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dourandish-yazdi--mahdi
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Study of Direct Joining of Nanostructured-Zirconia to 430L Stainless Steel Produced by Co-sintering Process
, Ph.D. Dissertation Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
In this study, the joint of co-sintered zirconia/stainless steel is investigated. To this end ZrO2-3mol%Y2O3 (TZP) and 430L stainless steel powders were utilized. The joining parameters of co-sintering in zirconia/metal were studied. In order to study the microstructure, diffusion and probable reactions at the joint boundary, HRSEM, HRTEM, EPMA and micro-focused XRD methods were employed. Shear strength of the joint was also measured. Finite element simulation of residual stresses and thermodynamic studies are utilized in the next step to analyze the experimental results. It is found that the direct joining of zirconia to 430L stainless steel is feasible by co-sintering at 1350 °C under low...
Bio-inspired nanostructured sensor for the detection of ultralow concentrations of explosives [electronic resource]
, Article Journal of Angewandte Chemie International Edition ; 29 May 2012, Volume 51, Issue 22, P.5334-5338 ; Simchi, A. (Abdolreza) ; Tamjid Shabestary, Elnaz ; Hartwig, Thomas ; Sharif University of Technology
Abstract
TNT: Silicon microcantilevers modified with a three-dimensional layer of vertical titanium dioxide nanotubes can be used in micromechanical sensors with optical signal detection to detect low levels of explosives such as 2,4,6-trinitrotoluene (TNT) in the gas phase, even in the presence of other volatile impurities such as n-heptane and ethanol
Study the sintering behavior of nanocrystalline 3Y-TZP/430L stainless-steel composite layers for co-powder injection molding
, Article Journal of Materials Science ; Volume 44, Issue 5 , 2009 , Pages 1264-1274 ; 00222461 (ISSN) ; Simchi, A ; Sharif University of Technology
2009
Abstract
Recently, co-powder injection molding process (2C-PIM) has attained considerable interest to fabricate complex-shaped functional materials. The aim of this work is to study the sintering compatibility between nanocrystalline yttria-stabilized zirconia (3Y-TZP) and PIM grade 430L stainless steel (SS) powders, which is the utmost important step in the 2C-PIM process. To evaluate the mismatch strain development during the co-sintering, the isothermal and nonisothermal behaviors of the ceramic and metal powders were studied. Small bilayers of 3Y-TZP/430L were made by a powder metallurgy technique and the feasibility of simultaneous sintering and joining of the composite layer was examined....
Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers [electronic resource]
, Article Journal of Materials Letters ; 15 February 2011, Volume 65, Issue 3, Pages 523–526 ; Simchi, A. (Abdolreza) ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
Abstract
Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the...
Interface formation and bond strength in 3Y-TZP/Cr composite bilayers produced by sinter–joining [electronic resource]
, Article Materials Science and Engineering: A ; Volume 527, Issue 3, 15 January 2010, Pages 449–453 ; Simchi, A. (Abdolreza) ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
Abstract
The mechanism of interface formation during sinter–joining of nanostructured yttria stabilized zirconia (27 nm) compacts with chromium powder was investigated. The effect of sintering atmosphere, i.e. argon or vacuum, was studied. Microstructural evaluation and phase formation was examined by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and micro-focused X-ray diffraction (MFXRD) methods. It is shown that spreading and evaporation–condensation mechanisms are responsible for the interface formation. An improved joint shear-strength was obtained after sintering in vacuum (74 MPa) compared with argon (41 MPa). The result of MFXRD indicated formation of Cr-island at...
Presureless sintering of stainless steels/zirconia composite layers usable for co-powder injection moulding process
, Article Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010, 10 October 2010 through 14 October 2010 ; Volume 2 , 2010 ; 9781899072194 (ISBN) ; Simchi, A ; Hokamoto, K ; Sharif University of Technology
2010
Abstract
Sintering is the most critical step in manufacturing of functional parts by co-powder injection molding. In the present work, we studied the sintering phenomena occurring during co-sintering of metal/ceramic composite layers. Nanostructured yttria-stabilized zirconia (3Y-TZP) was co-sintered with 430L stainless steel and chromium. The sintering response was studied by dilatometer analysis in isothermal and non-isothermal modes. The microstructure of the sintered specimens was studied by scanning electron microscopy (SEM), electron-probe microanalysis (EPMA) and micro-focused X-ray diffraction (MFXRD). The strength of the joint was also determined by a shear-punch method. It is shown that...
Fabrication of porosity-graded biocompatible structures by 3D printing of Co-Cr-Mo alloy
, Article European Powder Metallurgy Congress and Exhibition, Euro PM 2007, Toulouse, 15 October 2007 through 17 October 2007 ; Volume 3 , 2007 , Pages 255-260 ; 9781899072293 (ISBN) ; Simchi, A ; Godlinski, D ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2007
Abstract
Manufacturing of complex-shaped bimetals utilizing two-color powder injection molding (2C-PIM) and three-dimensional printing (3DP) processes, which basically involve sintering of a powder/binder mixture, has been attracted a great interest. This article addresses sintering of biocompatible Co-Cr-Mo alloy for manufacturing stepwise porosity-graded composite structures. Such composite structures provide strength at the core and a porous layer for the tissue growth. To evaluate the process, two grades of gas atomized Co-Cr-Mo powder with an average particle size of 19 and 63 μm were used. Isothermal and nonisothermal sintering behavior of the loose powders under hydrogen and argon atmospheres...
3D printing of biocompatible PM-materials
, Article 2006 Powder Metallurgy World Congress and Exhibition, PM 2006, Busan, 24 September 2006 through 28 September 2006 ; Volume 534-536, Issue PART 1 , 2007 , Pages 453-456 ; 02555476 (ISSN); 0878494197 (ISBN); 9780878494194 (ISBN) ; Godlinski, D ; Simchi, A ; Sharif University of Technology
Trans Tech Publications Ltd
2007
Abstract
The fabrication of complex-shaped parts out of Co-Cr-Mo alloy and 316L stainless steel by three-dimensional printing (3DP) is studied using two grades of each alloy with average particle size of 20 and 75 nm, respectively. To produce sound specimens, the proper 3DP processing parameters were determined. The sintering behavior of the powders is characterized by dilatometric analysis and by batch sintering in argon atmosphere at 1280°C for 2h. The 3DP process has successfully produced complex-shaped biomedical parts with total porosity of 12-25% and homogenous pore structure, which is suitable for tissue growth into the pores
Sintering of zirconia/430l stainless steel bilayers for co-powder injection moulding
, Article European International Powder Metallurgy Congress and Exhibition, Euro PM 2008, Mannheim, 29 September 2008 through 1 October 2008 ; Volume 2 , January , 2008 , Pages 299-303 ; 9781899072033 (ISBN) ; Simchi, A ; Hartwig, T ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2008
Abstract
To fabricate ceramic/metal complex-shaped part by co-powder injection moulding process (2KPIM), it is essential to tailor the sintering parameters in order to gain a low mismatch shrinkage, i.e. high sintering compatibility. In the present work, nanocrystalline 3Y-TZP and commercial 430L MIM grade stainless steel powders were co-sintered at various sintering cycles. Isothermal and non-isothermal sintering behavior of the individual and composite layers in argon and vacuum atmospheres were examined. High resolution scanning electron microscopy (HRSEM) coupled with energy dispersive X-ray (EDX) analysis was used to study the bonding interface between the ceramic and metal joints. It is shown...
Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers
, Article Materials Letters ; Volume 65, Issue 3 , February , 2011 , Pages 523-526 ; 0167577X (ISSN) ; Simchi, A ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
2011
Abstract
Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the...
Interface formation and bond strength in 3Y-TZP/Cr composite bilayers produced by sinter-joining
, Article Materials Science and Engineering A ; Volume 527, Issue 3 , 2010 , Pages 449-453 ; 09215093 (ISSN) ; Simchi, A ; Hokamoto, K ; Tanaka, S ; Sharif University of Technology
2010
Abstract
The mechanism of interface formation during sinter-joining of nanostructured yttria stabilized zirconia (27 nm) compacts with chromium powder was investigated. The effect of sintering atmosphere, i.e. argon or vacuum, was studied. Microstructural evaluation and phase formation was examined by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and micro-focused X-ray diffraction (MFXRD) methods. It is shown that spreading and evaporation-condensation mechanisms are responsible for the interface formation. An improved joint shear-strength was obtained after sintering in vacuum (74 MPa) compared with argon (41 MPa). The result of MFXRD indicated formation of Cr-island at...
Sintering of biocompatible P/M Co-Cr-Mo alloy (F-75) for fabrication of porosity-graded composite structures
, Article Materials Science and Engineering A ; Volume 472, Issue 1-2 , 2008 , Pages 338-346 ; 09215093 (ISSN) ; Godlinski, D ; Simchi, A ; Firouzdor, V ; Sharif University of Technology
2008
Abstract
Manufacturing of complex-shaped bimetals utilizing two-color powder injection molding (2C-PIM) and three-dimensional printing (3DP) processes, which basically involve sintering of a powder/binder mixture, has been attracted a great interest. This article addresses sintering of biocompatible Co-Cr-Mo alloy for manufacturing stepwise porosity-graded composite structures. Such composite structures provide strength at the core and a porous layer for the tissue growth. To evaluate the process, two grades of gas atomized Co-Cr-Mo powder with an average particle size of 19 and 63 μm were used. Isothermal and non-isothermal sintering behavior of the loose powders under hydrogen and argon...
Master sintering curves of a nanoscale 3Y-TZP powder compacts
, Article Ceramics International ; Volume 35, Issue 2 , 2009 , Pages 547-554 ; 02728842 (ISSN) ; Simchi, A ; Dourandish, M ; Golestani Fard, F ; Sharif University of Technology
2009
Abstract
The sintering behavior of commercially available granulated ZrO2-3 mol% Y2O3 (3Y-TZP) powder compacts with an aggregate size of 75 nm was studied. The shrinkage response of the powder compacts during non-isothermal sintering was measured in a sensitive dilatometer at different heating rates. Densification and grain growth were also studied after isothermal firing in air according to different sintering cycles. The sintering and grain growth activation energy was estimated to be QS = 485 ± 12 kJ mol-1 and QG = 546 ± 23 kJ mol-1, respectively. Using the estimated Q-values, the master curves for sintering and grain growth were established and used for prediction of the densification and...
Pressureless sintering of 3Y-TZP/stainless-steel composite layers
, Article Journal of the American Ceramic Society ; Volume 91, Issue 11 , 2008 , Pages 3493-3503 ; 00027820 (ISSN) ; Simchi, A ; Tamjid Shabestary, E ; Hartwig, T ; Sharif University of Technology
2008
Abstract
A pressureless sintering method was utilized to fabricate metal/ceramic joints out of yttria-stabilized zirconia (3Y-TZP) and stainless steels (SS). Ultrafine (150 nm) and nanoscale (75 nm) 3Y-TZP particles and micrometric 17-4PH, 316L, and 420 SS (<31 μm) powders were tested. Isothermal and nonisothermal sintering behaviors of the powders and composite layers in hydrogen, argon, and vacuum atmospheres were examined. It was found that the mismatch strain between the zirconia ceramic and SS during cosintering is significant, which leads to bond cracking and joint failure. Nevertheless, interlayer diffusion of Zr, Fe, and Cr and the formation of a reaction zone, particularly during vacuum...
Decentralized control of reconfigurable robots using joint-torque sensing
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 581-585 ; 9781467372343 (ISBN) ; Sharif University of Technology
2015
Abstract
In this paper, a decentralized controller for trajectory tracking of modular and reconfigurable robot manipulators is developed. The proposed control scheme uses joint-torque sensory feedback; also sliding mode control is employed to make both position and velocity tracking errors of robot manipulators globally converging to zero. Proposed scheme also guarantees that all signals in closed-loop systems will be bounded. In contrast to some of prior works in this scheme, each controller uses a smooth law to achieve its purposes. In this method, each controller uses only local information for producing control law hence separated controller can be used to control each module of manipulator and...
Two new swinging interferometers
, Article Journal of Optics A: Pure and Applied Optics ; Volume 9, Issue 7 , 2007 , Pages 560-564 ; 14644258 (ISSN) ; Rashidian, B ; Sharif University of Technology
2007
Abstract
The most important disadvantage of swinging interferometers is that the optical path difference created in them is a nonlinear function of the rotation angle. In this paper, two new swinging interferometers are presented which have good linearity and provide a larger path difference in response to the rotation angle compared to other interferometers. This makes them suitable for applications such as high-resolution spectroscopy, and precision micro and nanopositioning. In one of these two interferometers, the optical path difference is created by rotation of a system composed of four mirrors, and in the other one it is created by rotation of a system consisting of two mirrors. They are not...
Numerical Investigation of Instabilities of Flow in Micro-fluid
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
This research concerns investigating the behavior of two-phase flow in the inlet and outlet of the microchannels.Both the droplet based and the continuous microfluidics are considered. For the continuous system whenthe minor fluid enters the microchannel, due to ratio of viscosity of two fluids, viscous folding occurs.Viscous folding phenomena is similar to the buckling phenomena in solids.This means that the viscosity of the fluid, which is applied to two sides of the fluid layer, causes folding the fluid layer and changing the shape of it. For the study we employ a VOF based numerical routine. In order to verify numerical results, the grid and the time step independenciesare checked. In...
Comparison of Classic Regression Model and Geographically Weighted Regression Model in Trip Generation Models,Case Study in Shiraz
, M.Sc. Thesis Sharif University of Technology ; Kermanshah, Mohammad (Supervisor)
Abstract
Trip demand analysis is among the most important parts in comprehensive transportation studies. Developing four stage models including trip generation, trip distribution, mode choice, and assignment are so common in demand analyzing. In this study, trip generation models have been studied and to analyze data, two different methods including OLR and GWR are utilized. This study aims to examine relationship between aggregate zones in order to forecast future trips. Moreover, results of modeling trip generation with two different methods, OLR and GWR, are compared. Comparing different levels of aggregation reveals that as the number of zones decreases, the results get better. Decreasing number...
MBBR and MBR Reactor Configuration for Better Performance
, M.Sc. Thesis Sharif University of Technology ; Borgheei, Mahdi (Supervisor)
Abstract
Membrane bioreactors (MBRs) which are commonly understood as the combination of membrane filtration and biological treatment using activated sludge have several advantages, but membrane fouling reduces the membrane efficiency, permeability and lifetime. An alternative is replacing a moving bed biofilm reactor (MBBR) with the activated sludge system which may reduce the effect of membrane fouling. The sludge produced in MBBRs has poor settling characteristics, therefore, their efficiency is limited by the sedimentation tank performance and they require a larger settling surface. The combination of moving bed biofilm reactors and membrane bioreactors can compensate for the drawbacks of both of...
Improvement of palm oil and sunflower oil blends by enzymatic interestrification
, Article International Journal of Food Science and Technology ; Volume 46, Issue 5 , 2011 , Pages 1093-1099 ; 09505423 (ISSN) ; Alemzadeh, I ; Sharif University of Technology
2011
Abstract
Palm oil (PO) and sunflower oil (SFO) blends with varying proportions were subjected to enzymatic interesterification (EIE) using a 1,3-specific immobilised lipase. The interesterified blends were evaluated for their slip melting point (SMP), solid fat content (SFC) at 10-40°C, p-anisidine value, peroxide value, free fatty acids (FFA), induction period of oxidation at 110°C (IP110) and composition of fatty acids by gas chromatography. Under EIE treatment, the blends of PO and SFO in different proportions (20:80, 40:60, 50:50, 60:40 and 80:20) had saturated and unsaturated fatty acid content in the range of 37.6-52.0% and 48.0-62.4%, respectively. The blends showed a considerable reduction in...