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Total 75 records

    Study on Effects of Short Wood Fibers on Physical and Mechanical Properties of Biodegradable Composite Based on Thermoplastic Starch

    , M.Sc. Thesis Sharif University of Technology Pesaran Haji Abbas, Ehsan (Author) ; Bagheri, Reza (Supervisor) ; Sayyed Reihani, Morteza (Supervisor)
    Abstract
    Due to the negative effects of conventional plastics on the enviroment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good processability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of natural... 

    “ Nano Oxide Layer Forming on the Surface of Porous Nitinol Shape Memory Alloy for Improving Surface Properties “

    , M.Sc. Thesis Sharif University of Technology Fattahzadeh, Mehrdad (Author) ; Sadrnejhad, Khatiboleslam (Supervisor)
    Abstract
    In this project ,it has been done different surface treatment on 6 samples of nitinol with 40 % prosity,three of them are anodized by H2SO4 ,Hf, Acetic acid, one of them is treated with plasma spray with TIO2 powder, one of them is putted in the furnace at 700 degrees for an hour, and the last one is bare ; Moreover, these treated samples are putted in Simulated body fluid for 16 days . After this period of time, we analyzed the results. Then the cell adhesion amount of osteo blast cells (MG 63) is measured to these samples by immersing them for 3 days in these cells.The results are investigated by SEM ,XRD(X pertpro produced by Panalitical), XRF(530-XRF-01), AAS( AA240), Roughness measuring... 

    Developing an Analytical Model for Predicting the Residual Stresses Induced by Shot Peening with Considering the Effect of Initial Surface Treatment

    , Ph.D. Dissertation Sharif University of Technology Sherafatnia, Khalil (Author) ; Farrahi, Gholam Hossein (Supervisor) ; Mahmoudi, Amir Hossein (Co-Supervisor)
    Abstract
    Shot peening is a cold-working process commonly used in industry to improve the fatigue performance, stress corrosion resistance and surface nano-crystallization of metallic parts. This process extends fatigue life via two mechanisms: Preventing the crack growth due to compressive residual stresses and, preventing the crack initiation because of increased material hardness. These mechanisms are the results of the bombardment of the component's surface with small spherical particles. In this research, an analytical model is developed for estimating the residual stress distribution induced by shot peening process. The modifications of the developed analytical model are related to... 

    hysical and Chemical Surface Modification of Titanium by Nanostructured Materials, and Biological Characterization for Use in Bone Tissue Implants

    , Ph.D. Dissertation Sharif University of Technology Rahnamaee, Yahya (Author) ; Bagheri, Reza (Supervisor) ; Vossoughi, Manochehr (Supervisor) ; Samadi Kuchaksaraei, Ali (Supervisor)
    Abstract
    According to human needs and in line with the development of advanced technologies, different biomedical Engineering fields like hard tissue implants are growing rapidly. Despite significant biotechnology Developments in recent years, some problems to the recognition of implants related osseointegration phenomena persist. The deficient osseointegration and implant-associated infections are key issues for the long-term clinical success of titanium and titanium alloy implants, while development of multifunctional surfaces that can simultaneously overcome these problems remains highly challenging. Therefore, the ultimate goal of this paper was to improve bone cell attachment and simultaneously... 

    , M.Sc. Thesis Sharif University of Technology (Author) ; Ghorbani, Mohammad (Supervisor)
    Abstract
    In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg)... 

    Enhanced Electronic Properties in Mesoporous TiO2 Via Passivation Treatment in Perovskite Solar Cells

    , M.Sc. Thesis Sharif University of Technology Azadi, Moloud (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Abstract
    Perovskite solar cells are the new generation of solar cells, and are mainly introduced in two types of structures.1) planer and 2) mesoscopic structure. The difference between these two structures derives from the absence of mesoporous layer in the planer structures. The mesoporous layer acts as an electron transporting layer, and is mainly a titanium dioxide semiconductor. To apply the mesoporous layer, the preparation of the TiO2 paste is needed.The synthesis of titanium dioxide nanopowder for the preparation of TiO2 paste requires high temperature heat treatment and is not desirable in terms of energy consumption.Another weakness of this layer is the presence of surface defects, which... 

    Efficiency improvement of solar stills through wettability alteration of the condensation surface: An experimental study

    , Article Applied Energy ; Volume 268 , 2020 Zanganeh, P ; Soltani Goharrizi, A ; Ayatollahi, S ; Feilizadeh, M ; Dashti, H ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    The condensation process is of great importance in many heat transfer devices in which a large amount of energy must be transferred. Furthermore, condensation is a crucial part of energy conversion and affects the energy efficiency of thermal desalination plants and solar stills. During the condensation process in solar stills, an essential part of the energy is transferred through the condensation surface to produce fresh water. Therefore, the condensation surface plays a significant role in the working efficiency of solar stills. The wettability of the condensation surface influences the condensation mechanism, which, in turn, affects the efficiency of solar stills. This study aims to... 

    Energy aspects and workpiece surface characteristics in ultrasonic-assisted cylindrical grinding of alumina-zirconia ceramics

    , Article International Journal of Machine Tools and Manufacture ; Volume 90 , 2015 , Pages 16-28 ; 08906955 (ISSN) Zahedi, A ; Tawakoli, T ; Akbari, J ; Sharif University of Technology
    Abstract
    Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina-zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the... 

    Melt compounding of thermoplastic polyurethanes incorporating 1D and 2D carbon nanofillers

    , Article Polymer - Plastics Technology and Engineering ; Volume 56, Issue 7 , 2017 , Pages 732-743 ; 03602559 (ISSN) Yuan, D ; Pedrazzoli, D ; Pircheraghi, G ; Manas Zloczower, I ; Sharif University of Technology
    Taylor and Francis Inc  2017
    Abstract
    Thermoplastic polyurethane nanocomposites incorporating carbon nanotubes and graphene nanoplatelets were prepared through melt blending and compression molding, and the compounding process was optimized taking into account the different physical properties of one-dimensional carbon nanotubes and two-dimensional graphene nanoplatelets. Filler dispersion was further improved in the case of carbon nanotubes by noncovalent surface modification using a specific surfactant. The well-dispersed nanofillers favored enhanced phase separation in the thermoplastic polyurethane, leading to a better microstructure, which is able to improve the load transfer and maximize the tensile and viscoelastic... 

    Self cleaning TiO2 coating on polycarbonate: Surface treatment, photocatalytic and nanomechanical properties

    , Article Surface and Coatings Technology ; Volume 204, Issue 9-10 , 2010 , Pages 1562-1568 ; 02578972 (ISSN) Yaghoubi, H ; Taghavinia, N ; Keshavarz Alamdari, E ; Sharif University of Technology
    Abstract
    A developed route to form TiO2 self cleaning coatings on polycarbonate substrates is reported. TiO2 coatings on plastics may find widespread application in auto and construction industries if possess desired photocatalytic and mechanical properties. A chemical surface treatment method was used to create hydrophilic groups on the surface. X-ray photoelectron spectroscopy showed the treatment led to the oxidation of surface groups. TiO2 deposition was based on wet coating using an anatase sol of TiO2 nanoparticles of 30 nm size. The sol was synthesized using a sol-gel route. A pre-coat of peroxotitanium complex was employed to improve adhesion and inhibit the substrate degradation. The coating... 

    CaTiO3/α-TCP coatings on CP-Ti prepared via electrospinning and pulsed laser treatment for in-vitro bone tissue engineering

    , Article Surface and Coatings Technology ; Volume 401 , 2020 Yadi, M ; Esfahani, H ; Sheikhi, M ; Mohammadi, M ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this study, the in-vitro bone regeneration ability of commercial pure titanium (CP-Ti) surface modified via electrospun polyvinylidene/hydroxyapatite (PVP/HA) masking and subsequent Nd-YAG pulsed laser treatment was investigated. The ratio of HA to PVP played a significant role in achieving a perfect homogenous mask on the CP-Ti. In the laser treatment process, the parameter of area scanning speed (ASS) had an important influence on the final surface morphology. A favorable range was defined for this parameter where these two conditions were satisfied: no PVP remaining and no severe substrate melting. Within a favorable range of ASS, as decreasing ASS exchanged the surface structure from... 

    Effects of severe plastic deformation on pre-osteoblast cell behavior and proliferation on AISI 304 and Ti-6Al-4V metallic substrates

    , Article Surface and Coatings Technology ; Volume 366 , 2019 , Pages 204-213 ; 02578972 (ISSN) Tevlek, A ; Aydın, H. M ; Maleki, E ; Varol, R ; Unal, O ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    In this study, titanium alloy (Ti-6Al-4V) and austenitic stainless steel (AISI 304) biomedical alloys were subjected to surface severe plastic deformation (SSPD) via severe shot peening (SSP) with the conditions of A28-30 Almen intensity. SSP is widely accepted as much more effective than the conventional surface modification techniques since it forms a nano-grain layer with large number of dislocations and grain boundaries. The SSP treatment in this study was led to a very thin rough layer in Ti-6Al-4V titanium alloy compared to that of AISI 304. The thicker layer of AISI 304 was created by twin-twin intersections and a martensite structure transformations. SSP treatment was resulted in a... 

    Surface modification of a hole transporting layer for an efficient perovskite solar cell with an enhanced fill factor and stability

    , Article Molecular Systems Design and Engineering ; Volume 3, Issue 5 , 2018 , Pages 717-722 ; 20589689 (ISSN) Tavakoli, M. M ; Tavakoli, R ; Prochowicz, D ; Yadav, P ; Saliba, M ; Sharif University of Technology
    Abstract
    The improvement of the quality of the hole transporting layer (HTL) plays a key role in the fabrication of highly efficient and stable perovskite solar cells (PSCs). Here, we used rubrene as a surface treatment agent on top of a spiro HTL. We found that rubrene can cover the pinholes of the spiro layer and provide an excellent contact layer for planar PSCs. Based on this modification, mobile gold ions from the metal electrode are prevented from diffusing through the HTL hindering the degradation of PSCs. The optimized device shows a maximum power conversion efficiency (PCE) of 19.87% and a 79% fill factor (FF), which are higher than the 17.98% PCE and 72% FF of the reference device. In... 

    Adhesion modification of polyethylenes for metallization using radiation-induced grafting of vinyl monomers

    , Article Surface and Coatings Technology ; Volume 201, Issue 16-17 , 2007 , Pages 7519-7529 ; 02578972 (ISSN) Shojaei, A ; Fathi, R ; Sheikh, N ; Sharif University of Technology
    2007
    Abstract
    The present paper demonstrates the performance of the radiation grafting technique as a chemically based surface pretreatment method to adhesion modification of polyethylene surfaces toward the metallic layer. Gamma irradiation over a dose range of 4-10 kGy is used for grafting of vinyl monomers including acrylamide (AAm) and 1-vinyl-2-pyrrolidone (NVP) onto the surface of three different polyethylenes including low density polyethylene (LDPE) and two kinds of high density polyethylenes, namely HDPE-1 and HDPE-2. The grafting yield is evaluated based on the weight increase of the samples. It is found that the grafting yield is dominated by the crystallinity of the polyethylene, so that lower... 

    Study of nanocrystallization in FINEMET alloy by active screen plasma nitriding

    , Article Journal of Alloys and Compounds ; Volume 491, Issue 1-2 , 2010 , Pages 487-494 ; 09258388 (ISSN) Shivaee, H. A ; Madaah Hosseini, H. R ; Memarzadeh Lotfabad, E ; Roostaie, S ; Sharif University of Technology
    2010
    Abstract
    The nanocrystallization process of amorphous Fe73.5Si13.5B9Nb3Cu 1 was investigated by active screen plasma nitriding (ASPN) treatment at temperatures ranging from 410 °C to 560 °C for 3 h in two gas mixtures of 75% N2-25% H2 and 25% N2-75% H2 at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum at the same time and temperatures mentioned above. The structure of the samples was analyzed using various techniques such as X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Microhardness measurements, electrical resistivity and Vibrating Sample Magnetometer (VSM) were used to study mechanical, electrical and magnetic... 

    Scattering of a Gaussian beam by a spherical dielectric object using the vectorial Gaussian beam tracing method

    , Article ICCEA 2004 - 2004 3rd International Conference on Computational Electromagnetics and its Applications, Beijing, 1 November 2004 through 4 November 2004 ; 2004 , Pages 72-75 ; 0780385624 (ISBN); 9780780385627 (ISBN) Shishegar, A. A ; Sharif University of Technology
    2004
    Abstract
    Scattering of a Gaussian beam by a spherical dielectric object is studied using the vectorial Gaussian beam tracing method. Expansion to a few Gaussian beams with the smaller waists has been used to extend the method to a more generalized one. This method can be applied to a large variety of different shape objects and incident beam profiles. Numerical results of this computationally fast method show a good agreement with the results represented in the literature. © 2004 IEEE  

    Effect of initial surface treatment on shot peening residual stress field: analytical approach with experimental verification

    , Article International Journal of Mechanical Sciences ; Volume 137 , 2018 , Pages 171-181 ; 00207403 (ISSN) Sherafatnia, K ; Farrahi, G. H ; Mahmoudi, A. H ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Shot peening is the most common surface treatment employed to enhance the fatigue performance of structural metallic materials and often carried out after other surface treatments. This paper mainly focuses on the effects of initial conditions of surface such as initial stress filed and hardness profile on shot peening residual stress field. The residual stress distribution induced by shot peening is obtained using Hertzian contact theory and elastic–plastic evaluation after yielding occurred during impingement and rebound of shots. Elastic plastic calculations are performed using different hardening models considering Bauschinger effect. The present model is able to predict redistribution... 

    Silver nano-islands on glass fibers using heat segregation method

    , Article Materials Chemistry and Physics ; Volume 113, Issue 1 , 2009 , Pages 63-66 ; 02540584 (ISSN) Sharifi, N ; Taghavinia, N ; Sharif University of Technology
    2009
    Abstract
    A new method for fabrication of silver nano-islands on glass fibers using a top-down process is introduced. A thin layer of silver chemically coated on the surface of the glass fibers evolves into silver islands by heat treatment. The effect of the concentration of the initial solution and the temperature were investigated. Segregation was more clearly observed for lower solution concentrations and higher temperatures. The temperature of 500 °C was found optimum where separated islands form. At higher temperatures, the coagulation and burial of silver islands occur. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and diffused reflectance spectroscopy (DRS) were... 

    Inhibitory effects of functionalized indium doped ZnO nanoparticles on algal growth for preservation of adobe mud and earthen-made artworks under humid conditions

    , Article International Biodeterioration and Biodegradation ; Volume 127 , Febraury , 2018 , Pages 209-216 ; 09648305 (ISSN) Shariati, M ; Mallakin, A ; Malekmohammady, F ; Khosravi Nejad, F ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    In this article, indium doped ZnO nanoparticles (alloy nanoparticles) were investigated as inhibitors against algae growth on adobe mud and earthen artworks for surface preservation from destruction caused by micro-organisms under humid conditions, through surface modification and activation run off. Nanoparticles (NPs) were fabricated by physical vapor deposition (PVD) growth mechanism. The fabricated NPs were approximately 20 nm in size. The Chlorella vulgaris and Scenedesmus quadricauda were tested by application of indium doped ZnO nanoparticles (In/ZnO NPs) as inhibitors. As concentrations of NPs increased, the negative impacts of NPs on the algal growth were enhanced and physical... 

    Direct growth of metal-organic frameworks thin film arrays on glassy carbon electrode based on rapid conversion step mediated by copper clusters and hydroxide nanotubes for fabrication of a high performance non-enzymatic glucose sensing platform

    , Article Biosensors and Bioelectronics ; Volume 112 , 2018 , Pages 100-107 ; 09565663 (ISSN) Shahrokhian, S ; Khaki Sanati, E ; Hosseini, H ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    The direct growth of self-supported metal-organic frameworks (MOFs) thin film can be considered as an effective strategy for fabrication of the advanced modified electrodes in sensors and biosensor applications. However, most of the fabricated MOFs-based sensors suffer from some drawbacks such as time consuming for synthesis of MOF and electrode making, need of a binder or an additive layer, need of expensive equipment and use of hazardous solvents. Here, a novel free-standing MOFs-based modified electrode was fabricated by the rapid direct growth of MOFs on the surface of the glassy carbon electrode (GCE). In this method, direct growth of MOFs was occurred by the formation of vertically...