IRANIAN JOURNAL OF SURFACE SCIENCE AND ENGINEERING
Year:2017 | Volume:12 | Issue:30|Papers Count:10

The aim of this study is applied zirconia sol-gel coatings on steel substrate API5L to evaluate the effect of number of layer and type of sintering on the corrosion resistance of these coatings. For this purpose the 4 and 2 layer zirconia sol gel coating using zirconium propoxide as a precursor was applied on API5L carbon steel by dipping method at constant speed 6 cm/min in sol. A group of samples for each cycle of immersion, drying at 110oC for 30 min and sintering for 1h at 450oC, while others group with repeated cycle of dipping+drying, the coating was applied to the desired number of layers and the sintering was accomplished at 450oC for 1h. Before sintering the thermal analysis of TG-DTA was completed in order to determined to the optimum temperature of gel calcinations or sintering of coated samples. The coating film of zirconia was characterized by FTIR, DTA, XRD and SEM. Properties of coated samples evaluated by measurement of microhardness and electrochemical tests. The results indicate for heat treatment at 550oC mixtures of the monoclinic and tetragonal phases and 450oC crystallization of tetragonal phase. multi-level sintering for both 4 and 2 layer more homogeneous microstructure, the corrosion resistance and microhardness is higher than one level sintering. Regardless the type of the sintering, properties of the coating 4 layer is better than the 2 layer.

In this study, the effect of Friction Stir Welding (FSW) on the corrosion behavior of 1050 aluminium alloy in 3.5 wt.% NaCl solution was investigated. Is so doing, 1050 aluminium alloy was welded with the rotational speed of 250, 500 and 1000 rpm and traveling speeds of 14 and 56 mm per minute. The microstructure of 1050 aluminium al and welded 1050 aluminium alloy was examined by X-ray diffraction. Corrosion behavior of the samples was evaluated in 3.5 wt.% NaCl solution using Tafel polarization tests and electrochemical impedance spectroscopy. The results showed that Friction Stir Welding (FSW) decreases the grain size of 1050 aluminium al and improve the corrosion resistance of stir zone. X-ray diffraction pattern was similar for 1050 aluminium alloy and welded samples indicating the absence of unwanted phases in the structure. Given the curves of Tafel polarization and the results from modeling through electrical equivalent circuit expressed that for 1050 aluminium alloy welded by FSW with pin travelling speed equaled to 56 mm per minute with rotating speed equaled to 500 rpm, the most polarization resistance was obtained and it has also shown the least hardness in the hardness test compared to the other samples.

Utilizing the sol–gel method, Al-Ti codoped ZnO (ATZO) nanostructured thin films were synthesized. The X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) methods were used to investigate the structure, morphology and surface roughness of the thin films. From XRD patterns, it was found that reducing atmosphere causes an improvement in the crystallinity of the ATZO thin film. The post annealing process in the reducing atmosphere of 95 % N2-5% H2 has revealed that cause a significant reduction of the resistivity from 13´106 Wcm to.006´106 Wcm, along with an increase in transmittance from 86.39% to 88.41%. It was observed that the grain size varies from 23 nm to 29 nm and RMS roughness of the thin films were found to be around 8 nm. According to their optical transparency and resistivity values, ATZO nanostructured thin films can be used in thin film transistors (TFTs).

In this research, alumina - titania nanoparticles in thin-film forms and in different alcoholic environments such as ethanol, butanol and isopropanol were coated on API5-GrB steel substrates by electrophoretic process. coating operations was performed at different voltages, as well as chronoamperometry method was used to investigation of the mechanism of nucleation and surface qualities of coatings. in order to measurement of coating thickness and adhesion to the substrate, optical microscope was used. in the measurment the weight of the coating test showed that the weight of the coating increased via increasing voltage. by applying low voltage, the highest coverage was created in the presence of the butanol suspension, but via increasing the voltage, the maximum coverage was formed in the presence of the ethanol suspension. in the measurement results of coatings weight and their quality viewing showed that coating weight changes with voltage (electrical field intensity) and time follow the Hamaker relationship.

Self-lubricating coatings are one of the conventional protective coatings in aerospace and power plant industries which have the suitable stability and performance at high temperature. In this research, co-deposition of alumina and silver particles within Ni-P electroless coating were implemented on mild carbon steel substrate. The effect of heat treatment on the hardness of the coatings was investigated and morphology and cross section of the coatings were evaluated by Scanning Electron Microscopy (SEM). The tribological behavior of the coatings was evaluated by pin-on disc method and by using 52100 steel pins at ambient and high temperature and the wear rate was measured by 3d optical profiler. Also, lubrication mechanism was investigated by using energy dispersive spectroscopy analysis (EDS) and wear track micrographs. The results showed that the wear resistance and lubrication of Ni-P-Ag-Al2O3 hybrid coating were increased simultaneously and high temperature self-lubricating characteristics of the hybrid coating have been enhanced by the diffusion of silver through the coating and the production of silver-rich tribofilms.

In this report, we explained the formation and characterization of high-porosity, uniform, and stable porous silicon (PS) layers. An innovative combination of electroless and electrochemical etching of silicon was introduced using a novel parameter of delay time (Td). The electroless chemical etching was optimized by varying the delay time (Td) prior to the electrochemical process to control the uniformity of the pores. The porosity and uniformity of PS samples were enhanced by applying the optimized value of delay time. The PL spectra of porous samples were measured in room temperature. The optimized sample showed the most intense PL peak compare to the other porous samples due to its highest porosity and elevated specific surface area which enhanced the absorption coefficient of this porous surface. The optical characteristics of the optimized sample indicated the highest porosity of this sample due to the application of sufficient duration of electroless chemical etching prior to applying the pulsed current. It was found that the performance of the photo detector on optimized PS sample is much better than the other porous samples.

Application of cermet coating deposited by High-Velocity Oxygen Fuel (HVOF) has received considerable attention in a variety of industries, nowadays. Since the surface roughness of carbide coatings is higher than the permissible limits under specific conditions, finishing the coated surface by grinding is essential in order to achieve the desired roughness. The present study investigates the effect of simultaneous changes in the grinding parameters including depth of cut, feedrate and cutting speed on the adhesion and cohesion strength of WC-10Co-4Cr coating by HVOF. A full factorial design of experiment was selected for experimental planning and the analysis of variance was employed to find the significant grinding parameters, forthe first time. The adhesive and cohesive properties were measured using fracture toughness with Vickers’ Indentation Test. The results showed that adhesion and cohesion strength of WC-10Co-4Cr coating increased after grinding process, and they increased with the increase of the depth of cut and feedrate and the decrease of the cutting speed. The most influencing parameters were the depth of cut, feedrate and cutting speed respectively. At the end of the current study, the relation between the grinding parameters and adhesive and cohesive propertieshas been modeled using regression analysis.

In this research Co-Cu/Cu and Fe-Co-Cu/Cu multilayer were electrodeposited on sputtered gold on glass substrates. The kinetic roughening of samples was investigated by atomic force microscopy (AFM) images and the logarithmic scale plots of roughness as a function of scan lengths. The XRD patterns indicate the multilayer thin films follow their substrate textures. The EDX results show that in both Co-Cu/Cu and Fe-Co-Cu/Cu multilayers the Co content increases as the magnetic layer thickness increasing. The SEM images show that increasing the magnetic and nonmagnetic layers thicknesses leads to increase the grain size of multilayers. The Magnetic property studies of samples reveal that the coercivity decreases and the remanence increases by presenting of Fe in magnetic multilayers.

In this paper, transparent conductive SnO2/Ag/MoO3 (SAM) multilayer system is designed and optimum thicknesses of each layer are calculated to achieve high optical transmittance and low sheet resistance simultaneously. SAM nanostructured films were deposited on glass substrate by thermal evaporation technique and then were annealed in air atmosphere at 150oC for 1 hour. We investigated some electrical, optical and structural properties of this multilayer system such as sheet resistance, optical transmittance, reflectance, figure of merit and surface roughness. High quality SAM layers with a low sheet resistance of 12.5 (W/ð) and the maximum optical transmittance of 90% in visible wavelength region were obtained for the optimized SAM system. The crystallite size of SnO2 and Ag were estimated about 27 (1) and 19 (5) nm, respectively, using diffraction analysis. Low electrical resistivity and high optical transmittance make it possible to use these layers as transparent electrode in optoelectronics applications. The results show that the fabricated photovoltaic cells on SAM multilayer system have higher power conversion efficiency compared to that fabricated on the conventional ITO films.