Effect of pH on electroless nickel deposition on alumina substrates for chip resistor application
Alumina has been used widely in electronics industry specifically for chip resistor application. Currently, the deposition of nickel on alumina surface using electrodeposition method suffered from the insufficient bonding between the metallic coating (nickel) and the ceramic substrate (alumina). Electroless deposition method however can produce strong adhesion between the metallic coating and ceramic substrate. In this research, the effect of pH on the electroless nickel on alumina substrate was investigated. The electroless deposition of nickel on alumina substrate was conducted at pH 4.0, 5.6 and pH 10.0 for 3, 5, 10, 20 and 30 minutes at constant temperature. The crystal structure of the substrate and coating was characterized by using X-ray diffraction (XRD). The surface morphology of the coating was observed by using scanning electron microscopy (SEM) and the coating thickness was measure by X-ray fluorescence (XRF). The coating performance was tested by using Standard ASTM D3359 (Tape-Test). It was found that the optimum pH of plating solution was 10.0 with the maximum thickness was obtained at 30 minutes of deposition with thickness of 1.15 μm. These optimum coating parameters shows homogeneous and uniform nickel deposition on the alumina surface as observed by SEM. Nickel deposition by electroless method at pH 4.0, 5.6, and 10.0 have excellent bonding with alumina substrate as shown by tape test analysis.
Pure nickel coating on a mesoporous alumina membrane: Preparation by electroless plating and characterization
Abstract This work concerns the preparation and characterization of a composite inorganic membrane based on nickel supported on a tubular porous ceramic for use in high temperature hydrogen separation. The characteristics required of this material for a high hydrogen permselectivity are a defect-free coating and thermal stability. Thus, electroless plating of nickel using hydrazine as reducing agent enables a metallic nickel coating to be deposited directly on an asymmetric alumina support having a mesoporous top layer composed of γ-alumina. To optimize conditions for reduction of the metal ion, variables including the temperature, the nature of the nickel salt, the choice of stabilizer and the hydrazine concentrations in the plating bath were studied. Metallic nickel was found to be dispersed both in and on the γ-alumina. After heat treatment at high temperature, a thin and uniform pure Ni˙ layer (thickness ≈ 1–1.5 μm), characterized by scanning electron microscopy (SEM) and X-ray Diffraction (XRD), was formed. The separation performance of the Ni/ceramic membrane was investigated using single gases (hydrogen, nitrogen, carbon dioxide and methane) at room temperature. The results indicate that the mechanism of hydrogen transport is related to the Knudsen diffusion.
Preparation of a Palladium Composite Membrane by an Improved Electroless Plating Technique
An ultrathin palladium membrane was prepared by an improved electroless plating technique on the surface of a porous titania ceramic substrate. A simple yet new and valuable activation technique named photocatalytic deposition (PCD) has been presented. The thickness of the resulting palladium membrane was about 0.3−0.4 μm. Hydrogen permeation through the composite membrane was proportional to the hydrogen partial pressure difference. The hydrogen permeability and H2:N2 selectivity through the palladium composite membrane are 6.3 × 10-6 mol m-2 s-1 Pa-1 and 1140 at 773 K, respectively. The activation energy for hydrogen permeation is 21.27 kJ/mol at the temperature range of 673−773 K. Long-term hydrogen permeation operation at 673 K indicated that the flux through the resulting membrane under hydrogen/nitrogen gradients requires 80 h to reach a steady state. The steady-state hydrogen flux showed no observable changes during the thermal cycles between 673 and 773 K.