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    Synthesis of pyrochlore free PMN-PZT ceramics via a seeding method

    , Article Sensors and Actuators, A: Physical ; Volume 141, Issue 2 , 2008 , Pages 463-470 ; 09244247 (ISSN) Moetakef, P ; Ali Nemati, Z ; Sharif University of Technology
    2008
    Abstract
    Pyrochlore free (x)PMN-(1 - x)PZT ceramics were synthesized successfully by a seeding method. In this method, the mixture of PbO, MgO and Nb2O5 was added to the prepared PZT sol to from PMN-PZT gel. The gel was fired to vaporize the organic contents of gel and obtain powder. Two-step sintering process was used to produce pyrochlore free ceramics. The samples produced by this method showed higher relative densities, lower sintering temperature and higher dielectric properties relative to the mixed oxide method, mostly due to the higher homogeneity of the prepared powder. The measured dielectric properties of PZT-rich and PMN-rich materials were high while the other samples exhibited low... 

    An investigation of the densification and microstructural evolution of M2/316L stepwise graded composite during co-sintering

    , Article Journal of Materials Science ; Volume 43, Issue 1 , 2008 , Pages 55-63 ; 00222461 (ISSN) Firouzdor, V ; Simchi, A ; Kokabi, A. H ; Sharif University of Technology
    2008
    Abstract
    The densification and microstructural evolution during co-sintering of M2 tool steel/316L stainless steel composite layers with and without boron addition was studied. A pressureless sintering method in conjunction with a powder layering technique was used to fabricate the stepwise graded composite layers. Isothermal and non-isothermal sintering response of the individual and composite layers was examined and the microstructural features of the bonding zone were studied. Shear strength and microhardness of the bonding zone were also measured. It was shown that an enhanced densification is obtained in the composite layers due to (i) sintering shrinkage incompatibility between two steels, (ii)... 

    Thermal effects on quantum communication through spin chains

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 71, Issue 4 , 2005 ; 10502947 (ISSN) Bayat, A ; Karimipour, V ; Sharif University of Technology
    2005
    Abstract
    We study the effect of thermal fluctuations in a recently proposed protocol for transmission of unknown quantum states through quantum spin chains. We develop a low-temperature expansion for general spin chains. We then apply this formalism to study exactly thermal effects on short spin chains of four spins. We show that optimal times for extraction of output states are almost independent of the temperature, which lowers only the fidelity of the channel. Moreover we show that thermal effects are smaller in the antiferromagnetic chains than the ferromagnetic ones. © 2005 The American Physical Society  

    Low temperature synthesis of carbonate-free barium titanate nanoscale crystals: Toward a generalized strategy of titanate-based perovskite nanocrystals synthesis

    , Article Journal of the American Ceramic Society ; Vol. 97, issue. 7 , 2014 , pp. 2027-2031 Ashiri, R ; Moghtada, A ; Shahrouzianfar, A ; Ajami, R ; Sharif University of Technology
    Abstract
    Synthesis temperature and purity of perovskite materials are key challenges facing the scientific community. This work aims to address these challenges by developing an innovative low temperature synthesis pathway for preparation of carbonate-free perovskite nanocrystals. The method is based on an ultrasound-Assisted wet chemical processing method. Nanocrystals are characterized and observed by X-ray diffraction (XRD), field-emission scanning electron microscopy and high-resolution transmission electron microscopy techniques. XRD studies show that very fine BaTiO3 nanocrystals (<11 nm) free from any by-products such as BaTi2O5 and BaCO3 are synthesized at 50°C. Moreover, the method developed... 

    Thermal stability investigation of expanded martensite

    , Article Surface and Coatings Technology ; Volume 300 , 2016 , Pages 87-94 ; 02578972 (ISSN) Baniasadi, F ; Bahmannezhad, B ; Nikpoor, N ; Asgari, S ; Sharif University of Technology
    Elsevier  2016
    Abstract
    The aim of this work is to investigate thermal stability of expanded martensite. For this purpose, two martensitic stainless steels, PH 17-4 and 13-8Mo, were low temperature gas carburized. After heat treatment, it was found out that thermal stability of expanded layer of PH 17-4 is higher than that of PH 13-8Mo. Auger Electron Spectroscopy and microhardness machines were used to investigate carbon concentration and hardness of samples, respectively. X-ray diffraction was done to study crystal structures of samples before and after heat treatment  

    The formation of atomic nanoclusters on graphene sheets

    , Article Nanotechnology ; Volume 20, Issue 13 , 2009 ; 09574484 (ISSN) Neek Amal, M ; Asgari, R ; Rahimi Tabar, M. R ; Sharif University of Technology
    2009
    Abstract
    The formation of atomic nanoclusters on suspended graphene sheets has been investigated by employing a molecular dynamics simulation at finite temperature. Our systematic study is based on temperature-dependent molecular dynamics simulations of some transition and alkali atoms on suspended graphene sheets. We find that the transition atoms aggregate and make various size nanoclusters distributed randomly on graphene surfaces. We also report that most alkali atoms make one atomic layer on graphene sheets. Interestingly, the potassium atoms almost deposit regularly on the surface at low temperature. We expect from this behavior that the electrical conductivity of a suspended graphene doped by... 

    Ultra-high voltage SnO2 based varistors prepared at low temperature by two-step sintering

    , Article Journal of Alloys and Compounds ; Volume 805 , 2019 , Pages 794-801 ; 09258388 (ISSN) Maleki Shahraki, M ; Delshad Chermahini, M ; Alipour, S ; Mahmoudi, P ; Safaee, I ; Abdollahi, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    In this research, full density, single phase microstructure (in the XRD and SEM detection limits), and fine-grained SnO2 varistors with an average grain size of 0.65 μm was acquired at low temperature by the two-step sintering technique. The sintering temperature was successfully decreased from 1300 °C in the normal sintering to 1150 °C and 1100 °C of respectively the first and the second stage in the two-step sintering. The mechanism of grain growth suppression of the two-step sintered samples was discussed and it was suggested that in addition to triple point junction, solute drag and/or nano-secondary phases contribute to cease the grain growth. These SnO2 varistors exhibited ultra-high... 

    Sonochemical synthesis of SrTiO3 nanocrystals at low temperature

    , Article International Journal of Applied Ceramic Technology ; Volume 12, Issue S2 , 2015 , Pages E202-E206 ; 1546542X (ISSN) Ashiri, R ; Ajami, R ; Moghtada, A ; Sharif University of Technology
    Blackwell Publishing Ltd  2015
    Abstract
    This work aims to develop an innovative low-temperature sonochemical synthesis pathway for synthesizing the carbonate-free SrTiO3 nanocrystals with tailored morphology. Ultrasonication causes the formation of stoichiometric SrTiO3 nanocrystals and accelerates their formation. Moreover, SrTiO3 nanocrystals are synthesized at low temperature. The methodology described here is simple, fast, cost-effective, and useful for large-scale production purposes  

    Aluminum coatings on cotton fabrics with low temperature plasma of argon and oxygen

    , Article Surface and Coatings Technology ; Volume 201, Issue 9-11 SPEC. ISS , 2007 , Pages 5646-5650 ; 02578972 (ISSN) Shahidi, S ; Ghoranneviss, M ; Moazzenchi, B ; Anvari, A ; Rashidi, A ; Sharif University of Technology
    2007
    Abstract
    In this article, we have studied the properties (especially water repellency) of cotton coated by a thin layer of aluminum. The process has been performed in a low temperature plasma medium, using a magnetron sputtering device. We have also investigated the effect of different gases such as argon and oxygen as the discharge medium on the properties of the obtained samples. The results which are exposure time dependent show a good repellent property for 30 min of treating in argon medium under the condition of our experiment. However, when O2 is used in the system, the cotton property changes to become hydrophilic of which the factor decreases as we increase the time of treating. © 2006... 

    Thermal entanglement of spins in the Heisenberg model at low temperatures

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 70, Issue 5 A , 2004 , Pages 052307-1-052307-5 ; 10502947 (ISSN) Asoudeh, M ; Karimipour, V ; Sharif University of Technology
    2004
    Abstract
    The entanglement between two spins in the ferromagnetic Heisenberg chain at low temperatures was calculated. It was shown that if a magnetic field is applied to a ferromagnetic Heisenberg chain, then pairwise entanglement develops between spins at arbitrary given states. It was also shown that the entanglement profile is a Gaussian with a characteristic length depending on the temperature and the coupling between spins only when the ground state and the one-particle states are populated. The magnetic field was shown to affect only the amplitude of the profile and not its characteristic length  

    Experimental and numerical investigation of low-temperature performance of modified asphalt binders and mixtures

    , Article Road Materials and Pavement Design ; 2016 , Pages 1-22 ; 14680629 (ISSN) Jahanbakhsh, H ; Karimi, M. M ; Tabatabaee, N ; Sharif University of Technology
    Taylor and Francis Ltd  2016
    Abstract
    Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

    Experimental and numerical investigation of low-temperature performance of modified asphalt binders and mixtures

    , Article Road Materials and Pavement Design ; Volume 18, Issue 6 , 2017 , Pages 1353-1374 ; 14680629 (ISSN) Jahanbakhsh, H ; Karimi, M. M ; Tabatabaee, N ; Sharif University of Technology
    Abstract
    Thermal cracking is the prevalent type of distress experienced by asphalt pavements in cold regions. It is widely assumed that when thermal stresses induced in the pavement exceed the tensile strength of the asphalt surface layer, cracking occurs; however, the role of thermal fatigue should not be ignored. To better describe the low-temperature (LT) performance properties of modified asphalt binders, a new parameter, normalised tensile stress (NTS), was defined in this research. NTS values were compared with bending beam rheometer (BBR), direct tension (DT) and semi-circular bending (SCB) fracture test results. The m-value parameter of the BBR test specifies the type of asphalt binder. This... 

    Low-temperature solution-based processing to 7.24% efficient superstrate CuInS2 solar cells

    , Article Solar Energy ; Volume 157 , 2017 , Pages 581-586 ; 0038092X (ISSN) Cheshme Khavar, A.H ; Mahjoub, A. R ; Taghavinia, N ; Sharif University of Technology
    Elsevier Ltd  2017
    Abstract
    The fabrication of high performance, solution-processed CIGS family solar cells is based on high-temperature crystallization processes in chalcogen-containing atmosphere and/or using dangerous solvents like hydrazine. The non-hydrazine sulfurization- and selenization-free reports typically suffer from poor grain structures. We report a facile strategy to overcome grain growth limitations at very low temperature processing (250 °C). Selenium free Superstrate configuration CuInS2 (CIS) solar cells are fabricated using a nanocrystals ink which avoiding from high temperature selenization or/and sulfurization is targeted. We investigated the effect of intentional M doping (M = Sb, Zn, Cd and Sn)... 

    New approaches in lowering the gas-phase synthesis temperature of TiO2 nanoparticles by H2O-assisted atmospheric pressure CVS process

    , Article Journal of Materials Research and Technology ; Volume 8, Issue 3 , 2019 , Pages 3024-3035 ; 22387854 (ISSN) Rahiminezhad Soltani, M ; Saberyan, K ; Simchi, A ; Gammer, C ; Sharif University of Technology
    Elsevier Editora Ltda  2019
    Abstract
    H2O-assisted atmospheric pressure chemical vapor synthesis is a modern economical process for the gas-phase synthesis of TiO2 nanoparticles. In the present work, the influence of synthesis temperatures (100-800 °C) on the phase structure, nanoparticle size, morphology, and agglomeration is investigated by transmission electron microscopy, selected area electron diffraction, X-ray diffraction, thermogravimetry, and differential thermal analysis. Down to 400 °C, crystalline TiO2 nanoparticles are synthesized and at 200 °C amorphous nanoparticles are formed. Therefore, a decrease in minimum synthesis temperature by more than 500 °C is achieved. In addition, the paper investigates the hypothesis... 

    Microstructure Investigation of Low Temperature Carburized Precipitation Hardenable 17-4 And 13-8 Mo Stainless Steels

    , M.Sc. Thesis Sharif University of Technology Baniasadi, Fazel (Author) ; Asgari, Sirous (Supervisor)
    Abstract
    Recently, low temperature carburizing of stainless steels, especially austenitic stainless steels, have been considered by so many researchers. The improvement of tribological properties of which is so impressive so much so that such properties like hardness and wear resistance increase to manifold. In this research, low temperature carburizing was done on two kinds of precipitation hardenable stainless steels 17-4 and 13-8 Mo. After that, microstructural investigations were done on the carburized surfaces and in 5, 10, 20, 80, and 150 micrometer depths. Moreover, in each depth, in order to phase structure and tribological properties investigation, XRD and microhardness tests were done,... 

    On the Microstructure and Mechanical Properties of Aluminum after Low-temperature Multi-directional Forging

    , M.Sc. Thesis Sharif University of Technology Alyani, Ali (Author) ; Kazeminezhad, Mohsen (Supervisor)
    Abstract
    Severe Plastic Deformation (SPD) has been used as an effective approach to access fine grain (FG) and ultra-fine grain (UFG) materials.the Temperature of SPD is a dominant parameter to controlling ultimate properties. SPD at room-temperature and the high temperature was used widely in literature but the low-temperature process (sub-zero and cryogenic temperatures) was not used comparably. In this study, Low-temperature Multi-Directional Forging (LMDF) was applied on commercially pure aluminum and room-temperature MDF (RMDF) was attained for contrast temperature effects, and resulting in more fine grains. The grain refinement was attributed to the fragmentation process with a limitation in... 

    Investigation and Accomplishment of CO2 Capturing with Solid Sorbent

    , M.Sc. Thesis Sharif University of Technology Shirdel, Elham (Author) ; Safekordi, Ali Akbar (Supervisor)
    Abstract
    Carbon dioxide emissions account for 80% of current greenhouse gas emissions that contribute to global warming; this majority stake held by carbon dioxide indicates that reduction in its release to the atmosphere and capturing emissions accomplished is imperative in conservation of human life in earth. The aim of this project is CO2 capturing from ambient air to decrease air pollution with uses building surface that is wide available surface, as basis of adsorbent. In this research, we select CaO as absorbent that it is proven good absorbent in high temperature for CO2. We studied this absorbent in low temperature and pressure. We experimented different weight amount of sorbent 2,3,4,5,6.5... 

    Evaluation of Warm Mix Asphalt containing Sasobit

    , M.Sc. Thesis Sharif University of Technology Naderi, Behzad (Author) ; Tabatabaee, Nader (Supervisor)
    Abstract
    Warm mix asphalt has received considerable attention over the past decade particularly due to its potential environmental benefit such as lower energy consumption and emission, its ability to be placed at lower ambient temperatures making it a suitable material for areas with short construction season. There are three warm mix asphalt (WMA) techniques are available; organic additive, foaming, and chemical additive. This study examined Sasobit, a micro crystalline wax which is an organic additive. The concentrations tested were 1.5, 2.5 and 3.5 percent of the base binder. A PG 64-22 asphalt binder from an Iranian refinery (Tehran refinery) was used as the base binder. Superpave binder... 

    Spark plasma sintering of TaC-HfC UHTC via disilicides sintering aids

    , Article Journal of the European Ceramic Society ; Volume 33, Issue 8 , 2013 , Pages 1479-1484 ; 09552219 (ISSN) Ghaffari, S. A ; Faghihi-Sani, M. A ; Golestani Fard, F ; Mandal, H ; Sharif University of Technology
    2013
    Abstract
    Ta0.8Hf0.2C ceramic has the highest melting point among the known materials (4000°C). Spark plasma sintering is a new route for consolidation of materials, specially ultra high temperature ceramics (UHTCs), which are difficult to be sintered at temperatures lower than 2000°C.The purpose of this study is to consolidate Ta0.8Hf0.2C by spark plasma sintering at low temperature using MoSi2 and TaSi2 as sintering aid. In this regard, effect of different amounts of sintering aids and carbides ratio on densification behavior and mechanical properties of Ta1-xHfxC were investigated.Fully consolidation of Ta0.8Hf0.2C was achieved in presence of 12vol.% sintering aid after sintering at 1650°C for 5min... 

    Mechanism of 1,12-Dicarba-closo-dodecaborane Mobility on Gold Substrate as a Nanocar Wheel

    , Article Journal of Physical Chemistry C ; Volume 120, Issue 26 , 2016 , Pages 14048-14058 ; 19327447 (ISSN) Hosseini Lavasani, S.M ; Nejat Pishkenari, H ; Meghdari, A ; Sharif University of Technology
    American Chemical Society  2016
    Abstract
    We studied the mobility of p-carborane on a gold surface by analyzing the potential energy surfaces (PES) and simulating the motion of p-carborane using the classical molecular dynamics (MD) method. In the first section, we calculated the PES of p-carborane molecules on a gold surface during pure translation (sliding) and pure rotation independently and then employed this PES to predict the probable motion of p-carborane. These calculations were performed in several major orientations during sliding as well as different fixed positions during rotational movements to enable us to find the p-carborane motion threshold on a gold surface. In the second section, we use classical MD in isothermal...