Showing 7 results for Electrodeposition
K. Raeissi, A. Saatchi and M. A. Golozar,
Volume 23, Issue 2 (1-2005)
Abstract
On electropolished steel at low current densities, morphology and texture of electrodeposited zinc were investigated. Zinc coating is consisted of hexagonal crystallites laid on each other to produce packets. These packets are of different sizes and are stacked in different orientations to construct a homogeneous coating on steel substrate. This coating does not have texture, i.e., it has a random texture. With increasing current density, the morphology changes completely as each grain attains a special orientation. In this case, coating has a strong basal plane (0002) along with low angle planes (1013 and 1014). Coating obtained on mechanically polished surfaces consists of individual packets of zinc crystals, which are near each other with different
orientations. These coatings have a higher density of basal plane (0002) in comparison to electropolished surfaces. The morphology and texture variations with cathodic polarization and surface preparation of steel are due to their effect on nucleation and growth.
I. Kazeminezhad, N. Monzavizadeh, M. Farbod,
Volume 29, Issue 2 (12-2010)
Abstract
In this work, NiCu and CoCu alloy nanowires were prepared by electrodeposition within nuclear track-etched polycarbonate membranes with the nominal diameter of 30nm. Electrodeposition was carried out under potentiostatic control with three electrodes. In order to grow CoCu nanowires and NiCu nanowires, an electrolyte containing salts of Co and Cu, and an electrolyte containing the salts of Ni and Cu were used respectively. Then, the potentiodynamic behavior of each electrolyte was investigated by its CV curves, and the optimum potentials for the deposition of Ni, Co and Cu were selected according to these curves. A TEM microscope was used to study the structure of the nanowires. The results showed that the crystalline growth is polycrystalline and the diameter of the wires is about 80 nm. Apart from that, some nanowires were deposited under different deposition voltages. EDX analysis showed that the atomic weight of Ni and Co in all samples vanishes in the potentials between -0.5V to -0.8V which indicates that pure Cu atoms are deposited at these voltages. Deposition of Ni and Co starts at more negative voltages such as -0.9 and -0.85 V, respectively.
B. Bakhit, A. Akbari,
Volume 31, Issue 2 (12-2012)
Abstract
Composite and nanocomposite Ni-Co/SiC coatings were synthesized by electro-codeposition of micro and nano-sized SiC particles with average diameter of 10m and 20nm using horizontal electrodes. Surface morphology, chemical composition, phase composition, hardness and corrosion resistance of the deposited coatings were studied using SEM observations and EDX, XRD, microhardness and polarization measurements as a function of the electrodeposition current density. The results indicated that the nanocomposite coatings exhibit higher hardness and corrosion resistance compared with the composite coatings containing micro-sized SiC particles despite their lower percentage of the SiC content. The maximum hardness values of 615HV and 490HV were obtained for nanocomposite and composite coatings deposited at current density of 3A/dm2. The observed properties were discussed based on the structural details.
S. Khorsand, K. Raeissi, F. Ashrafizadeh,
Volume 34, Issue 4 (3-2016)
Abstract
Super-hydrophobic nickel and nickel-cobalt alloy coatings with micro-nano structure were successfully electrodeposited on copper substrates with one and two steps electrodeposition. Surface morphology, wettability and corrosion
resistance were characterized by scanning electron microscopy, water contact angle measurements, electrochemical impedanc spectroscopy (EIS) and potentiodynamic polarization curves. The results showed that the wettability of the micro-nano Ni and Ni-Co films varied from super-hydrophilicity to super-hydrophobicity by exposure of the surface to air at room temperature. The corrosion results revealed the positive effect of hydrophobicity on corrosion resistance of Ni coating (~10 times) and Ni-Co coating (~100 times) in comparison with their fresh coatings. The results showed that super-hydrophobic nickel coating had higher corrosion resistance than super-hydrophobic nickel-cobalt coating.
V. Rajaei, K. Raeissi, M. Shamanian, H. Rashtchi,
Volume 35, Issue 1 (6-2016)
Abstract
In this study, Ni-Mo nanocrystalline alloys were prepared on steel substrates by electrodeposition method from citrate-ammonia bath by applying current densities 30, 60 and 100 mA/cm2. Results indicated that the obtained coatings were uniform and compact. Moreover, molybdenum content in the alloy and current efficiency decreased with increasing electrodeposition current density. X-ray diffraction analyses indicated that all coatings were composed of face-centered cubic solid solution of molybdenum in nickel with grain size of 9-5 nanometer. Moreover, the most intensive plane in X-ray diffragtogram was (111). On the othe hand, roughness measurements indicated that surface roughness escalated with increasing current density. Corrosion behavior study showed decrease in corrosion current density of substrate with applying Ni-Mo alloy coatings. In addition, corrosion current density reduced with increasing molybdenum content of the coating and the minimum amount was related to the coating with 13 atomic percent molybdenum.
M. Alizadeh, A. Cheshmpish,
Volume 37, Issue 2 (9-2018)
Abstract
In this research, Ni-Mo-Al2O3 composite coatings were electro-deposited on the mild carbon steel in a citrate bath containing micro- sized Al2O3 particles. Afterward, the effect of the particle concentration in the electrolyte bath (ranging from 0 g/L to 30 g/L) on the microstructure, microhardness, and corrosion performance was evaluated. To investigate the microstructural changes and the surface morphology of the coatings, as well as the particle distribution in the deposits, optical and scanning electron microscopy coupled with the energy dispersive X-ray spectroscopy was utilized. The corrosion behavior of the prepared coatings was investigated in a 3.5 wt. % NaCl solution. The results showed that the presence of the Al2O3 particles in the Ni-Mo coatings changed the microstructure and also, increased the microhardness and corrosion resistance of them. It was also found that the desirable structure of the protruding crystallite morphology with no detectable pores could be achieved at the medium concentrations of reinforcement (e.g. 20 g/L). Further the optimum concentration of the particles in the electrolyte bath to attain the composite coating with the desirable microstructure and consequently, the desirable corrosion resistance was found to be 20 g/L.
M. Tafreshi, S. R. Allahkaram, S. Mahdavi,
Volume 37, Issue 3 (12-2018)
Abstract
In this research, Zn-Ni and Zn-Ni/PTFE coatings were electrodeposited from sulfate-based electrolytes. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to investigate the corrosion properties of the coatings. Hardness and tribological behavior of the coatings were examined by the Vickers microhardness testing machine and the pin-on-disc method, respectively. Chemical composition and morphology of the as-deposited and worn surfaces of the coatings were studied by a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). According to the results, the corrosion current density of the Zn-Ni film was about 30% of that of the composite coating. Hardness of the alloy film was partially decreased by the incorporation of Polytetrafluoroethylene (PTFE) particles. However, the wear loss and coefficient of friction of the Zn-Ni/PTFE coating were, respectively, about 43% and 57% of those of the Zn-Ni film. Moreover, wear mechanism was changed from plastic deformation and adhesive wear to slight abrasion by the co-deposition of PTFE particles.
