Sharif Digital Repository

In this study, the kinetics of aging in AA6061 and AA6061 with 5% volume fraction SiCp were studied and compared. The composite was first produced and homogenized using stir casting technique followed by hot extrusion with the ratio of 18:1. Then, both AA6061 and the composite were aged at three different temperatures including room temperature, 170 °C and 240 °C, while mechanical properties during aging were evaluated employing hardness measurements and tensile testing. Moreover, in order to assess the effect of plastic deformation on the kinetics of aging, a series of samples were first deformed by equal-channel angular pressing immediately after solution treatment and then aged in the... 

In this research, submicron bioactive glass (BG) particles were synthesized by a sol-gel process and were then coated on a 316L stainless steel substrate using an electrophoretic deposition (EPD) technique. Stable suspension of bioactive glass powders in ethanol solvent was prepared by addition of triethanol amine (TEA), which increased zeta potential from 16.5 ± 1.6 to 20.3 ± 1.4 (mv). Thickness, structure and electrochemical behavior of the coating were characterized. SEM studies showed that increasing EPD voltage leads to a coating with more agglomerated particles, augmented porosity and micro cracks. The results of Fourier transformed infrared (FTIR) spectroscopy revealed the adsorption... 

Ferrite nanocrystals are an interesting material due to their rich physical properties. Here we add nonmagnetic dopants Zn and Cu to nickel ferrite nanocrystals, Ni1-xMxFe2O4 (0 ≤ x ≤ 1, M = Cu, Zn), and study how relevant properties of the samples are modified accordingly. Basically, these dopings cause a rearrangement of Fe +3 ions into the two preexisting octahedral and tetrahedral sites. In fact, this, we show, induces pertinent magnetic properties of the doped samples. In the case of the Cu-doping, the Jahn-Teller effect also emerges, which we identify through the Fourier Transform Infra-Red Spectroscopy of the samples. Moreover, we show an increase in the lattice parameters of the... 

An experimental study of wear characteristics of electroless Ni-10% P coating sliding against hard AISI 52100 steel pin is investigated. Experiments are carried out at room and 550°C temperatures. Heat treatment effects on tribological behavior of this coating are studied. The wear surface and the microstructure of the coatings are analyzed using optical microscopy, scanning electron microscopy, energy dispersion analysis X-ray, and microhardness testing equipment. It is observed that the forming of continuous oxide film on contacting surfaces of pin and disk improves wear resistance and decreases friction coefficient of the Ni-10% P coating. The results indicate that the wear resistance of... 

Effect of deformation path change on the static strain aging of low carbon steel was studied in this work. In the first stage, strip samples were subjected to cold rolling processes under different paths with the same total reduction in thickness while the deformation behaviors of the rolled samples were also evaluated using a mathematical analysis. Then, cold-rolled strips were aged in room temperature up to 45 days while hardness and tensile evaluations were performed to assess the mechanical properties of the as-rolled and the aged samples. Finally, the influence of rolling pass schedule on the subsequent strain aging phenomenon was investigated by means of the experimental results and... 

In this study, the effects of stress-assisted heat treatment on the microstructure and phase transformation of a Ti-rich (Ti-49.52 at.% Ni) shape memory alloy were investigated. For this purpose, the alloy was heat treated at temperature of 500 °C for 10 h under applied stresses of 100 and 200 MPa. XRD, TEM, and repeated thermal cycling were employed to study the microstructure and transformation behavior of the heat-treated materials. Room temperature XRD diffractogram of the stress-free heat-treated material showed a weak reflection of austenite (B2), while that for the stress-assisted heat-treated materials had a high intensity implying the presence of residual austenite in the... 

AISI 4340 steel bars were heated at 900 °C for one hour, annealed at 738 °C for different durations and oil-quenched in order to obtain dual phase steels with different ferrite volume fractions. A 3% prestrain at the temperature range of 150-450 °C was then imposed to the samples, and room temperature tensile tests were carried out, afterwards. Results indicate that the maximum values for both yield and ultimate tensile strength would exist for the samples pre-strained at the temperature range of 250-300 °C. Also, a sudden drop of the ductility was observed at the mentioned temperature range. The observed behavior might be attributed to the occurrence of dynamic strain aging taken place at... 

In the current study, the hybrid effect of a corona discharge and γ-alumina supported Ni catalysts in CO 2 reforming of methane is investigated. The study includes both purely catalytic operation in the temperature range of 923-1023 K, and hybrid catalytic-plasma operation of DC corona discharge reactor at room temperature and ambient pressure. The effect of feed flow rate, discharge power and Ni/γ-Al 2O 3 catalysts are studied. When CH 4/CO 2 ratio in the feed is 1/2, the syngas of low H 2/CO ratio at about 0.56 is obtained, which is a potential feedstock for synthesis of liquid hydrocarbons. Although Ni catalyst is only active above 573 K, presence of Ni catalysts in the cold corona plasma... 

While energy consumption is increasing worldwide due to population growth, the fossil fuels are unstable and exhaustible resources for establishing sustainable life. Using biodegradable compounds present in the wastewater produced in industrial process as a renewable source is an enchanting approach followed by scientists for maintaining a sustainable energy production to vanquish this problem for ulterior generations. In this research, bioelectricity generation with whey degradation was investigated in a two-chamber microbial fuel cell with humic acid as anodic electron mediator and a cathode compartment including combinational electron acceptor. Escherichia coli was able to use the... 

Graphene-tungsten oxide composite thin films with sheetlike surface morphology were fabricated and applied in photoinactivation of viruses under visible light irradiation. Using X-ray photoelectron spectroscopy, it was found that the chemically exfoliated graphene oxide sheets incorporated in the tungsten oxide film reduced through a visible light photocatalytic reduction. In addition, annealing the films at 450 °C in air resulted in formation of W-C and W-O-C bonds to obtain graphene-tungsten oxide composite films. The composite films fabricated by this method showed an excellent visible light photocatalytic performance in photoinactivation of bacteriophage MS2 viruses, as compared to... 

High-bainite dual phase (HBDP) steels with 34. vol.% ferrite were subjected to tensile strains of 1%, 3%, and 5% at intermediate temperatures (150-450. °C). Mechanical behavior of pre-deformed steels was then investigated at room temperature. A maximum value for both yield stress and ultimate tensile strength was observed for pre-deformed steels. A minimum elongation was also found in the same pre-deformed specimens at the range of 250-350. °C. It was found that dynamic strain aging (DSA) plays the major role in mechanical properties of pre-strained HBDP steels. The DSA indicator parameter (DSAP) was introduced to evaluate DSA mechanism. Maxima of DSAP were likewise observed at the range of... 

In this study, two different chemical solution methods were used to synthesize Zinc oxide nanostructures via a simple and fast microwave assisted method. Afterwards, the photocatalytic performances of the produced ZnO powders were investigated using methylene blue (MB) photodegradation with UV lamp irradiation. The obtained ZnO nanostructures showed spherical and flower-like morphologies. The average crystallite size of the flower-like and spherical nanostructures were determined to be about 55 nm and 28 nm, respectively. X-ray diffraction (XRD), scanning electronic microscopy (SEM), Brunauer-Emmett-Teller (BET), room temperature photoluminescence (RT-PL) and UV-vis analysis were used for... 

In this study, WO 3 nanocrystallites were first produced by laser ablation of W target in deionised water. To synthesize palladium, a PdCl 2 solution (0.2 g/L) was added to the liquid. Transmission electron microscope revealed successful synthesis of tungsten oxide nanocrystallites along with the production of Pd and core-shell Pd/WO3 nanoparticles. Gasochromic behavior was examined by hydrogen bubbling into Pd/WO 3 liquid in which a transition to blue absorbing state was observed. Optical absorption spectra of the colored liquid represented different sharp small polaron absorbing peaks below 3 eV and the peaks intensity was observed to be varied with Pd:WO 3 ratio. Time variations of... 

Two types of gold ores were subjected to iodide/iodine leaching at room temperature. The effects of three factors, including ore type (a carbonaceous and an oxide gold ores), iodide/iodine concentration, and the presence of oxygen in solution on gold leaching performance were investigated. The carbonaceous ore showed only 20% gold extraction, since gold-iodide complexes readily adsorb on organic matter. In contrast, gold extraction from the oxide ore in a solution containing 20 g/L iodide and 4 g/L iodine reached 77% in 6 h and 89% in 24 h. With iodate as the oxidant, no gold could be leached in 48 h. When the iodate was partially converted to iodine by adding HCl to the solution, gold... 

The properties of W-15 wt.%Cu composites were investigated by preparing two distinct composites of micrometer and nanoscale structures. Micrometer composite was produced by mixing elemental W and Cu powders and nanometer one was synthesized through a mechanochemical reaction between WO3 and CuO powders. Subsequent compaction and sintering process was performed to ensure maximum possible densification at 1000-1200 °C temperatures. Finally, the behavior of produced samples including relative density, hardness, compressive strength, electrical conductivity, coefficient of thermal expansion (CTE) and room temperature corrosion resistance were examined. Among the composites, nano-structured... 

The novel coumarin-3-carboxamides (=2-oxo-2H-1-benzopyran-3-carboxamides) 5a-5g containing lipophilic spacers were synthesized through the Ugi-four-component reaction (Scheme 1). The reactions of aromatic aldehydes 1, 4,4'-oxybis[benzenamine] or 4,4'-methylenebis[benzenamine] as diamine 2, coumarin-3-carboxylic acid (=2-oxo-2H-benzopyran-3-carboxylic acid; 3), and alkyl isocyanides 4 lead to the desired substituted coumarin-3-carboxamides 5a-5g at room temperature with high bond-forming efficiency. These novel coumarin derivatives exhibit brilliant fluorescence at 544 nm in CHCl 3  

CeO 2-TiO 2 nanoparticles were prepared by the sol-gel process using 2-hydroxylethylammonium formate as room-temperature ionic liquid and calcined at different temperatures (500-700°C). CeO 2-TiO 2-graphene nanocomposites were prepared by hydrothermal reaction of graphene oxide with CeO 2-TiO 2 nanoparticles in aqueous solution of ethanol. The photocatalysts were characterized by X-ray diffraction, BET surface area, diffuse reflectance spectroscopy, scanning electron microscopy, and Fourier transformed infrared techniques. The results demonstrate that the room-temperature ionic liquid inhibits the anatase-rutile phase transformation. This effect was promoted by addition of CeO 2 to TiO 2.... 

A severe plastic straining method, called constrained groove pressing, is used to improve the microstructure and mechanical properties of non-hardenable 3003 Al-Mn alloy. Williamson-Hall method is utilized to measure the grain size from X-ray diffraction patterns of deformed samples. The results show that ultra-fine grained 3003 alloy having grain size of 580 nm can be successfully produced by constrained groove pressing at room temperature. Mechanical properties of sheets, examined by tensile test, are approximately exhibited 170% improvement in comparison with those of annealed sample. Also, comparing the achieved results with those of aluminum 1100 alloy confirms the rapid rate of grain... 

In this paper, Ti-6Al-4V/TiC composite was fabricated by VIM furnace and graphite crucible. X-ray diffraction analysis and EDS techniques were used to identify the phases in the material. Microstructure characteristics of the Ti-6Al-4V/TiC composite were evaluated by means of optical microscopy. The tensile test was performed at room temperature after hot-rolling of the samples in the beta phase field. The results revealed that at different melting times, three kinds of precipitates are formed in the microstructure including grain boundary, eutectic and transgranular precipitates. The size of transgranular precipitates was significantly larger than that of the other two types of carbides and... 

The solubility of sulfur dioxide (SO2) and carbon dioxide (CO2) at P = 1 bar in a series of imidazolium-based room-temperature ionic liquids (RTILs) is calculated by Monte Carlo simulation in NPT ensemble using the OPLS-UA force field and Widom particle insertion method. The studied ILs were 1-butyl-3-methylimidazolium ([bmim]+) tetrafluoroborate ([BF4]-), [bmim]+ hexafluorophosphate ([PF 6]-), [bmim]+ bromide ([Br]-), [bmim]+ nitrate ([NO3]-), [bmim]+ bis-(trifluoromethyl) sulfonylimide ([Tf2N]-), and 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]). To validate the simulations, the liquid density of studied ILs and the solubility of CO2 in [bmim][PF6] was compared with...