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Si/Si, Si/SiO2 and SiO2/SiO2 fusion wafer bonding
, Article Scientia Iranica ; Volume 10, Issue 4 , 2003 , Pages 477-480 ; 10263098 (ISSN) ; Rashidian, B ; Sharif University of Technology
Sharif University of Technology
2003
Abstract
The wafer bonding process has many applications in the fabrication of microelectronic, optoelectronic, power and micromachined devices. In this article, fusion bonding of silicon wafers and study of their interface are reported for the first time in Iran. Also, the bonding of two silicon wafers, with one (or both) of the wafers having a thermally grown silicon dioxide layer, has been performed and tested. © Sharif University of Technology, October 2003
Investigation of warm compaction and sintering behaviour of aluminium alloys
, Article Powder Metallurgy ; Volume 46, Issue 2 , 2003 , Pages 159-164 ; 00325899 (ISSN) ; Veltl, G ; Sharif University of Technology
IOM Communications Ltd
2003
Abstract
The effects of warm compaction on the green density and sintering behaviour of aluminium alloys were investigated. Particular attention is paid to prealloyed powders, i.e. eutectic and hypereutectic Al-Si alloys, regarding their potential applications in the automotive industry. The effects of chemical composition, alloying method, compacting temperature and the amount of powder lubricant were studied. The compaction behaviour was examined by an instrumented die enabling simultaneous measurement of density, die wall friction coefficient, the triaxial stresses acting on the powder during the course of compaction and ejection pressure. The sintering behaviour was studied via dilatometeric...
Transient analysis of injection-locked frequency dividers
, Article 2002 45th Midwest Symposium on Circuits and Systems, Tulsa, OK, 4 August 2002 through 7 August 2002 ; Volume 3 , 2002 , Pages III381-III384 ; Sharif University of Technology
2002
Abstract
Injection locked frequency dividers (ILFD) are used for frequency division to reduce the overall power consumption. By injecting a high frequency signal to an LC oscillator, injecting signal gets synchronous with oscillator output. All ILFDs analysis reports are based on steady state solution when locking is reached. At the same time, it is important to consider transient analysis too. In this paper a simple model is developed to study phase transient analysis when injecting signal is small in amplitude. This model can be used for large signal injection as a good approximation
An investigation of the silicon role on austenite recrystallization
, Article Materials Letters ; Volume 56, Issue 6 , 2002 , Pages 984-989 ; 0167577X (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2002
Abstract
The role of silicon on austenite recrystallization was investigated using hot compression experiments on a low carbon and a high silicon steel samples. The models were proposed to describe the hot deformation behavior of metals regarding dynamic recovery. The rate of static recrystallization was found lower in the silicon steel in comparison with low carbon steel. Silicon was found to produce a lower rate of dynamic recovery due to its effect on the austenite staking fault energy
Multicomponent transport across nonporous polymeric membranes
, Article Desalination ; Volume 144, Issue 1-3 , 2002 , Pages 93-101 ; 00119164 (ISSN) ; Farhadpour, F. A ; Soltanieh, M ; Sharif University of Technology
Elsevier
2002
Abstract
The theoretical description of multicomponent transport across nonporous polymeric membranes was investigated using two alternative frameworks: the phenomenological approach of irreversible thermodynamics and the mechanistic Stefan-Maxwell formulation. The transport models developed account for potential equilibrium and/or kinetic coupling of fluxes and the contribution of diffusion induced non-selective flow within the polymer. The models were validated against transient dialysis and pervaporation data for the {ethanol-water}/silicone rubber system. A critical assessment was obtained by recovering the model parameters from the dialysis data and using the same parameters to predict the...
Drug release from silicon polymer matrices containing an osmotic agent or a water-swelling additive
, Article Iranian Journal of Science and Technology, Transaction B: Technology ; Volume 26, Issue 2 , 2002 , Pages 197-204 ; 03601307 (ISSN) ; Sharif University of Technology
2002
Abstract
Potassium chloride, as an osmotic agent and poly methacrylic acid, as a water-swelling additive have been incorporated in polydimethyl siloxane. By using caffeine as a model drug, the results of release experiments from two systems have been compared. Because of osmotic rupturing pseudo-zero-order release kinetics preceded by marked burst effect were observed. Since osmotic pressure of PMAA is higher than that of KCI, drug release rate from PMAA-PDMS matrices is higher than that from KCI-PDMS matrices. Since KCI is release along with the drug, but PMAA is not, therefore water-swelling additives may provide efficient drug release without releasing undesirable substances
Thermal desorption of ultrathin silicon oxide layers on Si(111)
, Article Semiconductor Science and Technology, Bristol, United Kingdom ; Volume 15, Issue 2 , 2000 , Pages 160-163 ; 02681242 (ISSN) ; Taghavinia, N ; Ahadian, M ; Mashaei, A ; Sharif University of Technology
IOP
2000
Abstract
The mechanism of oxide desorption from the surface of Si(111) is studied. Oxide layers formed by different chemical treatments were thermally removed in a UHV chamber and the removal process was probed by Auger electron spectroscopy. Results show that the oxide formed by HCl desorbs very fast and the desorption rate is initially almost linear in time, while for oxides formed by HNO3, H2SO4 and NH4OH the rate is initially slow, becoming faster at later times. Similarity in AES spectra of different oxides indicates that the difference in the desorption rates of different oxides cannot be attributed to the difference in chemical environment. Linear increase of void coverage with the square of...
Chemomechanical Modeling of Silicon Electrode in Lithium-Ion Battery by Considering the Effects of Large Plastic Deformation and Strain Rate
, Ph.D. Dissertation Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Argavani Hadi, Jamal (Supervisor)
Abstract
In Li-ion batteries, large volume changes of electrodes with high capacity, such as silicon electrodes during charging and discharging processes (insertion/extraction of lithium into/from the electrode), lead to restrictions on the use of this type of electrode. Given the very high capacity of silicon, predicting and modeling the behavior of silicon electrodes during electrochemical cycles is important and is also addressed in this thesis. First, using the theory of linear elasticity, relations are proposed that couple the diffusion of particles with small elastic deformation. The effect of hydrostatic stress on diffusion and stresses is investigated in lithiation processes. Then, the...
Investigation of the Effects of Various Parameters on Microstructure and Mechanical Properties of Nano-Composite Al-Al2O3 and Al-Sic Produced by Accumulative Roll Bonding
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh Changiz, Abbas (Supervisor)
Abstract
Accumulative roll bonding has been used as novel method to produce the composite with ultra fine grain microstructure. This method has two steps, impose the particles as reinforcement between the layers by roll bonding process and then distribute the particles in matrix and generat an ultra fine grain microstructure during the ARB passes. In the present work, ARB process was performed to produce the Al/SiC and Al/Al2O3 nano-composites with various particles size and different volume fraction of reinforcement. Microscopic observations such as OM, SEM and TEM and XRD analyses were used to investigate the microstructure of produced composites and the distribution of the particles in matrix...
Investigation And Fabrication Super Hydrophobic Coating On Building Facades
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdullah (Supervisor)
Abstract
According to the creation of high-rise buildings and structures due to the increase in urbanization and population concentration in cities and attention to the beauty of these structures and the impact of this beauty on the morale of urban people, owners or municipalities costs a lot of money for cleaning the building facade every year. On the other hand, removing contaminants from high-rise buildings facades is difficult and lifethreatening. Today, with the advancement of science and the use of self-cleaning super hydrophobic coatings, many of these costs, as well as threats to life, can be prevented. On the other hand, protection of ancient structures as a cultural capital of a country,...
Investigating The Mechanical Properties Of Two-Dimensional Silicon Dioxide With Inherent Negative Poisson's Ratio by Molecular Dynamics Method
,
M.Sc. Thesis
Sharif University of Technology
;
Tavakoli, Ruholah
(Supervisor)
Abstract
Silicon dioxide or silica with the chemical formula SiO2 is the basic component of many minerals. SiO2 films and sheets are widely used in mechanics, optics and electronics due to their outstanding mechanical and electronic performance. The main reason for research in the field of materials with negative Poisson's ratio is their unusual properties, which arise due to the inherent property of negative Poisson's ratio. In this research, the mechanical properties of four two-dimensional silica structures at a temperature of one Kelvin were investigated with the help of molecular dynamics simulation. Also, the sensitivity of the results to the system size and strain rate was studied, and the...
Investigating the Joining between Silicon Carbide and Aluminum Oxide Using Separate Metal Layers
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor)
Abstract
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...
Investigating the Effects of Heat Treatment and Y Addition on the Microstructure, Mechanical Properties and Corrosion Behavior of Bio-Degradable Mg–Si Alloys
, M.Sc. Thesis Sharif University of Technology ; Alizadeh, Reza (Supervisor)
Abstract
In Mg–Si alloys, both primary and eutectic Mg2Si particles normally appear with sharp edges, which can lead to weak mechanical properties as the result of stress concentration at the sharp corners of these brittle particles. On the other hand, the morphology, size and distribution of Mg2Si particles affect corrosion behavior of Mg–Si alloys. Thus, it would be of great importance to modify the morphology of these particles. In this study, microstructure modification mechanisms after 0.5 wt% Y addition and heat treatment (HT) at 420 ◦C for 24 h are comprehensively studied in hypo-eutectic Mg–1Si and hyper-eutectic Mg–2Si alloys. Microstructural observations were performed using optical and...
Molecular Dynamic Simulation of Friction Reduction in Two-Phase Flows with Nanostructures and Study of the effect of Electric Field
, M.Sc. Thesis Sharif University of Technology ; Kazemzadeh Hannani, Siamak (Supervisor) ; Moosavi, Ali (Supervisor)
Abstract
The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Since in such systems the surface structure plays a key role, in the first part of this study, the performance of the hierarchical nanostructures is explored. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. The flow is considered between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics (MD) method. The size of the nanostructures and the distance between them have been studied to find whether a design with maximum flow rate exists. The nanostructures have two...
Evaluation of Microstructure and Wear Behaviour of Nicrbsi Composite Coating Deposited by Atmospheric Plasma Spray and Plasma Transferred Arc on Steel Substrate
, M.Sc. Thesis Sharif University of Technology ; Movahedi, Mojtaba (Supervisor) ; Kokabi, Amir Hossein (Supervisor)
Abstract
Nowadays, in many industrial applications, protecting surfaces has become necessary. This research attempted to create a coating resistant to the wear of NiCrBSi with the help of the atmospheric plasma spray and the process of plasma Transferred Arc on the substrate of the simple carbon steel. Also, in order to study the effect of compositing on hardness and abrasive properties of the APS coatings, NiCrBSi powder was strengthened with 25 weight percent of Titanium Carbide particles so that the NiCrBSi-25TiC composite coating could also be created. According to the nature of the APS process, the substructure of this coating always has some porosity and layered structure, and the connection of...
Properly-tuned continuum and atomistic models for vibrational analysis of the silicon nanoplates
, Article International Journal of Mechanical Sciences ; Volume 229 , 2022 ; 00207403 (ISSN) ; Nejat Pishkenari, H ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The high computational costs of atomistic simulations for the investigation of nanostructures, despite their accuracy, necessitate efforts to develop efficient continuum models. Since the classical continuum mechanics assume the matter as continuous and ignore the size dependency of material properties, these theories fail to capture the behavior of materials at the nanoscale. Size-dependencies of nanostructures could result in the emergence of surface effects. This paper, for the first time, aims to develop and tune surface-enhanced continuum models to predict the vibrational properties of nanoplates which are inherently discrete at the nanoscale. Regarding this aim, we use a composite...
Design guidelines for a tunable SOI based optical isolator in a partially time-modulated ring resonator
, Article IEEE Photonics Journal ; Volume 14, Issue 5 , 2022 ; 19430655 (ISSN) ; Mehrany, K ; Memarian, M ; Jamshidi, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
In this paper, we present the design guidelines for a tunable optical isolator in an SOI-based ring resonator with two small time-modulated regions. By considering a physical model, the proper geometrical and modulation parameters are designed, based on a standard CMOS foundry process. The effect of the variation of the key parameters on the performance of the isolator is explained by two counter-acting mechanisms, namely the separation between the resonance frequencies of counter-rotating modes and energy transfer to the side harmonic. We show that there is a trade-off between these parameters to obtain maximum isolation. Consequently, by applying the quadrature phase difference one can...
Friction reduction of Al2O3, SiO2, and TiO2 nanoparticles added to non-Newtonian water based mud in a rotating medium
, Article Journal of Petroleum Science and Engineering ; Volume 217 , 2022 ; 09204105 (ISSN) ; Sedaghat, A ; Rashidi, M ; Sabati, M ; Vaidyan, K ; Ali, N ; Omar, M. A. A ; Hosseini Dehshiri, S. S ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In drilling industry, energy consumption counts from 20 to 40 percent of total costs. Enhanced water-based mud (WBM) drilling fluids with nanoparticles can save energy in drilling processes. An in-house Taylor-Couette flow system (TCS) was developed at Australian University (AU) to study WBM enhanced by Al2O3, SiO2, and TiO2 nanoparticles. The TCS is really a practical tool to help well drillers with a rough idea of viscosity when nanoparticles are added. The TCS for sure cannot substitute advanced rheometry. The goal of the present experiment is to produce a rough estimate in field operation. Experimental results were examined with several rheology models in our previous publications. In...
Plasma-enhanced chemical vapor deposition for fabrication of yolk-shell SnO2@Void@C nanowires, as an efficient carbon coating technique for improving lithium-ion battery performance
, Article Materials Science in Semiconductor Processing ; Volume 149 , 2022 ; 13698001 (ISSN) ; Mousavi, M. R ; Yasoubi, M ; Sanaee, Z ; Ghasemi, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
This manuscript describes the implementation of plasma-enhanced chemical vapor deposition (DC-PECVD) and vapor-liquid-solid (VLS) techniques to fabricate a yolk-shell SnO2@Void@C nanowire (NW) structure. SnO2 nanowires have been synthesized on the stainless steel mesh substrate through the VLS method. The PECVD-assisted growth of carbon nanolayer on the SnO2 and SiO2 coated SnO2 NWs has been performed to fabricate SnO2@C core-shell and SnO2@SiO2@C yolk-shell structures, respectively. A consequent silica etching process converted the SnO2@SiO2@C into SnO2@Void@C structure. The electrochemical performance of bare SnO2 NWs, SnO2 NWs @ C, and SnO2 @Void @ C coaxial NWs structures have been...
Effects of heat treatment and Y addition on the microstructure and mechanical properties of as-cast Mg–Si alloys
, Article Materials Science and Engineering A ; Volume 859 , 2022 ; 09215093 (ISSN) ; Alizadeh, R ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In Mg–Si alloys, both primary and eutectic Mg2Si particles normally appear with sharp edges, which can lead to weak mechanical properties as the result of stress concentration at the sharp corners of these brittle particles. Thus, it would be of great importance to modify the morphology of these particles. In this study, microstructure modification mechanisms after 0.5 wt% Y addition and heat treatment (HT) at 420 °C for 24 h are comprehensively studied in hypo-eutectic Mg–1Si and hyper-eutectic Mg–2Si alloys. Microstructural observations were performed using optical and scanning electron microscopy equipped with electron disperse spectroscopy, while phase analysis was done by X-ray...