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The May 2024 issue of the Journal of Materials Science features a cover paper titled "Role of stacking fault energy in confined layer slip in nanolaminated Cu" by Ji et al. The paper explores the deformation of metallic nanolaminates and acknowledges the contribution of Professor Hussein Zbib. The issue is dedicated to honoring Professor Zbib's memory and was conceived by Guest Editors Tariq Khraishi, Georges Ayoub, Sinisa Mesarovic, and Mutasem Shehadeh. The paper includes references to previous work but does not mention any measurements of the intrinsic stacking fault energy. The corresponding author is Professor Shuozhi Xu from the University of Oklahoma, and the last author is Professor I.J. Beyerlein, who has a background in research and was born in Los Alamos. The paper is freely accessible through the SharedIt link provided. [Extracted from the article]

The dielectric loss of Cu with high thermal conductivity is large at high frequency, which cannot meet the performance requirements in high-integrated circuits. There is an urgent need for materials to reduce its dielectric loss. In this paper, the thermal conductivity and dielectric properties of the AlN coating-Cu substrate system were controlled by changing the N2 pressure. The results showed that the crystallinity of hcp-AlN in AlN coating increased significantly when the proportion of N2 pressure was increased. With the increase of the N2 pressure, the particle size on the surface and the roughness of the coating improved. The AlN coating prepared at high N2 pressure had high dielectric constant and low dielectric loss at high frequency compared to those of the coatings prepared at low N2 pressure. At the same time, the AlN coating prepared under high N2 pressure on the Cu substrate did not decrease the thermal conductivity of Cu substrate. The AlN-Cu system prepared in this paper had high thermal conductivity and good dielectric properties, providing theoretical guidance for integrated circuit packaging and capacitor applications. [ABSTRACT FROM AUTHOR]

In the paper, near-net shape fabrication (ball milling, cold pressing, and microwave sintering) of Fe-6.5 wt%Si steel strip was carried out on the basis of the rapid solidification single-roll spinning, and the micromorphology transformation, texture evolution, mechanical and magnetic properties of the obtained samples were studied. This process could not only prepare samples with good mechanical and magnetic properties, but also achieve near-clean shape treatment. The results show that the refinement and homogenization of grain and the evolution of texture (the disappearance of γ-texture and the formation of Goss texture) play a good role in improving the mechanical and magnetic properties. The sample prepared by 1200 °C microwave sintering has excellent magnetic properties of Ms = 232.54 emu/g, Hc = 32.27 Oe, and Mr = 3.13 emu/g, and it also has the highest Vickers hardness of 212.32HV. [ABSTRACT FROM AUTHOR]

Through Silicon Via (TSV), a kind of 3D packaging technique, can improve chip integration based on "More than Moore" scheme. The larger copper area ratio at the TSV barrier layer interface requires strong adjustability of the removal rate selection ratio of copper, tantalum and TEOS–SiO2, and stronger surface defect control and surface profile correction capabilities. In this paper, the effects of guanidine hydrochloride (GH) and 2,2′-[[(Methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol (TT-LYK) system on the tunability of Ta and Cu removal rate in chemical mechanical polishing (CMP) of TSV wafer barrier material were studied. GH can complex TaO 4 3 - , while TT-LYK can form a protective film on the surface of Cu, thereby achieving rate regulation. The results showed that when the concentration of GH increased from 0 to 2 wt%, the removal rate selectivity ratio of Ta and Cu raised from 1.02:1 to 1.26:1. When the concentration of TT-LYK increased from 2.5 to 10 mmol/L, the removal rate selectivity ratio of Ta and Cu increased from 1.33:1 to 1.79:1, which verified that the GH and TT-LYK systems can efficiently regulate the rate and rate selection ratio of Ta and Cu. Surface roughness for both metals decreased from pre-polishing values of 5.03 nm to post-polishing values of 0.37 nm for Ta, from pre-polishing values of 5.33 nm to post-polishing values of 1.26 nm for Cu indicating that GH and TT-LYK systems significantly improved the surface quality. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical damage behavior is investigated based on the characteristic roughness on the surface and the orientation of superficial structures. The main goal is to explore the surface roughness on mechanically loaded copper conductors as a lifetime indicator. For this purpose, copper conductors are mechanically stressed in accordance with EN 50,396 and then examined metallographically and microscopically. The microstructure examination shows that the roughness is caused by material extrusion and cracks due to work hardening in the surface area. Using confocal microscopy, it is shown for the first time that significant formation of surface roughness takes place over the service life of copper conductors. The roughness increases monotonically, but not linearly with number of cycles, due to internal microstructural processes and can be divided into three sections. First inspections of the conductor surface over lifetime show a correlation between the intensity of structures orientated 45° to the loading direction and the roughness. This phenomenon, already known from microscopic slip lines, is thus also evident in macroscopic roughness formation and is well founded by the research theory on material extrusion along dislocation lines. In summary, a lifetime determination is possible based on its developing roughness which enables the utilization as a sensor element. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms behind sintering Cu-Ag core–shell nanoparticles can help us optimize the sintering process parameters and design the core–shell structure to achieve the desired sintering structure. In this paper, we employed molecular dynamics simulations to investigate the sintering behaviors and mechanisms of CS NPs, taking into account the effects of shell thickness, particle size, and temperature. Our results revealed that dislocation loops in Cu-Ag CS NPs played a crucial role in sintering by emitting dislocations that facilitated crystal evolution, thereby reducing the number of amorphous structures. The state of dislocation loops could be controlled by shell thickness and NP size. As the shell thickness decreased to 0.5 nm, the structure of the dislocation loops could not be generated due to the extremely chaotic and thin Ag atoms. Furthermore, for NPs of the same size, the CS NP with a 0.5-nm shell thickness was the most active. Despite the neck not consisting of a Cu core, the Cu core, particularly its interface, could still participate in the sintering process. At 900 K, limited interface diffusion could be activated. [ABSTRACT FROM AUTHOR]

The impact of solute Al on the penetration of Cu atoms into the Fe grain boundary (GB) in the Fe–Cu embrittlement system was investigated by performing molecular dynamics simulations. Furthermore, the first principle density functional theory calculation was also employed to determine the binding properties and the electronic structure of GBs doped with solute atoms. The inhibition mechanism of liquid metal embrittlement (LME) cracks in the Fe–Cu system by Al was analyzed at the atomic scale by conducting simulations and calculations. The results show that the diffusion rate of Al along with the GB direction was much higher than that of Cu, and the preferential penetration and segregation of Al atoms acted as a barrier layer. Moreover, the addition of Al reduced the potential energy of Cu atoms, thus stabilizing their motion. These factors significantly inhibited the diffusion of Cu atoms along with the GB direction. The binding property of Fe GB doped with a high concentration of Cu was severely deteriorated, while the Al doping improved the atomic bonding. GBs with higher binding properties are less susceptible to fracture and groove under the application of tensile stress. This paper presents a novel perspective on the inhibition mechanism of LME cracks by doping a third component to inhibit the penetration of embrittlement atoms. [ABSTRACT FROM AUTHOR]

Copper/steel composite is a kind of composite with excellent performance and broad application prospects. In this paper, the micro-morphology and structure of the interface of copper/steel composite prepared by the hot-dip casting were observed by scanning electron microscope and transmission electron microscope, and the formation mechanism of the interface area was explored. The results show that the hot-dip casting temperature has a great influence on the micro-structure and morphology of the copper/steel interface area. When the hot-dip casting temperature is lower than 1125 °C, the copper/steel interface area is basically in a straight line. Even if the hot-dip casting time is extended, the interface characteristics change little. At 1100 °C, the copper-rich phase precipitated at the interface area is the coherent precipitates of Cu and BCC-Fe, with the crystal orientation <110> and the diameter about 10 nm ~ 30 nm. When the hot-dip casting temperature reaches 1150 °C, the copper/steel interface area begins to appear new micro-morphology, and the range of new micro-morphology becomes larger and larger with the increase in the hot-dip casting temperature and the extension of the hot-dip casting time. At 1200 °C, the copper-rich phase precipitated at the interface is the coherent precipitates of FCC-Cu and FCC-Fe, with the crystal orientation <100> and the size similar to that at 1100 °C. In the process of the hot-dip casting, the formation of the copper/steel interface area experienced three stages: the co-temperature of copper/steel and the wetting of copper liquid on solid steel, the formation and transformation of the solid–liquid mixed layer between steel and copper liquid and the evolution stage of the liquid–solid mixed layer during cooling and solidification. This kind of interface zone with gradual structure tightly connects the steel matrix and solidified copper together, to form a copper/steel composite with strong bonding. [ABSTRACT FROM AUTHOR]

The regulation of hydrogen content in the continuous casting process is conducive to the reduction of pore defects in the casting billet. In this paper, the influence of negative pressure (NP) and continuous casting speed (CCS) on hydrogen content in copper rod billet prepared by negative pressure continuous casting (NPCC) technique was analyzed, and the mechanism of the coordinated coupling of NP and melt flow on hydrogen removal was revealed. It is clarified that with the CCS of 20 mm min−1 and an increase in the NP value from − 20 to − 80 kPa, the hydrogen content is reduced from 1.0 to 0.3 ppm. The coordinated action of NP and melt flow induced by CCS can minimize the hydrogen content. When the NP value is − 80 kPa and the CCS is 10 mm min−1, the hydrogen content is as low as 0.2 ppm, and the hydrogen removal rate is 85.7%. The larger the NP, the smaller the critical nucleation radius of the hydrogen bubble, and the larger the growth rate of the hydrogen bubble. The coupling of the NP field and flow field can make the melt which is difficult to nucleate and grow of the hydrogen bubble flow to the position which is easy to nucleate and grow. The effect of the vortex fields in the purification chamber on the removal of hydrogen is not affected by the CCS, but the CCS affects the floating of hydrogen at the solidification front, which leads to a small increase in the hydrogen content with the increase of the CCS. Our study provides a theoretical basis for the preparation of high-quality metal billets. [ABSTRACT FROM AUTHOR]

In this paper, high-density (60−x)Fe−Cr−Co−xCu (x: 0–6 wt.%) permanent magnet alloys were fabricated by laser powder bed fusion (LPBF) in-situ alloying technique, and the effects of Cu content on the microstructure, magnetic, and mechanical properties of the alloy were systematically investigated. The addition of 2 wt.% Cu enhanced the coercivity H c and the energy product (B H) max of the alloy in the isotropic state by 19.4 and 27.9%, respectively, compared to the alloy without Cu. The impacts of Cu content on the magnetic properties were investigated by combining experimental results and first-principles calculations. Furthermore, the addition of Cu improved the yield strength of the alloy, and the strengthening mechanism was analyzed in detail. The yield strength of the alloy with 2 wt.% Cu reached 908 MPa, representing a notable 7% increase relative to the Cu-free alloy. [ABSTRACT FROM AUTHOR]

With the continuous downsizing of solder joints, the influence of the grain characteristics of the under bump metallization (UBMs) on the interfacial reaction is exposed. In this paper, the effect of grain characteristics of Cu UBM on the growth of interfacial intermetallic compounds and the formation of Kirkendall voids in Cu/Sn/Cu micro solder joints during isothermal aging at 150 °C was investigated. Electroplated polycrystalline Cu (EP-Cu), (111) single crystal Cu ((111) Cu), and (111) nano-twinned Cu ((111) nt-Cu) were selected as UBMs. After reflow soldering, the Cu6Sn5 grains formed on (111) nt-Cu were near to the orientation (2 1 - 1 - 3) , while those were randomly formed on both EP-Cu and (111) Cu. During isothermal aging, the Cu6Sn5 grains exhibited the highest growth rate on (111) nt-Cu UBM, and the slowest growth rate on (111) Cu UBM, due to the differing number of diffusion routes among the three Cu UBMs with distinct grain characteristics. Furthermore, no Kirkendall voids were detected on the (111) Cu UBM, however, a significant number of Kirkendall voids were identified on the (111) nt-Cu UBM, which can be attributed to the diffusion path and impurities present in the three Cu UBMs. The results will offer theoretical and practical recommendations for the selection of Cu UBMs for micro solder joints in 3D packaging interconnection technology. [ABSTRACT FROM AUTHOR]

Due to the excellent thermoelectric properties and low sintering temperature, nano-Ag paste is a promising die-attach material for high power electronic device. Unfortunately, it is difficult to resolve the critical issues including poor interfacial wettability, high porosity and poor high-temperature reliability of sintered nano-Ag joint. In this study, a novel bonding method was proposed to solve these problems by introducing Sn into the nano-Ag joint through the transient-liquid-phase (TLP) bonding technology. The Ag-Sn joint reported in this paper maintained excellent mechanical properties after high temperature aging and thermal shock test. The addition of Sn reduced the porosity of nano-Ag joint and improved the wettability of bonded interface. After aging at 200 °C for 2000 h, the shear strength still remains higher than 50 MPa. Besides, this bonding approach resolves the oxidization problem of Cu substrate at high temperature. The molecular dynamics (MD) simulation results indicate the addition of Sn could effectively inhibit the permeation of oxygen into the interface. [ABSTRACT FROM AUTHOR]

In this paper, we proposed rapid laser-induced synthesis of copper micropatterns on the surface of oxide glass from deep eutectic solvents (DESs) consisting of choline chloride, citric or tartaric acid, and copper acetate as the copper plating solutions. It was shown that upon the 532-nm continuos wave laser irradiation, it is possible to increase the deposition rate of copper and create micropatterns with a resistance close to the value of pure metal together with high adhesion to the substrate surface. This metallization method is favorable for the practical use of copper patterns, including in the production of new printable microelectronic devices. Thus, we demonstrated the possibility of copper deposition on arbitrary three-dimensional surfaces. Moreover, the resulting copper micropatterns were tested as working electrodes for non-enzymatic glucose. Finally, the proposed technology can be successfully used for the design and development of sensor platforms for the electrochemical analysis and microelectronic devices. [ABSTRACT FROM AUTHOR]

The effect of Ni in Ag–Cu filler on the wetting and brazing characterization of stainless steel was studied by means of wetting test and brazing test under high vacuum condition. The wettability of filler metal and the joint strength were improved after adding Ni in Ag–Cu filler. The filler penetrates into stainless steel and the topmost steel grains separate from the substrate, exposing the metal surface without oxide film after adding Ni, which leads to the reduction in contact angle. The interdiffusion between FM and SS is enhanced after adding Ni, which leads to further reduction in contact angle. At wetting temperature, large amount of Ni in liquid enriched at solid–liquid interface, increasing the Cu content in liquid near the interface to form Cu-rich liquid, which caused the penetration of liquid filler. Cu first penetrates into steel grain boundary, which provides a path for Ni diffusion into stainless steel. After the oxide film was removed, a large number of Ni directly diffused into stainless steel to form (γ-Fe, Ni) layer on stainless steel surface. Cu in liquid can directly diffuse into (γ-Fe, Ni). Stainless steel can dissolve in Cu-rich liquid with high Ni content. In the absence of Ni, FM/SS interface is the weakest location of the joint. After adding Ni in filler, the formation of Cu solid solution at FM/SS interface and the enhancement of interdiffusion between FM and SS strengthen the FM/SS interface, leading to the increase in joint strength. The results in this paper suggest Ni is beneficial for brazing stainless steel by Ag–Cu alloy. [ABSTRACT FROM AUTHOR]

Solar-driven interfacial evaporation is a sustainable and green desalination method with great prospects for development in today's severe water shortage problem. In this paper, a novel composite aerogel was prepared by hydrothermal method with sodium alginate (SA) and Cu2+ in the preparation process using reduced graphene oxide as photothermal material and cellulose nanofibers as substrate. The good hydrophilicity of nanocellulose makes the composite aerogel have strong capillary action and continuous water transport. The gel formed by ion exchange between SA and Cu2+ greatly improves dry and wet mechanical strength of the composite aerogel and ensures the stability of the evaporator for multiple recycling. Copper is doped by reduction of copper ion complexes and reduced graphene oxide have a synergistic effect to increase the photothermal response rate of the composite aerogel of 1.446 kg m−2 h−1 with evaporation efficiency of 84.87% under one standard solar irradiation. In addition, the purification of heavy metal ions, dye wastewater as well as acid and alkali solutions also has excellent results. It is expected that this study will provide some new ideas for the fields of seawater desalination and wastewater treatment. [ABSTRACT FROM AUTHOR]

The demolding process of electroforming technology in fabricating microstructured optical-functional thin films produces the problem of excessive bonding between the metal substrate and the metal replica, which triggers the deformation of the microstructure and the reduction of precision, and the deposition of Cr–O–C discrete nuclei at the interface can play a good role in assisting the demolding effect. In this paper, the tensile deformation of polycrystalline Cu/Ni and Cu/Cr–O–C/Ni composites is investigated using molecular dynamics methods. The results show that the Cu/Ni model produces a large number of HCP structures during stretching, with holes at the interface and a large number of Cu atoms transferring to the Ni layer. The addition of the Cr–O–C layer reduces the yield strength of the Cu/Cr–O–C/Ni model by 26.41%, and at the same time, the dislocation proliferation at the interface is reduced, and the fracture is at the centralized interface, and the fracture time is reduced by 90.8%. The higher number of Cr–O–C atoms at the interface decreases the transfer of Cu atoms to the Ni layer. The results provide a possible explanation for the Cr–O–C layer-assisted precision electrodeposition debonding. [ABSTRACT FROM AUTHOR]

Mo/Cu composites exhibit significant potential for applications in electronic packaging and other domains. However, the diffusion process and mechanism of Mo/Cu composites are difficult to experiment with. Therefore, in this paper, a new potential function is first constructed and verified for the Mo/Cu system. The Mo/Cu diffusion process is studied on the atomic scale by molecular dynamics (MD) simulation. The conditions for rapid diffusion of Mo/Cu are determined at 1000 K and Mo (100) interface orientation. The vacancy diffusion mechanism in the Mo/Cu system is elucidated through the analysis of the diffusion results. Finally, the diffusion under an external electric field is simulated, and the critical condition for diffusion is determined by increasing the vacancy concentration. The diffusion temperature can be reduced by about 100 K at E = 0.002 V/Å. This study can provide theoretical support for the electro-assisted preparation of Mo/Cu composites.Graphical abstract: Mo/Cu composites exhibit significant potential for applications in electronic packaging and other domains. However, the diffusion process and mechanism of Mo/Cu composites are difficult to experiment with. Therefore, in this paper, a new potential function is first constructed and verified for the Mo/Cu system. The Mo/Cu diffusion process is studied on the atomic scale by molecular dynamics (MD) simulation. The conditions for rapid diffusion of Mo/Cu are determined at 1000 K and Mo (100) interface orientation. The vacancy diffusion mechanism in the Mo/Cu system is elucidated through the analysis of the diffusion results. Finally, the diffusion under an external electric field is simulated, and the critical condition for diffusion is determined by increasing the vacancy concentration. The diffusion temperature can be reduced by about 100 K at E = 0.002 V/Å. This study can provide theoretical support for the electro-assisted preparation of Mo/Cu composites. [ABSTRACT FROM AUTHOR]

In this paper, 50 ... 680 nm thick AlN-Al2O3 coatings are deposited by magnetron sputtering on the surface of a steel substrate and a piece of copper is melted on top of the ceramic. Upon heating the ceramic layer is cracked, and the phase inversion of the two top phases from steel/ceramic/copper configuration to the steel/copper/ceramic configuration takes place within 30 s of liquid time of copper. This phase inversion process is accompanied by a Gibbs energy change of about − 1.78 J/m2, due to good wettability of solid deoxidized steel by liquid copper in contrary to poor wettability of the ceramic by the copper. When copper is melted on AlN-Al2O3 coating with its thicknesses smaller than a critical value of about 170 ± 60 nm, liquid copper droplets hanging down into the cracks within the ceramic reach the solid steel surface at the bottom of the cracks, thus the flow of Cu down along the cracks is enabled. However, when copper is melted on AlN-Al2O3 with its thickness larger than the critical value of 170 ± 60 nm, Cu first forms a non-wetting droplet on top of the ceramics, and only after a certain incubation time it starts flowing down the cracks. This incubation time was found to depend linearly on the thickness of the ceramic, as cracks are filled from the bottom upwards by liquid copper via the evaporation–condensation mechanism. By the end of the process, the steel/copper/ceramic configuration is further stabilized by gravity. [ABSTRACT FROM AUTHOR]

Research into the corrosion behavior of a copper substrate with a graphene coating synthesized using the CVD method has been performed. The influence of various copper substrates with varying substrate thickness, time of high-temperature annealing and duration of graphene synthesis was investigated. Different synthesis durations allowed studying the corrosive current on the copper surface: (a) not fully covered with graphene, (b) completely covered with single-layer graphene and (c) when there are areas with several graphene layers on the surface. Electrochemical corrosion in saline solution was realized at high and low potentials of the working electrode, which enabled assessment of the limiting factors of corrosion. At a low potential, the mass of corrosion products decreased by an order of magnitude. A hypothesis explaining the formation of deep corrosion pits of rectangular shape was proposed. The energy-dispersive X-ray analysis (EDAX) demonstrated that with a high potential of the working electrode, an essentially heterogeneous distribution of carbon and copper is realized (compared with a lower potential of the electrode). With the duration of graphene synthesis from 0 to 10 min, the corrosion current decreases almost 10 times. With a further increase in the duration of synthesis, the corrosion current drops slightly. The performed MD simulation on wettability corresponds to the experimental data. The obtained results may be useful for the development of the technology of defect-free graphene-based sensors that are less sensitive to corrosion. [ABSTRACT FROM AUTHOR]

Nanoporous metals can serve in unique functional applications due to their high surface area, and they are often made through dealloying, which removes a sacrificial element through chemical etching and leaves a nanoporous matrix of the remaining element(s). Several variations on this technique allow for a wider variety of metals and alloys to be processed, but simple, scalable, and reliable production of nanoporous devices is still not a reality using the majority of techniques and alloy systems. Oxide reduction may provide a suitable alternative, and in this work, nanoporous Cu was produced via oxide reduction in the Cu–CuO system. This method uses mechanical milling to create a metal matrix composite powder primarily composed of CuO that is reduced under hydrogen to leave pure Cu behind. It requires no harsh chemicals, and it uses modest temperatures and short reaction times. Furthermore, it is fully compatible with traditional powder metallurgy, making it readily scalable. Powder compacts were also processed to track the geometric changes associated with each composition and demonstrate that device creation is feasible, even with the basic process applied here. This work reveals important parameters associated with these materials by incorporating a wide range of milling times and compositions, with shorter milling times and higher oxide concentrations providing the finest pore sizes, the highest porosity, and the greatest simplicity. [ABSTRACT FROM AUTHOR]

A new bifunctional nanomaterial, [SBCu(II)Hyd]-MWCNTs, exhibiting exotic electrical and magnetic properties has been synthesized via chemical modification of MWCNT-COOH. Double probe DC electrical conductivity, CV and EIS studies show better conductivity of the material than that of MWCNT-COOH. With higher saturation and remanent magnetization, as well as coercivity, [SBCu(II)Hyd]-MWCNTs showed better ferromagnetic characteristics. Mott–Schottky electrochemical analysis was carried out to explore capacitive and dielectric properties. The enhancement in electrical conductivity of [SBCu(II)Hyd]-MWCNTs is also confirmed by optical and electrochemical band gaps studies. Subsequently, this material has been utilized to fabricate an electrochemical sensor by coating it over glassy carbon electrode for the determination of glucose. The corresponding sensitivity and limit of detection values are calculated to be 1.1 µA µM−1 cm−2 and 0.09 µM, respectively. [ABSTRACT FROM AUTHOR]

A silver metallic interlayer was inserted into a direct-bonded aluminum–copper (DBAC) substrate to inhibit the formation of aluminum–copper intermetallic compounds (IMCs) in the substrate. The Ag caused the dissolution of small quantities of Al and Cu to form a Ag(Al, Cu) metallic layer, which exhibited lower hardness (1.4 ± 0.2 GPa) and a lower elastic modulus (71.7 ± 12.8 GPa) than did Al–Cu IMCs (hardness/elastic modulus: 10.4 ± 0.9 GPa and 193.9 ± 7.2 GPa for Al4Cu9, 10.6 ± 0.3 GPa and 171.2 ± 10.7 GPa for Al–Cu, and 7.6 ± 1.5 GPa and 121.0 ± 8.4 GPa for Al2Cu, respectively). Moreover, the Ag(Al, Cu layer was able to withstand high stress caused by the coefficient of thermal expansion mismatch between Al, Ag, and Cu; thus, this layer prevented crack formation at the Al–Cu bonding interface. The shear strength of the Al–Cu bonding interface was originally 13.3 ± 3.4 MPa. This value then increased to 26.3 ± 3.6 MPa when a Ag metallic interlayer was inserted, and the shear strength was maintained at 21.9 ± 1.1 MPa during 500 thermal cycles between − 50 and 150 °C. At room temperature, the thermal conductivity of DBAC with a Ag metallic layer (280 W/mK) was higher than that of direct-bonded aluminum (233 W/mK) and DBAC without a Ag metallic layer (276 W/mK) because of the high thermal conductivity of Ag and the absence of Al–Cu IMCs in the DBAC with a Ag metallic layer. [ABSTRACT FROM AUTHOR]

Environmentally benign sustainable development can be realized only by meeting our energy demands through devices that can operate by taking energy from their surrounding environment. Self-assembled nanostructured CuO on copper ribbon and spin-coated ZnO thin films were optimized for engineering a self-powered UV photodetector in this work. We optimize the thickness of the ZnO and CuO thin films and subsequently the concentration of the alkaline electrolyte KOH to deliver a self-powered UV photodetector which exhibits an ON/OFF ratio of 505, photosensitivity of ~ 3433%, responsivity of ~ 84 mAW−1 and an excellent incident photon to current conversion efficiency of ~ 30% at 360 nm. We demonstrate the actuation of the UV photodetector by integrating the cells and switching on red and green LEDs. [ABSTRACT FROM AUTHOR]

With the fast growing of oily contaminants, continuous oil/water separation with high flux is in demand. Superhydrophilic/superoleophobic composites are considered as ideal candidates. In this work, the oil–water separation composite is from superhydrophilic copper mesh coated by robust superhydrophilic/superoleophobic paint based on fluorine-containing epoxy resin. Firstly, a superhydrophilic/superoleophobic coating with excellent comprehensive properties was prepared through hydrophilic epoxy and superhydrophilic/superoleophobic TiO2. Then copper mesh was treated into being superhydrophilic, and the superhydrophilic/superoleophobic coating was sprayed on the superhydrophilic copper mesh to obtain oil–water separation material. As a result, the oil–water separation efficiency of the separation material is higher than 99.7%, the water flux is higher than 80,000 L m−2 h−1, and it has excellent mechanical properties. The oil–water separation material is promising for the applications. [ABSTRACT FROM AUTHOR]

In this work, rapid failure of a few minutes was observed in real ball grid array solder joints under high current density (8 × 103 and 1 × 104 A cm−2) at room temperature. For each test condition, the failure solder joint was detected at the same position of the daisy chain by computed tomography technology. Furthermore, the open failure for all solder joints was caused by the chip side (anode side) Cu dissolution. Microstructure evolution for a pair of electrically connected solder joints was investigated. In both solder joints, Cu atoms on the chip side were dissolved to the board side with the formation of intermetallic compound particles in solder matrix. Finite element simulation was introduced to calculate the current density, temperature, and heat flux distribution. The temperature gradient along the direction of Cu migration in solder joint was developed due to the accumulation of Joule heating. Thermomigration was confirmed as the dominant mechanism of chip side Cu dissolution. [ABSTRACT FROM AUTHOR]

Printed circuit boards (PCB) are easily corroded under moist environment due to formation of dendrites and short circuit. It would be a promising approach to exploit intentionally formed dendrite covered by functional coating for corrosion inhibition to elongate the lifespan of PCB. In this work, a facile electrodeposition method has been applied to grow dendritic tin onto Cu as a substrate for PCB. Bioinspired formation of superhydrophobic surface (SHS) and liquid-infused surface (LIS) are adopted to minimize access of moisture to underneath Cu metal. In this regard, dimethylsilicone oil and zeolitic imidazolate framework (ZIF) nanoparticles are infused into dendritic matrix to form a solid–liquid ZIF-LIS coating. Morphology, composition and wettability are characterized by different sophisticated techniques. Beyond significant improvement in corrosion resistance, ZIF-LIS has demonstrated self-healing properties, improved mechanical stability and anti-icing behavior. Current finding provides a new approach to fabricate coating for PCB having extended stability against corrosive degradation. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) has great potential to produce graphene films at large-scale. However, CVD production of graphene films usually requires a catalytic metal substrate, such as copper. Recently we have developed a new method to grow graphene films directly on crystalline silicon wafers with a thermally grown 300 nm oxide layer, using a seeded-CVD growth approach. The use of methane as the feedstock and optimized graphene seeds has led to enhanced film formation, which SEM, X-ray photo-electron and Raman spectroscopies indicate consist of graphene layers formed by the coalescence of expanding "graphene seeds". The resultant films have regions of single graphene crystallites within them as a result of lateral growth of the seeds. In addition, we have observed that the unilateral conductivity of the graphene films is consistent with the presence of graphene nanoribbons and as such has potential application in device fabrication. [ABSTRACT FROM AUTHOR]

To study plastic deformation behavior in high-strength Cu–Ag nanostructured composites, we compared (1) overall stress–strain curves with local stress–strain curves and (2) engineering stress–strain curves with true stress–strain curves. We then related the differences between these curves to the internal structure of the composites from microscale to atomic scale. Strain-softening appeared both locally and overall in longitudinal samples. Pronounced strain-hardening occurred only locally in transversal samples. In longitudinal cross-section, but not in transversal cross-section, we observed many shear bands in which the lamellar thickness values of Cu and Ag were below 6 nm and 2 nm, respectively. Within these bands, the boundaries between Cu and Ag were composed of semi-coherent {111} interfaces in a zigzag pattern, with twins and stacking faults concentrated in Ag lamellae. We demonstrated that strain-softening in longitudinal tensile samples resulted from a favorable angle within shear bands between the existing {111} slip system and the maximum shear stress direction. Strength in the transverse direction was about 10% stronger than in the longitudinal direction, an anisotropy in strength values that we attributed to the underlying anisotropy in local true strain-hardening. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces have attracted extensive attentions due to their promising potential for broad applications. However, the complex preparation process and expensive low-surface-energy modifier significantly constrain its large-scale practical applications. Thus, construction of robust liquid-repellent surfaces via a facile and versatile approach without assistance of binder or post-modification is still highly desired and challenging. In this work, we synthesized superhydrophobic organic–inorganic coupling PVDF@SiO2 hybrid particles by thiol-ene click reaction using the branched thiol-terminated pentaerythritol tetra(3-mercaptopropionate) (PETMP) as cross-linking agent. The prepared PVDF@SiO2 hybrid particles could be used as building units to construct robust inorganic–organic composite superhydrophobic coating on various substrates through a simple spraying-curing process without any post-modification treatments. Owing to its high intermolecular cohesive force and self-film formation property of PVDF matrix, the fabricated coating possesses stable superhydrophobicity even after withstanding mechanical destruction or chemical harsh conditions. More importantly, the PVDF@SiO2 coating tremendously enhanced anti-corrosion property of Cu plate by orders of magnitude, with the corrosion current decreasing from 6.15 × 10–3 to 3.92 × 10–6 mA cm−2. Therefore, this strategy for constructing superhydrophobic composite coatings on various substrates could promote the advancement of interfacial superwetting technology and provide promising potentials for large-scale practical applications. [ABSTRACT FROM AUTHOR]

The enhancing effect of low melting trace additions (Sn, Cd, In) on the precipitation hardening in the Al–Cu based alloys accounts for the great practical importance of this phenomenon. However, to date, the influence of Sn micro-addition, either separately or jointly with other ones, on the precipitation structure and hardening of the wrought 2219-type alloys based on the Al–Cu–Mn system remains unexplored. In this study, the effect of 0.1 wt% (0.02 at.%) Sn trace addition on the structure and mechanical properties of the new Al–4Cu–1.5Mn (wt%) alloy has been studied using computational (thermodynamic calculations) and experimental techniques. Analysis of microhardness has revealed that the peak hardness at aging of the wrought model Sn-containing alloy reaches ~ 120 HV which is about 43% higher than for the Sn-free alloy. Transmission electron microscopy analysis of the peak-aged hot-rolled sheet alloys has revealed that trace addition dramatically changes the precipitation structure leading to the formation of much finer precipitates (with an average length of 55–60 nm) with a higher number density. Uniaxial tensile tests of the wrought and peak-aged samples have revealed that the mechanical properties of the model Al4Cu1.5Mn0.1Sn alloy (UTS ~ 402 MPa, YS ~ 323 MPa and elongation ~ 9.7%) are very close to those of the industrial 2219-type alloy. However, the new alloy contains a much lower concentration of copper and a superior fraction of Al20Cu2Mn3 phase dispersoids the influence of which on the mechanical properties should be further studied in detail. [ABSTRACT FROM AUTHOR]

The environmentally friendly luminescent sensing materials are desired for detection of heavy metal ions. Herein, two kinds of fluorescent nanomaterials, carbon dots (CDs-1) and N-doped carbon dots (CDs-2) were designed and synthesized as effectively sensors for simultaneous detection of Fe3+ and Cu2+ ions. A simple one-step hydrothermal synthesis was adopted by using cost-effective precursor humic acid (HA) as a carbon source and ammonium hydroxide as a nitrogen source. Photoluminescence (PL) spectra and TEM images reveal the distinct structure and property of these two CDs, in which CDs-1 display blue fluorescence with the average diameter of about 1.73 nm, while CDs-2 possess larger size (av. 2.41 nm) because of the larger conjugated structures and exhibit green fluorescence. The successful doping of N on the surface of CDs-2 was confirmed by characterizations of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR), which endows CDs-2 improved detection performance than that of CDs-1. CDs-2 could selectively and sensitively detect iron(III) and copper(II) ions, and the limit of detection (LOD) can reach 73 nM and 61 nM with a liner range from 0 to 20 μM and 0 to 50 μM, respectively. The fluorescence static quenching effect and the formation of the ground-state complex may explain the quenching mechanism of CDs-2 in this process. This work demonstrates the more possibilities of applying the low-cost waste and developing high-efficiency CDs-based luminescent sensors. [ABSTRACT FROM AUTHOR]

As an important strengthening phase in Al-Ca eutectic alloy, the mechanical properties of Al4Ca phase are important for its engineering application. The effects of Cu, Zn, Mg, Fe and Mn doping on mechanical properties and electronic structures of Al4Ca phase are investigated in detail based on DFT calculations. The negative mixing enthalpy and cohesive energy of all Al4(Ca,m) phases show that the substitution of Ca by m (m = Cu, Zn, Mg, Fe and Mn) is energetically favorable at 0 K. The modulus and hardness values of Al4(Ca,m) are improved from 43.3, 2.73 GPa to 47.4, 2.99 GPa, 52.3, 3.3 GPa, and 70.6, 4.45 GPa by Mg, Fe and Mn doping, while they are decreased to 35.1, 38.2 and 2.21, 2.4 GPa by Cu and Zn doping. Based on Pugh ratio (B/G, 1.75) and Poisson's ratio (σ, 0.26) criteria, all Al4(Ca,m) phases are ascertained as ductile materials. Cu and Zn can increase the ductility of Al4Ca and the situation is in contrary after doping of Mg, Fe and Mn. Mn is the ideal element for increasing fracture toughness and decreasing the mechanical anisotropy of Al4Ca among these elements from calculation results. The calculated electronic structures show that the mechanical properties evolution of Al4(Ca,m) phases are primarily attribute to the variation of Al-m bonds. [ABSTRACT FROM AUTHOR]

Magnetic core–shell nanomaterial Fe3O4–SiO2–Cu2O/Cu was first successfully synthesized using an economical strategy. Using Fe3O4 as a magnetic center for easy recycling and SiO2 as the connecting layer, Cu elements were evenly and steadily distributed on the surface of the Fe3O4–SiO2–Cu2O/Cu core–shell nanostructure. The magnetic catalyst performed outstanding catalytic reduction activity for 4-nitrophenol (4-NP), and the complete catalytic reduction of 4-NP was achieved within only 5 min. What's more, the catalyst could be well recycled, and the catalytic efficiency remained more than 90% after being reused 24 times. [ABSTRACT FROM AUTHOR]

Residual stress greatly influences the warping behavior of lead frame copper alloys and can be evaluated by nanoindentation. In this study, the residual stresses are calculated by Suresh's model, Wang's model, and Ghanbari's model. In addition, an elastic work model, based on indentation unloading curve, is proposed. The results reveal that the residual stresses of all samples are determined to be compressive stresses. Furthermore, Wang's model and the elastic work model may be considered to be most appropriative for the residual stress assessments in lead frame copper strips. More importantly, for the lead frame copper alloys, there will be an obvious pile-up effect during the indentation process. This effect is utilized to correct residual stresses in Suresh's model, and identified that residual stresses decrease by about 300 MPa. This study has great significance for the development of the residual stress models by nanoindentation. [ABSTRACT FROM AUTHOR]

Flexible smart-window technology is promising in controlling the building energy in an intelligent city; however, fabricating a high-performance flexible smart windows through a simple, cost-effective, and scalable method is a challenge. Herein, we present an approach for fabricating a flexible smart window that can achieve a maximum difference of the transparency between the "ON" and "OFF" state (Δ TON-OFF) of 69.6% at a low applied voltage (35 V) using flexible transparent electrodes (FTEs) of copper nanowires/multi-walled carbon nanotubes (Cu NWs/MWCNTs). MWCNTs were coated on the nanowire network by spin coating to form bridges between the Cu NWs, resulting good optoelectrical properties of the FTE (a sheet resistance of 22 Ω /sq at 90% of the transmittance) and uniform electric field of the device. Moreover, MWCNTs enable excellent mechanical stability under a bending test of over 5000 cycles of the electrodes. As a result, the flexible smart window can achieve high output performance, mechanical durability, and fast response. Furthermore, our method is in the solution phase and operates at room temperature (25 °C), which indicates the suitability of flexible smart windows for commercial applications. [ABSTRACT FROM AUTHOR]

Asymmetric particles (Janus particles) with discrete surface regions owning different chemical compositions or physical shapes have attracted increasing attention in the last two decades. Exploring novel strategies for synthesis of Janus particles is a great challenge due to somewhat complicated process and taking long time. In this work, several micron-scale Janus particles were rapidly prepared by photo-initiated seeded swelling polymerization for the first time, using glycyl methacrylate (GMA) as monomer and pentaerythritol tetraacrylate (PET4A) as crosslinker. After swelling of the seeds, the polymerization could be completed with ultraviolet light of 365 nm for 15 min. The effects of seed amount, molar ratio of monomer to crosslinker, volume ratio and type of porogenic agent and illumination time on Janus particle morphology were systematically investigated, and the resulting Janus particles with semi-raspberry-like morphology could be adjusted. Additionally, Janus particles were modified with a layer of polymer brush by surface-initiated atom transfer radical polymerization. The as-synthesized Janus@poly(GMA)-EDA was utilized for the adsorption of Cu(II) ion, and the adsorption capacity reached 349.6 mg g−1, indicating that Janus@poly(GMA)-EDA exhibited great application potential for heavy metal removal. [ABSTRACT FROM AUTHOR]

Multi-material structures make it possible to obtain effective solutions to engineering problems by combining the benefits of different materials to meet the requirements of different working conditions. The aim of this multifunctional 420 stainless steel-copper structure is to create a hybrid solution in which copper acts as heat-transfer enhancer (through cooling channels) while maintaining the required mechanical properties of the steel matrix. This work focuses on a combined engineering process consisting of CNC machining through holes on a 420 stainless steel surface substrate and subsequent filling with copper by hot pressing. The influence of the copper filling on the physical, chemical, microstructural, mechanical, and thermal properties of this multi-material solution was analysed. The machined area (5% of the total surface area) consisted of nine holes with a diameter of approximately 1 mm. The multi-material samples showed high densification, homogeneous microstructures, and a well-defined and sharp interface between the two materials. The microhardness values measured for the 420 stainless steel and copper were 759 and 57 HV, respectively, and the thermal conductivity of the multi-material was ≅ 59% higher than the 420 stainless steel (39.74 and 16.40 W/m K, respectively). [ABSTRACT FROM AUTHOR]

The electrodeposition rate is important for improving the application prospects and fabrication efficiency of Cu electrodeposition. However, high electrodeposition rates may result in reduced mechanical properties and surface quality of the deposited layer. In this article, high-speed electrodeposition of bright Cu with low surface roughness and excellent mechanical properties was achieved using friction-assisted electrodeposition (FAED). The mechanisms of the high luminance and low roughness on the deposited surface after FAED were analyzed from the perspective of geometrical optics. The results showed that mirror luminance with a low roughness of Ra 0.613 μm was obtained with hard particles by reducing the diffuse reflection and bulges on the deposited surface. The electrochemical behaviors of FAED and traditional electrodeposition were compared using electrochemical tests. The results indicated that hard particles increased the limiting current density by thinning the diffusion layer; thus, a high electrodeposition rate of 7.1 μm min−1 was realized in FAED because it could proceed at higher current densities. Moreover, FAED achieved grain refinement and heterostructures because hard particles allowed periodic overpotential by disturbing the electroreduction process. The heterostructure provided an unusual synergy between high strength (486 MPa) and superior ductility (20.1%) by back-stress strengthening and hardening. The results not only broaden new understanding in the mechanism of FAED, but also lay the foundation for extending the applications of Cu electrodeposition. [ABSTRACT FROM AUTHOR]

This study investigated the effect of ferrite band formation for preventing the diffusion of molten copper (Cu) into steel grain boundaries. To this end, the gas tungsten arc welding method was exploited for cladding ERCuAl-A2 and ERCuSi-A filler metals on plain carbon steel. Then, microstructure, cracks, and ferrite bands were characterized and the conditions for the formation of 4.20 wt.% Si in the ferrite band were evaluated using the design of experiments methodology. The results indicated that when cladding with 7.60 wt.% Si takes place with minimum heat input (0.9 kJ/mm), the penetration of the molten Cu will not occur in the grain boundaries of the heat-affected zone in the presence of the %overlap. [ABSTRACT FROM AUTHOR]

The φ16 mm single-crystal copper rod billet was prepared by the heated mold horizontal continuous casting process. After cold drawing + 600 °C× 5 s annealing to φ1 mm, the annealed φ1 mm single-crystal copper processing wire was cold drawn to φ0.2 mm (φ1 mm → φ0.2 mm), and the electrical conductivity, tensile strength and microstructure evolution of single-crystal copper wire were compared and analyzed. The research shows that the conductivity of the as-cast single-crystal copper rod is 102.1% IACS, the tensile strength is 141 MPa, the conductivity is as high as 97.26% IACS, after cold drawing to φ0.2 mm, and the tensile strength is greatly increased to 506 MPa. Compared with the as-cast properties, the electrical conductivity of the as-drawn wire is only reduced by 4.7%, while the tensile strength is increased by 258.9%. The as-cast rod exhibits typical characteristics of single-crystal copper; with the increasing amount of deformation, the microstructure evolves in the following form: dislocations generated by slip entanglement into dislocation cells → microstrip structure → layered structure → twin structure. A prediction model for the strength and electrical conductivity of single-crystal copper wire was constructed. The results show that grain refinement strengthening and dislocation strengthening are the key factors affecting the strength and conductivity of single-crystal copper wire, when deformed to φ0.2 mm, and twinning strengthening is superimposed in the above strengthening mechanism. [ABSTRACT FROM AUTHOR]

Organic pollutants have been a significant source of concern in recent years due to their facile dissemination and harmful effects. In this work, two different metal–organic frameworks (MOFs) were initially prepared by hydrothermal treatment, namely aluminum trimesate (MIL-100(Al)) and copper trimesate (HKUST-1). These materials were subsequently submitted to a post-synthetic modification step to grow titania nanoparticles on their surface. Anatase nanoparticles with sizes around 5 nm were successfully anchored on MIL-100(Al), and the concentration of TiO2 in this sample was about 68 wt.%. This is the first time that this composite (TiO2@MIL-100(Al)) is reported in the literature. It showed an improved photocatalytic activity, removing 90% of methylene blue (kapp = 1.29 h−1), 55% of sodium diclofenac (kapp = 0.21 h−1), and 62% of ibuprofen (kapp = 0.37 h−1) after four hours of illumination with UV-A light. A significant concentration (14 µM) of reactive oxygen species (ROS) was detected for this composite. HKUST-1 showed a structural collapse during its post-synthetic modification, leading to a non-porous material and providing fewer sites for the heterogeneous nucleation of titania. This behavior led to a low concentration of rutile nanoparticles on HKUST-1 (9 wt.%). However, the obtained composite (TiO2@HKUST) also showed an improved photoactivity compared to HKUST-1, increasing the photodegradation rates evaluated for methylene blue (0.05 h−1 vs. 0.29 h−1), sodium diclofenac (negligible vs. 0.03 h−1), and ibuprofen (0.01 h−1 vs. 0.02 h−1). This work brings new insights concerning the preparation of photocatalysts by growing semiconductor nanoparticles on trimesate-based MOFs. [ABSTRACT FROM AUTHOR]

To achieve superior thermal and mechanical properties of copper-bonded (Cu-bonded) Si3N4 substrate, a pressure-assisted direct bonded Cu (DBC) technique was applied to bond Cu foil with Si3N4 plate. The effects of oxide layer (SiO2) thickness of Si3N4 plate on the microstructure, thermal and mechanical properties of the Si3N4-DBC samples were investigated. The successful bonding of Cu foil to Si3N4 plate was confirmed by the presence of the interfacial products of Cu2MgSiO4 and CuYO2. Additionally, it was demonstrated that a thin SiO2 layer can result in a discontinuous distribution of interfacial products while a thick one can lead to the formation of pores in SiO2 layer. Notably, the sample prepared by Si3N4 plate with 5-μm-thickness SiO2 layer and Cu foil with 5.9-μm-thickness oxide layer (Cu2O) exhibited the optimally comprehensive properties with thermal conductivity of 92 W·m−1·K−1 and shearing strength of 102 MPa, which demonstrates significant promise for application in power electronic modules. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu2O) nano- and microstructures possess unique properties that may find a variety of applications. Environmentally benign synthesis of Cu2O with well-controlled morphology is highly desirable. In this study, Cu2O crystals with tunable shapes are synthesized using cellulose nanofibrils (CNFs) as a shape regulator and the sole reducing agent in aqueous environment. By simply increasing Cu2O precursor concentration, the Cu2O crystals evolved from octahedra to cuboctahedra, and finally cubes, accompanied with increasing size from nano- to microscale. The selection of Cu chelating agent (sodium tartrate or potassium sodium tartrate) affected the crystal growth rate. Transition in the relative intensities of the (111) and the (200) crystalline peaks in their XRD patterns was consistent with the morphology change. During the growth of crystals, CNFs were preferably bound to the {111} crystalline facet. The introduction of KBr to the reaction system produced short hexapods. The resultant CNF-Cu2O hybrids were incorporated into waterborne polyurethane (WPU) films. Even with 0.5 wt% CNF-Cu2O, the WPU film showed significant enhancement in modulus, strength and elongation at break. This work proves the possibility of controlled growth of Cu2O particles aided by CNFs and provides a new strategy for improving the performance of eco-friendly WPU films. [ABSTRACT FROM AUTHOR]