IRANIAN JOURNAL OF SURFACE SCIENCE AND ENGINEERING
Year:2016 | Volume:12 | Issue:29|Papers Count:10

Production of nonmaterial by an appropriate price and good quality is the main problem in using of nanotechnology. For achieving this discipline, present study proposed a simple and cost effect method. Nanocomposites of bentonite/titanium dioxide nanocomposites were synthesized for using as an antibacterial material by a prompt and simple alkaline ion exchange method. The preparation of nanocomposite was achieved by heating a mixture of TiO2 and bentonite at 500, 600 and 700oC for 30 and 60 minute. For synthesis of these nanocomposites, no reduction agent or chemical material not used except TiO2 and bentonite. The nanocomposites were characterized by XRD, XRF, SEM and DRS. SEM observations confirmed the formation of TiO2 particles on the clay surfaces with the mean average size of about 96.7-99.6 nm at less than 60 min. The XRD analysis showed the presence of anatase structure of TiO2 nanoparticles within the clay mineral layers. The Nano composite have antibacterial effect on the S. aureus and E. coli bacteria.

In this research, by spin coating, a layer of conductive poly (3, 4-ethylene dioxythiophene) (PEDOT) synthesized via in situ polymerization of 3, 4-ethylene dioxythiophene (EDOT) was coated on poly (methyl methacrylate) (PMMA) substrate. The effect of different factors such as time and temperature of curing, speed of spin coating on the structural, electrical and mechanical properties of coated layer were characterized by FT-IR and UV-Vis spectroscopy, conductive measurements and tape test. Theresults revealed that a surface with good conductivity (61.38 kW) and excellent transparency with an excellent adhesion was obtained which can be useful for anti-static application. Also these data show that the resistance of the prepared coating is less than 108W and since the decrease of polymer electrical resistance to108 W or less, can reduce the accumulation of static electricity on the surface of the polymer, therefore, this coating has the ability to reduce accumulation of static electricity.

In this study the surface of WC powder particles coated by Ni-P electroless process and the effect of powder proportion immersed in Ni-P electroless bath and the activation pretreatment on the Nickel content was evaluated by X-Ray florescence analysis. To investigate the effect of powder proportion immersed in electroless bath, the activated powder with concentrations of 20 and 40 g/lit was added in electroless bath and the weight percent of Ni assessed to be 14.1 and 7.5% respectively. To evaluate the effect of activation process, WC powder with concentration of 20 g/lit was immersed in Ni-P electroless bath with and without activation process. By applying the activation process, the weight percent of Ni increased about 27%. An equation was proved to estimate the thickness of electroless layer. In this approach, the thickness of electroless layer in E20, E20P andE40P samples was calculated 0.08, 1.1 and 0.05 mm respectively. In XRD pattern of Ni-P coated WC, the W2C peaks were exhibited, because of the diffusion of hydrogen in structural defects.

The purpose of this research is investigation of two fine grained stainless steel coatings produced by two physical vapor deposition methods, i.e. magnetron sputtering and cathodic arc evaporation, on a carbon steel substrate. The coatings were compared according to their structure, hardness and adhesion. In order to evaporate the target atoms, high power (3300 w) was applied on the cathode surface in cathodic arc evaporation method and argon pressure (105 Pa) was used in magnetron sputtering method. For comparison of these coatings, the same substrate temperature (300±50oC) and bias voltage (250±50 V) and also similar deposition time (50 min) were used. XRD, EDS, SEM and FE-SEM methods were used for characterization of the coatings. Nano-indention and Vickers indenter tests were also carried out for evolving the hardness and adhesion of the coatings. The EDS analysis results showed that the magnetron sputtered coating had a composition similar to the target material, whereas the cathodic arc evaporation coating had a different composition. Also, the nano-indention test showed that the magnetron sputtered coating hardness increased up to about 890 Vickers, which is much higher than that of the cathodic arc coating (about 260 Vickers) and bulk 304 stainless steel (220 Vickers), due to its nano-crystalline structure. However, the sputtered coating adhesion was evaluated weaker than that of the cathodic arc coating, because of the existence of more cracks at the edges and also local spalling of the coating.

In this Article, AZ31 magnesium alloy pre-sprayed with WC-10%Co-4%Cr powder after surface melting by pulsed Nd-YAG laser was investigated to improve corrosion resistance. Chemical composition, phase and microstructure of produced composite layer by this process were studied by scanning electron microscope equipped with energy dispersive spectroscopy and X-ray diffractometry. After laser treatment different intermetallic compounds such as Cr2O3, W2C were detected in produced composite layer. This layer mainly consist of tungsten carbide particles, chromium and cobalt in Mg matrix. In this article, beside of evaluation of corrosion properties, evaluating of hardness of produced layer of laser treatment showed that hardness of AZ31 magnesium alloy has increased from about 50±5 Vickers for base alloy to about 200±10 Vickers for layer produced by laser treatment. Corrosion behavior evaluation of laser treated layer and comparison with base alloy was done by polarization test in 3.5wt.% NaCl solution and by measurement of some parameters of polarization curves was determined that corrosion resistance of laser treated sample with WC-Co-Cr powder has increased three times in comparison with base alloy.

In this paper, the effect of aluminum addition on the tribological behavior of Hadfield steel in mild wear condition was investigated. The pin-on-disk test method was used on the different compositions of Hadfield steel that alloyed by three nominal compositions of zero, 1.5 and 3 weight percent of aluminum. The experimental induction furnace surrounded by Ar atmosphere and zirconia ceramic mold was used for melting and casting of samples. In the wear test, the grinding wheel as abrasive medium was used and the changes in the friction coefficient and the weight losses of specimens versus the sliding distance were measured. The tensile, hardness and impact tests were used for evaluation of mechanical properties. In addition, the microscopically studies on the deformed samples, worn surface and wear debris were done using optical and scanning electron microscopes. The results shown that in the low stress wear condition, the work-hardening of worn surface of Hadfield steel cannot well be activated, therefore it has not sufficient wear resistant. By addition of 3wt. % aluminum, the yield strength from 415MPa to 470MPa and hardness from 190HV to 215HV can be increased. In addition, depth of work-hardened on abrasive forces and worn surface hardness can be enhanced from 100mm to 200mm and from 340HV to 365HV in sequence. Thus the wear rate from 0.15mg/m to 0.11mg/m was decreased and wear resistance was improved up to 70%.

Nanostructures growth for a diamond lattice under oblique angle by Monte-Carlo method and random number generation are simulated. Nucleation stage have done by two kinds; square and triangular. At nucleation stage, interactions between particles have chosen at first Lennard-Jones and then Tressof. With variation potential from Lennard-Jones to Terssof, surface roughness decreases for both square and triangular nucleation. Oblique angle effect on growth is studied by packing density and surface roughness. Our results showed that with increasing incident angle, packing density decreases and surface roughness increases.

A composite clad layer of stellite6 matrix was fabricated on plain steel and the effect of B4C reinforcing particles on microstructure characteristics, hardness and wear behavior was investigated. For this purpose B4C powder with different weight percentages were pasted on substrates and subsequently melted by GTAW using stellite6 filler. Microstructural investigations of clad layers were conducted by optical microscopy (OM) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometery (EDS). X-ray diffractometery (XRD) was used for structural evaluation of clad layers. Hardness and wear behavior were studied by micro hardness testing and pin on disk wear test, respectively. The results showed that the clad layer mostly g contain g cobalt-rich matrix, eutectic carbides such as Cr7C3 and Cr23C6 relating to the matrix and secondary phases such as CoB2, CrB2, WC and W2B resulted from the reaction of B and C with other elements after decomposition of B4C. By the addition of B4C content in the clad layer a finer dendritic structure with more interdendritic phases was obtained. Moreover, composite clad layers exhibited higher hardness compared to stellite6 clad layer. Wear mechanism of stellite6/B4C composite clad layers was delamination and the stellite-20 wt.% B4C showed the least wear rate.

In this study, in order to improve surface properties of 316 austenitic stainless steel and its erosive properties, nanostructured TiN layers by PACVD method were developed. The TiN coatings were deposited on AISI 316 austenitic stainless at three different temperatures 470, 490 and 510oC and duty cycle 33% by means of PACVD method. Microstructure and cavitation resistance were characterized by techniques such as field emission scanning electron microscopy (FE-SEM), XRD, micro hardness, erosion tests. The results indicated that with increasing deposition temperature from 470 to 510oC, grain size of coating increased from 12 to 47 nm. It was found that at 470oC, has the best erosive properties.