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Total 394 records
Bioglass Coating on 316L Stainless Steel, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah
Bioactive glasses are able to bond to soft and hard tissues in living body and their application as coating on metallic implants like 316L stainless steel has two important effects: (1) intimate link between bone and materials and (2) corrosion protection of metallic implant in body fluid and protection from tissues in front of corrosion products. Therefore, in this research, 45S5 bioactive glass prepared via sol- gel method was dip coated on 316L stainless steel substrates and its characteristics was investigated.Results of phase analysis showed that by sintering 45S5 bioglass at 600 ˚C for 5 h, an amorph sample with small amount of Na2Ca2Si3O9 was obtained. So, the bioglass coated samples...
Computer Simulation of Ultrasonic Waves in Cybernetic Glasses in Order to Increasing Spatial Resolution of Blinds, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad
Eyesight is one of the most important tools for humans to communicate with environment and consequently, blindness or poor eyesight results in unsatisfactory effect on life quality. Owing to the importance of the sense and to assist to the patients, this thesis aims to design and assemble cybernetic glasses using ultrasound waves. To this end, firstly, the notion of waves focusing on ultrasound waves is described and reactions of human hearing system to the waves are studied. Then, the transducers as a key device are introduced. Afterward, bat sense system to communicate with environment which is based ultrasound waves is described. Next, attenuation effects on ultrasound wave pressures are...
Experimental and Analytical Investigation of Elastic-Plastic Behavior of Glass Fiber Reinforced Polymer Composites, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza ; Asghari, Mohsen
In this thesis, we aim to study the elastic-plastic behavior of short fiber reinforced composites experimentally and analytically. The experimental investigation is applied to glass fiber-polypropylene composites (PP/GF). The samples are produced by injection process with maximum temperature of 190C. Fibers are randomly oriented in this procedure of fabrication. The samples are tested in tension, and the mechanical strength is measured by changes in fiber content. The Young's modulus is also investigated in these experiments.Also in this thesis, an analytical model for calculation of Young’s modulus of fiber reinforced composite materials is proposed. In this analysis a displacement field is...
Thermally induced failure mechanism transition and its correlation with short-range order evolution in metallic glasses, Article Extreme Mechanics Letters ; Volume 9 , 2016 , Pages 215-225 ; 23524316 (ISSN) ; Tavakoli, R ; Srolovitz, D. J ; Zhang, Y. W ; Sharif University of Technology
The effect of temperature on the short-range order (SRO) structures, deformation mechanisms and failure modes of metallic glasses (MGs) is of fundamental importance for their practical applications. However, due to lack of direct structural information at the atomistic level from experiments and the absence of previous molecular dynamics (MD) simulations to reproduce experimental observations over a wide range of temperature, this issue has not been well understood. Here, by carefully constructing the atomistic models of Cu64Zr36 and Fe80W20 MGs, we are able to reproduce the major deformation modes observed experimentally, i.e. single shear banding (SB) at low temperatures, multiple...
Effect of the strain rate on the intermediate temperature brittleness in Zr-based bulk metallic glasses, Article Journal of Non-Crystalline Solids ; Volume 475 , 2017 , Pages 172-178 ; 00223093 (ISSN) ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
In this work, the effect of strain rate on the ductility, intermediate temperature brittleness and fracture surface of Zr-based BMG over a wide range of temperatures from 0.1 Tg to near Tg, has been systematically investigated. The results showed two remarkable ductile to brittle transition at low cryogenic and intermediate temperatures. At low temperatures, below 0.4 Tg, the activation of diffusion mediated phenomena is negligible and the combined effects of strain rate and temperature contribute to the plasticity of material by changing the STZ volume, hence the possibility of forming multiple shear bands. At the temperature range from 0.4 Tg to the temperature at which the intermediate...
Effects of Fe2O3 content on ionic conductivity of Li2O-TiO2-P2O5 glasses and glass-ceramics, Article Materials Chemistry and Physics ; Volume 190 , 2017 , Pages 8-16 ; 02540584 (ISSN) ; Nemati, A ; Eftekhari Yekta, B ; Banijamali, S ; Sharif University of Technology
Elsevier Ltd 2017
In this study, Li2O-TiO2-P2O5-x(Fe2O3) (x = 0, 2.5, 5 and 7.5 weight part) glass and glass-ceramics were synthesized through conventional melt-quenching method and subsequently heat treatment. Glass samples were studied by UV–visible spectroscopy and crystallized samples were characterized by differential thermal analysis, X-ray diffractometry and field emission scanning electron microscopy. Besides, electrical properties were examined according to the electrochemical impedance spectroscopy techniques. Experimental optical spectra of the Fe2O3-doped glasses revealed strong UV absorption band in the range of 330–370 nm, which were attributed to the presence of Fe3+ ions. The major crystalline...
Recent advancements in bulk metallic glasses and their applications: A review, Article Critical Reviews in Solid State and Materials Sciences ; Volume 43, Issue 3 , 2018 , Pages 233-268 ; 10408436 (ISSN) ; Nemati, A ; Rahman, Z.U ; Shah, U. H ; Asgar, H ; Haider, W ; Sharif University of Technology
Taylor and Francis Inc 2018
Bulk metallic glasses (BMGs), that display extraordinary properties of high strength, corrosion resistance, polymer-like formability, and excellent magnetic properties, are emerging as modern quintessential engineering materials. BMGs have garnered significant research enthusiasm owing to their tremendous technological and scientific standing. In this article, the recent advancements in the field of BMGs and their applications are put in a nutshell. Novel state-of-the-art production routes and nano/microimprinting strategies with salient features capable of circumventing the processing related complexities as well as accelerating modern developments, are briefly summarized. Heterogeneous BMG...
Chemical corrosion and gamma-ray attenuation properties of Zr and Ti containing lead silicate glasses, Article Journal of Nuclear Materials ; Volume 385, Issue 3 , 2009 , Pages 527-532 ; 00223115 (ISSN) ; Raisali, G ; Sadrnezhaad, K ; Alipour, A ; Sharif University of Technology
Lead silicate glasses (LSGs) have high gamma-ray attenuation but low chemical durability properties. In this work, LSGs with (55.5-68.5 wt%) PbO content containing ZrO2 and TiO2 additions were produced. The chemical corrosion of various produced LSGs in 0.5 N HNO3 aqueous solution and determination of their gamma-ray attenuation coefficients for 60Co and 137Cs sources were investigated. The weight loss measurements, the SEM micrographs, the EDS analysis of the sample surfaces and the ICP analysis of solution were used to characterize the dissolution process. The effects of PbO content, ZrO2 and TiO2 additives on chemical corrosion, and also the effect of PbO on gamma-ray attenuation...
Effect of utilizing glass fiber-reinforced polymer on exural strengthening of rc arches, Article Scientia Iranica ; Volume 26, Issue 4A , 2019 , Pages 2299-2309 ; 10263098 (ISSN) ; Khaloo, A. R ; Shekarchi, M ; Kazemian, A ; Sharif University of Technology
Sharif University of Technology 2019
An experimental study of the. flexural behavior of Reinforced-Concrete (RC) arches strengthened with Glass Fiber-Reinforced Polymer (GFRP) layers was performed. A total of 36 specimens including 3 un-strengthenod (control) and 33 strengthened RC arches were tested under centrally concentrated point load. The variables of this study were steel reinforcement ratio, number of GFRP layers, and location and arrangement of GFRP layers. Failure mode, load-displacement response of specimens, crack propagation patterns, and GFRP debonding were examined. The extrados strengthening method was shown to Ix1 more effective than the intrados strengthening one in improving the failure load and rigidity of...
The fabrication and characterization of bioactive Akermanite/Octacalcium phosphate glass-ceramic scaffolds produced via PDC method, Article Ceramics International ; 2020 ; Paryab, A ; Khalilifard, R ; Anousheh, M ; Malek Khachatourian, A ; Sharif University of Technology
Elsevier Ltd 2020
In the present study, a bioactive silicate-phosphate glass-ceramic scaffold was fabricated via the polymer-derived ceramics (PDC) method. K2HPO4 phosphate salt was used as the P2O5 precursor in this method. The effect of K2HPO4 wt% and heat treatment temperatures (900–1100 °C) was evaluated. It was observed that although increasing the wt% of K2HPO4 led to the formation of scaffolds with higher densities and strengths, it could also increase the formation of the calcium phase, which could result in improper release behavior of scaffolds. On the other hand, higher heat treatment temperatures enhanced the strength of the scaffolds but eliminated the bioactive octacalcium phosphate (OCP) phase....
Temperature dependence of serrated flow, strain-rate sensitivity and activation volume in a Ti-based bulk metallic glass, Article Journal of Non-Crystalline Solids ; February , 2020 ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
Elsevier B.V 2020
In this study, the influence of temperature on serrated flow behavior, strain rate sensitivity (SRS) and effective activation volume in a Ti-based bulk metallic glass (BMG) bent at different strain rates has been investigated. Results reveal that the fundamental origin of shear deformation is related to the time-dependent structural relaxations, which occur during deformation at special temperatures and strain rates. Furthermore, the localized structural relaxation processes at intermediate temperatures cause an inelastic shuffling within cages and mitigate the activation of STZs. The main reason of negative SRS at intermediate temperatures is due to the insufficient time for structural...
Energy-landscape networks of spin glasses, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 77, Issue 3 , 2008 ; 15393755 (ISSN) ; Seyed Allaei, H ; Ejtehadi, M. R ; Sharif University of Technology
We have studied the topology of the energy landscape of a spin-glass model and the effect of frustration on it by looking at the connectivity and disconnectivity graphs of the inherent structure. The connectivity network shows the adjacency of energy minima whereas the disconnectivity network tells us about the heights of the energy barriers. Both graphs are constructed by the exact enumeration of a two-dimensional square lattice of a frustrated spin glass with nearest-neighbor interactions up to the size of 27 spins. The enumeration of the energy-landscape minima as well as the analytical mean-field approximation show that these minima have a Gaussian distribution, and the connectivity...
Investigation into the effect of substrate material on microstructure and optical properties of thin films deposited via magnetron sputtering technique, Article Ceramics International ; 2021 ; 02728842 (ISSN) ; Nemati, A ; Hadi, I ; Mirdamadi, Sh ; Sharif University of Technology
Elsevier Ltd 2021
This study aims at investigating the effect of the substrate material on growth mechanism and also microstructure of Ta2O5 thin films. For this purpose, atomic force microscopy, scanning electron microscopy, and interferometry analyses were implemented to reveal the influence of silicon wafer and amorphous BK7 glass substrates on the nucleation and growth mechanisms of Ta2O5 thin films deposited via the radio frequency magnetron sputtering technique. Results indicated that those films with finer morphologies had relatively higher nucleation densities. Compared with BK7 glass substrate, crystals formed on the silicon wafer were shown to be finer and had lower mean areas in more nucleation...
The effect of Ag incorporation on the characteristics of the polymer derived bioactive silicate phosphate glass-ceramic scaffolds, Article Boletin de la Sociedad Espanola de Ceramica y Vidrio ; 2021 ; 03663175 (ISSN) ; Godary, T ; Khalilifard, R ; Malek Khachatourian, A ; Abdollahi, F ; Abdollahi, S ; Sharif University of Technology
Sociedad Espanola de Ceramica y Vidrio 2021
In the bone tissue engineering field (BTE), it is of significant importance to develop bioactive multifunctional scaffolds with enhanced osteoconductivity, osteoinductivity, and antibacterial properties required for lost bone tissue regeneration. In this work, a bioactive glass-ceramic scaffold was manufactured via a novel polymer-derived ceramics (PDC) manufacturing method. To gain antibacterial properties, the silver ions were incorporated in controlled amount along with other precursors in the PDC processing stage. Microstructural and structural properties of the fabricated silicate-phosphate glass-ceramic scaffold were evaluated by scanning electron microscopy (SEM) equipped with energy...
The effects of SiO 2 and K 2O on glass forming ability and structure of CaOTiO 2P 2O 5 glass system, Article Ceramics International ; Volume 38, Issue 4 , 2012 , Pages 3281-3290 ; 02728842 (ISSN) ; Nemati, A ; Eftekhari Yekta, B ; Hamnabard, Z ; Sharif University of Technology
The effects of SiO 2 and K 2O were investigated on the glass forming ability (GFA) and structural characteristics of CaOTiO 2P 2O 5 system. Differential thermal analyzer (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR and 31P magic angle spinning NMR methods were applied for characterizations of the system. Unwanted crystallization in the initial three components base glass composition was observed by adding SiO 2 and crystalline phases such as TiP 2O 7, rutile (TiO 2) and cristobalite (SiO 2) were formed in it. The results showed that K 2O prevents crystallization of glasses and promotes the formation of glass. FT-IR and X-ray diffraction showed that the addition...
Synthesis and characterization of diopside glass-ceramic matrix composite reinforced with aluminum titanate, Article Ceramics International ; Volume 35, Issue 4 , 2009 , Pages 1447-1452 ; 02728842 (ISSN) ; Alizadeh, P ; Eftekhari Yekta, B ; Molaie, F ; Ghafoorian, N ; Montazerian, M ; Sharif University of Technology
Glass-ceramic composites in the SiO2-CaO-MgO-(Na2O) system, reinforced with 5, 10 and 20 wt.% aluminum titanate were synthesized by pressureless sintering. Optimum sintering temperatures with maximum relative density were determined for each composition. The composites were fired above the crystallization peak temperature of glass-ceramic. Mechanical properties of glass-ceramic and sintered composites, such as fracture toughness, flexural strength and Vickers microhardness, were investigated. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the composite containing 10...
Topologic Properties Of The Energy Landscape Network In Frustrated Systems, M.Sc. Thesis Sharif University of Technology ; Ejtehadi, Mohammad Reza
The study of Energy Landscape of physical systems has a key role in complex problems. In this project we have enumerated the energy landscape of a finite squared lattice spin glass with nearest neighbored interactions to study its behavior. We choose the coupling constants of this spin glass system with Heb rule. According to this rule the coupling constants are chosen in a way to make specific patterns of spin configuration as a local minimum. We have studied these spin glasses with different number of patterns. In our computation we saw a significant difference between spin glasses with odd and even number of patterns. We addressed this behavior to properties of coupling constant...
Molecular Dynamics Study of Tungsten and Iron Addition on the Glass Formability of Cobalt-based Electrodeposited Coatings, M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rouhollah
Recent research suggests that the electrochemical deposition of cobalt-based binary alloys, such as cobalt-tungsten and cobalt-iron, can lead to the formation of amorphous structures in the coatings. Theoretical studies suggest that these structures are equivalent to structures created by the melt cooling of the alloy at speeds of about 〖10〗^10 Kelvin per second. The formation of a glass phase can significantly increase the abrasion resistance and corrosion resistance of these coatings. Empirical studies show that the ability of the glass to become glassy, or more precisely, the transition from crystalline to amorphous, is largely a function of the chemical composition. Simulation of...
Synthesis of Silica Nanosheets Using Droplet-based Microfluidics, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Aliasghar
The main purpose of this project is synthesis of the silica nano-sheets by means of microfluidic techniques. Continuous process, precise control of reaction condition, and higher production rate can be considered as main pros of silica nano-sheets synthesized by microfluidic platforms. General method can be explain as follow: first two oleic and aqueous phase are injected to the microfluidic system, then oleic phase breaks down in aqueous phase drop-wisely and by performing sol-gel reaction on the oil-water interface a silica crust is made on oil droplets. Eventually, oil droplets are left the system and broken down and silica nano-sheets are made. FESEM and microscopic images of...
Nano composite coating based on cellulose nanofibers/carbon nanoparticles: application to voltammetric determination of clonazepam, Article Journal of Solid State Electrochemistry ; Vol. 19, issue. 1 , 2014 , p. 251-260 ; Balotf, H ; Ghalkhani, M ; Sharif University of Technology
A novel electrochemical sensor for clonazepam (CLNP) was fabricated based on immobilizing cellulose nanofibers/carbon nanoparticles (CNFs/CNPs) nanocomposite on glassy carbon electrode (CNFs/CNPs/GCE). The combination of CNFs and CNPs produced a novel kind of structurally uniform and electro-analytically active nanocomposite. The surface morphology of CNFs/CNPs layer deposited onto glassy carbon electrode was characterized by scanning electron microscopy. The results of the voltammetric investigations showed a considerable enhancement in the cathodic peak current of CLNP (up to 60 times) on the surface of CNFs/CNPs/GCE relative to the bare GCE. Under the optimal conditions, the modified...