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Showing 5 results for Raygan

M. Ghobeiti Hasab, F. Rashchi, Sh. Raygan,
Volume 11, Issue 2 (June 2014)

In this paper, gold leaching of a refractory sulfide concentrate by chloride–hypochlorite solution was investigated and effects of stirring speed, temperature and particle size on the leaching rate were reported. Experimental data for leaching rate of gold were analyzed with the shrinking–core model. Results were consistent with chemical reaction control mechanism in the first 1 h of leaching and diffusion control mechanism in the second 1 h. Apparent activation energy also was found to be 22.68 kJ/mol in the first step and 3.93 kJ/mol in the second step of leaching.
S. Niksirat, Sh. Raygan, S. Moradi Ghiassabadi,
Volume 12, Issue 2 (June 2015)

In this research, two different carbonaceous materials (Graphite:G and Petrocoke:P) were separately compared in terms of the carbothermic reduction of hematite and anatase in order to synthesize Fe-TiC nanocrystalline composite by mechanically activated sintering method. Powders were activated in a planetary high-energy ball mill under argon atmosphere for 0, 2, 5, 10,and 20 h. Then, the activated powders were analyzed by XRD and SEM to investigate phase constituents and microstructure of the mixtures. Results proved that Fe 2 O 3 and TiO 2 were not reduced by carbonaceous materials even after 20h of milling. SEM investigations showed that G-mixture was more homogenous than P-mixture after 20h of milling, meaning that graphite-anatase-hematite was mixed satisfactorily. Thermogravimetry analysis was done on 0 and 20h milled powders. TG and DTG curves showed that mechanical activation led to almost 300°C decrease in the reduction temperature of hematite and anatase in both mixtures. In the next step, the powders were sintered in a tube furnace under argon atmosphere. In the G-mixture, anatase was reduced to titanium carbide at 1100°C but, in the P-mixture, temperature of 1200°C was essential for completely reducing anatase to titanium carbide.Results of phase identification of the sintered powders showed that anano-crystalline ironbased composite with titanium carbide, as the reinforcement was successfully synthesized after 20 h high-energy milling of the initial powders and subsequent sintering occurred at 1200˚C for 1h
N. Ghanbarpourabdoli, Sh. Raygan, H. Abdizadeh,
Volume 13, Issue 4 (December 2016)

In this study, the adsorption of hexavalent chromium and zinc ions from the solution is investigated by raw red mud and mechanical-chemical activated red mud along with the possibility of selective reclamation of these ions from the solution. The mechanical-chemical activation of red mud was done by employing high-energy milling and subsequent acid treatment with HNO3. Raw red mud (RRM) and mechanical-chemical activated red mud (MCARM) adsorbents were characterized with Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM), and Brunauer–Emmett–Teller (BET) methods. In order to determine the suitable adsorption conditions, effects of pH of the solution, amount of adsorption, temperature, and time of adsorption were investigated. It was found that the optimum pH for the adsorption of hexavalent chromium and zinc ions by MCARM adsorbent was 2 and 6, respectively. According to these pH values, MCARM had the ability to separately adsorb more than 95 and 79% of hexavalent chromium and zinc ions from the solution, respectively. Experimental results were in good agreement with Langmuir and Freundlich isotherms. By considering the kinetic models of adsorption, the kinetics of the adsorption of both ions followed the pseudo-second-order reaction model. It was also determined that almost 25.8 and 61.8% of the hexavalent chromium and zinc ions adsorbed in MCARM could be recovered

H. Torkamani, H. Rashvand, Sh. Raygan, J. Rassizadehghani, Y. Palizdar, C. Garcia Mateo, D. San Martin,
Volume 14, Issue 3 (September 2017)

In industry, the cost of production is an important factor and it is preferred to use conventional and low cost procedures for producing the parts. Heat treatment cycles and alloying additions are the key factors affecting the microstructure and mechanical properties of the cast steels. In this study an attempt was made to evaluate the influence of minor Mo addition on the microstructure and mechanical properties of conventionally heat treated cast micro-alloyed steels. The results of Jominy and dilatometry tests and also microstructural examinations revealed that Mo could effectively increase the hardenability of the investigated steel and change the microstructure features of the air-cooled samples. Acicular microstructure was the consequence of increasing the hardenability in Mo-added steel. Besides, it was found that Mo could greatly affect the isothermal bainitic transformation and higher fraction of martensite after cooling (from isothermal temperature) was due to the Mo addition. The results of impact test indicated that the microstructure obtained in air-cooled Mo-added steel led to better impact toughness (28J) in comparison with the base steel (23J). Moreover, Mo-added steel possessed higher hardness (291HV), yield (524MPa) and tensile (1108MPa) strengths compared to the base one.

M. Monzavi, Sh. Raygan,
Volume 17, Issue 3 (September 2020)

Low-grade iron ores contain many impurities and are difficult to upgrade to make appropriate concentrates for the blast furnace (BF) or direct reduction (DR) technologies. In this study, the beneficiation of an Oolitic-iron ore (containing 45.46wt% Fe2O3) with magnetization roasting by non-coking coal (containing 62.1wt% fixed carbon) under a stream of argon gas was investigated. Then, a 2500 Gaussian magnet was used for dry magnetic separation method. The effects of roasting time, ore particle size and reaction temperature on the amount of separated part and grade of the product were examined. It was found out that the hematite inside of ore could almost be completely converted into magnetite by stoichiometric ratio of coal to ore at the roasting temperature of 625 °C for 25 min. Under the optimum condition, a high amount of magnetic part of the product (72.22 wt%) with a grade of 92.7% was separated. The most important point in this process was prevention of reduced ore from re-oxidation reaction by controlling roasting atmosphere, time and temperature. In addition, different analytical methods such as X-ray fluorescence (XRF), X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG) and scanning electron microscopy (SEM) were applied to investigate and expound the results.

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