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    A comprehensive study on the microstructure of high strength low alloy pipeline welds

    , Article Journal of Alloys and Compounds ; Vol. 597 , June , 2014 , pp. 142-147 ; ISSN: 09258388 Beidokhti, B ; Kokabi, A. H ; Dolati, A ; Sharif University of Technology
    Abstract
    The microstructural characteristic of HSLA welds containing different amounts of titanium were evaluated carefully. It was observed that the microstructure of welds consisted of ferrite with mixed morphologies, and small amounts of pearlite and martensite-austenite micro-constituents. Because of insufficient time for diffusion of carbon, formation of pearlite lamellae could not be completed in the weld region. Martensite was formed from carbon enrichment of austenite during nucleation and growth of acicular ferrite and bainitic ferrite. While coarse manganese sulfide particles had weak interface strength with matrix and formed some micro-fissures; increasing titanium amount of welds... 

    Towards defining new nano-descriptors: Extracting morphological features from transmission electron microscopy images

    , Article RSC Advances ; Vol. 4, issue. 104 , Nov , 2014 , p. 60135-60143 Bigdeli, A ; Hormozi-Nezhad, M. R ; Jalali-Heravi, M ; Abedini, M. R ; Sharif-Bakhtiar, F ; Sharif University of Technology
    Abstract
    Due to the important role of surface-related properties of NPs in their biological behavior, simple and fast methods that could precisely demonstrate accurate information about NPs' surface, structure and morphology are highly desirable. In this study a set of surface morphological nano-descriptors (size, shape, surface area, agglomeration state, curvature, corner count and aspect ratio) have been defined and extracted from Transmission Electron Microscopy (TEM) images of nanoparticles (NPs) by Digital Image Processing methods. The extracted data represent a thorough description of the surface and morphologies of NPs lying beyond their TEM images and can supply the data required for a... 

    Growth kinetics of Al-Fe intermetallic compounds during annealing treatment of friction stir lap welds

    , Article Materials Characterization ; Vol. 90 , April , 2014 , pp. 121-126 ; ISSN: 10445803 Movahedi, M ; Kokabi, A. H ; Seyed Reihani, S. M ; Najafi, H ; Farzadfar, S. A ; Cheng, W. J ; Wang, C. J ; Sharif University of Technology
    Abstract
    In this study, we explored the growth kinetics of the Al-Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 C for 30 to 180 min. Optical microscope (OM), field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) were employed to investigate the structure of the weld zone. The thickness and composition of the IM layers were evaluated using image analysis system and electron back-scatter diffraction (EBSD), respectively. Moreover, kernel average misorientation (KAM) analysis was performed to evaluate the level of stored energy in the as-welded state.... 

    Influence of double aging on microstructure and yield strength of AEREX ™ 350

    , Article Materials Science and Engineering A ; Volume 534 , 2012 , Pages 547-551 ; 09215093 (ISSN) Kermajani, M ; Sharif University of Technology
    Abstract
    Age hardening behavior of selected samples of AEREX ™ 350, a nickel-cobalt based superalloy, was investigated in this article. The relationship between the microstructure and mechanical properties was elucidated using hardness and compression testing methods and optical, scanning and transmission electron microscopy techniques. It was found that the microstructure is sensitive to the temperature of the solution and the aging treatments. This approach may be used to optimize the microstructure of the alloy for different applications  

    Supercritical synthesis and characterization of graphene-pbs quantum dots composite with enhanced photovoltaic properties

    , Article Industrial and Engineering Chemistry Research ; Volume 54, Issue 30 , 2015 , Pages 7382-7392 ; 08885885 (ISSN) Tayyebi, A ; Tavakoli, M. M ; Outokesh, M ; Shafiekhani, A ; Simchi, A ; Sharif University of Technology
    American Chemical Society  2015
    Abstract
    Lead sulfide quantum dots (PbS QDs) were decorated onto a graphene surface in a semi-core-shell structure using supercritical ethanol. The temperature of ethanol played significant role in controlling size and agglomeration of QDs as well as the extent of reduction of graphene. Average size of the QDs was estimated by transmission electron microscopy to be around 3.96 nm and by quantum models to be about 4.34 nm. PbS QDs prepared at 330 °C were of high purity, and the yield was 99%. Instrumental and chemical analyses demonstrated formation of a strong bond between PbS QDs and graphene, through a Pb-O-C bridge. UV and photoluminescence measurements along with theoretical considerations... 

    Synthesis of zero-valent iron nanoparticles via electrical wire explosion for efficient removal of heavy metals

    , Article Clean - Soil, Air, Water ; Volume 45, Issue 3 , 2017 ; 18630650 (ISSN) Seyedi, S. M ; Rabiee, H ; Seyed Shahabadi, S. M ; Borghei, S. M ; Sharif University of Technology
    Abstract
    In this paper, electrical wire explosion (EWE) was used as a simple, clean, in situ method to synthesise nano zero-valent iron (nZVI) particles in liquid mediums. The structural and physical properties of the synthesised nZVI particles were characterised by x-ray diffraction, Brunauer–Emmett–Teller analysis, field emission scanning electron microscopy and transmission electron microscopy. The synthesised spherical nanoparticles, at a specific size of 10–50 nm, possessed large surface areas of approximately 13.27 m2/g, reinforcing the significant advantages of EWE, that is, less aggregation and in situ production of nanoparticles with enhanced removal efficacy, for groundwater treatment.... 

    Influence of solution treatment on precipitation behavior of a Ni-Co alloy

    , Article Scripta Materialia ; Volume 57, Issue 2 , 2007 , Pages 93-96 ; 13596462 (ISSN) Samiee, M ; Asgari, S ; Sharif University of Technology
    2007
    Abstract
    The age-hardening behavior and microstructure of selected samples of a Ni-Co alloy were studied using hardness testing, optical microscopy, and scanning and transmission electron microscopy. The final microstructure of the material was found to be sensitive to the temperature of the solution treatment. This approach may be used to optimize the microstructure of the alloy for different applications. © 2007 Acta Materialia Inc  

    Preparation and characterization of ZnO nanoparticles by a novel sol-gel route

    , Article Materials Letters ; Volume 61, Issue 14-15 , 2007 , Pages 3265-3268 ; 0167577X (ISSN) Vafaee, M ; Sasani Ghamsari, M ; Sharif University of Technology
    2007
    Abstract
    In this study, ZnO nanoparticles with 3 to 4 nm size and spherical shape have been prepared. For the first time, TEA (triethanolamine) as a surfactant has been used for the preparation of ZnO nanoparticles. The best concentration of each component was adjusted through comparison between different sol absorption spectra. The best sol regarding its optical property was subjected to analysis by photoluminescence spectroscopy. TEM micrograph and electron diffraction pattern of these particles were obtained to represent the morphology and crystalline phase of the particles, respectively. Experimental results have shown that the prepared zinc oxide nanoparticles by this method have higher... 

    GMR in multilayered nanowires electrodeposited in track-etched polyester and polycarbonate membranes

    , Article Journal of Magnetism and Magnetic Materials ; Volume 308, Issue 1 , 2007 , Pages 35-39 ; 03048853 (ISSN) Nasirpouri, F ; Southern, P ; Ghorbani, M ; Iraji zad, A ; Schwarzacher, W ; Sharif University of Technology
    2007
    Abstract
    Commercially available track-etched polyester membranes were used as templates to electrodeposit Co-Ni-Cu/Cu multilayered nanowires, giving room-temperature current perpendicular to plane (CPP) giant magnetoresistance (GMR) values of up to ∼12%. In contrast to similar nanowires electrodeposited in track-etched polycarbonate membranes, the GMR obtained in multilayered nanowires electrodeposited in the polyester membranes increased with decreasing Cu-layer thickness tCu, for tCu in the 2-7 nm range, indicating a lack of ferromagnetic coupling through pinholes, etc. Transmission electron micrographs showed clear evidence for smooth, parallel layer interfaces in the nanowires. © 2006 Elsevier... 

    Age-hardening behavior and phase identification in solution-treated AEREX 350 superalloy

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 37, Issue 7 , 2006 , Pages 2051-2057 ; 10735623 (ISSN) Asgari, S ; Sharif University of Technology
    2006
    Abstract
    This article presents results of an investigation on age-hardening behavior of superalloy AEREX 350. Microhardness testing was employed to evaluate the age-hardening response of the alloy while optical, scanning, and transmission electron microscopy techniques were used to characterize the major phases formed during the aging process. No significant hardening was found in solution-treated samples aged at temperatures up to about 680 °C. Aging at 700 °C up to 950 °C, however, caused a characteristic hardening response. This hardening was concurrent with the formation of γ', an ordered phase with L12 structure, as fine precipitate distributed throughout the fcc matrix. In the temperature range... 

    Strain hardening mechanisms in aged AEREX350 superalloy

    , Article Materials Science and Engineering A ; Volume 398, Issue 1-2 , 2005 , Pages 204-208 ; 09215093 (ISSN) Najafi, H ; Asgari, S ; Sharif University of Technology
    2005
    Abstract
    In this paper, results of an investigation on strain hardening mechanisms of aged AEREX350 alloy during room temperature compression testing are reported. TEM studies were conducted on commercial samples aged at 850 °C both before and after deformation in a strain range of 0.15-0.27. It was found that only coherent γ′ precipitates with L12 structure formed in these samples prior to deformation. TEM studies also showed twin intersections in the deformed samples. Based on these observations, it is suggested that the high strain hardening rate of the aged material in this strain range is mainly related to the formation of intersecting deformation twins. This is attributed to the decrease in the... 

    Evolution of quantum electronic features with the size of silicon nanoparticles embedded in a SiO2 layer obtained by low energy ion implantation

    , Article 11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technlogy, GADEST 2005, Giens, 25 September 2005 through 30 September 2005 ; Volume 108-109 , 2005 , Pages 71-76 ; 10120394 (ISSN); 3908451132 (ISBN); 9783908451136 (ISBN) Grisolia, J ; Shalchian, M ; BenAssayag, G ; Coffin, H ; Bonafos, C ; Dumas, C ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
    Trans Tech Publications Ltd  2005
    Abstract
    In this paper, we have studied the evolution of quantum electronic features with the size of silicon nanoparticles embedded in an ultra-thin SiO 2 layer. These nanoparticles were synthesized by ultralow energy (1 KeV) ion implantation and annealing. Their size was modified using the effect of annealing under slightly oxidizing ambient (N2+O2). Material characterization techniques including transmission electron microscopy (TEM) Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on few (less than two... 

    Investigation of rheological behavior of polyamide 6/acrylonitrile-butadiene-styrene/nanoclay in transient shear flow

    , Article Journal of Thermoplastic Composite Materials ; Volume 28, Issue 8 , 2015 , Pages 1217-1232 ; 08927057 (ISSN) Mojarrad, A ; Ramazani Sa, A ; Ghasemi, I ; Vaziri, A ; Sharif University of Technology
    SAGE Publications Ltd  2015
    Abstract
    Linear and nonlinear (in both steady and transient shear flows) rheological properties of polyamide 6/acrylonitrile-butadiene-styrene (PA6/ABS) nanocomposite blends have been investigated. Characterization of nanocomposite samples morphology by scanning electron microscopy revealed that with increasing nanoclay loading, size of dispersing phase droplets decreases significantly and their uniformity improved considerably. Transmission electron microscopy observations clearly display a coexistence of intercalate and exfoliate structure for nanoclay in the polymer-blend nanocomposite. On the other hand, we see that the tactoids are collected of a few silicate layers and possibly also of a single... 

    Adsorptive removal of petroleum hydrocarbons from aqueous solutions by novel zinc oxide nanoparticles grafted with polymers

    , Article Petroleum Science and Technology ; Volume 34, Issue 8 , 2016 , Pages 778-784 ; 10916466 (ISSN) Salehi, B ; Hasani, A. H ; Ahmad Panahi, H ; Borghei, S. M ; Sharif University of Technology
    Taylor and Francis Inc 
    Abstract
    Zinc oxide nanoparticles were synthesized and modified by a three-stage method. Elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy, and Brunauer–Emmett–Teller method were applied to characterize the nanoparticles. These nanoparticles were evaluated for toluene adsorption from aqueous solutions as a representative of petroleum hydrocarbon removal. The optimum adsorption condition achieved at pH of 6 and contact time of 30 min. The adsorption isotherms were fitted to the Langmuir model. The measured adsorption capacity was 12.8 mg g−1. This study demonstrated that these nanoparticles could be used as an... 

    Polyurethane/clay nanocomposites reinforced with carbon and glass fibres: study of mechanical and thermal properties, and the effect of electron beam irradiation

    , Article Plastics, Rubber and Composites ; Volume 46, Issue 9 , 2017 , Pages 413-420 ; 14658011 (ISSN) Kosari, M ; Mousavian, S. M. A ; Razavi, S. M ; Ahmadi, S. J ; Izadipanah, M ; Sharif University of Technology
    Abstract
    Polyurethane (PU) nanocomposites with 0, 1, 3, 5, and 7 wt-% nanoclay contents were prepared. X-ray diffraction patterns, transmission electron microscopy images, tensile test, and thermogravimetric analysis were utilised to reveal the morphological, mechanical, and thermal-resistant properties of the prepared nanocomposites. The exfoliated structure was obtained for nanoclay contents up to 3 wt-%. Incorporation of nanoclay to the PU matrix prompted the thermal stability of the polymer. A nanocomposite filled with 3 wt-% nanoclay showed the best tensile strength in the prepared nanocomposites. Subsequently, the nanocomposite with the 3 wt-% nanoclay was reinforced with carbon and glass... 

    Effect of dwell time on joint interface microstructure and strength of dissimilar friction stir spot-welded al-5083 and st-12 alloy sheets

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 48, Issue 4 , 2017 , Pages 1744-1758 ; 10735623 (ISSN) Fereiduni, E ; Movahedi, M ; Kokabi, A. H ; Najafi, H ; Sharif University of Technology
    Springer Boston  2017
    Abstract
    Joining of Al-5083 alloy sheet to St-12 steel sheet was performed using a new friction stir spot welding (FSSW) technique in which the tool pin tip did not enter lower steel sheet. Effect of dwell time on the microstructure and mechanical properties of the joints was studied by various methods including microhardness measurements, shear test, stereo and light microscopy as well as scanning and transmission electron microscopy (SEM and TEM). Results indicated that compared to the conventional FSSW process, stronger joints can be achieved by this FSSW technique. Cross-sectional observation of the failed specimens indicated the occurrence of final fracture from the circumference of the tool pin... 

    Study of molecular conformation and activity-related properties of lipase immobilized onto core-shell structured polyacrylic acid-coated magnetic silica nanocomposite particles

    , Article Langmuir ; Volume 32, Issue 13 , 2016 , Pages 3242-3252 ; 07437463 (ISSN) Esmaeilnejad Ahranjani, P ; Kazemeini, M ; Singh, G ; Arpanaei, A ; Sharif University of Technology
    American Chemical Society 
    Abstract
    A facile approach for the preparation of core-shell structured poly(acrylic acid) (PAA)-coated Fe3O4 cluster@SiO2 nanocomposite particles as the support materials for the lipase immobilization is reported. Low- or high-molecular-weight (1800 and 100 000, respectively) PAA molecules were covalently attached onto the surface of amine-functionalized magnetic silica nanoacomposite particles. The successful preparation of particles were verified by scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), zeta potential measurement, and Fourier-transform infrared (FTIR) techniques. Once lipase is covalently... 

    Influence of nanoclay on morphology, mechanical properties and deformation mechanism of Polystyrene

    , Article Polymer - Plastics Technology and Engineering ; Vol. 53, issue. 2 , 2014 , p. 156-161 ; ISSN: 03602559 Akbari, B ; Bagheri, R ; Sharif University of Technology
    Abstract
    Polystyrene/organoclay nanocomposites were prepared by melt intercalation method in this research. Morphology, tensile and impact properties and deformation mechanism of the samples were studied. To study the structure of nanocomposites, X-ray diffraction and transmission electron microscopy techniques are utilized. The deformation mechanisms of different samples were examined via reflected and transmitted optical microscopy. The results reveal that incorporation of organoclay affects structure, mechanical properties and deformation mechanism of nanocomposite. Introduction of organoclay can facilitate initiation and growth of crazing mechanism in polystyrene at both conditions of loadings,... 

    Polarity adjustment of a nanosilica-functionalized polyamine modified by ionic liquid for removal of Cu2+ from aqueous solutions

    , Article RSC Advances ; Volume 6, Issue 17 , 2016 , Pages 14128-14133 ; 20462069 (ISSN) Vafaeezadeh, M ; Mahmoodi Hashemi, M ; Ghavidel, N ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Abstract
    The current work deals with modification of the surface of a silica-polyamine with amine-based ionic liquid (IL) and its application for removal of Cu2+ from an aqueous media. The absorbent is simply prepared from commercially available reagents. The material is characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), N2 adsorption-desorption, and transmission electronic microscopy (TEM). Effects of several parameters on absorption efficiency, as well as activity of the absorbent to other metals, are also investigated. Moreover, the reusability of the absorbent is studied at the optimized condition. © The Royal Society of Chemistry 2016  

    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) Sajadi, S. A. A ; 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