Showing 700 results for Type of Study: Research Paper
R. Hasanzadeh, S. Fathi, T. Azdast, M. Rostami,
Volume 17, Issue 2 (6-2020)
Abstract
Heat transfer in foams consists of conduction through solid and gaseous phases, convection within the cells as well as radiation through the whole medium. Radiation thermal conduction affects the overall thermal conductivity by 40% in a high porosity. Therefore, the investigation of that term seems to be necessary. Radiation thermal conduction depends on the extinction coefficient which its determination is experimentally complex. In this study, this coefficient is theoretically estimated using Glicksman model for polyolefin foams and is verified in comparison with the experimental data. Extinction coefficient which plays an effective role in the radiation thermal conduction depends on the morphological properties including foam and solid densities, cell and strut diameters. The results demonstrate that the radiation thermal conduction decreases by reducing cell size and increasing foam density and strut diameter. An L25 orthogonal array of Taguchi approach is used for optimization of radiation thermal conduction respect to foam density, cell and strut diameters as variable parameters. The analysis of variance results illuminate that foam density and cell diameter with 58 and 32% contribution are the most effective parameters on the radiation thermal conduction, respectively. At optimum conditions according to the prediction tool of Taguchi approach, the radiation thermal conduction significantly decreases to 1.0908 mW/mK.
M. Ghamari, M. Ghasemifard,
Volume 17, Issue 2 (6-2020)
Abstract
In this research, the dependence of the optical band gap of nano gamma alumina on the OH/Al ratio and concentration of aluminum sulfate is measured through diffuse reflectance spectroscopy (DRS) in the range of 900-1100nm. The samples were prepared via sol-gel method. The results showed that the band gap is pH and concentration-dependent but in a different way. The direct band gap of alumina was determined to be 3.40, 4.37, 3.90, and 3.65 eV for samples prepared at pH 6, 7, 8, and 9, respectively. A decreasing trend was observed with increasing pH (except for pH6). The lowering of the band gap may be associated with the variations in particles size during synthesis due to the quantum size effect. The values of the band gap increased significantly through increasing concentration from 3.90 to 5.65 eV for 0.1M to 0.3M. The role of concentration in band gap control is remarkably more than pH.
S. Agbolaghi,
Volume 17, Issue 2 (6-2020)
Abstract
Confined and unconfined crystallizations of poly(3-hexylthiophene) (P3HT) were studied in the solution-grown supramolecules and melt-grown systems using a differential scanning calorimeter. The carbon nanotube (CNT) and reduced graphene oxide (rGO) and their functionalized (CNT-f-COOTh and rGO-f-TAA) and grafted (CNT-g-PDDT and rGO-g-PDDT) derivatives were employed to develop the samples. The absorbance, structure details via Scherrer formula, fusion enthalpy (ΔHm) and crystallinity (Xc) were measured in two distinct confined/unconfined crystallization environments. Although the functionalized-CNT/rGO precursors partially reduced the crystallite qualities with respect to the pristine CNT and rGO ones in the solution-grown supramolecules, they did not affect the structural properties in the melt-grown samples. Grafted carbonic materials could be considered as appropriate seeds for the arrangement of P3HTs in both solution and melt crystallizations. The best absorbances, larger and more compact crystals, and higher melting point, ΔHm, and Xc values were recorded for the pre-developed CNT-g-PDDT/P3HT stem-leaf (6.09–22.51 nm, 3.52–13.89 Å, 239.8 °C, 30.86 J/g and 83.40%) and rGO-g-PDDT/P3HT coarse-patched (5.96–20.76 nm, 3.57–13.95 Å, 237.6 °C, 29.13 J/g and 78.73%) supramolecules. Although the melt-grown CNT-g-PDDT/P3HT (201.4 °C, 215.3 °C, 16.22 J/g and 43.84%) and rGO-g-PDDT/P3HT (205.4 °C, 218.8 °C, 18.06 J/g and 48.81%) nanostructures were not as perfect as the respective solution-grown nano-hybrids, they were well-arranged with respect to the CNT/P3HT, CNT-f-COOTh/P3HT, rGO/P3HT and rGO-f-TAA/P3HT samples
R. Katal, A. Azizi, M. Gharabaghi,
Volume 17, Issue 2 (6-2020)
Abstract
Present paper investigates the dissolution behavior of copper from chalcopyrite concentrate sample using cupric chloride solution in detail. Response surface modeling (RSM) in combination with d-optimal design (DOD) was utilized for modeling and optimizing the cupric chloride leaching process. At first, a quadratic polynomial model was developed for the relationship between the recovery of copper and influential factors. The predictions indicated an excellent agreement with the experimental data (with R2 of 0.9399). Then, the effects of main factors including pH (1-4), liquid/solid ratio (2-7 mL/g), temperature (70-90 °C), CuCl2 concentration (6-35 g/L), and leaching time (0.5-16) were determined. The findings demonstrated that the temperature and CuCl2 concentration were the most effective factors on the dissolution rate of copper from chalcopyrite sample, while liquid/solid ratio had the lowest impact. The recovery of copper increased linearly with an increment in the liquid/solid ratio and the decrease in the pulp pH. Additionally, the recovery enhanced by increasing the temperature and CuCl2 concentration owing the generation of Cu–Cl complexes species and reached a plateau point and then almost remained unchanged. Meanwhile, it was found out that the recovery of copper was independent of the interaction between factors. Moreover, the optimization of leaching process was carried out by Design Expert (version 7) software and desirability function method and the highest recovery of copper was found to be about 86.1% at a pH of ~1.4, temperature of 89 °C, liquid/solid ratio of 6.8 mL/g, CuCl2 concentration of 21.79 g/L and leaching time of ~8 h.
H. Azimi,
Volume 17, Issue 2 (6-2020)
Abstract
In this work, the poly styrene-co-acrylonitrile (SAN)beads and three blowing agents (CO2, N2 and n-pentane) were used to investigate the foaming process via our batch foaming system. The solubility and diffusivity of three blowing agents were determined by the MSB. The solubility of blowing agents was increased by pressure and decreased by temperature increment. It was resulted that the solubility and diffusivity data for SAN/n-pentane/CO2 system (Using co-blowing gent) were higher than other samples. According to the scanning electron microscopy (SEM) results, it was concluded that the cell and foam densities were decreased with temperature increment and increased by pressure release rate in all foamed beads. With using co blowing agents, higher pressure release rate and low temperature without adding any fillers, we could improve the foam characteristics and produced the SAN foams with smaller cell sizes and greater cell and foam densities.
S.m. Moussavi Janbesarayi, M. Mohebi, S. Baghshahi, S.a. Ahmad Alem, E. Irom,
Volume 17, Issue 2 (6-2020)
Abstract
Overusing nitrogen fertilizer causes some serious problems for water resources, soil, and agriculture products. Researchers have been trying to develop effective means which may use less amount of fertilizers containing nitrogen. In this work, cost-effective ceramic granule adsorbent was prepared to be used as a fertilizer carrier of controlled release behavior. A mixture of 70 wt.% domestic kaolin and 30 wt.% gibbsite was used to produce the granules. By utilizing thermal analysis of raw granule, the calcination temperatures were obtained and the effect of various calcination temperatures of 500, 600, and 700˚C on the water adsorption was studied. The characteristics of granules were investigated by XRD, BET, FTIR, and SEM analyses. The results showed that by increasing the calcination temperature, the crystal structure of the granules was transformed into a dehydrated form and by calcination at 600°C the specific surface area of granules increased from 7.50 to 53.45m2/g. The granules were soaked in a 500g/lit solution of urea, where they adsorbed about 10wt.% urea. The dried urea-loaded granules were placed in water where the release of urea was measured by UV-vis spectrophotometry. Finally, different portions of urea-loaded granules were evaluated as fertilizer in the growing bed of corn plant where the height and the stem diameter of samples were compared with a control sample as well as a sample fertilized by urea directly. The results showed that by using the loaded granules, the urea consumption can be reduced by 50%.
O. Kaliuzhnyi, V. Platkov,
Volume 17, Issue 2 (6-2020)
Abstract
A method has been advanced to form porous poly(tetrafluoroethylene) (PTFE) using a partially gasified porogen. Sodium hydrogen carbonate (NaHCO3) was selected as a porogen. The standard technology of porous materials production including mixing, pressing, thermal treatment, porogen leaching and drying was employed.The formation of porous PTFE structures was investigated in a wide range of NaHCO3 concentrations. The mechanism for formation of such structures has been proposed. It is shown that the NaHCO3 porogen affords permeable porous structures with porosities down to 50% (cf. the lowest bound porosity of 70% attainable with the standard NaCl porogen).The flow rate characteristics of the pressure difference as a function of the air flow rate have been measured on porous PTFE samples formed using the partially gasified NaHCO3 porogen and the NaCl porogen. The obtained flow rate characteristics were linear, which suggests a laminar air flow in the pores. The permeability of the porous PTFE structures formed using the above porogens has been estimated.The use of the NaHCO3 porogen has allowed a five-fold cut of the leaching time, a more than three times enhancement of the permeability of the porous structures and an increase in the hydraulic pore diameter by a factor of 1.8 as compared to the corresponding data obtained with the NaCl porogen.
Sa. Benkacem, K. Boudeghdegh, F. Zehani, Y. Belhocine,
Volume 17, Issue 2 (6-2020)
Abstract
This paper focuses on the effect of ZrSiO4/ZnO ratio on the properties of the glaze to be used on ceramic sanitary-ware. Structural and morphological characterization of these glazed ceramics were identified by XRD, SEM, FTIR and Raman Spectroscopy. Furthermore, thermal properties were determined by DTA and TG techniques. Besides, flexural strength, Vickers Microhardness, whiteness and chemical resistance were investigated experimentally. XRD analysis showed that the zircon and quartz were the crystalline phases, zircon was also precipitated into the glaze layer during firing. It was found that an increase of the ZrSiO4/ZnO ratio part weights from 3.85 to 67, causes an increase in the zircon crystallite particle size from 203.90 to 288.86 Å. From DTA, it was observed that by increasing ZrSiO4/ZnO ratio, the crystallization temperature of zircon decreases. The glaze exhibits the highest whiteness value when the ratio of ZrSiO4/ZnO becomes 12.60.
A. Beigei Kheradmand, S. Mirdamadi, S. Nategh,
Volume 17, Issue 3 (9-2020)
Abstract
In the present study, the effect of adding minor amounts of scandium and zirconium elements to the 7075 alloyon the re-crystallization behaviour of one aluminium alloy (7000 series) was investigated. For this purpose, two kinds of Al-Zn-Mg-Cu-Sc-Zr alloys with the same amount of Zr and different amount of Sc were prepared. Homogenization durations and temperatures of alloys after alloying were obtained by DSC analysis and optical microstructure observations. The results showed that the optimum homogenization temperatures for Al-Zn-Mg-Cu-0.05Sc-0.1Zr and Al-Zn-Mg-Cu-0.1Sc-0.1Zr alloys were 500
0C and 490
0C respectively, and the optimum duration for both alloys was 12hours. After homogenization of alloys, the re-crystallization behaviour of the alloys was investigated by Brinell hardness test. Obtained results showed that although the starting re-crystallization temperature for both alloys was similar in 2 hours, but it was 130°C for alloys with 30% forming, and 120°C for alloys with 50%forming and recrystallization temperature for Al-Zn-Mg-Cu-0.1Sc-0.1Zr alloy was 350
in 2 hours. Despite what was expected, the hardness of Al-Zn-Mg-Cu-0.05Sc-0.1
S. Mortezaei, H. Arabi, H. Seyedein, A. Momeny, M. Soltanalinezhad,
Volume 17, Issue 3 (9-2020)
Abstract
Dynamic Recrystallization (DRX) is one of the likely mechanisms for fine-graining in metals and alloys. The dynamic recrystallization (DRX) phenomena occurs in different thermo-mechanical processing (TMP) conditions for various metallic materials. DRX depends on various materials and thermo-mechanical parameters such as temperature, strain rate, strain, stress and initial microstructure. in the present study, the restoration mechanism of the 17-7PH stainless steel has been investigated using a hot compression test under different conditions of thermo-mechanical treatment. The microstructural characteristics and the behavior of the hot deformation of the under study steel are investigated using flow curves and microstructure images obtained from optical microscopy. The results show that the maximum and steady state stresses are significantly affected by the strain rate and the deformation temperature. So that, the flow stress increases with decrease in the deformation temperature and increase in the strain rate. Microstructural studies confirm the occurrence of DRX as a restoration mechanism in the microstructure for the two phases of austenite and ferrite.
M. Monzavi, Sh. Raygan,
Volume 17, Issue 3 (9-2020)
Abstract
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.
N. Mohammed, H. F. Dagher,
Volume 17, Issue 3 (9-2020)
Abstract
Thin films of meta-cinnabar mercuric sulfide (β-HgS) nanoparticles (NPs) was prepared by pulsed laser ablation (PLA) utilizing a pellet of cinnabar mercuric sulfide (α-HgS) was immersed in distilled water (DW). Q-switched Nd:YAG laser of 1064 nm wavelengths with repetition rate (1hz) and fluency (1.5 J/cm2) applied for ablation. Structural, morphological and particle sizes of the β-HgS NPs are invastigated by analyzing XRD, AFM, SEM and TEM measurements. Their crystal structure is transformed from hexagonal (wurtzite) of the α-HgS target material to cubic (zinc blende) β-HgS NPs. The optical properties of the β-HgS NPs are measured by UV–visible spectrophotometer. The direct band gap is calculated to be (2.45eV) of small particles (4-6.2nm) moreover, the band gap value of smallest particles (1-4nm) is (3.47eV) according to the optical transmission spectra
R. Niazi, E. Tohidlou, H. Khosravi,
Volume 17, Issue 3 (9-2020)
Abstract
The effects of erbium (Er) addition at various weight percentages (0-0.6 wt.% at an interval of 0.2) on the microstructural characteristics, tensile response and
wear properties of as-cast Al-7.5Si-0.5Mg alloy were evaluated. The microstructure of samples was examined by X-ray diffraction, optical microscopy and scanning electron microscopy. The obtained results demonstrated that the incorporation of erbium obviously decreased the α-Al grain size and eutectic Si, and altered the Si morphology from plate to semi-globular. Further addition of erbium (> 0.2 wt.%) did not alter the eutectic morphology and size. Moreover, the Al
3Er phase was also observed in the eutectic region after modification. Out of the erbium contents used, 0.2 wt.% erbium showed the best influence on the tensile and wear properties. Compared with those of unmodified specimen, the values of ultimate tensile strength and elongation were enhanced by 31% and 39%, respectively with the introduction of 0.2 wt.% erbium. Additionally, a remarkable enhancement in the wear properties was observed with the addition of 0.2 wt.% erbium.
B. Mirzakhani, Y. Payandeh, H. Talebi, M. Maleki,
Volume 17, Issue 3 (9-2020)
Abstract
In this paper, the effect of two-step precipitation hardening on the mechanical properties of Al-3.7Cu-1Mg was investigated. For this meaning, some specimens were subjected to the first step aging at 175, 190 and 205°C for 2 h, once the samples solution treated at 500°C. To have stable precipitates uniformly distributed in the microstructure and to reduce the heat treatment time, the second step was implied at 65°C. The tensile and hardness tests were performed at ambient temperature immediately after aging. The results indicated that depending on the first step temperature, the second aging time affects the alloy mechanical behavior in different aspects. A factor named SNMP introduced to determine the cycle giving the best mechanical properties. The strength and elongation increase 1.5 and 2 times respectively; compared to the values reported in the DIN EN 755-2 standard by performing the two-step aging cycle, consisting of the first-stage at 175°C and the second step at 65°C for 10 hours. Moreover, using the proposed two-step aging, the heat treatment time was reduced considerably compared to the conventional precipitation hardening process.
A. Thakur, G. Reddy,
Volume 17, Issue 3 (9-2020)
Abstract
Mercury, one of the common pollutants in water, is known to affect human health adversely upon exposure. It is released in water not only by various natural processes but also by human activities. Methods developed so far for the detection of mercuric ions in water have limitations like sensitivity range, complex setup, skillful operation etc. Silver nanoparticles, due to unique properties, have been explored by researchers to develop better detection systems. Stable silver nanoparticles can be easily synthesized by methods of green chemistry, its reaction with mercuric ion can be easily observed by changes in color and UV-Vis spectra. The absorbance data from UV-Vis spectra can also be used in quantifying mercury concentration. In this paper, stable silver nanoparticles synthesized using silver nitrate as precursor, sodium lignosulphonate (LS) as reducing and stabilizing agent under microwave radiation are explored for detection of mercuric ions in water. Formation of AgNP was confirmed by UV-Vis band at 403.5nm. The intensity of this band showed a proportional decrease with increasing Hg+2 concentration. Hg+2 ions were detected by a distinct color change at higher concentration of Hg+2 also. The limit of detection (LOD) calculated from the observed absorbance data to be 0.7 ppm.
M. Hamdi, H. Saghafian Larijani, S. G. Shabestari, N. Rahbari,
Volume 17, Issue 3 (9-2020)
Abstract
Aluminum matrix composites are candidate materials for aerospace and automotive industries owing to their specific properties such as high elastic modulus (E), improved strength and low wear rate. The effect of thixoforming process on the wear behavior of an Al-Mg2Si composite was studied in this paper. During applying thixoforming process, casting defects such as macrosegration, shrinkage and porosity are being effectively reduced. These advantages are sufficient to attract more exploration works of thixoforming operation. Thermal analysis of the composite, as-cast microstructure, wear surface and subsurface area of the thixoformed alloy were investigated. Wear behavior of the specimens were examined using a pin-on-disk machine based on ASTM-G99, at the applied loads of 25, 50 and 75 N and the constant sliding velocity of 0.25m/s. The worn surfaces and subsurfaces were examined by scanning electron microscopy (SEM). The experimental results indicated that the thixoformed specimens exhibited superior wear resistance than the as-cast alloy. Moreover, the dominant wear mechanism is an adhesive wear followed by the formation of a mechanical mixed layer (MML). However, a severer wear regime occurs in the as cast specimens compared with the thixoformed ones
M. T. Basha G, V. Bolleddu,
Volume 17, Issue 3 (9-2020)
Abstract
The microstructural characteristics, mechanical properties, and wear characterization of air plasma sprayed coatings obtained from Carbon nanotubes (CNTs) reinforced Al2O3-3wt%TiO2 powders were examined at different loading conditions and different percentage proportion of CNTs. The CNTs in the proportion of 2, 4, and 6wt% were used as nanofillers to modify the properties of coatings. The uniform dispersion of CNTs throughout the powder particles can be observed from the SEM micrographs. The porosity of the microstructure of the coatings was measured by image analysis. Also, the mechanical properties such as microhardness and surface roughness were measured by microhardness tester and profilometer, respectively. The wear tribometer was used to analyze the tribology of the coatings by varying different parameters. The different loading conditions used were low load (0.5 kgf), moderate load (1.0 kgf), and elevated load (1.5kgf), respectively. The microhardness showed a slight increase with an increase in the percentage of CNTs proportion. Similarly, the surface roughness value showed a decreasing trend, since the CNTs were filled in the pores. From wear tests, it was observed that the coefficient of friction and wear rate were very less at 6wt% CNTs and 1.5kgf load. This was mainly due to the bridging of CNTs in between the splats. This implies that CNTs were one of the most suitable additives for improving the microstructural and tribological characterization of the ceramic coatings.
P. Shahsavari, B. Eftekhari Yekta, V. Marghussian,
Volume 17, Issue 3 (9-2020)
Abstract
Strong glass-ceramic foams with a compressive strength of 20 MPa were prepared by adding various amounts of Fe2O3 to a soda lime-based glass composition, and SiC as a foaming agent. The foams were prepared by firing the compacted samples in the range of 750–950°C for different soaking times. The crystallization behavior of the samples was investigated by Simultaneous Thermal Analysis (STA), Scanning Electron Microscope, and X-Ray Diffractometer (XRD). Based on the results, solid solutions of pyroxene groups were crystallized by the surface mechanism, between 730˚C and 900˚C during the firing of the specimens, and their amounts increases with increasing of the added iron oxide. Besides, we found that Fe2O3 neither acts as a nucleant for pyroxene nor as an oxidizer for SiC. The results also showed that the compressive strength as well as the crystallization behavior of the foams was influenced by the presence of the SiC particles.
A. Kazazi, S. M. Montazeri, S. M. A. Boutorabi,
Volume 17, Issue 4 (12-2020)
Abstract
In the present study, austempering heat treatment was performed on compacted graphite aluminum cast iron with the chemical composition of 4.8%wt Al, 3.2%wt C, 0.81%wt Ni, 0.37%wt Mn, and 0.02%wt Mg. This study aims to investigate the effect of aluminum additions and removal of silicon on the kinetics of austempering transformation of Fe-3.2%C alloy. The cast samples were austenitized at 900 °C for 120 min and the isothermal austempering heat treatment was performed at 200 °C, 300 °C and 400 °C for 5, 30, 60, 120 and 180 minutes, respectively. Kinetics of this transformation was studied by X-Ray diffraction (XRD) analysis. The effect of temperature and time on the microstructure and hardness of the austempered samples was investigated and discussed. The presence of Al was seen to prolonged formation of the carbides from high carbon austenite, and that expanded the process window in the austempering transformation. Besides, the lower bainitic ferrite phase was observed in the austempered samples at 200 °C and 300 °C. Increasing austempering temperature to 400 °C changed the lower bainite to upper bainite structure. The volume fraction of austenite reached its maximum level (34.6 %) after austempering the samples at 400 °C for 30 minutes.
S. Karimzadeh, F. Mahboubi, G. Daviran,
Volume 17, Issue 4 (12-2020)
Abstract
In the present investigation effects of time and temperature on plasma nitriding behavior of DIN 1.2344 (AISI H13) steel are studied. Pulsed plasma nitriding process with a gas mixture of N2 = 25% + H2 = 75% and duty cycle of 70% is applied to cylindrical samples of DIN 1.2344 hot work tool steel. X-ray diffraction, surface roughness, microhardness and ball on disc wear test are performed and behavior of plasma nitrided samples are compared. Scanning electron microscopy and optical microscopy are used in order to observe the microstructure of samples after nitriding. XRD results showed that the compound layer is dual phase. Hardness near the surface dropped by rising the process temperature and it rose in longer process durations. The comparison of µ results showed frictional properties in longer durations with lower temperatures is approximately the same in higher temperatures with shorter durations.
