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    Simulation of imaging in tapping-mode atomic-force microscopy: a comparison amongst a variety of approaches

    , Article Journal of Physics D: Applied Phyics ; Vol.44, Number 7, p.1-9, 2011 Nejat Pishkenari, H ; Mahboobi, S. H ; Meghdari, A. (Ali) ; Sharif University of Technology
    Models capable of accurate simulation of microcantilever dynamics coupled with complex tip–sample interactions are essential for interpretation and prediction of the imaging results in amplitude modulation or tapping-mode atomic-force microscopy (AM-AFM or TM-AFM). In this paper, four approaches based on combinations of lumped and finite element methods for modelling of cantilever dynamics, and van der Waals and molecular dynamics for modelling of tip–sample interactions, are used to simulate the precise imaging by AM-AFM. Based on the simulated imaging and force determination, the efficiency of different modelling schemes is evaluated. This comparison is performed considering their... 

    Dosimetric evaluation of a newly developed radiochromic film for radiation processing

    , Article Iranian Journal of Science and Technology, Transaction A: Science ; Volume 31, Issue 4 , 2007 , Pages 397-401 ; 10286276 (ISSN) Akhavan, A ; Sohrabpour, M ; Sharifzadeh, M ; Sharif University of Technology
    Shiraz University  2007
    In order to improve the performance of a newly developed radiochromic film, GIC-79, some dosimetric characteristics of this film have been studied based on relevant standard practice. The present study describes some parameters that may affect the dosimeter response before, during, and after irradiation. The effect of absorbed dose rate on dosimeter response was determined by irradiating dosimeters at low absorbed dose rates with gamma rays. Calibration irradiations of dosimeters were performed with both gamma rays and also electrons to determine the effect of large difference absorbed dose rates on dosimeter response. In addition, post irradiation stability was obtained and also 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... 

    The effect of grain size on the fluctuation-induced conductivity of Cu 1-xTlxBa2Ca3Cu4O 12-δ superconductor thin films

    , Article Superconductor Science and Technology ; Volume 20, Issue 8 , 2007 , Pages 742-747 ; 09532048 (ISSN) Khurram, A. A ; Mumtaz, M ; Khan, N.A ; Ahadian, M. M ; Iraji Zad, A ; Sharif University of Technology
    The high temperature superconductor thin films Cu1-xTl xBa2Ca3Cu4O12-δ (Cu1-xTlx- 1234) are post-annealed in a nitrogen atmosphere. The zero-resistivity critical temperature (Tc(R ≤ 0)) of these thin films is increased from 92.3 to 104K. The grain size is enhanced and their morphology is improved with the post-annealing. The enlargement of grain size is linked to fluctuation-induced conductivity (FIC) in the light of Aslamazov-Larkin (AL) theory. The FIC measurements have shown that the cross-over of three-dimensional (3D) to two-dimensional (2D) behaviour of fluctuations is shifted to higher temperature values with an increase of post-annealing temperature. These results have shown that the... 

    Tube bundle heat and mass transfer characteristics in falling film absorption generators

    , Article International Communications in Heat and Mass Transfer ; Volume 30, Issue 4 , 2003 , Pages 565-576 ; 07351933 (ISSN) Jani, S ; Saidi, M. H ; Mozaffari, A. A ; Sharif University of Technology
    Falling film heat and mass transfer analysis of a horizontal tube bundle in a generator of absorption chillers have been studied. The film Reynolds number is limited to the laminar flow and the effect of ripple on the free surface has been ignored. Thermal boundary conditions are considered to be constant wall temperature and desorption is considered to be free surface evaporation. Analysis is based on a single column of horizontal tubes, arranged in a vertically spaced configuration. A comprehensive numerical code has been developed to solved the governing equations. The functional relationship of average heat transfer coefficient of tube bundle has been analytically correlated to the first... 

    Development of biodegradable food packaging plastic films

    , Article Iranian Journal of Science and Technology, Transaction B: Technology ; Volume 27, Issue 2 , 2003 , Pages 299-304 ; 03601307 (ISSN) Frounchi, M ; Dadbin, S ; Karimi, S ; Sharif University of Technology
    Biodegradable thermoplastic films suitable for use in food packaging were produced. These films were mainly based on thermoplastic starch. The major task included research into thermal conversion of starch in a compression molding process and also under high shear conditions in an extruder in the presence of suitable plasticizers. The destruction of crystalline structure resulted in amorphous structure with thermoplastic properties. Films were rather transparent but slightly brown in color and had a specific smell. The films showed sufficient plasticity and acceptable tensile strength and elongation. The effect of plasticizer content on the final properties of the film was investigated. The... 

    Percolation of cadmium across a mercury film

    , Article Materials Chemistry and Physics ; Volume 78, Issue 3 , 2003 , Pages 796-799 ; 02540584 (ISSN) Malek, K ; Gobal, F ; Sharif University of Technology
    Electrodeposition/dissolution of cadmium onto a film of mercury shows some deviations from the natural liquidity of mercury caused by the reduction of Cd onto it. Percolation and fractal analyzes were done on the surface and the bulk of the mercury film during diffusion of Cd species (atoms). These show that the fractal dimensions of the Cd-inserted mercury film are about 2.11 and 2.54 near the surface of the mercury film and at deeper points inside the film, respectively. The insertion process has a negligible effect on the surface morphology of the mercury film and there is a phase transition in the bulk, as well as a geometrical transition during the Cd-insertion (de-insertion) process.... 

    Theory of the liquid film motor

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , September , 2015 ; 15393755 (ISSN) Feiz, M. S ; Namin, R. M ; Amjadi, A ; Sharif University of Technology
    American Physical Society  2015
    The liquid film motor is a freely suspended liquid film placed between two capacitively coupled plates that rotates when an electric current is passed through it. Here we propose a theory for its rotation mechanism based on thin film electroconvection. The capacitively coupled plates induce free charges on the surfaces of the film, and the electric field on the film exerts a force that induces rotation. Results of the proposed theory and simulation are in good agreement with the experiments in different properties of the liquid film motor  

    The effect of annealing temperature on the statistical properties of WO3 surface

    , Article Journal of Statistical Mechanics: Theory and Experiment ; Issue 9 , 2006 ; 17425468 (ISSN) Jafari, G. R ; Saberi, A. A ; Azimirad, R ; Moshfegh, A. Z ; Rouhani, S ; Sharif University of Technology
    We have studied the effect of annealing temperature on the statistical properties of WO3 surface using atomic force microscopy (AFM) techniques. We have applied both level crossing and structure function methods. Level crossing analysis indicates an optimum annealing temperature of around 400°C at which the effective area of the WO3 thin film is maximum, whereas the composition of the surface remains stoichiometric. The complexity of the height fluctuation of surfaces was characterized by roughness, the roughness exponent and the lateral size of surface features. We have found that there is a phase transition at around 400°C from one set to two sets of roughness parameters. This happens due... 

    Rotational regimes of freely suspended liquid crystal films under electric current in presence of an external electric field

    , Article Microfluidics and Nanofluidics ; Volume 13, Issue 1 , 2012 , Pages 83-89 ; 16134982 (ISSN) Shirsavar, R ; Amjadi, A ; Ejtehadi, M. R ; Mozaffari, M. R ; Feiz, M. S ; Sharif University of Technology
    The electrohydrodynamic (EHD) vortices produced by an electric current in freely suspended liquid crystal (LC) films of N-(4-methoxybenzylidene)-4- butylaniline (MBBA), convert to a pure rotation in the presence of external electric field (E ext) perpendicular to the current direction. Here, the direction and strength of the rotation are precisely under control by our self-made device called "liquid-film motor". In this paper, we present experimental observations of the EHD fluid flow when external electric field varies from zero to a value in which pure rotation on the liquid crystal (LC) film is observed. We also show experimentally that the presence of external electric field causes a... 

    Microstructure and thermochromic properties of VOX–WOX–VOX ceramic thin films

    , Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 3 , 2016 , Pages 1-5 ; 09478396 (ISSN) Khamseh, S ; Araghi, H ; Ghahari, M ; Faghihi Sani, M. A ; Sharif University of Technology
    Springer Verlag  2016
    W-doped VO2 films have been synthesized via oxygen annealing of V–W–V (vanadium–tungsten–vanadium) multilayered films. The effects of middle layer’s thickness of V–W–V multilayered film on structure and properties of VOX–WOX–VOX ceramic thin films were investigated. The as-deposited V–W–V multilayered film showed amorphous-like structure when mixed structure of VO2 (M) and VO2 (B) was formed in VOX–WOX–VOX ceramic thin films. Tungsten content of VOX–WOX–VOX ceramic thin films increased with increasing middle layer’s thickness. With increasing middle layer’s thickness, room temperature square resistance (Rsq) of VOX–WOX–VOX ceramic thin films increased from 65 to 86 kΩ/sq. The VOX–WOX–VOX... 

    Functionalized carbon nanotubes in ZnO thin films for photoinactivation of bacteria

    , Article Materials Chemistry and Physics ; Volume 130, Issue 1-2 , October , 2011 , Pages 598-602 ; 02540584 (ISSN) Akhavan, O ; Azimirad, R ; Safa, S ; Sharif University of Technology
    Two types of unfunctionalized and functionalized multi-wall carbon nanotubes (MWCNTs) were prepared to be applied in fabrication of MWCNT-ZnO nanocomposite thin films with various MWCNT contents. X-ray photoelectron spectroscopy indicated formation of functional groups on surface of the functionalized MWCNTs in the MWCNT-ZnO nanocomposite. Formation of the effective carbonaceous bonds between the ZnO and the MWCNTs was also investigated through photoinactivation of Escherichia coli bacteria on surface of the both unfunctionalized and functionalized MWCNT-ZnO nanocomposites. The functionalized MWCNT-ZnO nanocomposites showed significantly stronger photoinactivation of the bacteria than the... 

    Two-stage chemical deposition of oxide films

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 21, Issue 1 , 2008 , Pages 65-70 ; 1728-144X (ISSN) Vaezi, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
    Materials and Energy Research Center  2008
    Two-stage chemical deposition (TSCD) technique is used to produce ZnO, Mn2O3 and NiO films on soda-lime glass (SL-G) from an aqueous solution of zinc, manganese and nickel complex, respectively. The TSCD method enables the deposition of metal oxide thin films with a thickness which can be controlled during the preparation procedure. The ZnO, Mn 2O3 and NiO thin films were polycrystalline films which were adherent well to the substrates. The SEM micrographs clearly indicate that the zinc oxide layer is composed of oval shaped crystallites preferably orientated perpendicular to the surface of the substrate. The Mn 2O3 and NiO layers were closely packed on the substrate. These particles seem to... 

    Dewetting of evaporating thin films over nanometer-scale topographies

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Vol. 90, issue. 1 , July , 2014 ; ISSN: 15393755 Akbarzadeh, A. M ; Moosavi, A ; Moghimi Kheirabadi, A ; Sharif University of Technology
    A lubrication model is used to study dewetting of an evaporating thin film layer over a solid substrate with a nanometer-scale topography. The effects of the geometry of the topography, the contact angle, the film thickness, and the slippage on the dewetting have been studied. Our results reveal that the evaporation enhances the dewetting process and reduces the depinning time over the topography. Also it is shown that the depinning time is inversely proportional to the slippage and increasing the contact angle may considerably reduce the depinning time, while the film thickness increases the depinning time  

    TiO2 nanostructured films on mica using liquid phase deposition

    , Article Materials Chemistry and Physics ; Volume 107, Issue 2-3 , 2008 , Pages 449-455 ; 02540584 (ISSN) Pourmand, M ; Taghavinia, N ; Sharif University of Technology
    Liquid phase deposition is a method to grow conformal TiO2 films with good crystallinity on various substrates. The growth depends on the hydrophilicity of the substrate surface and we found that mica is a substrate capable of forming uniform and thick films. Films were grown using an aqueous solution of TiF4 through a hydrolysis-condensation process. We have studied films properties; morphology, porosity and thickness, in terms of growth conditions, i.e. TiF4 concentration, growth temperature, deposition time and pH. The porosity of films was shown to rapidly increase from about 18% to about 25% and remained the same for longer growth times. The growth process of films could be identified... 

    Gas permeability measurement in polyethylene and its copolymer films

    , Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) Gholizadeh, M ; Razavi, J ; Mousavi, A ; Sharif University of Technology
    In this research, low density polyethylene (LDPE) and poly ethylene-co-vinyl acetate (EVA) were used as polymeric materials. The methods used to produce LDPE and EVA was Film Blowing and ThermalDry Phase Inversion. The amount of permeability, diffusivity and solubility of O2 and CO2 through above polymers were obtained and also the effect of temperature, pressure and film thickness for LDPE was measured. The Barometric method was considered and measurements were based on ASTM standard. To study film cross-section morphology in EVA, Scanning Electron Microscopy (SEM) was applied. From results we considered that the amount of permeability and solubility were decreased by increasing film... 

    Sintering characterizations of Ag-nano film on silicon substrate

    , Article Advanced Materials Research ; Volume 829 , 2014 , Pages 342-346 ; ISSN: 10226680 ; ISBN: 9783037859070 Keikhaie, M ; Akbari, J ; Movahhedi, M. R ; Alemohammad, H ; Sharif University of Technology
    Nowadays, thin films have many applications in every field. So, in order to improve the performance of thin film devices, it is necessary to characterize their mechanical as well as electrical properties. In this research work we focus on the development of a model for the analysis of the mechanical and electrical properties of silver nanoparticles deposited on silicon substrates. The model consists of inter-particle diffusion modeling and finite element analysis. In this study, through the simulation of the sintering process, it is shown that how the geometry, density, and electrical resistance of the thin film layer are changed with sintering conditions. The model is also used to... 

    MWCNT/WO3 nanocomposite photoanode for visible light induced water splitting

    , Article Journal of Solid State Chemistry ; Volume 204 , 2013 , Pages 341-347 ; 00224596 (ISSN) Yousefzadeh, S ; Reyhani, A ; Naseri, N ; Moshfegh, A. Z ; Sharif University of Technology
    The Multi-walled carbon nanotube (MWCNT)/WO3 nanocomposite thin films with different MWCNT's weight percentages were prepared by sol-gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO3 thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO3. The influence of different weight percentage (wt%) of MWCNT on WO3 photoactivity showed that the electron... 

    Pt and Pd as catalyst deposited by hydrogen reduction of metal salts on WO3 films for gasochromic application

    , Article Applied Surface Science ; Volume 273 , May , 2013 , Pages 261-267 ; 01694332 (ISSN) Tahmasebi Garavand, N ; Mahdavi, S. M ; Iraji Zad, A ; Sharif University of Technology
    In this study, tungsten oxide films were deposited by pulsed-laser deposition (PLD) technique. The as-deposited films were annealed at 250 °C in air for 1 h. The surface morphology, microstructure, crystalline phase, and chemical composition of the films were characterized by SEM, XRD and XPS techniques. Pt nanoparticles were deposited onto the tungsten oxide films through a two-step process. First of all, a layer of PtCl2 was coated on the WO3 surface by drop-drying the PtCl2 solution onto the WO3 surface at 60 °C. Consequently, the reduction of the PtCl2 into the metallic Pt nanoparticles was performed at 200 °C. In this study, the effect of the temperature during hydrogen reduction of... 

    Nanodiamond Decorated with Silver Nanoparticles as a Sensitive Film Modifier in a Jeweled Electrochemical Sensor: Application to Voltammetric Determination of Thioridazine

    , Article Electroanalysis ; Volume 25, Issue 2 , 2013 , Pages 417-425 ; 10400397 (ISSN) Shahrokhian, S ; Hosseini Nassab, N ; Sharif University of Technology
    Nanodiamond-graphite (NDG) decorated with Ag nanoparticles (AgNPs-NDG) was prepared and used to construct a novel sensitive sensor for the voltammetric determination of thioridazine (TR). The results indicate a remarkable increase in the oxidation peak currents together with a negative shift in the oxidation peak potentials, in comparison to the bare pyrolytic graphite electrode. Remarkable enhancement in microscopic area of the electrode along with strong adsorption of TR on the surface of the modified electrode resulted in a considerable increase in the peak current of TR. The surface morphology and the nature of the composite film deposited on PGE were characterized by scanning electron...