Sharif Digital Repository

In this study effect of various mullite contents, as reinforcement phase, on phase combination, fracture surface and mechanical propertiese of hydroxyapatite- mullite composite has been investigated.
The used hydroxyapatite powder was synthesized through acid- base route and further calcination. XRD results demonstrated partially decomposition of HA in to β- TCP and CaO during the calcination. SEM image of the prepared HA powder showed that they were spherical and agglomarated.
The mixed HA with various amounts of the ball- milled mullite (10- 40 wt%)were pressed and sintered at 1350°C for 2h. Dominant phase in all composite samplese after sintering was Ca9Al(PO4)7.
Phase... 

In this thesis, macrostructural evolutions in dissimilar TLP bonding of as-cast nickel based supperalloy IN792 to wrought HX was investigated. In the first step of this study solidification behavior of Ni-Cr-Fe-Si-B (MBF-15) interlayer in presence of HX as base metal at 1120 °C was surveyed. In second step, bonding of HX/HX, IN792/IN792 and HX/IN792 systems with MBF-15 interlayer at 1120 °C and different times were studied and isothermal solidification time and factors that affect this stage were discussed. In third step, synchronization of dissimilar bonding with standard heat treatment cycle of IN792 was investigated and effect of this cycle on aging response of different zones, isothermal... 

Polypropylene block copolymer is used in different industries like pipe productions. This copolymer has proper mechanical properties, specially it has good impact strength, but in some applications it’s elastic modulus (stiffness) is not enough and that leads to some problemes in servise. Nucleating agents influence crystalline structure and properties and also the mechanical properties by controlling the crystallization process. Nanoparticles also have a beneficial effects on physical and mechanical properties. In this study, the effect of adding two types of α-phase nucleating agents (commercial names NA11 and DMDBS) in the form of masterbatch wt 5% with a carrier of polypropylene block... 

Mechanosensitive membrane channels are indispensable part of cells that sense and respond to mechanical signals. Hence, malfunction of these channels may cause various diseases. Despite numerous studies of these channels, there are still many unanswered questions surrounding these channels and their gating mechanism. Although there have been valuable experimental studies in this field, the need for modelling and computational studies are still felt since experiments face many limitations in this area. Thus, a channel that its crystallographic structure has been recently determined was chosen and studied using computational tools. In this study, gating of the channel under surface tension has... 

With increasing awareness, artificial materials have been replaced by recyclable materials and green materials. In the manufacture of composites, natural and degradable materials are also used. The main object of this research is the fabrication of natural fiber reinforced composites. In this research, fibers are used that are cultivated in the country. Also, the effect of fiber length, fiber mass percentage and fiber correction on composite properties was investigated. The fiber length factor is at two levels of 5 mm and 9 mm, the percentage of fiber mass is in four levels of 5%, 10%, 12.5% and 15%, and the factor for correction of fibers is also in two groups of modified fibers and... 

Now a days, the ability of measuring the mechanical properties of the living cells in in experiments has been increased. Experiments shows that the stem cells could alter their faith in different mechanical situations, but an integrated model about this phenomenon in literature has not been introduced yet. In this research thesis s minimal cell model (MMC) is developed to capture the behavior of the cells on substrates with varying mechanical properties and morphologies, MMC consists of large scale models for outer membrane of the cell and nuclear envelope, cytoplasmic area, chromatin fibers and Extra cellular matrix. Each component of the MMC will be placed in an integrated software to... 

Since the increase in the strength of metals resulting from the severe plastic deformation (SPD) leads to a reduction in their ductility, recently, several studies have been carried out on the deformation of metals. One if the goals has been increasing the ductility while maintaining the strength. In this project, copper is undergone severe plastic deformation in a constrained groove pressing (CGP) process. According to previous studies, it has been determined that with an optimal annealing process, not only the strength is not decreased, but also it is slightly increased and also the ductility is enhanced. Thus, in order to improve the surface of copper after CGP and also optimize its... 

Properties of biomaterials, especially in application as planting, can be controlled and optimized by alloying and hardening sedimentation. In recent years, the study on the simultaneous improvement of mechanical properties, toughness and corrosion behavior of magnesium composite by carbon nanotubes (CNTs) is very limited. In this study, the behavior of mechanical properties and corrosion of magnesium alloy composites with different percentages of CNTs have been investigated. The production of magnesium alloy composite by powder metallurgy and aging process have been used as effective methods for improving mechanical properties and increasing the corrosion resistance of magnesium alloys. For... 

FE simulations have been widely used to investigate the response of the brain tissue in various circumstances. The accuracy of the material models critically affects the results of the numerical simulation. However, despite the numerous studies aiming for the material modeling of the brain, there is still divergence between the results reported in the literature. A part of this discrepancy is due to the inherent difference between samples. Nonetheless, another part of it is resulted from the differences between testing protocols used by researchers. In some protocols multiple mechanical tests are performed on each sample. Enough recovery time should be considered between consecutive test... 

Equal Channel Angular Pressing (ECAP) is one of the most applicable severe plastic deformation procedures (SPD) which results in improvement of strength and ductility through grain refinement. WE43 magnesium alloy belongs to a group of alloys for medical industry because of its good biocompatibility. In this study, equal channel angular pressing was performed at different temperatures, strain rates and number of passes on strip-shape samples to achieve proper mechanical properties. Tensile properties, hardness and microstructural evolutions were evaluated and the results were analyzed according to the EDS test. Results shows that at 380 ℃ and 440 ℃ grain refinement was accomplished by... 

Severe Plastic Deformation (SPD) has been used as an effective approach to access fine grain (FG) and ultra-fine grain (UFG) materials.the Temperature of SPD is a dominant parameter to controlling ultimate properties. SPD at room-temperature and the high temperature was used widely in literature but the low-temperature process (sub-zero and cryogenic temperatures) was not used comparably. In this study, Low-temperature Multi-Directional Forging (LMDF) was applied on commercially pure aluminum and room-temperature MDF (RMDF) was attained for contrast temperature effects, and resulting in more fine grains. The grain refinement was attributed to the fragmentation process with a limitation in... 

Metallic glasses have been applied in industry owing to their attractive mechanical, physical, and chemical properties. such as high electrical resistivity, soft-type superconductivity, good magnetic softness, high strength and large elastic strain. These unusual properties make the amorphous alloys potentially useful for various applications, which originate from the intrinsic random atomic configuration. but their plasticity is low and this disadvantage limites their applicable range as a engineering material. In this study we try to improve plasticity of metallic glasses by structural rejuvenation. Structural rejuvenation in metallic glasses by a thermal process (i.e. through recovery... 

The structural integrity of the sealing material is critical for the reliability of solid oxide fuel/electrolysis stacks. In this study, the mechanical properties of a rapid crystallizing glass of BaO-CaO-SiO2 system were evaluated. The crystallization as a determining factor in the mechanical behavior of the glass-ceramic sealant was investigated via high-temperature X-Ray diffraction spectrometer. Three- and four-point bending tests were carried out to measure the flexural strength (σ) of sealant material bars and head-to-head joined specimens at room- and high-temperatures. In addition, the elastic modulus (E) was measured by impulse excitation test up to 900 ºC. Also, the indentation... 

The A-286 superalloy is an iron-nickel base alloy having properties such as oxidation resistance and high mechanical strength. In addition, good producibility and high workability are the important properties of this alloy. In the present work dynamic restoration mechanism of A-286 supper alloy during thermo-mechanical processing has been studied. The aim is to verify the dominant restoration mechanism in different deformation conditions and also to determine the desire deformation parameters for hot rolling. In this regard, utilizing compression test in the range of 950 to 1100ºC and strain rate of 0.001 to 1 per second, the strain-stress curve for this alloy was obtained. After correction... 

Articular cartilage has limited repair capability following traumatic injuries and current methods of treatment remain inefficient. Reconstructing cartilage provides a new way for cartilage repair and natural polymers are often used as scaffold because of their biocompatibility and biofunctionality. The goal of cartilage tissue engineering is to design a scaffold with proper pore structure and similar mechanical properties to the native tissue. In this study Porous scaffolds prepared from silk fibroin, chitosan and gelatin blends with varying ratio of silk fibroin and gelatin by freeze drying method were characterized for physicochemical, mechanical and biological properties. Among the... 

It is known that Fluoride ions strongly affect bone mineralization and formation. In the present study, the engineered bone tissue scaffolds are fabricated using silk fibroin (SF) and flouridated TiO2 nanoparticles. TiO2 nanoparticles are modified by fluoride ions, and different levels (0, 5, 10, 15 and 20 wt.%) of the fluoridated TiO2 nanoparticles (TiO2-F) were subsequently added to the SF matrix through phase separation method to prepare silk fibroin/flouridated TiO2 nanocomposite scaffolds (SF/TiO2-F). Phase structure, functinal groups, morphology and mechanical properties of the obtained scaffolds were evaluated by X-ray difraction method (XRD), Fourier transform infrared spectroscopy... 

One of the most important concerns in food industry is decreasing the contamination of food and increasing their shelf life. Antimicrobial/antioxidant packaging, an active packaging concept, can be considered an extremely challenging technology that could have a significant impact on shelf-life extension and food safety of meat and meat products. Due to harmfulness of chemical preservatives, their use has been limited and therefore natural antimicrobial/antioxidant agents have become more popular. Propolis is a natural resinous substance, with a high polyphenol content, produced by honeybees and characterized by antimicrobial, anti-inflammatory and antioxidant properties, which make it... 

In this research, Al-20Si-5Fe-2X (X=Cu,Ni,Cr) alloys were produced by gas atomizing and melt spinning processes. Microstructure and growth morphology of powder and ribbons were investigated using optical microscopy, scanning electron microscopy and transmission electron microscopy, then, analyzed by solidification models. Powder and chopped ribbons were hot pressed at 400°C/250 MPa and microstructural variations, mechanical properties and thermal coefficient expansion were evaluated after consolidation. Results show that relatively high cooling rate in gas-atomized powders lead to refinement of the microstructure and formation of semi-equilibrium δ intermetallic phase. As the powder particle... 

In this research ,Al-20Si-5Fe-3Cu-1Mg-XMn alloys were produced by gas atomizing and melt spinning processes. Microstructure and growth morphology of powder and ribbons were investigated using optical microscopy , scanning electron microscopy. powders were hot pressed at 400ºC/250Mpa and microstractural variations, mechanical properties were evaluated after consolidation. Results show that relatively high cooling rate in gas-atomized powders lead to refinement of microstructure and formation of semi-equilibrium δ intermetallic phase . As the powder particle size decrease , the growth morphology changes from primary silicon + euthectic to euthectic + primary dendritic aluminum . Mn changed the... 

A severe plastic straining method, called constrained groove pressing, was used to improve the microstructure and mechanical properties of non-hardenable 3003 Al-Mn alloy. Williamson-Hall method was utilized to measure the grain size from X-ray diffraction patterns of deformed samples. The results show that ultra-fine grained 3003 alloy having grain size of 580nm can be successfully produced by constrained groove pressing at room temperature. Mechanical properties of sheets, examined by tensile test, were approximately exhibited 170% improvement in comparison with those of annealed sample. Also, comparing the achieved results with those of aluminium 1100 alloy confirmed the rapid rate of...