Pulse Reverse Electrodeposition Technique Research Articles

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

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

Electrocatalytic Properties of Pulse-Reverse Electrodeposited Nickel Phosphide for Hydrogen Evolution Reaction.

Nickel phosphide (Ni-P) films as a catalytic cathode for the hydrogen evolution reaction (HER) of a water splitting were fabricated by a pulse-reverse electrodeposition technique. The electrochemical behaviors for the electrodeposition of Ni-P were investigated by the characterization of peaks in a cyclic voltammogram. The composition of the electrodeposited Ni-P alloys was controlled by adjusting duty cycles of the pulse-reverse electrodeposition. The HER electrocatalytic properties of the Ni-P electrodeposits with an amorphous phase as a function of phosphorous contents existing in Ni-P were electrochemically characterized by the analysis of overpotentials, Tafel slopes, and electrochemical impedance spectrometry. Additionally, the elemental Ni-embedded crystalline Ni3P was prepared by an annealing process with the amorphous Ni69P31 electrodeposit with high contents of phosphorus. The crystalline structure with Ni inclusions in the matrix of Ni3P was formed by the precipitation of excess Ni. The electrocatalytic properties of crystalline Ni3P with elemental Ni inclusions were also investigated by electrochemical characterization.

Assessment and effect of reinforcement of multi-walled carbon nanotubes in Ni-Al2O3 and Ni-SiC nanocomposite coatings using pulse reverse electrodeposition technique

The nanocomposite coating provides a higher degree of corrosion resistance, microhardness, wear resistance and significantly improves the tribological qualities of the base metal. This research work is aimed at investigating the effect of the proportion of multi walled carbon nanotubes (MWCNT) mixed with Ni-Al2O3 and Ni-SiC nanocomposite coatings on a mild steel AISI 1018 specimen against its tribological characteristics through experimental investigation. The pulse reverse electro deposition technique is deployed for coating formulation with optimized coating parameters. The proportions of carbon nanotubes vary in three different ratios ranging from 1:1 to 2 :1. Tribological characteristics (microhardness and surface morphology) are assessed using a Vickers microhardness testing machine and a scanning electron microscope (SEM). Nine different coating combinations are considered in this study and their tribological attributes are compared with the un-coated sample. From the results, it can be observed that the samples coated with Al2O3 nanoparticles reinforced with carbon nanotubes (CNTs) possess excellent magnitudes of micro-hardness in comparison with the uncoated and SiC-CNT coated samples with an enhancement factor of 2.88 and 1.37, respectively. Moreover, the variation of the CNT proportion in the coating blend has the tleast significant effect and therefore, addition of CNT particles beyond the blend ratio of 1:1 may be avoided to reduce the coating cost of samples significantly. Also, SEM images clearly reveal a uniform coating distribution owing to the application of optimized coating parameters. .

Assessment on the microhardness and corrosion resistance characteristics of Ni-SiC and Ni-MWCNT coatings by pulse reverse electrodeposition technique

The characteristics of Silicon carbide (SiC) and multi-walled carbon nanotube (MWCNT) nano composite coatings by a Pulse Reverse Electrodeposition (PRE) method is investigated in detail to enhance the microhardness (MH) and corrosion resistance characteristics of AISI 304 stainless steel substrate. The electrodeposition nature, dissolution behavior, surface characteristics are assessed by Scanning Electron Microscopy (SEM) with energy dispersive x-ray (EDX), x-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Microhardness (MH) Test and Electrochemical studies. The coatings are prepared in the watts type bath using pulse reverse electrodepositions (PRE) method of varying the electrolyte deposition parameters in different combinations. Present results clearly reveal that, there is a drastic improvement in the magnitude of microhardness of coated specimens, silicon carbide (SiC) and multi-walled carbon nanotube (MWCNT) composite coatings yield a maximum hike of 91.6% and 168% respectively. Furthermore, the Nyquist and impedance plots clearly depict that, multi-walled carbon nanotube (MWCNT) exhibits higher corrosion resistance characteristics.

Cu(In,Ga)Se2 Films with Branched Nanorod Architectures Fabricated by Economic and Environmentally Friendly Pulse-Reverse Electrodeposition Route

Cu(In,Ga)Se2 (CIGS) materials are one of the most promising solar cell technologies owing to their large absorption coefficient and tunable direct bandgap, and they have gained considerable commercial maturity. The study herein puts forward the preparation of nanostructured CIGS films containing branched nanorod architectures, which is reported for the first time. The process employs an economic pulse-reverse electrodeposition technique by utilizing the fundamentals of electro-reduction and oxidation to fabricate nanostructured CIGS and completely avoids conventional energy-intensive high-temperature annealing/selenization step. Comprehensive characterization of nanoarchitectured films reveals the stoichiometric composition and chalcopyrite structure with dominant (112) orientation. Nanostructured CIGS exhibits excellent photoactivity with a photocurrent density of 4.31 mA/cm2 at −0.13 V vs RHE in a liquid junction, which is highest for a bare CIGS film and is attributable to its inherent high interface a...

Three-dimensional architectures of graphene oxide–polyaniline nanocomposites synthesized by the pulse reverse electrodeposition technique for supercapacitor applications

Binder-free graphene oxide (GO)-polyaniline (PANI) nanocomposites with three-dimensional structures and good capacitive characteristics were prepared by pulse reverse electrodeposition of PANI and GO onto the previously formed TiO2 nanotubes (TiO2NTs). In the composite, interconnected reduced graphene oxide sheets constitute a high-efficient conductive network to improve the capacitive behavior of PANI. Furthermore, the network structure of the nanocomposites facilitates fast diffusion of electrolytes, which can significantly improve the parameters effectively influencing the capacitive behavior such as electrical conductivity and specific capacitance. The electrochemical data demonstrated that the specific capacitance of these electrodes was around 132 mF cm−2 in 1.0 M H2SO4 electrolyte as measured at a constant current of 0.66 mA cm−2, whereas it was 34 and 77 mF cm−2 for the GO/TiO2NT and PANI/TiO2NT electrodes, respectively.

Process Optimization for Pulse Reverse Electrodeposition of Graphene-Reinforced Copper Nanocomposites

In the present study, processing of graphene-reinforced copper nanocomposite foils with homogenous dispersion of graphene throughout the matrix, exhibiting good mechanical properties by a simple, cost-effective, and scalable pulse reverse electrodeposition technique (PRED) with special focus on the influence of graphene content in the electrolyte to tailor the properties. A systematic approach has been adopted for enhancing the properties. Distribution of graphene nanosheets in the copper metal matrix and the microstructural properties have been studied by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). Interesting observations have been made from nanoindentation studies, where hardness (∼2.7 GPa) enhanced mainly with increase in graphene content (0–0.75 g/L), while maximum elastic modulus (∼139 GPa) is achieved for a graphene content of 0.5 g/L in the electrolyte. Four-point probe testing has been adopted to evaluate the electrical features. The major contribution in enhancement of properties is found to be the presence of graphene and its uniform individual dispersion and distribution as nanosheets in the copper matrix.

Controllable Crystallographic Texture in Copper Foils Exhibiting Enhanced Mechanical and Electrical Properties by Pulse Reverse Electrodeposition

The texture evolution in copper foils prepared by a rapid pulse reverse electrodeposition (PRED) technique using an “additive-free” electrolyte and the subsequent correlation with the mechanical and electrical properties is investigated in this study. Control over (111), (100), and (101) crystallographic textures in copper foils has been achieved by optimization of the pulse parameters and current density. A hardness as high as 2.0–2.7 GPa, while the electrical conductivity was maintained in the same range as that of bulk copper, was exhibited by these foils. A complete study of controlling the (111), (100), and (101) textures, CSL Σ3 coherent twin boundaries, grain refinement, and their effect on the mechanical and electrical properties is performed in detail by characterizing the foils with electron backscatter diffraction, X-ray diffraction, nanoindentation, and electrical resistivity measurements. The PRED technique with short and high-energy pulses allowed the (111) texture with increase in forward o...

Fabrication of microcellular metal foams with sphere template electrodeposition

Microcellular metal foam (MMF) is a new class of metallic material with many potential applications such as solar energy storage. In this study we present a sphere template electrodeposition process for bulk MMF fabrication. To overcome ion diffusion limitation and uneven metal growth problems we explore the benefit of a pulse reverse electrodeposition technique. An experimental study was conducted on the effect of pulse voltage and frequency. It is shown that metal deposition uniformity can be significantly improved with high pulse frequency and amplitude. This study suggests that bulk MMFs could be fabricated with a microsphere template electrodeposition process.

Morphology and composition control of manganese oxide by the pulse reverse electrodeposition technique for high performance supercapacitors

Manganese oxide (MnOx) nanostructures were synthesized by the pulse reverse electrodeposition technique for electrode materials of supercapacitors. The morphology and composition of MnOx were controlled by the pattern of applying potential. In the case where constant potential (CP) was applied, a bulk film of aggregated MnO2 particles was obtained. However, Mn2O3 nanostructure was obtained by pulse potential (PP) or pulse reverse potential (PRP) methods (1/0 V or 1/−1 V). Furthermore, fine nanorod morphology with high electrical conductivity was produced by the pulse reverse potential method which resulted in excellent capacitive performance. The specific capacitance of the Mn2O3 nanorod structure produced by the PRP method was 448 F g−1 at 10 mV s−1. From charge–discharge testing, specific capacitance values of 306 F g−1 and 211 F g−1 were obtained at current densities of 10 A g−1 and 100 A g−1, respectively, indicating high rate capability. The electrode provided exhibited excellent electrochemical stability with a retention life of 99% after 20 000 cycles.

Effects of duty cycle on properties of CIGS thin films fabricated by pulse-reverse electrodeposition technique

DC and pulse-reverse electrodeposition mode were employed for the deposition of polycrystalline Cu(In,Ga)Se2 thin films. In comparison with DC electrodeposition mode, films obtained by pulse-reverse electrodeposition were smoother, denser and more uniform with good adhesion. The Ga content in final composition of CIGS thin film was improved in pulse-reverse electrodeposition mode. In addition, pulse-reverse electrodeposited CIGS thin films were more crystalline with chalcopyrite structure. The compact morphology without pores in the deposit was achieved in the pulse-reverse electrodeposited CIGS thin films by varying duty cycle.

CuIn1 − xGaxSe2 Absorber Layer Fabricated by Pulse-Reverse Electrodeposition Technique for Thin Films Solar Cell

A single phase of (CIGS) polycrystalline thin films was successfully fabricated by the pulse-reverse electrodeposition technique. In this study, a multipulse sequence of potentials with varying amplitude and duration time was used to fabricate CIGS thin film, in which the electrolyte was composed of , , , , Na-citric, and LiCl. Then these as-deposited films were annealed in argon atmosphere. The crystalline structure of the thin film was characterized by X-ray diffractometer. The results revealed that thin films fabricated by the pulse-reverse electrodeposition technique only produced a chalcopyrite structure, with no occurrence of secondary phases. The identification of secondary microcrystalline phases and vibration modes of chalcopyrite and was used by a micro-Raman spectrum. The morphological features were characterized by scanning electron microscopy, which showed that the films were dense and smooth compared with that fabricated by a one-step electrodeposition technique without a multipulse step. The thickness and roughness of the CIGS thin films were estimated by an Alpha-Step profilometer. Finally, the carrier type of the CIGS thin film is of a p-type nature as confirmed by electrochemical measurement.

Synthesis of ZnTe nanowires onto TiO 2 nanotubular arrays by pulse-reverse electrodeposition

Growth of ZnTe nanowires using a pulse-reverse electrodeposition technique from a non-aqueous solution is reported. ZnTe nanowires were grown on to an ordered nanotubular TiO 2 template in a propylene carbonate solution at 130 °C inside a controlled atmosphere glove box. The pulse-reverse electro deposition process consisted of a cathodic pulse at − 0.62 V and an anodic pulse at 0.75 V Vs Zn 2+/Zn. Stoichiometry growth of crystalline ZnTe nanowires was observed in the as-deposited condition. The anodic pulse cycle of the pulse-reverse electrodeposition process presumably introduced zinc vacancies as deep level acceptors at an energy level of E v + 0.47 eV. The resultant ZnTe nanowires showed p-type semiconductivity with a resistivity of 7.8 × 10 4 Ω cm and a charge carrier density of 1.67 × 10 14 cm − 3 . Annihilation of the defects occurred upon thermal annealing that resulted in marginal decrease in the defect density.

Magnetic properties of pulse-reverse electrodeposited nanocrystalline NiFe/Cu composite wires in relation to the anodic current

Ni80Fe20/Cu composite wires were developed using the pulse-reverse electrodeposition technique with the cathodic (positive) current Ic fixed at 1 mA and the anodic (negative) current IA varied from 10 to 90% of Ic. The relationship between the magnetic properties of pulse reverse electrodeposited nanocrystalline NiFe/Cu composite wires and the anodic current was investigated. The results showed that the smaller the magnitude of the anodic current, the smaller was the average nanocrystalline grain size of the deposited material and the better was the uniformity of the surface, and consequently, the better the magnetic properties.

Electrodeposition of highly uniform magnetic nanoparticle arrays in ordered alumite

We report the fabrication of nanometer scale ordered arrays of magnetic cylindrical nanoparticles with low aspect ratio (height/radius a=0.2–7) and ultrahigh uniformity. Anodization and electrochemical deposition are employed for template synthesis and metal particle growth, respectively. Particle uniformity is achieved by an electrodeposition scheme, utilizing pulse reverse voltage wave forms to control nucleation and growth of the particles. The resulting nanoparticles are polycrystalline and grains are randomly oriented. The magnetic properties of the array are dominated by particle shape and by interparticle magnetostatic interactions. A very clear transition of the anisotropy from perpendicular to in plane is observed at an aspect ratio a of about two. The arrays exhibit good thermal stability, demonstrating a great potential of these structures as future recording media in a patterned scheme. The pulse reverse electrodeposition technique shows great promise for the synthesis of nanostructures of various nature.

Crystallite growth of nanocrystalline transition metals studied in situ by high temperature synchrotron X-ray diffraction

The thermal stability of nanocrystalline iron; Palladium and oxygen-doped nickel was investigated in situ by synchrotron X-ray diffraction. Synchrotron experiments allow the determination of crystallites up to the μm-range and the high flux of the synchrotron source enables in situ experiments with very high time resolution. For the normal crystallite growth of nanocrystalline iron we found two different growth regimes. At low temperatures (663 < T < 739) the activation energy of the growth rate constant is about 100 kJ/mol whereas 173 kJ/mol can be determined for higher temperatures (T > 739K). Our advanced X-ray technique allows also the detection of a bimodal crystallite size distribution. The crystallite growth of nanocrystalline palladium shows above 628 K an anomalous behaviour. Nanocrystalline nickel can be stabilized by the pulse-reverse electrodeposition technique due to co-deposition of oxygen in the grain boundaries. The effect of nickel oxide on the thermal stability of n-Nickel was studied using samples with oxygen contents between 956 and 6039 wt.-ppm. At 873 K samples with a low oxygen content grow immediately up to the μm-range; Samples with 2000 ppm oxygen can be stabilized at final crystallite sizes of about 100 nm whereas n-nickel with the highest oxygen concentration even after several hours exhibits a constant crystallite size of only 40 nm.