Sharif Digital Repository

The need for better characterization systems (electron microscopes) and high resolution lithography systems, have made electron beams systems an interesting choice for research and development. In fact, all of the above applications require ideal electron beams (beams with minimum energy spread, maximum current density, and minimum spotsize), and electron-optic lenses (simple lenses with minimum aberration). In this research, theoretical aspects of electron emission and lens systems are reviewed. Field emission array (FEA) electron guns are introduced as electron sources with minimum energy spread, and a new simulation method is presented in order to minimize the complexity, and reduce the... 

There are many techniques that have been used to create hydroxyapatite nanoparticles coating on nanotubes. Electrophoretic deposition (EPD) is one of the methods that has advantages of short formation time, needs simple apparatus, little restriction of the shape of substrate, no requirement for binder burnout as the green coating contains few or no organics. In the research, first, titanium dioxide nanotubes were fabricated by anodic oxidation. Anodizing voltage effect on the morphology of nanotubes was evaluated. SEM images was shown that in the anodizing voltage 20V, nanotubes were the most regular. Then, Hydroxyapatite nanoparticles has been deposited onto nanotublar TiO2 by... 

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... 

In this study, biocompatible ceramic coating, containing hydroxyapatite particles (HA), was successfully created by AC anodizing, on the surface of commercially pure titanium grades 2. Coating process basically consisted of three methods. In Method 1, samples were anodized in a salty electrolyte containing calcium – phosphate base and in method 2 samples were anodized as initial process, following cathodic polarisation deposition of HA particles. Finally in method 3, samples were anodized in an electrolyte containing of HA particles suspension.Parameters such as current density and time of anodizing process, in first procedure, and time of cathodic deposition process in second procedure, and... 

Many of the major structure over coastal waters in the Kish Island due to the aggressive condition are showing signs of reinforcement corrosion. Recent advances in the development of anodes make it practical to use zinc galvanic cathodic protection to protect this structure in this area. Five anode systems were tested on several samples as, (1) zinc metal spray applied by arc-spraying on the concrete, (2) a zinc foil with conductive adhesive backing, (3) a system of zinc mesh and grout jacket, (4) a system of zinc mesh and compression panels, and (5) a bulk zinc. These anodes are set up to comparison the effects of potential and current over the zinc galvanic cathodic protection during 4... 

Titanium anodes activated by noble metal oxides under the trade name of dimensionally stable anodes (DSAs) are widely used in the electrolytic industry, particularly in chlor – alkali electrolysis. Over 20 years of use, the fundamental aspects of their long – lasting performance are not fully understand and the corrosion mechanisms are still the subject of many investigations. RuO2 – TiO2 coatings on titanium substrate, due to proper electrochemical characteristics and good corrosion resistance, is most applicable as an anode in chlor – alkali systems. In the present investigation, the first layer of Pt – Ir coating is applied via electrodeposition method on the pretreated titanium substrate... 

In this study, the performance of Inconel 617 anode as an inert anode in aluminum electrolysis process was studied. To carry out the research, first, an electrolyte was produced using NaF, KF, AlF3 and Al2O3 with a molar ratio of sodium and potassium fluoride to aluminum fluoride of 1.33. Next, aluminum electrolysis cell was made using Inconel 617 anode and cathode and the aforementioned electrolyte. To evaluate the Inconel 617 anode, the performance of the electrolysis cell in different conditions of temperature, anode-cathode distance, and excess potential was investigated in a period of one hour. Using anode mass measurements, cell potential and current density and scanning electron... 

Among the various materials, silicon anodes have the highest lithium absorption in lithium-ion batteries. But this high lithium absorption capacity can cause 300 percent volume expansion and large stresses. Experimental observations show that charge and discharge cycles may cause plastic deformation in some parts of the electrode particle. On the other hand, there is a possibility of a ratcheting phenomenon due to changing in elastic properties of the electrode material during the charging and discharging processes. However, this phenomenon has not been reported for silicon spherical electrode particles yet.This study aims to model the elastic-plastic behavior of silicon spherical electrode... 

This dissertation argues that bi-conductive textured surfaces increase both Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) simultaneously. Surface modification is applied to stainless steel specimens by the anodizing method in an electrolyte containing Ammonium Fluoride and DI-Water and Ethylene Glycol as the based solvent. The process of oxidation was under constant DC voltage and constant temperature. The contact angle on self-aligned Nano-porous oxide layer fabricated on the substrate substantially decreases to about 5.7 degree which has a dramatic effect on CHF. Furthermore, the oxide layer augments the boiling efficiency by increasing the number of active sites and... 

The present work describes sensing application of modified TiO2 nanotubes towards detection of dopamine. The TiO2 nanotubes electrode was prepared using anodizing method at different conditions, among which NaF/ NaHSO4 solution and voltage of 15 V was chosen as the optimum condition. In order to improve the performance, surface modification with metal nanoparticles (Pd, Pt and Au) and carbon is required using “pulse electrodeposition” and “decomposition of polyethylene glycol at 600 °C” respectively. Carbon was deposited by decomposition of polyethylene glycol in a tube furnace to improve the conductivity. In this regard two type of electrodes were proposed: Pd-Pt-Au-TiO2 and C-Ni(Pt)-TiO2.... 

In recent decade, photocatalystic properties of titania nanotube and its mechanisms has been considered greatly in many researches. One of the major ways to increase photocatalystic properties and extending the usage of TNTs is doping them with various elements and modifying their band structure. In present research doped TNTs were prepared by doping of Molybdenum, Nitrogen, and Carbon elements by anodizing method in about of 35 degrees of centigrade and constant voltage of 20V on the surface of titanium sheet. Structural and photocatalystic properties of as-prepared TNTs were studied using field emission scanning electron microscope (FESEM), x-ray diffraction (XRD), energy dispersive... 

In the present study, it has been tried out to increase the hardness and wear resistance of anodized aluminum coating byadding Si3N4 nanoparticles to the anodizing bath and making a composite coating. In order to investigate the influence of other effective parameters on the properties of anodized coating before the compositing process, hardness and thickness were optimized in the Sulphoric/oxalic bath using design of experimental method (central composite design). The properties of these coatings are dependent on various parameters among which time, temperature and pulse current parameters (current density limit, frequency and duty cycle) were considered in the present study. Analysis of... 

In this research we focus on study and fabrication of ordered nanotube arrays of titanium oxide and their applications in photoelectrochemical cell. Nanotubular films of titanium oxide have been fabricated using anodization method. Short-length nanotubes, less than one micrometer, have been synthesized in aqueous electrolyte containing deionized water, hydrofluoric acid and phosphoric acid. To get Micron-length nanotubes, we have employed organic electrolyte containing ethylene glycol, deionized water and fluoride ammonium. After fabrication, the photo-catalytic activity of nanotubular structures was evaluated by measuring the rate of degradation of in methylene blue aqueous solution. The... 

In this study anodized none composite and composite film containing ZrO2 nanoparticles were prepared on 1050 Al Alloy using hard anodizing method in sulfuric and oxalic acid mixed solution by pulse Currents. The microstructure and properties of the film were studied by field emission scanning electron microscopy with EDS analyzer and XRD diffraction and friction wear test were performed to evaluate the mechanical properties of coating . Results indicate that the composite film with ZrO2 nanoparticles have reduced friction coefficient with high micro hardness friction coefficient of composite film can be small as 0.16 which is much smaller than that 0.39 of none composite film. Micro hardness... 

In this research, first thin films with nanostructures of titanium nanotube arrays (TNAs) synthesized by anodization under different applied voltage (20- 60 V) and different reaction times (120 and 200 min). The electrolyte solution for synthesizing the samples contained 90% ethylene glycol (EG), 10% DI water, 0.1 M NHR4RF and a little HR3RPOR4R to reach the pH to 5.6. The synthesized samples crystallized under annealing treatment at 500 °C (with heating rate of 9.5 °CminP -1 P). The scanning electron microscopy (SEM) analysis was indicate that the length and the inner diameter of the nanotubes have increased from 1.6 μm and 67 nm (for 30 V anodization and for 2h) to 4.2 μm and 125 nm (for... 

Ruthenium based-oxide coatings on Titanium anodes are widely used as DSA (Dimensionally Stable Anode) for chlorine and chlorate production. Coatings consisting of composition of highly conductive oxide of noble metals (Ru, Ir and Pt) make them as long lasting anodes in chlor-alkali technology.In this work, a newly anode by a ternary coating of IrO2, RuO2, and TiO2 on the Pt-coated Ti was developed through thermal decomposition of iridium and titanium and ruthenium inorganic salts dissolved in n-pentane. The effect of deposition parameters such as current density, time, different condition of baking, heating, mole ratio and pulling up the samples was investigated to find out reasonable... 

In this study, desulfurization of petroleum coke has been investigated for use in aluminum industry. To reduce sulfur content in petroleum coke, desulfurization has been investigated by two methods of solvent extraction and molten caustic leaching. The method of molten caustic leaching at temperatures of 400-600 °C has been investigated. Other effective parameters on the desulfurization of petroleum coke are the mass ratio of alkali to feed (petroleum coke) in the range of 0.5-1.5 and the time of 1-3 hour and the mesh size of 200-600 micron. In this study, the conditions of desulfurization of petroleum coke using potassium hydroxide have been investigated. Results show that by using the... 

Ice formation upon various surfaces could lead to many industry problems and result in unpleasant accidents. For instance, the formation of ice on wind turbine blades or airplanes/helicopter wings could cause catastrophic disasters. The methods used to address this problem usually require exogenous energy consumption or anti-ice ingredients. The energy or anti-ice ingredients usage has adverse environmental effects and should be replaced with better approaches. One of these approaches is utilizing modified anti-ice surfaces. In this method, by modifying surface features, such as physical asperities and surface energy, the icing time of the surface could be prolonged. These surfaces are... 

The future crisis and environmental pollution led to increasing interest in alternative energy conversion systems such as solid oxide fuel cell (SOFC). One of the main obstacles in using SOFCs is their relatively high fabrication cost compared with their low amount of produced energy .Therefore, in the present study, fabrication of a more cost-efficient functionally graded NiO-YSZ composite for SOFC anode by electrophoretic deposition (EPD) method was investigated. In this research, the effect of different chemical parameters such as media, additives, particle size distribution and nano NiO addition were initially investigated on the stability of NiO-YSZ suspension by Zetasizer and turbidity... 

Today, recycling lithium as a valuable metal from brine plays an important role in various applications such as battery manufacturing, computers, aerospace and automobiles. Among the aqueous methods available for the extraction of the lithium element in brines, ion exchange by TiO2 nanosorbents is one of the most efficient methods. In this study, first the titanium dioxide nanotubes were well synthesized by anodizing method and the nanograss created after the anodizing process were completely eliminated. Then, the effect of three cathodes of aluminum, graphite and stainless steel in order to select the best cathode and achieve a regular morphology as well as their replacement with platinum...