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    Synthesis of Magnesium Aluminate Spinel Nanoparticles Using Chemical Method and Investigation of the Effect of Zirconia on Spinel Composites Properties

    , M.Sc. Thesis Sharif University of Technology Maddahi, Vahid (Author) ; Nemati, Ali (Supervisor)
    In this research, a powder containing magnesium-aluminate spinel particles is prepared based on co-precipitation method and 5% , 10%, 15% and 20% zirconia-contained composites are produced as second phase from the synthesized powder. The raw materials used in the synthesis comprise hexa-hydrated magnesium nitrate, nona-hydrated aluminum nitrate, ammonium bicarbonate, 28% ammonium solution and distilled water. The properties of the powder is then investigated using STA, XRD and SEM tests. Also, XRD and SEM analyses as well as triple point flexural strength and Vickers hardness tests are carried out in order to investigate the effect of adding zirconia to the powders. The variations of the... 

    , M.Sc. Thesis Sharif University of Technology Kashani, Massoud (Author) ; Moghaddam, Hassan (Supervisor)
    The paper presents the results nonlinear analysis of steel base plates subjected to different combinations of axial and bending forces. The bending forces range from small moments representing small eccentricities to large moments from seismic actions. The results of analyses proved to be in good agreement with experiments. The parameters investigated in this study are as follows: distribution of strain and stresses in the concrete foundation and the steel plate, the strains and stresses in the tensile anchorage bolts, the location of neutral curve under the base plate, the centre of compressional reaction forces in concrete, the flextural rigidity of the base plate connection, and the axial... 

    Investigation on Nonlinear Behavior of base Plates with Triangular Hardener under Axial Load and Bending Moment

    , M.Sc. Thesis Sharif University of Technology Sheibani, Mehran (Author) ; Moghaddam, Hassan (Supervisor)
    The paper presents the results of nonlinear analysis of steel base plates subjected to different combinations of axial and bending forces. The bending forces range from small moments representing small eccentricities to large moments from seismic actions. The results of nonlinear analysis are done on three samples of the column base plate with large moment, small moment and compression axial force are compared to the results of the code. The parameters investigated in this study are as follows: distribution of strain and stresses in the concrete foundation and the steel plate, the strains and stresses in the tensile anchorage bolts, the location of neutral curve under the base plate, the... 

    The Investigation of Additive Elements Ti, Cr on Structure and Some Mechanical Properties of Micro and Nano Composites of Iron Aluminide/Alumina

    , M.Sc. Thesis Sharif University of Technology Khazraiyan Vafadar, Ali (Author) ; Abachi, Parvin (Supervisor) ; Salahi, Esmaeil (Supervisor)
    In this experiment, first the Fe and Al powders with atomic ratio of 25 and 75 were mixed by mechanical alloying process. After obtaining the optimum conditions of milling, nano structural Fe3Al powder was synthesized by 40 hours alloying with a Ball to Powder Ratio (BPR) of 20:1. The synthesized powder was then milled with different weight ratios of titanium and Cr for 30 hours. Morphological changes, size of powder particles, lattice strain, grain size and phase transitions were studied for different powders in different time spans during milling process by means of scanning electron microscopy, X-ray diffraction and grain size analyzer. The smallest grain size gained for milled powder... 

    Mechanical performance of self-compacting concrete reinforced with steel fibers

    , Article Construction and Building Materials ; Volume 51 , 31 January , 2014 , Pages 179-186 ; ISSN: 09500618 Khaloo, A ; Raisi, E. M ; Hosseini, P ; Tahsiri, H ; Sharif University of Technology
    Self-compacting concrete (SCC) is a highly-workable concrete that without any vibration or impact and under its own weight fills the formwork, and it also passes easily through small spaces between rebars. In this paper, the effect of steel fibers on rheological properties, compressive strength, splitting tensile strength, flexural strength, and flexural toughness of SCC specimens, using four different steel fiber volume fractions (0.5%, 1%, 1.5%, and 2%), were investigated. Two mix designs with strengths of 40 MPa (medium strength) and 60 MPa (high strength) were considered. Rheological properties were determined through slump flow time and diameter, L-box, and V-funnel flow time tests.... 

    Investigation on cristobalite crystallization in silica-based ceramic cores for investment casting

    , Article Journal of the European Ceramic Society ; Volume 33, Issue 15-16 , 2013 , Pages 3397-3402 ; 09552219 (ISSN) Kazemi, A ; Faghihi Sani, M. A ; Alizadeh, H. R ; Sharif University of Technology
    In this work, cristobalite crystallization and its effects on mechanical and chemical behaviour of injection moulded silica-based ceramic cores were investigated. In order to simulate casting process condition, the sintered samples at 1220 °C were also heated up to 1430 °C. Flexural strength test was carried out on both sintered and heat treated samples. Chemical resistance of the cores was evaluated by leaching the samples inside 43. wt% KOH solution at its boiling point. Phase evolution and microstructure were investigated by thermal analyses (DTA and DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). Results showed that cristobalite was... 

    Effect of Zirconia Content and Powder Processing on Mechanical Properties of Gelcasted ZTA Composite

    , Article Transactions of the Indian Ceramic Society ; Volume 72, Issue 3 , May , 2013 , Pages 175-181 ; 0371750X (ISSN) Khoshkalam, M ; Faghihi Sani, M. A ; Nojoomi, A ; Sharif University of Technology
    Addition of fine zirconia particles in the alumina matrix in order to produce ZTA composite is a well-known method for improving the mechanical properties of alumina ceramics such as flexural strength and fracture toughness. Increasing homogeneity and reducing alumina grain size are two key factors for achieving proper mechanical properties in this ceramic matrix composite. In this work two batches of ZTA powder precursor were prepared through mixing of alumina and zirconia by ball milling and in situ synthesis of ZTA composite via solution combustion method. The bending strength testing samples were fabricated through gel-casting process. The effects of different powder processing methods... 

    Flexural behavior of concrete beams reinforced with high volume steel fibers

    , Article ISEC 2013 - 7th International Structural Engineering and Construction Conference: New Developments in Structural Engineering and Construction ; 2013 , Pages 1031-1036 ; 9810753551 (ISBN) ; 9789810753559 (ISBN) Khaloo, A ; Jahromi, H. S ; Mohammadian, A ; Yazdani S ; Singh A ; Sharif University of Technology
    This paper presents the results of an experimental study on the flexural behavior of ten 10 × 15 × 120 (cm) steel reinforced high strength concrete beams under deflection control loading conditions. Test variable includes volumetric percentage of steel fibers (0%, 1.5%, 3%, 4%, 5%). The plain concrete strength was 30MPa. The monotonic concentrated load was applied at the center of the beam, the relative deflection was measured, and demec points were used to determine curvature of the beam. Load-deflection and moment-curvature diagrams have been obtained and plotted for each beam individually. Test results indicate that higher fiber content considerably improves flexural behavior and provides... 

    Experimental investigation of square RC column strengthened with near surface mounted GFRP bars subjected to axial and cyclic lateral loads

    , Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1361-1371 ; 10263098 (ISSN) Dayhim, N ; Nicknam, A ; Barkhordari, M. A ; Hosseini, A ; Mehdizad, S ; Sharif University of Technology
    Sharif University of Technology  2013
    This article is intended to highlight the effectiveness of longitudinal Glass Fiber Reinforced Polymer (GFRP) bars in combination with GFRP sheets on the flexural capacity of Reinforced Concrete (RC) columns. Seven half-scale RC columns including five strengthened and two control unstrengthened specimens were experimentally tested under axial and cyclic lateral loads. The strengthened columns with two different longitudinal GFRP bar ratios were tested under three different axial load levels. The flexural strength and ductility parameters of the specimens were calculated by obtaining their deformations and measuring the loads from load cells. The experimental results indicate significant... 

    Closed-cell Al alloy composite foams: Production and characterization

    , Article Materials and Design ; Volume 42 , December , 2012 , Pages 8-12 ; 02641275 (ISSN) Malekjafarian, M ; Sadrnezhaad, S. K ; Sharif University of Technology
    Foamy Al alloy SiCp composites of different densities ranging from 0.4 to 0.7g/cm3 were manufactured by melt-foaming process, which consisted of direct CaCO3 addition into the molten A356 aluminum bath. Mechanical properties and morphological observations indicated that the three-stage deformation mechanism of typical cellular foams is dominant in the produced A356 aluminum foams. Middle-stage stress plateau shrinkage plus compressive strength and bending stress enhancements were observed in denser foams. With the same Al/SiCp ratio, energy absorption ability and plastic collapse strength of the closed-cell foams were increased with the foam density. Doubling cell-face bending effects... 

    Improving the performance of cement-based composites containing superabsorbent polymers by utilization of nano-SiO2 particles

    , Article Materials and Design ; Volume 42 , 2012 , Pages 94-101 ; 02641275 (ISSN) Pourjavadi, A ; Fakoorpoor, S. M ; Khaloo, A ; Hosseini, P ; Sharif University of Technology
    The application of superabsorbent polymer (SAP) as an internal curing agent for cement based composites results in benefits such as reduced autogenous shrinkage and cracking. However, a reduction in compressive and flexural strength usually occurs due to the empty voids remained in the matrix after deswelling of SAP particles. Nanoparticles are good candidates for improving the mechanical performance of cementitious materials, due to their multiple mechanisms of action, not the least their high pozzolanic activity.In the present work, the capability of amorphous nano-SiO2 (NS) as the most widely used nanoparticle in cementitious materials, for retrieving mechanical properties of... 

    Production of waste bio-fiber cement-based composites reinforced with nano-SiO 2 particles as a substitute for asbestos cement composites

    , Article Construction and Building Materials ; Volume 31 , 2012 , Pages 105-111 ; 09500618 (ISSN) Hosseinpourpia, R ; Varshoee, A ; Soltani, M ; Hosseini, P ; Ziaei Tabari, H ; Sharif University of Technology
    The environmental impact of asbestos fibers on human health and their consequent safety-related problems indicate that there is a significant need to replace this material in all asbestos-containing products. Many different types of fibers have been introduced to replace asbestos fibers. In this study, the performance of silica nano-particles combined with waste paper pulp fibers (sulfite fibers) has been investigated. Different mechanical (compressive and flexural strengths and bending performance), durability (water absorption), physical (bulk density and flowability), and microstructural (scanning electron microscopy) tests were conducted to examine the properties of manufactured green... 

    Densification behavior and mechanical properties of biomimetic apatite nanocrystals

    , Article Current Nanoscience ; Volume 7, Issue 5 , 2011 , Pages 776-780 ; 15734137 (ISSN) Eskandari, A ; Aminzare, M ; Hassani, H ; Barounian, H ; Hesaraki, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    Nanocrystalline hydroxyapatite (nHA) of 50 nm average diameter and length to diameter ratio of >3 was synthesized by biomimetic method. Non-isothermal sintering improved densification behavior and mechanical properties of apatite to 0.88 maximum fractional density, 70MPa bending strength, 148MPa compressive strength and 2.53GPa microhardness at sintering temperature of 1250°C. Higher sintering temperatures resulted in the decomposition of the apatite and in-situ biphasic calcium phosphate HAP/TCP formation. This process lowered apatite densification and weakened mechanical properties of the sintered specimen. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and field emission... 

    The Effect of Temperature and Rotational Speed on Structure and Mechanical Properties of Cast Cu Base Alloy (Cu-Al-Si-Fe) Welded by Semisolid Stir Joining Method

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 46, Issue 12 , 2015 , Pages 5782-5788 ; 10735623 (ISSN) Ferasat, K ; Aashuri, H ; Kokabi, A. H ; Shafizadeh, M ; Nikzad, S ; Sharif University of Technology
    Semisolid stir joining has been under deliberation as a possible method for joining of copper alloys. In this study, the effect of temperature and rotational speed of stirrer on macrostructure evaluation and mechanical properties of samples were investigated. Optical microscopy and X-ray diffraction were performed for macro and microstructural analysis. A uniform micro-hardness profile was attained by semisolid stir joining method. The ultimate shear strength and bending strength of welded samples were improved in comparison with the cast sample. There is also lower area porosity in welded samples than the cast metal. The mechanical properties were improved by increasing temperature and... 

    Experimental study of RC jacketed and CFRP strengthened RC beams

    , Article Construction and Building Materials ; Volume 95 , October , 2015 , Pages 476-485 ; 09500618 (ISSN) Tahsiri, H ; Sedehi, O ; Khaloo, A ; Raisi, E. M ; Sharif University of Technology
    Elsevier Ltd  2015
    This paper presents the results of an experimental study on retrofitting RC beams using FRP strengthening and RC jacketing. Three-point loadings are applied to twelve strengthened beams and three reference specimens to put the two techniques into perspective. Formation of first cracks, FRP debonding, and onset of concrete crushing are compared and discussed. Load-deflection behavior, failure modes, and crack propagation patterns are studied extensively. The experiments demonstrate that the RC jacketed beams exhibit a flexural failure identical to the reference beams. However, the FRP strengthened beams fail in a relatively small deflection due to the premature FRP debonding. Furthermore, the... 

    Investigation of hydroelastic effect in analysis of high-speed craft

    , Article Ships and Offshore Structures ; Volume 11, Issue 1 , 2016 , Pages 16-24 ; 17445302 (ISSN) Zamanirad, S ; Seif, M. S ; Tabeshpur, M. R ; Yaakob, O ; Sharif University of Technology
    Taylor and Francis Ltd  2016
    Hydroelastic effect in bottom slamming problem of high-speed craft is one of the most challenging issues in structural design. In this paper, numerical method is used to investigate the hydroelastic effect in bottom-water impact analysis of high-speed monohull craft. Slamming with two viewpoints of rigid and elastic structures (hydroelastic effect) is modelled by coupled computational fluid dynamic (CFD) and finite element method (FEM) techniques. The results showed that considering hydroelastic effect, especially in high-impact speed, reduces the structural deformations and stresses compared with quasi-statistic analysis. The effect of different parameters, such as boundary condition, plate... 

    Densification and properties of Fe2O3 nanoparticles added CaO refractories

    , Article Ceramics International ; 2016 ; 02728842 (ISSN) Ghasemi Kahrizsangi, S ; Nemati, A ; Shahraki, A ; Farooghi, M ; Sharif University of Technology
    Elsevier Ltd 
    Up to 8wt. % of Nano-iron oxide was added to CaO refractory matrix. The crystalline phases and microstructure characteristics of specimens sintered at 1650°C for 5h in an electric furnace were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The physical properties are reported in terms of bulk density, apparent porosity and hydration resistance. The mechanical behavior was studied by a cold crushing strength (CCS) and flexural strength at 1200°C test. As a result, it was found that the presence of Nano-iron oxide in the CaO refractory matrix induced 2CaO.Fe2O3 (C2F), CaO.Fe2O3 (CF) and 3CaO.Al2O3 (C3A) phase's formation, which improved the sintering... 

    The influence of silica nanoparticles addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites

    , Article Ceramics International ; Volume 43, Issue 18 , 2017 , Pages 16780-16786 ; 02728842 (ISSN) Gheisari Dehsheikh, H ; Ghasemi Kahrizsangi, S ; Sharif University of Technology
    The high hydration potential of CaO and MgO phases restricted the application of Mag-Dol refractory composites. In this study, the impact of nano-silica (SiO2) addition on the physical, mechanical, thermo-mechanical as well as microstructure of Mag-Dol refractory composites is investigated. Mag-Dol compositions were prepared by using calcined dolomite and magnesite particles (micron, 0–1, 1–3, 3–5, and 5–8 mm), liquid resin, and 0, 0.5, 1, 1.5, 2, and 2.5 wt% nano SiO2 as additives. Specimens were heated up to 1650 °C for the 3 h soaking period. Fired specimens were characterized by physical (apparent porosity, bulk density, and hydration resistance), mechanical (cold crushing strength), and... 

    Behavior of polymer concrete beam/pile confined with CFRP sleeves

    , Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-8 ; 15376494 (ISSN) Toufigh, V ; Toufigh, V ; Saadatmanesh, H ; Ahmari, S ; Kabiri, E ; Sharif University of Technology
    This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity. © 2017 Taylor... 

    Predicting delamination in multilayer composite circuit boards with bonded microelectronic components

    , Article Engineering Fracture Mechanics ; 2017 ; 00137944 (ISSN) Akbari, S ; Nourani, A ; Spelt, J. K ; Sharif University of Technology
    Elsevier Ltd  2017
    The present work developed a mixed-mode cohesive zone model (CZM) with a mode I failure criterion to predict the delamination bending loads of multilayer, composite printed circuit boards (PCBs) assembled with soldered ball grid array (BGA) components that were reinforced with an underfill epoxy adhesive. Two different delamination modes were observed in these microelectronic assemblies: delamination at the interface between the solder mask and the first conducting layer of the PCB, and PCB subsurface delamination at the interface between the epoxy and glass fibers of one of the prepreg layers. The cohesive parameters for each of the two crack paths were obtained from fracture tests of...