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Influence of Microstructure on Mechanical Properties and Fracture Behavior of Hybrid PP/GF/CaCO3 Composites, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar ; Bagheri, Reza
Homo-polymer of Polypropylene is a commodity thermoplastic with good physical and mechanical properties along with fair recyclability and cost. However, its application is limited in some cases, especially in automotive industry, due to a lack of toughness. One of the approaches for PP toughening is the copolymerization of PP with some ethylene co-monomers. However, existence of elastomers in this kind of polymers causes a decrease in tensile properties. Besides, glass fibers improve tensile properties of homo-and co-PP and decrease toughness of co-polymers but result in an increase for homo-polymers. A rise in expenditure of energy due to increasing the processing temperature and...
M.Sc. Thesis Sharif University of Technology ; Ejtehadi, Mohammad Reza
The study of Energy Landscape of physical systems has a key role in complex problems. In this project we have enumerated the energy landscape of a finite squared lattice spin glass with nearest neighbored interactions to study its behavior. We choose the coupling constants of this spin glass system with Heb rule. According to this rule the coupling constants are chosen in a way to make specific patterns of spin configuration as a local minimum. We have studied these spin glasses with different number of patterns. In our computation we saw a significant difference between spin glasses with odd and even number of patterns. We addressed this behavior to properties of coupling constant...
Effect of Bioglass Particle Size and Titania Morphology on the Bioactivity and Kinetics of Tissue Growth in Three-Dimensional Poly(ɛ-Caprolactone) Scaffolds with Controlled Pore Structure Produced by 3D-Printing Process, Ph.D. Dissertation Sharif University of Technology ; Bagheri, Reza ; Vossoughi, Manouchehr ; Simchi, Abdolreza
Polycaprolactone (PCL) scaffolds and its composites containing bioactive glass particles (45S5) and TiO2 nanostructures with pre-defined and controlled external and internal architecture were prepared via an indirect three-dimensional (3D) printing process. The scaffolds had an interconnected structure with macro- (400-500 μm) and micro- (~25 μm) pores. Bioactivity, mechanical behavior and kinetics of tissue growth in 3D scaffolds were studied. The size effect of biogactive glass particles (6 μm, 250 nm, <100 nm) and morphology of titania nanostructures (spherical, tube, leaf-like, and flower-like particles) were elaborated. The biogactive glass particles with different sizes were prepared...
Electrophoretic Deposition of Alginate-Bioglass-Nanodiamond Nanocomposites and Evolution of their Bioactivity, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdollreza
Recently, diamond nanoparticles have attracted interest for biomedical applications such as drug delivery, targeted cancer therapies, fabrication of tissue scaffolds and biosensors. In the present work, elecrophoretic deposition (EPD) of nanodiamond-bioactive glass-alginate nanocomposite was studied. In vitro bioactivity and biocompatibility of the nanocomposite were evaluated in simulated body fluid (SBF) and by MTT assay. The EPD process was performed under different conditions in order to obtain a uniform coating on the surface of 316L stainless steel substrate. The stability of the suspension was determined via optical sedimentation method and zeta potential analysis. It was found that...
Synthesis & Properties of Nd-doped Glass-ceramics in the SiO2-CaO-MgO System from Sol-gel Method Used as Solid Lasers
Sharif University of Technology
In this study, SiO2-CaO-MgO galsses and glass-ceramic powder doped with Nd3+ were synthesized with sol-gel method. Tetraethylorthosilicate (TEOS), Ca(NO3)2.4H2O, Mg(NO3)2.6H2O, Nd(NO3)3.6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with STA, XRD, DRS, PL, FTIR and SEM analysis. From XRD patterns of glass samples, the role of dopant was introduced as intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that the bredigite and akermanite crystals were formed in glass matrix. The band gap energy of samples were calculated from DRS analysis and were seen with increasing the dopant...
M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah
Bioactive glasses are able to bond to soft and hard tissues in living body and their application as coating on metallic implants like 316L stainless steel has two important effects: (1) intimate link between bone and materials and (2) corrosion protection of metallic implant in body fluid and protection from tissues in front of corrosion products. Therefore, in this research, 45S5 bioactive glass prepared via sol- gel method was dip coated on 316L stainless steel substrates and its characteristics was investigated.Results of phase analysis showed that by sintering 45S5 bioglass at 600 ˚C for 5 h, an amorph sample with small amount of Na2Ca2Si3O9 was obtained. So, the bioglass coated samples...
Experimental Investigation of Mechanical Behavior of Structural Concrete with Combination of Waste Glass and Silica Fume, M.Sc. Thesis Sharif University of Technology ; Khaloo, Ali Reza
Concrete is the second most structural material in the world. So attention and promotion of the concrete mix design with respect to variable issues and requirements, is very important. On the other hand, these days environment and its pollution has become very popular discussion. Waste-glass which is produced by human products is one of the environmental pollutants. In this thesis it replaces some aggregate in concrete and it can reduce the level of this material in the world. Also we study effects of silica-fume as cement replacement and properties enhancer in our concrete mix design and see how it can ...
Evaluation of Controlled Drug Release Chitosan-based Coatings on Titanium Implants: Microstructure, Bioactivity and Biocompatibility, Ph.D. Dissertation Sharif University of Technology ; Simchi, Abdolreza
Implant-associated infections are one of the most serious complications in orthopaedic and trauma surgery as it may result in poor functional outcome, implant failure, chronic osteomyelitis or even death. Great concerns have been taken to reduce implant-associated infections through progressing in operating standards, minimizing the possibility of contamination during surgery, reducing the establishment of infection by perioperative antibiotic prophylaxis, and confining of pathogenic strains by patient isolation. In spite of these preventions, the percentage of postoperative infections is still rising. Composite coatings with bone-bioactivity and drug-eluting capacity are considered as...
M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar ; Karimi Sabet, Javad
Continuous separation processes in microfluidic devices experienced a steep rise in attention during the last two decades. Among the different separation processes, liquid-liquid extraction especially benefits from the short molecular diffusion distance and large specific interfacial area, as these are advantageous for effective mass transport. In the present study, glass-based microfluidic devices have been fabricated utilizing laser ablation and wet chemical etching methods then experiments and numerical simulation were carried out to investigate hydrodynamic behavior of fluid flow in Y-junction microfluidic. In order to achieve phase separation at the end of the microchannel, a phase...
Surface Modification of Metallic Implants and Improvement of their Biological Properties in Presence of Bioactive Ceramic Nanoparticles, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam
By consideration of increasing demands to use implants and efforts to get technical knowledge and localization of this implants, considerable research in this field is needed. Therefore, presentation of a coating which is able to provide parameters needed for an acceptable implant is the aim of this study. In this direction, modification of surface of metallic implants in order to achieve nanotubes of titanium oxide, with the purpose of providing biocompatibility was done. On the other hand, because chronic infection of the implant’s surrounding is one of the main important reasons in rejection of implants, 〖TiO〗_2 nanotubes as a drug carrier were used in order to solve this problem. So,...
Fabrication and Characterization of Electron Transport and Buffer Layer Thin Films, Employing Sputtering Method, for All-Oxide Solar Cells, M.Sc. Thesis Sharif University of Technology ; Iraji zad, Azam ; Mohammadpour, Raheleh
In this study, transparent conductive thin film of Aluminum doped ZnO (ZnO:Al) have been fabricated thorough RF sputtering. The main goal of fabrication of these layers is achieving thin films with minimum resistivity and maximum optical transparency in visible range of spectrum employing as transparent electrodes and buffer layer at the entirely oxidized solar cells. To achieve the suitable structure, various parameters including pressure, power and the thickness of the deposition and annealing on morphologies of thin film has been investigated. According to these results, thin film of ZnO:Al has the transparency of 80% in the visible light range . Doping of ZnO with Aluminum caused...
Chitosan–Bioactive Glass Composite Coating on Nd-Fe-B Magnetic Alloy Substrate by Electrophoretic Deposition, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah
This research work deals with application of poly-saccharide to improve coating process of bioactive ceramic composite on aNd-Fe-B magnetic alloy substrate. Bioactive glass particles were synthesized through a sol-gel process and coated in the form of composite with poly-saccharide onto a magnetic substrate by electrophoretic deposition technique. Stable suspensions of 0.5 gr/lit polysaccharide polymer-ceramic were prepared using bioactive glass particles (<1µm), acetic acid 1%. The influence of added water to ethanol, pH and tri-ethanol-amine (TEA) additive on suspension stability, deposition rate and coating’s structure was investigated. It was shown that by increasing the water to ethanol...
M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rohollah
Metallic glasses (MG) are a group of materials that have unique properties such as high yielding strength and high elastic deformation. Because of limitation in the production of these materials, a few industrial materials of MG have been made so far. A few of binary alloys, like binary alloys made of Cu-Zr, have high Glass Forming Ability (GFA) in medium cooling rates. Between two binary systems of Cu-Zr and Ni-Zr, although constituent elements in aspect of atomic radius, electronic structure, physical properties, phase diagrams and intermetallic compounds are so similar to each other, but GFA between them are very different. For example, in Cu-Zr system there are compounds, such as...
Computer Simulation of Ultrasonic Waves in Cybernetic Glasses in Order to Increasing Spatial Resolution of Blinds, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad
Eyesight is one of the most important tools for humans to communicate with environment and consequently, blindness or poor eyesight results in unsatisfactory effect on life quality. Owing to the importance of the sense and to assist to the patients, this thesis aims to design and assemble cybernetic glasses using ultrasound waves. To this end, firstly, the notion of waves focusing on ultrasound waves is described and reactions of human hearing system to the waves are studied. Then, the transducers as a key device are introduced. Afterward, bat sense system to communicate with environment which is based ultrasound waves is described. Next, attenuation effects on ultrasound wave pressures are...
YSZ Coating on Ferritic Stainless Steel Interconnect through Sol-Gel Method and Studying its Reaction with Glass Sealant in SOFC, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali ; Nemati, Ali
Solid oxide fuel cells are used to convert solid-state energy to direct electrical current by electrochemistry mixing a gas fuel and an oxidant in an oxide electrolyte. One of the most interesting aspects of this field for the researchers is the reaction between the metal interconnect and the glass sealant. In the current research, deposition of the YSZ coating onto the metal interconnect in order to impede the reaction with glass sealant and prohibition of its oxidation in oxidizing/reducing environment in high temperature, was mainly investigated. Effect of applying YSZ Thin layer in the intersection of Crofer steel and glass sealant on strength and chemical durability of these two...
Ph.D. Dissertation Sharif University of Technology ; Aashuri, Hossein ; Tavakoli, Rouhollah
Bulk metallic glasses (BMGs), in contrast to conventional crystalline materials, are defined as metals with an amorphous and disordered atomic-scale structure. Due to the absence of dislocations and grain boundaries, BMGs have considerably unique mechanical properties such as high strength and elastic strain, high wear resistance and desirable corrosion resistance. However, they generally suffer from poor plasticity caused by an inhomogeneous deformation which leads to catastrophic failure by localization of strain into narrow regions, known as shear bands. This factor has extremely restricted their application as advanced structural materials. Furthermore, the recently discovered phenomenon...
Ph.D. Dissertation Sharif University of Technology ; Aashuri, Hosien ; Tavakoli, Roholah
In this work, structures of Cu-Zr bulk metallic glasses at atomic scale were studied by molecular dynamics simulation. Bulk metallic glasses have high glass form ability, which makes it possible to more effectively examine the relationship between structure and properties in glassy materials. Due to this reason, this family of materials has been selected in this research. Voronoi tessellation method, coordination number analysis, short-range order examination, glass transition temperature and pair distribution function have been selected to investigate the structure in atomic scale. Results show that full icosahedron (with the highest five-fold symmetry) and some distorted icosahedra have...
Molecular Dynamics Study of Tungsten and Iron Addition on the Glass Formability of Cobalt-based Electrodeposited Coatings, M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rouhollah
Recent research suggests that the electrochemical deposition of cobalt-based binary alloys, such as cobalt-tungsten and cobalt-iron, can lead to the formation of amorphous structures in the coatings. Theoretical studies suggest that these structures are equivalent to structures created by the melt cooling of the alloy at speeds of about 〖10〗^10 Kelvin per second. The formation of a glass phase can significantly increase the abrasion resistance and corrosion resistance of these coatings. Empirical studies show that the ability of the glass to become glassy, or more precisely, the transition from crystalline to amorphous, is largely a function of the chemical composition. Simulation of...
M.Sc. Thesis Sharif University of Technology ; Ashouri, Hossein ; Tavakoli, Rouhulla
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...
Investigation of Mechanical Properties of Glass-Ceramic Sealant for Solid Oxide Fuel/Electrolysis Cells, Ph.D. Dissertation Sharif University of Technology ; Kokabi, Amir Hossein ; Faghihi-Sani, Mohammad Ali ; Abdoli, Hamid
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...