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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... 

    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... 

    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)... 

    Surface treatment of perovskite layer with guanidinium iodide leads to enhanced moisture stability and improved efficiency of perovskite solar cells

    , Article Advanced Materials Interfaces ; Volume 7, Issue 14 , 2020 Chavan, R. D ; Prochowicz, D ; Tavakoli, M. M ; Yadav, P ; Hong, C. K ; Sharif University of Technology
    Wiley-VCH Verlag  2020
    Abstract
    Interfacial engineering between the perovskite and hole transport layers has emerged as an effective way to improve perovskite solar cell (PSC) performance. A variety of organic halide salts are developed to passivate the traps and enhance the charge carrier transport. Here, the use of guanidinium iodide (GuaI) for interfacial modification of mixed-cation (Cs)x(FA)1−xPbI3 perovskite films, which results in the formation of a low-dimensional δ-FAPbI3-like phase on the 3D perovskite surface, is reported. The presence of this thin layer facilitates charge transfer at interfaces and reduces charge carrier recombination pathways as evidenced by enhanced carrier lifetimes and favorable interfacial... 

    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... 

    The nanofibrous PAN-PANi scaffold as an efficient substrate for skeletal muscle differentiation using satellite cells

    , Article Bioprocess and Biosystems Engineering ; Volume 39, Issue 7 , 2016 , Pages 1163-1172 ; 16157591 (ISSN) Hosseinzadeh, S ; Mahmoudifard, M ; Mohamadyar Toupkanlou, F ; Dodel, M ; Hajarizadeh, A ; Adabi, M ; Soleimani, M ; Sharif University of Technology
    Springer Verlag 
    Abstract
    Among polymers, polyaniline (PANi) has been introduced as a good candidate for muscle regeneration due to high conductivity and also biocompatibility. Herein, for the first time, we report the use of electrospun nanofibrous membrane of PAN-PANi as efficient scaffold for muscle regeneration. The prepared PAN-PANi electrospun nanofibrous membrane was characterized by scanning electron microscopy (SEM), Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and tensile examination. The softer scaffolds of non-composite electrospun nanofibrous PAN govern a higher rate of cell growth in spite of lower differentiation value. On the other hand, PAN-PANi electrospun... 

    Hexagonal core–shell SiO2[–MOYI]Cl–]Ag nanoframeworks for efficient photodegradation of the environmental pollutants and pathogenic bacteria

    , Article Journal of Inorganic and Organometallic Polymers and Materials ; Volume 29, Issue 4 , 2019 , Pages 1314-1323 ; 15741443 (ISSN) Padervand, M ; Asgarpour, F ; Akbari, A ; Eftekhari Sis, B ; Lammel, G ; Sharif University of Technology
    Springer New York LLC  2019
    Abstract
    Hexagonal core–shell SiO2[–MOYI]Cl–]Ag nanoframeworks were synthesized via surface modification of hexagonal silica nanoparticles prepared from perlite (EP) as a cheap and abundant raw material. The prepared samples were well characterized by X-ray diffraction powder (XRD), energy dispersive X-ray (EDX), diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) specific surface area analysis, fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The XRD patterns confirmed that Ag and AgCl crystalline phases were successfully loaded on the surface. The TEM images were also implied that the... 

    Surface modification of polysulfone ultrafiltration membranes by free radical graft polymerization of acrylic acid using response surface methodology

    , Article Journal of Polymer Research ; Volume 26, Issue 9 , 2019 ; 10229760 (ISSN) Ganj, M ; Asadollahi, M ; Mousavi, S. A ; Bastani, D ; Aghaeifard, F ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    In this research, polysulfone (PSf) ultrafiltration (UF) membranes were prepared by a phase inversion method. Surface modification of the PSf membranes was carried out via grafting of acrylic acid as a hydrophilic monomer by free radical graft polymerization initiated by redox reaction. A central composite design (CCD) of response surface methodology (RSM) was applied to design the experiments. The process variables were acrylic acid concentration (CAA), redox system contact time (T1), and acrylic acid polymerization time (T2), while the contact angle (CA), pure water flux (PWF), and flux recovery ratio (FRR) were considered as the responses. Analysis of variance (ANOVA) demonstrated that... 

    Environmentally responsive surface-modified silica nanoparticles for enhanced oil recovery

    , Article Journal of Nanoparticle Research ; Volume 18, Issue 9 , 2016 ; 13880764 (ISSN) Behzadi, A ; Mohammadi, A ; Sharif University of Technology
    Springer Netherlands 
    Abstract
    Environmentally responsive surface-modified nanoparticles are colloidal nanoparticles coated with, at least, two physicochemically distinct surface groups. Recent advances in the synthesis and production of nanoparticles have enabled the production of environmentally responsive surface-modified nanoparticles with both hydrophilic and hydrophobic surface groups. These nanoparticles act like colloidal surfactants. In this paper, environmentally responsive surface-modified silica nanoparticles are synthesized and used for enhancement of oil recovery. For this purpose, silica nanoparticles are coated with polyethylene glycol chains as hydrophilic agent and propyl chains as hydrophobic agent at... 

    The investigation of laser shock peening effects on corrosion and hardness properties of ANSI 316L stainless steel

    , Article International Journal of Advanced Manufacturing Technology ; Volume 88, Issue 5-8 , 2017 , Pages 1557-1565 ; 02683768 (ISSN) Ebrahimi, M ; Amini, S ; Mahdavi, S. M ; Sharif University of Technology
    Springer London  2017
    Abstract
    Laser shock peening (LSP) is known as a post processing surface treatment which can improve the mechanical properties of some materials. Shock waves are generated by confining the laser-induced plasma to cause a large pressure shock wave over a significant surface area. In the present study, effects of LSP on the electrochemical corrosion and micro hardness properties of 316L stainless steel alloy were investigated by changing the laser parameters such as the laser spot size, the average number of impacts, and the laser intensity. Since laser parameters do not cover the desired region of LSP, we have to use the proper design of experiment method, in which the D-optimal design of MATLAB was... 

    Effect of oxidizing atmosphere on the surface of titanium dental implant material

    , Article Journal of Bionic Engineering ; Volume 16, Issue 6 , 2019 , Pages 1052-1060 ; 16726529 (ISSN) Khodaei, M ; Alizadeh, A ; Madaah Hosseini, H. R ; Sharif University of Technology
    Springer  2019
    Abstract
    Direct oxidation is a simple and effective method for titanium surface treatment. In this research, a titanium sample was directly oxidized at the high temperature in two different atmospheres, air and pure oxygen, to obtain better atmosphere for titanium surface treatment. The results of the Raman spectroscopy indicated that in both atmospheres, the rutile bioactive phase (TiO2) has been formed on the titanium surface. The results of X-ray diffraction (XRD) also revealed that the surface of oxygen-treated sample was composed of the rutile phase and titanium monoxide (TiO), while at the surface of the air-treated sample, the rutile phase and titanium dioxide had been formed. Further, the... 

    Oxidation behavior and electrical properties of de-siliconized aisi 430 alloy with mn1.5co1.5o4 coating for solid oxide fuel cell interconnect

    , Article Oxidation of Metals ; Volume 93, Issue 3-4 , 2020 , Pages 401-415 Bakhshi Zadeh, A ; Salmani, S ; Faghihi Sani, M. A ; Abdoli, H ; Jalili, N ; Sharif University of Technology
    Springer  2020
    Abstract
    Abstract: The effect of de-siliconization on the oxidation behavior of AISI 430 stainless steel used for solid oxide fuel cell interconnect application was investigated. De-siliconization treatment was conducted via heating steel parts in an H2 environment. The de-siliconized substrates were then coated with a Mn1.5Co1.5O4 spinel coating, using wet spray method. For comparison, a similar coating process was applied on the as-received AISI 430 stainless steel specimens. Oxidation kinetics of coated interconnects were evaluated at 700, 800 and 900 °C in air. Results showed that the de-siliconization surface treatment decreased oxidation rates, with kinetic rates (g2 cm−4 s−1) of 4.39 × 10−14... 

    Supramolecular polycaprolactone nanocomposite based on functionalized hydroxyapatite

    , Article Journal of Bioactive and Compatible Polymers ; Volume 27, Issue 5 , January , 2012 , Pages 467-480 ; 08839115 (ISSN) Mehmanchi, M ; Shokrollahi, P ; Atai, M ; Omidian, H ; Bagheri, R ; Sharif University of Technology
    SAGE  2012
    Abstract
    Arms bearing ureido-pyrimidinone functional groups with self-association capability (through quadruple hydrogen bonds) were successfully grafted onto hydroxyapatite nanoparticles. The supramolecularly modified nanoparticles (nHApUPy) exhibited enhanced colloidal stability compared to the original hydroxyapatite nanoparticles and were uniformly dispersed in supramolecular polycaprolactone in PCL(UPy)2/HApUPy nanocomposites at different filler loadings. The combined atomic force microscopy, mechanical, and rheological analyses confirmed a high degree of compatibility of HApUPy nanoparticles with the polymer matrix. The temperature dependence of the supramolecular structure in PCL(UPy)2/HApUPy... 

    TiO2/nanoporous silicon hybrid contact for heterojunction crystalline solar cell

    , Article RSC Advances ; Volume 6, Issue 60 , 2016 , Pages 55046-55053 ; 20462069 (ISSN) Ghorbani Shiraz, H ; Razi Astaraei, F ; Mohammadpour, R ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Abstract
    The conventional solar cell architectures include a p-n junction of c-Si sandwiched by rear and front contacts. The conventional approach features a complex as well as expensive procedure. Here, we propose a new architecture for p-n heterojunction solar cells prepared by a simple and cost-effective procedure. In this regard, (1) a silicon wafer underwent surface treatment through electrochemical anodization. To prepare a stick junction, (2) photoactive TiO2 nanoparticles were deposited over the porous layer by electrophoretic technique. Finally, (3) indium tin oxide (ITO) was sputtered. During the fabrication steps, we examined various anodization times ranging from 6 to 12 min to study the... 

    An easy method to modify PEDOT:PSS/perovskite interfaces for solar cells with efficiency exceeding 15%

    , Article RSC Advances ; Volume 6, Issue 70 , 2016 , Pages 65594-65599 ; 20462069 (ISSN) Shahbazi, S ; Tajabadi, F ; Shiu, H. S ; Sedighi, R ; Jokar, E ; Gholipour, S ; Taghavinia, N ; Afshar, S ; Diau, E. W. G ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Abstract
    Herein, we show that surface treatment of PEDOT:PSS films using propionic acid (PA) results in better device performance for the resulting CH3NH3PbI3 perovskite solar cells (PCE > 15%). N2 blow spreading of PA appears critical in enhanced performance. This weak acid treatment leads to no worse roughness, while providing larger perovskite grains  

    Increasing the interfacial adhesion in poly(methyl methacrylate)/carbon fibre composites by laser surface treatment

    , Article Polymers and Polymer Composites ; Volume 14, Issue 6 , 2006 , Pages 585-589 ; 09673911 (ISSN) Nematollahzadeh, A ; Mousavi, S. A. S ; Tilaki, R. M ; Frounchi, M ; Sharif University of Technology
    Rapra Technology Ltd  2006
    Abstract
    The impact strength of poly(methyl methacrylate)/caibon (long) fibre composites for denture prosthesis applications was improved by fibre surface treatment. The carbon fibre surfaces were modified by Nd:YAG laser irradiation at 1064 nm wavelength. Laser light intensity was adjusted at 100 mj per pulse that only changed the fibre surface roughness and did not lead to fibre rupture, as verified by scanning electron microscopy. Increased surface roughness of the fibres improved the adhesion of poly(methyl methacrylate) to the fibre surface. Adhesion between the fibres and poly(methyl methacrylate) was evaluated by a tear-off method and by scanning electron microscopy. The results also suggest... 

    Modelling of conventional and severe shot peening influence on properties of high carbon steel via artificial neural network

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 31, Issue 2 , 2018 , Pages 382-393 ; 1728144X (ISSN) Maleki, E ; Farrahi, G. H ; Sharif University of Technology
    Materials and Energy Research Center  2018
    Abstract
    Shot peening (SP), as one of the severe plastic deformation (SPD) methods is employed for surface modification of the engineering components by improving the metallurgical and mechanical properties. Furthermore, artificial neural network (ANN) has been widely used in different science and engineering problems for predicting and optimizing in the last decade. In the present study, effects of conventional shot peening (CSP) and severe shot peening (SSP) on properties of AISI 1060 high carbon steel were modelled and compared via ANN. In order to networks training, the back propagation (BP) error algorithm is developed and data of experimental tests results are employed. Experimental data...