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    Design and modeling of a semiconductor laser by employing silicon carbide polymers (6H-SiC, 3C-SiC and 4H-SiC)

    , Article Asian Journal of Chemistry ; Volume 24, Issue 5 , May , 2012 , Pages 2177-2179 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    We present an edge emitting laser structure employing silicon carbide polymers only. In this structure, 3C-SiC well embedded in 6H-SiC barriers are used as the active region, which is sandwiched between the 6H-SiC mirror at the top and bottom of structure. The basic design goal is to use only silicon carbide polymers and decrease the threshold current and stable optical wavelength of the lasers with silicon carbide polymers. This paper provides key results of the device characteristics, including the light power versus electrical current and the optical wavelength versus current  

    Analysis and design of semiconductor laser with silicon carbide polymers (6H-SiC and 3C-SiC)

    , Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 7 , 2011 , Pages 1060-1063 ; 19918178 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    In the present work, a new structure of the strained quantum-well (QW) laser diode is designed and simulated. In this structure, the active region consists of tow 6H-SiC barrier and 3C-SiC quantum well (QW)which is sandwiched between two layers of 6H-SiC that can be interpreted in terms of a type-II heterostructure character and a built-in electric field due to the pyroel ectricity of 6H using an industrial-based numerical simulator. The basic design goal was to decrease the threshold current by using only silicon carbide polymers. We could obtain a working model at stable optical wavelength of 0.83μm. This paper provides key results of the device characteristics, including the light power... 

    Effect of nanoparticle content on the microstructural and mechanical properties of nano-SiC dispersed bulk ultrafine-grained Cu matrix composites [electronic resource]

    , Article Journal of Materials & Design ; December 2013, Volume 52, Pages 881–887 Akbarpour, M. R ; Salahi, E ; Alikhani Hesari, F ; Kim, H. S ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    In this study, the microstructural and mechanical features of monolithic pure Cu and Cu matrix nanocomposites reinforced with three different fractions (2, 4, and 6 vol%) of SiC nanoparticles (n-SiC) fabricated via a combination of high energy mechanical milling and hot pressing techniques were investigated. The fabricated composites exhibited homogeneous distribution of the n-SiC with few porosities. It was found that the grain refinement, the planar features within the grains, and the lattice strains increase with increase in the n-SiC content. The yield and compressive strengths of the nanocomposites were significantly improved with increases in the n-SiC content up to 4 vol%; then they... 

    Analysis of the various elements of heat sources in silicon carbide polymers (6H-SiC and 3C-SiC) semiconductor laser

    , Article Asian Journal of Chemistry ; Volume 24, Issue 5 , 2012 , Pages 2333-2335 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    In the present paper, we investigated the various elements of heat sources within a silicon carbide polymers (6H-SiC and 3C-SiC) semiconductor laser. The device employs 3C-SiC quantum well (QW) which is sandwiched between two layers of 6H-SiC as cladding regions that can be interpreted in terms of a type-II heterostructure character and a built-in electric field due to the pyroelectricity of 6H using a numerical simulator. The basic design goal was the study of the various elements of heat sources, including the Joule heat power, the Peltier-Thomson heat power and the recombination heat power  

    Analysis of lattice temperature effects on a GaInP/6H-SiC strained quantum-well lasers

    , Article Asian Journal of Chemistry ; Volume 25, Issue 9 , Oct , 2013 , Pages 4715-4717 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Hosseini, S. E ; Sharif University of Technology
    In this paper, simulative study on the effects of lattice temperature on a GaInP/6H-SiC strained quantum-well (QW) laser's device is presented. Loss mechanisms are severe in the edge-emitting lasers. As a consequence, the wall-plug efficiency is sensitive to changes in temperature. The lasers used in this work were separate-confinement quantum-well lasers with a single strained GaInP, located in a latticematched waveguide core and cladding region of 6H-SiC. This paper provides the key results of the wall-plug efficiency upon the lattice temperature  

    Molten salt synthesis of a SiC coating on graphite flakes for application in refractory castables

    , Article Ceramics International ; 2016 ; 02728842 (ISSN) Masoudifar, S ; Bavand Vandchali, M ; Golestani Fard, F ; Nemati, A ; Sharif University of Technology
    Elsevier Ltd 
    A silicon carbide coating was formed on the surface of graphite flakes by reaction of molten Si with carbon at 1100-1300. °C in a 95%KCl-5%NaF molten salt under Ar atmosphere. The effect of temperature and Si/graphite ratio in the initial mixture on the quality and the amount of SiC were investigated by XRD and SEM/EDS analyses. Also, the water wettability, oxidation resistance and zeta potential of un-coated and coated graphite were examined by TGA analysis and sedimentation test. The results show the amount of coating to increase in the coated flakes with increasing temperature and Si/graphite ratio. The SiC coating improves water wettability of graphite and acts as a protective layer to... 

    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... 

    Thermal synergistic effect in hybrid filler epoxy composites consisting of graphene nanoplatelets and SiC particles

    , Article Thermal Science and Engineering Progress ; Volume 25 , 2021 ; 24519049 (ISSN) Nouri Borujerdi, A ; Kazemi Ranjbar, S ; Sharif University of Technology
    Elsevier Ltd  2021
    The use of hybrid filler is a promising strategy for development of thermally conductive polymer composites. This paper reported the measurement of thermal conductivity of the epoxy composite filled with a hybrid filler of graphene nanoplatelet (GNP) and silicon carbide (SiC) microparticles. For this hybrid filler, the effect of the average size of SiC on composite thermal conductivity was examined. The results showed that the thermal synergistic effect was highly affected by the average size of the SiC. By using a hybrid filler of 11% vol. GNP and 9% vol. 1 µm-size SiC micro-particles thermal conductivity has reached 3.44 W m−1 K−1. This value is 42% higher than the thermal conductivity of... 

    Effect of SiC particles on the laser sintering of Al-7Si-0.3Mg alloy

    , Article Scripta Materialia ; Volume 59, Issue 2 , 2008 , Pages 199-202 ; 13596462 (ISSN) Simchi, A ; Godlinski, D ; Sharif University of Technology
    The direct laser sintering of Al-7Si-0.3Mg/SiC composites was studied. It is shown that the densification rate obeys first-order kinetics. The rate constant is found to increase at low SiC fractions but abruptly decreases at >∼5 vol.%. In the presence of ceramic particles, the melt track becomes more stable and a more continuous sintered surface is obtained. Meanwhile, significant reaction occurs between the aluminum melt and the reinforcement particles, leading to formation of Al4SiC4 and silicon particles. The solidification microstructure is also altered. © 2008 Acta Materialia Inc  

    Foamability and compressive properties of AlSi7-3 vol.% SiC-0.5 wt.% TiH2 powder compact

    , Article Materials Letters ; Volume 62, Issue 10-11 , 2008 , Pages 1561-1564 ; 0167577X (ISSN) Esmaeelzadeh, S ; Simchi, A ; Sharif University of Technology
    This paper presents experimental results on the foaming behavior and compressive properties of AlSi7-3 vol.% SiC metal foam. Elemental powders of Al, Si, SiC and TiH2 were mixed, hot compacted and foamed at 750, 780 and 810 °C. It was shown that the addition of fine SiC particles (mean diameter of 3 μm) increases the melt expansion and improves the stability of AlSi7 foam. A less drainage in the cell structure was also noticed. Meanwhile, large irregular cells in the macrostructure and a slight degradation of the mechanical properties under compressive load were observed. © 2007 Elsevier B.V. All rights reserved  

    Iterative interference cancellation and decoding for a coded UWB-TH-CDMA system in multipath channels using MMSE filters

    , Article 14th IEEE 2003 International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC2003, Beijing, 7 September 2003 through 10 September 2003 ; Volume 2 , 2003 , Pages 1555-1559 ; 0780378229 (ISBN); 9780780378223 (ISBN) Bayesteh, A ; Nasiri Kenari, M ; Sharif University of Technology
    In this paper, we consider a low-complexity iterative receiver for decoding multi-user information data for the bandwidth efficient convolutionally coded UWB-TH-CDMA system, in a multipath channel. The proposed receiver structure consists of a bank of soft interference cancellers (SIC), followed by a block of MMSE filters. The outputs of these filters, are feeded to a bank of likelihood calculators (LC), each followed by a soft-input soft-output (SISO) convolutional decoder. Information is fed back from SISO decoders to SICs for interference cancellation. This receiver requires the knowledge of the attenuation and delay of the strongest path of each active user. We evaluate the performance... 

    Silicon Vacancy in 4H-SiC: Many-body Electronic Structure

    , M.Sc. Thesis Sharif University of Technology Najafi Ivaki, Moein (Author) ; Vesaghi, Mohammad Ali (Supervisor)
    The silicon vacancy in silicon carbide is a strong emergent candidate for applications in quantum information processing. 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states. Electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) investigations suggest that silicon vacancy point defects in SiC possess properties similar to those of the NV center in diamond. We provide a new theoretical frame to explain a wider range of experimental results. Employing a proposed generalized Hubbard model, with the help of electronic structure programs, DFT, second quantization, and various computational approaches, we obtain new... 

    Investigation the Machinability of Al/SiC Composite

    , M.Sc. Thesis Sharif University of Technology Rahiminasab, Jafar (Author) ; Kouchakzade, Mohammad Ali (Supervisor) ; Yoosafi, Reza (Supervisor)
    Metal matrix composites (MMCs) have received considerable attention due to their excellent engineering properties, but their poor machinability has been the main deterrent to their substitution for metal parts. The hardness and abrasive nature of reinforcement phase causes rapid tool wear during machining and, consequently, high machining costs. This paper discusses an experimental investigation on the machinability of Al-SiC particulate metal matrix composite produced by powder metallurgical process with , and %SiC. Continuous dry turning of round composite bars using titanium carbide inserts has been selected as the test method. The influence of machining parameters, e.g. cutting speed,... 

    Synthesis of Super Hydrophobic and Anti-Wear Coating with SiO2 and SiC Nano Particles on Glass Surface )

    , M.Sc. Thesis Sharif University of Technology Zahmatkesh Saredorahi, Amir Hossein (Author) ; Dolati, Abolghasem (Supervisor)
    In this research we developed a superhydrophobic and anti-wear coating on a glass substrate using SiO2 nanoparticles to form a transparent superhydrophobic thin film and SiC nanoparticles to improve the wear resistance of coating.
    Silica nanoparticles were produced via a simple sol gel method from Tetraethylorthosilicate (TEOS) as precursor. Hexamethyldisilazane (HMDS) and Tetramethylclourosilane (TMCS) were used as hydrophobic inducing agents and at last SiC nanoparticles were dispersed in the solution in order to provide wear resistance. The final results indicate the contact angle (CA) of water droplet on the surface was about 158° and sliding angle (SA) lower than 9°. Studying the... 

    Improvement of Polymer Composites Thermal Conductivity by Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Kazemi Ranjbar, Sina (Author) ; Nouri Broujerdi, Ali (Supervisor)
    The new generation of electronic devices including 5G internet, wearable electronics, LED optoelectronics or cloud computing devices have higher power density as their computing power increases and their sizes reduce. The increase in power density leads to higher heat generation and consequently higher operating temperature which reduces their lifetime and reliability. In recent years development of novel solutions for electronic cooling has been persued. Thermal interface material that inserted between heat source and heat sink is the main component in electronic cooling. These materials consists of a polymeric base that filled with highly thermally conductive solid particles. By emergence... 

    Investigating the Joining between Silicon Carbide and Aluminum Oxide Using Separate Metal Layers

    , M.Sc. Thesis Sharif University of Technology Ahadi Dolatsara, Reza (Author) ; Nemati, Ali (Supervisor)
    Sometimes, some ceramics and metals cannot be produced in an integrated manner; In addition, ceramics, like metals, do not fully benefit from the properties of melting and casting; Therefore, it is necessary to produce this group of parts with other methods such as joining to each other. By using joining methods and technologies, it is possible to make composite materials; Therefore, in this way, the applications of ceramic or metal composites have been increasingly expanded. In many researches, bonding of oxide ceramics such as aluminum oxide to itself as well as carbide ceramics such as silicon carbide to itself have been investigated. In this research, the bonding mechanisms of two types... 

    Study the effect of architectural modification on fracture behavior of Al-DRA composite

    , Article Mechanics of Advanced Materials and Structures ; Vol. 21, issue. 8 , 2014 , Pages 662-668 ; ISSN: 15376494 Jamali, M ; Khalili, S ; Bagheri, R ; Simchi, A ; Sharif University of Technology
    An architectural modification method was utilized to improve fracture toughness of discontinuously reinforced aluminum (DRA) composites. Al-DRA composites having a structure similar to that of reinforced concrete were fabricated. The number of reinforcing DRA rods within Al matrix and volume fraction of SiC particles in DRA were altered to evaluate their effect on fracture behavior of these materials. It was found that architectural modification does not have any destructive influence on elastic modulus and yield strength of the composite. Moreover, the success of this method on toughness improvement strongly depends on the occurrence of debonding between Al and DRA regions upon loading  

    A study on the mechanism of electrodeposition of Ni/SiC composite coatings using impedance technique

    , Article ECS Transactions ; Volume 41, Issue 44 , 2012 , Pages 47-57 ; 19385862 (ISSN) ; 9781607683452 (ISBN) Sohrabi, A ; Dolati, A ; Electrodeposition; Sensor ; Sharif University of Technology
    Ni/SiC nanocomposite coatings were electrodeposited using Watts type bath and different SiC particle size. The electrodeposition behavior of Ni/SiC nanoelectrocomposites was studied using electrochemical techniques such as impedance spectroscopy (EIS) and voltammetry. In this study it was shown that SiC particles modify the EIS diagram and voltammograms as well as surface morphology of electrodeposited layers. Experimental results showed that SiC particles not only affect the formation of intermediate species and decrease charge transfer resistance but also increase the nucleation sites for nickel electrodeposition and thus affect the microstructure of electrodeposited Ni/SiC nanocomposites.... 

    Fabrication of SiC body by microwave sintering process

    , Article Journal of Materials Science: Materials in Electronics ; Volume 28, Issue 7 , 2017 , Pages 5675-5685 ; 09574522 (ISSN) Ahmadbeygi, S ; Khodaei, M ; Nemati, A ; Yaghobizadeh, O ; Sharif University of Technology
    Springer New York LLC  2017
    In the present study, SiC samples with 3, 5, 7.5 and 10 wt% Al2O3–Y2O3 as additives were made by powder metallurgy method, then sintering was performed by microwave-assisted process. β–SiC samples sintering was performed for 100 min. The highest sintered relative density 91.06% was achieved at 10 wt% additives content. The maximum values of hardness and toughness were up to 23.3 GPa and 6.14 MPa.m− 1/2. α–SiC and α–SiC/β–SiC samples sintering was performed for 120 min. The maximum value of density and hardness were up to 96.38% T.D and 24.88 GPa in α–SiC with 7.5 wt% additives, whereas the highest toughness was achieved at 10 wt% additives content in β–SiC samples. The α–SiC samples... 

    Hot deformation behavior of P/M Al6061-20% SiC composite

    , Article 2006 Powder Metallurgy World Congress and Exhibition, PM 2006, Busan, 24 September 2006 through 28 September 2006 ; Volume 534-536, Issue PART 2 , 2007 , Pages 897-900 ; 02555476 (ISSN); 0878494197 (ISBN); 9780878494194 (ISBN) Asgharzadeh, H ; Simchi, A
    Trans Tech Publications Ltd  2007
    In the present work, hot workability of particulate-reinforced Al6061-20%SiC composite produced by direct hot extrusion technique was studied. Uniaxial hot compression test at various temperatures and strain rates was used and the workability behavior was evaluated from the flow curves and the attendant microstructures. It was shown that the presence of SiC particles in the soft Al6061 matrix deteriorates the hot workability. Bulging of the specimens and flow lines were observed, which indicates the plastic instability during hot working. Microstructure of the composites after hot deformation was found to be heterogeneous, i.e. the reinforcement clusters were observed at the flow lines. The...