مجله مواد نوین
سال دهم شماره 2 (پیاپی 38، زمستان 1398)

The aim of this research was the production of in-situ Al-Al3Ti composite on the surface of Al1050 alloy, using friction stir processing with reactive mechanically alloyed Al-Ti powder. Al-Al3Ti was fabricated with different rotational speeds and FSP passes. the primary Al-Ti powder was mechanically alloyed for different durations and suitable time for achieve a fine lamellar and uniform structure was determined. microstructral evaluations were implemented by optical microscopy (OM) and scanning electron microscopy (SEM). X-ray diffractometery (XRD) was used for phase identification and differential scanning calorimertry (DSC) was used to study the thermal behavior of powder during heating.Vickers micro hardness test and tensile test were used to evaluate mechanical properties of the base metal and FSPed samples. using mechanically alloyed Al-Ti particle led to the enhancement of hardness by 2.5 times, tensile strength by 3.4 times. meanwhile increasing the number of passes to 4, improved the reaction of Al3Ti formation in Al matrix. Improved the distribution of in-situ particles in the matrix caused better mechanical properties. Evaluation of the fracture surfaces indicated ductile fracture for all specimens.

Severe plastic deformation is one of the most effective methods of grain refinement which can be used for processing of ultra fine grained and nanostructured metallic materials. In the present study the combination of extrusion and equal channel angular pressing is imployed for severe plastic deformation of materials. Using this method, a severe plastic deformation was imposed succesfully on pure copper, Al7075 alloy, plain low carbon and microalloyed steels. The cabability of the proposed methode in production of nanostructured materials was approved by anallyzing the obtained microstructures of processed samples with opticaal microscopy and X-ray diffraction spectroscopy. The mean crystallite size of processed Al7075 alloy and plain low carbon steel was meassured to be 160 and 125 nm respectively. Also, the plastic deformation was applied on these materials at high temperatures. In the case of Al7075 alloy the microstructure was refined to the mean grain size of 6 µm through the occurance of dynamic recrystallization during deformation at the preheating temperature of 250 ̊C. Also, the plastic deformation of plain carbon steel at the preheating temperature of 930 ̊C demonstrated that the microstructure can be refined to 3 µm through dynamic strain induced transformation of austenite to ferrite. Moreover, the plastic deformation characteristics of combined extrusion-equal channel angular pressing was studied using finite element simultion. The formation of superficial cracks on the topside of Al7075 sample was also predicted using the FEM analysis.

In this investigation, the effect of plasma arc welding (PAW) process parameters on the welding quality of Ti-6Al-4V alloys is studied. These parameters including current, welding linear velocity and plasma gas composition that affected on the weld bead width. Macrograph results indicated that there is a certain range of electric current and linear velocity, which within the range, the full penetration welding obtains, and the weld bead is free from defect. As a result, the mechanical properties are favorable and comparable to those of the base material. It can be protected weld bead from oxidation with argon gas (5N). Furthermore, the automation of the process resulted in repeatability of the plasma arc welding is very good and the weld quality is well controlled. The results indicated that increasing the amount of helium gas, increases the welding area and the higher penetration depth of the weld. Examination of the microstructure of the weld region shows that there are three serrated alpha phase, alpha-beta phase (Widmanstätten) and the martensitic phase in the weld microstructure.

Nowadays, by technology progression (CAD), controlling tools movement in Incremental forming process, caused improvement of forming function mechanism-manufacturing symmetrical and asymmetrical pieces, as by determination of an ideal direction pattern and the way of contacting tools with pieces, Caused improvement of forming behavior in sheet metals and geometry firming of complicated forms, was used in airspace and auto-making industries. In present research two-point incremental forming of sheet metal was studied experimentally by investigating priority of tool movement in negative and positive limit of geometrical profile in central cavity die. Moving pattern of tools rotationally and spindle axis constant of system (Z) around die geometrical profile, was investigated for positive and negative forming. Used sheet metal in this research is 1050 Aluminum with 15mm thickness. The results of die geometrical profile showed that critical area with maximum thinning led to tearing of all samples of sheet metals in negative forming limit while moving pattern of rotator caused decrease of tearing rate and thinning relative to constant tools in sheet metal. Maximum rate of deep, formed in negative critical area of die geometrical profile, occurrence time of tearing in sheet metal Z= -25.2mm in rotational case of tools with first negative and second positive forming pattern, is the most ideal two-point forming case in central cavity pieces.

In this study, g-C3N4 was prepared and the effects of two-step heat treatment on its structure and photocatalytic properties were investigated. This material was then coated with gold nanoparticles by light deposition method and the composite was examined. The photocatalytic activity of the synthesized materials was also studied for hydrogen generation using sunlight and water. Characterization of the synthesized powders was carried out using various techniques such as X-ray diffraction, transmitted electron microscopy TEM, surface area analysis (BET) and ultraviolet-visible spectrometry (UV-Vis). X-ray diffraction showed that graphitic carbon nitride has a crystalline structure and its crystallinity is reduced after two stages of thermal treatment which is due to oxidation of graphitic carbon nitride. In addition, X-ray diffraction confirms the successful sedimentation of gold on graphitic carbon nitride. Transmission electron microscopy images show gold nanoparticles having particle size of about 8 nm. The study of UV-Visible absorption spectra of the synthesized powders showed that after two stages of heat treatment, the band gap of the samples increased and the presence of gold nanoparticles increased the light absorption in the visible light region via the surface plasmon resonance phenomenon. The specific surface area of the samples after two steps heat treatment and after applying of the gold nanoparticles increased from 4.2 to 15.7 and 29.3 m2/g, respectively. Graphitic carbon nitride with two steps heat treatment and coated with gold nanoparticles produced about 1128 μmol g-1 h-1 under sunlight. The photocatalytic mechanism of the system for the production of hydrogen gas was discussed.

Antimony dissolution in alkaline sulfide solution is the most common wet method of extraction of antimony from primary and secondary sources. In this research, the effect of adding crystallization step before electrowining step on improvement of antimony extraction from sulphide ores was studied. Effect of time and temperature of crystallization step on the removal of antimony and other constituents from leaching solution was explored. Furthermore, effect of crystallization step on some important process parameters such as antimony recovery, current efficiency, type of antimony precipitation on cathode plate and purity of produced antimony was investigated. According to the results, a decrease in the temperature and an increase in the time of crystallization step tend to enhance antimony separation to solid crystals. Removal degree of 95.2 wt% was the best result for antimony separation which was achieved after 2 hour crystallization at 5 C. Additionally more than 90% of As, Fe, Al and sulfur components such as sulphates and thiosulphates were remained in the liquid phase. Results of electrowining step show that high concentration of sulfur component in the solutions that did not pass crystallization step, leads harmful reactions to take place at the electrodes and consumption of electrical energy. Therefore, removal of these harmful components by crystallization causes an increase in the antimony production rate and current efficiency and also improves antimony adherence to the cathode plate. Moreover, the purity of final antimony product was rised from 98.5 to 99.6 wt%.

The purpose of the present work is to provide a suitable substrate for the deposition of titanium dioxide as a photocatalyst on aluminum. Due to the weak adhesion of photocatalysts to aluminum, there is no possibility of adhering photocatalysts to its surface or the lifetime is very short. For this reason, in this study, the adhesion between TiO2 and aluminum substrate is enhanced by the creation of micron pores on the substrate surface using two methods of anodizing and Plasma Electrolytic Oxidation (PEO) and the results of the two methods are compared. Experiments were carried out to investigate the dye removal over time using Rhodamine 6G aqueous solution in the presence of UV light. SEM images were also prepared from the surface of TiO2-coated aluminum substrates. The results of the study showed that the density of pores on the aluminum surface, and consequently, the dye removal in the PEO method were higher than those of conventional anodizing. In addition, although the dye removal in the PEO method is increased compared to the anodizing method, the overall process time and energy consumption in this method, especially in the pulse mode, were less than those of the anodizing method.

Entering environmental pollutants into water resources have harmful effects on human health and environment. In recent years, adsorption methods using adsorbents to remove contaminants from water resources have been abundant. Pentaaza tetra ethylene supported polyacrylamide (PAA-N5) as a novel adsorbent can be effective for removal of chemical pollutants of the aquatic solution. The purpose of this research is removal of Propargite by PAA-N5 as an adsorbent from polluted water in vitro.

The effects of variables such as pH, contact time, initial concentration, adsorbent amount, efficiency in removing Propargite from contaminated water were studied. Isotherms of Langmuir, Freundlich and Temkin have been fitted with the data of experiment. In addition, kinetics of pseudo- first order, pseudo- second order, intra-particle diffusion and Elovich were also fitted with the experiment data. Graphs and data analyses have been done using office program.

For PAA-N5, Langmuir isotherms show good agreement with the experimental data. Using these models to maximize absorption capacity of 294.11 (mg g-1) for PAA-N5. Absorption rates show quick responses and less than one hours. The results showed that the adsorption kinetics of pseudo- second order is more consistent (R2=0.99).

The results show that PAA-N5 absorbent is effective in removing Propargite contaminants from the aqueous solutions due to high surface area and rapid kinetics of the reactions. Therefore, the use of this adsorbent is recommended to remove Propargite from aqueous solutions.