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    , M.Sc. Thesis Sharif University of Technology Zamzamian, Mehrdad (Author) ; Vosoughi, Nasser (Supervisor)
    High purity Germanium (HPGe) detector is a sub branch of semiconductor detectors which has very good resolution, very little dead time, able tobuild in large dimensions and suitable for any condition that it is using in vast fields from space investigation to radiation therapy. this detector is usually used to detecting gamma radiations furthermore the best resolution can be attained with decreasing leakage current. for analyzing about operation of the HPGe detector, it needs to initiate a model of this detector. in this studing has been used modelGEM-15190,POP-TOP which is built by ortec company. for initiating, it was used liquid nitrogen and accessory equipments like high voltage supply,... 

    Influence of martensite volume fraction on impact properties of triple phase (TP) steels

    , Article Journal of Materials Engineering and Performance ; Volume 22, Issue 3 , 2013 , Pages 823-829 ; 10599495 (ISSN) Zare, A ; Ekrami, A ; Sharif University of Technology
    Ferrite-bainite-martensite triple phase (TP) microstructures with different volume fractions of martensite were obtained by changing heat treatment time during austempering at 300 C. Room temperature impact properties of TP steels with different martensite volume fractions (VM) were determined by means of Charpy impact testing. The effects of test temperature on impact properties were also investigated for two selected microstructures containing 0 (the DP steel) and 8.5 vol.% martensite. Test results showed reduction in toughness with increasing VM in TP steels. Fracture toughness values for the DP and TP steels with 8.5 vol.% martensite were obtained from correlation between fracture... 

    Near-room-temperature spin caloritronics in a magnetized and defective zigzag MoS2 nanoribbon

    , Article Journal of Computational Electronics ; Volume 19, Issue 1 , 2020 , Pages 137-146 Zakerian, F ; Fathipour, M ; Faez, R ; Darvish, G ; Sharif University of Technology
    Springer  2020
    Using a tight-binding approach and first-principles calculations combined with the nonequilibrium Green’s function method, the thermal spin transport in a zigzag molybdenum disulfide (MoS 2) nanoribbon in the proximity of a ferromagnetic insulator that induces a local exchange magnetic field in the center of the nanoribbon is investigated. It is found that a pure spin current and perfect spin Seebeck effect with zero charge current can be generated by applying a thermal gradient and local exchange magnetic field without a bias voltage near room temperature. Furthermore, it is shown that this nanoscale device can act as a spin Seebeck diode for the control of thermal and spin information in... 

    Dynamic ageing and the mechanical response of Al-Mg-Si alloy through equal channel angular pressing

    , Article Materials and Design ; Volume 31, Issue 9 , October , 2010 , Pages 4076-4082 ; 02641275 (ISSN) Vaseghi, M ; Karimi Taheri, A ; Ig Hong, S ; Seop Kim, H ; Sharif University of Technology
    In this paper, dynamic ageing characteristics associated with the application of equal channel angular pressing (ECAP) to Al6061 alloy at elevated temperatures was investigated. Followed by ECAP, Vickers microhardness measurement on the cross-sectional planes and microstructural observations were undertaken using transmission electron microscopy. The combination of the ECAP process with dynamic ageing at both 100°C and 150°C resulted in a significant increase in hardness. The grain size was measured as ∼160. nm after four passes. A comparison with the published data on the same alloy processed by ECAP at room temperature and statically aged, suggests several advantages in incorporating... 

    Adiabatic shear banding in an Al-Mg-Si alloy processed by equal channel angular pressing

    , Article Materials Science Forum, 2 August 2010 through 6 August 2010, Cairns, QLD ; Volume 654-656 , 2010 , Pages 1014-1017 ; 02555476 (ISSN) ; 0878492550 (ISBN) Vaseghi, M ; Taheri, A. K ; Yoo, J. H ; Joo, S. H ; Kim, H. S ; Sharif University of Technology
    Equal channel angular pressing is an outstanding method for imposing large plastic deformation to metallic materials without any decreasing in cross section area of as processed samples. In this paper, the effect of working temperature, ram speed and the number of passes on the formation of adiabatic shear bands in Al6061 during equal channel angular pressing was investigated. Billets of the alloy were processed up to four passes via route BC from room temperature to 200°C with two ram speeds using a die that imparts an effective strain of ∼1.1 per pass. The results have demonstrated that the onset of the adiabatic shear banding in this alloy strongly depends on the ram speed: more... 

    Structural, magnetic, and optical properties of zinc-and copper-substituted nickel ferrite nanocrystals

    , Article Journal of Superconductivity and Novel Magnetism ; Volume 25, Issue 7 , 2012 , Pages 2443-2455 ; 15571939 (ISSN) Tehrani, F. S ; Daadmehr, V ; Rezakhani, A. T ; Akbarnejad, R. H ; Gholipour, S ; Sharif University of Technology
    Springer  2012
    Ferrite nanocrystals are an interesting material due to their rich physical properties. Here we add nonmagnetic dopants Zn and Cu to nickel ferrite nanocrystals, Ni1-xMxFe2O4 (0 ≤ x ≤ 1, M = Cu, Zn), and study how relevant properties of the samples are modified accordingly. Basically, these dopings cause a rearrangement of Fe +3 ions into the two preexisting octahedral and tetrahedral sites. In fact, this, we show, induces pertinent magnetic properties of the doped samples. In the case of the Cu-doping, the Jahn-Teller effect also emerges, which we identify through the Fourier Transform Infra-Red Spectroscopy of the samples. Moreover, we show an increase in the lattice parameters of the... 

    Ionic liquid/graphene oxide as a nanocomposite for improving the direct electrochemistry and electrocatalytic activity of glucose oxidase

    , Article Journal of Solid State Electrochemistry ; Volume 17, Issue 1 , January , 2013 , Pages 183-189 ; 14328488 (ISSN) Tasviri, M ; Ghasemi, S ; Ghourchian, H ; Gholami, M. R ; Sharif University of Technology
    By combination of 1-ethyl-3-methyl immidazolium ethyl sulfate as a typical room temperature ionic liquid (IL) and graphene oxide (GO) nanosheets, a nanocomposite was introduced for improving the direct electrochemistry and electrocatalytic activity of glucose oxidase (GOx). The enzyme on the IL-GO-modified glassy carbon electrode exhibited a quasireversible cyclic voltammogram corresponding to the flavine adenine dinucleotide/FADH2 redox prosthetic group of GOx. At the scan rate of 100 mV s-1, the enzyme showed a peak-to-peak potential separation of 82 mV and the formal potential of -463 mV (vs Ag/AgCl in 0.1 M phosphate buffer solution, pH 7.0). The kinetic parameters of the charge transfer... 

    Facile synthesis of monodisperse thermally immiscible Ag-Ni alloy nanoparticles at room temperature

    , Article Bulletin of Materials Science ; Vol. 37, issue. 6 , 2014 , pp. 1447-1452 Tabatabaei, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag-Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag-Ni ANPs was achieved. Stoichiometry of the Ag-Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand... 

    Efficient synthesis of novel 3-substituted coumarin-3-carboxamide

    , Article Journal of the Korean Chemical Society ; Vol. 58, Issue. 2 , 20 April , 2014 , pp. 186-192 ; ISSN: 2234-8530 (Online) Sheikhhosseini, E ; Balalaie, S ; Bigdeli, M. A ; Habibi, A ; Moghaddam, H. P ; Sharif University of Technology
    A series of novel pseudopeptides contained coumarin skeleton were synthesized through the Ugi-four-component reaction. The 3-substituted coumarin-3-carboxamides were formed through reaction of benzaldehyde derivatives, anilines, coumarin-3- carboxylic acid and isocyanides with high yields and high bond-forming efficiency at room temperature. These novel amidated coumarins exhibit brilliant fluorescence in range of 535-547 nm in chloroform  

    Room-temperature quantum effect in silicon nanoparticles obtained by low-energy ion implantation and embedded in a nanometer scale capacitor

    , Article Applied Physics Letters ; Volume 86, Issue 16 , 2005 , Pages 1-3 ; 00036951 (ISSN) Shalchian, M ; Grisolia, J ; Assayag, G. B ; Coffin, H ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
    In this article, we present the room-temperature current-voltage characteristics of a nanometer scale (100×100 nm2) metal-oxide-semiconductor capacitor containing few (less than 100) silicon nanoparticles. The layer of silicon nanoparticles is synthesized within the oxide of this capacitor by ultra low-energy ion implantation and annealing. Current fluctuations in the form of discrete current steps and sharp peaks appeared in the static and dynamic I (V) characteristics of the capacitor. These features have been associated to quantized charging and discharging of the nanoparticles and the resulting Coulomb interaction to the tunneling current. © 2005 American Institute of Physics  

    The effect of dynamic strain aging on room temperature mechanical properties of high martensite dual phase (HMDP) steel

    , Article Materials Science and Engineering A ; Volume 550 , 2012 , Pages 325-332 ; 09215093 (ISSN) Shahriary, M. S ; Koohbor, B ; Ahadi, K ; Ekrami, A ; Khakian Qomi, M ; Izadyar, T ; Sharif University of Technology
    Elsevier  2012
    AISI 4340 steel bars were heated at 900 °C for one hour, annealed at 738 °C for different durations and oil-quenched in order to obtain dual phase steels with different ferrite volume fractions. A 3% prestrain at the temperature range of 150-450 °C was then imposed to the samples, and room temperature tensile tests were carried out, afterwards. Results indicate that the maximum values for both yield and ultimate tensile strength would exist for the samples pre-strained at the temperature range of 250-300 °C. Also, a sudden drop of the ductility was observed at the mentioned temperature range. The observed behavior might be attributed to the occurrence of dynamic strain aging taken place at... 

    Room temperature synthesis of highly crystalline TiO2 nanoparticles

    , Article Materials Letters ; Volume 92 , February , 2013 , Pages 287-290 ; 0167577X (ISSN) Sasani Ghamsari, M ; Radiman, S ; Azmi Abdul Hamid, M ; Mahshid, S ; Rahmani, S ; Sharif University of Technology
    Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the... 

    High temperature NiTiHf shape memory thin films fabricated by simultaneous sputter deposition from elemental targets

    , Article International Conference on Shape Memory and Superelastic Technologies, SMST-2006, Pacific Grove, CA, 7 May 2006 through 11 May 2006 ; 2008 , Pages 315-322 ; 9780871708625 (ISBN) Sanjabi, S ; Sadrnezhaad, .Kh ; Barber, Z. H ; Sharif University of Technology
    NiTiHf thin films with varying hafnium contents up to 28.7at% were fabricated using simultaneous sputter deposition from separate Ni, Ti, and Hf targets onto unheated substrates. The required film composition was achieved by adjusting the power ratio to the targets. The as-deposited films were amorphous; and post deposition annealing was performed at 550°C, slightly above their crystallization temperatures. The crystallization temperature of the films varied as a function of Hf concentration, and was as high as 520°C at a Hf content of 28.7at%. 2μm thick crystallized films with I0at% or greater Hf were martensitic at room temperature. DSC analysis demonstrated that above 10at%Hf additions... 

    Stereoselective synthesis ofβ-Amino ketones via direct mannich-type reaction catalyzed with SO 2- 4/TiO 2 and SO 2- 4/nano TiO 2

    , Article Synthetic Communications ; Volume 39, Issue 24 , 2009 , Pages 4441-4453 ; 00397911 (ISSN) Samet, M ; Eftekhari Sis, B ; Mahmodi Hashemi, M ; Farmad, F ; Sharif University of Technology
    At room temperature, SO 2- 4/nano-TiO 2 efficiently catalyze the direct Mannich-type reaction of varieties of in situ-generated aldimines using aldehydes and anilines with ketones in a three-component reaction under solvent-free conditions. The reaction proceeds rapidly and affords the correspondingβ-amino ketones in good to high yields with good to excellent stereoselectivity. The catalyst can be recycled for subsequent reactions without any appreciable loss of efficiency  

    Catalyst-Free and Green Synthesis of Some Novel Benzamide Derivatives

    , Article Journal of Heterocyclic Chemistry ; Volume 52, Issue 6 , November , 2015 , Pages 1848-1857 ; 0022152X (ISSN) Samani Ghaleh Taki, B ; Rostami, M ; Mirkhani, V ; Moghadam, M ; Mohammadpoor Baltork, I ; Tangestaninejad, S ; Jamali Moghadam, A ; Kia, R ; Sharif University of Technology
    HeteroCorporation  2015
    In the present work, a simple, green, rapid, and catalyst-free procedure for the synthesis of benzamide derivatives by ring opening of azlactones with diamines such as ethylene diamine and 1,3-propylenediamine is described. The present method offers several advantages such as short reaction times, easy work-up, and mild reaction conditions in the absence of catalyst and any toxic solvent and material. In addition, the structure obtained by X-ray crystallography was compared with the theoretical results obtained by density functional theory using the B3LYP functional and cc-pVDZ basis sets  

    Water repellent room temperature vulcanized silicone for enhancing the long-term stability of perovskite solar cells

    , Article Solar Energy ; Volume 218 , 2021 , Pages 28-34 ; 0038092X (ISSN) Samadpour, M ; Heydari, M ; Mohammadi, M ; Parand, P ; Taghavinia, N ; Sharif University of Technology
    Elsevier Ltd  2021
    A key direction toward enhancing the long term and outdoor stability of the perovskite solar cells is encapsulation. As a result, a suitable encapsulation package is required to prevent moisture and oxygen penetration toward the perovskite solar cells. In this work, a low-cost commercially available bilayer structure of poly (methyl methacrylate)/ room-temperature vulcanizing silicone rubber (RTV) encapsulation package for enhancing the long term stability of the perovskite solar cells has been investigated. Encapsulated cells retained more than 80% of the initial efficiency at the environmental condition of 50% moisture, and room temperature after 1000 h, however reference cell efficiency... 

    Automated trace determination of earthy-musty odorous compounds in water samples by on-line purge-and-trap-gas chromatography-mass spectrometry

    , Article Journal of Chromatography A ; Volume 1136, Issue 2 , 2006 , Pages 170-175 ; 00219673 (ISSN) Salemi, A ; Lacorte, S ; Bagheri, H ; Barceló, D ; Sharif University of Technology
    An automated technique based on purge-and-trap coupled to gas chromatography with mass spectrometric detection has been developed and optimized for the trace determination of five of the most important water odorants; 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2,4,6-trichloroanisole and geosmin. The extraction method was absolutely solvent-free. Analytes were purged from 20 ml of water sample containing sodium chloride at room temperature by a flow of He and trapped on a Tenax sorbent. The desorption step was performed with helium and temperature programming and desorbed analytes were directly transferred to a gas chromatograph coupled to a mass... 

    Microstructure-toughness relationship in AISI4340 steel

    , Article Defect and Diffusion Forum ; Volume 312-315 , 2011 , Pages 110-115 ; 10120386 (ISSN) ; 9783037851173 (ISBN) Saeidi, N ; Ekrami, A ; Sharif University of Technology
    To improve the strength and toughness of AISI 4340 steel, different microstructures, containing full bainite, bainite-ferrite, martensite-ferrite and full martensite were produced by different heat treatment cycles. Tensile, impact and hardness tests were carried out at room temperature. The ductile-brittle transition temperature was determined from impact data at different temperatures. The results showed that steel with bainite - 0.34 ferrite microstructure has the highest elongation and charpy impact energy, while its tensile strength and yield stress decreased in comparison to other microstructures. This increment was noticeable when bainite - 0.34 ferrite steel was tempered. The... 

    Comparison of mechanical properties of martensite/ferrite and bainite/ferrite dual phase 4340 steels

    , Article Materials Science and Engineering A ; Volume 523, Issue 1-2 , 2009 , Pages 125-129 ; 09215093 (ISSN) Saeidi, N ; Ekrami, A ; Sharif University of Technology
    Different microstructures were produced by heat treatment of 4340 steel. These microstructures are bainite, martensite, ferrite-martensite and ferrite-bainite. Mechanical tests were carried out at room temperature. The results showed that steel with bainite-ferrite microstructure has better ductility and charpy impact energy than steels with martensite-ferrite and full bainite microstructures. But yield and tensile strengths of this steel are less than the yield and tensile strengths of the other two steels. Hardness measurements showed that their hardness is the same. Fracture surface observations of tensile specimens showed increase in toughness of bainite-ferrite in comparison to... 

    Effect of microstructure on rolling behavior of NiTi memory alloy

    , Article Materials and Manufacturing Processes ; Volume 23, Issue 7 , 26 August , 2008 , Pages 646-650 ; 10426914 (ISSN) Sadrnezhaad, S. K ; Badakhshan Raz, S ; Sharif University of Technology
    NiTi shape memory alloy (SMA) ingots were produced by vacuum induction melting/casting unit. The effect of microstructure on the hot (1000C) and cold (room temperature) rolling workability of cast samples was investigated. Microstructure of the cast samples was related to the type of crucible which used for melting and the average vacuum pressure of VIM furnace. Optical microscope, scanning electron microscope (SEM), and energy dispersive technology (EDS) methods were used to inspect the origins of observed cracks after rolling processes. The results showed that the formation of both Ti4Ni2O and TiC impurities formed due to inappropriate melting conditions had detrimental effects on...