Mehdi Alizadeh

Concurrent fitness evaluations in searching for the optimal process conditions of Al matrix nanocomposites by linearly decreasing weight

In this article, the effect of nanoceramic reinforcements on the mechanical properties of aluminum matrix composites was critically reviewed. Reinforcement of an Al alloy with nanoceramic particulates is expected to improve its tensile strength. This article also reports the role of an integrated optimization approach using an artificial neural network and a modified particle swarm to solve a process parameter design problem in casting of this class of metal matrix nanocomposites. The artificial neural network is used to obtain the relationships between decision variables and the performance measures of interest, while the particle swarm is used to perform the optimization with multiple objectives.

Preparation and characterization of in situ chitosan/polyethylene glycol fumarate/thymol hydrogel as an effective wound dressing

In the present study, polyethylene glycol fumarate (PEGF) was synthesized as a component of blend solutions via polycondensation polymerization and characterized by different tests in order to determine its functional groups and its physical properties included melting and crystallization temperature, enthalpy of fusion and average molecular weights. Wound dressing films based on chitosan (Ch), PEGF and thymol (Th) were fabricated by solvent casting method with different formulations contained 80%(w/w) chitosan and 20%(w/w) PEGF as polymeric components and different amounts of thymol consisted of 0, 0.6, 1.2 and 1.8%(v/v) as pharmaceutical additives of blend solutions. These films were evaluated by different essential tests included Fourier transform infrared spectroscopy (FTIR), tensile testing, water vapor transmission rate (WVTR), water vapor uptake, equilibrium water uptake, water solubility, swelling, scanning electron microscopy (SEM) and antibacterial activity tests. The blend film contained 1.8%(v/v) thymol demonstrated optimal properties included acceptable mechanical properties, better absorption of water vapor or liquid water, higher water vapor transmission rate and air permeability, acceptable water solubility, superior swelling level, more porous structures and rough surfaces and the excellent antibacterial activity against both gram-negative and gram-positive bacteria which make it a suitable candidate for wound dressing applications.

Fluid flow characterization of liquid–liquid mixing in mixer-settler

Agitation in a mixer-settler is one of the most common operations, yet presents one of the greatest challenges in the area of computer simulation. Mixer-settlers typically contain an impeller mounted on a shaft, and optionally can contain baffles. The hydrodynamic characteristics of mixer-settlers have been studied in the present study. The effect of different geometrical parameters on the efficiency characteristics of the system has been investigated. The effects of different width of impellers, impeller speed, inlet velocity, impeller diameter, etc. have been studied. Computational fluid dynamics (CFD) model has been developed to predict the efficiency characteristics. The model has been validated with the help of experimental data for different velocity outlets used in the work. This work has enabled developing efficiency that can produce higher condition than those reported in previous literature. From the CFD simulations results, optimum mixer-settler geometry has been proposed.

The Relationship Between the Synthesis and Morphology of SnO2-Ag2O Nanocomposite

There are various methods for synthesizing SnO2-Ag2O nanocomposite such as chemical vapor deposition, coprecipitation, spray-pyrolysis, sol-gel, laser ablation, hydrothermal routes, and so on. In this study, SnO2-Ag2O nanocomposite powders have been synthesized by sol-gel method using NH3OH/NaOH route. The obtained powders were characterized by scanning electron microscopy, X-ray Diffraction, X-ray fluorescence, and Fourier transform infrared spectroscopy. Monodispersed SnO2-Ag2O nanosized composite ranging from 80 to 400 nm in size in the NH3OH/NaOH route was obtained when the gel was heat-treated at different temperatures. Finally, it was found that optimum uniform distribution of the silver in SnO2 could be achived at an annealing temperature of 400°C.

Influence of Thermal Hydrogen Treatment of Titanium Particles on Powder Metallurgical Processing of NiTi-SMA

Powder metallurgy methods have been extensively used for producing near-net-shape components of NiTi shape memory alloys in recent years. The main drawback of these methods is the formation of undesirable phases and intermetallics, such as NiTi2, Ni3Ti, and oxide phases during sintering process. In this research, it is attempted to improve production of NiTi parts by pre–heat treatment of titanium powder under hydrogen atmosphere at temperatures between 100 and 300°C. Results show that heat treatment could change the microstructure and facilitate martensitic transformation of sintered NiTi specimens and reduction of Ni3Ti3O oxide phase.

Fluid Flow and Mixing in Non-Isothermal Water Model of Continuous Casting Tundish

Fluid flow and mixing of molten steel in a twin-slab-strand continuous casting tundish were investigated using a mixing model under non-isothermal conditions, This model led to a set of ordinary differential equations that were solved with a Runge-Kutta algorithm. Steady state water modeling was carried out under non-isothermal conditions. Experimental data obtained from the water model were used to calibrate the mixing model. Owing to the presence of a mixed convection in the non-isothermal conditions, a channelizing flow would be created in the fluid inside the tundish. A mixing model was designed that was capable of predicting RTD (residence time distribution) curves for different cases in non-isothermal conditions. The relationship between RTD parameters and the Tu (tundish Richardson number) was obtained for various cases under non-isothermal conditions. The results show that the RTD parameters were completely different under isothermal and non-isothermal conditions. The comparison of the RTD curves between the isothermal and non-isothermal conditions presents that the extent of mixing in the tundish in non-isothermal conditions is lower than the mixing extent in isothermal conditions.

Biosynthesis of Ag/MWf-CNT Nanocomposites Using Aspergillus fumigatus as the CO Oxidation Catalyst

In this research, the biosynthesis process of an Ag nanoparticles/multiwalled carbon nanotubes (Ag/MWf-CNT) catalyst system has been investigated by Aspergillus fumigatus fungus. Characteristic peaks of pure silver and FCC crystallization systems were characterized by X-ray diffraction pattern. TEM images show a well-dispersed spherical silver nanoparticles (≤10 nm) on the carbon nanotubes. Based on the results, reduction of silver ions is mainly dependent on the biomass weight applied in the biosynthesis process. Catalytic activity in CO/CO2 conversion process revealed approximately 100% conversion of CO at 220°C.

Wear of Al–Si alloys matrix reinforced with sol–gel coated particles

Abstract In the present study, squeeze cast A356 matrix composites reinforced with coated B4C particles were fabricated. Attempts were made to coat the B4C powders with TiB2 via a sol–gel process and incorporate them into the A356 alloy by a mechanical stirrer. The hardness of B4C particle is the third highest among all materials of this type. The wear properties of unreinforced A356 alloy and composites with different volume percentages of coated boron carbide particles were experimentally investigated. It is noted that composites exhibit better wear resistance compared to unreinforced alloy. The presence of B4C particles could shield the matrix and silicon phases from directly experiencing the applied load and reduce the weight loss during the wear test. According to the differences in wear rates of the composites, two separate wear rate regimes were identified as low and high wear rate regimes. Microscopic examination by a scanning electron microscope equipped with an energy dispersive spectrometer has also been carried out on the worn surfaces and debris.