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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 ; Nemati, Ali (Supervisor)
Abstract
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 ; Moghaddam, Hassan (Supervisor)
Abstract
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...
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 ; Abachi, Parvin (Supervisor) ; Salahi, Esmaeil (Supervisor)
Abstract
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...
Investigation on Nonlinear Behavior of base Plates with Triangular Hardener under Axial Load and Bending Moment
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
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 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) ; Ghasemi Kahrizsangi, S ; Sharif University of Technology
Abstract
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...
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) ; Aashuri, H ; Kokabi, A. H ; Shafizadeh, M ; Nikzad, S ; Sharif University of Technology
Abstract
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...
The effect of mixing molar ratios and sand particles on microstructure and mechanical properties of metakaolin-based geopolymers
, Article Materials Chemistry and Physics ; Volume 240 , 2020 ; Nemati, A ; Khodabandeh, A. R ; Baghshahi, S ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study the influence of the molar ratios such as SiO2:Al2O3:Na2O:H2O, as well as the sand particles on the mechanical performance, shrinkage and microstructure of metakaolin based geopolymers was studied. Considering different content of the reactive silica and alumina in metakaolin, forty eight different compositions were prepared. The proper condition for achieving the highest mechanical performance as well as less structural defects by tailoring the curing condition, molar ratios and addition of sand particles are presented. Special attention was paid to the incorporation of sand particles up to 70 wt% on the microstructure, shrinkage and mechanical properties of metakaolin based...
Strength of SCLC recycle springs and fibers concrete subject to high temperatures
, Article Structural Concrete ; 2021 ; 14644177 (ISSN) ; Toufigh, V ; Sharif University of Technology
John Wiley and Sons Inc
2021
Abstract
In this article, the self-compacting lightweight concretes (SCLC) with different fibers were prepared and exposed to elevated temperatures, and their mechanical properties were investigated. Three types of fibers were steel fibers (SF), polypropylene fibers (PPF), and metal springs with a volume fraction of 0.4%. One hundred and fifty cylindrical specimens were prepared, and the compression, tensile and flexural tests were carried out on them after exposure to high temperatures ranging from 25 to 700°C. The findings indicate that incorporation of steel fibers and springs enhanced the compressive strength of concrete by 20% compared to the control specimen. Meanwhile, the polypropylene fibers...
Seismic shear strengthening of R/C columns with ferrocement jacket
, Article Cement and Concrete Composites ; Volume 27, Issue 7-8 , 2005 , Pages 834-842 ; 09589465 (ISSN) ; Morshed, R ; Sharif University of Technology
2005
Abstract
This paper presents results of an experimental study to evaluate a retrofit technique for strengthening shear deficient short concrete columns. In this technique a ferrocement jacket reinforced with expanded steel meshes is used for retrofitting. Six short concrete columns, including four strengthened specimens, were tested. Specimens were under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross, A g, and the concrete compressive strength, fc′. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching their nominal calculated flexural...
Seismic shear strengthening of R/C beams and columns with expanded steel meshes
, Article Structural Engineering and Mechanics ; Volume 21, Issue 3 , 2005 , Pages 333-350 ; 12254568 (ISSN) ; Kazemi, M. T ; Sharif University of Technology
Techno-Press
2005
Abstract
This paper presents results of an experimental study to evaluate a new retrofit technique for strengthening shear deficient short concrete beams and columns. In this technique a mortar jacket reinforced with expanded steel meshes is used for retrofitting. Twelve short reinforced concrete specimens, including eight retrofitted ones, were tested. Six specimens were tested under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross section, Ag, and the concrete compressive strength, fc′. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching...
Rubberized alkali-activated slag mortar reinforced with polypropylene fibres for application in lightweight thermal insulating materials
, Article Construction and Building Materials ; 2020 ; Shoaei, P ; Shariati, M ; Ameri, F ; Musaeei, H. R ; Behforouz, B ; de Brito, J ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Every year, about a thousand million tires reach the end of their service life, more than half of which are disposed of in landfills. The waste tire rubber has a great potential for application as aggregate phase in production of lightweight concrete/mortar. This study is aimed at evaluating the effects of using crumb rubber (CR) as fine aggregate at replacement ratios of 0–60% (by volume) in alkali-activated slag mortars. Furthermore, polypropylene fibre (PPF) was used at 0.5% and 1% of volume of the mix to enhance the properties of mortar mixes such as flexural strength and shrinkage behaviour. The compressive strength, flexural strength, water absorption, thermal conductivity, drying...
Rubberized alkali-activated slag mortar reinforced with polypropylene fibres for application in lightweight thermal insulating materials
, Article Construction and Building Materials ; Volume 270 , 2021 ; 09500618 (ISSN) ; Shoaei, P ; Shariati, M ; Ameri, F ; Musaeei, H. R ; Behforouz, B ; de Brito, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Every year, about a thousand million tires reach the end of their service life, more than half of which are disposed of in landfills. The waste tire rubber has a great potential for application as aggregate phase in production of lightweight concrete/mortar. This study is aimed at evaluating the effects of using crumb rubber (CR) as fine aggregate at replacement ratios of 0–60% (by volume) in alkali-activated slag mortars. Furthermore, polypropylene fibre (PPF) was used at 0.5% and 1% of volume of the mix to enhance the properties of mortar mixes such as flexural strength and shrinkage behaviour. The compressive strength, flexural strength, water absorption, thermal conductivity, drying...
Response of a novel beam-to-column/brace-to-frame connection to monotonic and cyclic shear loading
, Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 9 June 2008 through 13 June 2008, Berlin ; Volume 2 , 2008 , Pages 609-618 ; 9780791848197 (ISBN) ; England, G. L ; Abazarsa, F ; Ocean, Offshore, and Arctic Engineering Division; ASME ; Sharif University of Technology
2008
Abstract
A new universal structural joint was developed. While in bending it has a high rotational capacity, which can be accompanied by large bending stiffness and strength, in shear, it also has a very high shear deformation capacity, which can again be accompanied with large shear stiffness and strength. While the former characteristic makes it a good candidate for being used as a beam-to-column joint, the latter makes it highly applicable in connecting braces of a braced frame to the frame members. The experimental study carried out previously on this joint, concentrated on the performance of its steel specimens under 'monotonie' shear loading as well as that of its aluminium specimens under both...
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) ; Varshoee, A ; Soltani, M ; Hosseini, P ; Ziaei Tabari, H ; Sharif University of Technology
2012
Abstract
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...
Predicting delamination in multilayer composite circuit boards with bonded microelectronic components
, Article Engineering Fracture Mechanics ; 2017 ; 00137944 (ISSN) ; Nourani, A ; Spelt, J. K ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
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...
Predicting delamination in multilayer composite circuit boards with bonded microelectronic components
, Article Engineering Fracture Mechanics ; Volume 187 , 2018 , Pages 225-240 ; 00137944 (ISSN) ; Nourani, A ; Spelt, J. K ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
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...
Mixed shear-flexural (VM) hinge element and its applications
, Article Scientia Iranica ; Volume 14, Issue 3 , 2007 , Pages 193-204 ; 10263098 (ISSN) ; Erfani, S ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
In the present paper, a mixed, shear-flexural (VM) hinge element, with zero or nonzero length, for using in frames, has been introduced, where shear-flexural interaction has been considered. The element has the capability of modeling flexural yielding, shear yielding and their interaction in frames, subjected to all kinds of monotonic or cyclic loadings. The inelastic shear and flexural deformations and tangential stiffnesses are considered by using the multi-surfaces approach with dissimilar yield surfaces and by a stiffness matrix with nonzero off-diagonal components. A new kinematics hardening rule and, also, a new non-associated flow rule are introduced. The mixed hinge element can be...
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 ; Raisi, E. M ; Hosseini, P ; Tahsiri, H ; Sharif University of Technology
Abstract
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....
Mechanical characteristics of cement paste in the presence of carbon nanotubes and silica oxide nanoparticles: An experimental study
, Article Materials ; Volume 14, Issue 6 , 2021 ; 19961944 (ISSN) ; Farhangi, V ; Farani, M. R ; Joshaghani, A ; Zadehmohamad, M ; Ahmadzadeh, M ; Sharif University of Technology
MDPI AG
2021
Abstract
Considering the remarkable characteristics of nanomaterials, previous research studies investigated the effects of incorporating different types of these materials on improving the concrete properties. However, further studies are required to evaluate the complementary hybridization and synergistic influence of nanomaterials. In this research, the combined effect of adding nano silica particles (NS) and multi-walled carbon nanotubes (MWCNT) on enhancing both the compressive and flexural strengths of the cement paste was investigated. Moreover, the morphology of the interface between cement paste and aggregates was studied by scanning electron microscopy (SEM). The mixtures were prepared...
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) ; Faghihi Sani, M. A ; Alizadeh, H. R ; Sharif University of Technology
2013
Abstract
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...