Nanocrystalline Nickel Coatings Research Articles

Ultrasonic-assisted pulse electrodeposition process for producing nanocrystalline nickel films and their corrosion behavior: Competition between mass transport and nucleation

Ultrasonic-assisted pulse electrodeposition of nanocrystalline nickel (NC-Ni) coatings from Watts bath on copper substrate was investigated. Direct (DC), pulsed (PC), and pulse reversed (PRC) current electrodeposition techniques were employed to electrodeposit NC-Ni coatings in the absence and presence of ultrasound wave with a nominal power ranging from 95 W to 200 W and their surface morphology, hardness, and crystalline microstructure were compared. We observed that as the ultrasound power increases, the cathodic efficiency and the microhardness increase, whereas the crystallite size and surface roughness decrease for NC-Ni electrodeposited by the three techniques in the same way. However, the effect of pulse waveform is dominant. The finest crystallite size (24 nm) and highest hardness (585 HV) were achieved for NC Ni coatings PC electrodeposited using an ultrasound with 200 W nominal power. It is believed that the coating produced by PC and PRC techniques develops a preferential orientation in (111) and (100) planes, respectively. The application of ultrasound wave and increasing its nominal power changes the preferential orientation of all obtained coatings to (111) planes. The corrosion behavior of NC Ni coatings, as investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in NaOH solution, demonstrates the effect of nanocrystalline on the passivation and corrosion resistance of NC-Ni coatings.

Comparing brightness of nanocrystalline nickel coating with traditional bright nickel coating and investigation of stereochemistry of brightener molecules

ABSTRACT Nanocrystalline nickel coatings can be electrodeposited by using grain refiners like saccharin which consequently increase the gloss of the coating. Also, brighteners can produce bright coatings. The aim of this research was to compare the brightness of electroplated nanocrystalline nickel coating with traditional electroplated bright nickel coating. The coatings prepared from the bath containing saccharin and a bath with para-toluene sulphonamide had virtually the same gloss. Thus, instead of expensive brightening agents, saccharin can be used to achieve the same gloss in nickel plating. To investigate the stereochemistry of brightener molecules, the density functional theory (DFT) method was used at the computational level of B3LYP with the basis set 6-311G (d,p) ++ in a Gaussian software. The results of computational chemistry showed that the most probable state of adsorption of brightening additives is when the aromatic ring or a double bond or a triple bond of the brightener molecule approaches the cathode surface during the adsorption process.

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.

Effect of Annealing on Surface Morphology and Structure of Nickel Coatings Deposited from Deep Eutectic Solvents

Nanocrystalline nickel coatings deposited on a copper base material from DES made of choline chloride and ethylene glycol in 1:2 molar ratio containing 1 mol dm−3 NiCl2⋅6H2O were modified through post-deposition heat treatment at the temperatures from 100 to 400 °C. As-deposited coatings were composed of spheroidal agglomerates with the size of several hundred nanometers interspersed with lamellar crystals, but after annealing at 300 °C and 400 °C only single nano-sized plates embedded in a granular and porous layer remained. As the temperature of the heat treatment increased from 100 °C to 400 °C, the mean crystallite size increased from 13 to 35 nm. The change in crystallite size was accompanied by a change in microhardness, the maximum value of which was measured for the annealed coating at 200 °C. As a result of heat treatment, coatings were gradually covered by a layer of oxidized nickel species. XPS analyses showed that NiOOH and Ni(OH)2 dominated among them. Above 200 °C the share of these compounds began to decline in the face of the increasing share of NiO. This, in turn, clearly translated into a deterioration of the corrosion resistance of Ni coatings annealed at 300 °C, and especially at 400 °C, during exposure in 0.05 mol dm−3 NaCl solution.

Texture orientation, morphology and performance of nanocrystalline nickel coatings electrodeposited from a Watts-type bath: Effects of H3BO3 concentration and plating time

Nanocrystalline nickel coatings were electroplated from a Watts-type bath with the addition of H3BO3 ranging of 5–25 g·L−1. In order to study the evolution of preferential orientation of Ni electrodeposits, the microstructure, texture and grain size of the coatings deposited with different H3BO3 contents for different plating times were characterized by optical microscopy, scanning electron microscopy and X-ray diffraction, further the residual stress, microhardness, and abrasion resistance of the texture-oriented coatings were measured by X-ray diffraction, Vickers microhardness tester, and Calotester, respectively. The electrochemical corrosion resistance of the highly texture-oriented coatings and the substrate was evaluated by polarization and electrochemical impedance spectroscopy. The results show the preferential orientation of the coating was gradually changed from (200) to (220) crystal plane with increasing H3BO3 content after plating time of 1 h. The longer the plating time was applied, the higher the degree of Ni (200) orientation was produced at a low H3BO3 concentration of 5 g·L−1. The preferential orientation of the coatings at a high H3BO3 concentration of 25 g·L−1 was changed initially from (111) + (200) to (200) plane, then random orientation, and evolved to (220) plane after plating time of more than 20 min. The stability of various textures of Ni electrodeposits against plating time-H3BO3 concentration was established, and at the same time the microstructure-property relationship was developed. The average grain size of nickel coating was about 50–65 nm. The average residual stresses of the coatings with (200), (200) + (220) and (220) orientations were −64.3 ± 5 MPa, −477.2 ± 57 MPa and −618.0 ± 36 MPa, respectively. The microhardness of the coating increased gradually from 242.52 ± 10HV1 to 269.46 ± 12HV1 with increasing H3BO3 content because of the inverse Hall-Petch and grain orientation. The abrasion and corrosion resistances of (200)-oriented coatings were better than those of (220)-oriented coatings.

Direct Correlations among the Grain Size, Texture, and Indentation Behavior of Nanocrystalline Nickel Coatings

By using nc-Ni coatings as a model system, systematic experiments were designed to evaluate the interaction between the microstructural and mechanical properties tailored by electrodeposition conditions. A direct correlation between grain size and texture was established for the first time. The grain size of the (111) crystalline plane decreases with the texture coefficient (RTC) regardless of the process conditions, and that of the (220) plane has different trends. Then, a peculiar phenomenon is revealed that the dependence of hardness on grain size is accurately described by the Hall-Petch relationship when changing the temperature or pH, but with different slopes, while it deviates from such a relationship with changing current density, denoting more underlying mechanisms related to texture. Finally, a surprising degree of influence of texture on hardness and elastic modulus is also presented, with the overall trend of hardness increasing with texture; and when the RTC of (111) exceeds 40%, the elastic modulus increases with texture, implying a fundamental relationship between modulus and texture. Texture predominates over the other factors on the elastic modulus, revealing the importance of elastic anisotropy. Significantly, the present work suggests a useful tailoring routine to fabricate high quality nc-Ni coatings with the desired structure and mechanical properties.

A new model for predicting the grain size of electrodeposited nanocrystalline nickel coatings containing sulphur, phosphorus or boron based on typical systems

Controlling the grain size in electrodeposited coatings for the prevention of corrosion is highly important. To understand the relationship with grain size and electrochemical performance many experiments need to be undertaken to vary the grain size of the deposit. In the present work the (crystallite) grain size of electrodeposited Ni coatings formed in the presence of metalloids such as boron (B), sulphur (S) and phosphorus (P) was estimated from analysing mass transfer at the cathode-electrolyte interface. A mathematical model has been proposed which indicates that the grain size of the deposit is directly proportional to current efficiency and the deposition rate while being inversely proportional to the current density and metalloid (B, S, P) content in the coatings. A simple relationship is developed which is in agreement with experimental data and data that is reported in the literature. The development of such a model should significantly decrease the amount of experimentation required to achieve the desired grain size in such systems (Ni-B, Ni-S, Ni-P coatings) obtained by electrodeposition.

Jet electrodeposition with movable, flexible friction on quality of nanocrystalline nickel coatings

ABSTRACTTo improve the deposition rate and quality of nanocrystalline nickel coatings, a method involving movable, flexible friction, jet electrodeposition (MFFJE) was proposed in this paper. The effects of cathode scanning speed and current density on electrodeposited nickel coatings prepared by MFFJE were investigated. Compared with traditional jet electrodeposition, the results showed that MFFJE exerted remarkable effects, improving the deposition rate and quality of nickel coatings, and, when the cathode scanning speed was 1000 mm min−1, the coating surface morphology was best. The maximum processing current density of nickel plating was more than 250 A dm−2. The grain size was decreased to 11.7 nm, hardness increased to 546 HV, and coating corrosion resistance significantly improved.

Solid Particle Erosion of Nanocrystalline Nickel Coatings: Influence of Grain Size and Adiabatic Shear Bands

The primary objective of the present study is to investigate the influence of nanocrystalline grain size on the solid particle erosion behavior of nickel. For the above purpose, 450-μm-thick nanocrystalline Ni coatings having the average grain sizes of 21, 42, 70, and 195 nm were obtained using pulsed electrodeposition (PED). All these samples along with bulk annealed Ni samples (43 μm grain size) were subjected to solid particle erosion using SiO2 particles as an erodent at a constant impact velocity of 45 m/s and two impact angles (30 and 90 deg). Erosion results indicate that bulk Ni and PED Ni coatings of grain sizes 195 and 70 nm exhibit the same erosion rate, while PED Ni coatings of 42 and 21 nm grain size exhibit marginally higher erosion rates with a clear trend of increasing erosion rate with decreasing grain size. It was also observed that the higher erosion rates exhibited by 21- and 42-nm-grain size PED Ni samples were associated with the formation of adiabatic shear bands (ASBs) originating from the eroded surface and propagating into the eroded sample. The experimental observations have been understood on the basis of a transition from a localization model for erosion for coarse-grained Ni (> 70 nm) to an ASB-induced erosion model for grain sizes less than 70 nm.

Electrodeposition of Nanocrystalline Nickel Coatings from a Deep Eutectic Solvent with Water Addition

The electrodeposition of nanocrystalline Ni coatings from electroplating baths containing deep eutectic solvents (analogues of room-temperature ionic liquids) is studied. To improve physicochemical properties of electrolytes and enhance mechanical properties and corrosion resistance of Ni films, we suggest introducing extra water into plating baths based on a deep eutectic solvent. The effect of water addition on the electrodeposition of nickel coatings is investigated using an electrolyte containing choline chloride, ethylene glycol, nickel chloride and water in the molar ratio of 1: 2: 1: x where x is equal to 6, 9, 12, 15 or 18 (i.e., Ethaline + NiCl2 + xH2O). The introduction of water into the liquid mixture results in an increase in conductivity and a decrease in viscosity. The addition of extra water leads to more uniform and finer grained deposits. The electrodeposited Ni coatings with an average crystallite size of about 5 to 7 nm have an fcc crystal nanostructure. An increase in water content in the plating bath results in an increase in the microhardness of deposits and the inverse Hall–Petch effect is observed. According to electrochemical impedance spectroscopy measurements, the coatings with higher corrosion resistance are deposited from Ni plating bath containing water addition.

The Effect of Stirring Rate on Electrodeposition of Nanocrystalline Nickel Coatings and their Corrosion Behaviors and Mechanical Characteristics

The Effect of Stirring Rate on Electrodeposition of Nanocrystalline Nickel Coatings and their Corrosion Behaviors and Mechanical Characteristics

The role of functional groups of saccharin in electrodeposition of nanocrystalline nickel

Nanostructural materials exhibit different mechanical, physical, chemical, and electrochemical properties relative to conventional structures. For instance, nanostructural nickel shows enhanced properties compared to those of polycrystalline nickel, such as higher microhardness, increased wear resistance, higher brightness and lower roughness. In order to produce nanostructural materials, some additives are used as grain refiners. Saccharin is one of the additives that is usually added to the Watts bath in the electroplating process as a grain refiner. The aim of this study is to clarify the functional mechanism of saccharin as a grain refiner in order to realize which functional group of this molecule works as a grain refiner and causes enhancement of properties. To investigate the impact of a functional group of saccharin in the production of nanocrystalline nickel deposits, three different materials with the same functional groups as saccharin were chosen: benzene sulfonic acid, methyl sulfonamide, and benzothiazole. In the process of nickel electroplating these materials were added to the Watts bath as additives. The X-ray diffraction patterns were used to determine the average grain size of the nanocrystalline nickel coatings. The results indicate that the presence of a benzene ring in saccharin, benzene sulfonic acid and benzothiazole cause these molecules to move from the electrolyte to the electrode surface and, by blocking the electrode surface, enhance the grain size and produce nickel coatings with an average grain size below 50 nm. The results also showed that the presence of materials containing a benzene ring with a weak ionic group enhances adsorption on the electrode surface.

Synthesis and Thermal Stability of Nanocrystalline Nickel Coatings by Direct Current Electrodeposition

Abstract The influences of current density and saccharin concentration on nanocrystalline nickel coatings synthesized by direct current electrodeposition were analyzed. Results show that in the current density range from 0.5 A/dm2 to 1.5 A/dm2, nanocrystalline nickel coatings with broad microhardness HV distribution from 4150 MPa to 6030 MPa can be synthesized by adjusting saccharin concentration. The preferred orientation in the deposits exists at 0.5 A/dm2, (111), (200) double orientation texture changes to a (200) orientation texture as saccharin concentration and (200) intensity increase. The internal stresses of the samples prepared at 0.5 A/dm2 decrease to nearly 0 MPa as saccharin concentration increases to 1.2 g/L. The results of DSC curves show that the grains start to grow until 600 °C and keep the thermal stability near to bulk nickel when grain sizes are in the range from 28 nm to 98 nm. However, when the grain size is 10 nm, the grains grow abnormally at 317 °C, and their thermal stability decrease sharply.

Influence of mode of electrodeposition, current density and saccharin on the microstructure and hardness of electrodeposited nanocrystalline nickel coatings

Abstract The main purpose of the present work is to study the influence of current density, deposition mode and the presence of saccharin as an additive on the microstructure, sulfur content, grain size and microhardness of nanocrystalline Ni coatings. Towards this purpose, nanocrystalline nickel (Ni) coatings were deposited at various current densities in Watt's bath using direct, pulse and pulse reverse current (PRC) electrodeposition and subsequently characterized for sulfur content, grain size and hardness. It was observed that, the current density has no influence on the grain size/hardness of nanocrystalline Ni coatings in direct and pulsed current electrodeposition mode. However, the grain size increased from ~ 20 to ~ 200 nm with decrease in current density in PRC mode of deposition. In addition a substantial change in microstructure and texture of PRC Ni coatings was also evident. The experimental results have been rationalized based on the adsorption–desorption type of mechanism during electrodeposition.

Effect of Microstructures on Corrosion Behavior of Nickel Coatings: (II) Competitive Effect of Grain Size and Twins Density on Corrosion Behavior

Nanocrystalline nickel coatings with grain size of 50 nm were annealed in vacuum at 200 °C and 400 °C for 10 min. Their microstructures were investigated by transmission electron microscopy (TEM). And their corrosion behaviors were studied by means of polarization and electrochemical impedance spectroscopy (EIS). The results showed that their grain size grew up to about 60 nm (200 °C) and 500 nm (400 °C), respectively. The specimen annealed at 200 °C possessed higher density of twins in compared with the counterparts of as-deposited and annealed at 400 °C. The normal grain size effect on the corrosion behavior was not observed. However, it was found that the corrosion resistance of the coating linearly changed with the density of twins.

Electrodeposition of nanocrystalline nickel assisted by flexible friction from an additive-free Watts bath

Nanocrystalline nickel coatings with different grain sizes were prepared by a modified electrodeposition technology assisted by flexible friction from an additive-free Watts bath. The effects of various flexible media, e.g. polymers, bio-bristles and natural fibers, on the morphology, preferred orientation, and grain size of electrodeposited nickel coatings were studied at different temperatures. The results demonstrate that flexible friction can effectively hinder the aggregation growth of adsorbed atoms and remove some surface-adsorbed species, to significantly refine the grain size and change the preferred orientation of deposits. The crystal growth inhibition effect significantly increases with temperature and incremental contact pressure of flexible friction. At 50°C, the nanocrystalline nickel coating gained by bio-bristle friction is the smoothest and has a dense surface morphology with a (111) preferred orientation. The corresponding grain sizes concentrate in the range of 20–30nm, and the microhardness is between 470 and 500HV, which is higher than that of the traditional electrodeposited nickel coating (320HV). The grain refining mechanism, texture evolution and microhardness variation of nickel deposits assisted by flexible friction are discussed.

X-ray diffraction grazing-incidence methods applied for gradient-free residual stress profile measurements in electrodeposited Ni coatings

The present work investigates the possibility of bias introduced in grazing-incidence-angle X-ray diffraction techniques applied to residual stress measurements. In these studies, monotextured nanocrystalline nickel coatings obtained by electrodeposition were examined as the model reference samples. Selected Ni coatings exhibited well developed and simple gradient-free residual stress states that were visible using conventional sin2ψ measurements with varying X-ray penetration depths. These results were verified against the stress state picture obtained by two variants of grazing-incidence X-ray methods: multi-reflection (differenthkl) and constant angle of incidence (singlehkl). The outcome of both grazing techniques consistently excluded stress gradients in the samples, which agreed with conventional sin2ψ measurement results. However, only the results of the constant angle of incidence technique agreed with those obtained by the sin2ψ method in terms of calculated residual stress level, suggesting this approach could be applied in further studies of graded material coatings. All analysed coatings yielded uniformly distributed tensile residual stress related to gradual structure development in electrodeposited Ni coatings studied by electron microscopy techniques.

The effects of current density and saccharin addition on the grain size of electroplated nickel

Nanocrystalline nickel (Ni) coatings were synthesized by direct current electrodeposition at current density from 1 to 30 mA/cm2 and pH 4. The basic composition of the bath, which was prepared by dissolving Ni metal particles in HCl, was 0.2 M Ni ions. The effects of the current density and saccharin addition on the average particle size of Ni deposits were investigated by XRD and SEM techniques. The results showed that the surface roughness decreased as the saccharin concentration increased to 2 g/l, while a further increase in saccharin concentration had no significant effect. The current density for deposition of Ni was increased as the saccharin concentration increased. The experimental results showed that the increase in the current density had a considerable effect on the average particle size of the Ni deposits.

Effect of Pulse Electrodeposition on Properties of Nanocrystalline Nickel Coatings

In this work, nanocrystalline nickel coatings were electrodeposited from a Watts bath using direct (DC) and pulsed (PC) current. Effect of deposition conditions on the morphology, hardness, grain size, surface roughness and corrosion resistance of nickel coatings were investigated. Ni films deposited by PC method exhibited greater hardness values and smaller crystallite size compared to those deposited by DC method. A preferential crystallographic orientation or texture was found in the nickel films depending upon the electrodeposition pulse shape, as it is polycrystalline in the DC electrodeposited films, while exhibit <111> crystallographic growth direction for PC method. Corrosion evaluation results showed that the PC electrodeposited nanocrystalline Ni films have higher corrosion resistant compared to those deposited with the DC method in 2 mol/liter NaOH solution.

Micro-scale testing of ductile and brittle cantilever beam specimens in situ with a dual beam workstation

Micro-scale cantilever beam specimens created by focused ion beam milling have been mechanically loaded in situ at room temperature to observe the deformation and fracture of single crystal silicon, nanocrystalline nickel and thermal barrier coatings with a multilayer structure. The micro-scale preparation technique allows cantilever beams to be selected from preferred positions in the samples so that specific mechanical properties can be evaluated. As a consequence these microstructural specific properties can be combined with direct observation of the response of the test specimen throughout the period of the test. The measured mechanical properties and response for the materials given above are discussed and compared with previously published data.