IRANIAN JOURNAL OF SURFACE SCIENCE AND ENGINEERING
Year:2018 | Volume:14 | Issue:36|Papers Count:9

In this study, synthesis and characterization of ZnO/silica gel photo catalyst for degradation of the methyl orange from wastewaters were investigated. For this purpose, ZnO/Silica composite was prepared by immersing silica gel in the zinc chloride molten bath at a temperature of 560 ⁰ C for 20, 40, 60 and 90 minutes. For synthesis of these composites, no reducing agent or chemical agent was used except zinc chloride. In this method, synthesis of nanoparticles and their immobilization on the substrate was done instantly. The synthesized composites were characterized by XRD, SEM and DRS analysis. The scanning electron microscope (SEM) pictures showed that ZnO nanoparticles were formed on the silica gel surface as a thin layer by using a molten salt process. The results indicate the formation of ZnO layer on the silica surface in the form of flat films, which at longer times the film thickness increases while after 60 minutes produced a number of visible nanoparticles. XRD patterns indicated amorphous structure of silica gel and the crystalline structure of ZnO nanoparticles. In addition, the stability of synthetized nanocomposites was confirmed by water leaching test. Finally, the photocatalytic activity of the composites was assayed against methyl orange dye. The decolorization efficiency of prepared composites of 20, 40 and 60 min was close together and about 39. 9, 40. 6 and 41. 3%, respectively.

In this study, the few-layer graphene foam (GF) was synthesized by chemical vapor deposition (CVD) method and the effect of methane concentration and the synthesizing temperature on the number of GF layer have been studied. With methane concentration changing as 0. 5, 0. 6, 0. 7, 1 and 1. 5 sccm (standard cubic centimeters per minute) the 2, 4, 6, 11 and 25 layer graphene foam was obtained, respectively. The CVD synthesizing temperature also was studied and by changing the temperature as 900, 1000 and 1120˚ C, the 23, 10 and 6 layer GF was synthesized. The images of scanning electron microscopy (SEM) showed the good quality of porous structure of synthesized GF. Raman analysis was used to confirm the formation of graphene foam and to find the relationship between the methane concentration and the synthesizing temperature (as synthesizing conditions) and layers number of GF. The obtained results from Raman analysis showed that the methane concentration and synthesizing temperature are important parameters for formation of few-layer GF. The two-layer GF was synthesized by decreasing the concentration of methane to 0. 6 sccm and increasing the temperature to 1120 ˚ C.

In this study, Al/(SiC+BNh) hybrid composite was produced on the surface of Al-1050 substrate via friction stir processing to achieve the high hardness of SiC particle and lubricating property of BNh simultaneously. Microstructural studies revealed that grain refinement was occurred in the stir zone (22% reduction of grain size in comparison to base metal). Closer microstructural studies by using scanning electron microscope equipped to Map-EDS analyzer illustrate the relatively uniform distribution of SiC and BNh particles in the Al-1050 matrix. Microstructural studies indicated that increasing FSP passes increased the grain sizes of TMAZ and HAZ more than 20% of base metal grain size. Microhardness evaluation showed that increasing the number of FSP passes resulted in increasing hardness of stir zone (100± 5HV in 8 pass sample in comparison with 60± 5 in 1 pass sample) that was ~70% more than hardness of base metal.

Acrylic-based polymer coatings are of paramount importance owing to their versatile potential applications. In order to improve various properties of such coatings, different attempts are usually carried out, among which is to employ nanoparticles, which results in nanostructured acrylic coatings. In this study, the effect of silica nanoparticles on emulsion polymerization reaction and surface interaction of nanoparticles with latex particles has been investigated. In addition, the effect of silica nanoparticles on final conversion percentage, reaction coagulum percentage and particle size and distribution of latex has been evaluated. The results of dynamic light scattering analysis showed a change in the size of polymer particles along with a change in the concentration of silica nanoparticles. Therefore, the addition of silica nanoparticles during the emulsion polymerization reaction broadens the size distribution of the latex particles. In all synthesized samples, in spite of the presence of silica nanoparticles, the conversion percentage was higher than 95%, and the amount of coagulum was less than 0. 2%, indicating the choice of suitable formulation and favorable conditions. Subsequently, the synthesized latex film was made; Cross-Cut adhesion tests, pencil hardness, and contact angle were used to study the surface properties of the nanocomposite.

Typically polyurethane coatings are used to protect oil and gas transmission pipelines against corrosion. In order to increase the protection efficiency and prevent corrosion problems, the pipelines are cathodically protect. The major problem of the polymeric coatings under cathodic protection is reducing the adhesion of the coating at the interface with the metal surface, and as a result, the cathodic disbondment of the coating, due to the formation of corrosion products as well as the accumulation of hydrogen in the interface would be occurred. In this study, to improve the resistance against the cathodic disbondment of the polyurethane coating, before applying the polyurethane coating on the metal surface, a layer of ethylcellulose nanofibers has been applied on an API X52 steel substrates. In order to compare the cathodic disbondment of the ethylcellulose nanofibers /polyurethane nanocomposite coatings with polyurethane coating, ASTM G8-96 method at different time intervals has been used and the disbondment of the coatings has been calculated. In addition, electrochemical impedance spectroscopy analysis has been used at different interval times on coated specimens. The results obtained revealed that the ethylcellulose nanofibers /polyurethane nanocomposite coatings is more resistance to cathodic disbondment compared to polyurethane coating.

In this research, wear mechanisms and tribological properties of Ni-P and Ni-P-Ag electroless coatings at high temperatures have been studied. At First, the surface of carbon steel samples were prepared and then they were entered into the Nickel phosphorus electroless bath (with and without silver particles) to deposit Ni-P-Ag and Ni-P coatings on the substrates. After heat treatment at 400 ° C, the hardness of the coatings was measured using a microhardness tester and the tribological tests were implemented by Pin on disc method at 500 ° C. The microstructure of the coatings was also evaluated by XRD analysis and the surface morphology, cross-section and wear scars of the coatings were studied by using an optical microscope a scanning electron microscope equipped with EDS analyzer. The results showed that the co-deposition of silver particles in Ni-P coating led to the self-lubricating property as the result of the formation of silver rich tribofilms. It can be related to the diffusion of silver toward the sliding surface of Ni– P– Ag coating at high temperatures. Also, abrasive wear, surface oxidation and the plastic deformation were also recognized as the high temperature wear mechanisms in Ni-P-Ag coating.

AISI 1045 steel substrate was pack-chromized for 6hr at 900, 1000 and 1100° C. Pack chromizing was also carried out by applying direct current field between the treated sample and the powder agents (current of 4. 5 A and voltage of 20 V). The treated layers were studied by optical and scanning electron microscopes as well as Xray diffraction technique. Subsequently, in order to evaluate the hardness of the layer, Vickers micro hardness tests were carried out under an applied load of 25 gF. The results showed that by applying direct current field during chromizing, thickness and uniformity of the treated layers are increased. The hardness of the coatings was also increased from 812 to 879 Vickers.

In this study, a rolled AA3003-H14 Aluminum alloy sheet and the titanium metal powder were used to fabricate a surface composite reinforced with in-situ formed Al3Ti aluminide nanoparticles using friction stir processing technique. The hardness and the wear behavior of the FSPed composite and the base metal were determined after six passes FSP. The phase analysis was done using X-ray diffraction (XRD) and the microstructural examinations were performed using an optical microscope (OM) and scanning electron microscope (SEM) equipped with microprobe elemental analysis. Microstructural studies revealed that FSP has resulted in grain refinement, uniform distribution of reinforcing particles, and in-situ formation of Al3Ti aluminide nanoparticles at the interface between the Al-matrix and the Ti particles. The hardness and the wear resistance of the FSPed composite exhibited considerable improvement in comparison with the base metal. The dominant wear mechanisms identified as severe adhesive wear for the base metal, and mild adhesive and abrasive wear for the FSPed composite, respectively.

Erosion behavior and microstructure of the weld metal in the HSLA-100 steel joints were studies. The Welding of the alloy carried out by GTAW method with electromagnetic vibration simultaneously. The microstructure investigations were done by optical and SEM microscopy. Erosion test with slurry(water+5% sand) at the time from 0. 5 to 2 hours, 10 ms-1 speed, impact angles 30, 90 was carried out. The results shows that by applying electromagnetic vibration the microstructure shifts from Quasi polygonal ferrite with austnaite-martensite (M A) coarse and coadunate islands to the acicular ferrite with the finer and more uniform distribution M A islands. It was revealed that the electromagnetic vibration causes improving the erosion behavior in the both impact angles, especially 90 degree. The best erosion behavior (lower erosion rate and least weight drop) of weld metal was obtained under vibration of 30 volts. The erosion dominate mechanism were recognized plowing and plastic deformation, forming and separating of the metallic particle, for 30 and 90 angles, respectively.