Search for: silicates
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    Treatment of diatomaceous earth to obtain its catalyst support

    , Article Scientia Iranica ; Volume 10, Issue 3 , 2003 , Pages 350-356 ; 10263098 (ISSN) Mahani, H ; Kazemeini, M ; Sharif University of Technology
    Sharif University of Technology  2003
    Treatment of diatomaceous earth with sulfuric acid reduces mineral and organic impurities, such as Fe2O3, Al2O3 and alkali metal oxides (CaO, MgO and Na2O). In addition, wettability and porosity of the acid-treated diatomite are greatly enhanced. Acid-treated diatomite is suitable to be used as a siliceous support for catalysts, due to high silica content (> 90%), amorphous structure with low cristobalite and quartz phases, appropriate Brunauer-Emmett-Teller surface area, high absorptive capacity, good mechanical strength after calcinations and low cost of production. In the first part of this study, the influence of temperature, sulfuric acid concentration, acid-diatomite mass ratio and... 

    Lithium iron silicate sol–gel synthesis and electrochemical investigation

    , Article Journal of Alloys and Compounds ; Volume 672 , 2016 , Pages 93-97 ; 09258388 (ISSN) Oghbaei, M ; Baniasadi, F ; Asgari, S ; Sharif University of Technology
    Elsevier Ltd 
    Li2FeSiO4 was synthesized through Sol–Gel method and the effect of calcination temperature, time and chelating agent concentration were investigated. Appropriate calcination temperature above 550 °C was determined by TG/DTA analysis. Afterward, the dried gel powder was calcined at each temperature of 650 °C, 700 °C and 750 °C for 1, 2 and 3 h. XRD studies illustrated the most appropriate calcination temperature of 700 °C for 1 h. To compare the effect of chelating agent concentration, citric acid with molar ratio of 1/3, 2/3 and 1 were used which 1/3 was determined as the best concentration. FE-SEM observation showed that mean grain is size lower than 100 nm. By using this material, a three... 

    A new study on binder performance and formulation modification of anti-corrosive primer based on ethyl silicate resin

    , Article Progress in Organic Coatings ; Volume 65, Issue 3 , 2009 , Pages 410-413 ; 03009440 (ISSN) Hoshyargar, F ; Sherafati, S. A ; Hashemi, M. M ; Sharif University of Technology
    Zinc-rich ethyl silicate coatings are quite successful in protecting steel against corrosion under severe exposing conditions. In spite of providing excellent cathodic protection to steel structure after film curing, two-component zinc-rich ethyl silicate coatings have some limitations, one of which is inadequate shelf life as a result of in-can binder gelation. In this work, the preparation steps of ethyl silicate such as pre-hydrolysis, dehydration and organometallic reactions were surveyed and herein an approach towards understanding the cause and effect relationship of the use of ingredients is presented. The effects of water and catalytic acid dosages on gel time under accelerated... 

    Mechanical properties and structure of solvent processed novolac resin/layered silicate: Development of interphase region

    , Article RSC Advances ; Volume 5, Issue 98 , Jun , 2015 , Pages 80875-80883 ; 20462069 (ISSN) Jahanmard, P ; Shojaei, A ; Sharif University of Technology
    Royal Society of Chemistry  2015
    Composites of phenol-formaldehyde (PF) resin with Closite Na+ and Closite 30B up to 20 wt% loadings were prepared by solution mixing. Tensile testing showed that both pristine and organically modified clays increased considerably the mechanical properties of PF resin at 2.5 wt% loading followed by marginal improvement or even sacrificed properties at high loadings. DMA and DSC analyses suggested development of a highly crosslinked and well adhered interphase around silicate layers. A novel three-phase model considering the interphase region was proposed to predict composite modulus. The model was successfully employed to correlate morphological characteristics and mechanical properties of... 

    Generation and collapse of bubbles in lead silicate glass

    , Article Glass Physics and Chemistry ; Volume 41, Issue 3 , May , 2015 , Pages 307-315 ; 10876596 (ISSN) Rahimi, R. A ; Sadrnezhaad, S. K ; Sharif University of Technology
    Maik Nauka Publishing / Springer SBM  2015
    Presence of bubbles affects quality of the lead silicate glass (LSG) samples. This paper presents the most recent results obtained on formation and collapse of bubbles in LSG melts. Main sources of the bubbles are dissolved gases and redox reactions. A foamy layer full of bubbles rapidly forms at top of the molten phase. Effect of viscosity and density of the melt on content and ascension rate of the bubbles are investigated. Number and mean diameter of the bubbles and thickness of the top bubbly layer are calculated from gas volume measurements and image analysis via J software  

    Evaluation of The Effect of Molecular Weight, Mixing Approach and Compatibilizer on Morphologhy and Mechanical Properties of PP/PA/Clay Nanocomposite

    , M.Sc. Thesis Sharif University of Technology Orshesh, Ziba (Author) ; Bagheri, Reza (Supervisor)
    Polypropylene/clay nanocomposites are considered as a group of widely used nanocomposites in industrial applications due to their desired properties, yet reasonable cost. However, dissimmilar chemical nature of polypropylene and clay do not allow perfect dispersion of silicate layeres in the matrix and thus restricts full advantages of these composites.An earlier investigation in this group considered solving this shortcoming through incorporation of PA6 as an intermediate phase to enhance clay platelets dispersion. The current project follows this route via studing the influence of molecular weight of the PP matrix, compatibilzer and the mixing procedure of the compound. To investigate the... 

    Incorporating multiscale micromechanical approach into PLSNs with different intercalated morphologies

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 6 , September , 2011 , Pages 3347-3359 ; 00218995 (ISSN) Yazdi, A. Z ; Bagheri, R ; Kazeminezhad, M ; Heidarian, D ; Sharif University of Technology
    The objective of the present study is to predict Young's modulus of polymer-layered silicate nanocomposites (PLSNs) containing fully intercalated structures. The particular contribution of this article is to consider the changes in structural parameters of different intercalated morphologies in vicinity of each other. These parameters include aspect ratio of intercalated stacks, number of silicate layers per stack, d-spacing between the layers, modulus of the gallery phase, and volume fraction of each intercalated morphology. To do this, the effective particle concept has been employed and combined with the Mori-Tanaka micromechanical model. It has been shown that the simultaneous effects of... 

    Study on modification of colloidal silica surface with magnesium ions

    , Article Journal of Colloid and Interface Science ; 2009 , Pages 379-383 ; 00219797 (ISSN) Karami, A ; Sharif University of Technology
    The prepared colloidal silica via ion exchange was modified by adding Mg+2 ions in the surface growth process of colloidal silica. The particle size of the modified colloidal silica was decreased by increasing the seed concentration, whereas that of colloidal silica was slightly increased as the seeds concentration exceed 15 wt%. But the trend of changes in surface area was completely reversed. Magnesium ions on surface of the modified colloidal silica were identified by the measurement of energy-dispersive X-ray spectrometry (EDS). After modifying with Mg+2 ions, the iso-electric point (IEP) of colloidal silica in pH ∼ 2 without modification, disappears over the whole pH range. © 2008... 

    On the sensitivity of the nanostructural parameters on youngg"s modulus of PLSNs in fully intercalated structures

    , Article Journal of Composite Materials ; Volume 43, Issue 24 , 2009 , Pages 2921-2941 ; 00219983 (ISSN) Zehtab Yazdi, A ; Bagheri, R ; Kazeminezhad, M ; Sharif University of Technology
    Polymer-layered silicate nanocomposites have been observed to demonstrate enhanced mechanical properties particularly at low weight fractions of silicate. Experimental and theoretical investigations reveal that numerous structural parameters strongly influence the modulus of such nanocomposites. A multiscale micromechanical model is developed which considers a wide range of different affecting parameters including the particle aspect ratio, the number of silicate layers per stack, the d-spacing ratio between the layers, the penetration of polymer chains along silicate sheets, the intercalation feature, and the particle volume fraction. The developed model illustrates the accuracy and... 

    Preparation of polyethylene/layered silicate nanocomposites using in situ polymerization approach

    , Article Macromolecular Symposia ; Volume 274, Issue 1 , December , 2008 , Pages 65-71 ; 10221360 (ISSN) Ramazani Saadatabadi, A ; Tavakolzadeh, F ; Sharif University of Technology
    In this paper, preparation of polyethylene/clay nanocomposites (PECNC) by in situ Ziegler-Natta catalyst polymerization was investigated. A Ziegler-Natta catalyst was first supported on montmorillonite (MMT) type clay and subsequently used for polymerizing ethylene. Clay and clay supported catalyst were characterized by Fourier transmission infrared and ICP method. X-ray diffraction (XRD) and transmission electron microscopy results show that silicate layers of the mineral clay in prepared nanocomposites were intercalated and exfoliated in the polymeric matrix. Differential scanning calorimetry results show that the prepared nanocomposites have higher crystallization temperature than pure... 

    Effect of ethylene-vinyl acetate copolymer on the rheological behaviour of alumino-silicate/polyethylene wax suspensions

    , Article Ceramics International ; Volume 28, Issue 5 , 2002 , Pages 507-514 ; 02728842 (ISSN) Attarian, M ; Taheri Nassaj, E ; Davami, P ; Sharif University of Technology
    Ceramic suspensions were prepared from an alumino-silicate powder, polyethylene wax (PE-wax) as binder with additions of stearic acid (SA). The ceramic powder consisted of mullite, corundum and tridymite phases. The organic binders contained 3 to 8 wt.% ethylene-vinyl acetate (EVA) and were filled with various volume fractions of ceramic powder. The yield stresses of suspensions were estimated using shear stress-shear rate data measured at 90-120 °C. The addition level of EVA was shown to have a considerable effect on the yield stress of suspensions. The effect of EVA on the flow parameters was also investigated over the temperature range of 90 to 120 °C. It was shown that the addition of 5... 

    Modeling of stiffening and strengthening in nano-layered silicate/epoxy

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 30, Issue 1 , 2017 , Pages 93-100 ; 17281431 (ISSN) Marouf, B. T ; Pearson, R. A ; Bagheri, R ; Sharif University of Technology
    The aim of this paper is to investigate adhesion property between nano-layered filler and the polymer matrix using a combination of experimental and micromechanical models as well as the changes in yield strength and stiffness of a layered silicate-filled epoxy nanocomposite. The results indicate that addition of intercalated layered silicate particles increased Young's modulus and yield strength of the epoxy resin, although the increases in stiffness and yield strength are modest, 30% and 4%, respectively. In addition, experimental results were compared with predictive stiffening and strengthening models. The rule of mixtures provides an upper bound for the modulus in these materials, while... 

    Lithium Iron Silicate Sol-Gel Synthesis and Electrochemical Investigation

    , M.Sc. Thesis Sharif University of Technology Oghbaei, Morteza (Author) ; Asgari, Sirous (Supervisor)
    Recently lithium iron silicate (Li2FeSiO4) has been used as a new cathode material for lithium ion battery. Li2FeSiO4 has such benefits like low raw material price so lower production cost, lower environmental pollution, higher safety, electro chemical and cyclic stability and high theoretical capacity of 166 mAh/g against other cathode materials like LiMn2O4, LiBNiO2, LiCoO2 and LiFePO4. In this research Li2FeSiO4 was synthesized through sol gel synthesis method and effect of chelating agent concentration, calcination temperature and time has been investigated. To determine the appropriate calcination temperature range, TG/DTA was performed. Then the dried gel powder was calcined at each... 

    Mechanical & Microstructural Evaluations of (High MFI PP/Low MFI PP)/Organoclay Nanocomposites Influence of Clay Loading, Compatibilizer Loading and Processing Sequence

    , M.Sc. Thesis Sharif University of Technology Darestani Farahani, Amir (Author) ; Bagheri, Reza (Supervisor)
    Polymer/layered silicate nanocomposites are good candidates to improve polymer matrices due to enhanced interfaces between nanoclay reinforcement and matrix. So many attempts has been done to improve fabrication methods of these nanocomposites. Polypropylene is a common used engineering material in many industrial applications (general and special). So there is many researches focused on PP/Clay nanocomposites. In this research we tried to investigate the role of clay loading, compatibilizer loading and processing sequence on clay delamination and layer dispersion. We used a blend of two different PPs with different MFI values as matrice. It seems that the blend achieves acceptable... 

    Experimental Evaluation of Different Parameters on Chemical Production of Biodiesel by Used Frying Oil

    , M.Sc. Thesis Sharif University of Technology Shiati, Peyman (Author) ; Kariminia, Hamid Reza (Supervisor)
    Biodiesel as an alternative fuel for fossil diesel has many benefits such as reducing regulated air pollutants emissions, reducing greenhouse gases emissions, being renewable, biodegradable and non-toxic. In this study, used frying oil was used as a low cost feedstock for biodiesel production by sodium silicate as an alkaline catalyst in transesterification reaction in order to optimize the conditions of biodiesel production. The factors studied were: reaction temperature, molar ratio of methanol to oil, catalyst amount and catalyst recovering. The optimum conditions of reaction obtained as follows: methanol to oil molar ratio of 7:1(mol⁄mol), catalyst amount of 3% w/w and reaction... 

    Increase the Flame Resistance of Polyurethane Foams Using Liquid Sodium Silicate (Water Glass)and Nano Silica

    , M.Sc. Thesis Sharif University of Technology Fathi, Javad (Author) ; Ramazani Saadatabadi, Ahmad (Supervisor)
    In recent years, the use of polyurethane foams has been of interest for many researchers and craftsmen. Polyurethane foams, due to their excellent properties, can be used in important applications such as advanced military industries, insulation and those requiring strength and maneuverability. The aim of this research project is to produce polyurethane / sodium silicate or nano-silica nanocomposites. Prior to the fabrication and synthesis process of polyurethane containing sodium or nano-silica, deposited silica nanoparticles were synthesized using high-rubbed sodium silicate and sulfuric acid, followed by various tests including XRD, FE-SEM and BET to verify It was done. Sodium silicate... 

    Hydrometallurgical treatment of tailings with high zinc content

    , Article Hydrometallurgy ; Volume 82, Issue 1-2 , 2006 , Pages 54-62 ; 0304386X (ISSN) Espiari, S ; Rashchi, F ; Sadrnezhaad, S. K ; Sharif University of Technology
    Zinc exists as smithsonite and hemimorphite in the lead flotation tailings from the Dandi mineral processing plant in north western Iran. In this research, zinc-rich tailings produced in the Dandi plant were characterized mineralogically and a leaching study was carried out to assess the effect of several parameters on the kinetics of zinc dissolution. Parameters studied included: sulfuric acid concentration, reaction time, temperature and slurry density. It was found that leaching is controlled by a single rate-controlling step with an activation energy of 23.5 kJ/mol. To overcome some of the filtration problems associated with polymerization of silicic acid, lime was added as a coagulant.... 

    Mechanism of deleading of silicate glass by 0.5 N HNO3

    , Article Journal of Non-Crystalline Solids ; Volume 355, Issue 48-49 , 2009 , Pages 2400-2404 ; 00223093 (ISSN) Sadrnezhaad, K ; Rahimi, R. A ; Raisali, G ; Foruzanfar, F ; Sharif University of Technology
    Mechanism of removal of lead from silicate glass containing 68.5 wt% PbO by 0.5 N HNO3 was investigated by incorporation of the chemical-analyses/weight-loss data into shrinking-core model (SCM) and minimization of the difference. Scanning electron microscopy (SEM), emission spectrometry with inductively coupled plasma (ICP), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS) were used to determine the compositional changes of the lead-silicate glass (LSG) samples. Dual inter-diffusion chemical reaction mechanisms having respective activation energies of 83.49 and 47.80 kJ/mol dominated the deleading process. © 2009 Elsevier B.V. All rights reserved  

    Simulation of Cement Hydrate by the Use of Molecular Dynamics and Developing a Reactive Forcefield for Calcium-carbonate Systems

    , M.Sc. Thesis Sharif University of Technology Zare, Siavash (Author) ; Khoei, Amir Reza (Supervisor) ; Abdolhosseini Qomi, Mohammad Javad (Co-Advisor)
    Concrete is the most used man-made material on earth, albeit is responsible for the ten percent of the carbon dioxide gas emitted by human to atmosphere. Also the most important constituent of concrete, hydrated cement, has a sophisticated structure yet its precipitation, composition, mechanical properties and morphology has been the subject of dispute among cement researchers. On the other hand, according to the increasing focus on sustainable development, design of optimum materials has become important. Several models have been proposed for the structure of cement hydrate while every model has its own advantages and disadvantages. Recently, a combinatorial model at atomic scale has been... 

    Formation of Two-Step Plasma Electrolytic Oxidation Coating On Commercially Pure Titanium and Study its Properties

    , M.Sc. Thesis Sharif University of Technology Ahmadnia, Samira (Author) ; Ghorbani, Mohammad (Supervisor)
    Improvement of biological properties by modifying the composition and morphology of the surface layer is one of the main goals of using plasma electrolytic oxidation (PEO) for coating titanium implants. The purpose of this research is formation of biocompatible coating containing calcium, phosphorus and silicon on titanium by two-step PEO method in DC, constant voltage mode. In addition to good corrosion properties of the resultant coatings in simulated body environment (SBF), Having good adhesion due to the use of electrolytes with useful elements for biological function in both step of coating process rather than acidic electrolytes which are incompatible with the body environment, this...