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    Drug nano-particles formation by supercritical rapid expansion method; operational condition effects investigation

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 1 , 2011 , Pages 7-15 ; 10219986 (ISSN) Zabihi, F ; Akbarnejad, M. M ; Vaziri Yazdi, A ; Arjomand, M ; Safekordi, A. A ; Sharif University of Technology
    2011
    Abstract
    Dissolution pressure and nozzle temperature effects on particle size and distribution were investigated for RESS (Rapid Expansion of Supercritical Solution) process. Supercritical CO2 was used as solvent and Ibuprofen was applied as the model component in all runs. The resulting Ibuprofen nano-particles (about 50 nm in optimized runs) were analyzed by SEM and laser diffraction particle size analyzer systems. Results show that in low supercritical pressure ranges, depending on the solvent and solid component properties (Lower than 105 bar for Ibuprofen-CO2 system), nozzle temperature should be as low as possible (80-90 °C for Ibuprofen-CO2 system). In the other hand in high supercritical... 

    Investigation on the particle size and shape of iron ore pellet feed using ball mill and HPGR grinding methods

    , Article Physicochemical Problems of Mineral Processing ; Volume 53, Issue 2 , 2017 , Pages 908-919 ; 16431049 (ISSN) Abazarpoor, A ; Halali, M ; Sharif University of Technology
    Oficyna Wydawnicza Politechniki Wroclawskiej  2017
    Abstract
    An effect of a grinding method, that is ball mill and high pressure grinding rolls (HPGR), on the particle size, specific surface area and particle shape of an iron ore concentrate was studied. The particle size distribution was meticulously examined by sieve, laser and image analyses. To measure the specific surface area of particles, Brunauer-Emmett-Teller (BET) and Blaine methods were used. It was found that for samples having equal Blaine specific surface areas numbers, the amount of fine particles produced in HPGR was higher than that produced in a ball mill. A higher surface area was observed from HPGR treatment in comparison to ball mill grinding, provided by a higher porosity,... 

    Deformation, Yield and fracture of elastomer-modified polypropylene

    , Article Journal of Applied Polymer Science ; Volume 90, Issue 14 , 2003 , Pages 3767-3779 ; 00218995 (ISSN) Zebarjad, S. M ; Bagheri, R ; Seyed Reihani, S. M ; Lazzeri, A ; Sharif University of Technology
    2003
    Abstract
    In recent decades, great attention has been devoted to the toughening of isotactic poly(propylene) (PP) with elastomers such as ethylene-propylene rubber (EPR). The most important reasons for this interest are the moderate cost and favorable properties of PP. This article is focused on the role of EPR in the deformation and fracture mechanism of PP/EPR blends with different volume fractions of elastomer phase. Differential scanning calorimetry (DSC), tensile tests, and microscopy techniques were used in this study. The fracture mechanism of isotactic PP toughened by EPR (PP/EPR) has also been studied by three point bending (3-PB) and four point bending (4-PB) tests. Rubber particle... 

    A simplified model for the flow inside cascade impactor

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 7 A , November , 2013 ; 9780791856314 (ISBN) Mehr, S. M. N ; Sohrabi, S ; Falsafi, P ; Gorji, P ; ASME ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2013
    Abstract
    In this paper we developed a new mathematical model for the flow inside cascade impactors and via this simplified model, we determined the particle size distribution by a fast and low cost computational method. Using cascade impactors for determining the particle size distribution, one can use comprehensive CFD methods to fully simulate the particle traces. Although the results from those CFD analyses can be very accurate, usually that is not a time and cost efficient routine. In contrast, we showed that by using our proposed calculation we can estimate the particle size distribution very fast and yet with the slight error -comparing to the results from CFD method. Cascade impactors are... 

    Evaluation of relationship among filler amount, degree of conversion, and cytotoxicity: approaching performance enhancement novel design for dental Bis-GMA/UDMA/TEGDMA composite

    , Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 66, Issue 16 , 2017 , Pages 844-852 ; 00914037 (ISSN) Najafi, H ; Akbari, B ; Najafi, F ; Abrishamkar, A ; Ramedani, A ; Yazdanpanah, A ; Sharif University of Technology
    Abstract
    Dental composites of A2 color using Bis-GMA, urethane dimethacrylate and triethyleneglycol dimethycrylate resins (70/20/10), and silica filler (70 wt%, 75 wt%, and 80 wt%), a hybrid of nano- and microsilica particles, are made and subjected to the following tests: Fourier transform infrared spectroscopy (FTIR), particle size analyzer, scanning electron microscope (SEM), and also cytotoxicity. FTIR results show that an increase in filler amount yields to a decrease in degree of conversion. Therefore, there should be a compromise between degree of conversion and the filler amount. SEM images manifest the uniformity of silica particles. It is shown from the cytotoxicity tests that as the... 

    HPGR effect on the particle size and shape of iron ore pellet feed using response surface methodology

    , Article Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy ; 2017 , Pages 1-9 ; 03719553 (ISSN) Abazarpoor, A ; Halali, M ; Hejazi, R ; Saghaeian, M ; Sharif University of Technology
    Taylor and Francis Ltd  2017
    Abstract
    In this study the effect of HPGR operational parameters on the dimensional properties of pellet feed was examined and optimized using factorial methodology. The operational parameters considered include feed moisture, specific pressure and roll speed. For this study, size and shape of particles with Blaine number in the range 1800–2200 cm2 g−1 was thoroughly investigated. It was deduced that increasing the specific pressure and decreasing the roll speed would result in reduction of D80 but would increase the Blaine number. The circularity, aspect ratio and roughness descriptors of the particles were measured by SEM micrographs and image analysis software. It was observed that particles... 

    HPGR effect on the particle size and shape of iron ore pellet feed using response surface methodology

    , Article Mineral Processing and Extractive Metallurgy: Transactions of the Institute of Mining and Metallurgy ; Volume 127, Issue 1 , 2018 , Pages 40-48 ; 25726641 (ISSN) Abazarpoor, A ; Halali, M ; Hejazi, R ; Saghaeian, M ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    In this study the effect of HPGR operational parameters on the dimensional properties of pellet feed was examined and optimized using factorial methodology. The operational parameters considered include feed moisture, specific pressure and roll speed. For this study, size and shape of particles with Blaine number in the range 1800–2200 cm2g−1 was thoroughly investigated. It was deduced that increasing the specific pressure and decreasing the roll speed would result in reduction of D80 but would increase the Blaine number. The circularity, aspect ratio and roughness descriptors of the particles were measured by SEM micrographs and image analysis software. It was observed that particles tended... 

    Study on mechanical properties of ternary blended concrete containing two different sizes of nano-SiO2

    , Article Composites Part B: Engineering ; Volume 167 , 2019 , Pages 20-24 ; 13598368 (ISSN) Nazerigivi, A ; Najigivi, A ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    The aim of this study was to investigate the influences of combination of the two different SiO2 nanoparticles (15 nm and 80 nm) on compressive, flexural and tensile strength of ternary blended concrete. SiO2 nanoparticles with two different sizes of 15 and 80 nm have been used as a partial cement replacement by 0.5, 1.0, 1.5 and 2.0 wt.% in 16 different proportions of mixture followed by curing in lime solution for 7, 28 and 90 days. The results indicate that in all curing ages in lime solution specimens with 2.0% of 15 nm plus 1.5% of 80 nm cement replacement achieved higher mechanical properties. The continuous cement paste with the lowest delicate zones might be due to the fact of quick... 

    Effect of iron particle size on the diffusion bonding of Fe-5%Cu powder compact to wrought carbon steels

    , Article Materials and Design ; Volume 29, Issue 2 , 2008 , Pages 411-417 ; 02613069 (ISSN) Fillabi, M. G ; Simchi, A ; Kokabi, A. H ; Sharif University of Technology
    Elsevier Ltd  2008
    Abstract
    In the present work, diffusion bonding of Fe-5%Cu powder compact to wrought carbon steels was studied. Effects of iron particle size and carbon content of the solid component on the bond strength, which is the maximum shear stress required to obtain separation at the interface, were investigated. Atomized iron powders with the mean particle size of 36, 56, 90, 106, and 148 μm and wrought steels with 0.22, 0.33, and 0.47 wt% carbon content were used. To evaluate the bonding zone, "ring shear" test, standard metallography technique, and micro-hardness test were employed. The results showed a profound effect of carbon content of the solid steel on the diffusion bonding process. It is suggested... 

    Modeling and Simulation of Particle Size Distribution in Batch Crystallization Processes

    , M.Sc. Thesis Sharif University of Technology Adeli Koudehi, Babak (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    In this research, it was tried to present a suitable environment for simulation of crystallization systems. Chapter one presented a survey on crystallization systems, its application, operating methods, and its phenomena. Chapter two presented mechanism and kinetic of phenomena that occur in crystallization systems, in detail, and mathematical models to modeling this systems are implied. In chapter three, that is the simulation result section, firstly, it focused on solution methods to solve population balance equation, that explains the particle size distribution, and its validation, secondly, the simulation results in a case study was compared with those obtained from finite volume method.... 

    Simulation and experimental evaluation of initiator and surfactant concentrations and temperature effects on styrene conversion and polymer particle size distribution in batch emulsion polymerization

    , Article Iranian Polymer Journal (English Edition) ; Volume 19, Issue 8 , Aug , 2010 , Pages 599-614 ; 10261265 (ISSN) Abedini, H ; Shahrokhi, M ; Sharif University of Technology
    Abstract
    Effects of initiator and surfactant concentrations and temperature on styrene conversion and polymer particle size distribution (PSD) in a batch emulsion polymerization are investigated through simulation and experimental studies. The detailed model based on population balance (zero-one model), accounting for nucleation, growth and coagulation phenomena has been used for prediction of particle size distribution. In checking the effect of initiator concentration on final PSD, it was noticed that when critical micelle concentration (CMC) is kept constant, the model cannot predict PSD very well. Thus, a correlation for calculating critical micelle concentration has been proposed and... 

    Optimization of particle size and specific surface area of pellet feed in dry ball mill using central composite design

    , Article Indian Journal of Science and Technology ; Volume 9, Issue 44 , 2016 ; 09746846 (ISSN) Abazarpoor, A ; Halali, M ; Sharif University of Technology
    Indian Society for Education and Environment  2016
    Abstract
    Objective: The dimensional properties of iron ore pellet feed including specific surface area and particle size distribution in the ball mill was studied using response surface area method. Methods/Statistical analysis: The effect of the operational parameters of dry ball mill including ball charge (20-40%), grinding time (30-50 min) and balling distribution (Small, Mixed and Large) on dimensional properties of pellet feed was meticulously examined and optimized using response surface methodology based on Central Composite Design (CCD). Responses were 80% passing size (D80) and Blaine (BL). A total of 30 grinding experiments were designed and carried out in the CCD method. Regression models... 

    Empirical models for minimum fluidization velocity of particles with different size distribution in tapered fluidized beds

    , Article Powder Technology ; Volume 338 , 2018 , Pages 563-575 ; 00325910 (ISSN) Rasteh, M ; Farhadi, F ; Ahmadi, G ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    The particle size distribution (PSD) is known as an important parameter affecting the hydrodynamic behavior of fluidized beds. In this study, extensive experimental data for fluidization of particles with different PSDs in tapered fluidized beds was presented. In the experimentations, three Geldart B powders with four average diameters and various PSDs were used. The experimental results showed that the minimum fluidization velocity (Umf) for particles with flat and binary size distributions were roughly the same; moreover, they were up to 25% larger than the Umf values for narrow cut particle size distribution. The Umf values for Gaussian size distribution were lower than those of narrow... 

    Synthesis and polymorph controlling of calcite and aragonite calcium carbonate nanoparticles in a confined impinging-jets reactor

    , Article Chemical Engineering and Processing - Process Intensification ; 2020 Adavi, K ; Molaei Dehkordi, A ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this article, a confined-impinging-jets reactor (CIJR) was designed and tested successfully for the synthesis of calcium carbonate nanoparticles using the reactive precipitation method. The proposed CIJR comprised of two opposed nozzles placed in a cylindrical chamber. Effects of various operating and design parameters such as supersaturation, feed flow rate, nozzle diameter, reactor diameter, operating temperature, and surface-active agents on the mean particle size, particle size distribution, and the polymorphs of calcium carbonate nanoparticles were investigated carefully. By changing the supersaturation, reactor diameter, jets velocity, operating temperature, and the nozzle diameter,... 

    Microinjection moulding of 316L/17-4PH and 316L/Fe powders for fabrication of magnetic-nonmagnetic bimetals

    , Article Journal of Materials Processing Technology ; Volume 200, Issue 1-3 , 2008 , Pages 259-264 ; 09240136 (ISSN) Imgrund, Ph ; Rota, A ; Simchi, A ; Sharif University of Technology
    2008
    Abstract
    In the investigations presented here, the feasibility of producing magnetic-nonmagnetic bimetals made of 316L/17-4PH and 316L/Fe powders by micro-metal injection moulding process (μ-MIM) was studied. In order to achieve sound replication of small specimens with dimensions less than 1 mm, very fine powders with mean particle sizes in the range of 3-7 μm were used. A wax-polymer binder system specially designed for micro-moulding was used to make up the feedstock. The isothermal and non-isothermal sintering behaviour of the moulded components was evaluated under hydrogen atmosphere. The effect of powder-binder-ratio of the feedstock, master alloy addition, and sintering conditions on the... 

    Inferential closed-loop control of particle size distribution for styrene emulsion polymerization

    , Article Chemical Engineering Science ; Volume 63, Issue 9 , 2008 , Pages 2378-2390 ; 00092509 (ISSN) Abedini, H ; Shahrokhi, M ; Sharif University of Technology
    2008
    Abstract
    In this work, a new control strategy for controlling the particle size distribution (PSD) in emulsion polymerization has been proposed. It is shown that the desired PSD can be achieved by controlling the free surfactant concentration which in turn can be done by manipulating the surfactant feed rate. Simulation results show that the closed-loop control of free surfactant concentration results in a better control of PSD compared to open-loop control strategy, in presence of model mismatch and disturbances. Since the on-line measuring of ionic free surfactant concentration is difficult, conductivity which is related to it is measured instead and used for control purposes. The closed-loop... 

    Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media

    , Article Applied Physics A: Materials Science and Processing ; Volume 84, Issue 1-2 , 2006 , Pages 215-219 ; 09478396 (ISSN) Tilaki, R. M ; Irajizad, A ; Mahdavi, S. M ; Sharif University of Technology
    2006
    Abstract
    We studied the effects of the surrounding liquid environment on the size and optical properties of silver nanoparticles prepared by laser ablation by a pulsed Nd:YAG laser operated at 1.064 nm. The silver targets used were kept in acetone, water and ethanol. TEM observations and optical extinction were employed for characterization of particle size, shape and optical properties, respectively. Nano silver in acetone showed a narrow size distribution with a mean size of 5 nm and the colloidal solution was stable. In deionised water a rather narrow size distribution with a mean size of 13 nm was observed and nanoparticles were precipitated slowly after about two weeks. In ethanol, a broadening... 

    Europium-doped yttrium silicate nanoparticles embedded in a porous SiO 2 matrix

    , Article Nanotechnology ; Volume 15, Issue 11 , 2004 , Pages 1549-1553 ; 09574484 (ISSN) Taghavinia, N ; Lerondel, G ; Makino, H ; Yao, T ; Sharif University of Technology
    2004
    Abstract
    Europium-doped yttrium silicate nanoparticles were grown inside a porous silicon oxide matrix by chemical impregnation of porous silicon layers, followed by heat treatments. The average size of the nanoparticles is 50 nm and they are dispersed almost uniformly within the whole porous layer. Local composition measurements demonstrate that Y and Eu are found only in nanoparticles, indicating a good phase separation efficiency. There is indirect evidence that yttrium silicate nanoparticles are nucleated around Eu ions. The crystalline phase of the particles is pure α-Y2Si2O7, with no trace of Y2O3 or Y2SiO5 or other Y2Si2O7 polymorphs. Structural purity is an advantage for this method, as in... 

    Fractal behaviour of flow of inhomogeneous fluids over smooth inclined surfaces

    , Article Journal of Physics Condensed Matter ; Volume 16, Issue 15 , 2004 , Pages 2497-2505 ; 09538984 (ISSN) Maleki-Jirsaraei, N ; Ghane Motlagh, B ; Baradaran, S ; Shekarian, E ; Rouhani, S ; Sharif University of Technology
    2004
    Abstract
    Patterns formed by the flow of an inhomogeneous fluid (suspension) over a smooth inclined surface were studied. It was observed that fractal patterns form. There exists a threshold angle for the inclination above which global fractal patterns are formed. This angle depends on the particle size of the suspension. We observed that there are two fractal dimensions for these patterns, depending on the area from which the pattern is extracted. If the pattern is taken from the top which only consists of the beginning steps of the pattern forming, one finds two fractal dimensions, i.e. 1.35-1.45 and 1.6-1.7, in which the first one is dominant while, if the entire pattern is taken, then a fractal... 

    The role of particle size on the laser sintering of iron powder

    , Article Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science ; Volume 35, Issue 5 , 2004 , Pages 937-948 ; 10735615 (ISSN) Simchi, A ; Sharif University of Technology
    Minerals, Metals and Materials Society  2004
    Abstract
    The effects of powder particle size on the densification and microstructure of iron powder in the direct laser sintering process were investigated. Iron powders with particle sizes ranging from 10 to 200 μm were used. It was found that the sintered density increases as the laser energy input is increased. There is, however, a saturation level at which higher density cannot be obtained even at very intensive energy input. This saturation density increases as the size of the iron particles decreases. Meanwhile fine powders with narrow particle size distributions have a tendency toward agglomeration, and coarse powders with broad particle size distributions have a tendency toward segregation,...