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In this research, coal tar and soft bitumen were used as raw materials and the low-cost liquid phase carbonization (LCP) method was employed to synthesize mesophase carbon microbeads. First, the effect of temperature, time, and various pressures on the synthesis of mesophase bitumen was investigated. Also, the effect of various solvents on the synthesis efficiency of mesophase carbon microbeads was evaluated. The structural and chemical characteristics of the mesophase carbon microbeads were evaluated using field emission scanning electron Microscopy (FESEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The results showed that the pressure of 7 bar and extraction with solvent of pyridine had a great effect on the morphology, removal of impurities in raw materials, and production efficiency. Also, the results of XRD and SEM revealed that mesophase carbon microbeads were not always spherical in shape. [ABSTRACT FROM AUTHOR]

Background and Objective: In the present research, the synthesis and characterization of ZnS nanoparticles in zinc blend crystallite phase via hydrothermal method were reported. Advanced oxidation processes using nanophotocatalysts are one of the most efficient methods for removing the dyes with complex organic compounds from textile and industrial wastewaters. The photocatalytic performance of nanoparticles is drastically affected by their structural and optical properties. One of the most important features affecting the photocatalytic degradation of nanoparticles is their optical bandgap width, which is an important factor in the radiant photons in the visible and UV region and the production of active radicals to destroy the complex carbon pollutants. The optical bandgap width, like other properties of nanoparticles is affected by three important geometric parameters, including particle size, dimension and shape. It is also a function of synthetic chemistry, i.e. the precursors and the fabrication methods. The aim of the present study was to investigate the nanostructure of zinc-sulfide synthesized nanoparticles, optical properties and photocatalytic effect on the degradation of Methylene Orange dye. Materials and Methods: The experiment of degradation of dye consisted of 70 mg of synthesized nanoparticles in 100 mL of dye solution containing 3.75 ppm of Methylene Orange dye at pH = 5.5. The experimental steps were repeated three times. Nanostructure characterization of three-dimension ZnS nanoparticles was specified by X-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy, Furrier transform infrared, ultraviolet-visible spectroscopy and N2 adsorption-desorption. Results: The lattice characteristics such as density, specific surface area, size, strain, stress and deformation energy density are specified using Williamson-Hall (W-H) and Halder-Wagner (H-W) analysis. The photocatalytic degradation rate (k) of Methylene Orange was calculated to be 0.052 1/min, whilst after 60 minutes about 95% of the dye was photodegraded. The N2 adsorption-desorption calculations determined the mean pore diameter, specific surface area (SBET) and total porosity volume as 20.69 nm, 19.12 m²/g and 0.065 m³/g, respectively. The bandgap of fabrication ZnS has been evaluated from the Tauc's equation to be 3.47 eV. Compared with ZnS nanoparticles made by the hydrothermal method in the wurtzite crystallite phase (sample 2), the synthesized sample (sample 1) shows less lattice strain and stress, less crystallite size and also revealed the higher photocatalytic activity. Conclusion: The pure zinc-sulfide nanoparticles without metal or ceramic dopants in the cubic zinc-blend crystallite phase are synthesized using the hydrothermal method. The precursors used in the synthesis of zinc-sulfide nanoparticles include zinc chloride and thioacetamide in the presence of oleic acid as a collecting agent. High photocatalytic activity of ZnS nanoparticles was confirmed by the degradation or dechlorination of Methylene Orange solution under UV light irradiation. Compared to similar studies, the results show that reducing the optical bandgap from 3.84 eV to 3.47 eV increases the degradation rate from 0.031 to 0.052. In this study, it was shown that synthesized zinc-sulfide nanoparticles by hydrothermal method, was able to decrease optical gap bandwidth and subsequently increased photocatalytic activity. [ABSTRACT FROM AUTHOR]

Introduction: Nowadays, the heavy metals pollution is one of the most important environmental problems. Due to the high cost of common refining methods, the use of microbial biomass is recommended to clean up heavy metals. The aim of this study was to evaluate the interactions of Rhodoterula toruloides strain IR-1395 with mercury. Materials and methods: In this study, the growth rate and types of interactions of the strain IR1395 with mercury in the Sucrose Broth medium were investigated and the amount of mercury accumulated was measured using the Spectrophotometry method. Then, in order to determine the best biosorption conditions, the effect of parameters such as pH, mercury concentration, biomass concentration, contact time, and the temperature was measured. Also, the biosorption was investigated by treated cells with 2,4 dinitrophenol and autoclave. Finally, the biosorbent was characterized by Scanning Electron Microscope equipped with Energy Dispersive X-Ray Analysis. Results: Studies have shown that the maximum growth rate of the strain IR-1395 was after 36 hours and then it entered the stationary phase. Also, this strain was able to the biosorption and bioaccumulation (61.86%) and 10.17% biovolatilization of mercury from the medium at the concentration of 10 mg/l of chloride mercury for seven days. In examining the factors affecting the mercury biosorption, it was indicated that the optimal pH was 4. The highest biosorption was observed at 300 mg/l of mercury in 10 minutes at 15 ˚C. In the study of the effect of 2,4- dinitrophenol treatment and autoclave, it was found that mercury adsorption has reduced by the treated yeast. Finally, the results of the EDX confirmed the biosorption of mercury by this yeast. Discussion and conclusion: By examining the types of interactions of the strain IR-1395 with mercury and its potential in biosorption, it was found that this strain is a valuable microorganism in mercury bioremediation processes from contaminated aquatic environments. [ABSTRACT FROM AUTHOR]

In this article, the effects of Pr and Nd were investigated on the microstructure and absorption/desorption characteristics of MmNi5 hydrogen storage alloy. The alloys were prepared in Vacuum induction furnace and the microstructures and phases were analyzed using scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDS) and X-ray diffraction (XRD). Hydrogen absorption/desorption characteristics was performed on Sievert apparatus. The results showed that the microstructure of the alloys consist of matrix, second phase as a result of Al segregation, porosities and cracks. The amount of second phases and Al in this phase in Mm(Pr,Nd)Ni4.7Al0.3 is less than MmNi4.7Al0.3. Al in Mm(Pr,Nd)Ni4.7Al0.3 were more homogenized. Pressure-Composition Isotherms of hydrogen absorption/desorption at 25˚C showed that for MmNi4.7Al0.3 and Mm(Nd,Pr)Ni4.7Al0.3, absorption pressures were 14.52 and 9.90 bar, desorption pressures were 5.53 and 5.49 bar, hydrogen storage capacities were 1.37 and 1.33 wt. % and hysteresis were 0.73 and 0.58, respectively. These results are useful in industrial applications, because of inconsiderable decrease in hydrogen storage capacity and the other positive variation in absorption/desorption characteristics, especially the hysteresis and absorption pressure. [ABSTRACT FROM AUTHOR]

Silver nanowires (AgNWs) are considered as one-dimensional nanostructures, which have received much attention due to their nanoscale size, high aspect ratio, high electrical and thermal conductivity, optical transparency and high mechanical stability. Preparation of AgNWs by polyol process is remarkably sensitive to the interactions between synthesis parameters. In this study, the effect of the simultaneous change of four synthetic parameters, namely the reaction temperature, the molecular weight of polyvinylpyrrolidone (PVP) stabilizer, the amount of sodium chloride, as well as, the solution mixing rate by the polyol process was reported. The results of field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) confirmed that the synthesized AgNWs were below 100 nm. X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis, as well as, Fourier transform infrared spectroscopy (FT-IR) confirmed that the formed AgNWs were free of impurities. It was also found that temperature, molecular weight of PVP, salt concentration and solution mixing rate caused a significant change in the morphology of AgNWs. More importantly, a strong interaction was created in the preparation process of AgNWs by adjusting the parameters. [ABSTRACT FROM AUTHOR]

Thermal spraying is an economical and rapid coating process that creates a rough and clean surface. As a result, it can be used for applying the interlayer in transient liquid phase bonding. In the present study, transient liquid phase bonding Al 2024 to Ti-6Al-4V was investigated using a brass interlayer, as well as thermal spray of brass on Al substrate. The results show that by using thermal spray coat as interlayer, because of the formation of different defects that can be considered as diffusion channels, diffusion potential of Ti and Al becomes higher at the interface. The mechanism of bonding formation involves the diffusion of Cu into Al and Ti base materials and formation of TiAl3, TiAl, Al2Cu, and AlCuMg phases and also diffusion of Cu through Al grain boundaries and formation of eutectic phases across the grain boundaries. The formation of these intermetallic phases was confirmed by energy dispersive spectroscopy and X-ray diffraction. Dissolution of the base metals in the joint area and the isothermal solidification process of the thermal sprayed interlayer is more and faster than the foil interlayer. The joint with thermal spray brass coat as interlayer gives higher shear strength of 25MPa in comparison with the case of using brass foil as interlayer (14.6MPa). The decrease in bond strength can be attributed to aggregation and growth of the brittle intermetallics near the joint interface due to lower diffusion potential of Al and Ti in the joint zone. [ABSTRACT FROM AUTHOR]

In this research, the effect of temperature and time on the properties of AISI420/SAF2507 dissimilar joint produced by transient litpd phase bonding process was investigated. A BNi-2 interlayer witb 25 pm thickness was inserted between two dissimilar steel samples. The bonding process was performed at 1050 oC and 1100 oC for different bonding times. The microstructures of the joints were studied using optical microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. Microhardness and tensile shear strength of bonded samples were investigated. Isothermal solidification was completed for the joints bonded at 1050 oC and 1100 oC for 45 min and 30 min, respectively. ASZ and ISZ areas of the bonding zone at the bonding temperature of 1050 oC indicated the highest (520 HV) and the lowest (300 HV) microhardness values, respectively. Sample bonded at 1050 oC for 1 min indicated the lowest tensile strength (196 MPa) and sample bonded at 1100 oC for 60 min indicated the highest tensile strength (517 MPa). [ABSTRACT FROM AUTHOR]

Practical applications of thermal barrier coatings with aluminide bond-coats are limited due to oxide scale spallation of the aluminide coating under applied thermal stresses. Considering the positive effects of oxygen-active elements or their oxides on the high temperature oxidation behavior, in this research zirconia was introduced into an aluminide coating. For this purpose, a Watts type bath was used to electroplate a layer of Ni-ZrO2 composite on a Ni-based substrate. Aluminizing was performed using the conventional two-step process at 760 and 1080C. Microstructural characterization of coatings in the ascoated conditions and after cyclic oxidation via 5-hour cycles at 1050 C was performed using electron microscopy, energy dispersive spectroscopy and X-ray diffractometry. The results showed that the general three-zone microstructure of the simple high activity aluminide coatings develops below the pre-deposited nickel-zirconia layer and latter converts to a nearly un-alloyed porous NiAl. In spite of its porous surface layer, the zirconia modified coating has a higher oxidation resistance than the unmodified aluminide coating. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) is one of the most widely used solid lubricants. In this study, MoS2-Cr composite coatings were deposited onto AISI 1045 steel substrates by direct-current magnetron sputtering. The MoS2/Cr ratio in the coatings was controlled by sputtering the composite targets. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and nano-indentation and nano-scratch techniques. The tribological behavior of the coatings was investigated using the pin-on-disc test at room temperature. The results showed that the thickness and the hardness of the coating were 6 μmand 850-1300 HV, respectively. The degree of the crystallization of the composite coatings was enhanced with increasing the Cr contents. The incorporation of Cr into MoSx coatings resulted in the considerable improvement of coating adhesion and hardness. The optimum doping level for MoS2-Cr coatings to show the best tribological propertie was 13 atomic percent. The main wear mechanisms of the coating were delamination, tribochemical and abrasive micro cracking. [ABSTRACT FROM AUTHOR]