Showing 306 results for Co
S. Borhani Esfahani, H. R. Salimi Jazi, M. H. Fathi, A. Ershad Langroudi, M. Khoshnam,
Volume 40, Issue 1 (5-2021)
Abstract
In this research, a kind of environmentally-friendly inorganic-organic hybrid nanocomposite coating based on silica containing titania/silica core/shell nanoparticles was synthesized and characterized for conservation of facade tiles in historical buildings. The matrix of the composite was prepared by sol-gel process via two methods of ultrasonic and reflux stirring. Tetraethyl orthosilicate (TEOS) and poly-dimethyl siloxane hydroxy-terminated (PDMS-OH) were used for the formation of silica network and creation of flexibility and hydrophobicity, respectively. Titania nanoparticles were used in the form of titania/silica core/shell as ultraviolet absorber. The synthesized nanocomposite was applied on the microscope slides and tiles by dip coating technique. The properties of nanoparticles and coatings were characterized by Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and water contact angle measurement. The results revealed that formation of titania/silica core/shell structure was successful. The investigation of PDMS content effect on transparency, cohesion and hydrophobicity of the coating confirmed that the optimum content of this siloxane was around 20 wt.%. In general, the results showed that the silica-based hybrid nanocomposite reinforced with TiO2/SiO2 core/shell nanoparticles could produce a transparent and hydrophobic coating for tile and glass protection.
H. R. Karimi, H. Mansouri, M. R. Loghman Estarki, M. Tavoosi , H. Jamali,
Volume 40, Issue 1 (5-2021)
Abstract
This study aimed to compare the phase changes and morphology of yttria-stabilized zirconium oxide powders (YSZ) synthesized by co-precipitation and molten salt methods. Ammonia precipitating agent was used for the synthesis of YSZ powder by co-precipitation method and a mixture of sodium carbonate and potassium carbonate salts was used as a molten salt in the molten salt method. Samples were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC) analysis. The results showed that only the sample prepared with zirconium oxychloride and yttrium nitrate by co-precipitation method had a single phase of yttria-stabilized zirconium oxide with tetragonal crystal lattice and particle size distribution in the range of 30 to 55 nm. The powder synthesized by the molten salt method contained a mixture of zirconia with monoclinic crystal lattice and yttria stabilized zirconia with tetragonal crystal lattice and particle size of 200 nm.
R. Amirarsalani, M. Morakabati, R. Mahdavi,
Volume 40, Issue 1 (5-2021)
Abstract
In this research, the hot deformation behavior of W360 tool steel was investigated using hot compression test at 1000-1200°C and strain rates of 0.001, 0.01, 0.1, and 1 s-1. According to the results, dynamic recrystallization was found the most important restoration factor of this alloy during hot deformation. Recrystallization was enhanced with an increase in temperature and strain rate. Also, the hot working process was optimized by drawing the processing map of this steel. Microstructural images obtained from the hot compression test showed that recrystallization started at 1000°C and the strain rate of 0.01 s-1 and developed with increasing temperature and strain rate due to an increase in the stored energy and suitable regions for nucleation. The results of drawing the processing map showed that the best hot deformation region was the temperature range of 1050-1150°C and strain rates of 0.1-1 s-1.
M. Khosravi , M. Mansouri, A. Gholami, Y. Yaghoubinezhad,
Volume 40, Issue 1 (5-2021)
Abstract
In this research, the effect of graphene oxide (GO) and reduced graphene oxide (RGO) nanosheets on the mechanical and microstructural properties of AISI 304 stainless steel welded joints produced by the flux-cored arc welding (FCAW) method was investigated. Light microscope, field emission scanning electron microscope (FE-SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), Raman spectroscopy, and tensile strength test were used to characterize the samples. GO was synthesized by modified Hummers’ method and reduced by hydrazine. Accordingly, the pastes of GO and RGO in different concentrations of 1, 3, and 10 mg/ml were applied in the groove. The results demonstrated that increasing the RGO concentration up to 10 mg/ml improves the tensile strength and hardness values of welded joints up to 23% and 43%, respectively. It seems that RGO nanosheets have a significant effect on the mechanical properties of the welded joints by pinning of dislocations.
S. Shahzamani, M. R. Toroghinejad, A. Asharfi,
Volume 40, Issue 2 (9-2021)
Abstract
In this study, Al/Al2O3 composite was produced by accumulative roll bonding (ARB) process coupled with the plasma electrolytic oxidation (PEO) process. The alumina was grown on Al sheets by electrolyte technique with three different thicknesses (10, 20, and 40 µm). The results showed that incorporation of alumina up to 3.22 vol.% in aluminum matrix enhanced the yield and tensile strength of the composite, whereas increasing the amount of alumina up to 6.25 vol.% deteriorated the tensile properties. In the last part, a serial sectioning process was employed to develop a three-dimensional (3D) representation of the microstructure of Al2O3 particles reinforced Al composite for visualization and finite-element modeling (FEM).
H. Fallah-Arani, S. Baghshahi, A. Sedghi, F. Shahbaz Tehrani,
Volume 40, Issue 2 (9-2021)
Abstract
In this research, the influence of titanium dioxide nanoparticles on the structural and magnetic properties of high-temperature superconductor Bi1.6Pb0.4Sr2Ca2Cu3O10+θ (Bi-2223) from the Bi-based ceramic system (BSCCO) was studied. In order to investigate the synthesized samples, X-ray diffractometry and magnetic measurements were performed. Based on the magnetic measurements, the superconductivity transition temperature declined with the increase in the nanoparticles' content. The addition of nanoparticles affected on the hysteresis loop width. Accordingly, the compound containing 0.2 wt.% nanoparticles had the maximum magnetization, hysteresis loop width, and critical current density.
R. Bagheri, F. Karimzadeh, A. Kermanpur , M. Kharaziha,
Volume 40, Issue 2 (9-2021)
Abstract
A new method has been presented for the synthesis of copper (Cu)/copper oxide (CuO)-nanoparticles (NPs), based on the process of corrosion and oxidation of Cu-NPs on the surface of the gold electrode by nitric acid. Cu-NPs were deposited on the surface using potentiometric method. The high concentration of Cu-NPs was estimated by Differential Pulse Voltammetry (DPV). The process of growth and distribution of CuO-NPs on the surface of Cu-NPs using structural analysis of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) showed that nitrate was well absorbed and a sharp hydroxyl peak appeared and a phase of CuO NPs formed on the electrode surface. The surface morphology indicated that the average size reduced from about 150 nm to 50 nm in the presence of nitrate. This can be due to the oxidation of Cu nanoparticles on the surface and reduction of particle size compared to the absence of nitric acid. This simple and low-cost method can be used as a surface modification of antibacterial and active catalyst electrodes.
M. Salehi, M. Eskandari, M. Yeganeh,
Volume 40, Issue 2 (9-2021)
Abstract
In this study, microstructural changes in the thermomechanical processing and its effect on the corrosion behavior of 321 austenitic stainless steel were investigated. EDS analysis and optical microscopy were used to identify precipitates and microstructure, respectively. To evaluate the corrosion properties, potentiodynamic polarization test and electrochemical impedance spectroscopy were performed. First, the as-received sample was subjected to cold rolling with a 90% thickness reduction at liquid nitrogen temperature, and then annealing was performed at temperatures of 750, 850, and 1050 °C for 10 min. The results showed that severe cold rolling slightly improved the corrosion properties and in annealed samples, the corrosion resistance increased with more uniform microstructure, more reversion of martensite phase to austenite, and reduction of grain size. Annealed samples at 850 °C and 1050 °C with polarization resistance values of 8.200 kΩ.cm2 and 3.800 kΩ.cm2 depicted the highest and lowest corrosion resistance compared to other samples, respectively.
F. Fareghdeli, M. Karimi, A. Novin, M. Solati-Hashjin,
Volume 40, Issue 3 (11-2021)
Abstract
One challenge in preparing polymer/ceramic composites is non-uniform ceramic particles distribution in a polymer matrix. This research evaluated the effect of stirring time and temperature on hydroxyapatite (HA) distribution through (polylactic acid) PLA matrix. Therefore, to mix the ceramic suspension with the polymer solution, three temperatures, namely 25, 37, and 45°C and four times including 6, 12, 24 and, 48 h were examined. Fourier-transform infrared spectroscopy (FTIR) analysis was used to investigate the bonds, which showed physical bond formation such as carboxyl-calcium-carboxyl between HA and polymer matrix, influenced on particles distribution. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) were used to observe particles distribution and determine samples homogeneity. To fulfill this goal, each obtained photograph representing the calcium presentation was split into nine equal sections, and a method based on the newly defined index called dispersion factor “α” was used to analyze the distribution. Results showed that the sample prepared at 37°C and 48 h had the topmost homogeneity properties.
P. Verdi, S. M. Monirvaghefi, F. Ashrafizadeh,
Volume 40, Issue 3 (11-2021)
Abstract
Regarding to the low rate of conventional Ni-P electroless plating method that needs more time to make a coating on the substrate surface, a new technique called “substrate local heating” was introduced based on the temperature parameter modification and its advantages were expressed and compared to the conventional electroless plating technique (temperature=90°C, pH=4.7). In order to provide necessary equipment making this approach practicable, electrical resistance was used as the heating source, and air injection and cooling water circulation were employed to control the solution temperature near the substrate and in the bulk solution, respectively. Considering the heater power (1000 W), the substrate and bulk temperatures were about 190°C and 80°C, respectively. This novel method could enhance the plating rate up to 32 µm/h which was about 60% greater than that of the conventional method, 20 µm/h. Moreover, benefits such as local plating, reduction of production costs, and formation of functionally graded coatings (FGC) can be achieved.
O. Ganji, S.a. Sajjadi, M. Mirjalili, Z.g. Yang,
Volume 40, Issue 4 (3-2022)
Abstract
Carbide coatings, due to their excellent anti-wear properties, are used to extend the life of molds exposed to abrasion forces. Various processes have been applied to produce carbide coatings. Thermo-reaction diffusion (TRD) using a molten salt bath could be considered as an economical method compared to other coating processes. In this study carbide-composite coatings using molten salt baths composed of oxides of carbide forming elements (chromium and vanadium) on SKD-11 and T10 tool steels at 1000 ℃ were formed. The results showed that the coatings included chromium carbide phases: CrC, Cr7C3, and Cr23C6 as well as vanadium carbide: VC, VC0.88, V6C5, V8C7, and a triple phase with the composition of Cr2C2V. The highest hardness (1890-2020 HV) and the lowest coefficient of friction (0.14) were achieved by the carbide coating of T10 steel with the second bath of vanadium oxide.
N. Ghobadi, S. A. Hosseini Moradi, M. Amirzade,
Volume 40, Issue 4 (3-2022)
Abstract
In this research, cobalt ferrite powders (CoFe2O4) and cobalt ferrite/reduced graphene oxide composite (CoFe2O4/RGO) were synthesized by the co-precipitation method. The phase structure, morphology, magnetic properties, and microwave absorption properties of the produced samples were investigated through various techniques. X-ray diffraction test indicated the successful formation of pure CoFe2O4 and its composites with RGO. According to the Scanning electron microscopy (SEM) images, most pure and composite samples’ particles were formed in a semi-spherical shape. The VNA test results showed the saturation magnetization of CoFe2O4 and the composite containing 5 wt.% and 10 wt.% of RGO, 71.6, 56, and 37 emu/g, respectively. Also, the network analyzer results demonstrated the maximum reflective losses in the X-band range due to the impact of microwaves on CoFe2O4 te was -5.5 db. This amount reached 21.5 dB with the addition of 10 wt.% RGO. Also, the wave input increased from 41% for the pure CoFe2O4 to 99.5% for the sample containing 10 wt.% RGO.
H. Fallah-Arani, N. Riahi-Noori, S. Baghshahi, A. Sedghi, F. Shahbaz Tehrani,
Volume 40, Issue 4 (3-2022)
Abstract
In this research, the effect of addition of silicon carbide (SiC) nanoparticles on the improvement of the structural, superconductivity, magnetic, and flux pinning properties of high-temperature superconductor Bi1.6Pb0.4Sr2Ca2Cu3O10+θ (Bi-2223) was investigated. The Bi-2223 ceramic superconductor was prepared using the sol-gel method, and silicon carbide nanoparticles were modified by Azobisisobutyronitrile (AIBN). The X-ray diffractometry, feild emission scanning electron microscopy, magnetic susceptibility, and hystersis loop measurements were performed to characterize the synthesized compounds. Based on the magnetic measurements, the superconductivity transition temperature dropped with an increase in the content of nanoparticles. Also, the maximum magnetization, hysteresis loop width, critical current density, and magnetic flux pinning force belonged to the sample with 0.4 wt.% SiC nanoparticles.
M. H. Rezvani, M. Yeganeh, S. M. Lari Baghal,
Volume 41, Issue 1 (8-2022)
Abstract
In this study, the addition of organic methionine inhibitor (as an eco-friendly inhibitor) to 0.1 M sulfuric acid media on corrosion resistance of 316L austenitic stainless steel (fabricated by rolling method and three-dimensional (3D) printing method) was investigated. Open-circuit potential electrochemical test and impedance, and structural tests such as optical and electron microscopy and x-ray photoelectron spectroscopy were conducted. The results showed that the corrosion resistance in the presence of inhibitor was higher than the sample without inhibitor and the inhibitory efficiency of methionine was increased up to 64% and the resistance to surface transfer between metal oxide and electrolyte was improved up to 2.77 times. The addition of methionine reduced the surface roughness and accumulation of the surface cavities. The chemical and physical adsorption mechanism of the inhibitor (negatively charged side adsorption of the methionine molecule with positively charged anodic regions of the metal surface) occurred at all points on the surface of the sample with the inhibitor. Also, the amount of oxygen in the cavities was reduced and the distribution of sulfur was uniform. The thickness of the passivator oxide layers was calculated more than the sample without inhibition due to the addition of inhibitor.
F. Dehghani Firoozabadi, A. Ramazani Saadatabadi, A. Asefnejad,
Volume 41, Issue 1 (8-2022)
Abstract
Today, many people need to use bone grafts and implants because of damage to bone tissue. Due to the stimulation of the immune system after implantation, infection at the operation site is very common, which causes swelling and pain in the operation area. The use of zinc oxide nanoparticles reduces infection at the operation site and reduces the patient's need for antibiotics. In the present study, the morphology of the scaffolds was investigated by field emission scanning electron microscope (FE-SEM). The toxicity of the samples was evaluated using MTT assay. The behavior of nanocomposites against Escherichia coli and Staphylococcus aureus was investigated by measuring the diameter of the growth inhibition zone. It was found that modification of scaffolds with nanoparticles caused a growth inhibition in bacterial culture medium. It was also observed that fibroblast cells on the surface of the modified scaffolds had longer survival than polymer scaffolds. This study showed that the addition of oxidizing nanoparticles improves the antibacterial properties of scaffolds and cell viability and reduces scaffold toxicity.
R. Zarei, E. Mohammadsharifi, M. R. Loghman, M. Ramazani, Kh. Zamani,
Volume 41, Issue 1 (8-2022)
Abstract
The present research has examined the effect of adding Si3N4 on the mechanical and structural properties of NiCrAlY alloy. The structural and mechanical properties of the manufactured samples were characterized by SEM, XRD, micro-hardness evaluation and pin on disk wear test. Various concentrations of Si3N4 powder (1, 3, and 5 wt.%) were mixed with NiCrAlY powder using a mechanical ball mill. Next, the mixtures were sintered at 1100 °C using the spark plasma sintering (SPS) technique. The XRD patterns indicated that the samples were composed of two phases of solid solution γ-Ni(Cr) and intermetallic compounds β-NiAl. The results of micro-hardness measurements showed that adding 1% Si3N4 to NiCrAlY enhanced the hardness from 418 to 614 HV. However, with an increase in the Si3N4 content from 1 to 5 wt%, the hardness diminished from 614 to 543 HV, and by Adding Si3N4 to the NiCrAlY, its tribological properties were significantly improved.
Sh. Talebniya, M. R. Saeri, I. Sharifi, A. Doostmohammadi,
Volume 41, Issue 1 (8-2022)
Abstract
Magnetic nanoparticles are of interest in various research fields such as magnetic fluids, catalysts, biotechnology, medicine, information storage, and environmental issues. However, spinel ferrite magnetic nanoparticles with proper magnetic properties could not be used alone in these applications because of their lack of biocompatibility and instability in aqueous solutions. Surface coating is an effective strategy to eliminate or minimize this issue. In this study, FeFe2O4 and ZnFe2O4 spinel ferrites were synthesized using the reverse co-precipitation method under a nitrogen gas atmosphere. The magnetic behavior of the particles, determined by a vibrating magnetometer (VSM) showed the saturation magnet (Ms) values of the FeFe2O4 and ZnFe2O4 spinel. Fourier-transform infrared (FTIR) spectra showed two high-frequency bands v1 and v2 at about 554-578 and 368-397 cm-1, respectively, which were related to the spinel structure. Finally, the synthesized FeFe2O4 nanoparticles were coated with chitosan and polyethylene glycol (PEG) biopolymers. The TEM and FTIR analysis indicated that the magnetic nanoparticles were uniformly coated by the biopolymers.
N. Mohammadi, B. Lotfi,
Volume 41, Issue 2 (11-2022)
Abstract
The purpose of this study was to improve the erosion behavior of Inconel 625 alloy by plasma transferred arc-deposited stellite6/B4C composite cladding. For this purpose, 5 wt.% of boron carbide was added to the stellite6 clad. Phase analysis and microstructure evaluation were conducted by Optical Microscope, Field Emission Scanning Electron Microscope (FESEM), and Energy-dispersive Spectroscopy (EDS). Solid particle erosion tests with silica particles at 30˚ and 90˚ impact angles were performed to study the erosion behavior. Eroded surfaces were observed by SEM. Investigations showed that the addition of boron carbide particles caused finer microstructure in composite cladding. Moreover, hardness increased with adding boron carbide. Maximum erosion resistance was achieved at 30˚ impact angle. The weight loss of composite cladding were 20 % and 33 % compared to those obtained in Inconel 625 substrate and stellite6 cladding, respectively. The weight loss of the claddings and substrate showed negligible difference at 90˚ impact angle. The dominant mechanism of erosion for composite cladding at 30˚ impact angle was suggested to be cutting and detachment of reinforcing particles. Crater formation was found the predominant mechanism of erosion at 90˚ impact angle.
B. Sharifian, G. H. Borhani, E. Mohammad Sharifi,
Volume 41, Issue 2 (11-2022)
Abstract
In this study, mechanically milled (MM) Al-24TiO2-20B2O3 powder in molten Al7075 matrix was used in order to fabricate in-situ TiB2 and Al2O3 reinforcements in Al7075 matrix. Differential thermal analysis (DTA) examination was adopted to find reaction temperature between milled Al, TiO2, and B2O3 powders. X-Ray Diffraction (XRD) patterns showed the existence of TiB2 and Al2O3 peaks (750 °C at Ar atmosphere) in MM powder. Scanning Electron Microscopy (SEM) results revealed the uniform distribution of TiO2 and B2O3 particles in the aluminum matrix. 6 wt.% MM powder was added to molten Al7075 at 750 °C. The molten Al7075/TiB2-Al2O3 composite was poured in copper mold. The stir casted composites were hot extruded at 465 °C with extrusion ratio of 6:1 and ram speed of 5 mm/s. The microstructures (optical microscopy and TEM) and mechanical properties (hardness and tensile testing) of samples were evaluated. TEM results showed that in-situ TiB2 nanoparticles were formed. The tensile strength of extruded Al7075/TiB2-Al2O3 composite was reached the value of 496 MPa. This result was around four times greater than that of the as cast Al7075 alloy.
A. Azimi-Fouladi , S.a. Hasanzadeh-Tabrizi,
Volume 41, Issue 2 (11-2022)
Abstract
Water pollution is one of the big problems of human societies, and the need to find new ways to remove these pollutants has been given much attention in recent years. One of the methods is the use of photocatalysts. In this research, TiO2 and TiO2-CdO nanoparticles were prepared by a sol-gel method as nano photocatalysts. The produced samples have been used to degrade methylene blue under UV light. To characterize the prepared samples, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), X-ray Energy Diffraction Spectroscopy (EDS), and Ultraviolet-Visible Spectroscopy (UV-Vis) were used. Microstructural results revealed nanoparticles with dimensions of 18 to 32 nm. XRD results showed that the main phase formed was the anatase. TiO2-4 wt.% CdO nanocomposite showed more photocatalytic activity compared to pure TiO2. Also, the effect of pH, irradiation time, and amount of powder on photocatalytic activity was investigated. The results showed that at pH=9, time of 75 min, and using 0.02 g TiO2-4 wt.% CdO photocatalyst, the maximum photocatalytic activity of about 92 % was obtained.
