Sharif Digital Repository

Electroplating is an appropriate method for co-deposition of metallic, non-metallic and polymeric fine particles onto a metal matrix for production of functional coatings. In this study, chromium and Cr–Al2O3 composite coatings are electrodeposited from trivalent chromium bath by using DC and square pulse current. Dependence of the amount of Al2O3 nano-particles trapped into the coatings on the Al2O3 bath concentration, average current density, particle size, agitation rate and type of the current is investigated. These parameters are optimized for the highest co-deposition amount of the Al2O3 onto chromium layer. Optimum values are 20g/l Al2O3, 200 rpm stirring rate and 25A/dm2 current... 

In this research, aluminum composite foams reinforced with silicon carbides were manufactured using melt direct foaming with gas. The density of produced foams changed from 0.1 to 0.35 g cm-3. At first, simulation of bubble configuration was carried out in order to specify the effective parameters on foaming process. As the result, parameters such as ceramic particle volume percentage and gas type were selected. Results showed that, to process foam with acceptable stability, there was a critical minimum of ceramic particles concentration above which, stability of the foam was enhanced. Gas type was also showed to have a significant effect on foam stability. Argon, carbon dioxide and air were... 

NiTi intermetallic is well known for its unique physical and mechanical properties, such as superelasticity, shape memory effect, good tribological properties, excellent corrosion resistance and biocompatibility. It is widely used in several areas including aerospace and medical applications and surface engineering. Several approaches, such as casting, powder metallurgy, self-propagating high-temperature synthesis, mechanical alloying and explosive shock-wave compression have been used to produce NiTi alloys. However the formation of the undesirable phases such as NiTi2 and Ni3Ti still is the biggest concern. According to Ni-Ti phase diagram, stability region of NiTi compound is at... 

Semiconductor-based photo catalysts, titanium dioxide (TiO2) especially, have been extensively studied for the oxidative photo destruction of organic pollutants in wastewaters and hydrogen production as a green energy source. Much effort has been made to remove the restrictions on the use of TiO2 and challenges related to the recovery of powdery photocatalysts. In this study, copper oxide (CuO) and Zirconium oxide (ZrO2) were used to synthesize nanocomposites. Composition of TiO2/CuO and TiO2/ZrO2 with different weight percentages of second dioxide was synthesized by chemical methods and structural properties of samples were studied by X-ray diffraction and scanning electron microscopy.... 

The use of dental implants has grown considerably in recent years in Iran but this piece is the industrial imported parts that are not yet produced in Iran. So the main purpose of this research was to fabricate a dental implant from Ti-6Al-4V alloy by CNC machining techniques. On the other hand, the poor bonding strength of bioactive coatings and low cell growth on the surface of uncoated implants are the common problems in the use of dental implants. So another aim of this study was to investigate the effect of Nanoscale surface topography and nanostructured coatings on the surface modification of titanium implant in order to improve Osseointegration and the bonding strength of bioactive... 

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,... 

The main purpose of this research is design and manufacture of nanostructured hydroxyapatite-coated foamy core@compact shell Ti-6Al-4V bone-like composites for utilization as substitutive implant for cortical bone having porous core. The production procedure consist of two steps; (a) fabrication of foamy core@compact shell Ti-6Al-4V alloy using powder metallurgy-space holder technique, (b) precipitation of hydroxyapatite on the Ti-6Al-4V alloy specimens via pulse electrodeposition process. The bone-like structures were designed to reduce the stress shielding which ensures long-term stabilization of implants. It is while that, the hydroxyapatite coating improve the biological response of... 

In recent decades, due to the significant growth of implants’ application and considering the infection of the implants as the most momentous factor in implantation failure, study on the controlled drug release and other biologically active agents in modern drug delivery systems has attracted many kinds of research throughout the world and efforts are being made to use regulated drug delivery systems for implantation which is also the purpose of this current scientific work.To achieve this, the anodizing process was used to fabricate titanium oxide nanotubes (TNTs) to increase the absorption capacity of the drug in the implants and these TNTs were formed regularly and uniformly in an organic... 

NiTi Memory alloys have a great range of applications. Porous metallic biomaterials (e.g., stainless steel, chromium- cobalt, titanium and nickel–titanium (NiTi)) represent superior alternatives to traditional non-porous metallic implants for two main reasons. First, open porosity can enhance bone ingrowth and thus improve fixation at the interface between bone and implant. Second, porosity decreases the mismatch in stiffness between bone and implant, thus reducing stress-shielding effects which shorten the lifetime of the implant through bone resorption and loosening. NiTi foams may thus find multi-functional applications such as bone implants, impedance-matching connectors between... 

Nickel oxide is used in the manufacture of ceramic, magnetic materials, battery cathodes, electrochromic films, heterogeneous catalytic materials and gas sensors. NiO nano-powder can be produced with many different methods. The synthesis of NiO nanopowder has been carried out via solochemical processing from an aqueous solution of a Ni containing complex in this research. Another name for this method is two-stage solochemical (TSSC) method. This is the newest economic method for synthesis of NiO nanopowder. NiCl2 anhydrous and NH3-H2O used as the raw materials and H2O used as solvent. The results obtained from XRD and TEM show that the nanoparticles have cubic crystal structure and the mean... 

Based on the new standards, less than 10 ppm sulfur is allowed for the automotive fuels. This has led researchers to try improving the present conventional methods as well as seeking alternative routes for refinement of the petroleum products so much to comply with the requirements. Since thiophenic fragments such as dibenzothiophene (DBT) are the most durable sulfur compounds in the current hydrodisulfurization method, many studies have been conducted over recent years on how to remove these compounds. In this thesis, the desulfurization of dibenzothiophene from gasoline via adsorption method was studied. In order to carry out the adsorption process, a nanocomposite of graphitic-carbon... 

For measuring damping capacity of shape memory alloy, samples containing Fe- 27Mn-6Si-4Cr-4Ni were prepared. In order to produce the alloy 99% pure elemental powders were mixed and pressed in a matrix rod. The packed powders put in 15cc alumina crucibles were held in a 200 °C oven for 10 hours before they were melted inside two–layered alumina and graphite grucible an induction furnace. Resulting samples went under hot and cold rolling, thermomechanical treatment and were shaped into strips by wirecut. Chemical composition ascertainment, Tensile, bending, differential scanning calorimetry (DSC), micro hardness and modal tests were operated. Microstructural investigation was done using... 

Nowadays, because of drastically decrease of copper sulfide ore’s grade, and difficulties in leaching of them, new processes of copper production like bioleaching technique become significant. Finding the optimal conditions for bioleaching, require investing a lot of time and cost. Computer simulation is useful in this case. Temperature, affects the kinetics of dissolution reactions, type and growth rate of bacteria, and finally, rate and amount of recovery of valuable copper metal from ores, so determination of temperature within the bioheap is very important. Thermophiles are better than mesophiles in chalcopyrite bioleaching and in the range of 55 to 65 degree centigrade, thermophiles... 

Sodium-ion batteries are cost-effective rechargeable batteries which have attracted considerable interest in recent years due to the low cost and abundance of sodium resources on the earth. Na3MnCO3PO4 (NMCP) has been identified as a potential cathode material with a high theoretical capacity of 191 mAh g-1. In order to improve the conductivity and electrochemical properties of NMCP, fabrication of NMCP/reduced graphene oxide (rGO) composite is a novel and interesting research goal. Therefore, in the current study, rGO was produced by using modified Hummers method. Then, the kinetics of NMCP formation through hydrothermal process was investigated. Results indicate that the optimum... 

NiTi is known as a most important material for manufacturing implants and other medical devises duo to its shape memory and super elasticity properties, high energy damping and high corrosion resistance.In this project the possibility of producing nano structured NiTi implant with high porosity was investigated. For reaching to nano scale mechanical alloying process was done on Ti and Ni powder as row materials. Mechanical alloying process and the possibility of reaching nano structure or amorphous phase was investigated. Space holder technic was used for reaching a porous structure. Sintering process was planned in a way to inhibit grain growth as much as possible. The samples sintered in... 

Transparent conductive electrode (TCE) is one of the indispensable constituent of optoelectronic devices, which heretofore various materials such as ITO, graphene, CNT, metal nanowire and nanofiber network have been used to produce them. It should also be assumed that the use of low-cost materials, which has cost-effective production method, is essential for the construction of transparent electrodes. Copper nanofiber network film which is obtained from electrospinning process is a promising candidate among these materials because it has superiorities, such as low sheet resistance, proper flexibility and abundance in ground resources, scalable and cost-effective fabrication method. There are... 

Influence of attachment of Multi Walled Carbon Nanotubes (MWCNT) on various nickel nanocatalysts produced by the electroless plating method was investigated via Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), Atomic Absorption Spectroscopy (AAS), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) measurements, Temperature Programmed Reduction (TPR) and Temperature Programmed Oxidation (TPO) tests. Application of TPR/TPO data to Kissinger (Redhead) Equation yielded the activation energies of both nickel reduction and nickel oxidation reactions. Addition of MWCNT improved the catalytic effects by easing of... 

In the last decade, a great deal of attention has been paid to the study of synthesis of Nanoparticles, because of the widespread use of this material in applications involving Fuel cells and magnetic devices. In this thesis, we report some interesting features in the electrodeposition of metallic nanoparticles. The electrochemical phase formation of rhenium and nickel on the surface of P-Si (100) substrate plus morphological, topographical and fractal aspects of the accumulated surface were investigated in this research by means of chronoamperometry method and by utilization of AFM and SEM. The nucleation and growth mechanisms on silicon electrode are characterized using cyclic voltammetry... 

This work examines the dissolution kinetics of Sodium meta vanadate in water medium. The effects of temperature, solid/liquid ratio, agitation speed on the leaching kinetics were investigated. the dissolution kinetics was controlled by the internal diffusion at the surface of the Sodium metavanadate particles. The activation energy for the leaching was2/13 kJ/mol. In the current project, we report the preparation of VO_2 nanorods crystals using a ethylenediaminetetracetic acid assisted and Cetyl Trimethyl Ammonium Bromide hydrothermal synthesis route. NH_4 Cl and NaVO_3 solution were used as the starting materials and vanadiumoxide crystals were obtained following growth at 180 °C for 24... 

The aim of this project is the synthesis and study of the photocatalytic activity of biphasic titanium dioxide loaded with Au@Ag@Au core double shell bimetallic nanoparticles. The creation of nanostructure, utilization of hierarchical biphasic morphology, loading of light-sensitive particles, and stabilization of photocatalytic particles have enhanced the titanium dioxide photocatalytic activity via approaches of (1) sensitization to visible light, (2) separation of charge carriers produced by light irradiation and minimization of their recombination, and (3) advancing reaction and absorption of reactants by increasing quantity and quality of surface active sites. Hierarchical TiO2...