Showing 9 results for Azad
Fotoohi B., No Parast M., Oliazadeh M.,
Volume 1, Issue 4 (Jul 2004)
Abstract
Gold deposits are varied regarding their geological and geochemical settings. Hence,their processing methods must be best organized for achieving the desired recovery of preciousmetals. In this research, two types of hard-rock gold ores, each with specific characteristics fromKouh-zar region (south of Damghan city) were subjected to mineral processing tests at thelaboratory scale. The reference (head) samples of both veins contained on average 3.5-4.5 ppmgold. According to mineralogical investigations no observable gold particles reported even inSEM analyses except for rare over-micrometer gold particles locked in the silica matrix.Therefore, the major (invisible) gold supposed to exist in sulfides" crystal structure. Flotationapplied to recover the gold interlocked within sulfides. The highest grades achieved were 49.2ppm @ R=77.61% for Baghu samples and 57.0 ppm @ R=61.00% for Darestan samples gold inthe sulfide concentrates. In the cyanidation diagnostic tests the optimum conditions of pH,particle size, cyanide concentration and leaching time were determined for both ores. High goldrecoveries (> 95%) were achievable for Baghu samples for the pH conditions between 10.5 and11, and cyanide and hydrated lime consumptions of 0.6 and 2.5 grams per kilogram of orerespectively. As it had been expected, direct cyanidation of Darestan samples (containing up to1.5% copper), couldn"t be established as an efficient procedure (due to cyanide consumption ofabout 20 times higher than for Baghu tests to achieve similar recoveries) and the preliminarycopper removal phase was determined as a necessity for better recovery of gold.
Dr Mohammad Reza Allazadeh,
Volume 9, Issue 3 (september 2012)
Abstract
Abstract: A combination of a finite element method (FEM) algorithm with ANSYS codes and post image processing of NDT ultrasonic images along with laboratory cooling experiments and microstructural analysis provide a guideline to determine the optimum cooling rate for any grade of steel in which the highest productivity can be achieved without any degradation of the cast steel products. The suggested FEM algorithm with ANSYS codes is introduced to develop a quasi real models to simulate quenching of as-cast steel with any cooling rate from any initial temperature below steel’s melting point. The algorithm builds a model which is capable to approximate the thermodynamic stresses generated by thermal strain and possible solid-solid phase transformation for as-cast steel with any chemical composition. The model is applicable for any casting geometry (slab, billet and bloom, bar, etc) and adaptable for any method of cooling (unidirectional or multidirectional). Cooling with any cooling agent can be simulated with the algorithm in an ideal case. The phase transformation of the steel in the algorithm can be controlled by Continuous Cooling Transformation (CCT) Diagram obtained from analytical calculation or real time-temperature-transformation experiments for the cast steel. A function for optimizing cooling rate is suggested.
Sh. Damghanian, H. Omidvar, S. H. Tabaian, A. R. Azadmehr,
Volume 11, Issue 2 (June 2014)
Abstract
The conical nanostructure improves the applications of alumina membranes and provides three dimensional
nanometer scale systems to study the chemical and physical properties. In this study, the nano cone structure is
produced in porous anodic alumina (PAA) by two-step anodizing. This conical nanostructure will improve the
application of PAA membranes. This approach is novel generation of the so-called "gradually decreased voltage"
technique, in which the voltage- time curve is divided into three stages and the effect of each step is investigated for
different electrolytes. The effect of the decreasing voltage is examined in two types of electrolytes oxalic and
phosphoric acid with a constant decrease in voltage rate. The results of SEM, FE-SEM images show the slope of the
inner cone layer in the oxalic acid to be considerably larger compared with phosphoric acid.
A. Mohammadzadeh, A. Sabahi Namini, M. Azadbeh,
Volume 11, Issue 3 (september 2014)
Abstract
The rapidly solidified prealloyed alpha brass powder with a size range of 40 to 100 μm produced by water
atomization process was consolidated using liquid phase sintering process. The relationships between sintering
temperature, physic-mechanical properties and microstructural characteristics were investigated. Maximum
densification was obtained at 930 °C, under 600 MPa compacting pressure, with 60 min holding time. The
microstructure of the sintered brass was influenced by dezincification and structural coarsening during supersolidus
liquid phase sintering. As a consequence of Kirkendall effect atomic motion between Cu and Zn atoms caused to
dezincification at the grain boundaries and formation of ZnO particles on the pore surfaces. It was concluded that
microstructural analysis is in a well agreement with obtained physical and mechanical properties. Also, the amount of
liquid phase, which depends on sintering temperature, results in different load bearing cross section areas, and it
affects the type of fracture morphologies.
M. Palizdar, Z. Aslam, R. Aghababazadeh, A. Mirhabibi, P. Sangpour, Z. Abadi, Y. Palizdar, R. Brydson,
Volume 16, Issue 4 (December 2019)
Abstract
In this paper the chemical interaction between catalyst and support has been studied to understand the observed different growth rate of CNTs in our previous paper. Both pure MgO and Mg(NO3)2 . 6H2O as sources of the MgO catalyst support and Fe2(SO4)3 · xH2O as the source of the Fe catalyst, were employed. A Fe catalyst supported on MgO has been synthesized using the wet impregnation method followed by calcination. To compare the catalyst grain size and its distribution, the sample were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and BET specific surface area (SSA) measurement and X-ray photoelectron spectroscopy (XPS). XPS technique have utilized complementary to demonstrate the existence of chemical interaction between MgO support and Fe catalyst. Results revealed that the type of precursor used to prepare the support has a significant influence on the morphology of the support and the associated distribution of the Fe catalysts. The highest yield of MgFe2O4 phase was obtained using a pure MgO precursor which after calcination results in a homogenous distribution of nano-sized Fe particles over the support surface
M. Azadi, M. Ferdosi, H. Shahin,
Volume 17, Issue 1 (March 2020)
Abstract
In this paper, the effects of solutioning and various aging heat treatment processes on the microstructure, the hardness and electrochemical properties of a duplex stainless steel (DSS) were studied. The evaluation of the microstructure and phase compositions were carried out by the optical microscopy (OM) and the X-ray diffraction (XRD), respectively. Electrochemical behaviors of specimens were evaluated by both potentiodynamic polarization and electrochemical impedance spectra (EIS) tests at temperatures of 25 and 60 ºC. The obtained results showed that the solutioning heat treatment increased corrosion rates with respect to the blank specimen. The aging process at 490 ºC for 20 hrs increased the volume percent of the carbide phase to the highest value (25.1%) which resulted in an increase of the hardness value to 170 VHN. The specimen which was aged at 540 ºC for 10 hrs with the Cr7C3 size of 22.8 µm, exhibited the higher corrosion resistance at both temperatures of 25 and 60 ºC with respect to other aged specimens. In addition, the temperature of 60 ºC promoted the anodic reactions in 3.5 wt% NaCl solution which decreased impedance modulus values significantly. Consequently, the carbide size was more effective parameter than the carbide content in predicting electrochemical behaviors of such alloys.
Farnaz Dehghani Firoozabadi, Ahmad Ramazani Saadatabadi, Azadeh Asefnejad,
Volume 19, Issue 2 (June-Biomaterials Special Issue- 2022)
Abstract
Fabrication of fully optimized tissue-engineered materials in order to simulating the natural structure, and enhancing the biological properties of damaged tissue is one of the major challenges in biomedical engineering and regeneration medicine. Although polymeric based membranes have revealed noticeable advancements in bone regeneration, their mechanical stiffens, electrical conductivity and bioactivity need to be tolerated.
Therefore, the present study is designed to generate a multifunctional biomaterial based on polylactic acid (PLA)/ polycaprolactone (PCL)/hydroxyapatite (HA) nanocomposite containing zinc oxide (ZnO) and Graphene (Gr) nanoparticles employing solvent casting combined with die cast techniques for using as absorbable joint implants in bone tissue regeneration. The physical, chemical, mechanical and biological properties of the produced nanocomposite biomaterials were analyzed in vitro. A detailed experimental evaluation between the nanocomposite coatings was carried out to shed light on the effect of ZnO and Gr nanoparticles on the properties.
It was found that the nanocomposite contained 1% ZnO and 1% graphene with a Young's modulus of 1540.5 ± 169.426MPa and the pure sample had a Young's modulus of 1194.81±215.342MPa. The rate of elongation at break of the nanostructure contained 1% graphene was 5.1±0.816%. This value was 3.8±0.944% for the pure sample. The improvement in elongation at break is due to the presence of polycaprolactone in the polymer matrix. The optimal sample with 1% zinc oxide and 1% graphene had antibacterial properties more than other samples. Also, the survival rate of fibroblasts cell in the vicinity of the optimal matrix was significantly different from other samples.
The obtained results revealed that the incorporation of the nanoparticles improved physico-chemical features and mechanical strength with enhanced biological properties and its anti-bacterial performance makes this material a promising candidate for further bone regeneration studies.
Imtiaz Ali Soomro, Srinivasa Rao Pedapati, Mokhtar Awang, Afzal Ahmed Soomro, Mohammad Azad Alam, Bilawal Ahmed Bhayo,
Volume 19, Issue 4 (Desember 2022)
Abstract
This paper investigated the optimization, modelling and effect of welding parameters on the tensile shear load bearing capacity of double pulse resistance spot welded DP590 steel. Optimization of welding parameters was performed using the Taguchi design of experiment method. A relationship between input welding paramaters i.e., second pulse welding current, second pulse welding current time and first pulse holding time and output response i.e, tensile shear peak load was established using regression and neural network. Results showed that maximum average tensile shear peak load of 26.47 was achieved at optimum welding parameters i.e., second pulse welding current of 7.5 kA, second pulse welding time of 560 ms and first pulse holding time of 400 ms. It was also found that the ANN model predicted the tensile shear load with higher accuracy than the regression model.
Bahram Azad, Ali Reza Eivani, Mohammad Taghi Salehi,
Volume 20, Issue 4 (December 2023)
Abstract
Microstructure evolution and mechanical properties of Zn-22Al alloy after post-ECAP natural/artificial aging were investigated. A homogenization treatment was applied to the casting samples. In addition, after preparing the samples for the ECAP, secondary homogenization treatment was done and then the samples quenched in the water to form a fine grain structure. After 8 passes of ECAP, some ECAPed samples were naturally aged and some ECAPed samples were artificially aged. Natural aging after 8 passes of ECAP showed that Zn-22Al alloy has a quasi-stable microstructure because limited grain growth occurred. Two-phase structure of Zn-22Al alloy prevented excessive grain growth after natural aging. On the other hand, artificial aging after 8 passes of ECAP caused a relatively much grain growth took place. In shorter times of artificial aging, the grain growth rate is faster due to the high surface energy of grain boundaries. On the contrary, as the time of artificial aging increased, the surface energy of grain boundaries decreased, which leads to a decrease in the grain growth rate. In addition, texture evolution was studied after aging artificial. Therefore, the main texture of α and η phases was determined.
