Conductivity Of Cu Research Articles

A flexible thermal interface composite of copper-coated carbon felts with 3d architecture in silicon rubber

Thermal interface materials (TIM) are key thermal management components to enhance the performance of electronic products, and how to improve thermal conductivity is a key issue to consider. As a high thermal conductivity material, it is difficult for copper to have both high thermal conductivity and high elasticity when filled into the polymer. In this paper, by growing copper nanoparticles on the surface of carbon felt (Cfelt), a three-dimensional interoperable thermally conductive copper network is formed with carbon fibers as the support, which makes the material both better thermally conductive and elastic at the same time. The vertical thermal conductivity of the prepared Cu-Cfelt/silicon rubber composite material reached 7.3230 W/mK. It is 23 times higher than pure silicon rubber(0.3130 W/mK), 18 times higher than Cu/silicon rubber composite (0.4120 W/mK) and 12 times higher than CFelt/silicon rubber composite (0.6200 W/mK), and successfully improves the thermal conductivity of the interface. The three-dimensional Cu network structure of the prepared Cu-CFelt/silicon rubber composite maximized the thermal conductivity of Cu, and the composite also showed excellent mechanical properties, indicating that the composite has broad application prospects in thermal management and other aspects.

C/C-(Hf0.5Zr0.3Ti0.2)C-W-Cu composites: Long-term ablation resistance based on active-passive protection at 2600 °C

Compared with the traditional C/C composites modified by ultra-high-temperature ceramics (C/C-UHTCs), those modified by metal/medium-entropy ceramics have excellent mechanical properties, thermophysical properties, and long-term ablation resistance. These composites have great potential towards improving the high-temperature resistance and service life of thermal protection systems for spacecraft. In this study, a new type of (Hf0.5Zr0.3Ti0.2)C-W-Cu cermet-modified C/C composites (C/C-(Hf0.5Zr0.3Ti0.2)C-W-Cu) was prepared at 1500 °C. Compared with C/C-UHTCs, the bending strength and fracture toughness of C/C-(Hf0.5Zr0.3Ti0.2)C-W-Cu increased by 70% and 110% to 364.25 MPa and 14.64 MPa·m1/2, respectively. Due to the high thermal conductivity of Cu and W, the thermal conductivity of this new composite was 106% higher than that of C/C-(Hf0.5Zr0.3Ti0.2)C (44.26 versus 21.53 W/m·K). Under a high heat flow of 4.18 MW/m2, this material exhibited very low mass and linear ablation rates (−0.163 mg/s and −0.193 μm/s, respectively). Active and passive protection occur during ablation due to the evaporative cooling of Cu, CuO, and WO3 as well as a dense outer oxide layer that inhibits oxygen diffusion. The internal oxide layer forms a Hf-Zr-Ti-C-O framework mingled with Ti-rich Ti-Hf-Zr-C-O and an unoxidised W-Cu structure, effectively reducing the osmotic oxygen content. This work provides a new direction for developing thermal protection materials capable of long-term service in ultra-high-temperature environments.

Effect of residual stress and microstructure on mechanical properties of sputter-grown Cu/W nanomultilayers

The combination of the high wear resistance and mechanical strength of W with the high thermal conductivity of Cu makes the Cu/W system an attractive candidate material for heat sinks in plasma experiments and for radiation tolerance applications. However, the resulting mechanical properties of multilayers and coatings strongly depend on the microstructure of the layers. In this work, the mechanical properties of Cu/W nanomultilayers with different densities of internal interfaces are systematically investigated for two opposite in-plane stress states and critically discussed in comparison with the literature. Atomistic simulations with the state-of-the-art neural network potential are used to explain the experimental findings of Young’s modulus and hardness. The results suggest that the microstructure, specifically the excess free volume associated with porosity and interface disorder interconnected with the stress state, has a great impact on the mechanical properties, notably Young’s modulus of Cu/W nanomultilayers.

Arc erosion behaviour of Cu–diamond composites at different load voltages in air atmosphere

ABSTRACT To investigate the arc erosion performance of Cu–diamond composites, Cu–5vol.-% diamond composites were fabricated using the hot-pressing sintering method. Compared to pure copper, Cu–5vol.-% diamond composites exhibited improvements in Brinell hardness of 60.1 HB. The relative density and electrical conductivity of Cu–5vol.-% diamond composites were 97.54% and 83.29% IACS (International Annealing Copper Standard), respectively, with no significant decrease compared to pure copper. The thermal conductivity was 423.48 W·(m·K)−1, showing a slight enhancement. The effect of different load voltages on the arc erosion behaviour of Cu–5vol.-% diamond composites was investigated. Experimental results indicated that as the voltage rose from 3 to 7 kV, the breakdown strength decreased from 7.164 × 106 V m–1 to 2.535 × 106 V m–1, while the arc duration increased from 21.752 × 10−3 s to 28.864 × 10−3 s, and the breakdown current rose from 10.8 to 27.2 A. Additionally, the presence of diamond particles enhanced the viscosity of the molten pool, thus the splashing phenomenon of copper liquid during arc discharge was not obvious, indicating that the material loss was small. Few cracks and holes were detected. The Cu–5 vol.-% diamond composites possess good resistance to arc erosion.

Effect of Cu–Al Ratio on Microstructure and Mechanical Properties of Cu–Al Alloys Prepared by Powder Metallurgy

Cu–Al alloys are widely used in electronics, new energy, and other fields due to the combination of th excellent corrosion resistance and electrical conductivity of Cu and the light weight of Al. In this paper, the powder metallurgy and equal-channel angular pressing compound technology was used to fabricate a Cu–Al alloy joint, which can be used to replace armor. Devices such as an optical microscope, electron scanning microscope, and microhardness scale were used to characterize the microstructure and mechanical properties of the Cu–Al alloys. The finite element analysis software Abaqus was used to analyze stress distribution during equal-channel angular pressing. The results indicated that the microstructure and properties of Cu–Al alloys were closely related to the volume ratio of Cu–Al. The microhardness and tensile strength were significantly increased by increasing the volume ratio of Cu–Al. As the volume ratio of Cu–Al varied from 1:2 to 2:1, the ultimate tensile strength of the Cu–Al alloys increased from 79.9 MPa to 164.9 MPa at room temperature and the microhardness increased from 60 HV to 101 HV. However, the elongation of the Cu–Al alloys hardly changed; this was about 4.4%. Crack initiation occurred at the Cu–Al interface and spread along the bonding surface of the Cu–Al alloys during the tensile process.

Atmospheric plasma sprayed Cu coating on Cu–B/diamond composite for electronic packaging application

Although Cu/diamond composites have high thermal conductivity, the limited processibility and weldability of the hard and inert diamond reinforcement limit their applications for electronic packaging. Therefore, there is a necessity for surface metallization of the Cu/diamond composites. Here, a Cu coating with a thickness of 170 μm is sprayed onto a Cu–B/diamond composite using a rapid deposition technique of atmospheric plasma spraying. The adhesion strength between the Cu coating and the composite is measured to be 13.1 MPa. The Cu-coated composite demonstrated a significantly enhanced wettability, as evidenced by the reduction of the contact angle between the solder and the Cu–B/diamond composite from 96° to 10°. Surface roughness and composition determine the wettability between the solder and the substrate. However, the thermal conductivity of the Cu–B/diamond composite is somewhat decreased from 839 to 738 W/mK after depositing the Cu coating, which is ascribed to the low thermal conductivity of Cu coating. The findings provide an effective way for metalizing Cu/diamond composites for the integration of electronic devices in thermal management.

Effects of multistage thermomechanical treatment on the microstructure and properties of Cu–Ni–Co–Si–Mg alloy strip by HCCM horizontal continuous casting

Multistage thermomechanical treatment experiments were conducted on Cu–Ni–Co–Si–Mg alloy strip prepared by the Heating Cooling Combined Mold (HCCM) horizontal continuous casting-cold rolling process. Effects of various heat treatments on the microstructure, mechanical properties, and electrical conductivity of the alloy were studied. The strengthening mechanisms and factors influencing the performance of each process has been analyzed. The tensile strength, yield strength, and electrical conductivity of Cu–Ni–Co–Si–Mg alloy can reach 894 MPa, 855 MPa, and 47.1 %IACS after a third-stage of thermomechanical treatment (TTMT). The cold rolling in first-stage of thermomechanical treatment (FTMT) not only caused work hardening of the alloy but also promoted the precipitation of solute atoms and the growth of second phase particles, limiting the increase in strength. Second-stage of thermomechanical treatment (STMT) effectively hindered the excessive growth of second phase particles in FTMT but shortened recrystallization process. The superior performance of Cu–Ni–Co–Si–Mg alloy after TTMT was attributed to dispersive precipitation of Ni, Co, and Si elements as (Ni, Co) 2Si phases in the copper matrix, strengthening the interaction between the precipitates and dislocations. A short process of HCCM horizontal continuous casting-cold rolling-thermomechanical treatment was developed to produce a high strength and highly electrically conductive Cu–Ni–Co–Si alloy strip used in lead frames.

Insights into the Tribological Properties and Electrical Conductivity of Cu–C Coating Under Grease Lubrication

Insights into the Tribological Properties and Electrical Conductivity of Cu–C Coating Under Grease Lubrication

Characterization of CuAg Alloys with Low Ag Concentrations.

Copper-based alloys designed to combine high electronic and thermal conductivities with high mechanical strength find a wide range of applications in different fields. Among the principal representatives, strongly diluted CuAg alloys are of particular interest as innovative materials for the realization of accelerating structures when the use of high-gradient fields requires increasingly high mechanical and thermal performances to overcome the limitations induced by breakdown phenomena. This work reports the production and optical characterization of CuAg crystals at low Ag concentrations, from 0.028% wt to 0.1% wt, which guarantee solid solution hardening while preserving the exceptional conductivity of Cu. By means of Fourier Transform Infrared (FTIR) micro-spectroscopy experiments, the low-energy electrodynamics of the alloys are compared with that of pure Cu, highlighting the complete indistinguishability in terms of electronic transport for such low concentrations. The optical data are further supported by Raman micro-spectroscopy and SEM microscopy analyses, allowing the demonstration of the full homogeneity and complete solubility of solid Ag in copper at those concentrations. Together with the solid solution hardening deriving from the alloying process, these results support the advantage of strongly diluted CuAg alloys over conventional materials for their application in particle accelerators.

Tailoring the microstructure, mechanical properties, and electrical conductivity of Cu–0.7Mg alloy via Ca addition, heat treatment, and severe plastic deformation

Tailoring the microstructure, mechanical properties, and electrical conductivity of Cu–0.7Mg alloy via Ca addition, heat treatment, and severe plastic deformation

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

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

High strength and electrical conductivity of nanostructured Cu–1Cr–0.1Zr alloy processed by multi–stage deformation and aging

The effects of equal channel angular pressing (ECAP), multiple cryogenic rolling and aging treatment on the microstructure, mechanical properties, and electrical conductivity of Cu–1Cr–0.1Zr alloy were investigated. The results showed that multi-stage deformation and aging (ECAP at ambient temperature + primary cryogenic rolling 50 % + 450 °C aging for 1h + secondary cryogenic rolling 80 % + 150 °C aging for 1h) can lead to the rational comprehensive performance of Cu–1Cr–0.1Zr alloy with tensile strength of 730 MPa and electrical conductivity of 75.5 % IACS. The microstructure characterization revealed that in the Cu–1Cr–0.1Zr alloy a subject to the multistage deformation and aging, there ultrafine grains, nanotwins, nanoprecipitates and micrometer precipitates constituted the nanostructured state. The increase in tensile strength was mainly attributed to fine grain strengthening and precipitation strengthening, followed by dislocation strengthening due to low temperature deformation. The ECAP resulted in the refinement of grain, and the increased dislocation density. The following primary cryogenic rolling refined the grains up to ultrafine-grained (UFG) size and created nanotwins. The introduction of nano-precipitated phases by intermediate aging pinned dislocations and impeded the motion of dislocation entanglements, allowing the alloy to achieve higher strength. Multi-stage deformation and aging resulted in a higher density of twin boundaries in the nanostructure and dilute solid solution in comparison with one stage treatment. These microstructural features were responsible for the excellent electrical conductivity.

Improved mechanical strength, ductility, and electrical conductivity of Cu–Ni–Si alloys after multi-pass continuous extrusion and aging processes

The manufacture of high strength, high electrical conductivity, and high ductility of Cu–Ni–Si strips in the industry is a challenging problem due to the mutually exclusive relationships among the three properties. However, the results obtained in the present study demonstrated that the trade-offs can be improved by employing a multi-pass continuous extrusion and aging process. The mechanical strength and electrical conductivity increase with the increase of extrusion number before three passes with the help of dynamically occurred recrystallization and precipitation. The yield strength, however, drops after four-pass extrusion, suggesting that a too-high strain deformation during continuous extrusion is not favorable. After aging, alloys that suffer fewer extrusion passes exhibit higher yield strengths, indicating that it is the precipitates rather than the microstructure that dominates the mechanical properties of Cu–Ni–Si alloys. Interestingly, the fracture elongation after aging for alloys experienced more pass number increases, which can be attributed to the refined grain size and reduced dislocation densities. After a two-pass continuous extrusion and aging process, the tensile strength and fracture elongation can reach 629 MPa and 16.5%, respectively, increasing approximately by 28.8% and 13.4% compared with those before aging. It is therefore significant to design an appropriate deformation process (strain) for continuous extrusion to obtain high strength, high conductivity, and high ductility Cu–Ni–Si strips.

Time-domain thermoreflectance measurement of the thermal diffusivity of Nb thin films

Nb-coated Cu superconducting radiofrequency (SRF) cavities are of interest as a possible alternative to bulk Nb cavities for particle accelerators due to the high thermal conductivity of Cu and its lower cost than Nb. Studying the thermal diffusion properties in Nb thin films on Cu is important for developing Nb-coated Cu SRF cavities. In the present study, the thermal diffusivity of 100‒800 nm Nb films on Cu is measured by time-domain thermoreflectance (TDTR). The thermal diffusivity is obtained from a curve fit of the TDTR signal to a one-dimensional Fourier heat diffusion model over a time extending from 25 to 985 ps after laser-surface interaction. The film was examined by atomic force microscopy and scanning electron microscopy. The grain size and thermal diffusivity increase with film thickness. The thermal diffusivity reaches a value similar to that reported for bulk Nb for the 400 and 800 nm films, for which the average grain size is 47 ± 13 nm and 68 ± 18 nm, respectively. TDTR measurement for the 400-nm film taken over the temperature range of 293 to 40 K showed that the thermal diffusivity increases as the temperature is reduced. The results indicate that grain boundaries reduce the thermal diffusivity of the Nb film and, therefore, must be considered in Nb-coated Cu SRF cavities.

Anharmonic rattling leading to ultra-low lattice thermal conductivity in Cu12Sb4S13 tetrahedrites

Phonon propagations driven by disorder and anharmonicity associated with Cu(12e) atoms particularly govern the lattice dynamics in Cu12Sb4S13, resulting in an ultra-low lattice thermal conductivity for thermoelectric applications.

Ni,S co-doped Cu dendrites decorated with core-shell architecture assisted by MOF and Fe0.92Co0.08S nanoflakes on nanocellulose/graphene fibers for fabrication of flexible wire-type micro-supercapacitor.

One-dimensional micro-supercapacitors (1D micro-SCs) have been regarded as an efficient energy storage system to fulfill the ever-growing need for miniaturized electronics. Designing multi-dimensional nanoarchitectures on fibrous microelectrodes is an effective strategy to build a high-performance 1D micro-SC. In this work, Ni,S-doped Cu was firstly prepared on Cu wire as a micro-sized 1D current collector through Cu electrodeposition using a H2 bubble template and then co-doped with nickel and sulfur. Benefiting from the high electrical/thermal conductivity of Cu, and the highly electroactive sites of Ni and S as well as the 3D porous architecture, the deposited Ni,S-doped Cu provided a platform for growing active substances. Thereafter, cobalt carbonate hydroxide (CoCH) pine-like nanoneedle integrated ZIF-67 polyhedrons were synthesized on a foam-like skeleton and converted into NiMoCo-layered triple hydroxide (LTH)/Ni,S-doped Cu shish-kebab type nanoarrays by applying a hydrothermal method. Finally, Ni2Mo3N-CoN/Ni,S-doped Cu was prepared via nitridation. The potent interactions and synergy between components realized a well-organized hybrid nanoarchitecture consisting of dodecahedrons decorated on needle-like arrays within a 3D framework with rich redox properties, rapid ion/electron transfer dynamics and high electroactivity. In comparison to the LTH obtained from the electrodeposition method (without the ZIF-67 precursor) and that derived from leaf-like ZIF-Co, this modified microfiber exhibited a high charge storage capacity of 1.5 mA h cm-2 (149.9 mA h cm-3 and 0.187 mA h cm-1) at 4 mA cm-2 and possesses an excellent durability of 98.4% after 5000 cycles. Additionally, FeCoS nanoflakes were electrodeposited using carbon fiber coated with an rGO-nanocellulose hydrogel (GNCH) and employed as a negative 1D microelectrode, which delivered a high specific capacitance of 1223 mF cm-2 (83 F cm-3, 232.4 mF cm-1) at 4 mA cm-2 with a superior cyclic lifespan. Ultimately, the assembled 1D flexible micro-device (Ni2Mo3N-CoN/Ni,S-doped Cu@CW//FeCoS/GNCH@CF) yielded an energy density of 7.2 mW h cm-3 at a power density of 294 mW cm-3 and outstanding cycling stability in PVA/KOH electrolyte and preserved the capacitive performance under various bending states. This research highlights that assembled 1D micro-SCs have a high potency for next-generation portable/wearable energy-supply microelectronics.

Highly durable and flexible transparent electrode on PET based on copper and cupronickel multilayer

Multilayer grid electrodes consisting of Cu0.7Ni0.3/Cu/Cu0.7Ni0.3 utilize the high conductivity of Cu to realize low electrical resistance and the high corrosion resistance of CuNi to improve reliability. The effect of thickness of outer CuNi layer on corrosion resistance and visibility was investigated. Samples prepared with 2 μm line width on PET having grid mesh side length of 300 μm, and 60° internal angle with 280 nm thickness showed a transmittance of 90.1% at 550 nm and sheet resistance of 2.4 Ω/□ after grid pattern formation. The low process temperature enabled electrode formation on thin substrate, 23 μm-thick PET and accomplish highly durable and flexible electrode on PET. The superior bending properties showed no change in sheet resistance after 200 000 cycles of outer/inner fatigue bending tests at 3 mm radius of curvature. Additionally, the potential for foldable usage was further supported by demonstrating the ability to form electrodes on both sides of the film.

First-Principles Study of the Effect of Sn Content on the Structural, Elastic, and Electronic Properties of Cu–Sn Alloys

In order to explore the mechanism of the influence of Sn contents on the relevant properties of Cu–Sn alloys, the structure, elasticity, electronic, and thermal properties of Cu–Sn alloys doped with different proportions of Sn (3.125 at%, 6.25 at%, and 9.375 at%) were established using the first-principles calculation based on density functional theory. Firstly, their lattice constants and Sn concentration comply with Vegard’s Law. From the mixing enthalpy, it can be seen that Sn atoms can be firmly dissolved in the Cu matrix, and the structure is most stable when the Sn content is 3.125 at%. In addition, the introduction of mismatch strain characterized their solid solution strengthening effect. The elastic and electronic properties showed that when the Sn content is 6.25 at%, the Cu–Sn alloy has the best plasticity and the highest elastic anisotropy; when the Sn content is 3.125 at%, the Cu–Sn alloy is the most stable and has stronger bulk and shear modulus, which was mainly due to a stronger Cu-Cu covalent bond. Finally, the Debye temperature, thermal conductivity, and melting point were calculated. It is estimated that the thermal conductivity of Cu–Sn alloy is relatively good when the Sn content is low.

Properties and mechanism of Cu(OH)2 nanoarray reinforced cement composites

This experiment investigates the effect of Cu(OH)2 nanoarray on the properties of cementitious materials. Cu(OH)2 nanoarray is a novel nanomaterial with excellent electrical conductivity and chemical stability. At present, the interaction mechanism between Cu(OH)2 nanoarray and cementitious materials has not been explored. In this paper, the effect of Cu(OH)2 nanoarray on the properties of cement mortar was investigated by testing the mechanical strength and electrical conductivity of Cu(OH)2 nanoarray. The microstructure of Cu(OH)2 nanoarray cement mortar and the development of hydration products were analyzed using XRD, SEM, EDS and MIP tests. The results showed that when 0.5% Cu(OH)2 nanoarray was added, the 28d compressive strength and flexural strength of the cement mortar increased by 50.29% and 41.28%, respectively, and its electrical resistivity decreased by 50%. The Cu(OH)2 nanoarray optimized the mechanical strength and workability of the cement mortar by modulating the hydration products and improving the microstructure.

Synergistic improvement of strength and electrical conductivity in Cu–Cr–Zr alloys through prestrain-assisted friction stir processing

The objective of this study is to investigate the effects of prestrain-assisted friction stir processing and subsequent aging heat treatment on the microstructural evolution and performance of copper-chromium-zirconium alloys. The findings indicated that prestrain, generated through cold rolling before friction stir processing, considerably affected grain refinement and enhanced the mechanical properties and electrical conductivity in the processing zone. The prestrain not only decreased the activation energy of dynamic restoration and precipitation in the processing zone, but also strengthened the “constraint effect” of the base metals to the processing zone. This effectively reduced the width of micro-bands and promoted nanocrystalline formation in the processing zone. Furthermore, dynamic precipitation resulted in higher thermal stability of the microstructure in the processing zone during subsequent aging heat treatment. Thus, the synergistic improvement of the mechanical properties and electrical conductivity of copper-chromium-zirconium alloys was successfully achieved.