Electrolytic Bath Research Articles

Evaluation of the Effect of Deposition pH on the Physico-chemical Properties of Electrochemically Deposited Cadmium Telluride for Photovoltaic Device Applications

Two-electrode (2E) configuration was successfully utilised in the electrochemical deposition of cadmium telluride (CdTe) on fluorine-doped tin oxide (FTO) substrate with the main emphasis on the electrolytic bath pH. The electrochemical deposition pH explored is within the range of (1.00 to 6.00)±0.02 for the aqueous electrolyte comprising of tellurium oxide (TeO2) and cadmium nitrate (Cd(NO3)2) which are the respective precursors of Te and Cd. The optical, structural, morphological, compositional, and electrical properties of the electroplated CdTe thin-films were respectively explored using UV-Vis spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and photoelectrochemical (PEC) cell measurements. The optical characterisation show that the CdTe samples exhibit dissimilar absorbance depending on the growth pH for both the as-deposited layers and post-growth treated CdTe layers. A decrease in the absorption edge slope and dip in the bandgap was observed away from pH2. The bandgap of the post-growth treated CdTe layers showed enhancement as it leans towards 1.45 eV, with the trend retention of absorption edge slope, similar to the as-deposited CdTe layers. The electrodeposited CdTe thin-films show a dominant orientation along the cubic (111) CdTe plane, while both the the calculated crystallite size and the XRD peak intensity Pi decreases with the electroplating pH outside the (2.00 to 3.00)±0.02 range. The EDX analyses depicts an alteration in the ratio of Cd to Te atomic percentage relative to the pH of the electrolyte. Comparatively high Te atomic ratio was observed at lower pH values and vice versa with increase alkalinity of the electrolyte. The obtained morphology depicts that the underlying FTO layers are well covered with a gradual reduction in the grain size of the CdTe observable away from pH value (2.00 and 3.00). The photoelectrochemical cell study depicts that the conduction type of the CdTe layers can also be attributed to the CdTe-electrolytic bath pH value.

HBM4EU chromates study - Overall results and recommendations for the biomonitoring of occupational exposure to hexavalent chromium

Exposure to hexavalent chromium [Cr(VI)] may occur in several occupational activities, e.g., welding, Cr(VI) electroplating and other surface treatment processes. The aim of this study was to provide EU relevant data on occupational Cr(VI) exposure to support the regulatory risk assessment and decision-making. In addition, the capability and validity of different biomarkers for the assessment of Cr(VI) exposure were evaluated.The study involved nine European countries and involved 399 workers in different industry sectors with exposures to Cr(VI) such as welding, bath plating, applying or removing paint and other tasks. We also studied 203 controls to establish a background in workers with no direct exposure to Cr(VI). We applied a cross-sectional study design and used chromium in urine as the primary biomonitoring method for Cr(VI) exposure. Additionally, we studied the use of red blood cells (RBC) and exhaled breath condensate (EBC) for biomonitoring of exposure to Cr(VI). Personal measurements were used to study exposure to inhalable and respirable Cr(VI) by personal air sampling. Dermal exposure was studied by taking hand wipe samples.The highest internal exposures were observed in the use of Cr(VI) in electrolytic bath plating. In stainless steel welding the internal Cr exposure was clearly lower when compared to plating activities. We observed a high correlation between chromium urinary levels and air Cr(VI) or dermal total Cr exposure. Urinary chromium showed its value as a first approach for the assessment of total, internal exposure. Correlations between urinary chromium and Cr(VI) in EBC and Cr in RBC were low, probably due to differences in kinetics and indicating that these biomonitoring approaches may not be interchangeable but rather complementary.This study showed that occupational biomonitoring studies can be conducted successfully by multi-national collaboration and provide relevant information to support policy actions aiming to reduce occupational exposure to chemicals.

Aluminum Protection by Using Green Zirconium Oxide Layer and Organic Coating: An Efficient and Adherent Dual System

In this work, the use of ZrO2 nanocoating in aluminum substrates, generated by controlled electrochemical chronoamperometry in hexafluorozirconic acid solutions (H2ZrF6·5H2O), resulted in a lower porous films than that obtained by chemical conversion coating. After the application of an epoxy coating, long-term cyclic immersion corrosion tests and scratch tests proved the superior protection of the dual system and the coating lifespan, thanks to the enhanced adhesion of ZrO2 intermediate layer and the organic coating. As zirconium-based electrolytes are considered more friendly bath if compared to that of other conversion coating processes, like chromating, phosphating or anodizing processes, the study opens new insights to the protection of structural metals in sectors such as automotive, naval and aerospace industries. The main advantages are the employment of lightweight intermediate pre-treatment (nanoscale), compared to conventional ones (microscale), and reduction of waste slurry (electrolyte bath free of additives).

Effect of copper additive on microstructure and anti-corrosion performance of black MAO films grown on AZ91 alloy and coloration mechanism

Black micro-arc oxidation (MAO) films on AZ91 alloy were successfully fabricated using MAO technique in a designed bath of silicate electrolyte with addition of colorant copper additive aiming to extend the application scope of magnesium and its alloys. It was found that the color of MAO films on AZ91 alloy changed gradually from white to black with the increasing copper ion concentration. The black color MAO films formed on AZ91 alloy may mainly be owing to the existence of CuO particulates in the porous outer layer. In addition, incorporation of CuO in the uniform and compact MAO films could significantly improve the anti-corrosion property of AZ91 substrate, thus effectively prevent the inward migration of corrosive medium. Copper additive concentration of electrolyte also affected the surface roughness of MAO films. The increase of copper additive concentration may result in an increase in the thickness and compactness of the black MAO films, and finally an enhancement in their corrosion resistance. Therefore, the MAO technique method coupled with silicate electrolyte containing copper additive was a promising surface modification technique for magnesium alloys.

Uncertainty Quantification Analysis on Silicon Electrodeposition Process Via Numerical Simulation Methods

Abstract Silicon is one of the commonly used semiconductors for various industrial applications. Traditional silicon synthesis methods are often expensive and cannot meet the continuously growing demands for high-purity Si; electrodeposition is a promising and simple alternative. However, the electrodeposited products often possess nonuniform thicknesses due to various sources of uncertainty inherited from the fabrication process; to improve the quality of the coating products, it is crucial to better understand the influences of the sources of uncertainty. In this paper, uncertainty quantification (UQ) analysis is performed on the silicon electrodeposition process to evaluate the impacts of various experimental operation parameters on the thickness variation of the coated silicon layer and to find the optimal experimental conditions. To mitigate the high experimental and computational cost issues, a Gaussian process (GP) based surrogate model is constructed to conduct the UQ study with finite element (FE) simulation results as training data. It is found that the GP surrogate model can efficiently and accurately estimate the performance of the electrodeposition given certain experimental operation parameters. The results show that the electrodeposition process is sensitive to the geometric settings of the experiments, i.e., distance and area ratio between the counter and working electrodes; whereas other conditions, such as the potential of the counter electrode, temperature, and ion concentration in the electrolyte bath are less important. Furthermore, the optimal operating condition to deposit silicon is proposed to minimize the thickness variation of the coated silicon layer and to enhance the reliability of the electrodeposition experiment.

Speciation Analysis of Arsenic in Copper Electrolyte Baths Using Liquid-liquid Extraction and ICP-OES Method Detection

Speciation Analysis of Arsenic in Copper Electrolyte Baths Using Liquid-liquid Extraction and ICP-OES Method Detection

Alginate Biopolymer Effect on the Electrodeposition of Manganese Dioxide on Electrodes for Supercapacitors

Electrolytic manganese dioxide (EMD) synthesized from different electrolytic baths with varying biopolymer additive concentrations has been investigated for application as an electrochemical supercapacitor. Alginic acid, also termed “alginate”, is a widely used biopolymer for various biological applications due to its physicochemical properties. Here, the EMD material synthesized with alginate crosslinking was introduced in the field of electrochemistry for supercapacitors. Different EMD and alginate composites were characterized to find the trade-off between the biopolymer content in the bath and the energy storage capability. Compared to the pristine EMD, the EMD composites at all of the alginate concentrations influenced both the physical and the electrochemical storage properties of the materials. The presence of alginate in the solution at higher concentrations altered the morphology from spindle-shaped to cactus-shaped with flutes. Rearranged morphology and enhanced particle size are attributed to the ability of the alginate to act as a template for binding the Mn2+ ions on the substrate in a relatively ordered and widely distributed manner. The EMD composite delivered 5 times higher capacitance (487 F g–1) than the pristine EMD at a current density of 1 mA cm–2 in a three-electrode system using a 2 M NaOH aqueous electrolyte. When the EMD composite was coupled with activated carbon, the asymmetric device exhibited 52 F g–1 capacitance at a current density of 2 mA cm–2 while giving excellent capacitance retention (94%) over 5000 cycles. The molecular dynamics simulation model supported the influence of alginate on ion–polymer interactions in the electrolytic bath. The simulations showed that the alginate provides a template for binding Mn2+ ions in a relatively ordered manner. It could assist the EMD/Alg composite growth in a more favorable condition for energy storage applications.

Morphology and Corrosion Behavior of Zn-Ni Layers Electrodeposited on Low Alloy Carbon Steel Substrate

The aim of this work is to improve the microstructure, the morphology, the mechanical and the corrosion behavior of Zn-Ni layers electrodeposited on low alloy carbon steel. Some factors such as the nickel concentration in the electrolyte, the electrolyte temperature and the current density are studied and optimized. The efficiency of the layers to protect the low alloy carbon steel against corrosion in HCl solution is also studied in this work. The electrodeposited Zn-Ni layers morphologies and microstructure were investigated by Scanning Electronic Microscopy (SEM) and X-ray diffraction (XRD) respectively. The best deposits of Zn-Ni layers are obtained with 50%-Ni in the electrolyte bath at a temperature of 40°C and a current density of j = 3 A dm-2. The XRD spectrum showed the coexistence of two phases: δ-phase (Ni3Zn22) and γ-phase (Ni5Zn21), and a pyramidal morphology is detected by SEM. The lost mass method results showed that the corrosion rate tacked a steady state between 10 and 50% of Ni, and it increased with the increase of Ni amount in the electrolyte bath.

Zn–Mn alloy coatings electrodeposited from acidic sulfate-citrate bath

The Zn–Mn alloy electrodeposition on steel substrate from sulfate-citrate bath was investigated using cyclic voltammetry. In a metal ion-free solution, an electrochemical analysis showed that increasing the citrate concentration induces the increase in the overpotential for hydrogen evolution reaction, with an optimum citrate concentration of 0.6 mol dm−3. Cyclic voltammograms recorded in the electrolyte with Zn2+ and Mn2+ ions, reveal that the potential of Zn–Mn alloy electrodeposition (-1670 mVSSE) stands between those of pure Zn (-1500 mVSSE) and pure Mn (-1850 mVSSE) electroreduction. The effect of [Mn2+]/[Zn2+] ratio in the electrolyte on the Mn content in the obtained Zn–Mn coatings was studied. It was found that the Mn content increases with increasing the [Mn2+]/[Zn2+] ratio in the electrolytic bath. The surface morphology and crystalline phase structure of Zn–Mn deposits were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD), respectively.

Surface Structure Control and Charge/Discharge Characteristics of Bismuth Anode Materials By Electrodeposition for Magnesium-Ion Batteries

The magnesium ion secondary battery (MIB) has attracted much attention because magnesium (Mg) metal has high theoretical capacity (3,755 mAh/cm3), high electrochemical stability, and high abundance in the earth. However, developing anode and cathode materials with superior capacity for conventional electrolytes has required considerable study. Bismuth (Bi) has high capacity as an anode and also resists oxidation in Mg-containing electrolyte, so is a promising candidate material. However, experimental studies suggest that the available capacity has not yet reached the theoretical limit, and that the cycle life is short. This is due to sluggish diffusion of Mg2+ into the anode material and the slow interfacial charge transfer. We aimed to improve the electrochemical properties by atomizing the internal and surface structure of the Bi anode and enhancing the diffusibility of Mg2+. In this study, we prepared Bi films by an electrodeposition method, in which the structure of the Bi electrodes could be controlled by changing some of the electrodeposition conditions. We also evaluated the electrochemical properties of Bi anode materials deposited with different deposition times and current densities, to elucidate the relationships between the structure of the Bi anode and its capacity and cycle life.We prepared an electrolytic bath by dissolving H2SO4, Na2SO4 and polyethylene glycol in pure water, and subsequently added H2SO4 to the electrolytic bath to control the pH at 1.2. Before electrodeposition, we removed organic species and native oxide from the Cu foil surface with NaOH and HCl. We employed a Cu plate with an exposed foil area of 2 × 2 cm2 and a carbon plate as the cathode and anode, respectively. The Bi electrodeposition was carried out, while changing the deposition time and current density (from 10 to 50 mA/cm2). The film thickness was controlled by the deposition time (from 1.5 to 3.0 μm), and was calculated based on the weight increase under the assumption that the film was uniform. The surface morphology and crystal structure of the Bi films were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. In addition, the characteristics were compared before and after discharge/charge. The cycle characteristics of the Bi anodes were studied in PhMgCl/THF electrolyte. The bipolar half-cells were assembled with Mg plate as the anode and Bi electrode as the cathode. We established representative galvanostatic charge/discharge profiles of the Bi electrodes, at a current density of 50 mA/g within 0–0.6 V, versus Mg2+/Mg. We evaluated the cyclic stability of the Bi electrodes under the same conditions until the 50th cycle. The elemental composition and chemical bonding state of the Bi films after charge/discharge were evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS).Figure 1 shows the cycling performance of Bi films with thicknesses of 1.5, 2.0, and 3.0 μm until the 50th cycle. Each film showed a capacity of about 300 mAh/g at the early stage of cycling, which is the maximum capacity. The capacities were about 1.5 times those of the Bi anodes which Niu et al. prepared by powder metallurgy. The cycle performance differed among Bi films differing in thickness, and the 1.5-µm Bi film maintained the maximum capacity until the 25th cycle. Thus, film thickness had an impact on the cycle performance.Figure 2 shows the surface morphology of Bi films with different thicknesses before and after the charge/discharge reaction. The figure also shows the compositional ratio of Bi to Mg on the surface of the Bi films. As the film thickness increased, agglomerates involving a large number of particles, indicated by the circles marked by “A” in Fig. 2, tended to increase in diameter from 1 to 3 µm. After charging/discharging, Mg dendrites were observed on the surface of the Bi films with thicknesses of 2 and 3 µm (circles marked by “B”), which resulted in a low capacity maintenance rate. Thus, the localized formation of Mg dendrites on the Bi surface could explain the decreased cycle performance of the Bi films prepared in this study. Figure 1

Electrodeposition of Platinum Group Metals for Interconnects Beyond 5nm Technology Node

For technology nodes beyond 5 nm, copper metal may not be feasible as conductor material in Damascene interconnects.1 The bulk resistivity of copper increases exponentially and electromigration of copper is possible with the scaling down of the technology nodes. Metals such as inert platinum group metals have been proposed as alternative metal conductors for interconnects.2 Platinum group metals exhibit less electron scattering and lower electromigration in narrow line widths compared to copper; the electron scattering is proportional to the bulk resistivity. Thus, certain platinum group metals, e.g., ruthenium2, have been proposed as alternative conductors for interconnects.3 Ruthenium electrodeposition needs further development because of slow kinetics, resulting in poor control of morphology, and defects in the film due to hydrogen evolution at the high overpotential required to initiate ruthenium deposition.4 Another challenge is that ruthenium has multiple oxidation states, which may result in disproportionate reactions, and, thus, electrodeposition may not occur reproducibly.3This study investigates the electrodeposition of ruthenium from nitrosyl ruthenium complexes, and/or inorganic ruthenium compounds such as chlorides, sulfates or phosphates in acidic electrolytes. Figure 1 shows ruthenium electrodeposited on an ultrathin seed layer with high sheet resistance. Electrodeposition techniques such as chronoamperometry and chronopotentiometry are compared for the initiation of ruthenium nuclei on such highly-resistive (up to 400 Ω/sq) seed layers. In this study, a multi-step electrodeposition process was developed for the nucleation, then growth of a uniform, void-free ruthenium film. A constant voltage was applied for a short time (few seconds) to initiate plating by providing the overpotential necessary to form ruthenium nuclei. Next, a low current density was applied to grow the film to the desired thickness (50 – 100 nm). This method allows for minimal hydrogen evolution and prevents void formation since the high potential is applied for a short time compared to other typical pulse plating methods. The multi-step method is reproducible and results in uniform plating on 200 mm wafer scale by utilizing plating tool shields that can control center and edge plating rates. This talk describes the effect of electrolyte bath composition and plating parameters on the morphology, adhesion and uniformity of the electrodeposited ruthenium.Figure 1: Electrodeposited ruthenium on Si substrate with ultrathin seed layer.1) Chen, Q.; Lin, X.; Valvede, C.; Paneccasio, V.; Hurtubise, R.; Ye, P.; Kudrak, E.; Abys, J., Electroless copper deposition on ruthenium for damascene interconnects. ECS Transactions. 2007, 6 (8), 179-184.2) Mainka, G.; Beitel G.; Schnabel R.F.; Saenger, A.; Dehm, C., Chemical mechanical polishing of iridium and iridium oxide for damascene process. Journal of the Electrochemical Society. 2001, 148, G552-G558.3) Bernasconi, R.; Magagnin, L., Review—Ruthenium as diffusion barrier layer in electronic interconnects: Current literature with a focus on electrochemical deposition methods. Journal of the Electrochemical Society. 2019, 166 (1), D3219-D3225.4) Oppedisano, D.K.; Jones, L.A.; Junk, T.; Bhargava, S.K., Ruthenium electrodeposition from aqueous solution at high cathodic overpotential. Journal of the Electrochemical Society. 2014, 161 (10), D489-D494.AcknowledgementThe authors acknowledge the researchers of the Microelectronics Research Laboratory (MRL) at the IBM T. J. Watson Research Center, for the fabrication work. Figure 1

Development and Characterization of High Emittance and Low-Thickness Plasma Electrolytic Oxidation Coating on Ti6Al4V for Spacecraft Application

Plasma electrolytic oxidation (PEO) or microarc oxidation process has been carried out on Ti6Al4V substrate in electrolytic bath containing sodium silicate and sodium hypophosphate. The phase composition, microstructure and roughness of the PEO coating are examined by x-ray diffraction, scanning electron microscopy and profilometry techniques, respectively. Wavelength-dependent thermo-optical properties viz. solar absorptance ( $$\alpha_{s}$$ ) and IR emittance (eir) are recorded by UV-VIS-NIR and FTIR spectrophotometer, respectively. Nanomechanical properties such as nanohardness (H) and Young’s modulus (E) are evaluated by well-established nanoindentation technique. The PEO coating is found to be hydrophobic (contact angle ~108°) and possesses low thickness of 5-9 $$\upmu$$ m. Average eir is obtained to be 85% while average $$\alpha_{s}$$ is recorded as 76%. The characteristics H and E values are 2.59 GPa and 81.45 GPa, respectively. The PEO coating is also characterized with respect to potentiodynamic polarization and impedance spectroscopy to evaluate corrosion resistance. The total impedance and corrosion current density (icorr) are in the order of 1 MΩ and 10-8 µA.cm-2, respectively. The results indicate superior corrosion resistance of the present PEO coating compared to similar coatings reported in the literature.

The Effect of pH and Monomer Concentration on Polyaniline Thin Films Grown Using Electrodeposition

Polyaniline (PANI) thin films were successfully prepared from an aqueous electrolyte bath containing aniline and sulphuric acid (H2SO4) using electrodeposition method. The present study demonstrates that the properties of PANI thin film depends on the variation of pH and aniline concentration in prepared precursor. The optical and structural of PANI thin films were characterized using UV-Visible spectrometer (UV-Vis), X-ray diffraction spectrometer (XRD), Fourier Transform Infra-Red spectrometer (FTIR) and Raman spectrometer. PANI layer grown at pH 2.00 displayed green colour layer which denoted as emeraldine base (half oxidized state of PANI) while at pH 3.80 the colour of PANI layer was yellow representing the leucoemeraldine base (fully reduced state of PANI). Result obtained from FTIR confirmed the footprint of PANI and Raman spectrometer confirmed the half oxidized emeraldine base of PANI. Optical analysis using UV-Vis demonstrated the smallest energy band gap, Eg of PANI is 3.54 eV for sample with 0.50 M aniline concentration and pH 2.00. The trend shows that the bandgap of PANI is increased as the pH increased from 2.00 to 3.80. XRD result showed that all the deposited PANI layers were amorphous. Full characterization of this material is providing some information on PANI behavior due to pH and concentration in the prepared precursor.

Low temperature electrogalvanization: Texture and corrosion behavior

Electrogalvanization at room temperature using aqueous bath is extensively used for protection of steel in highly corrosive environments. Here, it is shown that low temperature galvanization conducted at ~2 °C using aqueous electrolyte bath produces Zn coating which exhibits significantly lower corrosion current density (icorr) value when compared to the icorr values of coatings deposited at room temperature (~28 °C) and high temperature (~60 °C) when these coatings are exposed to a corrosive environment (3.5 wt% NaCl solution). The icorr values for coatings deposited at 2 °C, 28 °C and 60 °C were 8.94 µA/cm2, 24 µA/cm2 and 182 µA/cm2 respectively. Micro-texture analysis revealed that the texture (grain orientation and grain boundary constitution) of the coatings is also highly sensitive to the deposition temperature. Higher corrosion resistance observed in case of 2 °C deposited coatings was due to factors such as growth of grains oriented with relatively inert basal plane on the coating surface which retards the transgranular corrosion and presence of higher fraction of low energy special boundaries (such as low angle grain boundaries, coincidence site lattices and symmetrical tilt grain boundaries) which retards the intergranular corrosion significantly.

Optimization of Ag2S Quantum Dots Decorated ZnO Nanorod Array Photoanodes for Enhanced Photoelectrochemical Performances

The synthesis of Ag2S quantum dots (QDs) deposited on the surface of electrodeposited ZnO nanorods (NRs) by a successive ionic-layer adsorption and reaction (SILAR) method is reported. A Box-Behnken response surface factorial design was used to organize the experiments conducted and identify the effects of three electrochemical parameters and their potential interactions. These parameters include zinc precursor concentration in the electrolytic bath, the electrolytic bath temperature and the electrodeposition time on the morphological and structural properties of the electrochemically grown ZnO nanorods. Morphological, structural and optical characterizations of these NRs heterojunctions were done. A direct band gap for Ag2S QDs, tuned between 2.54 and 2.73 eV by varying the SILAR cycle numbers, was determined. The presence of ZnO nanostructures increases the light scattering capability of the samples, allowing an important quantity of diffuse light near the absorption edge of Ag2S. The photoelectrochemical performance of these ZnO NRs decorated with Ag2S QDs based photoanodes has been evaluated. The SILAR parameters related to the growth of the Ag2S QDs that optimize the performance of this photoelectrode are presented. The effect of a ZnS passivation layer has been studied leading to an increase of about 400% in the short-circuit current density after passivation.

Functional Antimicrobial Surface Coatings Deposited onto Nanostructured 316L Food-Grade Stainless Steel.

In our study, we demonstrated the performance of antimicrobial coatings on properly functionalized and nanostructured 316L food-grade stainless steel pipelines. For the fabrication of these functional coatings, we employed facile and low-cost electrochemical techniques and surface modification processes. The development of a nanoporous structure on the 316L stainless steel surface was performed by following an electropolishing process in an electrolytic bath, at a constant anodic voltage of 40 V for 10 min, while the temperature was maintained between 0 and 10 °C. Subsequently, we incorporated on this nanostructure additional coatings with antimicrobial and bactericide properties, such as Ag nanoparticles, Ag films, or TiO2 thin layers. These functional coatings were grown on the nanostructured substrate by following electroless process, electrochemical deposition, and atomic layer deposition (ALD) techniques. Then, we analyzed the antimicrobial efficiency of these functionalized materials against different biofilms types (Candida parapsilosis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis). The results of the present study demonstrate that the nanostructuring and surface functionalization processes constitute a promising route to fabricate novel functional materials exhibiting highly efficient antimicrobial features. In fact, we have shown that our use of an appropriated association of TiO2 layer and Ag nanoparticle coatings over the nanostructured 316L stainless steel exhibited an excellent antimicrobial behavior for all biofilms examined.

Nanocrystalline nickel-tungsten alloys assisted by thermosonication: Effect of temperature on the anticorrosive properties

Ni-W coatings were evaluated considering the effect of ultrasound-assisted deposition and the electrolytic bath's temperature on the faradaic efficiency. Electrodeposition occurred with and without thermosonication (TS) at 40, 50, and 60 °C. Both process variables were significant (p-value<0.05). The temperature profile indicated that the nominal power of the system was 10.8 ± 0.3 W. The W content increased with the increase of the temperature and the use of ultrasound. Microcracks decreased due to an increase in the diffusion process generated by acoustic cavitation. The alloys presented nanocrystalline structures of Ni17W3 composition, with preferential orientation in the plane (220). The peaks slightly decreased with the increase of the temperature and under TS, indicating a tendency to amorphization. The coating produced at 50 °C without TS exhibited the highest polarization resistance value of 20.50 kΩ cm2. The electrochemical impedance spectra confirmed the Ni-W alloy's anticorrosion property with an equivalent circuit mainly composed of a non-ideal capacitor and a Warburg element.

Fractal Dimension and lacunarity based microscopic image texture characterization of coated and non-coated metallic substrates

ABSTRACT The degree of surface roughness as measured using Fractal Dimension and Lacunarity can serve as quality measures of the coating process. The smoothness of the surface before and after coating is an important characteristic frequently used in surface engineering, to obtain well-polished and smoothened surface finish. We have used Brass plates and coated it with Nickel using electroless and electroplating methods. The images of the coated surfaces were taken using an optical microscope before and after coating. Fractal Dimension (FD) and Lacunarity (λ) of the surface image before and after coating is calculated for comparison using Differential Box-Counting algorithm. Electro-cleaning of the samples in an alkaline degreasing solution is done. Electroplating is carried out in respective electrolytic bath under constant current and temperature conditions. Electroless coating is carried out with a separate Nickel bath at constant temperature of 85° C. The experimental data was validated, which revealed that FD and λ values decreased after coating in all the cases. The lower value of FD and λ after coating suggests more regularity in the surface patterns or smoothness. Hence, we conclude that FD and λ serve as relevant parameters depicting the quality of coating surface at significance level of 0.05.

Co-deposited Zn-Cu/Gr nanocomposite: Corrosion behaviour and in-vitro cytotoxicity assessment

ABSTRACT Zn-Cu alloys have been considered as potential candidates for bioimplant applications due to their moderate corrosion rate and admirable mechanical properties with non-toxic nature to the human body. However, with the incorporation of advanced reinforcements, such as carbon allotropes, the properties and applicability of a Zn-Cu alloy matrix can be further enhanced. In this research, graphene (Gr) nanoplatelets reinforced Zn-Cu/Gr nanocomposites were synthesised through a modified electro-codeposition method with different concentrations of Gr (25, 50 and 100 mg L−1) in the electrolyte bath. The prepared powder samples were compacted and sintered to form pellets. The pellets were tested for mechanical and in-vitro corrosion. The obtained micro-hardness, compressive yield strength (CYS) and ultimate compressive strength (UCS) of Zn-Cu/Gr (100 mg L−1) nanocomposite are 151 HV, 340 MPs and 362 MPa with increments of 84.1%, 118% and 70.7% compared to pure Zn-Cu alloy, respectively. The reduced wear rates and friction coefficients of Zn-Cu/Gr nanocomposites are attributed to crystallite size refinement and Gr content. The electrochemical corrosion rate is reduced by 66.6% from 33 × 10−3 mm year−1 for pure Zn-Cu alloy to 11 × 10−3 mm year−1 for Zn-Cu/Gr (100 mg L−1) nanocomposites, owing to Gr barrier protection. The in-vitro cytotoxicity assessment reveals that the prepared Zn-Cu/Gr nanocomposite is non-toxic for Gr concentration up to 50 mg L−1 in the electrolyte bath. The results show that a non-toxic Zn-Cu/Gr nanocomposite with outstanding tribo-mechanical and anti-corrosion properties can be synthesised by the proposed method.

Optical and Morphological Properties of Electrodeposited Thin Films of ZnS

Zinc sulphide (ZnS) thin films were grown on glass/fluorine-doped tin oxide (FTO) substrates using the simple and inexpensive electrodeposition technique. The deposition electrolytic bath was prepared from aqueous acidic solution of ZnSO4 and (NH4)2S2O3. The work was carried out to investigate the optical and morphological properties of ZnS layers. The deposition temperature and the pH values were respectively 30°C and 1.50. It was observed that optical properties vary with variation in growth voltage. It was observed that bandgap decrease with increase in growth voltage since the higher the growth voltage, the higher the current density. As the deposition temperature in increased, the bandgap is seen to decrease. After annealing, the bandgaps are seen to increase and the absorption edges can be seen to have smoothened out. Increase in annealing temperature play a significant role in achieving desired results especially when it is meant for device application. As expected, the layer thickness is seen to increase with increase in deposition temperature.