Search for: silicones
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    Silicon morphology modelling during solidification process of A356 al alloy

    , Article International Journal of Cast Metals Research ; Volume 25, Issue 1 , 2012 , Pages 53-58 ; 13640461 (ISSN) Shabani, M. O ; Mazahery, A ; Davami, P ; Razavi, M ; Sharif University of Technology
    In this paper, an introduction of the finite element approach to microstructure based modelling is provided, and the primary and secondary dendrite arm spacings of A356 alloy in the solidification process are simulated. The simulated results of dendrite morphology and the experimental measurements are presented and compared with the investigations of other researchers, which confirmed the accuracy of this model in its ability to predict the dendrite arm spacing. Each of the length scales, including silicon rod diameter and spacing, is discussed in detail. Analytical equations are generated for the length scales and incorporated in the Sharif University Technology academic software for the... 

    Effect of Si antioxidant on the rate of oxidation of carbon in MgO-C refractory

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 24, Issue 4 , 2011 , Pages 357-366 ; 1728-144X (ISSN) Sadrnezhaad, S. K ; Bagheri, N ; Mahshid, S ; Sharif University of Technology
    Materials and Energy Research Center  2011
    Progressive conversion/shrinking core (PC-SC) models of constant-size cylinders were exploited to interpret the decarburization reactions of MgO-C-Si bricks heated up under blown air. Chemical adsorption/solid (or pore) diffusion mechanisms governed the reaction rate. With 5% silicon, chemical adsorption vanished at 1000 and 1100°C. The oxidation rate lowered then with temperature. This was due apparently to the blocking of the pore-end gorges by the voluminous compounds (like Forstrite). Arrhenius plots of the specific rates yielded the activation energies of the prevailing steps. Without Si antioxidant, three steps were appreciated having activation energies of 51.65 (for chemical... 

    DsReliM: Power-constrained reliability management in Dark-Silicon many-core chips under process variations

    , Article International Conference on Hardware/Software Codesign and System Synthesis, CODES+ISSS 2015, 4 October 2015 through 9 October 2015 ; Oct , 2015 , Pages 75-82 ; 9781467383219 (ISBN) Salehi, M ; Shafique, M ; Kriebel, F ; Rehman, S ; Tavana, M. K ; Ejlali, A ; Henkel, J ; ACM; IEEE ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Due to the tight power envelope, in the future technology nodes it is envisaged that not all cores in a many-core chip can be simultaneously powered-on (at full performance level). The power-gated cores are referred to as Dark Silicon. At the same time, growing reliability issues due to process variations and soft errors challenge the cost-effective deployment of future technology nodes. This paper presents a reliability management system for Dark Silicon chips (dsReliM) that optimizes for reliability of on-chip systems while jointly accounting for soft errors, process variations and the thermal design power (TDP) constraint. Towards the TDP-constrained reliability optimization, dsReliM... 

    A 60 GHz, 802.11ad/wigig-compliant transceiver for infrastructure and mobile applications in 130 nm sige bicmos

    , Article IEEE Journal of Solid-State Circuits ; Volume 50, Issue 10 , June , 2015 , Pages 2239-2255 ; 00189200 (ISSN) Tomkins, A ; Poon, A ; Juntunen, E ; El Gabaly, A ; Temkine, G ; To, Y. L ; Farnsworth, C ; Tabibiazar, A ; Fakharzadeh, M ; Jafarlou, S ; Abdellatif, A ; Tawfik, H ; Lynch, B ; Tazlauanu, M ; Glibbery, R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    A fully integrated 802.11ad/WiGig compliant 60 GHz transceiver is presented in a 130 nm SiGe BiCMOS technology. Encompassing an area of 2.3 mm × 2.16 mm = 4.97 mm2, the transceiver covers the entire 60 GHz band, from 57 to 66 GHz. Within this span, the RX NF, TX OP1dB, and PLL RMS jitter is better than 5.5 dB, + 13.5 dBm, and 7°, respectively. The transceiver is packaged in 1) a system-in-package substrate with industry standard WR-15 transition providing an approximate 1 dB insertion loss, and 2) a cost-effective 7 × 7 mm2 organic BGA package with integrated transmit and receive antennas providing 8 dBi gain. In system-level testing, the transceiver is fully compliant with all TX EVM and RX... 

    Dynamic strain aging of a commercial Al-Mg-Si-Cu alloy during equal channel angular extrusion process

    , Article Journal of Alloys and Compounds ; Volume 502, Issue 1 , July , 2010 , Pages 59-62 ; 09258388 (ISSN) Tabatabaei, N ; Karimi Taheri, A ; Vaseghi, M ; Sharif University of Technology
    In this research, the occurrence of dynamic strain aging (DSA) phenomenon during equal channel angular extrusion (ECAE) of a commercial air cooled Al-Mg-Si-Cu alloy is investigated. In order to detect the negative strain rate sensitivity behaviour associated with DSA, samples were ECAE-ed at various temperatures and strain rates. Subsequently, the extruded billets were subjected to mechanical and physical tests and it was found that at a certain ECAE temperature range there is a critical strain rate above which DSA occurs. The implication of the results to strengthening of dilute solid solutions is discussed  

    Silicon tetrachloride catalyzed aza-michael addition of amines to conjugated alkenes under solvent-free conditions

    , Article Synlett ; Issue 3 , 2010 , Pages 379-382 ; 09365214 (ISSN) Azizi, N ; Baghi, R ; Ghafuri, H ; Bolourtchian, M ; Hashemi, M ; Sharif University of Technology
    The efficient and very simple conjugate addition of aromatic and aliphatic amines to α,β-unsaturated carbonyl compounds under solvent-free conditions in the presence of catalytic amount of silicon tetrachloride is reported. The reaction of aryl and alkyl amines with different Michael acceptors gave the corresponding Michael adducts with simple catalyst and good to excellent yields  

    Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si

    , Article Sensors and Actuators, B: Chemical ; Volume 146, Issue 1 , 2010 , Pages 53-60 ; 09254005 (ISSN) Razi, F ; Iraji-Zad, A ; Rahimi, F ; Sharif University of Technology
    We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I-V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal-interface-semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100-40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration... 

    Digital holography based submicron thermometry

    , Article Optics Express ; Volume 24, Issue 25 , 2016 , Pages 28678-28685 ; 10944087 (ISSN) Moradi, A ; Akhlaghi, E. A ; Hajizedeh, F ; Seyed ReihaniReihani, S. N ; Sharif University of Technology
    OSA - The Optical Society  2016
    Here we introduce a phase-shifting digital holography-based method to determine the temperature profile around an irradiated (sub-)micron spherical bead. The method utilizes a Mach-Zehnder interferometer implemented into an open setup microscope. The results of irradiated gold spheres with diameter of 400 nm and also silver-coated micron-sized silica beads embedded in silicone oil are presented. We show that the applied method is able to accurately determine the surface temperature with accuracy of 1 °C. Our experimental results perfectly confirm the theoretical prediction of temperature profile around the irradiated bead  

    Recent advances in silicon nanowire biosensors: Synthesis methods, properties, and applications

    , Article Nanoscale Research Letters ; Volume 11, Issue 1 , 2016 ; 19317573 (ISSN) Namdari, P ; Daraee, H ; Eatemadi, A ; Sharif University of Technology
    Springer New York LLC 
    The application of silicon nanowire (SiNW) biosensor as a subtle, label-free, and electrical tool has been extensively demonstrated by several researchers over the past few decades. Human ability to delicately fabricate and control its chemical configuration, morphology, and arrangement either separately or in combination with other materials as lead to the development of a nanomaterial with specific and efficient electronic and catalytic properties useful in the fields of biological sciences and renewable energy. This review illuminates on the various synthetic methods of SiNW, with its optical and electrical properties that make them one of the most applicable nanomaterials in the field of... 

    Continuum models calibrated with atomistic simulations for the transverse vibrations of silicon nanowires

    , Article International Journal of Engineering Science ; Volume 100 , 2016 , Pages 8-24 ; 00207225 (ISSN) Nejat Pishkenari, H ; Afsharmanesh, B ; Tajaddodianfar, F ; Sharif University of Technology
    Elsevier Ltd  2016
    We have conducted Molecular Dynamics (MD) simulations with the Environment-Dependent Interatomic Potential (EDIP) to obtain the natural frequency of ultra-thin Silicon Nanowires (SiNWs) with various crystallographic structures, boundary conditions and dimensions. As expected, results show that the mechanical properties of SiNWs are size-/orientation-dependent. The observed phenomena are ascribed to the surface effects which become dominant due to the large surface-to-volume number of atoms at the investigated range of dimensions. Due to their accuracy, atomistic simulations are widely accepted for the investigations of such nano-scaled systems; however, they suffer from high computational... 

    Mechanical properties of Al–30Si–5Fe alloy using combination of rapid solidification and thixoforming processes

    , Article Metallography, Microstructure, and Analysis ; Volume 6, Issue 6 , 2017 , Pages 502-511 ; 21929262 (ISSN) Shafizadeh, M ; Aashuri, H ; Nikzad, S ; Ferasat, K ; Sharif University of Technology
    In this study, a combination of rapid solidification (melt-spinning) and semisolid forming (thixoforming) processes was used to refine the coarse microstructure of “as-cast” Al–30Si–5Fe alloy and improve its mechanical properties. Al–30Si–5Fe ribbons produced by the melt-spinning process were pulverized and subsequently consolidated at 300 °C in an argon atmosphere. Prepared specimens were thixoformed at temperatures ranging from 580 to 700 °C for various holding times. Some cast samples were also directly thixoformed as reference. In all thixoformed samples, microstructures were modified and needle-like intermetallic compounds as well as silicon particles in the as-cast part were changed... 

    Mechanism of Al-Si codeposition on In738LC through single-step diffusion process

    , Article International Journal of Surface Science and Engineering ; Volume 11, Issue 1 , 2017 , Pages 1-11 ; 1749785X (ISSN) Nikzad, S ; Abdi, M ; Rastegari, S ; Sharif University of Technology
    The out-of-pack cementation method was applied to coat the Nickel-based super alloy IN738LC with Si-modified aluminide. Different mixtures of the pack containing pure Al, Si, alumina powders as an inert filler, and NH4Cl as a halide salt activator were used for co-deposition at 950 and 1,050°C. The results showed although the amount of subhalide vapour pressures of Al and Si were equal at 1,050°C, Al atoms diffused only after Si atoms had been deposited. Before heat treatment, the coating thickness formed by the pack containing 2.3 wt.% Al was 6 μm more than that containing 3.5 wt.% Al. After heat treatment, thickening coatings formed within the pack containing 2.3 wt.% Al was less than that... 

    The potential impact of Fully Ceramic Microencapsulated (FCM) fuel on thermal hydraulic performance of SMART reactor

    , Article Nuclear Engineering and Design ; Volume 339 , 2018 , Pages 39-52 ; 00295493 (ISSN) Kamalpour, S ; Salehi, A. A ; Khalafi, H ; Mataji Kojouri, N ; Jahanfarnia, G ; Sharif University of Technology
    Elsevier Ltd  2018
    One of emerging advanced fuel materials for the next generations of the nuclear reactors is Fully Ceramic Microencapsulated (FCM) fuel. FCM fuel structure is comprised of TRISO particles dispersed randomly in a SiC matrix. In the present study, the thermal hydraulic performance of a SMART reactor is investigated and the results are compared with the case that conventional UO2 fuel is loaded into the core. At the beginning of the cycle, the reactor is simulated in normal operational and transient conditions. MCNPX 2.6 stochastic code is utilised to calculate neutronic parameters. COMSOL and RELAP5 codes are used for thermal hydraulic analysis. The reactor dynamics is simulated based on... 

    Frozen leg operation of a three-phase dual active bridge DC/DC converter at light loads

    , Article Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC ; Volume 2018-March , 18 April , 2018 , Pages 3385-3391 ; 9781538611807 (ISBN) Haghbin, S ; Blaabjerg, F ; Yazdani, F ; Bahman, A. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    A three-phase dual active bridge (DAB) converter is designed and constructed as the DC/DC stage of a 50 kW fast charger station. Recently introduced 300A SiC power modules and drivers are utilized in the converter to obtain a high efficiency. Each module has two interconnected switches with anti-parallel diodes resembling a converter leg. It is observed that the driver halts the module operation as a result of protective actions such as over-current, gate under-voltage, or gate overvoltage. In such case the module operates as a leg with two diodes until an external hardware signal resets the driver. The aim of this paper is to provide analysis, simulation and experiments for a three-phase... 

    A precipitation-hardening model for non-isothermal ageing of Al-Mg-Si alloys

    , Article Computational Materials Science ; Volume 45, Issue 2 , 2009 , Pages 385-387 ; 09270256 (ISSN) Yazdanmehr, M ; Bahrami, A ; Mousavi Anijdan, S. H ; Sharif University of Technology
    An age-hardening model has been developed to predict the evolution of the hardness of Al-Mg-Si alloys during non-isothermal ageing before peak age. The concurrent precipitation and dissolution have been considered in the structural model. Then the structural model has been combined with strengthening model to predict the precipitation-hardening behavior of the alloy AA6061. The results indicate that the developed model can be used as a predictive tool to model the mechanical properties evolution of Al-Mg-Si alloys during non-isothermal heat treatment. © 2008 Elsevier B.V. All rights reserved  

    SiC fines effects on the microstructure and properties of bauxite-based low-cement refractory castables

    , Article Ceramics International ; Volume 45, Issue 13 , 2019 , Pages 16338-16346 ; 02728842 (ISSN) Mavahebi, S ; Bavand vandchali, M ; Nemati, A ; Sharif University of Technology
    Elsevier Ltd  2019
    In the present paper, the effect of silicon carbide (SiC) fines was studied on the phase and microstructural properties of bauxite-based low-cement refractory castables (LCC) at different firing temperatures. XRD and SEM techniques were employed to evaluate phase and microstructure analysis, and physical/mechanical properties were measured according to standard methods. The results showed that the oxidation of SiC particles related to the oxygen partial pressure and active/passive oxidation behavior of SiC fines could markedly affect the microstructure and properties of bauxite-based LCC fired at high temperatures. Despite the negative influence of addition of SiC fines on cold mechanical... 

    A comparative study between friction stir processing and friction stir vibration processing to develop magnesium surface nanocomposites

    , Article International Journal of Minerals, Metallurgy and Materials ; Volume 27, Issue 8 , 2020 , Pages 1133-1146 Bagheri, B ; Abbasi, M ; Abdollahzadeh, A ; Kokabi, A. H ; Sharif University of Technology
    University of Science and Technology Beijing  2020
    Friction stir processing (FSP) can be used to improve surface composites. In this study, a modified method of FSP called friction stir vibration processing (FSVP) was applied to develop a surface composite on AZ91 magnesium alloy. In this technique, the workpiece is vibrated normal to the processing direction. The results illustrated that compared with the FSP method, the FSVP caused a better homogeneous distribution of SiC particles in the microstructure. The results also showed that matrix grains of friction stir vibration processed (FSV-processed) samples ((26.43 ± 2.00) µm) were finer than those of friction stir processed (FS-processed) specimens ((39.43 ± 2.00) µm). The results... 

    Integrated photonic neural network based on silicon metalines

    , Article Optics Express ; Volume 28, Issue 24 , 2020 , Pages 36668-36684 Zarei, S ; Marzban, M. R ; Khavasi, A ; Sharif University of Technology
    OSA - The Optical Society  2020
    An integrated photonic neural network is proposed based on on-chip cascaded one-dimensional (1D) metasurfaces. High-contrast transmitarray metasurfaces, termed as metalines in this paper, are defined sequentially in the silicon-on-insulator substrate with a distance much larger than the operation wavelength. Matrix-vector multiplications can be accomplished in parallel and with low energy consumption due to intrinsic parallelism and low-loss of silicon metalines. The proposed on-chip whole-passive fully-optical meta-neural-network is very compact and works at the speed of light, with very low energy consumption. Various complex functions that are performed by digital neural networks can be... 

    Effect of particle size on the microstructure of rapidly solidified Al-20Si-5Fe-2X (X = Cu, Ni, Cr) powder

    , Article Journal of Alloys and Compounds ; Volume 466, Issue 1-2 , 2008 , Pages 111-118 ; 09258388 (ISSN) Rajabi, M ; Simchi, A ; Vahidi, M ; Davami, P ; Sharif University of Technology
    The effects of particle size and alloying elements on the size and morphology of secondary/intermetallic phases in gas atomized Al-20Si-5Fe-2X (X = Cu, Ni, Cr) powders were studied. The microstructure composed of particle-like primary Si with average diameter of 0.5-2.7 μm, δ-Al4FeSi2 intermetallic compound containing small amount of dissolved alloying elements with the size of 1.4-7.7 μm, and fine Al-Si eutectic matrix with 0.25-0.4 μm spacing. As the powder particle size decreases, the primary silicon becomes finer while its morphology is not affected. For instance, 58-75% reduction in the size of primary silicon was observed when decreasing the average particle size from 89 to 18 μm. A... 

    Anodizing behavior and electrochemical evaluation of accumulative roll bonded Al and Al-SiC composite

    , Article Surface and Coatings Technology ; Volume 408 , 2021 ; 02578972 (ISSN) Ebadi, M ; Alishavandi, M ; Paydar, M. H ; Sharif University of Technology
    Elsevier B.V  2021
    Accumulative roll bonded (ARBed) AA1050 and Al-2 vol% SiCp (AMC) samples were anodized in an H2SO4 electrolyte to improve corrosion resistance. The SEM images revealed that the anodic oxide's morphology is significantly dependent on the microstructure of the ARBed bare samples, owing to high internal energy that accelerates Al consumption during anodizing process. Potentiodynamic polarization measurements and EIS evaluation showed that anodic oxide improves the corrosion resistance of both ARBed AA and AMC samples; however, the electrochemical behavior of the processed samples changed due to the formation of a complex oxide structure comprising of twisted pore channels and attack routes. ©...