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Anodizing behavior and electrochemical evaluation of accumulative roll bonded Al and Al-SiC composite
, Article Surface and Coatings Technology ; Volume 408 , 2021 ; 02578972 (ISSN) ; Alishavandi, M ; Paydar, M. H ; Sharif University of Technology
Elsevier B.V
2021
Abstract
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. ©...
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) ; Kazemi Ranjbar, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
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...
Oriented hyperlens based on passivated porous graphene phases for sub-diffraction visible imaging
, Article Optical Materials Express ; Volume 11, Issue 9 , 2021 , Pages 2839-2853 ; 21593930 (ISSN) ; Yazdanfar, P ; Rashidian, B ; Sharif University of Technology
The Optical Society
2021
Abstract
The performance of conventional imaging lenses, relying on the phase transformation of propagating waves, is impairing due to the aberration and diffraction limits. For imaging beyond the diffraction limit, different superlens designs have been proposed. Although subdiffraction resolution imaging in the near field has been realized by the superlenses with negative refractive index, magnification of the subwavelength objects into the far field has not been fulfilled. Imaging using “hyperlens” is promising to overcome the energy spreading associated with diffraction, by utilizing negative permittivity parallel to the optical axis, and positive permittivity perpendicular to it. Among various...
Oxidation effects on transport characteristics of nanoscale MOS capacitors with an embedded layer of silicon nanocrystals obtained by low energy ion implantation
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 124-125, Issue SUPPL , 2005 , Pages 494-498 ; 09215107 (ISSN) ; Shalchian, M ; Benassayag, G ; Coffin, H ; Bonafos, C ; Schamm, S ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this paper, we have studied the effect of annealing under slightly oxidizing ambient (N2 + O2) on the structural and electrical characteristics of a limited number of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultra-low energy (1 keV) ion implantation and annealing. Material characterization techniques including transmission electron microscopy (TEM), Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on less than one hundred nanoparticles by...
From continuous to quantized charging response of silicon nanocrystals obtained by ultra-low energy ion implantation
, Article Solid-State Electronics ; Volume 49, Issue 7 , 2005 , Pages 1198-1205 ; 00381101 (ISSN) ; Grisolia, J ; Ben Assayag, G ; Coffin, H ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this paper, we present a study on the contribution of silicon nanocrystals to the electrical transport characteristics of large (100 μm × 100 μm) and small (100 nm × 100 nm) metal-oxide-semiconductor (MOS) capacitors at room temperature. A layer of silicon nanocrystals is synthesized within the oxide of these capacitors by ultra-low energy ion implantation and annealing. Several features including negative differential resistance (NDR), sharp current peaks and random telegraph signal (RTS) are demonstrated in the current-voltage and current-time characteristics of these capacitors. These features have been associated to charge storage in silicon nanocrystals and to the resulting Coulomb...
Room-temperature quantum effect in silicon nanoparticles obtained by low-energy ion implantation and embedded in a nanometer scale capacitor
, Article Applied Physics Letters ; Volume 86, Issue 16 , 2005 , Pages 1-3 ; 00036951 (ISSN) ; Grisolia, J ; Assayag, G. B ; Coffin, H ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this article, we present the room-temperature current-voltage characteristics of a nanometer scale (100×100 nm2) metal-oxide-semiconductor capacitor containing few (less than 100) silicon nanoparticles. The layer of silicon nanoparticles is synthesized within the oxide of this capacitor by ultra low-energy ion implantation and annealing. Current fluctuations in the form of discrete current steps and sharp peaks appeared in the static and dynamic I (V) characteristics of the capacitor. These features have been associated to quantized charging and discharging of the nanoparticles and the resulting Coulomb interaction to the tunneling current. © 2005 American Institute of Physics
From continuous to quantized charging phenomena in few nanocrystals MOS structures
, Article 11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technology, GADEST 2005, 25 September 2005 through 30 September 2005 ; Volume 108-109 , 2005 , Pages 25-32 ; 10120394 (ISSN); 9783908451136 (ISBN) ; Shalchian, M ; Grisolia, J ; Bonafos, C ; Atarodi, S. M ; Claverie, A ; Pichaud B ; Claverie A ; Alquier D ; Richter H ; Kittler M ; Richter H ; Kittler M ; Sharif University of Technology
Trans Tech Publications Ltd
2005
Abstract
In this paper, we present a study on the contribution of silicon nanocrystals to the electrical transport characteristics of large (100 µ x 100 µm) and small (100 nm x 100 nm) metaloxide- semiconductor (MOS) capacitors at room temperature. A layer of silicon nanocrystals is synthesized within the oxide of these capacitors by ultra-low energy ion implantation and annealing. Several features including negative differential resistance (NDR), sharp current peaks and random telegraph signal (RTS) are demonstrated in the current-voltage and current-time characteristics of these capacitors. These features have been associated to charge storage in silicon nanocrystals and to the resulting Coulomb...
Synthesis mechanism and microstructure characterization of ZrB2–ZrC–SiC nanocomposite synthesized via magnesium boro/carbothermal reduction at low temperatures
, Article Materials Chemistry and Physics ; Volume 280 , 2022 ; 02540584 (ISSN) ; Bavand Vandchali, M ; Mashhadi, M ; Nemati, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In this study, magnesium boro/carbothermal reduction of zirconium silicate (ZrSiO4) was employed to synthesize zirconium-based composite nanopowders of ZrB2–SiC, ZrB2–ZrC–SiC, ZrC–SiC, and ZrC. For this aim, three different temperatures of 1200 °C, 1300 °C, and 1450 °C were selected as the supposed temperatures for synthesis. Elemental Mg and NaCl were also selected to assist reduction process. In addition, effects of different C/Zr ratios as well as using elemental boron and B4C as two different boron sources were investigated on the final produced phases. Subsequently, XRD and SEM/EDS analyses were carried out to elaborate microstructure and phase studies. Finally, STA carried out up to...
Mapping and Scheduling Applications onto Multi-Core Chip-Multiprocessors in Dark-Silicon Era
, M.Sc. Thesis Sharif University of Technology ; Sarbazi Azad, Hamid (Supervisor)
Abstract
Growing transistor counts, limited power budgets, and the breakdown of voltage scaling are currently conspiring to create a utilization wall that limits the fraction of a chip that can run at full speed at one time. This concept is the basis of the Dark Silicon definition. To address this issue, it is needed a structure to guaranty Limited power budget and obtain sufficient flexibility and performance for different applications with variety communication needs. Regarding to this structure, our aim is to present a platform for Networks-on-Chip that uses clustering and resource sharing among cores. Moreover, as task mapping on processing elements in NOCs is one of the most effective way to...
Electroplating of Bronze-Graphite-SiC Composite Coating
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Composite coatings including self-lubricant particles such as graphite, MoS2, Al2O3 and SiC are extensively used to decrease the coefficient of friction of tribo-surfaces. Adding lubricant particles to an appropriate metallic matrix like copper, nickel, lead and their alloys is a suitable option in severe condition –for instance high temperature and low pressure- which liquid lubricants will be failed. Bronze can give various properties such as wear resistance, corrosion and oxidation protection, However cyanide solutions for electroplating process have environmentally limited for plating of Cu-Sn. In this research, a chloride electrolyte for bronze electroplating was developed and effect of...
The Effect of Mn on Microstructure and Mechanical Properties on Splat Cooled Al-20Si-5Fe-3Cu-1Mg Alloy
, M.Sc. Thesis Sharif University of Technology ; Davami, Parviz (Supervisor)
Abstract
In this research ,Al-20Si-5Fe-3Cu-1Mg-XMn alloys were produced by gas atomizing and melt spinning processes. Microstructure and growth morphology of powder and ribbons were investigated using optical microscopy , scanning electron microscopy. powders were hot pressed at 400ºC/250Mpa and microstractural variations, mechanical properties were evaluated after consolidation. Results show that relatively high cooling rate in gas-atomized powders lead to refinement of microstructure and formation of semi-equilibrium δ intermetallic phase . As the powder particle size decrease , the growth morphology changes from primary silicon + euthectic to euthectic + primary dendritic aluminum . Mn changed the...
Fatigue Behavior of Al-SiC Nanocomposite
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor) ; Ekrami, Ali Akbar (Supervisor)
Abstract
Recently, mechanical properties of advanced materials such as nanostructured and ultra-fine materials and especially nanocomposites were studied by lots of researcher. In this study, fatigue behavior of Al-SiC nanocomposites is observed. Ultra-fine grains Al matrix nanocomposites reinforced with 50 nm diameter SiC nanoparticles were produced by milling and hot extrusion. For this purpose, pure aluminum powder was mixed with 2, 4 and 6 Vol. % of SiC nanoparticles and then milled by planetary mill. The milled powder then were degased in an Argon atmosphere furnace, cold pressed and then hot extruded. Closed die-hot forging was used with about 18.8% reduction in cross section in order to...
Fabrication, Visualization and Calibration of a Novel TEM Microactuator
, M.Sc. Thesis Sharif University of Technology ; Alasti, Aria (Supervisor)
Abstract
Nowadays precise nano positioning plays an important role in micro systems. Precise positioning at nano scale plays a basic role in nano science such as micro -robotics, solid state physics and photonics. Manipulating matter in a molecular scale creates a dramatic change and restruturing in macro scale engineering. During this research a novel TEM micro actuator is designed and fabricated based on calibration criteria. This structure was fabricated with SOI wafer (silicon on insulator) in micro scale level for the first time in Iran. This compliant consists of 12 TEM actuators end in 3DOF (In-plane) motion. The new micro actuator operates based on the thermal expansion due to voltage. Each...
Analysis and Design of Analog Operators Based on Photonic Metasurfaces
, M.Sc. Thesis Sharif University of Technology ; Khavasi, Amin (Supervisor) ; Rejaei, Behzad (Co-Advisor)
Abstract
Optical computing has emerged as a promising candidate for real-ime and parallel continuous data processing. Optical devices that perform spatial and spatiotemporal transformations of optical signals are of great interest for a wide range of applications including ultrafast all-optical information processing and analog optical computations. Although plasmonic metasurfaces(for analog computing applications) was investigated in the past, they are not realizable. Consequently the silicon photonics is a good alternative for realizing these applications.Firstly, the optical computing and its important features explained and a common architecture was introduced. in addition, another two structures...
CdO/PSi/Si photo detector
, Article International Journal of Nanotechnology ; Volume 6, Issue 10-11 , 2009 , Pages 997-1005 ; 14757435 (ISSN) ; Iraji zad, A ; Mahdavi, S. M ; Samadpoor, M ; Sharif University of Technology
2009
Abstract
In spite of various works which were carried out on CdO and porous Si (PSi) separately, the interesting properties of CdO/PSi/Si system are not known well. In this work, we study the photoconductivity of deposited CdO layer on PSi/Si system. PS and CdO layers were prepared by electrochemical anodisation of p-type crystalline silicon and pulsed laser deposition (PLD) of cadmium oxide target. Then samples were annealed in air at 500°C to increase their optical transmissions to a value as large as 90% for wavelengths above 700 nm. The XRD study reveals that the annealed films are polycrystalline with grain size of about 25 nm. SEM micrograph of the CdO/PSi/Si system indicates that CdO layer has...
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) ; Godlinski, D ; Sharif University of Technology
2008
Abstract
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) ; Simchi, A ; Sharif University of Technology
2008
Abstract
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
Effect of Si content and heat treatment on microstructure and magnetic properties of mechanically alloyed Fe-Si powders
, Article Materials Science and Technology Conference and Exhibition, MS and T'07 - ""Exploring Structure, Processing, and Applications Across Multiple Materials Systems"", Detroit, MI, 16 September 2007 through 20 September 2007 ; Volume 4 , 2007 , Pages 2701-2712 ; 9781605601335 (ISBN) ; Abachi, P ; Madaah Hosseini, H. R ; Sharif University of Technology
2007
Abstract
In this study, the effects of milling time, chemical composition and heat treatment on microstructure and magnetic properties of nanocrystalline Fe-Si (6.5-25 at.% Si) alloys prepared by mechanical alloying have been investigated. The results show that increasing the milling time or the Si content, decreases the lattice parameter and increases the internal microstrain. The prepared powders mainly consist of micron-sized particles with an average grain size of less than 20 nm. The specific saturation magnetization values are slightly less than those of single crystal or conventional Fe-Si alloys and decrease as Si content increases. The coercive force values of the nanocrystalline as-milled...
Power consumption and performance analysis of 3D NoCs
, Article 12th Asia-Pacific Computer Systems Architecture Conference, ACSAC 2007, Seoul, 23 August 2007 through 25 August 2007 ; Volume 4697 LNCS , 2007 , Pages 209-219 ; 03029743 (ISSN); 9783540743088 (ISBN) ; Sarbazi Azad, H ; Sharif University of Technology
Springer Verlag
2007
Abstract
Nowadays networks-on-chip are emerging as a hot topic in IC designs with high integration. Much research has been done in this field of study recently, e.g. in routing algorithms, switching methods, VLSI Layout, and effects of resource allocation on system performance. On the other hand, three-dimensional integrated circuits allow a time-warp for Moore's Law. By vertically stacking two or more silicon wafers, connected with a high-density, high-speed interconnect, it is now possible to combine multiple active device layers within a single IC. In this paper, we examine performance and power consumption in a three dimensional network-on-chip structure under different types of traffic loads,...
Scanning tunneling spectroscopy of porous silicon in presence of methanol
, Article Sensors and Actuators, B: Chemical ; Volume 120, Issue 1 , 2006 , Pages 172-176 ; 09254005 (ISSN) ; Iraji zad, A ; Vaseghinia, S ; Sharif University of Technology
2006
Abstract
In this research, we used the scanning tunneling spectroscopy (STS) technique to probe the local electrical properties of the surface of meso-porous silicon and its substrate, including local density of states (DOS) in air and in methanol environment to increase our knowledge of sensing phenomena. Meso-porous silicon was prepared on p+-type Si which has high sensitivity toward methanol. Observations revealed that while the surface electrical properties of p+-type Si have not sensible change toward methanol, average local density of state of the porous layer increases after the exposure to methanol especially in the E < EF region. Moreover, large number of surface states is produced in band...