Showing 29 results for Duct
M.r. Saeri, M. Azizi1, R. Amooaghaie,
Volume 34, Issue 4 (3-2016)
Abstract
Bio-inspired silver nanoparticles were synthesized with the aid of a novel method, using leaves of the plant Nigella sativa. After drying the leaves in air, they were first sweltered in boiling distilled water and the liquid was filtered subsequently. The result was the brothused to reduce solutions including various concentrations of silver nitrate in a proper amount of pH. The displayed UV–visible spectra identified formation of silver nanoparticles whenever the colorless initial acclimated mixture turned brown. The centrifuged powder samples were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (FESEM) and energy dispersive X-ray diffraction analysis (EDX) methods. The results clearly revealed that the final particles of precipitated powder are high purity agglomerates of silver nanoparticles. Besides, the effects of various amounts of the silver salt on particle size of nano silver were studied, using a particle size analyzer. FTIR results also indicated the role of different functional groups in the synthetic process.
B. Avishan,
Volume 35, Issue 4 (2-2017)
Abstract
Presence of nanoscale bainitic ferrites and high carbon retained austenites that are stable at ambient temperature within the microstructures of super strong bainitic steels makes it possible to achieve exceptional strengths and ductility properties in these groups of nanostructured steels. This article aims to study the effect of the dislocation density variations during tensile testing in ambient temperature on deformation behavior of nanostructured low temperature bainitic steels. Results indicate that dislocation absorption from bainitic ferrite subunits by surrounding retained austenite reduces the work hardening and therefore increases the formability of bainitic ferrite during deformation, which in turn results in a suitable combination of strength and ductility.
A. Amiri Moghaddam, M. Kalantar,
Volume 36, Issue 1 (6-2017)
Abstract
The aim of this investigation is obtaining WC-Co composite powder from WO3 and Co3O4 by in-situ and carbothermic reduction method using activated carbon as a reducing agent. In this study, cobalt and tungsten oxide powders with 17% carbon (30% more than stoichiometric value) were mixed by ball-milling under atmosphere of argon for 20 hours. Differential Thermal Analysis (DTA) and Thermal Gravimetric Analysis (TGA) results on powder mixture show complete reducing of oxides at 1050°C and forming cobalt carbide and tungsten carbide. Compact samples underwent carbothermic reduction at 1050 °C for different times of 1, 2 and 4 hours with protective layer of alumina and carbon powder mixture with ratio of 1:1. Based on X-Ray Diffraction (XRD) analyses, the best holding time in furnace is 4 hours, in which tungsten reduction and carbonization is completed. XRD evaluation of reduced compacted samples in three conditions of atmosphere protective layer of alumina and carbon powder mixture with ratio of 1:1, protective foil of refractory steel and argon, shows that unreduced oxides and extra phases are present in argon atmosphere and protective foil of steel but not in alumina and carbon mixture layer. The measurement results of physical and mechanical properties on the sintered composite sample in heating rate of 5 °C /min to temperature 1500 °C and the holding time of 2 hours under a shielding layer of alumina and carbon shows obtaining the optimal properties (Pr=80%, KIC=8.1 MPa , MHV=15.67GPa) comparable to that of advanced and costly methods.
M. Illbeigi, A. R. Fazlali, M. Kazazi, A. H. Mohammadi,
Volume 36, Issue 1 (6-2017)
Abstract
In this research, new lithium ion conductor glass-ceramics with NASICON-type structure (Li1+x+yAlxCryGe2-x-y (PO4)3, x+y=0.5) were synthesized using melt-quenching method and converted to glass-ceramics through heat treatment. Influence of addition of different concentrations of aluminum and chromium in LiGe2(PO4)3 glass-ceramic was investigated for ionic conduction improvement. Substitution of Ge4+ ions in NASICON structure by Al3+ and Cr3+ ions induced more Li+ ions in A2 vacant sites to obtain charge balance and also changed the unit cell parameters. These two factors led to ionic conductivity improvement of synthesized glass-ceramics. The glass-ceramics were characterized and the amorth structures were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Differential Scanning Calorimetry (DSC) and Complex Impedance Spectroscopy (CIS). The highest lithium ion conductivity of 8.82×10-3 S/cm was obtained for x=0.4 and y=0.1 (Li1.5Al0.4Cr0.1Ge1.5(PO4)3) crystallized at 850 oC for 8 h with minimum activation energy of 0.267 eV.
M. Samii Zafarghandi, S. M. Abbasi,
Volume 38, Issue 2 (9-2019)
Abstract
In the present work, hot tensile behavior of Haynes 25 Co-base alloy was investigated in the temperature range of 950-1200 ˚C and 0.1 s-1. Thermodynamic calculations showed that M23C6 and M6C carbides were stable below 1000 ˚C and above 1050 ˚C, respectively. Stress-strain curves also indicated an unusual trend of strain fracture. It was observed that with increasing temperature from 950 to 1050 ˚C, the fracture strain was decreased, while it was raised above 1050 ˚C again. Increasing the volume fraction of M6C carbide rich in Tungsten resulted in the loss of ductility. Also, microstructural evaluations showed dynamic recrystallization (DRX) grains were nucleated and growth was around carbides and the initial grains at 1150 ˚C. Occurrence of DRX led to the improvement of ductility via grain refinement mechanism, so this alloy had the highest level of ductility at 1150 ˚C
M. T. Asadi Khanouki, R. Tavakoli , H. Aashuri,
Volume 38, Issue 2 (9-2019)
Abstract
In this research, the effect of temperature on the mean size of fracture surface features, as well as the relation between fracture surface morphologies and ductility of a La-based BMG as a relatively brittle alloy, was systematically investigated. After producing the alloy, three-point bending experiments, over a wide range of temperatures, were conducted on the samples; then the fracture surfaces were analyzed using scanning electron microscopy. The results demonstrated that the width of stable crack growth region (ΔW) was increased upon ductility (δp). Conversely, the mean size of the features on both stable (Ds) and fast (Df) crack growth regions and also, shear offset width (ΔL) were found to decrease with increasing ductility. In this case, the shear band instability was reduced, and the plastic strain could be more homogeneously distributed on the shear bands. The similarity of ΔL and Ds values suggested that the formation of vein pattern was caused by steak-slip behavior and multiple-step sliding inside the shear band through the fluid meniscus instability mechanism. Furthermore, the results obtained from correlation between ductility and fracture surface morphologies in the BMG indicated that the size of features was reduced with increasing ductility.
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.
M. Kamali Ardakani , M. Morakabati,
Volume 40, Issue 2 (9-2021)
Abstract
The aim of this study was to investigate the behavior of hot deformation and occurrence of restoration phenomena during the deformation of AISI H10 hot work tool steel. For this purpose, hot tensile test was performed on the steel in the temperature range of 900-1150 ºC with a temperature interval of 50 ºC and at a constant strain rate of 0.1s-1. The microstructures were examined and the curves of hot flow and ductility were drawn. According to the curves and microstructures, ductility was lower at temperatures of 900 ºC and 950 ºC due to inactivity of repair processes and the presence of carbides. Ductility increased in the temperature range of 1000-1100 ºC due to the occurrence of dynamic recrystallization. Finally, ductility decreased in the temperature of 1150 ºC due to the dissolution of carbide particles and grain growth. The results obtained from hot tensile test and microstructural studies at a constant strain rate of 0.1s-1 revealed that the appropriate temperature range for deformation of AISI H10 hot work tool steel was 1000-1100 ºC.
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.
