Dendritic Copper Research Articles

Towards the I n-Operando Observation of Lithium Dendrite Growth Via X-Ray Computed Tomography

The formation of lithium dendrites causes significant safety concerns in current lithium ion cells and prevents the implementation of commercial lithium metal batteries. To better understand this phenomenon, we are using nanoresolution x-ray computed tomography (nano-CT) to observe the in-operando nucleation and growth of dendrites during lithium deposition. Preliminary results of lithium films deposited ex-situ reveal that different deposition conditions affect not only the surface morphology but also subsurface features. Figure 1 displays the results of cycling the lithium film at high rates: the higher rate sample shows a dramatic increase in thickness and porosity within the film. The observational cell can also be used to observe other degradation processes occurring within lithium-ion batteries such as the deposition of copper dendrites during an overdischarge event. We will show preliminary results on the effect of deposition conditions (rate, temperature, etc.) on the surface and subsurface morphology of the lithium. From this, we are able to investigate how suppression methods such as electrolyte composition affect these features and develop more targeted strategies at dendrite prevention. Figure 1

In-Operando Imaging of Electrodeposition and Dendrites Using Nanoscale X-Ray Computed Tomography

The widespread implementation of lithium-ion batteries in systems ranging from portable electronics to electric vehicles has generated a remarkable demand for batteries with improved durability and performance. In order to satisfy said demand, the issue of dendrite formation must be addressed; dendrite growths inside batteries have been observed to create an internal short circuit that results in catastrophic failure.1 Consequently, dendrite propagation not only poses a significant safety hazard to existing lithium-ion batteries, but also is detrimental to the development of next-generation lithium based energy storage technologies such as lithium-air batteries. A better understanding of dendrite nucleation and growth behavior through direct visualization is crucial to developing effective dendrite mitigation techniques. Prior studies observed these phenomena using electron microscopy2 and micro-scale resolution X-ray computed tomography (micro-CT).3,4 These approaches present distinct challenges, including the vacuum environment of electron microscopes2,5 and insufficient resolution of micro-CT to image nucleation events.3 An interesting alternative is the use of the nano-scale resolution X-ray CT (nano-CT) that allows for three-dimensional observations within opaque materials at high resolution (50 nm) with any electrolyte with controlled environmental conditions. In this study, an in-operando cell for nano-CT imaging was designed and fabricated, in which the working electrode is prepared on a metal wire placed within electrolyte contained by a sealed capillary. This work addresses the particular challenges of preparing in-operando electrochemical cells for lab-scale nano-CT instruments, which include sealing, limited cell size, and the beam path length through the sample. Additional considerations include the development of high temporal resolution 4D (3D plus time) reconstruction algorithms to address the longer exposure times of lab-scale instruments. Preliminary experiments demonstrating these capabilities include the imaging of dendritic copper electrodeposition using copper wires and aqueous copper sulfate electrolyte. Figure 1 shows the images of the in-operando copper dendrite growth acquired using the nano-CT with a 65 mm field of view and an exposure time of 10 s. The results in Figure 1f show that following the initial cell transient, the cell current increases with the corresponding increased surface area of the dendrites.

Fabrication of dendritic silver-coated copper powders by galvanic displacement reaction and their thermal stability against oxidation

Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a galvanic displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the galvanic displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150°C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.

Dendritic copper phthalocyanine with aggregation induced blue emission and solid-state fluorescence

In this work, dendritic copper phthalocyanine (CuPc) showing obvious aggregation induced emission (AIE) and strong solid-state fluorescence was synthesized. It was found that synthesized CuPc can be easily solubilized in polar aprotic solvent, where no fluorescence signal was detected. Interestingly, both the CuPc aggregates in solution and solid-state powder exhibited strong fluorescence emission around 480nm, which should be attributed to the restriction of intramolecular rotation as rationalized in aggregation induced emission framework. Meanwhile the obvious crystalline enhanced solid-state fluorescent emission is observed for CuPc powder.

Thermally induced oxidative growth of copper oxide nanowire on dendritic micropowder and reductive conversion to copper nanowire

Copper nanowires (NWs) were constructed on a dendritic copper powder precursor by a facile thermal oxidation-reduction method. First, copper oxide NWs were grown from high purity dendritic copper powder by thermal oxidation at 500°C. Next, these oxide NWs were reduced to copper NWs under a hydrogen flow at two different temperatures of 220 and 500°C. Oxide NW diameters distribution was in the range of 50-105 nm with length ranging from 1 to 5 μm while copper NWs were shorter and wider. A time-dependent study of oxide NWs growth was carried out. The morphology, composition and crystal structure of the resulting products were characterised by X-ray diffraction and scanning electron microscope. The results indicated that the final product of oxidation process was dispersed cupric oxide (CuO) NW whose density and length increased with time. Furthermore, it was observed that as the reduction temperature increased, the copper NW melted and adhered to the powder surface.

Soldering aluminium to copper with the use of interlayers deposited by cold spraying

The article presents the application of interlayers deposited by Low Pressure Cold Spraying (LPCS) in the soldering process. The problems concerning soft soldering of aluminium and copper were indicated and a solution with the use of metallic and composite interlayers was proposed. Wettability and spreadability tests with selected solders were performed to evaluate a solderability of various aluminium and copper LPCS coatings. Light and scanning microscopes were used to analyze solder dissimilar Al–Cu joints with previously deposited LPCS interlayer. What is more mechanical properties of the joints, e.g. microhardness and shear strength, were examined. Strength of the soldered Al–Cu joints with the LCPS interlayer highly depend on shape of powder used in spraying process. The joints with the interlayer sprayed with dendritic copper powder have low strength of about 20MPa. However, the strength of soldered joints with the LPCS interlayer of spherical copper powder is significantly higher and amounts to 36.7MPa.

Fabrication of different copper nanostructures on indium-tin-oxide electrodes: shape dependent electrocatalytic activity

This paper describes the fabrication of cubic, spherical, dendritic and prickly copper nanostructures (CuNS) on indium-tin-oxide (ITO) substrates by electrodeposition and their electrocatalytic activity towards the oxidation of glucose and hydrazine. CuNS with different shapes were fabricated on ITO substrates by using different applied potentials of +0.10, −0.10, −0.30 and −0.50 V for 400 s in the presence of 10 mM CuSO4 and 0.1 M H2SO4. The formed CuNS were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), X-ray photoelectron spectroscopy (XPS) and electrical impedance spectroscopy (EIS). SEM images showed that cubic, spherical, dendritic and prickly CuNS were formed at applied potentials of +0.10, −0.10, −0.30 and −0.50 V, respectively. XPS showed characteristic peaks at 935 and 955 eV corresponding to Cu(0). The dendritic CuNS modified electrode exhibits a higher heterogeneous electron transfer rate constant of 3.70 × 10−7 cm s−1 and an electroactive area of 51.32 cm2 when compared to other CuNS modified electrodes. Further, the electrocatalytic activity of the different shaped CuNS modified ITO electrodes was examined towards the oxidation of glucose and hydrazine. Interestingly, the dendritic CuNS modified ITO substrate dramatically enhanced the oxidation currents of both glucose and hydrazine and also shifted their oxidation potential towards less positive potential when compared to bare ITO and other CuNS modified ITO substrates. The formation of dendritic CuNS was optimized with respect to deposition time, anion and pH and was monitored by SEM. Based on the results, a plausible mechanism for dendritic CuNS formation was proposed.

Solution chemistry-based nano-structuring of copper dendrites for efficient use in catalysis and superhydrophobic surfaces

Solution chemistry-based nano-structuring of Cu dendrites is exploited to enhance their efficiency in applications of catalysis and superhydrophobicity.

Preparation of Transparent Conducting Films Using Dendritic Copper Nanowaires Prepared by Electrosynthesis

Preparation of Transparent Conducting Films Using Dendritic Copper Nanowaires Prepared by Electrosynthesis

AN APPROACH TO IDENTIFY AND ESTIMATE THE BONDING OF COPPER AND ALUMINUM POWDERS

Ultrasonic powder consolidation (UPC) is a novel rapid, full-density powder consolidation process in which metal powders confined in a die under uniaxial loading is subjected to ultrasonic vibration at low temperature for a few seconds or less. In this research, copper powders with dendritic and spherical morphologies and an aluminum powder with spherical morphology were subjected to UPC under various conditions to investigate the effects of the process variables on the densification and metallurgical bonding of the compact. An ultrasonic washing test, developed in this research, was used to determine the extent of densification and bonding achieved in specimens consolidated under systematically varied UPC conditions. Hardness testing was also employed as a supplementary means for the assessment of compact density in both as-consolidated and ultrasonically washed states. The degree of metallurgical bonding was also qualitatively assessed from the fracture surfaces of manually broken specimens. With the dendritic and spherical copper powders, the minimum consolidation temperature, time and uniaxial pressure required for nearly full densification were determined to be 450 °C, 4 s and 84 MPa, respectively. The best conditions were 500 °C, 4 s and 100 MPa for both copper powders. Dendritic-powder specimens exhibited better] Densification and bonding than spherical-powder specimens above 450 °C. However, below 450 °C, the spherical powder produced better results, due probably to its higher packing geometry and repacking under the ultrasonic vibrations. With the spherical aluminum powder, specimens with best densification and bonding were obtained under the conditions of 400 °C, 2.5 s and 80 MPa. Compact densification generally requires a good amount of powder deformation. In UPC, this occurs very quickly in a fraction of a second if consolidation temperature is sufficiently high. However, a high degree of compact densification does not necessarily assure good metallurgical bonding. Bonding must be preceded by the formation of nascent metal-to-metal contact of powder particles, which requires good compact densification. Thus, densification is only a necessary condition for bonding. For the copper compacts, metallurgical bonding, at a given temperature, increased with increasing consolidation time, indicating that bonding is a thermally activated

Effect of Particle Size and Shape on Properties of Copper – Graphite Composites

The present work aims to study the effect of particles shape and size of copper powder on physical, mechanical properties and wear resistance of copper-13vol%graphite composites prepared by powder metallurgy technique.Spherical and dendritic copper powder particles were used as a matrix besides a mixture of both shapes with three particle size ranges [(25>),(38-45),(53-63)]m. 13vol%graphite powder with a grain size of(63 (≤ was added as reinforcement. All powder mixtures were mixed mechanically for 2 hours. The mixed powders were cold pressed uniaxially at (700Mpa) for 30seconds and sintered at (900 oC) for one hour. The results showed that the relative density, both electrical and thermal conductivities and compressive strength of dendritic copper composites are higher than those of spherical copper composites, for example, the maximum values for both electrical and thermal conductivities for dendritic copper (53-63)m+13vol%graphite composite were 36.01 (.m)-1, 295.55 W/m.oK respectively, while wear rate of dendritic copper composites was lower than that of spherical copper composites where the minimum value for dendritic copper composites was (1.068×10-9 g/cm) for dendritic copper (53-63)m+13vol%graphite composite. It was found through the results of the present work that relative density, hardness and compressive strength increases with decreasing copper particle size. On the other hand an improvement in wear resistance was found on decreasing the particle size.

Electrochemical migration behavior and mechanism of PCB-ImAg and PCB-HASL under adsorbed thin liquid films

The electrochemical migration (ECM) behavior and mechanism of immersion silver processing circuit board (PCB-ImAg) and hot air solder leveling circuit board (PCB-HASL) under the 0.1 mol/L Na2SO4 absorbed thin liquid films with different thicknesses were investigated using stereo microscopy and scanning electron microscopy (SEM). Meanwhile, the corrosion tendency and kinetics rule of metal plates after bias application were analyzed with the aid of electrochemical impedance spectroscopy (EIS) and scanning Kelvin probe (SKP). Results showed that under different humidity conditions, the amount of migrating corrosion products of silver for PCB-ImAg was limited, while on PCB-HASL both copper dendrites and precipitates such as sulfate and metal oxides of copper/tin were found under a high humidity condition (exceeding 85%). SKP results indicated that the cathode plate of two kinds of PCB materials had a higher corrosion tendency after bias application. An ECM model involving multi-metal reactions was proposed and the differences of ECM behaviors for two kinds of PCB materials were compared.

A dendrite-suppressing composite ion conductor from aramid nanofibres.

Dendrite growth threatens the safety of batteries by piercing the ion-transporting separators between the cathode and anode. Finding a dendrite-suppressing material that combines high modulus and high ionic conductance has long been considered a major technological and materials science challenge. Here we demonstrate that these properties can be attained in a composite made from Kevlar-derived aramid nanofibres assembled in a layer-by-layer manner with poly(ethylene oxide). Importantly, the porosity of the membranes is smaller than the growth area of the dendrites so that aramid nanofibres eliminate 'weak links' where the dendrites pierce the membranes. The aramid nanofibre network suppresses poly(ethylene oxide) crystallization detrimental for ion transport, giving a composite that exhibits high modulus, ionic conductivity, flexibility, ion flux rates and thermal stability. Successful suppression of hard copper dendrites by the composite ion conductor at extreme discharge conditions is demonstrated, thereby providing a new approach for the materials engineering of solid ion conductors.

Base-free Knoevenagel condensation catalyzed by copper metal surfaces.

For the first time Knoevenagel condensation has been catalyzed by elemental copper with unexpected activity and excellent isolated yields. Inexpensive, widely available copper powder was used to catalyze the condensation of cyanoacetate and benzaldehyde under mild conditions. To ensure general applicability, a wide variety of different substrates was successfully reacted.

A New Method for Controlling the Quantized Growth of Dendritic Nanoscale Point Contacts via Switchover and Shell Effects

We report on quantum electrical characteristics of dendritic copper point contacts (PCs) formed through an electrochemical process via a new cyclic switchover effect that is demonstrated by the occurrence of steps in the time dependence of the dendritic-PCs conductance. We show that this quantization of the electrical conductance is due to an electronic shell effect governing the dendrite growth. The cyclic variations of conductance during dendritic PCs electrosynthesis offer the possibility for forming nanostructures of preassigned sizes controlled through their electrical resistance.

The effect of chloride ion concentration on electrochemical migration of copper

The effect of chloride ion concentration of electrochemical migration (ECM) was investigated on copper applying in situ electrochemical, optical and scanning electron microscopy—energy dispersive X-ray spectroscopy methods. An unexpected phenomenon was found: copper dendrite grows not only at low chloride concentration, but also at high and even saturated chloride concentrations, although it is generally suggested that the growth of copper dendrite through ECM does not take place in high chloride concentration solutions. Reactions have been proposed to explain the ECM of copper under different chloride concentration levels.

Numerical and experimental analysis of copper particles velocity in low-pressure cold spraying process

Thermodynamic aspects of low-pressure cold spraying process with air as a working gas were simulated using 1-D isentropic approximation and ANSYS Fluent CFD ver. 14.5 software. The simulation was completed with the help of Abaqus CAE software, which was used to find out the parameters causing adiabatic shear instability. The critical velocity of spherical and dendritic copper particles was specified. The experimental verification of the simulation was realized using a self-built CCD camera-based diagnostic system with laser light illumination. Moreover, the experimental investigation of copper particles after impact onto substrate was realized with the use of scanning electron microscope (SEM). The carried investigation proofed the important difference in impact behaviour between dendritic and spherical powders.

Dendritic Copper Catalysts for Homogeneous Click Chemistry in Water

Dendritic Copper Catalysts for Homogeneous Click Chemistry in Water

Comparative analysis of the polarization and morphological characteristics of electrochemically produced powder forms of the intermediate metals

The polarization and morphological characteristics of powder forms of the group of the intermediate metals were examined by the analysis of silver and copper electrodeposition processes at high overpotentials. The pine-like dendrites constructed from the corncob-like forms, very similar to each others, were obtained by electrodeposition of these metals at the overpotential belonging to the plateaus of the limiting diffusion current density. The completely different situation was observed by electrodeposition of silver and copper at the overpotential outside the plateaus of the limiting diffusion current density in the zone of the fast increase of the current density with the overpotential. The silver dendrites, very similar to silver and copper dendrites obtained inside the plateaus of the limiting diffusion current density, were obtained at the overpotential outside the plateau. Due to the lower overpotential for hydrogen evolution for copper, hydrogen produced during copper electrodeposition process strongly affected the surface morphology of copper. The same shape of the polarization curves with the completely different surface morphology of Cu and Ag electrodeposited at overpotentials after the inflection point clearly indicates on the importance of morphological analysis in the investigation of polarization characteristics of the electrodeposition systems. Role of hydrogen as crucial parameter in the continuous change of copper surface morphology from dendrites to the honeycomb-like structures was investigated in detail. On the basis of this analysis, the transitional character of the intermediate metals between the normal and inert metals was considered. The typical powder forms characterizing electrodeposition of the intermediate metals were also defined and systematized.

Study on Thermal Stability of Dendritic Silver-Coated Copper Powders Fabricated by Galvanic Displacement Reaction

Metals of Group IB due to their higher electrical and thermal conductivities have been thoroughly studied. Particularly, silver electronic slurry extensively used as electrode material in various resistance devices and electromagnetic interference(EMI) shielding materials. But Ag ions cause electro-migration phenomena in hot and humid conditions, which results in decreasing the conductivity and increasing the coating resistance in certain conditions. Copper relatively lower in cost and having good conductivity as silver, but the problem is copper oxidizes when exposed to air. To prevent oxidation of copper, silver coating on copper powder have been reported in many articles. In structural perspective, the dendritic structure has many superior properties, such as large surface area and good conductivity. Therefore, it is commendable to explore the mechanism of dendritic copper metallic materials formation. In this presentation, we are reporting a simple fabrication method for copper powder and silver coated copper powder with dendritic morphology at low temperature. To improve the dendritic structure, the galvanic displacement reaction and hydrogen evolution reactions have been applied together. The formation mechanism of Cu dendritic structures on the basis of effect of concentration, termination time, anion concentration, and additives have been prudently analyzed. In addition, we have also analyzed the thermal stability of silver-coated copper powders performance at different temperature. Figure 1. SEM images of (a) dendritic copper powders and (b) cross section of silver-coated copper powders fabricated by galvanic displacement reaction.