Iranian Journal of Materials Science and Engineering

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  Abstract

  The effect of mechanical activation using an attrition mill on the particle size of an ilmenite concentrate and its effect on the ability of the concentrate for Iron separation during hydrochloric acid leaching and the kinetics of the dissolution process have been investigated. It was observed that mechanical activation in an attritor significantly enhances the dissolution of iron in hydrochloric acid while have a slight effect on dissolution of titanium. With the mechanically activated ilmenite using an attrition mill, leaching conversion at 90 ^oC reached to 80%. The kinetic data of leaching of mechanically activated ilmenite was found to follow shrinking core model. Mechanically activating ilmenite using the attrition mill was found to cause the activation energy of leaching to be decrease from 43.69 , found for samples leached without mechanically activated, to 18.23 .

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Abstract:

point of view. In this study, a shaking-table was used for concentrating a manganese ore sample from the Ghasem Abad

area in Kerman, Iran. Experiments were designed by using L

The influence of each variable and their interactions on the operation of the device was studied. The variables under

investigation were: table slope, table frequency, water flowrate, feed rate, and particle size. The manganese

concentrate grade, recovery, and separation efficiency were used as response variables. It was shown that water

flowrate, table slope, feed rate, and particle size are the significant variable on concentrate grade while, all the

variables influence manganese recovery. Also, water flowrate, table slope, and table frequency have an important

effect on manganese separation efficiency. Finally, three mathematical models were presented to predict the values of

each response variables.

Among all gravity concentration methods, the shaking-table is the most effective one from the metallurgical8 Taguchi design with five variables, each in two levels.

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The epoxy coatings containing multi-walled carbon nanotube/ poly ortho aminophenol nanocomposite were prepared and used as anticorrosive coatings. The nanocomposites with different contents of carbon nanotube were synthesized in a solution of sodium dodecyl sulfate and ammonium peroxy disulfate as a surfactant and an oxidant, respectively. The morphology and structural properties were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy methods. The mean size of nanocomposite particles was 20-35 nm determined by scanning electron microscopy. The epoxy coatings containing the nanocomposites were applied over mild steel panels and their corrosion performance was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization measurements in a 3.5 % sodium chloride solution. The results showed that epoxy coatings consisting of nanocomposite with 1 wt.% multi-walled carbon nanotube exhibited higher anticorrosive properties than other prepared coatings of different carbon nanotube contents, which could be due to the strong interaction between the mild steel surface and the conjugated nanocomposite.

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In this paper, cyclic flaring and sinking (CFS) as a new severe plastic deformation (SPD) method was employed to produce the ultrafine grain (UFG) copper tubes. The extra friction has eliminated in the CFS method that provided the possibility for production of longer UFG tubes compared to the other SPD methods. This process was done periodically to apply more strain and consequently finer grain size and better mechanical properties. The CFS was performed successfully on pure copper tubes up to eleven cycles. Mechanical properties of the initial and processed tubes were extracted from tensile tests in the different cycles. The remarkable increase in strength and decrease in ductility take placed in the CFS-ed tubes. The material flow behavior during CFS processing was analyzed by optical microscopy (OM), and a model was presented for grain refinement mechanism of pure copper based on multiplication and migration of dislocations (MMD). This mechanism caused that the initial grains converts to elongated dislocation cells (subgrains) and then to equiaxed ultrafine grains in the higher cycles. The CFS method refined the microstructure to fine grains with the mean grain size of 1200nm from initial coarse grain size of 40µm

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Petroleum coke contains high amounts of carbon and is used in the manufacturing of anode electrodes for the aluminum extraction. In the process of aluminum production, some particles separate from anodes as waste which contain petroleum coke. Therefore, recycling and processing of these petroleum coke particles is the subject of this study. The ash content reduced to 31% and 13% in the jig and shaking table concentrate, respectively. These two steps were considered as the pre-processing methods and heavy media separation was used to decrease the ash content much more. Finally, flotation was performed in order to purify the particles with the size of less than one millimeter.

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Kinetic models are the most important instruments for predicting and evaluating the performance of flotation circuits. To determine the kinetic order and rate of flotation of a gilsonite sample, flotation experiments were carried out in both rougher and cleaner stages. Experiments conducted using the combinations of petroleum-MIBC, gas oil-pine oil, and one test without any collector and frother. Five first order kinetic models were applied to the data obtained from the flotation tests by using the Matrix Laboratory software. Statistical analysis showed that the classic first order model perfectly matched the rougher and cleaner results performed using petroleum-MIBC combination. The kinetic constants (k) were calculated as 0.04 (s^-1) and 0.01 (s^-1) for the rougher and cleaner, respectively. Rougher and cleaner tests without collector and frother also matched with the modified gas/solid adsorption and rectangular models with the k values of 0.05 (s^-1), and 0.01 (s^-1), respectively. The relationship between flotation rate constant, maximum combustible recovery and particle size were also studied. The results showed that the maximum flotation combustible recovery and flotation rate were obtained with an intermediate particle size both in the rougher and cleaner flotation processes. The combustible recovery and flotation rate in the rougher flotation process were higher than that in the cleaner flotation process.

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Quaternary ammonium compounds (QACs) are among the most commonly used antibacterial agents. The aim of this study was to synthesize a dimethacrylate monomer functionalized with a QAC and to study its effect on the properties of an orthodontic adhesive primer. Urethane dimethacrylate monomer functionalized with a QAC (UDMAQAC) was synthesized and then characterized by nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR). 5, 10, 15 and 20 wt% of UDMAQAC was added to an orthodontic adhesive primer (control group). FTIR analysis was used to measure the degree of conversion (DC). The bond strength of dental brackets was measured by shear bond strength (SBS) test and adhesive remaining index (ARI) was evaluated by stereomicroscope. Agar diffusion test and MTT assay were used to evaluate the antibacterial property and cell viability, respectively. Statistical analysis included one-way ANOVA with Tukey’s post hoc test and Kruskal-Wallis nonparametric test (P˂0.05). Although the obtained data did not show significant differences between the SBS and DC of different groups, but the highest values were obtained by adding 10 wt% monomer. Adding more than 10 wt% UDMAQAC resulted in significant increase in antibacterial property. The 15 and 20 wt% groups showed significantly lower cell viability