Electroless Method Research Articles

Surface morphology and structure of Ni–P, Ni–P–ZrO 2, Ni–W–P, Ni–W–P–ZrO 2 coatings deposited by electroless method

Electroless binary Ni–P and ternary Ni–W–P alloy coatings and electroless composite (Ni–P–ZrO 2 and Ni–P–W–ZrO 2) nickel coatings were deposited. Baths with aminoacetic acid as the complexing agent were used. ICP measurements showed that the P content depending on the type of coating is in a range of 4.7–6.3 wt.% (at pH = 6, t = 75 °C). The tungsten content is around 1–2 wt.%. SEM examinations show that the electroless Ni–P coating has the most fine-grained structure. Grains in the form of microspheroids 20 μm in size are characteristic of the Ni–P–ZrO 2 coating. X-ray diffraction patterns show that for all the obtained coatings peak Ni(111) located around 2 θ = 44° is the most intensive. After the coatings are heat treated at 400 °C for 1 h the peak becomes even sharper. The heat treatment results in a nearly double increase in crystallite size. The quaternary coatings' abrasion resistance is determined by the second-phase (ZrO 2) particles present in them.

Chemically deposited electrochromic cuprous oxide films for solar light modulation

Thin cuprous oxide electrochromic films on the transparent conductive electrodes were prepared by chemical electroless method. The films cycled in K +-based electrolyte revealed typical red-ox peaks with higher intensity compared to those in the Li + and the Na +-based electrolytes. The durability of the cuprous oxide due to cycling into LiClO 4 was about 60 cycles. The thermal treatment of the films invoked decrease in red-ox peak intensity, and thus deterioration in the electrochromic properties. The response time of the coloration and bleaching to an abrupt voltage change from −4.5 to +4.5 V and reverse was found to be in the range of about 10 s. The maximum light intensity modulation ability of the films, as the AM1.5 spectrum is taken for an input, was calculated to be about 65%.

Electrochromism of the electroless deposited cuprous oxide films

Thin cuprous oxide films were prepared by a low cost, chemical deposition (electroless) method onto glass substrates pre-coated with fluorine doped tin oxide. The X-ray diffraction pattern confirmed the Cu 2O composition of the films. Visible transmittance spectra of the cuprous oxide films were studied for the as-prepared, colored and bleached films. The cyclic voltammetry study showed that those films exhibited cathode coloring electrochromism, i.e. the films showed change of color from yellowish to black upon application of an electric field. The transmittance across the films for laser light of 670 nm was found to change due to the voltage change for about 50%. The coloration memory of those films was also studied during 6 h, ex-situ. The coloration efficiency at 670 nm was calculated to be 37 cm 2/C.

Transparent-conducting, gas-sensing nanostructures (nanotubes, nanowires, and thin films) of titanium oxide synthesized at near-ambient conditions

A template-based, electroless wet-chemical method for synthesis of nanotubes and nanowires of nanocrystalline anatase titanium oxide (titania) at 45 °C is reported. Single-nanowire electrical property measurements reveal low dc resistivities (7–21 × 10−4 Ω cm) in these titania nanowires. In the presence of 1000 parts per million of CO gas at 100 °C, the resistivity is found to increase reversibly, indicating low-temperature gas-sensing capability in these titania nanowires. Thin films of nanocrystalline anatase titania, deposited using a similar wet-chemical method, also have low room-temperature dc resistivities (6–8 × 10−3 Ω cm), and they are transparent to visible light. Nanostructure-properties relations, together with possible electrical conduction, optical absorption, and gas-sensing mechanisms, are discussed. The ability to fashion transparent-conducting and gas-sensing nanocrystalline anatase titania into nanotubes/nanowires and thin films at near-ambient conditions could open a wider field of applications for titania, including nanoelectronics, chemical sensing, solar cells, large-area windows and displays, invisible security circuits, and incorporation of biomolecules and temperature-sensitive moieties.

Novel Silica Based Coatings as a Substitute for Chrome Passivates

A novel electroless method was developed to deposit corrosion resistant silica coatings. Process parameters such as bath temperature, concentration of sodium silicate and sodium borohydride were optimized based on the uniformity and corrosion resistance of the final deposit obtained. Accelerated corrosion tests as per ASTM B117 standards show corrosion performance comparable to that of chrome passivates.

Development of an Electroless Method to Deposit Corrosion-Resistant Silicate Layers on Metallic Substrates

A novel electroless method for depositing corrosion-resistant silicate layers on metallic substrates from aqueous solutions has been developed. The silicate layer was deposited from an aqueous solution of sodium silicate (3.22 weight ratio sodium silicate, 37.5% solution in water from PQ Corporation) and sodium borohydride. The technique is demonstrated by forming a passive film on galvanized steel. Deposition parameters such as concentration of the bath, temperature, and pH have been optimized based on the corrosion characteristics of the final coating. Studies on the coating reveal the formation of a very thin zinc disilicate layer followed by a much thicker silica layer. Accelerated corrosion tests showed that the silicate coatings have higher corrosion resistance and better stability when compared to chrome passivates. Silica coatings developed by this method show promise as an alternative to chrome passivation for corrosion protection.

The effect of temperature on the preparation of electrochromic nickel oxide by an electroless method

The advantages of nickel oxide as an electrochromic material are due to its good contrast of transmittance and its suitable use as a secondary electrochrome. Compared to other methods of depositing eletrochromic nickel oxide, coating nickel oxide by electroless is simple and easy to scale-up for industrial application. This study presents the preparation of nickel oxide film on an ITO substrate by an electroless method and oxidizing it with heat treatment. The influence of oxidizing temperature in heat treatment procedures is notable. The morphology of the film was analyzed by a scanning electron microscope (SEM) and X-ray diffraction (XRD). Heat temperature at 380°C obtained optimal of electrochromic properties. The transmittance difference (ΔT) of the film at 630nm was maintained at 69%, and the amount of transferred charge during cyclic voltammetry was approximately 0.8mC/cm2 after 1000 cycles of redox, which was operated between −1.5 and +1.5V potential step. The degradation of the film was decreased by increasing the oxidizing temperature. The evidences showed electrochromic abilities of nickel oxide were affected by heat-treatment procedures. All these analyses provided a novel method for preparing the electrochromic nickel oxide in a low-cost way.

The electrochromic properties of nickel oxide by chemical deposition and oxidization

The advantages of nickel oxide as an electrochromic material are its good contrast of transmittance and its suitable use as a secondary electrochromic film with WO 3 for electrochromic devices. Electrochromic nickel oxide prepared by chemical processes which include deposited nickel film by electroless (or chemical deposition) method and then oxidized by H 2O 2. Compared with other methods, deposited nickel oxide by chemical deposition is simple and easy to scale-up for industrial application. The morphologies of the films were examined by scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD). The optical density change (ΔOD) of the films at 630 nm was 0.42, which was operated between − 1.5 and + 1.5 V of potential step after 100-cycle switching. The response time for coloring and bleaching were 1.7 s and 3.3 s, respectively. The life cycles of electrochromic characteristics was recorded by using the cyclic voltammetry (CV). The superficial current density of oxidation remaining was up to 0.002 A/cm 2 after 5000 cycles.

Microstructure and mechanical properties of Al 2O 3–TiC–4vol.%Co composites prepared from cobalt coated powders

Al 2O 3–TiC–4vol.%Co composite was fabricated by hot pressing cobalt-coated Al 2O 3 and TiC powders. A chemical electroless method for cobalt deposition on the surface of ceramic powders was used. Microstructure and mechanical properties of the Al 2O 3–TiC–4vol.%Co composite were compared with that of conventional Al 2O 3–TiC composite. Cobalt phase was uniformly dispersed in the matrix, especially along the interfaces between Al 2O 3 and TiC grains, which inhibited the grain growth of the matrix. The fracture mode changed from intergranular to a mixture of intergranular and transgranular type. Overall improvement in fracture toughness (7.8 ± 0.8 Mpa m 1/2) and bending strength (782 ± 60 Mpa) was obtained in the composite, which should be attributed to the improved crack bridging and crack deflection after interfacial modification. And no obvious decrease in hardness was found in the Al 2O 3–TiC–4vol.%Co composite. The sinterability, homogeneity and fracture behavior appear to be significantly improved due to the application of cobalt coated powders.

Electroless method for Bi 2Te 3 film deposition

This work reports the feasibility of thermoelectric thin films synthesis via a new aqueous chemical deposition process. Bismuth telluride thin films have been prepared using this method. A bath containing the dissolved precursors in acidic solution was used. The reaction generated between the bismuth and the tellurite ions on an electrodeposited Ni° on stainless steel substrate gave Bi 2Te 3 thin films. The reaction took place at ambient temperatures with stirring with different ratios of [Bi III]/[Te IV] ions. The tellurite ion concentration was fixed to 5.10 −3 mol/l in HNO 3 1 mol/l. The films formed were bright and adhesive to the substrate. It was shown that the composition of the deposited film is influenced by the composition of the chemical bath. The products characterized by X-ray diffraction were polycrystalline; the morphology of the film examined by scanning electron microscopy showed a compact structure. The thickness of the film determined by observation of the section by electronic microscopy was about 4 μm thickness.

Electrochemical characteristics of dopamine oxidation at palladium hexacyanoferrate film, electroless plated on aluminum electrode

A novel electrode material was obtained at an aluminum electrode (Al) by a simple electroless method including two consecutive procedures: (i) the electroless deposition of metallic palladium on the Al electrode surface from PdCl 2 + 25% ammonia solution and (ii) the chemical transformation of deposited palladium to the palladium hexacyanoferrate (PdHCF) films in a solution containing 0.5 M K 3[Fe(CN) 6]. The modified Al electrode demonstrated a well-behaved redox couple due to the redox reaction of the PdHCF film. The PdHCF film showed an excellent electrocatalytic activity toward the oxidation of dopamine (DA). The effect of solution pH on the voltammetric response of DA has been investigated. A linear calibration graph was obtained over the DA concentration range 2–51 mM. The rate constant k and transfer coefficient α for the catalytic reaction and the diffusion coefficient of DA in the solution D, were found to be 4.67 × 10 2 M −1 s −1, 0.63 and 2.5 × 10 −6 cm 2 s −1, respectively. The interference of ascorbic acid was investigated and greatly reduced using a thin film of Nafion on the modified electrode. The modified electrode indicated reproducible behavior and a high level stability during electrochemical experiments, making it particularly suitable for the analytical purposes.

Studies on the influence of double-layer electroless metal deposition on the electromagnetic interference shielding effectiveness of carbon fiber/ABS composites

Electromagnetic interference (EMI) shielding effectiveness (SE) of single-layer or double-layers electroless metals, such as nickel/phosphorus–pure nickel (NiP–Ni), Ni–NiP, NiP–Cu, Ni–Cu, coated carbon fiber reinforced acrylonitrile-butadiene-styrene (ABS) composites was investigated. The resistivity and anti-oxidization of conductive fillers were important factors for EMI shielding composites. Although the resistivity of electroless copper-coated carbon fiber (ECCF) is much lower than that of electroless nickel-coated carbon fiber (ENCF), electroless copper films on the carbon fibers are readily oxidized during compounding processes. The resistivity of ECCF/ABS composites increased significantly after composite fabrication. As a result, the EMI SE of ECCF/ABS composite showed a poor EMI SE (37 dBm) among those electroless metals-coated carbon fiber reinforced ABS composites. The coated double layers electroless metals on the conductive fillers were obtained by electroless method. The outside metal layer, which possessed better anti-oxidization, provided suitable protection for the conductive fillers. Thus, the EMI SE of the ECCF/ABS composite can improve effectively. The best EMI SE of double-layers electroless coated-metals/ABS composites could be reached 65 dBm.

The electroless deposition of nickel on SiC particles for aluminum matrix composites

Nickel coatings have been deposited by an electroless method on SiC powder particles. Three different SiC powder grades, in terms of average particle size, were chosen, i.e. 8, 14 and 70 μm. The coating process was performed in few steps consisting of the SiC powder cleaning by acetone, its sensitization by HCl aqueous solution containing Sn 2+, followed by its activation by HCl aqueous solution containing Pd 2+, and finally—hydrometallurgical nickel deposition using aqueous solution containing Ni 2+, as a nickel carrier. The influence of the deposition conditions on the coating layer properties was studied. The thickness, morphology and microstructure of the layers were controlled by the growth conditions. SEM and digital image analyzing techniques were used for those purposes. Since the Ni-coated SiC powders were produced as reinforcement for Al matrix composites, their compatibility as compared with the uncoated SiC powders was also controlled by metallography.

Deposition features of Ni on self-assembled microtubule template from biolipid by electroless method

Diacetylenic glycero-phosphatidylcholine is a chiral molecule with amphiphilic property, and it can self-assembly into a lipid microtubular structure. The lipid microtubule is a stable structure formed by tightly wound helical ribbons, and the ribbon-wrapping patterns have a significant effect on their chemical deposition on the microtubules. The deposition of colloidal Pd catalyst occurs mainly on the helical edge of the wound helical ribbons to form helical deposition lines of colloidal Pd particles in the interior and exterior of the lipid microtubules, resulting in an uneven chemical deposition of Ni on the microtubules. Catalyzed by as-deposited colloidal Pd, metallized Ni microtubules are characterized by a helical form, which may be in relation to inner stress due to the thickness difference or the different deposition processes. The observation of microtom shows that metallized tubules have a hollow structure. Some metallized tubules have a kind of coaxial double layer structure observed in the direct experiment evidence, indicating that metallization can occur in the inner and outer surface of the lipid tubules. Both lipid microtubules and metallized microtubules can be used as vehicles for encapsulating biological active molecules to control their release and to develop micro-components in biological and mechanical systems.

Structural and spectroscopic characterization of porous silicon carbide formed by Pt-assisted electroless chemical etching

A novel electroless method of producing porous silicon carbide (PSiC) is presented. Unlike anodic methods of producing PSiC, the electroless process does not require electrical contact during etching. Rather, platinum metal deposited on the wafer before etching serves as a catalyst for the reduction of a chemical oxidant, which combined with UV illumination injects holes into the valence band, the holes subsequently participating in the oxidation and dissolution of the substrate. The etchant is composed of HF and K 2S 2O 8 in water. Various porous morphologies are presented as a function of etchant concentration, time of etching, and SiC polytype. Wafer quality is of the utmost concern when utilizing the electroless wet etchant, since defects such as stacking faults, dislocations, and micropipes have a large impact on the resulting porous structure. Results of imaging and spectroscopic characterization indicate that the porous morphologies produced in this manner should be useful in producing sensors and porous substrates for overgrowth of low dislocation density epitaxial material.

Description of Al2O3 powders coated by Ni–P particles obtained through an electroless chemical reaction and possibilities to obtain an Al2O3/Ni–P composite

A chemical electroless method for Ni–P deposition on the surface of Al2O3 powder with the use of phosphate baths has been presented. The possibility of ceramic/metal nanocomposite formation by sintering the coated powders at temperatures of 1200 and 1400°C is described. The results of the sintering process showed that at both sintering temperatures, Ni–P becomes a liquid. Moreover, the beginning of the sintering process of the ceramic matrix at 1400°C was observed. This temperature is lower than required for the sintering of pure Al2O3 (1600°C). This result indicates the possibility to decrease the sintering temperature of Al2O3/Ni–P composites.

Corrosion Protection of Steel Using Nonanomalous Ni-Zn-P Coatings

A novel technique for obtaining nonanomalous Ni-Zn-P coatings with high Ni content (74 wt % as compared to 15-20 wt % in the conventional plating method) has been developed. These coatings show promise as a replacement for Cd in sacrificially protecting steel. Ni-Zn-P coatings were deposited using an electroless method from a solution containing complexing agent and ammonium chloride. Varying the concentration of in the bath controls the final amount of Zn in the deposit. The Zn content in the coating was optimized based on the corrosion resistance of the final deposit. Coatings with 16.2 wt % Zn were found to display a potential of vs. SCE that is more electronegative to steel and hence can be used as a sacrificial coating for the protection of steel. Deposition parameters like pH and temperature have been optimized based on composition of the coating and the surface morphology. Corrosion studies in corroding media show that Ni-Zn-P coatings obtained using the electroless method show a higher barrier resistance and better stability as compared to cadmium coatings. © 2003 The Electrochemical Society. All rights reserved.

Study on properties of high reinforcement-content aluminum matrix composite for electronic packages

High reinforcement-content aluminum matrix composite, with a high thermal conductivity, the adjustable coefficient of thermal expansion, low density and costs, have been extensively applied in electronic package. The Sip/Al composites were fabricated by squeeze casting technology. The microstructure observation showed that the composites were dense and macroscopically homogeneous, with no micro-holes and obvious defects. The linear CTEs of Sip/Al composites lay between 7.6-8.1/spl times//sup 10-6// /spl deg/C, and the thermal conductivity was larger than 100 W/ (m/spl deg/C). The composites also had lower density (2.4 g/cm/sup 3/), higher special strength and special modulus. The electroless nickel method was used to deposit a continuous and uniform layer on the composites surface, which can meet the reliability testing demands of the diodes with Sip/Al composite baseplate.

Electroless polyol deposition of FeNi-based powders and films

Iron-nickel-based powders and thin films were synthesized by an electroless polyol method. The growth process as a function of deposition time was studied. The Fe concentration of deposited films and precipitated powders were similar and independent of deposition time. The metalorganic intermediates were present in powders and their amount decreased with time. The morphological investigations suggested that 60 min was the optimum deposition time to deposit dense films with particles of narrow size distribution. In addition, the films deposited at 60 min also possessed the highest saturation magnetization due to a more ordered atomic environment of nickel. The as-deposited Fe was apparently oxidized in the films.

Electromagnetic interference shielding effectiveness and mechanical sliding behavior for electroless nickel/phosphorous–poly(tetrafluoroethylene) codeposition on carbon fiber/acrylonitrile–butadiene–styrene composites

AbstractPoly(tetrafluoroethylene) (PTFE) powders were mounted on an electroless nickel/phosphorous (Ni/P) film on the surface of a carbon fiber by an electroless codeposition method. This type of carbon fiber filler, denoted FENCF, was then compounded with acrylonitrile–butadiene–styrene (ABS) for use in electromagnetic interference shielding. For the suspension of the PTFE powders, a surfactant was used. Although the adhesion between the electroless Ni/P–PTFE films and the fiber was reduced, the PTFE powders on the surface of FENCF reduced the torque values when compounded into the ABS matrix because of a self‐lubricating effect. The two‐step FENCF composites exhibited particularly significant advantages. The torque values for the two‐step FENCF/ABS composites were about one‐half of those for carbon fiber/ABS composites in compounding processes; in addition, the former had an average mean fiber length almost 2.5 times that of the latter. The multiyield phenomena in stress–strain curves of FENCF/ABS composites implied that the PTFE powders mounted on Ni/P films slid during stress–strain action. The electromagnetic interference shielding effectiveness of FENCF/ABS composites did not decrease significantly even though the PTFE powders formed a discontinuous phase on the electroless Ni/P films. The mechanical properties of FENCF composites were enhanced because of the larger fiber length. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1661–1668, 2002