Search for: glass
Total 394 records
Thermal considerations on the design and operation of lens ducts, Article Optics and Laser Technology ; Volume 35, Issue 6 , 2003 , Pages 415-423 ; 00303992 (ISSN) ; Sharif University of Technology
In this paper, heat effects due to powerful pump beam in the lens duct delivery system is investigated and subsequent thermal effects are described. Temperature raise in the device, thermal loading, and material considerations for the lens ducts fabrication are reported. For an absorbed intensity of 10 W/cm2 in a 4 cm-long lens duct, the temperature difference between the midpoint and its faces, for a lens duct made from borosilicate is 7.05°C, for sapphire 4.01°C, and for synthetic fused silica is the smallest value of 0.54°C. For a typical absorbed intensity of 1.4 W/cm2 in a 4 cm-long lens duct, with a steady-state time constant of 120 s, the fractional thermal loading is 1.98% for BK-7,...
Properties, crystallization mechanism and microstructure of lithium disilicate glass-ceramic, Article Journal of Non-Crystalline Solids ; Volume 356, Issue 4-5 , 2010 , Pages 208-214 ; 00223093 (ISSN) ; Nemati, A ; Shabanian, M ; Afshar, A ; Sharif University of Technology
In this study, lithium disilicate glass-ceramic in the TiO2-ZrO2-Li2O-CaO-Al2O3-SiO2 system was investigated for dentistry applications by incorporation of P2O5 and Nb2O5 as nucleation agent. The influence of the particles size (nano and submicron size) and nucleating agents on the crystalline phases, microstructure, crystallization mechanism and mechanical properties were investigated. Our data indicated that in ceramic glass with nano and submicron P2O5, the main crystalline phase was lithium disilicate. The results also showed that change of P2O5 particle's size had significant effect on the crystalline phases and microstructure. By replacement of submicron P2O5 with submicron Nb2O5,...
Comparing short–range and medium–range ordering in Cu–Zr and Ni–Zr metallic glasses – Correlation between structure and glass form ability, Article Journal of Non-Crystalline Solids ; Volume 499 , 2018 , Pages 227-236 ; 00223093 (ISSN) ; Tavakoli, R ; Foroughi, A ; Sharif University of Technology
Elsevier B.V 2018
According to recent studies, Cu–Zr and Ni–Zr binary alloying systems are very similar based on known glass-forming ability criteria, however, they exhibit significant difference in glass-forming ability in practice. In this work, local atomic structures of Cu–Zr and Ni–Zr metallic glasses are studied by molecular dynamics simulation to explain the source of mentioned difference. The total and partial distribution functions, coordination number and voronoi analysis are utilized to characterize the local atomic structures around Zr, Ni and Cu atoms. It was found that the local environment around Zr atoms is almost similar in both systems. The difference in the atomic structure in these systems...
Topological and chemical short-range order and their correlation with glass form ability of Mg-Zn metallic glasses: A molecular dynamics study, Article Computational Materials Science ; Volume 180 , 2020 ; Tavakoli, R ; Sharif University of Technology
Elsevier B.V 2020
Mg-based metallic glasses are promising materials for biodegradable implants. Understanding atomistic mechanism behind glass formation in these glasses plays a critical role in developing them for future applications. In the present work, we perform a set of molecular dynamics simulations to study structural origin behind glass form ability of Mg-based Mg-Zn metallic glasses at a wide range of compositions. Pair distribution function, Voronoi tessellation and dynamical analysis were adopted to characterize local structures in these glasses. Structural analysis was performed considering both topological and chemical short-range orders. It was found that structure of Mg-Zn metallic glasses...
Effects of nucleation agents on the preparation of transparent glass-ceramics, Article Journal of the European Ceramic Society ; Volume 32, Issue 11 , August , 2012 , Pages 2989-2994 ; 09552219 (ISSN) ; Nemati, A ; Baghshahi, S ; Sharif University of Technology
Formation of transparent glass-ceramic in the system MgO-SiO 2-Al 2O 3-K 2O-B 2O 3-F with and without addition of LiF and NaF has been investigated. Crystallization of glass-sample was conducted by controlled thermal heat-treatment, at determined nucleation and crystallization temperatures. In this regard, the effects of addition of LiF and NaF were investigated on the crystallization behavior and transparency of the samples. Low transmission (less than 80% at 600. nm) was observed in the basic composition (K).The addition of NaF and LiF caused more intense phase separation in the system. The results indicated that the glass-ceramic can remain transparent if fine grains with nano size are...
Preparation and characterisation of diopside-based glass-ceramic foams, Article Ceramics International ; Volume 38, Issue 3 , 2012 , Pages 2005-2010 ; 02728842 (ISSN) ; Nemati, A ; Eftekhari Yekta, B ; Alizadeh, P ; Sharif University of Technology
Foaming and crystallisation behaviours of compacted glass powders based on a diopside glass-ceramic composition were investigated using the sintering route. The foaming agent was 2 wt.% SiC particles. The effect of PbO on the foaming ability of glasses was investigated. The results showed that the addition of PbO not only improved the foaming ability, by improving the wettability of the glass-SiC particles but also increased the crystallisation temperature and widened the temperature interval between the dilatometric softening point and the onset of crystallisation. The glass-SiC wetting angle was decreased from 85°for the lead-free glass, to 55°for the glass that contains 15 wt.% PbO
Simultaneous evaluation of magnesia and silica contents’ effect on in-vitro bioactivity of novel bioglasses in the SiO2-CaO-MgO system, Article Transactions of the Indian Ceramic Society ; Volume 75, Issue 1 , 2016 , Pages 7-11 ; 0371750X (ISSN) ; Mahdieh, Z ; Maddahi, V ; Shokrgozar, M. A ; Mehrjoo, M ; Sharif University of Technology
Taylor and Francis Ltd 2016
In this study, bioglasses in SiO2-CaO-MgO system were synthesized through sol-gel method and the effect of silica and magnesia contents on in-vitro bioactivity of the bioglasses were investigated. XRD patterns showed an amorphous structure after heat treatment at 600Â°C for 2 h for all glasses and also indicated that after immersion in SBF, apatite particles precipitated on glass surfaces and the rate of apatite formation decreased with increasing Mg/Ca ratio. On the other hand, the apatite formation rate was enhanced with increasing the silica content. Furthermore, magnesia contents increased the compressive strength of the samples. According to SEM, higher Mg/Ca ratio led to increase in...
Hyperion: a wearable augmented reality system for text extraction and manipulation in the air, Article Proceedings of the 8th ACM Multimedia Systems Conference, MMSys 2017, 20 June 2017 through 23 June 2017 ; 2017 , Pages 284-295 ; 9781450350020 (ISBN) ; Bermejo, C ; Huang, Z ; Butabayeva, A ; Zheng, R ; Golkarifard, M ; Hui, P ; Sharif University of Technology
We develop Hyperion a Wearable Augmented Reality (WAR) system based on Google Glass to access text information in the ambient environment. Hyperion is able to retrieve text content from users' current view and deliver the content to them in different ways according to their context.We design four work modalities for different situations that mobile users encounter in their daily activities. In addition, user interaction interfaces are provided to adapt to different application scenarios. Although Google Glass may be constrained by its poor computational capabilities and its limited battery capacity, we utilize code-level offloading to companion mobile devices to improve the runtime...
Serrated flow during inhomogeneous bending deformation of bulk metallic glasses: From self-organized critical to chaotic dynamics, Article Journal of Non-Crystalline Solids ; Volume 505 , 2019 , Pages 62-71 ; 00223093 (ISSN) ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
Elsevier B.V 2019
In this research, the dynamic behavior of serrated flows observed in the flexural stress-deflection curves during three-point bending (3 PB) tests on Zr-, Ti- and La-based bulk metallic glasses (BMGs) is statistically analyzed. Furthermore, the effect of strain rate on the serrations is studied. Based on the ductility of alloy, two distinct types of dynamics are detected. For more ductile alloys (Zr- and Ti-based BMGs) the stress drop magnitude of serrations obeys a power-law distribution of shear avalanches, which is an indicator of the self-organized critical (SOC) state in dynamics. In this case, the size of avalanches has no characteristic scale. In contrast, the size of serrations...
On the origin of intermediate temperature brittleness in La-based bulk metallic glasses, Article Journal of Alloys and Compounds ; Volume 770 , 2019 , Pages 535-539 ; 09258388 (ISSN) ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
Elsevier Ltd 2019
The effect of strain rate on the ductility of a La-based bulk metallic glass (BMG) over a wide temperature range, and the correlation between ductility and relaxation processes within this alloy are investigated in the present work. The three point bending test and dynamic mechanical analysis are employed to study these phenomena. It is found that the activation energies of the nearly constant loss (NCL) relaxation and intermediate temperature brittleness are almost identical. This observation reveals that the NCL relaxation, as a locally confined or caged dynamics, contributes as the main source of intermediate temperature brittleness in La-based BMGs. © 2018 Elsevier B.V
Universal correlation between the thermodynamic potentials and some physical quantities of metallic glasses as a function of cooling rate during molecular dynamics simulation, Article Journal of Non-Crystalline Solids ; Volume 536 , 2020 ; Tavakoli, R ; Sharif University of Technology
Elsevier B.V 2020
The existence of universal semi-log linear relation between potential energy and cooling rate during the molecular dynamics simulations of metallic glasses for Cu-Zr system was formerly reported. For this purpose, different classes of metallic glasses are considered and the validity of this correlation is studied. It is shown that it holds for other thermodynamics potentials and some physical quantities like density and Wendt and Abraham parameter, too. This observation enables us to economically construct atomic scale metallic glass structures equivalent to very low cooling rates, more consistent to experimental works, not accessible using classic molecular simulations. © 2020 Elsevier B.V
Temperature dependence of serrated flow, strain-rate sensitivity and activation volume in a Ti-based bulk metallic glass, Article Journal of Non-Crystalline Solids ; Volume 553 , 2021 ; 00223093 (ISSN) ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
Elsevier B. V 2021
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...
Enhancement of bond characteristics of ribbed-surface GFRP bars with concrete by using carbon fiber mat anchorage, Article Construction and Building Materials ; Volume 134 , 2017 , Pages 507-519 ; 09500618 (ISSN) ; Bazli, M ; Vatani Oskouei, A. V ; Sharif University of Technology
The bond of fiber-reinforced polymer (FRP) reinforcement is expected to be more sensitive to the strength and geometry of the ribs than conventional steel reinforcement. In this study, the effect of carbon fiber mat anchorage on the pullout behavior of glass fiber-reinforced polymer (GFRP) bars embedded in normal concrete is studied. The studied parameters were the compressive strength of the concrete (16 MPa, 24 MPa, and 37 MPa), and, the length and diameter of the anchorage. In total, 15 variables were studied. Ribbed GFRP bars with 10 mm nominal diameter and 80 mm embedment length, ld, (which is 8 times the bar diameter) were considered. Based on the results for concretes with the...
Comparing Glass Formability of Cu-Zr and Ni-Zr Systems by Molecular Dynamics Simulation, M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rohollah
Metallic glasses (MG) are a group of materials that have unique properties such as high yielding strength and high elastic deformation. Because of limitation in the production of these materials, a few industrial materials of MG have been made so far. A few of binary alloys, like binary alloys made of Cu-Zr, have high Glass Forming Ability (GFA) in medium cooling rates. Between two binary systems of Cu-Zr and Ni-Zr, although constituent elements in aspect of atomic radius, electronic structure, physical properties, phase diagrams and intermetallic compounds are so similar to each other, but GFA between them are very different. For example, in Cu-Zr system there are compounds, such as...
Study of Microstructure and Mechanical Properties of PA6/GF/GB Hybrid Composites, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza
Polyamide 6 is one of the well-known and oldest engineering thermoplastics, which has many uses in the transportation, automotive, apparel and sports industries due to its high strength, high corrosion resistance and high service temperatures. Cite gears, radiator tank, cylinder head cap and fuel rails can be mentioned as Polyamide 6 applications in the automotive industry. Glass fibers are used as reinforcement in PA6 media in order to enhance mechanical properties like tensile and impact strength. Even though the glass fiber improves the mechanical properties of the components produced from fiber-reinforced composites, it increases the anisotropy properties of the material and making it...
Investigation of Pb/PbS a positive Schottky junction formed on conductive glass in contact with alkaline solution, Article Journal of Applied Physics ; Vol. 116, issue. 3 , July , 2014 ; ISSN: 00218979 ; Jafarian, M ; Gobal, F ; Mahjani, M. G ; Miandari, S ; Sharif University of Technology
PbS on Pb thin film (Pb/PbS) was deposited on conductive glass (CG) substrate (CG/Pb/PbS) using electrochemical techniques to investigate the Schottky junction in solution. The CG/Pb/PbS electrode was investigated by different techniques based on thermionic emission theory. Electrochemical cell consisted of the CG/Pb/PbS as a working electrode in an alkaline solution showed character of the Schottky junction. Reduction and oxidation of H2O on the CG/Pb/PbS electrode were enhanced under illumination. Water photo splitting is the main process. Study of linear sweep voltammetry at around open circuit potential (OCP) allowed proposing a model based on the Schottky junction which is charged at...
Role of MgF2 on properties of glass-ceramics, Article Bulletin of Materials Science ; Volume 35, Issue 5 , October , 2012 , Pages 853-858 ; 02504707 (ISSN) ; Nemati, A ; Sharif University of Technology
Formation of machinable glass-ceramic in the system MgO-SiO 2-Al2O3-K2O-B2O 3-F with and without addition of MgF2 has been investigated. Crystallization of glass sample was done by controlled thermal heat treatment at nucleation and crystallization temperatures. The results showed that MgF2 in high concentration had a synergistic effect and enhanced the formation of interlockedmica crystals. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses were changed in the range of 235-405 kJ/mol, while the crystallization activation energies of samples with addition of MgF2 were changed in the range of 548-752 kJ/mol
Generation and collapse of bubbles in lead silicate glass, Article Glass Physics and Chemistry ; Volume 41, Issue 3 , May , 2015 , Pages 307-315 ; 10876596 (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
Maik Nauka Publishing / Springer SBM 2015
Presence of bubbles affects quality of the lead silicate glass (LSG) samples. This paper presents the most recent results obtained on formation and collapse of bubbles in LSG melts. Main sources of the bubbles are dissolved gases and redox reactions. A foamy layer full of bubbles rapidly forms at top of the molten phase. Effect of viscosity and density of the melt on content and ascension rate of the bubbles are investigated. Number and mean diameter of the bubbles and thickness of the top bubbly layer are calculated from gas volume measurements and image analysis via J software
Effects of substrate material and annealing temperature on morphology of zinc oxide films, Article Materials Science and Technology ; Volume 22, Issue 3 , 2006 , Pages 308-314 ; 02670836 (ISSN) ; Sadrnezhaad, S. K ; Sharif University of Technology
A two stage chemical deposition (TSCD) technique is used to produce ZnO films on quartz glass (QG), soda lime glass (SLG) and high purity alumina (HPA) from an aqueous solution of zinc complex. The effects of the substrate material on the chemical composition and morphology of the deposited layer are investigated. The effects of different annealing temperatures (180, 300, 500 and 800°C) on the morphology and orientation of the ZnO crystallites are also determined. X-ray diffraction diffractograms show that above 300°C, the intensity of (002) peak considerably decreases with increasing temperature. Results indicate that changing the substrate from QG to SLG does not significantly influence...
Influence of coloring voltage and thickness on electrochromical properties of e-beam eaporated W O3 thin films, Article Journal of the Electrochemical Society ; Volume 153, Issue 2 , 2006 , Pages E11-E16 ; 00134651 (ISSN) ; Akhavan, O ; Moshfegh, A. Z ; Sharif University of Technology
In this investigation, the effect of coloring voltage and thickness on optical and also electrochromical properties of W O3 thin films has been studied. The W O3 thin films were grown on glass and indium tin oxide coated conducting glass substrates by e-beam evaporation at different thicknesses of 200, 400, and 700 nm. Optical properties of the deposited samples were characterized in the ultraviolet-visible range (300-1100 nm). The optical bandgap energy of the W O3 was obtained in a range of 3.3-3.5 eV showing its increase by decreasing the film thickness. The refractive index of the W O3 films was measured around 2 in the visible range. Surface chemical states of the films were studied by...