Sharif Digital Repository

The formation of the oxide layer with Zr compounds on AZ31 Mg alloy processed by two-step plasma electrolytic oxidation (PEO) has been investigated. After the PEO process first in an alkaline phosphate electrolyte and second in an acid electrolyte containing K2ZrF6, the microstructure, chemical composition, and phase composition of the oxide layers were analyzed via SEM, EDS, and XRD, respectively. The electrochemical reaction and the high temperature caused by the plasma discharges in the electrolyte were the main factors leading to the fabrication of an oxide layer containing Zr compounds on AZ31 Mg alloy. The micro-pores were filled with ZrO2 formed during the PEO process. The results of... 

Alumina-silicate composite coatings were formed on titanium substrate by plasma electrolytic oxidation (PEO) process using a silicate-based electrolyte containing alumina nanoparticles. Microstructure, chemical and phase compositions, and thickness of the coatings were investigated to determine, coating mechanism and probable reactions during the process. The effect of processing time on corrosion resistance of the coatings was investigated using the potentiodynamic polarization test. Barrier layer (TiO2) formation, micro arcs occurrence, and electrolyte ionization were the main stages of PEO coating growth process. Alumina nanoparticles were incorporated into the coating by cataphoretic and... 

Electrophosphating is the novel method for accelerating the low temperature phosphating bath. This method can be performed as cathodic and anodic treatments. Both of them influence the coating deposition mechanism and therefore coating properties. In this study Zn-Ni electrophosphate coating was applied on galvanized steel using cathodic and anodic electrochemical methods. Microstructure, composition and corrosion resistance of coating were characterized by using a scanning electron microscopy, X-ray diffraction method and potentiodynamic polarization test respectively. The results of this study indicated that, by using cathodic method, compact phosphate coating with high corrosion... 

Electrophosphating is the novel method for accelerating the low temperature phosphating bath. This method can be performed as cathodic and anodic treatments. Both of them influence the coating deposition mechanism and therefore coating properties. In this study Zn–Ni electrophosphate coating was applied on galvanized steel using cathodic and anodic electrochemical methods. Microstructure, composition and corrosion resistance of coating were characterized by using a scanning electron microscopy, X-ray diffraction method and potentiodynamic polarization test respectively. The results of this study indicated that, by using cathodic method, compact phosphate coating with high corrosion... 

This study focuses on the effect of co-deposition of PTFE and/or MoS 2 particles on the morphology, wear, and corrosion properties of electroless nickel coating. The composite coating of EN-PTFE-MoS 2 was heat treated at different temperatures for hardness investigations. The surface morphology of coatings was characterized by scanning electron microscopy. Pin-on-disk and potentiodynamic polarization tests were used to study the tribological and corrosion properties of the coatings, respectively. Results of hardness analysis revealed that the hardness of electroless nickel coatings was increased by the heat treatment, and its maximum was gained at 400°C. Wear investigations showed that... 

In this study, biocompatible ceramic layers containing TiO2 and hydroxyapatite (HA) nanoparticles (TiO2/HA) were deposited on pure commercial titanium (Grade 2) by using plasma electrolytic oxidation and AC power supply. The coating process was carried out in five different solutions for various times at a current density of 500 mA cm−2. To achieve the optimum conditions for thickness and microstructure, the coating process was conducted in solutions with a 3 g L−1 concentration of HA nanoparticles. FESEM, XRD, and FTIR results showed that HA nanoparticles were successfully incorporated into the pores of the layer. Furthermore, the corrosion behavior of the coating layers in the simulated... 

Ti and TiN thin films were deposited by means of electron beam evaporation on stainless steel substrates, and subsequently annealed at different temperatures (650, 750 and 850 °C) in a nitrogen atmosphere. The surface morphology of the films studied by atomic force microscopy (AFM), was found to exhibit specific multifractal properties depending on the annealing temperature. It turned out that the width of the multifractal singularity spectra, f(α), decreased as the annealing temperature increased up to 750 °C, but it increased when the temperature was kept at 750 and 850 °C accompanied by the rapid development of the surface objects. The generalized fractal dimension followed a similar... 

Ni-Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni-Co alloy and Ni-Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.%... 

In this study, water-soluble terpolymers containing highly hydrophilic monomers of acrylamide and maleic anhydride and highly hydrophobic monomers of styrene were synthesized (ASM) through the one-step inverse emulsion polymerization. Proton nuclear magnetic resonance (1H NMR), fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction pattern (XRD) were performed to investigate the chemical structures and structural transformations of ASM. Thermal stability and thermal decomposition steps of ASM were studied by thermogravimetric analysis (TGA). An Ubbelhode capillary viscometer and a rheological mechanical spectrometer (RMS) were employed to obtain the specific, relative, and...