Microstructure and corrosion behavior of electroless deposited Ni-P/CeO_2 coating

Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy （SEM） and X-ray diffraction （XRD） spectrometer were used to examine surface morphology and structure of the as-plated coating. Differential scanning calorimeter （DSC） and transmission electronic microscopy （TEM） were used to study the coating＇s phase change at high temperature. The coating＇s corrosive behavior in 3%NaCl ＋ 5%H2SO4 solution was also investigated. The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals, while the Ni-P/CeO2 coating had perfect amorphous structure. In high-temperature condition, Ni3P precipitation and Ni crystallization took place in both coatings but at different temperatures, while the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels. The anti-corrosion property was better in the CeO2-containing coating, and this was due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart. Ni-P/CeO2 coating＇s pure amorphous structure was the result of Ni＇s hindered crystal-typed deposition and P＇s promoted deposition.

XPS Studies on Electroless As-Deposited and Annealed Ni-P Films

Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiation detectors. By keeping deposition time, temperature, pH and concentration of the precursor solution constant, the film deposition has been done. XPS studies were done to analyze the composition and stoichiometry of Ni-P thin films.

An in situ measure method to study deposition mechanism of electroless Ni-P plating on AZ31 magnesium alloy

An in situ method was designed to measure a continuous open circuit potential （OCP） curve of AZ31 magnesium alloy and to observe the morphology variation of Ni-P coating during the process of the electroless plating. The deposition mechanism of the electroless Ni-P plating on AZ31 Mg alloy was studied by OCP curve, scanning electron microscopy （SEM）, and energy dispersion spectroscopy （EDS）. The process of electroless Ni-P plating contains the coating formation stage and the coating growth stage. The formation stage includes three procedures, i.e., the nucleation and growth of Ni crystallites, the extension of the coating in two-dimensional （2D） direction and the coalescence of the coating along three-dimensional （3D） direction. SEM investigations demonstrate that the spherical nodules of the Ni-P coating are not only formed during the coating growth stage, but also generated in the initial deposition stage of electroless Ni-P plating. The variation of the coating rates at different deposition stages corresponds to the deposition mechanism of their respective deposition stage.

Effect of novel ternary ligand system on acidic electroless Ni-P plating on AZ91D magnesium alloy

The electroless Ni-P coatings on AZ91 D magnesium alloy substrate were prepared using the acidic hypophosphite-reduced electroless nickel bath containing the novel ternary ligand system. The results indicate that the deposition rate varies with the ternary ligand concentration in plating solution. The structural and morphological characteristics of the coatings were analyzed by XRD and SEM. The anticorrosion properties of the Ni-P coatings were evaluated in 3.5% NaCl solution by electrochemical impedance and potentiodynamic polarization methods. The amount of ternary ligands in electroless plating bath has an significant effect on the surface morphology and structure of Ni-P coatings. The decrease of crystallization temperature and increase of crystallization heat of all the deposits with an increase in ternary ligand concentration are found by DSC measurements. The coating obtained with 0.035 mol/L ternary ligand additive in plating bath can offer a better surface homogeneity and improve corrosion resistance.

Growing process and reaction mechanism of electroless Ni-Mo-P film on SiO_2 substrate

The diffusion barrier Ni-Mo-P film for Cu interconnects was prepared on SiO2/Si substrate using electroless method. The surface morphology and composition during the formation process of electroless Ni-Mo-P film were investigated through analyzing samples of different deposition time. Induced nucleation, induced co-deposition, and self-induced growth mechanisms involved in electroless process were confirmed by field-emission scanning electron microscopy （FE-SEM）, energy dispersive spectrometry and atomic force microscopy （AFM）. Firstly, the preceding palladium particles as catalysts induce the nucleation of nickel. Secondly, the nickel particles induce the deposition of molybdenum and phosphorus, which attributes to induced co-deposition. Thirdly, former deposited Ni-Mo-P induces deposition of the latter Ni-Mo-P particles. Moreover, the reaction mechanism was proposed with the oxydate of 3-4PO .

Electroless copper-phosphorus coatings with the addition of silicon carbide (SiC) particles

Cu-P-silicon carbide （SiC） composite coatings were deposited by means of electroless plating.The effects of pH values,temperature,and different concentrations of sodium hypophosphite （NaH2PO2·H2O）,nickel sulfate （NiSO4·6H2O）,sodium citrate （C6H5Na3O7·2H2O） and SiC on the deposition rate and coating compositions were evaluated,and the bath formulation for Cu-P-SiC composite coatings was optimised.The coating compositions were determined using energy-dispersive X-ray analysis （EDX）.The corresponding optimal operating parameters for depositing Cu-P-SiC are as follows：pH 9;temperature,90oC;NaH2PO2·H2O concentration,125 g/L;NiSO4·6H2O concentration,3.125 g/L;SiC concentration,5 g/L;and C6H5Na3O7·2H2O concentration,50 g/L.The surface morphology of the coatings analysed by scanning electron microscopy （SEM） shows that Cu particles are uniformly distributed.The hardness and wear resistance of Cu-P composite coatings are improved with the addition of SiC particles and increase with the increase of SiC content.

Electroless deposition of Cu on multiwalled carbon nanotubes

Copper has been deposited on the surface of multiwailed carbon nanombes （MWNTs） and inside MWNTs by electroless deposition. The as-prepared Cu-MWNT composite materials have been characterized by X-ray diffractometer （XRD）, transmission electron microscopy （TEM）, and electrochemical measurement. XRD analyses showed that Cu was a face-centered cubic （fcc） structure. The average size of Cu was calculated by Scherrer＇s formula from XRD data, and it was 11 nm. TEM revealed that Cu grains on the surface of MWNTs were uniform with the sizes of about 30-60 nm. The electrochemical measurement indicated that Cu-MWNT composite materials possessed fine electron conductivity.

Fabrication of multi-shell coated silicon nanoparticles via in-situ electroless deposition as high performance anodes for lithium ion batteries

Si-based materials have been extensively studied because of their high theoretical capacity,low working potential,and abundant reserves,but serious initial irreversible capacity loss and poor cyclic performance resulting from large volume change of Si during lithiation and delithiation processes restrict their widespread application.Herein,we report the preparation of multi-shell coated Si(DS-Si)nanocomposites by in-situ electroless deposition method using Si granules as the active materials and copper sulfate as Cu sources.The ratio of Si and Cu was readily tuned by varying the concentration of copper sulfate.The multi-shell(Cu@CuxSi/SiO2)coating on Si surface promotes the formation of robust and dense SEI films and the transportation of electron.Thus,the obtained DS-Si composites exhibit an initial coulombic efficiency of 86.2%,a capacity of 1636 mAh g^-1 after 100 discharge-charge cycles at 840 mA g^-1,and an average charge capacity of 1493 mAh g^-1 at 4200 mA g^-1.This study provides a low-cost and large-scale approach to the preparation of nanostructured Si-metal composites anodes with good electrochemical performance for lithium ion batteries.

Study of the Corrosion Resistance of Electroless Ni-P Deposits in a Sodium Chloride Medium

The corrosion resistance of electroless Ni-P deposits with phosphorous contents from 12% to 14% in sodium chloride solutions was studied. The deposits were immersed in 3.5% NaCl solutions for 29 d to obtain the electrochemical parameters and were examined in a standard salt spray test for 15 d respectively. The corrosion resistance of the deposits was studied by poten- tio-dynamic scan, electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and cold-field emission scanning electron microscopy (FE-SEM) equipped with an energy dispersive X-ray detector (EDX). The patterns of XRD and the results of FE-SEM showed that the prepared deposits were amorphous. But after a 15 d standard salt spray test, a few pinholes appeared on the surface of the deposit and the weight content of phosphorus on the surface of the deposit was higher (which was beneficial to the formation of the passivation films) than that before the standard salt spray test when the nickel content was lower because the dissolved weight of nickel was greater than that of phosphorus. The results from potentio-dynamic scan and EIS showed that passivation films formed on the Ni-P deposit after immersion in the NaCl solutions, which decreased the corrosion rate of Ni-P samples. The results of this work show their potential applications in marine corrosion.

EFFECT OF ELECTROLESS DEPOSITION CONDITIONS ON THE STRUCTURES AND THE MAGNETIC PERFORMANCES OF THE Co-Fe-P ALLOY

Electroless Co-Fe-P alloys were deposited from an alkaline bath, containing boric acid as a buffer agent and sodium citrate as a complexing agent. As a result, with the increase of pH of the bath, the iron content of the deposit increased, whereas the cobalt and phosphorus contents decreased. The structure of the deposit was investigated using X-ray diffraction （XRD） and transmission electron microscope （TEM）. The deposit consisted of hexahedron phase Co, cubic phase Fe-Co, and amorphous phase （crystalline）. The magnetic performances of the deposit were studied using vibrating sample magnetometer （VSM）. The more the content of Fe and the less the content of P （the content of Co being less）, the better the magnetic performances of the deposit. The Co-Fe-P deposit was suitable for use as soft magnetic material.

Fabrication of anatase titanium dioxide nanotubes by electroless deposition using polycarbonate for separate casting method

Titanium dioxide nanotubes(TNTs)were prepared by electroless deposition using ion track etched polycarbonate templates.The ion tracks were prepared to the desired diameter of the TNTs outer diameter.Titanium dioxide nanotubes with a diameter of minimum 80 nm having a wall thickness of minimum 10 nm can be fabricated using this method.To achieve nanotubes with thin walls and small surface roughness the tubes were generated by a several steps procedure under aqueous conditions at nearly room temperature.The presented approach will process open end nanotubes with well defined outer diameter and wall thickness.Using this method TNT arrays up to 109 tubes per cm2having a tube length up to 30μm can be produced,single tubes are also possible.The structural properties of the grown TNTs were investigated by using various analytical techniques,i.e.scanning electron microscopy(SEM),energy dispersive X-ray fluoresence spectrometer(EDX),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),Raman spectroscopy and Photoluminescence.

Electroless Ni-P Deposition on Magnesium Alloy from a Sulfate Bath

A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 C. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.

Electroless Plating of Ni-Fe-P Alloy and Corrosion Resistance of the Deposit

Electroless Ni-Fe-P alloys in an alkaline bath were plated. The effects of deposition parameters on the plating rate and the coating composition were examined. The weight loss test and the anodic polarization measurement of the deposits in 3.5 wt pct NaCI solution (pH7.0) showed that the deposits with the mole ratio of NiS04/FeSO4 being 0.07:0.03, pH8.0 and 7.5 possess better corrosion resistance than that of the other deposits and the Ni-Fe-P deposits did not form passive films in this environment. In 5.0 wt pct NaOH solution, the Ni-Fe-P deposits have better corrosion resistance and formed passive films.

Electroless Co-Zn Surface-Modified Nickel Hydroxide as an Active Material for Pasted Nickel Electrodes

Chemically precipitated β type nickel hydroxide powder was surface modified by electroless deposition of Co Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized by scanning electron microscopy (SEM), specific surface area (BET), X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). It has been found that Co and Zn components of the surface electroless coatings exist in the oxidized state. Electrochemical performances of pasted nickel electrodes using the modified nickel hydroxide as an active material were investigated, and compared with those of the electrodes prepared with the unmodified nickel hydroxide. Charge/discharge tests show that the modified nickel hydroxide electrodes exhibit better performances in the charge efficiency, specific discharge capacity and active material utilization. Their resistance to swelling with cycling is also superior to that of the unmodified nickel hydroxide electrodes. Cyclic voltammetric (CV) studies indicate that the modified electrodes have a higher electrochemical activity, and the porous pasted nickel electrodes have some distinguished CV characteristics in comparison with those of the thin film nickel electrodes.

STUDY ON THE REAR CAPACITY OF DEPOSITS USING ELECTROLESS NICKEL DEPOSITION AND ELECTROPLATE CHROMIUM

The comparison study of the relations between the hardness, wear capacity and heat treatment temperature of the electroless nickel deposition with the electroplating deposits of chromium were conducted .The results showed that the hardness and wear capacity of the electroplate technology were superior than that of electroless in general cases, but with the raising of the heat treatment temperature, the hardness and wear capacity of the samples treated by electroless deposition technology were superior obviously than that of electroplate.

Mechanism of Silver Nanoparticles Deposition by Electrolysis and Electroless Methods on a Graphite Substrate

This study shows a silver electrodeposition model (EDM) on a graphite substrate. The electrolyte was a 0.01 M solution of pure silver and chromium nitrate using an electrolyzing cell. EDC with current density up to 20 mA/cm2 and 15 mV and pulse current were studied. Results revealed that silver deposited at a rate of 0.515 mg/cm2/min with 12 mA/cm2 that decreases to 0.21 and 0.16 mg/cm2·min with the decrease of current density to 6 and 5 mA/cm2 respectively. The model postulates that silver ions (a) were first hydrated before diffusing (b) from the solution bulk to the cathode vicinity, The next step (c) involved the chemical adsorption of these ions on certain accessible sites of the graphite substrate (anode), The discharged entities (d) adhere to the graphite surface by Van der Vales force. Silver ions are deposited because the discharge potential of silver is low (0.38 mV) as compared to other metal ions like chromium (0.82 mV). Pulse current controls silver deposition due to flexibility in controlling steps (a)-(c) of the deposition mechanisms. Parameters like current density, current on-time, current-off time, duty cycle (ratio of current on time and total pulse time) and pulse frequency influenced the shape and size of the deposits. Step (b) suggested that silver particles were deposited in a monolayer thickness. The silver layer turned multiple after fully satisfying the accessible sites with the monolayer. The activation energy ΔE value amounts to 86.32 kJ/mol/K. At high temperature and current density, homogeneous diffusion occurs.

Investigation on Quick Surface Metallization of Nano Titania Powder

Quick surface metallization of titania powder was carried out by electrolesschemical deposition of nickel. The fabricated product was characterized by XRD, SEM, FTIR andcross-section metallography. The analysis results show that titania particles are completely coatedby a thin nickel shell about 600 nm thick composed of nano-sized crystalline nickel particles.Mechanism of nickel chemical deposition on nano powder is proposed.

Structural characterization and corrosive property of Ni-P/CeO_2 composite coating

Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart.Scanning electronic microscopy（SEM）, transmission electronic microscopy（TEM）, X-ray diffraction spectrometer（XRD）, and differential scanning calorimeter（DSC） were used to examine surface morphology and microstructure of the coating.Corrosive investigation was carried out in 3%NaCl＋5%H2SO4 solution.The results showed that Ni-P coating had partial amorphous structure mixed with nanocrystals, whereas the Ni-P/CeO2 coating had perfect amorphous structure.In high temperature condition, Ni3P precipitation and Ni crystallization occurred in both coatings but at different temperatures, whereas the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels.The anticorrosion property and passivity were improved in the CeO2-containing coating due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart.During the co-deposition process, some Cen＋（n=3, 4） ions may be adsorbed to the metal/solution interface, hinder nickel＇s crystal-typed deposition and promote phosphorous deposition.The nano-CeO2 doping finally resulted in the coating＇ perfect amorphous structure and good anti-corrosive property.

Mixed Phase Anatase/rutile Titanium Dioxide Nanotubes for Enhanced Photocatalytic Degradation of Methylene-blue

Titanium dioxide Nanotubes(TNTs) prepared by electroless deposition have been annealed at air ambient and low temperature. As a result, the anatase/rutile phase composition of the TNTs can be tailored to the needs of later applications. Nanotubes with anatase/rutile mixed phase ratio of 4:1 have been produced in this report and further examined for their photocatalytical behavior. The photocatalytical properties of the TNTs have been observed by degradation of methylene-blue in aqueous solution under low power UV-light irradiation. The results shown in this report are based on the synergetic effect between rutile and anatase,which results in the mixed phase TiO 2 nanotubes having enhanced photocatalytical properties.

Magnetoelectric effect in layered composites with arc shape

Magnetoelectric （ME） layered Ni/PZT/Ni composites with arc shape have been prepared by using electroless deposition. The ME effect is measured by applying both constant and alternating magnetic fields in longitudinal and transverse directions. The longitudinal ME voltage coefficient is much larger than the transverse one. With the increase of arc length or decrease of curvature, the resonance frequency of layered arc Ni/PZT/Ni composites gradually decreases, while the maximum of the ME voltage coefficient of the composites increases monotonously. The influence of the arc length and the curvature on ME coupling is discussed. The flat interface between the ferromagnetic and the piezoelectric phases in layered ME composites is believed to provide large ME voltage coefficient.