Pulse Reverse Electrodeposition Research Articles

Achieving exceptional strain-hardening ability in nanocrystalline Ni–W coatings through compositionally modulated multilayer approach

Nanocrystalline Ni–W coatings show exceptional strength; however, they exhibit poor toughness due to limited ductility and high residual stresses which impede their use in practical applications as a potential hard chrome replacement. In the present study, compositionally modulated multilayer (CMM) coatings with alternate layers of Ni-1 at% W (soft) and Ni-15 at% W (hard) of three different layer thicknesses of 1, 0.5, and 0.1 μm are developed by pulse reverse electrodeposition to achieve the strength-ductility synergy, thereby enhanced wear resistance. Microcompression test results reveal that all the CMM coatings exhibit remarkably higher strain-hardening ability than the homogenous coatings. Significant fluctuations in the strain-hardening rate and a positive shift in the onset stress for the work-hardening stages were observed with the layer thickness. This suggests a strong interplay between the hard and soft layers on the deformation characteristics of multilayer coatings. Detailed electron microscopy of the cross-section of the deformed micropillars shows substantial evidence of co-deformation of both layers. A mechanism is proposed to explain the enhanced strain-hardening in multilayers involving the strength incompatibility arising in the layers leading to lateral constraints, resulting in strain gradient plasticity, stabilizing of local shear by the soft layers, and the barrier effect of the interfaces.

Improving the Magnetic Properties of Electrodeposited Fe-55wt%Ni Alloy via Abnormal Grain Growth Induced by Second-Phase Particles

In this study, pulse reverse current electrodeposition was employed to fabricate Fe-55 wt%Ni alloy. Abnormal grain growth induced by the precipitation of second-phase particles during annealing resulted in a coarse-grained electrodeposited Fe-55 wt%Ni alloy. The grain evolution process during annealing was investigated, and the temperature for abnormal grain growth was determined through the high-temperature confocal microscopy technique. Subsequently, the mechanism of abnormal grain growth was investigated. The results suggest that abnormal grain growth occurs at approximately 1003 K, attributed to the preferential growth of (110) oriented grains due to local strain energy changes caused by the precipitation and coarsening of the second-phase particles (MnS). The preferred orientation of the grains transitioned from (111) to (110). Annealing at 1073 K for 2 h resulted in an average grain size increase to approximately 200 μm. Under these conditions, the magnetic properties of the alloy reached optimal levels, with a magnetization saturation strength of 186.7 emu g−1 and a coercivity of less than 1 Oe. This research presents a novel approach to preparing coarse-grained electrodeposited Fe-Ni alloys, significantly enhancing their magnetic properties.

Novel paddy-like Bi-Sb-Cu alloy fabricated via pulse reverse potential electrodeposition enabling high-performance sodium-ion batteries

Sodium-ion batteries (SIBs) have gained remarkable interest as cost-effective and scalable energy storage devices. Nevertheless, their further application has been significantly hindered due to the limited selection of desirable anode materials that can provide both high capacity and excellent cycling stability. Herein, we developed a hierarchical paddy-like Bi42.3Sb35.2Cu22.5 alloy anode on Cu foil via template-free pulse reverse potential electrodeposition. The Bi42.3Sb35.2Cu22.5 anode obtains a considerable specific capacity of 529.5 mAh·g−1 after 120 cycles with a remarkable capacity retention of 95.5 %, signifying a capacity loss of only 0.0375 % per cycle. However, Bi44.9Sb55.1 anodes obtained by the pulse potential electrodeposition strategy reveal a conventional irregular cluster structure, delivering only 64.5 mAh·g−1 after 100 cycles and also demonstrating inferior rate performance compared to Bi42.3Sb35.2Cu22.5 anodes. The enhanced cycling performance of the paddy-like Bi42.3Sb35.2Cu22.5 anode is primarily attributed to the introduced Cu-doped network facilitating the rapid diffusion of Na+ and also ensuring the stability of the electrode structure. Moreover, the unique paddy-like structure of Bi42.3Sb35.2Cu22.5 mitigates volume expansion-related stress and facilitates efficient charge transport through open channels. This is further corroborated by conducting CV measurements, indicating a greater capacitive contribution in the case of the Bi42.3Sb35.2Cu22.5 electrode compared to the Bi44.9Sb55.1 electrode. Additionally, SEM images show a stabilized surface morphology for the Bi42.3Sb35.2Cu22.5 electrode after cycling, demonstrating improved electrochemical performance. This work offers new insights into the development of high-performance anode materials for SIBs.

Cu microvia filling by pulse-reverse electrodeposition with a single accelerator

Cu electrodeposition processes are widely employed to achieve defect-free interconnections in electronic devices. Typically, combinations of three additives—an accelerator, a suppressor, and a leveler—are used for bottom-up filling of Cu in microscaled features. However, the use of multiple additives adds complexity to electrolyte maintenance and can lead to reliability issues in the process. To address this challenge, we have developed a single-accelerator filling technique using pulse-reverse electrodeposition for microvias. During pulse-reverse electrodeposition, the anodic steps produce a large amount of Cu+ ions near the electrode surface. These Cu+ ions can form complexes with Cl− ions or CuCl layers, thereby enhancing the adsorption of the accelerator, SPS. This phenomenon depends on the electrolyte convection. Under strong forced convection, Cu-Cl species are removed, leading to subsequent deactivation of SPS, whereas Cu-Cl species remain stable under mild convection conditions. Based on this convection-dependent behavior of SPS and Cl, Cu electrodeposition is promoted at the bottom of microvias while the SPS is selectively deactivated outside the microvias where the strong electrolyte motion exists. As a result, without any polymeric suppressor and organic leveler, the microvias are successfully filled with Cu.

Enhanced solid particle erosion resistance of nanocrystalline Ni-W coatings through multilayer approach

Electrodeposited nanocrystalline Ni-W alloy coatings are projected as potential alternatives for hard chrome (HCr) coatings owing to their comparable hardness and superior corrosion resistance. However, the limited strain hardening ability of the nanocrystalline Ni-W coatings manifests in their poor resistance towards solid particle erosion involving a high strain-rate (>103 s−1) deformation. In the present study, a novel microstructural engineering strategy has been implemented to enhance the strain hardening ability of the nanocrystalline Ni-W coatings without compromising on their strength/hardness. Ni-W multilayer coatings composed of alternatively stacked soft (2.6 GPa) and hard (8.5 GPa) Ni-W layers were developed using the pulse reverse electrodeposition technique. Further, to investigate the effect of individual layer thickness (λ), multilayer coatings with different λ were deposited. Solid particle erosion testing using the angular SiO2 particles showed that the multilayer coatings (irrespective of λ) exhibit superior erosion resistance compared to the homogeneous nanocrystalline Ni-15W at both oblique (θ = 30°) and normal (θ = 90°) impact conditions. The post-erosion microstructural analysis of the multilayer coatings revealed that the hard Ni-W layers undergo uniform strain (ε > 50 %) without cracking due to the constrained co-deformation imposed by the surrounding soft Ni-W layers. Therefore, the enhanced erosion resistance of the multilayer coatings is attributed to the effective dissipation of impact energy through co-deformation of the individual hard and soft Ni-W layers.

Electrodeposition of Cu Nanocubes in the Presence of Cl- and Br-

Electrodeposition is one of the simple methods for fabricating metal and alloy thin films. Electrodeposition is performed by applying external electrical energy to conductive substrates immersing in electrolytes containing metal precursors. Metal ions or complexes are reduced on a substrate surface and form metal films. The properties of metal thin films and surface morphology of the electrodeposit can be modulated by the parameters of electrodeposition, the composition of electrolytes, i.e., the concentrations of metal precursors and additives. Furthermore, the atomic composition of alloy films can also be easily controlled by electrochemical parameters in the electrodeposition process.1 As explained, the electrodeposition process has various advantages in producing metal thin films with desired properties. However, creating nanostructures with precisely controlling their shapes in the nm scale is relatively difficult. In colloidal syntheses, various nanocrystals, including nanowires, nanospheres, octahedrons, nanocubes, and nanoplates, can be obtained by introducing shape-directing agents.2-4 In the case of electrodeposition, the template-assisted electrodeposition method is the most common to form nanostructures,5,6 and relatively few examples of shape controlling by additives have been reported. Although the formation of metal nanowires in the presence of 3,5-diamino-1,2,4-triazole (DAT) has been recently reported,7 shape control of metal deposits by additives during the electrodeposition process is still limited to few nanostructures. Electrodeposition induces metal growth relatively faster than colloidal synthesis, and a precise nucleation step is not involved in the electrodeposition, which is critical in colloidal syntheses. In this study, we have adopted pulse-reverse electrodeposition to modulate metal nucleation at the initial stage of electrodeposition and also maximize the effects of additives. Pulse-reverse electrodeposition has been researched for controlling the properties of metal thin films and changing the adsorption of additives.8,9 Therefore, pulse-reverse electrodeposition can catch up with the shape control in colloidal syntheses. This presentation will introduce how the parameters in pulse-reverse electrodeposition and additives (halide ions) affect the shape of Cu nanocrystals. References 1) T. P. Moffat, J. J. Mallett, and S. M. Hwang, “Oxygen Reduction Kinetics on Electrodeposited Pt, Pt100− x Nix , and Pt100−xCox” J. Electrochem. Soc. 156, B238 (2009)2) Y. Xia, Y. Xiong, B. Lim, and S. E. Skrabalak, “Shape-Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?” Angew. Chem. Int. Ed. 48, 60 (2009)3) K. A. Fichthorn, Z. Chen, Z. Chen, R. M. Rioux, M. J. Kim, and B. J. Wiley, “Understanding the Solution-Phase Growth of Cu and Ag Nanowires and Nanocubes from First Principles” Langmuir 37, 4419 (2021)4) D. Huo, M. J. Kim, Z. Lyu, Y. Shi, B. J. Wiley, and Y. Xia, “One-Dimensional Metal Nanostructures: From Colloidal Syntheses to Applications” Chem. Rev. 119, 8972 (2019)5) K. R. Yeo, J. Y. Eo, M. J. Kim and S.-K. Kim, “Shape Control of Metal Nanostructures by Electrodeposition and their Applications in Electrocatalysis” J. Electrochem. Soc. 169, 112502 (2022)6) C. Liu, Z. Li, P. Yu, H. W. Wong, and Z. Gu, “Vertically Aligned and Surface Roughed Pt Nanostructured Wire Array as High Performance Electrocatalysts for Methanol Oxidation” ACS Appl. Energy Mater. 1, 3973 (2018)7) T. T. H. Hoang, S. Ma, J. I. Gold, P. J. A. Kenis, and A. A. Gewirth “Nanoporous Copper Films by Additive-Controlled Electrodeposition: CO2 Reduction Catalysis” ACS Catal. 7, 3313 (2017)8) M. J. Kim, T. Lim, K. J. Park, S. K. Cho, S.-K. Kim, and J. J. Kim “Characteristics of Pulse-Reverse Electrodeposited Cu Thin Films: I. Effects of the Anodic Step in the Absence of an Organic Additive” J. Electrochem. Soc. 159, D538 (2012)9) M. J. Kim, T. Lim, K. J. Park, O. J. Kwon, S.-K. Kim, and J. J. Kim “Characteristics of Pulse-Reverse Electrodeposited Cu Thin Film: II. Effects of Organic Additives” J. Electrochem. Soc. 159, D544 (2012) Figure 1

Cu TSV Filling with Cetyltrimethyl Ammonium Cations (CTA+) and Br-

Through silicon via (TSV) technology is essential for the three-dimensional packaging of electronic devices. After creating high-aspect-ratio vias, Cu electrodeposition is performed to achieve defect-free Cu interconnection. The most important purpose of electrodeposition process is to fill the features without any defects, and this process is called superfilling, superconformal deposition, or bottom-up filling. Since TSV is a key component for the packaging of semiconductor devices, various research on the electrodeposition process for TSV filling have been studied. Defect-free TSV filling can be achieved by introducing appropriate organic/inorganic additives into the electrolyte and the filling performance can be promoted by pulse reverse electrodeposition.1-3 Generally, it has been reported that Cu bottom-up filling at TSVs can be obtained by three-additive combinations (suppressor, accelerator, and leveler) or by using a single suppressor. Tetronic 701 is the most representative suppressor in a single-additive filling method, which was based on S-shaped negative differential resistance (S-NDR) behavior.4-6 In the case of three-additive systems, various levelers that contained ammonium functional groups, a polymeric suppressor, and an accelerator have been researched.7,8 Furthermore, it has been reported that halide ions (Br- and I-) can act as levelers for inducing Cu bottom-up filling at TSVs.9,10 This study investigated the effects of cetyltrimethyl ammonium cation (CTA+) and halide ion on TSV filling in the presence of an accelerator and polymeric suppressor. The influences of two halide ions, Cl- and Br-, on the adsorption of CTA+ and their convection dependency were studied. This presentation will introduce the electrochemical behaviors of halide ions and CTA+ and defect-free filling using the optimum combination of these additives. References M. Hayase, and K. Otsubo. "Copper deep via filling with selective accelerator deactivation by a reverse pulse" J. Electrochem. Soc.,157, D628 (2010).Q.S. Zhu, X. Zhang, C.Z. Liu, and H.Y. Liu. "Effect of reverse pulse on additives adsorption and copper filling for through silicon via" J. Electrochem. Soc.,166, D3006 (2019)Q.S. Zhu, A. Toda, Y. Zhang, T. Itoh, and R. Maeda. "Void-free copper filling of through silicon via by periodic pulse reverse electrodeposition" J. Electrochem. Soc.,161, D263 (2014)T. P. Moffat, and D. Josell. "Extreme bottom-up superfilling of through-silicon-vias by damascene processing: suppressor disruption, positive feedback and turing patterns" J. Electrochem. Soc.,159, D208 (2012)D. Joell, and T. P. Moffat. "Superconformal copper deposition in through silicon vias by suppression-breakdown." J. Electrochem. Soc.,165, D23 (2018)M. Dong, Y. Zhang, T. Hang, and M. Li. "Structural effect of inhibitors on adsorption and desorption behaviors during copper electroplating for through-silicon vias." Electrochim Acta372 (2021)M. J. Kim, Y. Seo, J. H. Oh, Y. Lee, H. C. Kim, Y. G. Kim, and J. J. Kim. "Communication—halide ions in teg-based levelers affecting TSV filling performance." J. Electrochem. Soc.,163, D185 (2016)V. Q. Dinh, K. Kondo, V. H. Hoang, and T. Hirato. "Communication—Bottom-up TSV filling using sulfonated diallyl dimethyl ammonium bromide copolymer as a leveler." J. Electrochem. Soc.,166, D505 (2019)M. J. Kim, H. C. Kim, and J. J. Kim. "The influences of iodide ion on Cu electrodeposition and TSV filling." J. Electrochem. Soc.,163, D434 (2016)M. Sung, Y. Yoon, J. Hong, M. J. Kim, and J. J. Kim. "Bromide ion as a leveler for high-speed TSV filling." J. Electrochem. Soc., 166, D546 (2019) Figure 1

Synergistic coupling of reduced graphene oxide with Ni0.85Se for highly active bifunctional electrocatalyst for water splitting

Electrochemical water splitting can provide eco-friendly fuel. Nevertheless, this method requires efficient bifunctional electrocatalysts. In this study, a bifunctional electrocatalyst was synthesized by coating Ni0.85Se and hydrothermally-reduced graphene oxide on nickel foam (NF) using two-step electrodeposition. Moreover, graphene oxide was reduced through hydrothermal means prior to the pulse reverse electrodeposition. As confirmed by FT-IR, hydrothermally and electrochemically reduced graphene oxide on NF (HERGO) reveals a higher reduction degree in comparison to electrochemically-reduced graphene oxide on NF (ERGO). Ni0.85Se covered HERGO through the on-off cathodic pulse electrodeposition. Therefore, excellent electrocatalytic activity was obtained using the synergetic effect of RGO and Ni0.85Se. The ECSA values of 431 and 3500 cm2 were attained through coating HERGO and Ni0.85Se/HERGO on bare NF, respectively. The Ni0.85Se/HERGO revealed Ƞ10 of 67 and 230 mV for HER and OER, respectively. For overall water splitting, the Ni0.85Se/HERGO ǁ Ni0.85Se/HERGO device requaired 1.533 V at 10 mA/cm2.

Fabrication of Large-Sized Invar Alloy Film with Low Thermal Expansion by Pulse Reverse Electrodeposition

Invar alloy film with low thermal expansion is a key substrate for high-resolution organic light-emitting diodes (OLEDs). The preparation of Invar alloy film by electrodeposition has attracted increasing attention due to its low cost and simple process. In this work, a large-sized (8 × 10 cm) uniform Fe-Ni alloy film was fabricated by pulse reverse electrodeposition. The effects of the electrodeposition parameters on the chemical composition and microstructure of Fe-Ni alloy films were investigated. Results showed that greater Ni2+/Fe2+ in the electrolyte, lower pulse frequency (f), smaller reverse pulse coefficient (x), and lower electrodeposition temperature (T) favored the iron content. The Invar alloy film (64 wt% Fe) was electrodeposited at T = 50 °C, x = 0.2, f = 10 Hz, and Ni2+/Fe2+ = 1.9 when the average pulse current density was 30 mA cm−2. The structure of the film was composed of a mixture of fcc and bcc phases, where (110) and (111) preferential orientations were predominant. After heat treatment in H2 at 800 °C for 120 min, the bcc phase transformed into the fcc phase, and the grain size increased (>2 μm). As a result, the coefficient of thermal expansion of the film decreased from 11 × 10−6 to 1.5 × 10−6/°C, which is close to the standard for commercial application.

(Invited) Nanocrystalline Ni-W: The Science, Commercialization and Scaling of an Electrodeposited Coating

Nanocrystalline Ni-W alloy coatings deposited using pulse-reverse electrodeposition were studied as a model nanocrystalline material 20 years ago at MIT, and commercialized by Xtalic Corporation in electronic applications beginning in 2008. Under the trade name Xtronic, these coatings provide exceptional wear resistance and barrier protection due to their extremely fine ~10 nm grain size, and have enabled significant reconfigurations of the electronic connector metallization stack in many applications from enterprise to consumer electronics. This talk will review the basic science of the Ni-W alloy system and its ability to deliver these unique properties by virtue of its nanostructure, as well as some of the electrochemical features of the process that enabled its scaling from the laboratory to hundreds of billions of individual metallized contacts. As a case study in the growth of an electrochemical nanotechnology, the talk will also review elements of technology transfer between MIT and Xtalic Corporation that helped facilitate Xtronic’s commercial emergence, including intellectual property management and ongoing basic research.

Deciphering the role of W content, triple junctions, and heat treatment on the corrosion performance of Ni–W alloy coatings used for automotive applications

In this study we focus on understanding the influence of tungsten (W) content, heat treatment and grain size on the corrosion behaviour of Ni–W coatings. Using pulse and pulse reverse electrodeposition techniques, Ni–W coatings with different W contents (3, 7.5, 12, 17, 20 and 25 at.%) were deposited from a standard ammonia-citrate bath. Coatings were heat treated at 700 °C in vacuum for 1 h and then characterized to determine the surface morphology, grain size, and phase transformations. To evaluate the corrosion performance of the coatings, potentiodynamic polarization tests were performed in 0.6 M NaCl solution. Polarization test results indicated that as-deposited Ni–W coatings had better corrosion resistance compared to heat treated coatings. In the as-deposited condition, corrosion resistance increased up to 17 at.% W. However, further addition of W decreased the corrosion resistance due to high volume fraction of triple junctions and intercrystalline regions. On the other hand, heat treated coatings suffered from micro-galvanic corrosion due to the precipitation of Ni4W and NiW phases, and therefore showed higher corrosion rates compared to as-deposited coatings. The changes observed in the corrosion behaviour of as-deposited and heat treated Ni–W coatings were rationalized based on surface composition, mixed potential theory, and triple junction corrosion theory.

Features of pulse-reverse modes for Ni–Fe nanogranular films electrodeposition: Correlation of structural parameters and MI effect

Through pulse-reverse electrodeposition with various reverse durations, the Ni–Fe films were synthesized. The film's structure was different. With an increase in the reverse duration, the average grain size and porosity increased to a certain point. As the reversal duration is increased, the porosity and average grain size decrease. Magnetic anisotropy was revealed through an analysis of magnetic characteristics. In particular, when the magnetic field was perpendicular to the samples, the remnant magnetization increased from 0.3 to 2.3 emu/g. The remnant magnetization varied from 77 to 91 emu/g with a parallel orientation. Research on the magnetoimpedance has revealed that at a frequency of 100 kHz, the magnetoimpedance coefficient is at a minimum due to resonance effects in both directions of the magnetic field. The magnetostatic model can be used to explain the mechanism of change in the magnetoimpedance in the low-frequency range. The magnetoimpedance occurs in the medium frequency range (from 10 kHz to 1 MHz) due to changes in the magnetic permeability caused by the impact of a magnetic field and an increase in current frequency, which modify the depth of the skin layer.With an increase in current frequency passing through the sample, the current density on the near-surface layer becomes non-uniform. This non-uniformity is significantly influenced by microstructure parameters such as porosity, average grain size, and the degree of texturization, all of which contribute to the conductor's impedance. It opens new direction for smart sensors development.

Bi-functional Ni-Co-P/rGO/NF flower-like structure as an electrocatalyst for hydrogen production assisted by urea oxidation reaction

Replacing the inert oxygen evolution reaction (OER) with alternative electrochemical reactions is critical for large-scale hydrogen generation. Here the Ni-Co-P flower-like nanostructure coated on reduced graphene oxide which was synthesized via two-step electrodeposition method (as Ni-Co-P/rGO/NF) is described. First, rGO was deposited on the nickel foam precursor by the pulse-reverse electrodeposition, then Ni-Co-P nano-layer by the Chronoamperometry was electrodeposited. The η10 for HER and UOR was 53 mV and 1.23 V, respectively, demonstrate enhanced electrocatalytic activity. XRD, XPS, and TEM analysis revealed that the Ni-Co-P/rGO catalyst has a flower-like structure depending on its composition. In the two-electrode cell at a voltage of 1.35 V, the generated current density of urea electrolysis (37.84 mA cm−2 in 0.33 M urea + 1.0 M KOH electrolyte) was 3.31 times greater than that of the conventional water splitting (11.41 mA cm−2). According to the findings, Ni-Co-P/rGO could be employed as a dual-functional catalyst toward UOR and HER for energy-saving and H2 generation.

Tuning formation process of void defects in microcolumn arrays via pulse reverse electrodeposition

The pulse reverse current electrodeposition process consists of two stages: the forward deposition and reverse dissolution. This study aims to understand the characteristics of forward deposition and reverse dissolution and to reveal their influences on the formation of void defects in electrodeposited microcolumn arrays. Both the simulation and experimental results show that pulse reverse current contributes to the void-free deposition of microcolumn arrays. During the deposition under forward pulse stage, the thickness of deposited layer in micro cavities via pulse reverse current is more uniform compared with direct current. Meanwhile, the dissolution behavior under reverse pulse stage is greatly determined by the reverse pulse current density. A low reverse pulse current density (1 A/dm2) leads to a slow dissolution at the mouth of micro cavities. In contrast, a high reverse pulse current density (4 A/dm2) contributes to a high electrolyte potential, as well as a rapid dissolution at the mouth of micro cavities, which helps to eliminate void defects. The experimental results exhibit that void-free microcolumn arrays with a high aspect ratio of 5:1 are obtained via pulse reverse current. This study provides a clear understanding on the formation process of void defects in microcolumn arrays via pulse reverse electrodeposition.

Pulse-reverse electrodeposition of Ni-Co/graphene composite films with high hardness and electrochemical behaviour

Pulse-reverse electrodeposition of Ni-Co/graphene composite films with high hardness and electrochemical behaviour

Pulse-reverse electrodeposition of Ni–Mo–S nanosheets for energy saving electrochemical hydrogen production assisted by urea oxidation

Electrochemical hydrogen production from water splitting is one of the effective methods for hydrogen production that has recently attracted particular attention. One of the limitations of the electrochemical water splitting method is the slow oxygen evolution reaction (OER), which leads to an increase in overpotential and a decrease in hydrogen production efficiency. Here, Ni–Mo–S ultra-thin nanosheets were synthesized using the pulse reverse electrochemical deposition technique, and then this electrode was used as an electrode material for accelerating hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Remarkably, the optimized electrode needs only 74 mV to attain the 10 mA cm−2 current density in HER and require only 1.3 V vs RHE potential in the UOR process. Also, results showed that the replacement of the UOR with the OER process resulted in a significant improvement in the electrochemical production of hydrogen in which for delivering the current density of 10 mA cm−2 in overall urea electrolysis, only 1.384 V is needed. In addition, outstanding catalytic stability was obtained, after 50 h electrolysis, the voltage variation was negligible. Such outstanding catalytic activity and stability was due to 3-D ultrathin nanosheets, the synergistic effect between elements, and the superhydrophilic/superaerophobic nature of fabricated electrode.

Strengthening of 3D printed Cu micropillar in Cu-Ni core-shell structure

Direct printing of complex 3D structures at the nano- and microscale is a promising technique for MEMS devices, small-scale sensors, and actuators. So far, most studies have been focused on printing copper (Cu) structures due to the high Coulombic efficiency compared to other conductive metals such as platinum. However, Cu suffers from low material strength, low modulus, and high strain-rate sensitivity. This work introduces a unique Cu-Ni core–shell structure for improved strength. A 3D additive-micromanufacturing technique based on localized electrodeposition was utilized to fabricate dog-bone-shaped Cu micropillars with submicron resolution. These pillars were subsequently coated with Ni by pulse-reverse electrodeposition. A combination of in-situ micropillar compression at various strain rates (0.001–500 s−1) and finite element simulations revealed remarkable strengthening in the Ni-coated Cu micropillar. Data obtained from both experiments and simulations were in good agreement, suggesting the strengthening was dominated by interface characteristics, stress redistribution, and geometrical effects. Furthermore, the study demonstrates that shape and dimension of the 3D-printed objects can be retained while increasing their strength drastically. These findings can be extended to other material systems and provide a pathway to develop strong and tough composites and metamaterials at multiple length scales for future applications.

Fabrication of corrosion-resistant conversion coating based on ZIF-8 on electro-galvanized steel utilizing pulse electrodeposition technique

In this work, through a novel method of synthesizing zeolitic imidazolate framework-8 (ZIF-8), a conversion coating (CC) was applied to a galvanized surface. A reverse pulse electrodeposition (PED) method was employed to apply ZIF-8 conversion coating in a 2-methylimidazole bath during 2, 4, and 6 h. Characterization techniques demonstrated that the ZIF-8 conversion coating (ZIF-8CC) was successfully synthesized after 6 h. The increase in hydrophilicity of the synthesized conversion coating was demonstrated by the contact angle test. The best performance of the single-layer conversion coating against corrosion was obtained in the case of ZIF-8CC@6 h. Then, an epoxy coating was applied to the samples with and without conversion coatings. The effect of the ZIF-8 conversion coating on the adhesion strength and the corrosion behavior of the epoxy coating was investigated. The results revealed the superior functioning of ZIF-8CC@6 h compared to the rest of the samples in terms of adhesion and protective performance of the epoxy coating.

Study on Pulse-Reverse Electroplating Process for the Manufacturing of a Graphene-Based Coating.

This work investigates the feasibility of increasing the electric conductivity of an AA1370 aluminium wire by using pulse-reverse electrodeposition to realize Cu-Graphene composite coating. The graphene adopted was in the form of nanoplates (GnP). To study the effects of plating parameters, a 23 factorial plan was developed and tested. During the tests, the following process parameters were varied: the current density, the frequency and the duty cycle. The ANalysis Of VAriance (ANOVA)) was adopted to evaluate their influence on the coated wires' morphology and electrical conductivity resistance. The results show that all the tested conditions allow good compactness to the coating, and the amount of graphene is well incorporated within the microstructure of the copper deposit. In addition, in the best conditions, the electrical resistivity decreases up to 3.4% than the uncoated aluminum.

Reverse voltage pulse deposition of a porous polyaniline/Mn–Co sulfide composite cathode material for modified Zn-ion hybrid supercapacitors

For expanding the working potential window and reducing the self-discharge for a Zn-ion hybrid supercapacitor, a cathode of the Mn–Co-sulfide–polyaniline (MCS–PANi) composite was prepared by the reverse voltage pulse electrodeposition method.