Sharif Digital Repository

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... 

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... 

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... 

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... 

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,... 

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... 

In order to prevent deterioration of metallic interconnects in solid oxide fuel cells (SOFC), while interacting with glass-ceramic sealant, a nickel electroplated ferritic stainless steel (UNS 430) was used. After applying a layer of powdered glass (SiO2-B2O3-Al2O3-Na2O-BaO-K2O) with thickness around 300-450 μm on the ferritic stainless steel sheets with dimansion of 0.5 × 60 × 60 mm and 0.5 × 10 × 10 mm, samples were heated at temperatures between 770-850 °C and durations of 1 to 15 hours. To evaluate the effect of the Ni layer, two types of sample (only sanded and only electropolished) were also submitted to the same process, and their results were compared with the coated samples. XRF,... 

The Fe-Ni-Co alloy to borosilicate glass seals have been used for many years as hermetic and electrically insulating seals. It is not only excellent in thermal expansion matching but also in good wettability and bond strength too. Oxidation of Kovar was performed in Water vapor, Saturated Nitrogen and N2-H2-H2O atmosphere in tube furnace. Oxide layer composition and thickness changed by varying in oxidation temperature and time. XRD analysis showed different Iron oxides in oxide layer, FeO, Fe3O4 and Fe2O3. However in the third atmosphere no Hematite observed. Increasing oxidation temperature and time result in increasing sample weight gains and roughness. Oxide layer microstructure also was... 

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... 

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... 

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... 

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... 

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... 

Wound healing is a complex and regular process. It makes more challenge when the volume of wound exudate becomes uncontrollable. To solve this problem, hydrofiber wound dressings which contain carboxymethyl cellulose fibers are being used. Fast absorption and keeping the moisture in balance specially in chronic wounds, is one of the major features of hydrofiber wound dressings. In this research, which was conducted with the aim of investigating the synergy effect of active glasses and Hydrofiber commercial wound dressing for the healing of skin wounds, especially chronic wounds, the sol-gel method has been used to synthesize bioactive glasses based on borosilicate, replacing a part of CaO... 

In this work, we have used a 3D printer and unidirectional ice-templating technique in conjunction, to fabricate a novel composite scaffold to facilitate local osteochondral defects tissue regeneration with a cell-free approach. Using ice-templating to induce radially-aligned porosity formation in type I bovine collagen is known to expedite host cells' migration into the scaffold which their ECM secretion shifts cellular milieu toward that of its neighboring tissue layer. We used numerical analysis to design and optimize appropriate freeze-casting mold, finding the optimum value for pin height and metal slab depth to be 4mm and 14mm, respectively. Collagen content equivalent to 2%w/v was... 

Understanding biological systems requires extensive knowledge of individual parameters, and to study the processes of cell differentiation and cell behavior, a suitable environment must be created with the physiological conditions of the human body. For this purpose, with the knowledge of microfluidics, a microenvironment can be provided to study the behavior of cells on a small scale. The use of bone tissue model microfluidic chips is an alternative and new method in which it is possible to study the behavior of cells to differentiate into bone and to examine the toxicity of drugs, which in itself can help in the effective and successful treatment of these cases show. Therefore, in this... 

Based on numerous laboratory and field evidence, low-salinity waterflooding or engineered salinity waterflooding can lead to enhanced oil production. According to the literature, the mechanisms involved in this process can be divided into two general categories: fluid-fluid interactions and solid-liquid interactions. These mechanisms are caused by intermolecular and electrostatic forces at the rock and fluid interfaces. The most important controlling factor of the electrostatic forces is the concentration of ions at/near fluids-rock interface. Therefore, improving the concentration of ions causes a shift in wettability toward a more water-wetting state, eventually leading to increased oil... 

PMMA bone cement lacks biodegradability and the ability to bond with surrounding bone tissue. Therefore, the development of a new generation of bioactive bone cements that are biodegradable and possess adequate mechanical properties as well as desirable setting time is receiving remarkable interest.In this study, we have developed novel mineral-based bioactive bone cements. Our mineral bioactive bone cements were composed of Calcium Sulfate Hemihydrate, Bioactive Glass, and Tricalcium Silicate. Firstly, a binary system composed of Calcium Sulfate Hemihydrate and Bioactive Glass was optimized based on mechanical and setting behavior. Secondly, Tricalcium Silicate was added to the powder phase... 

The following dissertation discusses Ionic Liquids (ILs) as an alternative to commercial surfactants for use in the Enhanced Oil Recovery process. Ionic Liquids came to researchers’ attention due to their environmental nature and their tolerance for high temperatures and salinity. In this work, firstly, an extensive literature review is carried out, and then, experiments are designed and performed to evaluate ILs’ surface activity and performance in a lab-scale EOR set-up. The Ionic Liquids used in this work consist of three types of methylimidazolium nitrate, [MIM]+[NO3]-, with three different alkyl chain lengths. This combination, and specifically the effect of nitrate anions on EOR and... 

Formation damage in petroleum engineering is an important and fundamental phenomenon. During drilling operation, penetration of either the solid phase of drilling fluid or the base-fluid into the porous medium, reduces the permeability of the formation. While most experiments in the literature have focused on core-scale and beyond, there is lack of pore-scale studies. Moreover, presence of fractures has an undeniable effect on the extent of formation damage. Thus, the main objective of this dissertation is to investigate the effects of fractures on the severity of formation damage caused by the water-based drilling fluid and the mechanisms of formation damage at the pore scale, using glass...