Showing 8 results for Vahdati Khaki
Fatemi Nayeri S.h.r., Aboutalebi M.r., Vahdati Khaki J.,
Volume 3, Issue 1 (Oct 2006)
Abstract
A mixture of Tio2+Al+C powders was mechanically activated using a planetary ball mill under different milling conditions wherein the milled powders were further subjected to combustion synthesis to produce TiC+Al2O3 composite. The mechanically alloyed powders were characterized by X-Ray diffraction analysis and TEM investigations. XRD analysis of milled powder mixture showed no significant reaction between TiO2, Al and C while a significant amorphization of powder mixtures was observed. TEM analysis indicated the formation of a composite structure of powder particles after milling. The subsequent thermal treatment of the milled powder mix showed that the milling of initial powder mixture under dry environment using mixed large and small balls had a great effect on reaction efficiency and yielded to the highest TiC + Al2O3 ratio in the synthesized products.
Jalil Vahdati Khaki, Salman Hadji Soleimani, Mohsen Moosavi Nejad,
Volume 4, Issue 1 (winter & spring 2007 2007)
Abstract
Abstract: The direct reduction of copper sulfide concentrate from Iranian Sarcheshme deposits
with carbon in the presence of lime was investigated in the temperature range of 800-1000 ºC. The
reduction kinetics was determined by means of weight loss measurements. It was found that the
rate of reaction increased considerably with increasing the temperature. The kinetics was also
improved when large excesses of lime and carbon were present in the mixture. The effects of
catalytic additives of Na2CO3 and K2CO3 were also investigated. It was realized that the rate of
reaction increased by higher concentrations of additives. X-ray diffraction analysis of reduced
samples revealed that sulfur was fixed as solid CaS, and metallic copper was formed.
S.h.r. Fatemi Nayeri, J. Vahdati Khaki, M. R. Aboutalebi,
Volume 6, Issue 1 (winter 2009 2009)
Abstract
Abstract:A combination of mechanical activation and Differential Thermal Analysis (DTA) together with X-Ray
Diffraction (XRD), and various microstractural characterization techniques were used to evaluate the starting reaction
in the combustion synthesis of TiC-Al2O3 composite in TiO2-Al-C system. The mechanical activation was performed
on the mixtures of two components of TiO2/Al, Al/C and TiO2/C and then the third component was added according
to the stoichiometric reaction for 3TiC+2Al2O3 composite formation. The powder mixtures were heated up to 1450 °C
under Argon atmosphere at a heating rate of 10 °C/min. The combustion synthesis temperature was observed to
decrease from 962 °C to 649 °C after milling of TiO2/Al mixture for 16 hr. On the contrary, the mechanical activation
of Al/C and TiO2/C mixtures for 16 hr made the reaction temperature increase to 995 °C and 1024 °C, respectively.
The decrease in reaction temperature as a result of milling the TiO2/Al mixture could be due to an increase of TiO2
and Al interface area as confirmed by TEM micrographs and XRD patterns of milled powder mixture. In addition, DTA
experiments showed that for the sample in which TiO2 and Al were mechanically activated the reaction occurred at
the temperature even lower than that of Al melting point.
A. H. Emami, M. Sh. Bafghi, J. Vahdati Khaki, A. Zakeri,
Volume 6, Issue 2 (Spring 2009 2009)
Abstract
Abstract:
the changes of BET surface area of a mineral substance during intensive grinding process. Validity of the proposed
model was tested by the experiments performed using a natural chalcopyrite mineral as well as the published data. It
was shown that the model can predict the experimental results with a very good accuracy and can be used to predict
what may happen under the similar experimental conditions.
Based on experimental observations, a model has been developed to describe the effect of grinding time on
M.sh. Bafghi, A.h. Emami, A. Zakeri, J. Vahdati Khaki,
Volume 7, Issue 2 (Spring 2010 2010)
Abstract
Abstract:
has been investigated. It has been shown that the mechanism of leaching reaction is diffusion through the product layer
and does not undergo any change as a result of mechanical activation in a wide range of experimental conditions.
Leaching rate is strongly influenced by milling intensity and the effect of ball to powder mass ratio is stronger than
milling time. Curve fitting of experimental data shows that leaching rate constant is approximately a linear function
of ball to powder mass ratio, while it obeys a power function with regard to the milling time.
The kinetics of chalcopyrite leaching in a ferric sulfate media for raw and mechanically activated samples
M. H. Hemmati, J. Vahdati Khaki, A. Zabett,
Volume 12, Issue 3 (September 2015)
Abstract
The volatile matter of non-coking coal was used for the reduction of hematite in argon atmosphere at nonisothermal condition. A thermal gravimeter furnace enable to use an 80 mm-height crucible was designed for the
experiments to measure the weight changes of about 10 grams samples. A two-layered array of coal and alumina and
four-layered array of iron oxide, alumina, coal and alumina was used for the devolatilization and reduction
experiments, respectively. The net effect of volatile reduction of Fe
2O3was determined and it was observe that 45%
reduction has been achieved. Three distinct regions were recognized on the reduction curve. The reduction of hematite
to magnetite could be completely distinguished from the two other regions on the reduction curve. At 600-950°C, the
reduction was accelerated. 63% of volatile matter resulted in 25% of total reduction before 600°C while the remaining
volatile matter contributed to 75% of the total reduction. From the reduction rate diagram, the stepwise reduction of
the iron oxides could be concluded. The partial overlap of the reduction steps were identified through the XRD studies.
The starting temperature of magnetite and wüstite reduction were determined at about 585°C and at 810°C,
respectively.
N. Alavifard, H. Shalchian, A. Rafsanjani-Abbasi, J. Vahdati Khaki, A. Babakhani,
Volume 13, Issue 3 (September 2016)
Abstract
In the present work, iron recovery from a low-grade hematite ore (containing less than 40% iron), which is not applicable in common methods of ironmaking, was studied. Non-coking coal was used as reducing agent. Reduction experiments were performed under various coal to hematite ratios and temperatures. Reduction degree was calculated using the gravimetric method. Reduced samples were subjected to magnetic separation followed by X-ray diffraction analysis. Total iron content, degree of metallization and recovery efficiency in magnetic part were determined by quantitative chemical analysis, which were obtained about 82%, 95% and 64% respectively under optimal conditions. CaO as an additive improved ore reducibility and separation efficiency. The microstructure of reduced samples and final products were analyzed by scanning electron microscopy. Final product with a high degree of metallization can be used in steel making furnaces and charging of blast furnaces which can improve production efficiency and decrease coke usage.
Zahra Rezayi, Mostafa Mirjalili, Jalil Vahdati Khaki,
Volume 21, Issue 4 (December 2024)
Abstract
Celestite ore, the primary mineral for producing strontium compounds, particularly strontium carbonate, is processed using the black ash method, which involves carbothermic reduction, water leaching, and carbonation. This study aims to investigate the combined effect of mechanical activation and additional graphite on the recovery rate and purity of strontium carbonate. Celestite ore with a strontium sulfate content of 79% was obtained from the Dasht-e-Kavir mine. Acid washing with 10% hydrochloric acid significantly reduced carbonate impurities, resulting in a celestite purity of 96.9%. Mixtures of celestite and graphite with varying amounts of graphite were prepared with and without milling. The mixtures were roasted at 900 °C for 1 hour to form strontium sulfide, followed by hot water leaching. After filtration, sodium carbonate was added to the leachate containing SrS, resulting in the formation and precipitation of white strontium carbonate crystals. The results showed that the addition of graphite increased the recovery rate in unmilled specimens. However, the recovery rate decreased significantly when 1 and 10 hours of milling were applied in the presence of excess graphite. Conversely, in the absence of additional graphite, milling for 1 and 10 hours increased the strontium recovery rate to over 95%. Furthermore, the analysis of strontium carbonate obtained from the sample with the highest recovery rate showed a purity of over 99.9%.
