnPb-solder in Cu as well as work hardening. Micrographs have confirmed the structural changes responsible for the variation of electro-mechanical properties.

Effect of Microstructure on Strength and Electrical Conductivity of Cu–3.8wt%Zr Alloy Wires

Effect of Microstructure on Strength and Electrical Conductivity of Cu–3.8wt%Zr Alloy Wires

Cu–Ni–Si合金板の強度と導電率に及ぼす極低温高速圧延の影響

Cu–Ni–Si合金板の強度と導電率に及ぼす極低温高速圧延の影響

Enhancing the thermoelectric performance of Cu–Ni alloys by introducing carbon nanotubes

High power factor and low thermal conductivity are imperative to maximize the energy conversion efficiency of thermoelectric materials. Constantan (Cu–Ni alloy), a widely-used material for thermocouples, has higher power factor (∼12000 μW m−1 K−2 at 950 K) [Mao et al. 2015] than the classic Bi2Te3-based thermoelectric materials (∼4500 μW m−1 K−2 at 300 K) [Poudel et al. 2008]. However, the high thermal conductivity restricts its thermoelectric performance. In this work, we demonstrate that, the thermal conductivity of Cu–Ni alloy can be effectively reduced from 48.1 to 9.6 W m−1 K−1 at 873 K by introducing carbon nanotubes (CNTs), and the thermoelectric performance is remarkably improved with the figure of merit (zT) being up to 0.41, an enhancement of about 141% over the pristine Cu–Ni alloy. Negative correlation between the total thermal conductivity of hybrid composite and the specific surface area of CNTs is further identified. The thermal conductivity suppression mechanism is ascribed to the introduction of both porous structures and carbon-nanotube-metal interfaces. Our studies provide a promising and general strategy to enhance the thermoelectric properties of materials with high thermal conductivity.

Fabrication and Radio Frequency Properties of 3-GHz SRF Cavities Coated with MgB2

Magnesium diboride (MgB2) is considered a potential material for superconducting radio frequency cavities. MgB2-coated Cu cavity will allow for a higher operational temperature than a bulk Nb cavity because of the higher transition temperature of MgB2 and the high thermal conductivity of Cu. Using the hybrid physical chemical vapor deposition technique, MgB2 coatings were successfully achieved on the inner wall of 3-GHz Cu cavities. The surface and superconducting properties of the coatings were characterized using small samples on Cu plugs mounted at different locations of mock cavities. RF measurement of a MgB2-coated single-cell 3-GHz test cavity was carried out, and it showed superconducting transition at 36 K. The quality factor of this test cavity was lower than expected due to poor connectivity and inclusion of Mg–Cu alloy in the MgB2 coating.

Thermal performance and stress analysis of heat spreaders for immersion cooling applications

This paper numerically investigates the thermal performance and stress analysis of enhanced Copper (Cu) spreaders for nucleate boiling immersion cooling of high-power electronic chips. The proposed spreaders take advantage of the remarkably high thermal conductivity of Cu (low thermal spreading resistance) and enhanced nucleate boiling heat transfer of dielectric liquid PF-5060 on Microporous Cu (MPC) coating. The spreaders topmost surfaces are smooth (Ra = 0.21 μm), roughened (Ra = 1.44 μm), and coated with an 80-μm thick MPC layer. The spreader thicknesses (δCu) varied between 1.6 and 3.2 mm, the chip side length (LC) between 10 and 30 mm, and chip thickness (δC) between 200 and 500 μm. The numerical results show that MPC spreaders remove the most significant quantity of thermal power (58–270 W) dissipated by underlying chips compared to plane (smooth and roughened) Cu spreaders (28–210 W). The MPC spreaders have the least total thermal resistance, and the corresponding maximum chip temperature (Tc,max) is low (67 °C) and in a considerable safe margin from the temperature limits set by the high-power chip industry (85–120 °C). The maximum Von-Mises stress (70 MPa) on the underlying chips cooled by MPC spreaders is 1/100 of the allowable yield strength of silicon (7 GPa) but much higher than those cooled by plane Cu spreaders (40–44 MPa). The total displacement or deformation due to the temperature gradient is 22 μm and 4 μm at the top face of the spreader and at the chip-spreader interface, respectively, for MPC spreaders cooling 500 μm thick 10 × 10 mm underlying chips. The total displacement is much less (<0.5 μm) for all chips cooled by plane Cu spreaders or larger footprint area underlying chips (LC = 20–30 mm) cooled by MPC spreaders. These numerical results demonstrate the capability of MPC spreaders for immersion cooling by nucleate boiling of dielectric liquid PF-5060 of high-power electronic chips.

Effect of cryorolling on microstructure and property of high strength and high conductivity Cu−0.5wt.%Cr alloy

Abstract Cu−0.5wt.%Cr alloy with high strength and high conductivity was processed by cryorolling (CR) and room temperature rolling (RTR), respectively. The microstructure, mechanical property and electrical conductivity of Cu−0.5Cr alloy after CR/RTR and aging treatment were investigated. The results indicate that obvious dislocation entanglement can be observed in matrix of CR alloy. The Cr particles in the alloy after CR and aging treatment possess finer particle size and exhibit dispersive distribution. The peak hardness of CR alloy is HV 167.4, significantly higher than that of RTR alloy. The optimum mechanical property of CR alloy is obtained after aging at 450 °C for 120 min. The conductivity of CR Cu−0.5Cr alloy reaches 92.5% IACS after aging at 450 °C for 120 min, which is slightly higher than that of RTR alloy.

High Performance Cu Matrix Nanocomposite Fabricated Through Spark Plasma Sintering of Cu and Cu-Coated CNT

In this paper, the effects of Cu coating of carbon nanotube (CNTs) as reinforcement on structural, microstructural, physical and mechanical properties of Cu–3 wt%CNT nanocomposite were investigated. CNTs were coated by Cu using the electroless technique for 1 and 2 h. Bulk nanocomposite samples were produced by spark plasma sintering of a mechanically milled powder mixture of Cu and CNT. Kinetic study showed a nucleation and growth mechanism for the Cu coating process. Microstructural characterization showed that the coated CNTs dispersed more homogeneously in the powder mixture. Results also revealed that 1 h coating of CNTs led to the higher relative density and thermal properties. The coating process increased 62 Brinell hardness (BHN) in hardness, 14% IACS in electrical conductivity for Cu–CNT nanocomposite. Transmission electron microscopy analysis showed a strong bonding between CNT and Cu matrix within the distinguishable interface. About 20 MPa increase in shear strength of nanocomposite was observed by 1 h coating of CNTs. Also, the fracture surfaces exhibit changes in the mode of fracture by well-bonded CNTs with the Cu matrix. The coefficient of thermal expansion and thermal distortion parameter revealed 12.7 ppm/k and 0.037 ppm.m/w for the sample including 1 h coated CNT, respectively.

First-Principles Study on the Cu/Fe Interface Properties of Ternary Cu-Fe-X Alloys.

The supersaturated Fe in Cu is known to reduce the electrical conductivity of Cu severely. However, the precipitation kinetics of Fe from Cu are sluggish. Alloying is one of the effective ways to accelerate the aging precipitation of Cu-Fe alloys. Nucleation plays an important role in the early stage of aging. The interface property of Cu/γ–Fe is a key parameter in understanding the nucleation mechanism of γ-Fe, which can be obviously affected with the addition of alloying elements. In this paper, first principles calculations were carried out to investigate the influence of alloying elements on the interface properties, including the geometric optimizations, interfacial energy, work of adhesion and electronic structure. Based on the previous research, 14 elements including B, Si, P, Al, Ge, S, Mg, Ag, Cd, Sn, In, Sb, Zr and Bi were selected for investigation. Results showed that all these alloying elements tend to concentrate in the Cu matrix with the specific substitution position of the atoms determined by the binding energy between Fe and alloy element (X). The bonding strength of the Cu/γ-Fe interface will decrease obviously after adding Ag, Mg and Cd, while a drop in interfacial energy of Cu/γ–Fe will happen when alloyed with Al, B, S, P, Si, Ge, Sn, Zr, Bi, Sb and In. Further study of the electronic structure found that Al and Zr were not effective alloying elements.

Effects of isovalent doping on the thermoelectric properties of environmentally-friendly phosphide Ag6Ge10P12

The electrical and thermal transport properties of the isovalent Cu- or Sn-doped ternary phosphide Ag6Ge10P12 have been investigated. Polycrystalline ingots of Cu- and Sn-doped Ag6Ge10P12 were grown by the melting method. In Ag6−xCuxGe10P12 (x ≤ 0.3) and Ag6Ge10−ySnyP12 (y ≤ 0.25), the lattice thermal conductivity accounted for ∼95% of the total thermal conductivity. The lattice thermal conductivity of Cu- and Sn-doped Ag6Ge10P12 decreased with increasing doping concentration. Because of the decrease of the lattice thermal conductivity, the figure of merit ZT value of Ag5.85Cu0.15Ge10P12 reached ∼0.26, which was ∼60% higher than that of non-doped Ag6Ge10P12. Although the lattice thermal conductivity of Sn-doped Ag6Ge10P12 decreased, the electrical resistivity of Sn-doped Ag6Ge10P12 increased, resulting in the ZT value of Sn-doped Ag6Ge10P12 monotonically decreasing. Therefore, Cu doping of Ag6Ge10P12 is the effective way to enhance the thermoelectric performance.

Surface chemical analysis of copper powder used in additive manufacturing

Additive manufacturing (AM) has during years gained significant interest owing to its endless component design possibilities. One of the most popular AM techniques is laser powder bed fusion (LPBF), which selectively melts metal powder layer‐by‐layer in a chamber with protective argon atmosphere. This technique is attractive for realizing Cu‐based products in which the high electrical conductivity of Cu is combined with component design possibilities. The successful use of Cu powder not only poses challenges owing to the high reflectivity and thermal conductivity of Cu but also involves the important concern of controlling the powder surface chemistry since the powder surface constitutes the main source of oxygen. It is of crucial importance to control the oxygen level in order to maintain good electrical conductivity and brazing ability of the AM‐fabricated Cu‐part. In LPBF, fine spherical powder with size of 10–60 μm is used, providing significant specific surface area, and this powder is also usually recycled several times, and hence, the role of powder surface chemistry is evident. Two kinds of copper powder with purities 99.70 and 99.95 wt% were analysed in both virgin and in used conditions after numerous printing cycles using LPBF. The powder was analysed by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). A clear difference between the two powder grades in terms of surface chemistry was observed. The oxide thickness and bulk oxygen content increased for both powder grades after recycling. The surface oxides under different conditions are identified and the effect of powder purity on the oxide formed is discussed.

Effect of Ni/Si mass ratio on microstructure and properties of Cu–Ni–Si alloy

Cu–Ni–Si alloys with 94 wt% Cu content and different Ni/Si mass ratios were prepared by hot pressing sintering, and then solution treatment and ageing treatment were also performed. Microstructure and phase composition along with electrical conductivity and hardness of the alloys under different treating condition was studied, and then the influence of Ni/Si mass ratio was discussed. Results showed that the as-sintered Cu–Ni–Si alloys mainly consisted of α-Cu matrix and some Ni31Si12 particles at the grain boundary as well as δ-Ni2Si phases inside the matrix. After solution treatment, most of the Ni–Si compounds decomposed, but δ-Ni2Si precipitates from the matrix after ageing treatment. With increasing Ni/Si mass ratio, the electrical conductivity and hardness of the alloys increases firstly and then decreases, while a highest combination of them achieved when the mass ratio of Ni/Si was 4:1. The effect of Ni/Si ratio on the electrical conductivity of Cu–Ni–Si alloys can be mainly ascribed to the residual content of Ni/Si in the Cu matrix after ageing treatment. When the mass ratio of Ni/Si is equal to the atomic ratio of δ-Ni2Si phase, most of the Ni and Si atoms would precipitates as δ-Ni2Si, and then the electrical conductivity reaches the highest value.

Effect of trace La on microstructure and properties of Cu–Cr–In alloys

The strength and conductivity of Cu–Cr–In alloys with trace La and different processing states were compared. Then, the influence of La on the structure and properties of the Cu–Cr–In alloy and the associated mechanisms were analyzed. The mechanical properties and microstructural evolution of the alloy were investigated via scanning electron microscopy, transmission electron microscopy, and tensile strength measurements. The results showed that the addition of 0.07wt% La to the Cu–Cr–In alloy had the effect of purifying the alloy melt and removing impurities, which improved the electrical conductivity of the alloy. However, the formation of rare earth intermetallic compounds reduced the tensile strength of the Cu–Cr–In–La alloy. After thermomechanical treatment, the Cu–Cr–In–La alloy reached a peak strength of 457 MPa and a conductivity of 85% IACS.

Improved tensile strength and electrical conductivity in Cu–Cr–Zr alloys by controlling the precipitation behavior through severe warm rolling

A Cu–Cr–Zr alloy was subjected to severe warm rolling, and the effects of processing temperature and strain on the precipitation and microstructures were systematically studied. The results show that the nucleation and growth of precipitates interact with the deformation-induced defects, and therefore, the distribution precipitates vary with the different warm rolling processes. This leads to a significant impact on mechanical and electrical properties. In detail, the size of the precipitates is coarser, but the number density is lower as the applied strain (after each annealing treatment) and temperature are higher. And therefore, the UTS is lower, but the electrical conductivity is higher in rolled sheets under higher strain and temperature. Moreover, the present process could improve the comprehensive properties of Cu–Cr–Zr alloys, and an excellent combination of high UTS of 586 MPa and good electrical conductivity of 78.2%IACS was achieved in the sample of RRA ~ 723 K. (The sample was subjected to intermediate annealing treatment at 723 K between each of two rolling passes.)

Mechanical, tribological and electrical properties of ZrB2 reinforced Cu processed via milling and high-pressure hot pressing

The present work investigates the effect of (0–10 wt%) ZrB2 reinforcement on densification, mechanical, tribological and electrical properties of Cu. The consolidation of Cu–ZrB2 samples was carried out using a hot press (temperature: 500 °C, pressure: 500 MPa, time: 30 min, vacuum pressure: 1.3 × 10-2 mbar). The bulk density of the hot-pressed Cu composites decreased from 8.84 g/cc to 8.16 g/cc and the relative density of samples lowered from 98.6% to 92.1% with the addition of ZrB2. The incorporation of hard ZrB2 (up to 10 wt%) improved the hardness of Cu (1.32–2.55 GPa). However, the yield strength and compressive strength of Cu composites increased up to 5 wt% ZrB2, and further addition of ZrB2 lowered its strength. The yield strength of Cu samples varied from 602 to 672 MPa and the compressive strength between ~834 and 971 MPa. On the other hand, the coefficient of friction (COF) (from 0.49 to 0.18) and wear rate (from 49.3 × 10-3 mm3/Nm to 9.1 × 10-3 mm3/Nm) of Cu–ZrB2 samples considerably decreased with the addition of ZrB2. Significantly low wear was observed with Cu-10 wt% ZrB2 (Cu-10Z) samples, which is 5.41 times less than pure Cu. As far as the wear mechanisms are concerned, in pure Cu, continuous chips (wear debris) were formed during sliding wear by plowing. Whereas the major amount of material loss was occurred due to the plowing mechanism with discontinuous and short chip formation for Cu–ZrB2 composites. The electrical conductivity of Cu–ZrB2 samples decreased from 75.7% IACS to 44.1% IACS. In particular, Cu with ZrB2 (up to 3 wt%) could retain the conductivity of 66.8% IACS. This study reveals that the addition of ZrB2 (up to 3 wt%) is advantageous to have a good combination of properties for Cu.