Sharif Digital Repository

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... 

Aseptic loosening and infection are two major problems of bone implants. Aseptic loosening occurs due to poor cell growth and poor adhesion to the implant surface over time. Bone infection at the implant site occurs mainly by the staphylococcus aureus bacteria. In some cases, infection occurs in the short term and in the early times after implantation, and in some cases, infection occurs in later times. The aim of this study is to synthesize and evaluate antibacterial coatings, while having cell growth-promoting components and cell differentiation to solve bone implant problems simultaneously. Also, the issue of bacterial resistance to antibiotics and their risks in bone implants is another... 

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... 

Today, microreactors come into focus due to their exclusive characteristics including high surface-to-volume, lower consumption of reagents and fast mixing. In this study, optimization of the Br-Li exchange reaction as a consecutive reaction using glass microreactor is investigated. To construct glass microreactor, laser ablation and thermal bonding method are utilized. In order to find the best yield and selectivity of the reaction, various parameters, such as solvent, equivalent ration of the two reagents, concentration of the reagents, residence time and flow rates of the reagents are examined. In addition, atomic force microscopy (AFM) analysis was used to determine the surface... 

Today, with the development of micro-technology in chemical reactions, the use of appropriate systems for the separation and purification of synthesized chemicals seems to be necessary. In this study, the continuous synthesis of bromide-lithium exchange reaction and the separation of organic and aqueous phase products in micro systems was investigated.The method used to construct micro-separator and micro reactor, a laser engraving technique, and thermal bonding of glass to glass.In the first step, the factors affecting the separation of organic and aqueous phase in the capillary micro-separator, such as the width of the capillary, the length of the capillary, the number of capillaries and... 

In this research, we studied the effect of compatibilizer and short glass fiber on microstructure and mechanical properties of PBT/PC blends. Fisrt, Antioxidants and sodium pyrophosphate dibasic were used to suppress transesterification in PBT/PC Blend. The results showed that best composition occur when both of them are used. In the next step, we used 3%wt MBS (methyl methacrylate-butadiene-styrene) and saw that this weight percent of this compatibilizer doesn’t useful. Moreover addition of short glass fiber to PBT/PC was examined and the results showed that mechanical properties of composite are extensively increased. Also in this step, we proved this idea that we can replace some of PBT... 

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... 

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... 

Recently, to improve the dynamic behavior of Reinforced Concrete (RC) slabs under impact load, the methods of externally bonding Glass Fiber Reinforced Polymer (GFRP) sheets to slab and internally reinforcing concrete by steel fibers have been proposed. Nevertheless, it is required to investigate the comparison between these two methods on response of RC slabs under impact loads. In this study, the influence of volume fraction of steel fibers, the number of GFRP sheet layers (one or two) and the arrangement of GFRP sheets (covering the whole or parts of surface), are examined. Performance of fourteen mm concrete slabs including one plain slab, one steel RC slab, three steel RC slabs... 

As nuclear energy continues to be used as a useful energy resource, waste management, especially management of high-level nuclear waste (HLW), will always be a major concern, as the future generations should not be deprived of the valuable benefits of this energy. Vitrification of liquid high-level radioactive waste (HLW) has received greater attention, worldwide, than any other high-level waste solidification process. The high solubility of HLW in borosilicate glass, the controllable temperature of this type of glass and its low leaching rate in repository environment, have introduced borosilicate glass as a suitable host for HLW immobilization. In this project, the immobilization of the... 

Nowadays, with the increasing number of polyethylene terephthalate wastes, the issue of its recycling has become very important. Among the problems of polyethylene terephthalate recycling are its loss of crystallinity and mechanical properties. Recycled polyethylene terephthalate does not have the properties of new polyethylene terephthalate and using its mixture with other materials is an effective way to remove its waste from nature and return it to the production cycle. The aim of this study is to produce a mixture of recycled polyethylene terephthalate with polycarbonate and glass fibers with mechanical properties such as good impact strength, which ultimately leads to the production of... 

One of the novel methods of stabilization of nuclear waste is the use of vitrification technology. In order to stabilize high level wastes (HLLW) in glass, it is required that the elements are in their oxide form. Therefore, it is necessary to evaporate the waste and turn it into a solid form so that the elements can be converted into oxide form in the calcination furnace. Hence, one of the challenges of stabilization is the optimization of evaporation and calcination conditions. In this research, the parameters affecting evaporation were first investigated. Using laboratory measurements of application: temperature (110 to 180 °C), presence of nitric acid (0.5 to 4 mol/L), ratio of zirconium... 

Ultrasonically assisted machining process has been introduced as an effective solution to improve machining quality of mechanical parts. This study aims to reduce the drilling induced delamination to increase mechanical properties of CFRP laminates. Delamination decreases the strength of laminates under static and dynamic loads. Drilling parameters (feed and spindle speed) and ultrasonic vibrations amplitude are chosen as design experiment factors. Taguchi design of experiments method is used to study the effect of input factors on drilling thrust force, delamination factor and residual strength of drilled laminates. Input factors are in three levels and Taguchi L9 array is utilized. To... 

Considering the operation of the current nuclear reactors and the country's policy to achieve 10,000 megawatts of nuclear power in the horizon of 1420, as well as the construction of research reactors, we will face a huge amount of radioactive waste in the coming years. Meanwhile, spent ion exchange resins constitute a large amount of low and intermediate level (LILW) solid radioactive waste produced from the nuclear industry. Therefore, appropriate precautionary measures should be taken for the immobilization and disposal of these radioactive wastes in order to ensure the sustainable development of the nuclear industry and the protection of the environment and human health. In this study,... 

Concrete-filled FRP tubes have gained popularity among structures in areas with harsh environmental condition. Despite their unique material properties such as resistance to corrosion, noticeable axial stiffness, and durability, FRP materials have poor resistance to elevated temperatures. This paper presents numerical investigations on the behavior and capacity of concrete-filled pultruded GFRP tubes (CFGFTs) after exposure to elevated temperatures under concentric compression. Variables in this study were the tube’s thickness of 3, 5, and 7mm, the infill concrete’s compressive strengths of 30 and 60MPa, and the exposure temperature of 25, 100, 200, 300, and 400°C. The results in this study... 

Currently, using biocompatible and injectable polymeric microcarriers as one of the efficient methods to transfer cells and active agents has gained much attention for bone regenerative medicine. However, they have some drawbacks such as weak mechanical stability and lack of mineral materials, which are the major ingredients of the bone tissues. Accordingly, it is expected that mimicking the chemical and physical structure of bone tissues could be valuable in their medical applications. Herein, a new porous biodegradable microcarriers (MCs) made of silk fibroin-oxidized alginate-bioactive glass was fabricated by electrospraying method. Response surface methodology (RSM) was used to study the... 

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... 

Despite extensive studies on the behavior of reinforced concrete slabs, especially those reinforced with steel rebars, no comprehensive studies have been conducted on the behavior of concrete slabs reinforced with FRP rebars. Therefore, there are some ambiguities regarding the tensile and compressive behavior of these rebars in the load-bearing capacity of reinforced concrete slabs (depending on their amount in the slab and their combination with steel rebars). Hence, in this study, in order to ensure the accuracy of numerical simulations, the numerical 3D simulation of a one-way concrete slab reinforced with tensile FRP rebars was performed using the finite element Abaqus software.... 

The rehabilitation of old structures holds a lot of importance, as many structures with a life span of over 30 years are prone to severe damage and even collapse. To overcome this problem, the use of FRP sheets to strengthen structures is suggested. RC-arches have been used in many structures such as bridges and require specific consideration in terms of strengthening. So far, the influence of the number of FRP layers and location, the height of arch and percentage of reinforcement on strengthened arch behavior have not been investigated. In this research, reinforced concrete arch members strengthened with GFRP and CFRP were investigated. A total of 28 Specimens, including four... 

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...