Nickel Plating Research Articles

Design of Self-Repairing Anode Catalysts for Alkaline Water Electrolysis with Both OER Activity and Durability Via Colloidal Self-Assembly

INTRODUCTION The demand of renewable energy is increasing, yet fluctuating power supply is one of the problems. Therefore, technology for energy storage such as alkaline water electrolysis is required. When an alkaline water electrolyzer is powered by renewable energy, electrodes degrade due to reverse current generated on shutdown.[1] We have reported self-repairing catalysts based on hybrid cobalt hydroxide nanosheets (Co-ns), and β-FeOOH nanorods (FeOOH-nr).[2,3] Our previous studies showed that Co-ns formed thick catalyst layer with high oxygen evolution reaction (OER) activity, whereas FeOOH-nr formed a thin layer with much higher OER activity than that of Co-ns. If the thickness of FeOOH-nr increases, the OER activity and durability are expected to be improved. Here, we demonstrate the design of composite catalysts, consisting of both Co-ns and FeOOH-nr. Co-ns promotes stacking of the catalysts on the electrode, and FeOOH-nr forms active sites. EXPERIMENTAL Co-ns[2] and FeOOH-nr[3] were synthesized according to the literature. Electrochemical tests were performed in a 1.0 M KOH, using a PFA three-electrode cell. A nickel plate, a nickel coil, and a reversible hydrogen electrode were used as the working, counter, and reference electrodes, respectively. The Co-ns dispersion, FeOOH-nr dispersion, or their mixture (total concentration of catalyst weights = 80 ppm) was added in the electrolyte. Catalysts were deposited by repeating the following processes 10 times according to our previous report:[2] i) chronopotentiometry at 800 mA cm– 2 for 30 min, ii) cyclic voltammetry (CV) between 0.5 and 1.8 V vs. RHE at 5 mV s– 1, iii) CV between 0.5 and 1.6 V vs. RHE at 50 mV s– 1, and iv) electrochemical impedance spectroscopy at 1.6 V vs. RHE. Furthermore, an accelerated durability test (ADT)[4] was conducted 2000 cycles to examine the degradation. RESULTS AND DISCUSSION The synthesis of Co-ns and FeOOH-nr was confirmed by XRD, FTIR, elemental analyses, and TEM. Co-ns is modified with tripodal ligand, whereas FeOOH-nr is non-modified. The electrophoretic mobilities of Co-ns and FeOOH-nr were 1.98 and –2.80 µm cm V– 1 s– 1 at pH 9.7. Because Co-ns and FeOOH-nr are oppositely charged, they are expected to be self-assembled into a composite in the electrolyte.The OER polarization curves during the repeated electrolysis are shown in the Fig. 1. The OER activity of the electrode prepared from the mixture of Co-ns and FeOOH-nr (Co-ns/FeOOH-nr molar ratio = 10) was higher than those of the electrodes prepared from only one component. The OER overpotential at 100 mA cm–2 (η 100) of the composite catalyst was 291 mV after 300 min of electrolysis. The η 100 of Co-ns and FeOOH-nr were 310 and 353 mV, respectively.The deposited amount of Fe (M Fe) and the η 100 as a function of the deposited amount of Co (M Co) is shown in the Fig. 2. The M Fe using the composite catalysts was much larger than that using FeOOH-nr only. The M Fe was 48.5 µg cm–2 when the Co-ns/FeOOH-nr ratio is 10, although it was 2.00 µg cm–2 when only FeOOH-nr was used. M Fe is correlated with the OER activity. The highest OER activity was obtained at Co-ns/FeOOH-nr = 10.The assembled structure of FeOOH-nr and Co-ns in the deposited catalyst layer was observed by TEM (Fig. 3). A rod-like FeOOH-nr was surrounded by sheet-like Co-ns. Thus, it was suggested that Co-ns was assembled with FeOOH-nr by the electrostatic interactions.The results of ADT with the composite catalyst dispersed in the electrolyte for self-repairing (Fig. 4) shows that there was little degradation after 2000 cycles of start-up and shut-down. Therefore, these composite catalysts have excellent stability. However, when no composite catalyst was dispersed in the electrolyte, meaning that no self-repairing occurred, η 100 gradually increased in the 2000 cycles. The degradation behavior was milder than that of the FeOOH-nr only; thus, the composite catalyst exhibited the improved stability of the FeOOH-based catalyst layer.In conclusion, the deposited amount of FeOOH-nr was successfully increased by the addition of Co-ns in the electrolyte to form composite catalysts. The electrostatic self-assembly is useful to combine the properties of different catalysts for a self-repairing system. ACKNOWLEDGEMENT A part of this study was supported by KAKENHI (Grant-in-Aid for Scientific Research 20H02821) from Japan Society for the Promotion of Science (JSPS). REFERENCE [1] Y. Uchino et al., Electrocatalysis 9, 67 (2018).[2] Y. Kuroda et al., Electrochim. Acta. 323, 1348122 (2019).[3] Y. Kuroda et al., J. Sol-Gel Sci. Technol., 104, 647-658 (2022).[4] A. Haleem et al., Electrochemistry. 89(2), 186 (2021). Figure 1

Catalyst Application in Three-Dimensional Porous Electrodes for Alkaline Electrolysis

Hydrogen is critical in the green transition, and a key system for producing green hydrogen is through alkaline electrolysis. Although the alkaline electrolyzers are mature and commercially available, vast improvements are still expected in the future 1.Traditional and most commercially applied alkaline electrolyzer electrodes are made from massive nickel plates (or nickel-plated steel plates) with some scattered perforation. With the ongoing development of thin alkaline ion‐conducting membranes with low internal resistance, the benefit of three‐dimensional porous electrodes becomes obvious. With such electrodes, there will be no blind spots and the active catalytic area can be increased significantly. Today, most groups developing such 3D electrodes use commercial nickel foam as substrate. This limits the options to what is available in the market, moreover the purchase cost is high.The present work aims at developing high‐performing three‐dimensional hydrogen and oxygen evolution electrodes for alkaline electrolysis. The focus will be on the application of nanostructured electrocatalysts into three‐dimensional electrode structures, similar to nickel foams.The results obtained, so far, show homogeneous formation of nanoparticles on the surface. The analysed samples show mechanical flexibility as soon as the particles are deposited but samples become rigid after testing in a half cell setup with KOH 1 M electrolyte. Further analysis will explore changes to the microstructure. The roughness factor calculated by non-faradaic cyclic voltammetry is in the range of 75 cm2 ECSA / cm2geometric, showing higher value than the commercial Nickel foam.Initial experiments are carried out on as-prepared samples, but more advanced catalysts are also explored based on state-of-the-art materials. [1] IRENA - Green Hydrogen Cost Reduction: Scaling up Electrolysers to Meet the 1.5 °C Climate Goal, International Renewable Energy Agency, Abu Dhabi (2020)

Preparation and mechanism of Cu-GO laminated composite films with high thermal conductivity by intermediate nickel and silver layers via electrodeposition and ultrasonic spraying method

The graphene oxide-Cu (GO-Cu) laminated composite films with nickel and silver intermediate layers were prepared by electrodeposition, ultrasonic spraying and subsequent annealing heat treatment. The influences of current density of Cu plating, the silver ion concentration and electrodeposition time of nickel plating on the morphology, microstructure and thermal conductivity of the composites were systematically studied. The introduction of Cu-O-C covalent bonds and the diffused nickel and silver transition layers at the interface could effectively enhance the interfacial bonding between GO and Cu, accordingly improving its thermal conductivity. Under the optimal process parameters (current density 8 A/dm2, silver ion concentration 4.25 g/L(0.025 M), electrodeposited nickel 25 s), the in-plane thermal conductivity of GO-Cu-GO and GO-Ag-Cu-Ag-GO and GO-Ni-Cu-Ni-GO laminated composite films could reach 572.21 W·m−1·K−1, 652.64 W·m−1·K−1 and 790.36 W·m−1·K−1, respectively. The significant enhancement of thermal performance for the Cu-GO laminated composite films could be attributed to the effective improvement of the interfacial bonding between Cu and GO in the composites by existence of intermediate metal layer.

Peak hardness stability analysis of Al7075 alloy dispersed with Ni coated duralumin powder during natural aging phenomena

This technical paper presents the successful reinforcement of nickel (Ni) coated duralumin powder in an Al7075 matrix using the liquid stir casting technique and property stability obtained by heat treatment. Ni coating is performed by electroless nickel plating technique where 8 μm coating thickness was observed to be the minimum required to prevent dissolution of the reinforcements (duralumin powder) in the matrix (Al7075). During stir casting it was observed to uniformly disperse the coated duralumin powder up to 7 wt.%. Al7075 alloy and composites were artificially aged with solution heat treatment (SHT) performed at 450 °C for 4 h, water quenched and then aged at 120, 150 and 180 °C. Al7075 alloy and composites were naturally aged for 24 weeks in atmospheric temperature after peak aging. Composites aged at 120 °C exhibited superior results and considered as optimum aging temperature compared to those aged at 150 and 180 °C. Peak hardness values in 7075-7Dp+8T composite improved by 108% and 7075-7Dp+10T composite improved by 110% when compared to peak aged (at 120 °C) Al7075 alloy. Moreover, composites with coated reinforcement displayed a higher resistance to natural aging, with reductions of 53.5 and 54.4% in natural aging tendency compared to the naturally aged Al7075 alloy for 7075-7Dp+8T and 7075-7Dp+10T composites respectively. However, an increase in Ni coating thickness beyond the optimal 8 μm did not significantly improve as cast and peak hardness or natural aging resistance. XRD analysis confirmed that there is presence of CuAl2, CuAl2Mg, Mg2Si, and MgZn2 phases in peak-aged (120 °C) 7075-7Dp+8T sample. Considering the limited impact on property enhancement and the financial burden associated with thicker coatings, a coating thickness of 8 μm is recommended as compared to 10 μm.

Design Optimization and Mechanical Properties of SiC Particle Reinforced Ti-Based Metallic Glass Matrix Composite.

Ti-based bulk metallic glass (BMG) alloys have attracted widespread attention due to their strong glass forming ability, high specific strength, and good corrosion resistance. However, the poor plasticity of BMGs limits their further application in the aerospace and aircraft fields, as well as others. We optimized the composition of SiC-reinforced, Ti-based metallic glass matrix composites (MGMCs) through finite element modeling (FEM). FEM of MGMCs containing irregularly shaped SiC particles with different contents was conducted. Stress and strain analyses were conducted to evaluate the effect of the particle volume fraction on the mechanical behavior of MGMCs, and an optimization value of 30% was obtained, which is conducive to plasticity improvement. Arc melting copper mold injection casting was used to verify the optimized SiC content. The results show that the electroless nickel plating treatment effectively improves the wettability between SiC particles and the amorphous matrix, enabling the successful preparation of SiC/MGMC with a volume fraction of 29.5% through traditional injection casting. The volume fraction of SiC plays a crucial role in the transition of fracture mode from splitting to shear in MGMCs. After adding lightweight SiC particles, the yield strength, plasticity, modulus, and specific strength were improved by 25%, 1471%, 46%, and 33%, indicating that the use of nickel-plated SiC particles in MGMCs is an effective strengthening and toughening method for BMGs.

Effect of humidity on radiolysis-enhanced corrosion by gamma irradiation on electroless nickel plating

The study reveals that water vapor can cause corrosion of electroless nickel plating under gamma irradiation, even in the absence of dew condensation. To control relative humidity during gamma irradiation, a simple apparatus utilizing saturated salt solutions was developed and validated by cold tests. Irradiation testing of electroless nickel plating was conducted under humidity control at relative humidity of 20%, resulting in surface degradation after 1 MGy total dose. Conversely, no degradation was observed on samples exposed to dry condition with relative humidity of less than 10% after a 5 MGy total dose. Humidity-uncontrolled irradiation tests, where condensation could occur, resulted in more severe corrosion than the humidity-controlled tests. A comparison of the chemical composition of corrosion products between the humidity-controlled and humidity-uncontrolled environments showed nitrate corrosion products were prevalent in the former while hydroxides were dominant in the latter.

Electrochemical properties of electroless Ni plated super duplex stainless in 3.5% NaCl solution

Si wafers used in semiconductors require precise machining; therefore, they are processed using an STS304 saw wire, which is made of an austenitic stainless steel with excellent strength and corrosion resistance. However, the recently developed super duplex stainless steel (SDSS) exhibits superior performance compared to STS304 and is suitable for use as a saw wire. SDSS is a stainless steel composed of austenite and ferrite, with the ratio varying depending on the temperature during heat-treatment. Ferrite has better wear resistance than austenite; therefore, Ni plating was applied to ferritized SDSSs to improve the saw wire performance, and the electrochemical properties were analyzed. The nickel layer increased with time, forming a non-uniform coating until 180 s, followed by uniform plating. This was confirmed by the changes in the surface roughness and surface images. With the formation of a uniform nickel-plating layer, the distinction between austenite and ferrite became visible, resulting in decreased surface roughness. When the time exceeded 240 s, the difference in roughness increased owing to the difference between in the reactivities of austenite and ferrite. This difference in the surface roughness influenced the electrochemical behavior. The uneven nickel-plating layer exhibited a potential change of over 200 mV during the initial open-circuit potential (OCP) stage (prior to 800 s). In a potentiodynamic polarization test, plating for more than 300 s resulted in a reduced corrosion resistance owing to overplating. Increasing the thickness of the Ni layer altered the electrochemical behavior from SDSS to nickel. By analyzing the surface conditions and electrochemical properties, a uniform nickel-plating layer, exhibiting the characteristics of SDSS, was observed at 240 s. Therefore, the optimal duration for electrolytic nickel plating of ferritized SDSS was 240 s

Effects of modification of hBN by nickel plating on coating structure and properties of supersonic plasma spraying NiCr-Cr3C2-hBN@Ni coatings

Hexagonal boron nitride (hBN) with excellent self-lubrication performance is expected to relieve the friction resistance and wear of NiCr–Cr3C2 coatings. However, the poor wettability of hBN with most materials makes it difficult to fabricate NiCr–Cr3C2-hBN composite coating with good cohesion strength. In this study, hBN was firstly pretreated through magnetron-sputtering aided Ni plating to form hBN@Ni particles. Then, NiCr–Cr3C2-hBN@Ni powder was prepared by spray granulation. Next, corresponding coatings were prepared through supersonic atmosphere plasma spraying. It was found that in comparison with NiCr–Cr3C2-hBN coating, the NiCr–Cr3C2-hBN@Ni coating exhibited a decreased porosity (from 3.6% to 0.3%), elevated cohesion (from 52.78 N to 62.11 N), and the wear rate decreased by an order of magnitude. It was concluded that hBN@Ni can effectively improve the component interface inside powder, enhance the cohesion of molten in-flight particles, and make the internal structure of the coating denser.

DEVELOPMENT OF RECYCLING TECHNOLOGY FOR SPENT CHEMICAL NICKEL PLATING SOLUTION

Currently, the chemical nickel plating process is one of the most popular electroplating methods compared to others due to a number of advantages. However, the production process generates a significant amount of spent chemical nickel plating solutions, which poses a threat of environmental pollution. To solve this problem, the possibility of regenerating the spent solution of chemical nickel plating from one of the industrial enterprises of Udmurtia by the reagent method was studied. Sodium carbonate was chosen as the precipitant for nickel ions, the amount of which was determined from potentiometric titration curves; the most complete precipitation of nickel ions occurs at pH 10. It has been established by IR spectroscopy that nickel hydroxide salts are formed as a result of the interaction of the spent electrolyte with the precipitant. The results of thermogravimetric and differential thermal analysis of the precipitate showed three endothermic effects: at temperatures up to 100 °C, it corresponds to dehydration; at 280±10 °C - to the removal of a part of chemisorbed water and carbonates; at 420 °C - to the final removal of water. As a result of heat treatment of the hydroxocarbonate precipitate, a black fine powder of nickel(II) oxide is obtained, the IR spectrum of which has a set of bands characteristic of this compound. Two variants of the technological scheme for the regeneration of spent electrolytes for the preparation of initial working solutions for chemical nickel plating from nickel(II) hydroxocarbonate and nickel oxide are proposed. The quality of the obtained solutions was checked by applying a nickel coating on brass products. The thickness of the coating was measured by scanning electron microscopy. It has been established that the highest quality coating is obtained using an electrolyte prepared from nickel hydroxocarbonate.

4-ATP-modified CNTs@NiO–Fe2O3–Ag SERS filter membrane for rapid in-situ detection of furfural in mineral oil

Evaluating the transformer aging state and detecting multi-aging characteristics in transformer oil with high sensitivity and fast speed has become a key challenge. This study introduces a P–N heterojunction (CNTs@NiO-α-Fe2O3) fabricated through electroless nickel plating and a one-step hydrothermal method. Additionally, silver nanoparticles (AgNPs) with adjustable particle sizes are grown on the surface using a chemical reduction method. To obtain high sensitivity and rapid SERS signal, CNTs@NiO-α-Fe2O3–Ag gel is adsorbed on a disposable needle filter (220 nm) surface, and 4-aminothiophene (4-ATP) is grafted onto the surface of SERS substrate. The minimum detection limit was 0.025 mg/L (EF = 5.22 × 104), and the response time of SERS best signal could be shortened to 3 min. Density functional theory (DFT) calculations reveal that by constructing a P–N heterostructure of NiO–Fe2O3 and assessing the adsorption energies of furfural, acetone, and methanol on the surface of the P–N heterojunction. This SERS strategy has a huge application prospect in the aging diagnosis of oil-paper insulation systems in a transformer.

Investigating the Potential of Electroless Nickel Plating for Fabricating Ultra-Porous Metal-Based Lattice Structures Using PolyHIPE Templates.

The use of polymerized high internal phase emulsions (polyHIPEs) as templates for electroless nickel plating is a promising method for producing ultra-porous metallic lattice structures with consistent wall thickness. These structures have desirable properties such as low density, high specific strength, resilience, and absorbency, making them suitable for various applications including battery electrodes, catalyst supports, and acoustic or vibration damping. This study aimed to optimize and investigate the electroless nickel plating process on polyHIPEs. Initially, a surfactant (Hypermer)-stabilized water-in-oil emulsion based on 2-ethylhexyl-acrylate and isobornyl-acrylate was used as a 3D printing resin to create polyHIPE structures. Then, the electroless nickel plating process was optimized using polyHIPE discs. The study also examined the effects of air, argon, and reducing atmospheres during the heating process to remove the polyHIPE template using metallized 3D-printed polyHIPE lattice structures. The findings indicated that different atmospheres led to the formation of distinct compounds. While nickel-coated polyHIPEs were fully oxidized in an air atmosphere, nickel phosphide (Ni3P) structures occurred in argon and reducing atmospheres along Ni metal. Moreover, in argon and reducing atmospheres, the porous structure of the polyHIPEs was retained as the internal structure was completely carbonized. Overall, the study demonstrated that intricate polyHIPE structures can be used as templates to create ultra-porous metal-based lattices for a wide range of applications.

Injection Molding of Encapsulated Diffractive Optical Elements.

Microstructuring techniques, such as laser direct writing, enable the integration of microstructures into conventional polymer lens systems and may be used to generate advanced functionality. Hybrid polymer lenses combining multiple functions such as diffraction and refraction in a single component become possible. In this paper, a process chain to enable encapsulated and aligned optical systems with advanced functionality in a cost-efficient way is presented. Within a surface diameter of 30 mm, diffractive optical microstructures are integrated in an optical system based on two conventional polymer lenses. To ensure precise alignment between the lens surfaces and the microstructure, resist-coated ultra-precision-turned brass substrates are structured via laser direct writing, and the resulting master structures with a height of less than 0.002 mm are replicated into metallic nickel plates via electroforming. The functionality of the lens system is demonstrated through the production of a zero refractive element. This approach provides a cost-efficient and highly accurate method for producing complicated optical systems with integrated alignment and advanced functionality.

Efficient Electromagnetic Interference Shielding of PPA6@NiM/PDMS Composites with Porous and Asymmetric Gradient Structures

In this work, magnetic PA6 microspheres (PPA6@NiM) with porous structures were prepared using the solvent co-precipitation method and electroless nickel plating technology, and the stacked magnetic microspheres were encapsulated with polydimethylsiloxane (PDMS) to obtain PPA6@NiM/PDMS composites. The existence of the porous structure increases the attenuation path of the electromagnetic wave, and the presence of the nickel layer improves the magnetic loss of the composite material to the electromagnetic wave and synergistically improves the absorption of the electromagnetic wave. Among them, the total shielding effectiveness (SET) of the PPA6@NiM4/PDMS composite is as high as 39.9 dB, and the reflection coefficient (R) is 0.83. To further increase the absorption effect of the composite material, an asymmetric gradient structure was constructed by utilizing the difference in electrical conductivity between the magnetic microspheres. The electromagnetic wave is incident from the surface with lower conductivity (impedance matching layer). It is reflected by the consistency with higher conductivity (strong reflective layer) than the bottom layer to increase the loss of electromagnetic waves inside the material. The composite SET constructed with M1 and M4 particles with the most significant difference in conductivity achieved 35.5 dB with an absorption coefficient (A) of 0.42. It shows that the porous combined asymmetric gradient structure we designed can effectively improve the shielding efficiency and absorption capacity of the composite material against electromagnetic microwaves and serve as a reference for creating high-absorbing and high-performance electromagnetic shielding materials.

Investigation on the effect of nickel and nickel-chromium alloy pulse current plating on copper substrate

ABSTRACT In the present study, nanocrystalline nickel (Ni) and nickel-chromium (Ni-Cr) alloy coatings were developed on copper (Cu) substrate using pulse current. The pulse current parameters include a cycle time of 240 milliseconds at a duty cycle of 0.5 and 4.17 Hz frequency. The surface morphology, texture, hardness, scratch resistance and porosity were investigated for different coatings developed by pulse plating. Energy Dispersive Spectroscopy (EDS) analysis revealed good quality Ni and Ni-Cr alloy coatings developed on the copper substrate. The peak current of the pulse has been observed to have an impact on the coating weight and thickness. The micrographs of the coatings explored under Field Emission Scanning Electron Microscopy (FESEM), depict uniform coatings consisting of fine primary and coarse secondary granules of Ni and Cr. The hard primary and secondary Ni granules deposited on the surface of Cu increase its hardness, corrosion and wear resistance. Further, it was observed that the Ni-Cr alloy plated samples are harder and less porous in nature compared to Ni plated samples.

Development and Mechanical Characterization of Ni-Cr Alloy Foam Using Ultrasonic-Assisted Electroplating Coating Technique

Metal foams and alloy foams are a novel class of engineering materials and have numerous applications because of their properties such as high energy absorption, light weight and high compressive strength. In the present study, the methodology adopted to develop a Ni-Cr alloy foam is discussed. Polyurethane (PU) foam of 40PPI (parts per inch) pore density was used as the precursor and coating techniques such as electroless nickel plating (ELN), ultrasonic-assisted electroplating of nickel (UAEPN), and pack cementation or chromizing were used to develop the Ni-Cr alloy foam. The surface morphology, strut thickness and minimum weight gain after each coating stage were evaluated. It was observed from the results that the adopted coating techniques did not damage the original ligament cross-section of the PU precursor. The minimum weight gain and the coating thickness after the UAEPN process were observed to be 42 g and 40–60 μm, respectively. The properties such as porosity percentage, permeability and compressive strength were evaluated. Finally, the pressure drop through the developed foam was estimated and verified to determine whether the developed foam can be used for filtering applications.

Multifunctional Biosensing Platform Based on Nickel-Modified Laser-Induced Graphene.

Nickel plating electrolytes prepared by using a simple salt solution can achieve nickel plating on laser-induced graphene (LIG) electrodes, which greatly enhances the electrical conductivity, electrochemical properties, wear resistance, and corrosion resistance of LIG. This makes the LIG-Ni electrodes well suited for electrophysiological, strain, and electrochemical sensing applications. The investigation of the mechanical properties of the LIG-Ni sensor and the monitoring of pulse, respiration, and swallowing confirmed that the sensor can sense insignificant deformations to relatively large conformal strains of skin. Modulation of the nickel-plating process of LIG-Ni, followed by chemical modification, may allow for the introduction of glucose redox catalyst Ni2Fe(CN)6 with interestingly strong catalytic effects, which gives LIG-Ni impressive glucose-sensing properties. Additionally, the chemical modification of LIG-Ni for pH and Na+ monitoring also confirmed its strong electrochemical monitoring potential, which demonstrates application prospects in the development of multiple electrochemical sensors for sweat parameters. A more uniform LIG-Ni multi-physiological sensor preparation process provides a prerequisite for the construction of an integrated multi-physiological sensor system. The sensor was validated to have continuous monitoring performance, and its preparation process is expected to form a system for non-invasive physiological parameter signal monitoring, thus contributing to motion monitoring, disease prevention, and disease diagnosis.

The use of Preston equation to determine material removal during lap-grinding with electroplated CBN tools

Grinding executed in a lapping configuration is an alternative finishing process benefiting from both grinding and free-abrasive machining, while minimizing the heat effect impact. Electroplated tools can be effectively used in different abrasive processes, including high-speed grinding, however, the assessment of machining performance over time is a key factor in their correct use to achieve satisfactory technological results. In conventional grinding, bigger grain-coverage provides better results due to the higher bonding strength of grains. In lap-grinding, fracturing and crushing of the abrasive particles initially covered by the plating result in a suspension which is typically dosed continuously in free-abrasive machining. Due to this, the process transforms from two-body (grinding) to three-body abrasion (free abrasive machining) which may result in reduced grinding performance approaching asymptotically a specific value while improving surface finish. The main aim of the presented study is the evaluation of electroplated CBN tools used in lap-grinding of 40H alloy steel workpieces whose hardness was 54 HRC. The obtained results and observations of the working surface of CBN wheels and workpieces allowed for the identification of the wear characteristics for three nickel plating thicknesses corresponding to 35%, 50% and 65% of the nominal CBN crystal size and for specific process parameters. The surface roughness Ra parameter decreased gradually from the initial value 1.9 μm to the values below 0.7 μm for bigger B107 grains and for all plating thicknesses. For smaller B64 grains, the surface roughness and waviness parameters reached similar values to those obtained for the larger B107 grains at corresponding processing times. The lowest value of Ra parameter below 0.4 μm was obtained for B64 grains and for the thinnest plating but with a 50% reduction in material removal comparing to B107 grains. The Preston equation was employed to calculate the material removal as a function of time under variable process conditions in the machining zone due to the tool wear. This attempt extended the range of the material removal modeling, despite the fact that the electroplated wheels were subject to wearing down resulting in the gradual reduction in the efficiency, as well as in the change of the working conditions in the workpiece-tool contact zone.

Approaches to Enhancing Cathodic Nickel Recovery from Ni-EDTA Containing Synthetic Wastewaters

Ethylenediaminetetraacetic acid (EDTA) is widely employed as a chelating agent in the electroless nickel plating industry to form stable metal–organic complexes (e.g., Ni-EDTA). These metal–organic complexes cannot be removed from plating wastewaters by traditional treatments in a cost-effective way. While electrochemical advanced oxidation processes (EAOPs) have been utilized for the efficient degradation of Ni-EDTA at the anode, challenges remain in the simultaneous and effective recovery of nickel at the cathode. In this study, we investigate the efficacy of five cathode materials [i.e., carbon felt (CF), titanium plate, graphite plate (GP), copper plate, and stainless-steel plate] with respect to Ni recovery. The highest Ni removal efficiency of 81.6 ± 0.1% was achieved with the carbon felt cathode which was 30% higher than that of the titanium cathode (52.1 ± 1.4%) with the improvement in performance attributed to the higher rate of mass transport of Ni ions (CF: 4.3 ± 0.4 × 10–4 s–1 vs Ti: 1.8 ± 0.2 × 10–4 s–1) toward the nanowire structure of carbon felt and to the large surface area of the carbon felt cathode compared with the other cathodes. While the chemical composition of the deposits was independent of the cathodic material or structure, the morphology of deposition varied with the cathode material. The accumulated Ni on the carbon felt surface was successfully recovered either as a nickel salt solution by acid leaching or as high purity NiO by calcinating the Ni-loaded carbon felt cathode at over 800 °C. The performance of the regenerated carbon felt after acid leaching was comparable to that of the fresh cathode even after 10 cycles of use and regeneration via acid leaching with this result confirming the stability and reusability of the carbon felt material.

Anchoring Monodispersed NiSe@Ni Particles on Graphene for Energy Storage in Supercapacitors

In this study, monodispersed NiSe@Ni particles were successfully anchored on graphene sheets by electroless nickel plating combined with a chemical-vapor-reaction process, in which the nickel particles were first deposited onto graphene sheets and subsequently transformed in situ into NiSe@Ni at an elevated temperature. The obtained product showed a unique multi-dimensional coupling structure, namely, monodispersed NiSe@Ni particles (0 D) anchored on graphene sheets (2 D), which enabled maximum synergy on the specific surface area, conductivity, and the electrochemical activity of NiSe, Ni, and graphene multi-phases. The NiSe@Ni/graphene composite showed a specific capacity of 302 mAh g−1 at a current density of 1 A g−1 in a potassium-hydroxide-electrolyte solution. Meanwhile, the hybrid supercapacitor of NiSe@Ni/graphene//AC exhibited a high energy density of 68.0 Wh kg−1 at 803.0 W kg−1 and maintained 72.53% of the initial capacity after 10,000 cycles at a current density of 10 A g−1.

ФТОРСОДЕРЖАЩИЕ СОЕДИНЕНИЯ В ПРOЦЕССЕ ЭЛЕКТРOХИМИЧЕСКOГO НИКЕЛИРOВАНИЯ

The influence of various compounds on the process of electrochemical nickel plating is considered. It is shown that organoelement compounds can be used as additives in nickel plating electrolytes. It is proposed to investigate fluorine-containing compounds as leveling and gloss-forming additives in the process of electrochemical nickel plating