Papers by Keyword: Electro-Deposition

Abstract: Magneto-impedance ratio of the multilayer [NiFe/Cu)]_N study by the number of multilayer. The both sample films of NiFe and Cu are fabricated by electrodeposition methods on a Cu-patterned substrate. The characteristic of magneto-impedance (MI) is performed at room temperature. Magneto-impedance are modified by varying N times (2, 4, 6 and 8) and the measurements frequency. The result show that the typical symetry of the magneto-impedance curve. Then the magneto-impedance (MI) ratio increases with the increase of frequency and N number layers. The increase of the magnetic permeability should address the increase of the MI ratio. Finally, the highest magneto-impedance ratio of 13.79 is obtained for [NiFe (200)/Cu (25)]₈ at frequency 100 kHz.

Abstract: Influence of gamma irradiation to the magneto-impedance ratio of the electrodeposited [NiFe/Cu]₄ multilayer on meander-shape PCB substrate has been studied. The magneto-impedance ratios were measured for both un-irradiated and irradiated by gamma radiation of Co-60 with a total dose of 40 Gy. The morphological structure were done by using scanning electron microscopy (SEM). The decrease in grain size of the samples after Gamma irradiated is observed. The magnetic property modifies as consequence of the change in the microstructure samples. Within result, the magneto-impedance ratio decreases around 34.9% for irradiated sample.

Abstract: This paper reports on fabricated hard magnetic cobalt nickel phosphorous (CoNiP) films with electro-chemically deposition technique on copper substrate in the presence of different urea (0 to 10 g/L) and NaH₂PO₂ (16 to 21 g/L) concentrations. Thin films were obtained at current density ranges from 5 to 20 mA/cm² and temperature varies from ambient temperature to 60°C. Magnetic properties namely coercivity, remanent magnetization, saturation magnetization and squareness of the films were studied using Vibrating Sample Magnetometer (VSM). The result showed that for bath containing higher concentration of urea (10 g/L), bright films with higher coercivity were obtained at moderate current density (15 mA/cm²) and at higher temperatures (40-60°C). In contrary, uniform and bright films were produced at ambient temperature in bath containing no urea or lower concentration of urea. Scanning Electron Microscopy (SEM) revealed that porosity and cracking tendency are increased with increasing temperature. CoNiP thin films with improved magnetic properties are thus obtained for plausible applications in high density recording media and MEMS.

Abstract: Open cell aluminum foams are a promising multi-functional material that has potential application in a variety of engineering fields, but their too low mechanical properties may restrict their applications in some load bearing conditions. To overcome this shortcoming, enhancement methods have been widely investigated in recent years including surface enhancement technologies. In the present study, an electrodeposition process was utilized to coat an amorphous Ni-P coating on the cell strut surface of open cell aluminum foams. The results show that the coated film exhibits typical amorphous feature and is thermally stable. The average nanohardness and Young’s modulus are 7.0GPa and 118.1GPa, respectively, in which the Young’s modulus is even 1.6 times higher than that of aluminum (70GPa). It is because the high strength film that leads to significantly enhancement of the foams. The compression strength of the foam was increased from about 0.2MPa to 11.9MPa when the film thickness was around 65μm. These results demonstrate that the surface coating does be an effective way to improve the mechanical properties of open cell aluminum foams.

Abstract: This paper compares the microstructure and electrochemical properties of the diamond-like carbon films obtained by two different deposition methods - microwave electron cyclotron resonance plasma enhanced chemical vapor deposition (MWECR-PECVD) techniques and electro-deposition – chosen for their low cost and capacity to produce films. The microstructure of the DLC films are investigated by Raman spectroscopy, FTIR spectroscopy, and electrochemical behavior is investigated by potentiodynamic and electrochemical impedance spectroscopy (EIS). Raman spectroscopy indicates that all the films deposited by different techniques show amorphous structure and typical characteristic of DLC film. FTIR spectrum results indicate that these DLC films are a-C:H films. As a result of EIS, the DLC films made by different methods showed obviously different electrochemical characters. The obtained results show that the DLC films deposited using the PECVD methods provided the better results, presenting a high corrosion resistance , high adherence to substrate, and a denser and more uniform surface.

Abstract: Atomic structures of fabricated Fe-Co alloys were investigated real time by time resolved x-ray absorption spectroscopy (TRXAS) at annealing temperature of 400° C. The various compositions of Fe-Co alloy thin films were prepared by electro-deposition on indium-tin oxide glass substrate with iron sulfate and cobalt chloride electrolyte solutions. The current density of 80 A/m² was used to deposit Fe-Co thin film with varying the ratio of Fe and Co ion concentrations. The Fe-Co alloys with boron nitride powders were mixed, grinded and pressed in the pallet form in order to insert into environmental controlled sample holder for TRXAS measurement. The samples were annealed under 20% oxygen and 80% nitrogen atmospheric by increasing the temperature up to 400° C and then remaining for an hour. The influence of annealing temperature can modify the atomic structures of Fe-Co alloys as indicated in the variation of extended x-ray absorption fine structure (EXAFS) peaks. Most of the EXAFS peaks followed the temperature profile i.e. increasing or decreasing during the temperature rising and then maintaining about constant values during holding the temperature at 400° C. By transforming the EXAFS peaks into scattering radius space, the modification of relative scattering amplitude from each nearest neighbor position indicated the atomic relocation during annealing the samples. Some of scattering patterns from Fe and Co oxides can be found and their amounts changed during rising the annealing temperature. In addition, the atomic relocations extracted from the Co absorption edge was very much smaller than those of Fe edge probably due to relative more stable of Co atomic positions for this range of annealing temperature.

Abstract: An investigation into the suitability of carbon materials, metallic lead and its alloys as substrates for the zinc electrode in acid Zn-PbO₂ flow batteries was performed. No maximum current appears on the potentiostatic current transients recorded for the zinc deposition on the lead and its alloys. With increasing the overpotential, the progressive nucleation turns to be the 3D-instantaneous nucleation process employed for the resin-graphite composite. Hydrogen evolution on the graphite composite is effectively suppressed due to the doping of polymer resins. The rate of hydrogen evolution reaction on the lead is relatively weak, but on the lead alloys, the hydrogen evolution conversely becomes serious to a certain degree. Though the exchange current density of the zinc deposition and dissolution process on the graphite composite is relatively low, the zinc corrosion is weakened to a great extent. With the increase of deposition time, the zinc deposits tend to be more compact. Zinc galvanostatic charge-discharge cycling on the graphite composite reveals that the coulombic of over 90% can be found, exhibiting an excellent cycling stability.

Abstract: Mechanical response of polyurethane open-cell foam with electrodeposited copper coatings under compressive loads is investigated via experimental characterization. Commercially available open-cell polyurethane foam specimens are copper deposited using electroless and electro-deposition techniques. Thickness and composition of the coating are controlled by varying the deposition time to 30, 60 and 90 minutes. Micrographs of the coated foam structure show that the coating thickness is higher at the outer surface, and the averaged thickness linearly depends on the deposition time. The coated foam exhibits a stiffer compressive response than that of the uncoated one. When unloaded, the copper coating layers fracture at the center of foams ligaments, and fall off from the foam structure.

Abstract: Black chrome coatings were electrodeposited under galvanostatic conditions on SS substrates. To enhance the thermal stability of the coatings for viable usage in parabolic trough receiver tubes in solar thermal applications beyond 250°C, graphite encapsulated FeCo nanoparticles had been introduced in the electrolyte solution at different weight percentages (0.025, 0.05, 0.1). An increase in the thermal stability of the coatings in the range of 400°C to 600°C is noticed from the STA analysis. The corrosion analysis (Tafel) and cyclic voltammetric studies of the coatings in the presence and absence of nanoparticles have been carried out in 3.5% NaCl solution to understand the stability of the coating in saline environment.

Abstract: Highly ordered Ni-Ag alloy nanowire arrays have been fabricated successfully by electrodeposition into the pores of anodic aluminum oxide (AAO). This template was prepared with modified two-step anodizing method. The scanning and transmission electron microscopy were utilized to characterize the Ni-Ag alloy nanowire arrays. The results revealed that the nanowire arrays were regularly arranged, about 90nm in diameter and 30µm in length. The nanowires were single crystal and the atomic ratio of Ni and Ag is very close to 79:21. Magnetic hysteresis loop showed that Ni-Ag alloy nanowire arrays embedded in AAO have superparamagnetism, indicating their potential applications in biomedical materials.