Electroless Method Research Articles

Characterisation of electroless Ni-P and electroless composite coatings Ni-P/Ni-PTFE

The present study is based on the investigation and characterisation of electroless nickel (Ni-P) and composite nickel - PTFE (Ni-P/Ni-PTFE) coatings. The plating bath composition and the technological regime for production of electroless nickel coatings are proposed. An easily controlled, eco-friendly and simple in operating system technology is developed applying electroless method EFTTOM-NICKEL. PTFE particles are added to the plating bath in suspension. The investigation on the possibility to obtain a stable PTFE suspension is implemented. One layer Ni-P coatings and double layer Ni-P/Ni-PTFE coatings are plated on steel samples. The volume percentage (vol. %) of incorporation of PTFE particles is defined depending on the temperature, pH, etc. microhardness, wear resistance tests and dynamic friction coefficient are measured and comparison the results are performed for Ni-P and Ni-P/Ni-PTFE coatings with different vol. % of incorporation of PTFE particles.

Pt nanotube network with high activity for methanol oxidation

Electrocatalysts with high performance, increased stability, and high surface area are essential for the widespread commercialization of fuel cells. Nanostructured materials emerge as potential candidates to meet these targets. We report on the synthesis and characterization of a nanostructured platinum electrocatalyst for methanol oxidation. Using a simple, one-step electroless method, an interconnected platinum nanotube network was prepared. The highly ordered, high-surface-area catalyst exhibited enhanced current density and durability for methanol oxidation. The catalyst shows a peak current density of 1.43 mA cm−2 at 50 mV s−1 and retained 25% of its initial activity after 1 h. The high catalytic activity is a result of increased Pt–OH formation on nanocrystal aggregates at lower potentials.

Abrasion resistance of Ni-B/Si3N4 composite layers produced by electroless method

Purpose: The paper presents the results of investigations of Ni-B/Si3N4 composite layers produced on steel substrate by electroless method. Design/methodology/approach: Amorphous silicon nitride powder (Si3N4) with nanometric particle sizes was used as a dispersion phase for the production of composite layers. Ni-B/Si3N4 composite layers were produced in baths of varying Si3N4 powder content. For comparative purposes, the study also includes results related to a Ni-B layer. The Si3N4 powder and the structure of the produced layers were characterized. The topography and morphology of the surface of the produced layers are presented. The adhesion of the layers to the substrate material was determined. Microhardness and tribological properties of test materials were determined. Findings: The results of the studies show that Ni-B/Si3N4 composite layers and Ni-B composite layers are characterized by compact structures and good adhesion to the substrate material. The incorporation of Si3N4 particles into the Ni-B layers increases the degree of surface development of the layers. The Ni-B/Si3N4 composite layer material exhibits less microhardness and less abrasive wear compared to Ni-B layers. However, the extent of wear damage of the Ni-B/Si3N4 is relatively small comparing to Ni-B layers.

Corrosion properties of Ni-B/Al203 composites layers produced by electroless method

Corrosion properties of Ni-B/Al203 composites layers produced by electroless method

Corrosion properties of Ni-B/Al2O3 composites layers produced by electroless method

Corrosion properties of Ni-B/Al2O3 composites layers produced by electroless method

The influence of acid etching on the electrochemical supercapacitive properties of Ni[sbnd]P coatings

Amorphous NiP coatings were deposited onto Ti substrates using the electroless method and subsequently etched with nitric acid at different concentrations. Such coatings were employed as a potential electrode for a supercapacitor, with the results indicating that these electrodes exhibited high specific capacitance by controlling the etching conditions, including acid concentration and etching time. Dealloying by acid etching can significantly improve the supercapacitive performance of NiP coatings. The specific capacitance increased 40-fold and achieved levels as high as 865Fg−1 at 10mVs−1 and 1254Fg−1 at 1Ag−1. This is mainly ascribed to the formation of porous structures and thus an increase of surface area due to Ni dissolving in acid solution. According to impedance analysis, the etching step can decrease the charge transfer resistance and Warburg impedance, thus improving the pseudocapacitive property. Moreover, the etched NiP coatings exhibit good cycling performance, and there is no noticeable specific capacitance decrement observed after 500CV cycles at a scan rate of 10mVs−1. Specifically, such electrodes also have low reflectivity, as low as 0.4%.

Palladium nanoparticle and decorated carbon nanotube for electrochemical hydrogen storage

This study proposes a multicomponent system for hydrogen storage. An electrochemical evaluation was used as a simple and accurate technique to assess the storage capacity. A porous silicon substrate was fabricated using an electrochemical anodization process and decorated with palladium nanoparticles using the electroless method. The hybrid substrate underwent chemical vapor deposition for 45 min. Since the deposited palladium nanoparticles could act as potential catalysts, carbon nanotubes grew properly over hybrid structure. The final sample was obtained through post-treatment by palladium nanoparticles using the same electroless method. This triplet sample was characterized using field emission scanning electron microscopy and X-ray diffraction. Galvanostatic charge/discharge experiments were used to conduct electrochemical evaluations of proposed electrode. A maximum hydrogen storage capacity of 537 mAh/g (∼2.05 wt.%) was achieved for the triple-structure sample. The measurements demonstrate that the storage capacity of the triple-structure sample was reduced by a factor of 0.05% after 100 cycles. Although the obtained storage capacity is far from DOE targets, optimized structures based on the proposed electrode may be further developed as an efficient storage system.

PL investigations of spin coated thin films of porous SiC powder embedded in PVA

Abstract Spin coated thin films of pure Poly Vinyl Alcohol (PVA) and PVA mixed with porous SiC microparticles were prepared in order to be used in an optical device. An electroless method was used for producing porous silicon carbide powder under UV irradiation was investigated. The electroless process was chosen because it does not require electrical contact during etching like in anodic one. Silver nanolayer coated SiC particles was formed by polyol process prior the etching and served both as an anode, catalyst and mask for the reduction of a chemical oxidant. The etchant was composed of HF and different oxidants in water. Various porous morphologies are presented and studied as a function of etchant concentration, oxidant type, etching time, and wavelength of irradiation. Morphological, optical and photoluminescence characterizations of SiC micropowder embedded in PVA matrix and deposited as thin films on glass substrates are reported. We concluded that the chemical etching conditions of SiC powder seems to have a large impact on the resulting properties. We noticed that thin film based on SiC powder etched under UV light of 254 nm using K 2 S 2 O 8 as oxidant, at reaction temperature of 80 °C for t = 40min exhibited the best photoluminescence property.

Effect of Operating Temperature on Tribological Behavior of As-Plated Ni-B Coating Deposited by Electroless Method

ABSTRACTThe present work investigates the tribological behavior of electroless Ni-B coating in its as-plated condition at elevated operating temperatures. Ni-B coating is deposited using an electroless method on AISI 1040 steel specimens. Coating characterization is done using scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction techniques. Vicker's microhardness and surface roughness are measured. Friction and wear tests are carried out on a pin-on-disc tribological test setup at room and elevated temperatures of 100, 300, and 500°C. The tribological behavior deteriorates at 100°C compared to room temperature. Electroless Ni-B coating shows excellent wear resistance at 300°C, which again degrades at 500°C due to severe oxidation and softening of the deposits. The worn surface of the coatings is analyzed using optical microscopy and scanning electron microscopy. Within the temperature range considered, the wear mechanism changes from adhesion to a combination of adhesion and abrasion as the temperature rises from ambient condition to 100°C, following which the wear mechanism is predominantly abrasive. The formation of a tribochemical oxide film also affects the tribological behavior of the coatings at high temperature.

Obtaining of the Ni-P Coatings on Steel Strips

The Ni-P coatings on steel strips were obtained by electroless method. Experiments were performed at three pHs, respectively: 6.6; 5.11 and 4.32 with immersion times 5 and 12 minutes at 80 - 85°C. Deposits were caractherized by energy-dispersive analysis (EDS), scanning electron microscopy (SEM) and optical microscopy. The chemical composition shows an increased of phosphorus content at the pH descrease, so at the pH-6.6 the phosphorus content in the coating is 4.74 wt% and at pH-4.32 is 12.42 wt% P. Regardless of the pH value is observed was some chemical dishomogeneity of layers the more pronounced with as the pH value is higher. Alongside Ni and P the layers can contain small amounts of oxygen and other elements coming from the nickel bath impurities and from working environment. Also it shows the surface morphology in correlation with the deposition process parameters and surface defects possible.

A study on EMI shielding enhancement behaviors of Ni-plated CFs-reinforced polymer matrix composites by post heat treatment

In order to develop the high quality electromagnetic interference shielding efficiency (EMI-SE) materials, Ni-plated carbon fiber fabrics (Ni-CFFs) were prepared by an electroless method. Effects of post heat-treatment conditions on EMI-SE and electrical conductivity of Ni-CFFs/epoxy composites were also investigated. The morphologies and structural properties of Ni-CFFs were measured by a SEM and a XRD. It was found that all the Ni peaks increased with increasing post-heat treatment temperature, indicating that some impurities were removed and nickel particle sharp crystalline peaks. Also, It was found that the EMI-SE of composites enhanced was increased after post heat-treatment. In the frequency range of electromagnetic wave occurred from appliances (3.0×107–6.0×108), EMI-SE of post-heat treatment Ni-CFs was increased. This result concludes that the EMI-SE of the composites can be enhanced according to the microstructure of Ni in the Ni-CFFs/epoxy composites.

Elaboration and characterization of luminescent porous SiC microparticles/poly vinyl alcohol thin films

In this study, Morphological, optical and photoluminescence characterizations of nanostructured SiC micropowder embedded in PVA matrix and deposited as thin films on glass substrates are reported. we prepared the porous SiC microparticles/PVA thin films by spin coating method. The average size of SiC microparticles were 7 μm. An electroless method was used for producing porous silicon carbide powder under UV irradiation. Silver nanoparticles coated SiC powder was formed by polyol process. The etchant was composed of aqueous HF and different oxidants. Various porous morphologies were obtained and studied as a function of oxidant type, etching time, and wavelength of irradiation. We concluded that the chemical etching conditions of SiC powder seems to have a large impact on the resulting properties. We noticed that the best photoluminescence property was achieved when SiC powder was etched in HF/K2S2O8 at reaction temperature of 80 °C for t = 40min and under UV light of 254 nm.

Thermo-physical characteristics of nickel-coated aluminum powder as a function of particle size and oxidant

Aluminum particles 15–25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size(15–25 μm, 74–105 μm, and 2.38 mm) and oxidizer(air, CO2, and argon), the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

Wear behavior of electroless Ni-P-W coating under lubricated condition - a Taguchi based approach

The present study aims to investigate the tribological behavior of electroless Ni-P-W coating under engine oil lubricated condition to ascertain its suitability in automotive applications. Coating is deposited onto mild steel specimens by the electroless method. The experiments are carried out on a pin - on - disc type tribo tester under lubrication. Three tribotesting parameters namely the applied normal load, sliding speed and sliding duration are varied at their three levels and their effects on the wear depth of the deposits are studied. The experiments are carried out based on the combinations available in Taguchi's L27 orthogonal array (OA). Optimization of the tribo-testing parameters is carried out using Taguchi's S/N ratio method to minimize the wear depth. Analysis of variance carried out at a confidence level of 99% indicates that the sliding speed is the most significant parameter in controlling the wear behavior of the deposits. Coating characterization is done using scanning electron microscope, energy dispersive X-ray analysis and X-ray diffraction techniques. It is seen that the wear mechanism under lubricated condition is abrasive in nature.

The Effect of Low-Temperature Annealing on a CdZnTe Detector

It is known that low temperature annealing at below 200 °C decreases the leakage current in a CdTe and CdZnTe (CZT) detector. However, only CZT detectors which have electrodes made by electroless method and low temperature annealing in the air showed diminished leakage current after annealing. With the aid of an in-situ annealing monitoring system, we measured the leakage current of a CZT detector while carrying out low-temperature annealing. A decrease in the leakage current resulted from the presence of thin insulating Te oxide layers, TeO2 and CdTeO3, instead of CZT/electrode interface enhancement by diffusion of Au. Other measurement results of Auger electron spectroscopy, micro TEM analysis, and pulse height spectrum were in good agreement with our new interpretation of the low temperature annealing effects of CZT.

Corrosion and wear properties of Ni-Sn-P ternary deposits on mild steel via electroless method

The rising necessity to improve corrosion and wear resistance of metals for engineering applications cannot be over emphasized. This has led to employing diverse models, method and techniques to obtain better corrosion and wear resistances for metallic materials and components which will otherwise fail during service. This work investigated the effect of Ni-P binary and Ni-Sn-P ternary electroless depositions on the corrosion and wear behavior of mild steel. Micro-structural examination using scanning electron microscopy (SEM) analysis shows finer and more evenly distributed particle orientation across the substrate surface. The Ni-Sn-P ternary deposits on the mild steel displayed from the linear polarization analysis a better corrosion resistance with corrosion rate values of 0.000246mm/yr as compared with that of the Ni-P binary deposits with 0.016672mm/yr. Also the coefficient of friction of the unplated sample varies between 0 and 0.08 while for the plated samples the coefficient of friction was relatively lesser and ranged from 0 to 0.02. Significant improvement in corrosion resistance was also indicated by a positive shift in potential. Sliding wear analysis demonstrates consistently enhanced wear resistance of the ternary deposits as well as the binary deposits, with the ternary Sn addition showing better resistance to wear. This work has established that Ni-Sn-P electroless coating of mild steel can be used to improve the corrosion and wear resistance for engineering applications.

Electrochemical hydrogen storage in Pd-coated porous silicon/graphene oxide

In this study, P-type single crystal silicon (Si) was used to make porous silicon (PS) using an anodization cell. The prepared PS samples were first coated with Pd nanoparticles by electroless method (Pd/PS); then, graphene oxide (GO) sol was spin coated on them. Pd/PS coated with GO (GO-Pd/PS/Si) characterization has been carried out using field emission scanning electron microscopy (FESEM), Raman spectroscopy and X-ray diffraction (XRD). Electrochemical characterization and hydrogen storage were studied for all electrodes (Si, PS, Pd/PS and GO-Pd/PS/Si) by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS), respectively. The highest hydrogen storage capacity was obtained for GO-Pd/PS/Si, which was 546.1 mAh g−1 equal to 2.1 wt% hydrogen. The results indicate that the storage capacity of the GO-Pd/PS/Si electrode decreases only 1% of initial capacitance, after 100 cycles. Also, the EIS studies show that GO-Pd/PS/Si electrode performs electrochemically better than other electrodes. Considerable hydrogen storage in GO-Pd/PS/Si shows that this newly synthesized material could be a good candidate to be used in mobile hydrogen storage applications.

Effect of rapid magnetic field annealing in vacuum on the structure and magnetic properties of Ni-P films

ABSTRACTNi-P thin films are deposited on silicon wafer by electroless method and treated by different annealing processes. The structure of as-deposited film exhibits the mixture of amorphous and microcrystalline phases, and the Ms is 150 emu/cc and Hc is 24 Oe. Rapid thermal annealing (RTA) could avoids the impurity and the Ms of the sample reached the maximum value about 413 emu/cc after RTA process at 350°C. A magnetic field about 5000 Oe was applied during RTA process, which resulted in higher crystallization temperature, higher value of Ms and lower value of Hc.

First Integration Steps of Cu-based DNA Nanowires for interconnections

In the wide range of emergent nanotechnologies, DNA-based microelectronics has shown an important potential for components miniaturization and auto-assembling approaches applicable to future silicon-based electronic circuits [1]. In order to pursue the Moore's law, interconnections must be indeed addressed at the nanoscale, with a good control of their size, location and electrical & thermal performances. With its natural auto-assembling property, its 2-nm-double-helix diameter and its several metallization possibilities, DNA is a promising candidate to build bio-inspired electronic components [1]. DNA has been first metallized by Erez Braun in 1998 using a silver electroless method [2]. Since 1998, several groups have worked on DNA metallization using different chemistries with metals such as Pd, Pt, Au, Ag and Cu [3]. Most of these works have presented electrical and morphological characterizations of few metallic nanowires. However, in order to initiate DNA-based-nanowires integration on silicon technologies, we must start to implement nanowires on silicon at wafer scale. We have thus developed a platform based on silicon technologies providing morphological and electrical characterizations of copper nanowires built from DNA [4]. This platform will allow us to simultaneously characterize a large number of nanowires, returning a statistic of their electrical performance, and thus allowing the optimization of the copper nanowire metallization process. Two main approaches are proposed to fabricate and contact a large number of copper nanowires with metallic electrodes in order to study their electrical behavior. In both approaches, a linear 16-μm-length DNA phage is used. The first approach consists in aligning DNA wires on a hydrophobic silicon oxide surface by a method called DNA combing. On a second time, aligned DNA wires are all metallized by electroless process [4]. 5-nm-diameter copper nanowires have been so far achieved by this method and focus on improving the metallization process is currently at stake. Finally, Ti/Au electrodes are fabricated on the nanowires by a classical lift-off process in order to electrically connect them. The advantage of this approach is the very accurate nanowires alignment and their homogeneity over the surface. However, the low number of aligned nanowires per surface unit (10–20μm−2) and the high electrical resistance of each (>kohms) makes the electrical characterization quite complex. On the other side, the second approach consists in fabricating the Ti/Au electrodes first and then aligning or randomly depositing the copper nanowires at their surface. Same protocols are used to align and metallize the DNA nanowires for both approaches. The advantage of this second approach is a higher nanowire density deposited on the electrodes. However, a higher contact resistance and a lower control of nanowires alignment are obtained. Both approaches are currently explored and permit to explore a wide range of parameters for copper nanowires metallization process improvement.

Fabrication of Oxidation-Resistant Metal Wire Network-Based Transparent Electrodes by a Spray-Roll Coating Process.

Roll and spray coating methods have been employed for the fabrication of highly oxidation resistant transparent and conducting electrodes (TCEs) by a simple solution process using crackle lithography technique. We have spray-coated a crackle paint-based precursor to produce highly interconnected crackle network on PET roll mounted on a roll coater with web speed of 0.6 m/min. Ag TCE with a transmittance of 78% and sheet resistance of ∼20 Ω/□ was derived by spraying Ag precursor ink over the crackle template followed by lift-off and annealing under ambient conditions. The Ag wire mesh was stable toward bending and sonication tests but prone to oxidation in air. When electrolessly coated with Pd, its robustness toward harsh oxidation conditions was enhanced. A low-cost transparent electrode has also been realized by using only small amounts of Ag as seed layer and growing Cu wire mesh by electroless method. Thus, made Ag/Cu meshes are found to be highly stable for more than a year even under ambient atmosphere.