فهرست مطالب abolghasem dolati

In this study, the effect of several industrial protective coatings such as alkyd base primer, zinc rich primer and polyamide primer coatings in compassion with the surface paints comprising alkyd, polyamide and polyamine were investigated. For evaluating corrosion and durability of concrete properties, strength of mixture, electrochemical impedance spectroscopy (EIS) and pull of test was accomplished. The outcomes significantly demonstrated EIS method performs an excellent response to corrosion analysis of coating upon the rebar. Beside, in harsh media the two parts of isocyanide-acrylic coating with a surface resistance approximately 7.3 GΩ.cm2 shows the best manner

Titanium nitride-carbon nanocomposites have been synthesized by the reaction of TiCl4 and NaN3 in supercritical benzene medium that also serves as a carbon source. The as-prepared precursor has been subjected to different heat treatments under ammonia and nitrogen atmospheres. The structure and chemical composition of the synthesized TiN-C nanocomposites are studied by X-ray diffraction (XRD) and CHN elemental analysis. Meanwhile, the nature of carbonaceous species and the respective carbon phase transitions during supercritical process and following heat treatments are further investigated by Raman spectroscopy, time of flight secondary ion mass spectrometry (ToF-SIMS), and their charge-discharge characteristics with respect to lithium storage. After 10 h NH3-treatment at 1000 ˚C carbonaceous phase transforms to graphene layered structure. The highly efficient mixed TiN conducting network and the internal defects between G layers induced by nitrogen doping improve rate capability and cycling performance of G sheets and provides a specific capacity of 381 mAh g-1 at charge/discharge (C/D) rate of 0.2 C. The enhanced electrochemical performance of the SIV nanocomposite is mainly due to improving the electronic/ionic conductivity and reducing charge transfer coefficient and increasing electrochemical surface area that are resulted from anchoring of TiN nanoparticles on graphene sheets.

The Cu-0.5Co/WC nano-composite coating was synthesized on CP-copper substrate using direct current (DC) electrodeposition method. At this work, it was tried to increase the hardness of surface without considerable degradation of copper's particular physical properties such as electrical conductivity. The effect of current density on microstructural homogeneity, hardness, fracture toughness and electrochemical behavior of coating was investigated. The copper plates with the purity of 99.99% were used as electrodes. The electrolyte consists of tungsten carbide particles (30 g/l), copper sulfate (200 g/l), sulfuric acid (50 g/l), cobalt sulfate (50 g/l) and sodium dodecyl sulfate (SDS) (0.3 g/(g of WC)) as surfactant. The particle size of tungsten carbide powder was in the range of 40-70 nm. The distribution of tungsten carbide particles in coating was studied using FESEM. Micro-hardness measurement was performed in Vickers scale. The fracture toughness of coating was determined by Vickers indentation test. The corrosion resistance of the electrodeposited Cu-Co and Cu-Co/WC nano-composite coatings was evaluated by polarization studies. Referring to results, the use of optimum current density value (60 mA/cm2) during the electrodeposition process improves hardness and corrosion resistance of nano-composite coating. Additionally, Cu-Co/WC composite coating shows more corrosion resistance than the unreinforced one.

The Production of iron- bronze bimetallic artifacts is one of the techniques of the Bronze Age to the Iron transitional period. In this research, in order to assess the alloy composition and method of production, two iron-bronze bimetallic objects in the site of Ziviyeh have been studied as one of the important Iron Age sites in Iran. The microstructure of the cross section of objects, the phases and metallic and nonmetallic inclusions was studied by the optical microscope (OM) and the scanning electron microscope equipped with an elemental analysis (SEM-EDX). The results shows the ferrite-pearlite microstructure and preferred orientation of inclusions in substrate of base metal that is decorated with bands of tin- bronze alloy. The amount of carbon in different parts of the body of objects is not the same. Dendritic microstructure and distribution of gas holes in copper phase of bronze strips confirmed the use of casting-on technology in production of bronze layers. Fine grains and twin lines in the outer edges of bronze strips are the result of final hot working.

Nickel coating has a poor surface mechanical properties. In order to improve the mechanical properties, nickel were covered with ceramic particles. In this study, the Ni/TiN composite coatings were produced by Watts bath containing TiN nanoparticles. The effects of deposition current density, electrolyte agitation speed and the number of particles were investigated. The presence of particles was determined by EDS analysis and the coating morphology was examined by SEM. The corrosion samples were examined by linear polarization tests. It was observed that the maximum amount of particles is formed at the current density of 4 A/dm2 and the agitation speed of 450 rpm.

Composite Electrodeposition is a low-cost and low-temperature method، which is used to make metal matrix composite coatings. In This study the surfactant of anionic (SDS) and cationic (CTAB) is used as additive in composite coating of Ni/TiN. The results showed that the anionic surfactant caused more particles in the composite coatings. Increasing SDS concentration to the optimal value leads to more uniform dispersion of nanoparticles in the coating. The hardness of pure nickel and optimal composite coating is measured by AFM and the results showed that the hardness of the coating increases from 1. 86Gpa to 3. 23Gpa، in the presence of particles.

Anodic oxidation can be done in order to obtain a porous structure، and to obtain TiO2 nanotubes. In the current research، first، titanium dioxide nanotubes were fabricated by anodic oxidation and then hydroxyapatite nanoparticles have been deposited onto nanotublar TiO2 by electrophoretic deposition at 30V for 10min and then sintered at 400°С for 2hr. Corrosion behavior in SBF at 37˚С was evaluated. The results show that formation of TiO2 nanotubes and sintering improve corrosion behavior in SBF.

Porcelain enamels are widely used as coating on metals and alloys, because of their excellent corrosion resistance against different aggressive media with different pHs at high temperatures up to 600oC. In this regard, the chemical composition of the enamels is very important and TiO2 is introduced as additive to promote the corrosion resistance of the enamels. Therefore, corrosion resistance of TiO2 containing and TiO2 free enamels has been examined by applying standard test method ISO 2742. This test has been done in simulated sour water that is one of the most corrosive solutions which is produced during oil refining in refineries. The test has been performed three times on samples for 2.5h. Then, the attacked surfaces were studied by Scanning Electron Microscope (SEM) and then elemental distribution of surface was investigated by Energy Dispersive Spectroscopy (EDS). Finally, by applying Electrochemical Impedance Spectroscopy (EIS), Nyquist spectra of the samples were obtained and compared. The results showed that adding 3.20%wt TiO2 considerably enhanced the chemical and corrosion resistance of the enamel.