Papers by Keyword: Ni-Co Alloy

Abstract: Nickel-cobalt alloys have broad application prospect for their excellent properties (i.e. high microhardness, strength, abrasion, corrosion resistance and magnetic properties.etc). Present situation and new trends on mechanism of the anomalous codeposition and technology of electrodepostion of nickel-cobalt were studied. Effects of electrolysis parameters (e.g. concentration of co2+in the electrolyte, cathodic current density, pH value, temperature.etc) on the alloy composition, morphology and mechanical properties were analyzed. The formation of the monovalent intermediate (hydroxides or colloid) may cause the cobalt preferential deposition or the faster charge-transfer of Co2+ reduction compared to that of Ni2+ reduction is the main factor that causes the anomalous codeposition behavior of the nickel-cobalt alloy.

Abstract: A fully dense nanocrystalline Ni-Co alloy with 18 nm grain size exhibited high strength of about 2200 MPa and ductility of 8.19.2% at strain rates of 1.04×10-5 to 1.04 s-1 and room temperature. The alloying of Co element induces the grain refinement, solid solution hardening and decrease of stacking fault energy should contribute to the favorable combination of mechanical performance. The obvious distinctions of fracture-surface morphologies with strain rate alteration were attributed to underlying deformation mechanism transition. The high strain rate sensitivity exponent and small activation volume indicate that grain boundary activity may be expected in this alloy.

Abstract: The effects of additive TN1, power waveforms (full wave, half wave, and direct current), current density and pH on the throwing power of Ni-Co alloy electroforming solution had been investigated by orthogonal tests; and the effects of plating parameters on current distribution of cathode by ANSYS numerical simulation were discussed. The results of orthogonal test showed that the additive TN1 had the largest effect on the throwing power; the power waveform was secondary; the current density and pH had minor effect. The biggest throwing power was 78% when the TN1 was 15g/L and waveform was full wave. Numerical simulation showed that the cathode shape and shield had effect on current distribution; reasonable cathode shape and application of shield could improve the current distribution. The thickness uniformity of part could be up to 92% by optimizing of electrolyte, adjusting the electroforming technics and applying second electroplating.

Abstract: The traditional pure nickel coatings and the Ni-Co alloy coatings were prepared with the same parameters on the type 316L stainless steel substrates by utilizing two-ways pulse current electroplating method. And then, we used atomic force microscope (AFM) to observe their surface morphologies and structures and obtained their 3D images. The results of AFM showed that the Ni-Co alloy coating were superior to the traditional pure nickel coating on mechanical and tribological properties respects. For example, the surface of the Ni-Co alloy coating is smoother and even than that of the traditional pure nickel coating. Direct current (DC) and two-ways pulse current electroplating two methods were adopted respectively to prepare the Ni-Co alloy coatings. Followed we observed their surface morphologies by using AFM. The result showed that under the same experimental parameters the coating of the two-ways pulse current electroplating is superior to conventional DC electroplating coating in the surface morphology, grain size and microstructure and so on.

Abstract: The influence of a static magnetic field of 4.4 T on the electrodeposition process on copper plates immersed in a solution of Nickel and Cobalt ions is presented. The electrodeposited layers characterized by Scanning Electron Microscopy (SEM) including Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM).It was observed that the difference between the mass of electrodeposition with the application of a Permanent Parallel Magnetic Field to the electrode surface (PPMF) and the electrodeposited layers without the PPMF, increased with the increase of current density. The presence of the PPMF gave smoother electrodeposited surface compared to without the PPMF. The increase in current density gave fewer the cracks on the electrodeposited surface.

Abstract: In this paper, NiCo2O4 spinel oxide was synthesized by the oxidation of Ni-Co alloy. The variables that affect the formation of spinel oxide include the Ni-Co ratio in the alloy, the oxidation temperature and time. 350°C is the upper oxidation temperature limit. And longer oxidation time is helpful. Surface roughness analysis shows that with the formation of NiCo2O4, the surface shows rougher.

Abstract: This study presents an innovative imprinting method to fabricate IC devices by micro-punch process. Normally, imprinting method is used to imprint plastic materials such as photoresist and polymeric materials. In this study, imprinting process is applied to micro-punch metallic materials directly for IC devices. Fabrications of IC devices with high aspect ratio structures ranging from micrometer to sub-micrometer are described. In this study, to keep the production costs as low as possible, a complete micro-punching process is applied to replicate IC devices. A combination of lithography, extra-hard alloy nickel cobalt (Ni/Co) electroplating process (as a metal imprint mold for punch) and chemical mechanic polishing (CMP) process is used to flat the extra-hard alloy micro-punch head. It is worth noticing that the Ni-Co electroplating process with hardness over Hardness of Vicker (Hv) 560 is developed. With such hardness, it can stand the high pressure and abrasivness to confine the accuracy during micro-punching process. With regard to the electroplating process, Ni-Co is deposited and covered on the photoresist template uniformly by electroplating. The Ni/Co mold is served as master for micro-punching process to replicate the pattern onto polyimide (PI) or copper sheets. Finally, the experimental results are measured and characterized.