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Tensile deformation mechanisms at different temperatures in the Ni-base superalloy GTD-111
, Article Journal of Materials Processing Technology ; Volume 155-156, Issue 1-3 , 2004 , Pages 1900-1904 ; 09240136 (ISSN) ; Nategh, S ; Isac, M ; Zebarjad, S. M ; Sharif University of Technology
2004
Abstract
The Ni-base superalloy GTD-111 is employed in high-power stationary gas turbines because of its high temperature strength and oxidation resistance. The temperature dependence of the tensile behavior of GTD-111 has been studied by tensile tests in the temperature range of 25-900°C with a constant strain rate of 10-4s-1. The results showed an abnormal tensile property variation with increasing temperature. The yield strength decreased slightly with temperature up to about 650°C and then increased between 650 and 750°C. Above 750°C, a rapid decrease in the yield strength was found. The tensile strength showed a similar behavior except for its maximum that occurred at 650°C. The elongation...
Synthesis and properties of MWCNT-HAP composites via sol-gel technique
, Article Iranian Journal of Materials Science and Engineering ; Volume 10, Issue 2 , 2013 , Pages 57-63 ; 17350808 (ISSN) ; Nemati, A ; Salahi, E ; Sharif University of Technology
2013
Abstract
In the present study, bioceramic composites based hydroxyapatite (HAp) reinforced with carbon nanotubes (CNTs) was synthesized via sol-gel technique. The dried gels were individually heated at a rate of 5°C/min up to 600°C for 2 h in a muffle furnace in order to obtain HAp-MWCNTs mixed powder. Composites were characterized by XRD, FT-IR, SEM, TEM/SAED/EDX and Raman spectroscopy techniques. Results showed the synthesis of HAp particles in the MWCNTs sol which was prepared in advance, leads to an excellent dispersion of MWCNTs in HAp matrix. Apparent average size of crystallites increased by increasing the percentage of MWCNTs. The average crystallite size of samples (at 600°C), estimated by...
Effect of carbon nanotube incorporation in polyvinyl alcohol on structure and morphology of derived electrospun carbon nanofibers in presence of iodine and cadmium salt
, Article Materials Chemistry and Physics ; April , 2014 ; SSN: 02540584 ; Faghihi-Sani, M. A ; Shabani, K ; Baniasadi, A ; Sharif University of Technology
Abstract
This research focused on fabrication of various carbon nanofibers (CNFs) from electrospun Polyvinyl alcohol (PVA) by utilization of iodine (I2) and cadmium acetate dihydrate (Cd) as stabilizers. Moreover, the influence of carbon nanotube (CNT) incorporation on structure and morphology of CNFs was investigated. In this regard, PVA and PVA-Cd solutions were individually prepared and electrospun. The resulting nanofibers were treated in I2 vapor and then carbonized. In the case of CNT incorporation, oxidized CNTs were first scattered in PVA and PVA-Cd solutions and then electrospun, iodinated and carbonized in the same conditions as mentioned above. It was found that the I2, Cd and their...
Effect of equal channel angular pressing on aging treatment of Al-7075 alloy
, Article Progress in Natural Science: Materials International ; Volume 25, Issue 2 , April , 2015 , Pages 159-168 ; 10020071 (ISSN) ; Shaeri, M ; Salehi, M. T ; Seyyedein, S. H ; Abutalebi, M. R ; Sharif University of Technology
Elsevier
2015
Abstract
The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined. Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BC at both the room temperature and 120°C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120°C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using...
A TEM investigation on precipitation behavior of AEREX350 superalloy
, Article 11th International Symposium on Superalloys, Superalloys 2008, Champion, PA, 14 September 2008 through 18 September 2008 ; January , 2008 , Pages 549-552 ; Asgari, S ; Sharif University of Technology
2008
Abstract
The influence of solution treatment on precipitation behavior of AEREX™350 was investigated using hardness testing, TEM and SEM. Samples were solution treated at 1050°C and 1075°C for 1 hr and then aged at 700°C, 750°C and 800°C for 1,2,4,8 and 25 hrs. It was found that different solution treatment may be used for different applications of AEREX™350
Design and Fabrication of a 16-Way Ultra-Wideband Spatial Power Divider/Combiner
, M.Sc. Thesis Sharif University of Technology ; Banai, Ali (Supervisor)
Abstract
High power, broadband amplifiers at microwave and millimeter wave frequencies are needed for military and civilian applications. High power, broadband, high linearity, low noise, high efficiency and graceful degradation on failure are among the most important features in amplifier design. Solid state and vacuum tube devices have many disadvantages. A promising solution has been spatial power combining technique. Spatial power combining is a method of coherently combining the power of many amplifying devices using free space as the power dividing/combining medium within a guided wave structure in contrast to traditional circuit based amplifiers. This thesis presents the design and fabrication...
Producing ultrafine-grained aluminum rods by cyclic forward-backward extrusion: Study the microstructures and mechanical properties
, Article Materials Letters ; Volume 74 , May , 2012 , Pages 147-150 ; 0167577X (ISSN) ; Zaeem, M. A ; Dehghani, K ; Shivaee, H. A ; Sharif University of Technology
2012
Abstract
A cyclic forward-backward extrusion (CFBE) process was used as a severe plastic deformation (SPD) technique to produce ultrafine-grained aluminum rods. Yield strength and tensile strength of the specimens increased by increasing the number of CFBE cycles, while elongation to break decreased due to an increase in the grain refinement and microhardness. According to transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) results, the average grain size was reduced from 120 μm to 315 nm after only 3 cycles of CFBE
Low cycle fatigue mechanism of René 80 at high temperature-high strain
, Article Materials Science and Engineering A ; Volume 494, Issue 1-2 , 2008 , Pages 385-390 ; 09215093 (ISSN) ; Nategh, S ; Sharif University of Technology
2008
Abstract
The low cycle fatigue René 80, a Ni-base superalloy, was studied at temperature of 871 °C, R = (εmin/εmax) = 0 and strain rate of about 2 × 10-3 s-1. The dislocation structure and failure surface observations were evaluated through TEM and SEM. TEM studies showed that at Δεt = 0.8% during the first cycle the dislocations formed a hexagonal network in the γ-phase matrix. When the number of cycles increased, the density of dislocations increased as well. At N = Nf and Δεt = 0.8% the cutting of γ′ precipitates took place. SEM studies at Δεt = 0.8% and N = Nf showed that fatigue crack initiation generally occurred at the surface, where it is depleted of the γ′ phase as a result of oxidation by...
Investigation of thermal behavior of α-PbO and β-PbO IN O2 atmosphere
, Article Metalurgija ; Volume 57, Issue 4 , 2018 , Pages 287-290 ; 05435846 (ISSN) ; Nazari Alavi, A ; Mirzai, M ; Sharif University of Technology
Faculty of Metallurgy
2018
Abstract
The compounds α-lead oxide (α-PbO) and β-lead oxide (β-PbO) were purchased from Merck co. and used for thermal investigations in laboratory. The compound was heated in a thermogravimeter at different temperature, from 25 to 400 °C. The used gas atmosphere was O2. The received products were investigated by X-ray diffraction (XRD) technique. The received product Pb3O4 was confirmed by XRD. The textures of two different morphologies of α-PbO, β-PbO and the product Pb3O4 is investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. © 2018, Faculty of Metallurgy. All rights reserved
Oxido-peroxido W(VI)-histidine–MgAl-layered double hydroxide composite as an efficient catalyst in sulfide oxidation
, Article Applied Organometallic Chemistry ; Volume 32, Issue 6 , 2018 ; 02682605 (ISSN) ; Amini, M ; Morteza, S ; Farnia, F ; Bayrami, A ; Bagherzadeh, M ; Gautam, S ; Chae, K. H ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Oxido-peroxido W(VI)-histidine–MgAl-layered double hydroxide composite was prepared by using MgAl-layered double hydroxide as a host and oxido-peroxido W(VI)-histidine complex as a guest. The composite was characterized by XRD, IR, EDX,SEM and TEM techniques. This composite is tested for catalytic selective sulfoxidation reactions using hydrogen peroxide as oxidant showing good to moderate conversion along with high selectivity. Copyright © 2018 John Wiley & Sons, Ltd
Formation of Lanthanum hydroxide nanostructures: effect of NaOH and KOH solvents
, Article International Journal of Engineering, Transactions B: Applications ; Volume 21, Issue 2 , 2008 , Pages 169-176 ; 1728-144X (ISSN) ; Zanganeh, S ; Kajbafvala, A ; Shayegh, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
Materials and Energy Research Center
2008
Abstract
Lanthanum hydroxide (La(OH)3) nanostructures, including elliptical nanoparticles, octahedral rods and irregular nanoparticles were prepared chemically in NaOH and KOH solutions with 10 M concentration. The obtained powders were characterized with XRD, SEM, TEM and DTA. Crystallinities, morphologies and thermal behavior of the obtained nanostructure powders were investigated under the influence of above mentioned solvents. The effect of chemical's temperature was also determined in one of the solvents (i.e. NaOH). The formation of growth in nanostructure mechanism under the influence of alkali solutions (i.e., KOH and NaOH) have been discussed considerably in this paper
The effects of oxidation conditions on structural and electrical properties of silicon nanoparticles obtained by ultra-low-energy ion implantation
, Article Nanotechnology ; Volume 16, Issue 12 , 2005 , Pages 2987-2992 ; 09574484 (ISSN) ; Shalchian, M ; Ben Assayag, G ; Coffin, H ; Bonafos, C ; Schamm, S ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this paper, we have studied the effect of annealing under slightly oxidizing ambient (N2+O2) on the structural and electrical characteristics of a limited number of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultra-low-energy (1 keV) ion implantation and annealing. Specific experimental methods have been used to characterize the ncs populations. They include transmission electron microscopy (TEM) Fresnel imaging for evaluating the distances and widths of interest and spatially resolved electron energy loss spectroscopy (EELS) using the spectrum-imaging mode of a scanning transmission electron microscope (STEM) to measure the size...
Sonochemical synthesis and measurement of optical properties of zinc sulfide quantum dots
, Article Chemical Engineering Journal ; Volume 209 , 2012 , Pages 113-117 ; 13858947 (ISSN) ; Sajjadi, S. H ; Mehrkhah, R ; Nancarrow, P ; Sharif University of Technology
2012
Abstract
A facile sonochemical method has been developed to prepare very small zinc sulfide nanoparticles (ZnS NPs) of extremely small size about 1. nm in diameter using a set of ionic liquids based on the bis (trifluoromethylsulfonyl) imide anion and different cations of 1-alkyl-3-methyl-imidazolium. The structural features and optical properties of the NPs were determined in depth with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) analysis, and UV-vis absorption spectroscopy. The energy band gap measurements of ZnS NPs were calculated by UV-vis absorption...
Microstructure and phase transformation behavior of a stress-assisted heat-treated Ti-Rich NiTi shape memory alloy
, Article Journal of Materials Engineering and Performance ; Volume 21, Issue 8 , August , 2012 , Pages 1806-1812 ; 10599495 (ISSN) ; Rezaei, E ; Sharif University of Technology
Springer
2012
Abstract
In this study, the effects of stress-assisted heat treatment on the microstructure and phase transformation of a Ti-rich (Ti-49.52 at.% Ni) shape memory alloy were investigated. For this purpose, the alloy was heat treated at temperature of 500 °C for 10 h under applied stresses of 100 and 200 MPa. XRD, TEM, and repeated thermal cycling were employed to study the microstructure and transformation behavior of the heat-treated materials. Room temperature XRD diffractogram of the stress-free heat-treated material showed a weak reflection of austenite (B2), while that for the stress-assisted heat-treated materials had a high intensity implying the presence of residual austenite in the...
Interstitial sulfur photoluminescence in thermochemically synthesized CdS nanocrystals (NCs)
, Article EPJ Applied Physics ; Volume 56, Issue 1 , 2011 ; 12860042 (ISSN) ; Saievar Iranizad, E ; Marandi, M ; Taghavinia, N ; Sharif University of Technology
2011
Abstract
We have synthesized CdS NCs (NCs) by a thermochemical approach. CdSO 4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The structure and optical property of the NCs were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL). XRD and TEM analyses demonstrated hexagonal phase CdS NCs with an average size of around 2 nm. Synthesized NCs exhibited a band gap of about 3.21 eV and showed a broad band emission from 400 to 750 nm centered at 503 nm. This broad band emission is related to surface states of CdS and our results showed that the emission peak can be attributed to the interstitial sulfur. The...
Rheological and mechanical characteristics of low density polyethylene/ethylene-vinyl acetate/organoclay nanocomposites
, Article Polymer Engineering and Science ; Volume 50, Issue 7 , March , 2010 , Pages 1315-1325 ; 00323888 (ISSN) ; Shojaei, A ; Sheikh, N ; Sharif University of Technology
2010
Abstract
Attempts were made to trace the effect of organoclay (OC) on the rheological and mechanical behaviors of the low density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) blends. To do this effectively, in addition to LDPE/EVA/OC system, pure LDPE and LDPE/EVA blends were also examined as model systems. The rheological behavior was determined by the capillary rheometer. Morphological characterization was also carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and theoretical approach based on interfacial energies. Shear viscosity, tensile strength and elastic modulus of LDPE/EVA were found to decrease by increasing the EVA...
Analysis of Nonuniform Superconducting Transmission Lines and Microstrips in Microwave Regime
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor) ; Fardmanesh, Mehdi (Supervisor)
Abstract
Nonuniform superconducting microstrip transmission lines in microwave regime have been investigated. Nonuniform transmission lines provide the capability of controlling line parameters. Photonic structures with subwavelength features can be homogenized and thus be accurately approximated by homogeneous yet spatially dispersive structures. This idea is here applied to nonuniform superconducting transmission lines with subwavelength nonuniformities, i.e. subcentimeter features in the microwave regime. This modelling is quite useful in geometrical and optical control of quasi-TEM wave propagation and dispersion engineering along microwave superconducting lines. This approach has applications...
Modeling of Sub-wavelength Normal and Superconducting Nonuniform Transmission Lines in the Quasi-static Approximation
, M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mahdi (Supervisor) ; Mehrany, Khashayar (Supervisor)
Abstract
In this thesis, we have investigated nonuniform normal and superconducting microstrip transmission lines in microwave regime. Photonic structures with subwavelength features can be homogenized and thus be accurately approximated by homogeneous structures. This idea is here applied to nonuniform transmission lines with subwavelength nonuniformities, i.e. subcentimeter features in the microwave regime. We present an analytical model based on telegraphers’ equations in order to obtain line propagation characteristics; characteristic impedance, propagation constant, and group velocity. The accuracy of analysis in normal and superconducting lines is evaluated by measurement and electromagnetic...
On the effect of cooling rate during melt spinning of FINEMET ribbons
, Article Nanoscale ; Volume 5, Issue 16 , 2013 , Pages 7520-7527 ; 20403364 (ISSN) ; Hosseini, H. R. M ; Davami, P ; Ostadhossein, F ; Song, M ; Gjoka, M ; Sharif University of Technology
2013
Abstract
The effect of quenching wheel speed on the structure and Curie temperature of Fe73.5Si13.5B9Nb3Cu1 alloy has been investigated using X-ray diffraction, differential scanning calorimetry, transition electron microscopy and a SQUID magnetometer. Ribbons were melt-spun at different wheel speeds and then were annealed to nucleate nano crystals embedded in the amorphous matrix. The results indicated that the thickness of the ribbons was inversely proportional to the wheel speed following the power law of the type t ∝ Vs -1.231. DSC and XRD results showed that at higher wheel speeds the greater potential energy triggers the formation of Fe (Si) crystallites and thus, increases the crystallinity....
Study the effect of ultrasonic irradiation and surfactant/fe ions weight ratio on morphology and particle size of magnetite nanoparticles synthesised by co-precipitation for medical application
, Article World Academy of Science, Engineering and Technology ; Volume 64 , 2010 , Pages 457-460 ; 2010376X (ISSN) ; Pourafshary, P ; Madaah Hosseini, H. R ; Sharif University of Technology
2010
Abstract
A biocompatible ferrofluid have been prepared by coprecipitation of FeCl 2.4H 2O and FeCl 3.6H 2O under ultrasonic irradiation and with NaOH as alkaline agent. Cystein was also used as capping agent in the solution. Magnetic properties of the produced ferrofluid were then determined by VSM test and magnetite nanoparticles were characterized by XRD and TEM techniques. The effect of surfactant to Fe ion weight ratio was also studied during this project by using two different amount of Dextran. Results showed the presence of a biocompatible superparamagnetic ferrofluid including magnetite nanoparticles with particle size ranging under 20 nm. The increase in the surfactant content results in the...