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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
Pore Network Model of Two Phase Flow in low permeable carbonate Rock
, Ph.D. Dissertation Sharif University of Technology ; Bozorgmehry, Ramin (Supervisor) ; Pishvaie, Mahmoud Reza (Supervisor)
Abstract
Development of pore network models for real porous media requires a detailed understanding of physical processes occurring on the microscopic scale and a complete description of porous media morphology. In this study, the microstructure of porous media has been represented by three dimensional networks of interconnected pores and throats which are designed by an object oriented approach. Afterwards, the connectivity of the system has been optimized by an optimization algorithm. To validate the methodology, a network of a carbonate sample is constructed. In this model, the geometrical characteristics of the pores and throats, such as their shapes, effective radii and lengths, are selected...
Study of the Evolution of Three-dimensional Pore Structure during Sintering of High Density Polyethylene Powders with Different Particle Size and Melt Flow Index
, M.Sc. Thesis Sharif University of Technology ; Pircheraghi, Gholamreza (Supervisor)
Abstract
Recently, macroporous polymers have gained wide acceptance for applications such as filters, membranes, biodegradable scaffolds, retention media, sound mufflers and etc. In this research, by keeping in mind the importance of the pore structure in the functionality of the porous part, three dimensional images of the pore structure during sintering was obtained using an optimized manual serial sectioning technique. Then, using the Euler number as a property of the topology of the pore surface, evolution of the three dimensional pore structure was scrutinized for two types of powders, powder A with a mean particle size of 200 micron and melt flow index of 0.2 (g/10 min) and powder B with a mean...
Effect of the Blast Furnace Slag on Microstructural and Transport Properties of the Fly Ash-based Geopolymers
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
Alkali-activated fly ash-slag (AAFS) is a new type of sustainable construction material widely studied in recent years for its desirable mechanical properties and low environmental impacts. In this study, the effects of the slag incorporation from 10 to 30% of fly ash are investigated on the strength, pore structure, and transport properties of the AAFS with various levels of fly ash replacements with slag. The unconfined compression and ultrasonic pulse velocity tests were performed to evaluate the mechanical properties of the AAFS concrete. Microstructural and mineralogical changes were studied by porosity, N2-adsorption/desorption, and SEM/EDX tests. Additionally, transport properties...
Pore level characterization of Micro-CT images using percolation theory
, Article Journal of Petroleum Science and Engineering ; Volume 211 , 2022 ; 09204105 (ISSN) ; Shams, R ; King, P. R ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Flow through porous media depends strongly on the spatial distribution of the geological heterogeneities which appear on all length scales. We lack precise information about heterogeneity distribution on various scales, from pore level to reservoir scale. However, some sources provide suitable information. At pore scale, for example, the micro-CT images show considerable insights into pore space structures and play valuable role in porous media characterization. The consequence of all geological heterogeneities is a great deal of uncertainty in dynamic performance of porous media which can be investigated using percolation theory. The main percolation quantities include the connected pore...
Highly conductive self-electrical stimuli core-shell conduit based on PVDF-chitosan–gelatin filled with in-situ gellan gum as a possible candidate for nerve regeneration: a rheological, electrical, and structural study
, Article Applied Nanoscience (Switzerland) ; Volume 11, Issue 8 , 2021 , Pages 2199-2213 ; 21905509 (ISSN) ; Ramazani Saadatabadi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
In the context of peripheral nerve injuries treatment, self-electrical stimuli nerve guidance conduit is a promising technique. To fabricate such structures, PVDF-chitosan–gelatin was considered for the outside walls of conduit and gellan gum containing conductive polyaniline-graphene (PAG) nanocomposite particles in the middle. PVDF-chitosan–gelatin nanofibers were prepared using the dual-electrospinning method and highly conductive binary-doped polyaniline-graphene was synthesized by chemical oxidative polymerization in the presence of aniline and sodium dodecyl sulfate. The morphology and chemical structure of nanofibers and PAG were characterized using SEM and FTIR analyses. The...
Thermo-oxidative degradation during sintering of polyethylene particles
, Article Journal of Applied Polymer Science ; Volume 138, Issue 19 , 2021 ; 00218995 (ISSN) ; Pircheraghi, G ; Sharif University of Technology
John Wiley and Sons Inc
2021
Abstract
Polymer sintering is not only a well-established procedure for producing functional polymeric parts, but it is also the basis for the relatively new additive manufacturing technique, selective laser sintering. Although studying the impact of thermo-oxidative degradation during sintering has significant practical importance, few studies have focused on this aspect of the sintering process. In the present work, we have investigated the active thermo-oxidative degradation mechanisms during sintering of high-density polyethylene (HDPE) particles, the conditions that promote them, and their respective impact on the morphological evolution of the polyethylene particles. To perform a comprehensive...
Investigation on reactive flow through porous media by quadtree Lattice Boltzmann
, Article Journal of Natural Gas Science and Engineering ; Volume 104 , 2022 ; 18755100 (ISSN) ; Ayatollahi, S ; Jamshidi, S ; Raoof, A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this study, in order to investigate the effect of the underlying pore-scale processes on continuum scale simulations of porous media dissolution, we improve the standard Lattice Boltzmann method using Quadtree grid refinement approach to simulate fluid flow and reactive transport through large domain sizes. Our results have shown considerable computational improvements up to 80% in simulation time together with increased numerical accuracy. The results and the added value of the new approach are discussed using comparison of our model with the conventional LBM. Moreover, we have applied a systematic analysis by increasing complexity levels and starting from fluid flow and continuing with...
Pore network modeling of nanoporous ceramic membrane for hydrogen separation
, Article Separation Science and Technology ; Volume 45, Issue 14 , Sep , 2010 , Pages 2028-2038 ; 01496395 (ISSN) ; Farhadi, F ; Sharif University of Technology
2010
Abstract
Pore network modeling of porous media has this advantage that can consider the pore structure incorporating any desired details, but it has not been studied sufficiently. In addition, most studies are limited to mathematical modeling only which need validation. In the present study, this approach was applied to hydrogen separation from syngas by nanoporous ceramic membrane to predict the membrane permeance theoretically based on its pore structure. Gas transport through nanoporous membrane was modeled with the aim of a 2D network model. A dusty gas model was used for gas transport in the individual pores. Model validation showed that the model predictions are in good agreement with the...
Pore structure evolution during sintering of HDPE particles
, Article Polymer ; Volume 183 , 2019 ; 00323861 (ISSN) ; Pircheraghi, G ; Foudazi, R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Sintering is a processing technique in which loose particles consolidate at elevated temperatures to form porous monoliths. Sintering is also a critical stage in recent additive manufacturing method like selective laser sintering. In this study, using an affordable alternative to X-ray tomography technique, we analyze the pore structure evolution in sintered parts made of nascent high-density polyethylene (HDPE) particles in terms of pore surface genus and pore surface curvature. Also, we investigate the underlying microstructural development and macroscopic properties of sintered parts. It is observed that pore structure and macroscopic permeability are strongly influenced by the...
Insights into the pore-scale mechanisms of formation damage induced by drilling fluid and its control by silica nanoparticles
, Article Energy and Fuels ; Volume 34, Issue 6 , 20 May , 2020 , Pages 6904-6919 ; Mahani, H ; Sharif University of Technology
American Chemical Society
2020
Abstract
The formation damage (FD) caused by the invasion of drilling fluid severely affects reservoir performance during production. Most of the published research studies which address this type of FD have been carried out at the core or field scale. Thus, the main aim of the paper is to investigate the pore-scale mechanisms of FD induced by drilling fluids and their control with silica nanoparticles (NPs) using a microfluidic approach. The proper identification of the mechanisms of FD can lead to the proper selection of NP type and concentration as well as a suitable method to remediate FD. The micromodel was designed in a way to closely simulate the cross-flow at the wellbore surface. A...
Thermo-oxidative degradation during sintering of polyethylene particles
, Article Journal of Applied Polymer Science ; 2020 ; Pircheraghi, G ; Sharif University of Technology
John Wiley and Sons Inc
2020
Abstract
Polymer sintering is not only a well-established procedure for producing functional polymeric parts, but it is also the basis for the relatively new additive manufacturing technique, selective laser sintering. Although studying the impact of thermo-oxidative degradation during sintering has significant practical importance, few studies have focused on this aspect of the sintering process. In the present work, we have investigated the active thermo-oxidative degradation mechanisms during sintering of high-density polyethylene (HDPE) particles, the conditions that promote them, and their respective impact on the morphological evolution of the polyethylene particles. To perform a comprehensive...
Fabrication of a novel 3D scaffold for cartilage tissue repair: In-vitro and in-vivo study
, Article Materials Science and Engineering C ; Volume 128 , 2021 ; 09284931 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Self-repairing is not an advanced ability of articular cartilage. Tissue engineering has provided a novel way for reconstructing cartilage using natural polymers because of their biocompatibility and bio-functionality. The purpose of cartilage tissue engineering is to design a scaffold with proper pore structure and similar biological and mechanical properties to the native tissue. In this study, porous scaffolds prepared from gelatin, chitosan and silk fibroin were blended with varying ratios. Between the blends of chitosan (C), gelatin (G) and silk fibroin (S), the scaffold with the weight per volume ratio of 2:2:3 (w/v) showed the most favorable and higher certain properties than the...
Effect of graphene oxide on morphological and structural properties of graphene reinforced novolac-derived carbon aerogels: A modified Quasi-Percolation Model
, Article Ceramics International ; Volume 46, Issue 8 , 2020 , Pages 11179-11188 ; Madaah Hosseini, H. M ; Pourjavadi, A ; Bahramian, A. R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Graphene reinforced polymer derived carbon (carbon/graphene) aerogels were synthesized by carbonization of novolac/graphene oxide aerogels. Novolac/graphene oxide aerogels were synthesized using solvent-saturated-vapor-atmosphere technique. To this aim, 20 wt% solution of novolac resin with 0, 2, and 5 wt% graphene oxide in 2-propanol were made and were cured in an autoclave. Wet aerogels were dried in air and were carbonized at 800 °C in nitrogen atmosphere. Eliminating the time-consuming methods of drying like supercritical and freeze drying is one of the advantages of this method of synthesis of organic aerogles. Fourier transform infrared spectroscopy, field emission scanning electron...
Self-accumulated Ag nanoparticles on mesoporous TiO2 thin film with high bactericidal activities
, Article Surface and Coatings Technology ; Volume 204, Issue 21-22 , August , 2010 , Pages 3676-3683 ; 02578972 (ISSN) ; Ghaderi, E ; Sharif University of Technology
Abstract
Antibacterial activity of sol-gel synthesized Ag-TiO2 nanocomposite layer (30nm) deposited on rough anatase (a) TiO2 thin film (~200nm in thickness) was investigated against Escherichia coli bacteria, in dark and also in exposure to UV light. The nanocomposite thin films were transparent with a surface plasmon resonance absorption band at a wavelength of 410nm. The metallic silver nanoparticles with an average diameter of 30nm and fcc crystalline structure were self-accumulated on surface of a mesoporous and aqueous TiO2 layer with a capillary pore structure having a pore radius of 3.0nm. By adding the silver nanoparticles in the TiO2 layer, recombination of the photoexcited electron-hole...