M. Ghasemian Safaei, Dr. S. Rastegari, R. Latifi,
Volume 17, Issue 2 (6-2020)
Abstract
In this study, Si-modified aluminide coating on nickel-base superalloy IN-738LC was prepared using a pack cementation method with various powder compositions at 1050 °C for 6 h. The cyclic oxidation test was conducted at 1000 °C followed by cooling at room temperature for 200 h and 20 cycles. The effect of powder composition and the way of cooling on the coatings microstructure and oxidation behavior were studied. Investigations carried out using a scanning electron microscope (SEM), EDS analysis, and XRD. Microstructural observations revealed that the coating thickness of 293 and 274 µm was achieved in the case of using pure Al and Si powder and alloyed Al-20wt.%Si one in the packed mixture, respectively. It was also found that utilizing pure Al and Si powder with NH4Cl as an activator in the pack led to the formation of silicide coating, owing to the higher diffusion of Si, which showed superior cyclic oxidation performance.
R. Kumar, Y. Chandra Sharma, V. Vidya Sagar, D. Bhardwaj,
Volume 17, Issue 2 (6-2020)
Abstract
In this study an effort has been made for the plasma ion nitriding (PIN) of Inconel 600 and 601 alloys at low temperatures. After plasma ion nitriding, microstructure study, growth kinetics of nitrided layer formation and wear properties were investigated by various characterization techniques such as; scanning electron microscope (SEM), X-ray diffraction (XRD) analysis, micro-hardness measurement and wear test by pin on disk technique. It was found that, surface micro-hardness increases after PIN process. A mix peak of epsilon (ε) phase with fcc (γ) phase was detected for all temperature range (350 0C to 450 0C), while the chromium nitride (CrN) phase was detected at elevated temperature range ~450 0C in inconel 601 alloy. The calculated values of diffusion coefficient and activation energy for diffusion of nitrogen are in accordance with the literature. Volume loss and wear rate of the plasma nitrided samples decreases, but it increases as PIN process temperature increases.
S. Manafi, S. Joughehdoust,
Volume 17, Issue 2 (6-2020)
Abstract
In this research, calcium titanate (CaTiO3) hollow crystals have been successfully prepared via hydrothermal method. Titanium tetrachloride, calcium chloride dihydrate and potassium hydroxide were used as Ti, Ca and precipitating agent, respectively. The hydrothermal synthesis was performed at different temperatures and time durations. The negative amount of the Gibbs free energy shows the reactivity of the reaction at room temperature. Characterization of CaTiO3 was carried out using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The optimum condition for preparing CaTiO3 is the sample kept in an autoclave at 300 ℃ for 3 h that requires less energy and time which consists of a high degree of crystallinity. In this research, tetragonal CaTiO3 hollow crystals have been successfully prepared via hydrothermal method. TiCl4, CaCl2.2H2O, and KOH were used as Ti, Ca and precipitating agent, respectively. The hydrothermal synthesis was performed at different temperatures and time durations. Characterization of CaTiO3 was carried out using SEM, HRTEM, and XRD. The sample kept in the autoclave at 300 ℃ for 3 h well crystallized and required less energy and time for synthesis. The powder has a homogenous dispersity of crystals with the range of nanometer to micrometer sizes which makes it a good candidate as a photocatalyst material
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.
A. Nemati,
Volume 17, Issue 2 (6-2020)
Abstract
Synthesis of materials at nano scale is one of the main challenges in nanotechnology for different applications such as semiconductor, superconductors, electro-optics devices, advanced ceramics, refractories, diagnostic imaging and drug delivery. Semiconductors nanocrystals, known as “Quantum Dots”, have emerged as new generation of nanomaterials due to their unique optical, electrical and electrochemical properties, for variety of applications such as contrasts agents, fluorescent labels, localized targeted drug delivery and new generation of biosensors. Quantum dots advantages over traditional nanomaterials are due to quantum confinement effect, which bring broad absorption spectra, superior brightness and durability for different applications. The most important factor in developing nano carriers for biological applications is the toxicity, so recent researches have been focused on heavy metal-free formulations and nontoxic ceramics and polymers. So, one of the main goals in this paper is to explicate efficiencies and deficiencies of recent advances in quantum dot based formulations with the least toxicity for bioimaging, therapeutic and drug delivery applications. Another area of quantum dot’s application is the determination of dopamine (DA). Due to basic role of DA in some diseases like Parkinson and Schizophrenia, its determination is important and thus, it is desirable to develop new, simple and rapid analytical methods for the determination of DA with high selectivity and sensitivity, especially for diagnostic applications. Recently, developments in nanotechnology and preparations of semiconductors quantum dots cause open a new field in photo-electrochemical methods based on semiconductors quantum dots for determination of DA. In this review, an attempt was made to elaborate the mentioned goals of the paper in details.
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.
V. Usov, M. Rabkina, N. Shkatulyak, E. Savchuk, O. Shtofel,
Volume 17, Issue 4 (12-2020)
Abstract
The aim of this study is to establish the correlation between the impact strength and texture, fractal dimensions of fractures , fractal dimensions obtained from load-time diagrams reflecting the applied load (P) dependence on time (τ) during the Charpy impact test of 20K steel at various temperatures as well as the comparison of abovementioned fractal dimensions. The tests were carried out on a vertical impact testing machine with a multi-channel system for high-speed registration of forces and strains, as well as a heating and cooling system for samples in a wide temperature range. The load vs. time (load dependence on time) diagrams were obtained at an impact velocity of = 4.4 m/s at temperatures of -50, +20, + 50°С. The Charpy standard samples of 20K steel (analogue to DIN17175, class St45.8) were cut in various directions out of a 12 mm thick the destroyed tank shell of a distillation column for oil refining. It was established that the behavior of both abovementioned fractal dimensions depending on the cutting direction and test temperature coincides qualitatively. The trend of decreasing in fractal dimension with a more viscous nature of fracture was found. The effect of texture is discussed.
S. Das, R. Ghadai, A. Krishna, A. Trivedi, R. Bhujel, S. Rai, Sh. Ishwer, K. Kalita,
Volume 17, Issue 4 (12-2020)
Abstract
Graphene oxide (GO) and reduced graphene oxide (rGO) is a semiconductor device which finds its many applications in the various electronic devices. In the present study GO and rGO thin sheets have been grown over Si wafers using Hummer’s and modified Hummer’s method and a comparison in the properties of the coatings have been carried out. The morphology of the sheets characterized by SEM revealed similar transparent sheet like structure for both the chemical synthesis. The diffraction pattern of GO and rGO prepared with modified Hummer’s method showed peak shift to lower diffraction angle from 9.96 o to 9.63 o and 26.4 o to 26.3 o respectively. The diffraction peaks were observed at diffraction phase of 001 and 002 crystal plane. FTIR spectra revealed presence of oxygen functional groups in GO thin sheets whereas peaks for oxygen functionalities are absent in rGO. The polarization curve indicated similar corrosion resistance of GO and rGO thin sheets grown under Hummer’s and modified Hummer’s. Capacitive property of rGO is better than GO as observed by the electrochemical analysis of GO and rGO..Graphene oxide (GO) and reduced graphene oxide (rGO) is a semiconductor device which finds its many applications in the various electronic devices. In the present study GO and rGO thin sheets have been grown over Si wafers using Hummer’s and modified Hummer’s method and a comparison in the properties of the coatings have been carried out. The morphology of the sheets characterized by SEM revealed similar transparent sheet like structure for both the chemical synthesis. The diffraction pattern of GO and rGO prepared with modified Hummer’s method showed peak shift to lower diffraction angle from 9.96 o to 9.63 o and 26.4 o to 26.3 o respectively. The diffraction peaks were observed at diffraction phase of 001 and 002 crystal plane. FTIR spectra revealed presence of oxygen functional groups in GO thin sheets whereas peaks for oxygen functionalities are absent in rGO. The polarization curve indicated similar corrosion resistance of GO and rGO thin sheets grown under Hummer’s and modified Hummer’s. Capacitive property of rGO is better than GO as observed by the electrochemical analysis of GO and rGO.
S. M. Alduwaib, Muhannad M. Abd,
Volume 17, Issue 4 (12-2020)
Abstract
Graphene oxide thin layers, graphene oxide:silver nano-composite, graphene oxide:zinc oxide nano-composite and graphene oxide:zinc oxide/graphene oxide:silver bilayer were deposited by spray pyrolysis method. The synthesized thin layers were characterized using X-ray diffraction spectroscopy, field emission scanning electron microscope, energy dispersive x-ray spectroscopy and Raman spectroscopy. The optical properties and the band gap of the thin layers were also studied and calculated using the Tauc equation. Gram-negative bacterium of Escherichia coli was used to study the antibacterial properties of thin layers. The results showed that among the thin layers investigated, GO:ZnO/GO:Ag bilayer had the greatest effect on the inhibition of E. coli growth and was able to control the growth of bacterium after 2 hours.
Jafar Shafaghat, Ali Allahverdi,
Volume 18, Issue 1 (3-2021)
Abstract
Microscopic studies has shown that adjacent to the interface between cement paste and aggregate, there exists an area with high porosity and low binding compounds that is referred to as interfacial transition zone (ITZ). ITZ in concrete and mortar imposes a number of negative effects, including flexural and compressive strengths reduction and permeability enhancement. That’s why many research attempts have been devoted to limit ITZ and its negative effects. The present study investigates the possibility of utilizing fine Portland cement (PC) clinker as a reactive aggregate in mortar for the same purpose. For this, natural quartz sand in normal mortar (NM) was totally replaced with PC clinker of the same particle size distribution and the most important engineering properties of the new mortar referred to as Reactive Aggregate Mortar (RAM) were measured and compared with NM as control. The results of compressive strengths measurements represented 65% and 21% increases at curing ages of 7 and 90 days, respectively, for RAM compared to NM. Chloride penetration depth in RAM displayed reductions by about 33% and 26% after 14 and 28 days of exposure, respectively. The effect of PC clinker reactivity on the microstructure and size of ITZ was studied by using scanning electron microscopy.
Mahnaz Mohammadzadeh Mianji, Hossein Sarpoolaky, Mehrnoush Shafiei Sararoudi,
Volume 18, Issue 1 (3-2021)
Abstract
Translucent porcelain with appropriate workability has been considered beneficial for light and shadow to be used in the production of ceramic artworks. In addition, using low firing temperature encourages more artists to use this body. The soft-paste cellulose composite porcelain is composed of similar amount of high Borax/Calcia leadless frit and Kaolin with 3% Vee gum T as a plasticizer. In order to increase workability and green strength, five units of soft-paste porcelain (SP) slip was mixed by one unit bleached bagasse pulp of sugar cane slip in volume and then cellulose containing soft-paste porcelain (CSP) slip was made. The samples were formed by hand, dried and then fired at the optimum temperature of 1120 for 5 hours. Results showed that the SP sample became self-glazed after firing while cellulose increased porosity in CSP. Microstructure analysis showed a large amount of glass phase, which improved translucency of the bodies. Moreover, mullite needle-shaped crystals were derived from the flux-penetrated clay because of less viscous molten body matrix. XRD results clearly showed that the fritted soft-paste porcelain consists of quartz, mullite, anorthite and albite in the fired state. Spectrophotometry showed that adding cellulose to the porcelain body slightly increased translucency in the wavelength ranges 400 to 500 nm.
Alireza Mirak,
Volume 18, Issue 2 (6-2021)
Abstract
In the present study, the early stages of the surface oxidation and fluoridation of liquid AZ91D and AM60B alloys under ultra-high purity (UHP) argon, dry air, and air mixed with two different protective fluorine-bearing gases were studied. The chemical composition, morphology and thickness of the surface films formed inside the trapped bubbles were characterized by SEM and EDS analyses. It is found that the molten AM60B alloy is more sensitive to impurities under UHP argon gas than AZ91D alloy. Under dry air atmosphere, the entire surface of molten AZ91D alloy is covered with an oxide layer and thinner thickness than the surface film formed on AM60B alloy which has a rough surface exhibiting granular growth in later stages of oxidation. The EDS analyses show that film chemistry is mainly composed of Mg, Al, and O elements. Under fluorine-bearing gas/air mixtures with either SF
6 or HFC-R134a at 3.5%vol., a fresh surface film formed with a flat and dense morphology of a uniform thickness composed of mixed Mg, F, Al, and O elements. It is observed that there is a lower O:F intensity ratio in the surface film formed on the molten AZ91D alloy under 1,1,1,2-tetra-fluoroethane (HFC-R134a) mixed with dry air compared to the AM60B alloy under both air/ R134a and air/SF
6 mixtures which shows a higher fluorine concentration in the surface film a leading to a better oxidation resistance
.
Gholam Hussein Borhani, Saeed Reza Bakhshi, Sadegh Soltani,
Volume 18, Issue 2 (6-2021)
Abstract
In this study, Ta powder was produced from Ta scarp via chemical processes using Mg and Ca powders. At first, Tantalum scraps were converted to Tantalum oxide (Ta2O5) at 1100˚C in an oxygen atmosphere. Tantalum oxide was reduced to Tantalum powder with Mg in a vacuum environment at 950 to 1200˚C for 3 hours. The obtained Ta powders further were reacted with Ca at 950˚C for 5 hours in a vacuum atmosphere. The powders were analyzed through X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), as well as oxygen measurement. The results show that the average particles size of the produced Ta powders is about 58 nm with oxygen contents of 250 ppm.
Sedigeh Mohamadnejad Zanjani, Ali Basti, Reza Ansari,
Volume 18, Issue 2 (6-2021)
Abstract
Phenomenological methods are more diagnostic tools than a predictor, so multi-crystalline material approaches based on their microstructures have been proposed during the last years. The purpose of this research is to review methods taking into account the effect of microstructures and texture deformation on predicting the behavior of sheet metals. These methods can be categorized into six general groups: Taylor-type models, crystal plasticity finite element methods, strain gradient methods, methods that consider dislocations, self-consistent methods, methods based on fast Fourier transform. This paper attempts to explain and compare these methods that have been used to forecasting forming limits or stress-strain curves.
