Sharif Digital Repository

Joining of yttria-stabilized zirconia (YSZ) to stainless steel (SS) is considered for various applications such as solid oxide fuel cells, thermal barrier coatings, and medical implants. In the present work, a series of brazing pastes utilizing silver and nickel nanoparticles (~80 nm) mixed with carboxymethyl cellulose as the organic phase were developed to join 5YSZ to 420 SS. The effects of processing parameters such as time and temperature of brazing and the composition of the paste on the microstructure of the joint and its mechanical strength were studied. The mechanism of interface formation was elaborated by scanning electron microscopy (SEM) and electron probe micro analyzer (EPMA).... 

The commercial breakthrough of micro-tubular solid oxide fuel cells (MT-SOFCs) is still facing so many challenges because of the complexity of their manufacturing process and the high cost associated with them. By deploying electrophoretic deposition as a simple and cost-effective method, the different components of the fuel cells (the anode, electrolyte, and cathode) can deposit on the graphite rod as a sacrificial substrate. The next step is eliminating the sacrificial substrate which will make hollow rods of cell components. The results of this study show that the use of a particular type of pencil lead will have a minimal negative impact on the overall fuel cell performance, leading to a... 

In this research, aluminum matrix composites (AMCs) reinforced by different contents of zirconium dioxide nanoparticles, graphite microparticles, and a mixture of both with various hybrid ratios, into a cold-rolled Aluminum1050 as base metal, fabricated by 4-passes friction stir processing. Observations show that the processing of composites reinforced by Gr particles is significantly hard due to the low friction coefficient of graphite resulting in the decline in the maximum temperature during the process and the type of base metal. The mixtures of graphite and zirconia resulted in more homogenous dispersion of particles in the matrix due to deterring a drastic drop in friction coefficient... 

In this investigation, nanostructure Fe3Al was produced by mechanical milling initially. Pure iron and aluminum powders were milled with suitable ratio 86Fe-14Al by weight. Milling was done up to 120 h times and with BPR 10 and BPR 20. Morphological changes, powder density and size, phase and structural changes, grain size and lattice strain were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and laser particle size analyzer (LPSA). 40 h mechanical alloying with BPR 20 led to the corresponding intermetallic compound, Fe3Al with a nanocrystalline structure. Therefore Fe3Al/ZrO2 micro and nanocomposite powders were synthesized with manufactured by milling of... 

Metallic implants are useful in dental and orthopedic applications. Bio coating is necessary to improve bio-compatibility and bio-activation of metallic implants. For this goal, HA is the most important material. In this research, the goal is to improve bio-compatibility of St. St 316 by coating HA, HA-ZrO2, HA-TiO2, HA-ZrO2-TiO2 using combination of electrodeposition and electrophoretic methods. To form HA, calcium and phosphor salt solution was used then ZrO2- TiO2 nanoparticles was added to solution. In order to analyst the coatings different tests were done. Thickness analysis, XRD, FT-IR, FE-SEM and EDS, bonding Strength, Polarization test, bio-compatibility and surface roughness... 

In this study, antistatic waterborne polyurethane coating containing zirconia nanoparticles is made and applied on 304 stainless steel substrates at weight percentage of 0.66, 1.3, 3, 4.5 and 6% zirconia nanoparticles. For synthesis of hydrophilic isocyanate prepolymer, isocyanate prepolymer is modified by hydrophilic polyethylene glycol with molecular weight 600, 1000 and 4000. For ensuring of modification condition and stability of hydrophilic isocyanate prepolymer in aqua solution, FTIR and stability tests are employed, respectively. In order to create antistatic properties of these coatings, semi - conductive zirconia nanoparticles are used. To improve the distribution of zirconia... 

In this study, the ultrafine-nanometric yttria stabilized zirconia (YSZ) particles were used for reinforcing of copper metal powder. To producing of bulk nanocomposite specimens, the copper powder and the proper volume percent of reinforcement powders (i.e. 2, 3 and 5) were mixed using Turbula mixer for one hour. Before the mixing of two metallic powders and ceramic nanoparticles, for separation of agglomerated zirconium oxide nanoparticles that witch leads to producing of nanocomposite specimens with satisfactorily distributed secondary phase, the ultrasonic devise with enough quantity of ethanol as neutral liquid have been used for 15 minutes. The powders mixture have been placed under... 

Medical engineering advances in total joint replacements and society’s rising demand for long lasting materials, have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological and biological properties. Ultra High Molecular Weight Polyethylene(UHMWPE), is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability and proper mechanical properties. In this study, UHMWPE-HAp nanocomposites reinforced with Zirconia and Graphene were manufactured aiming to reach a structure that is more compatible with bone tissue and also to improve overall properties. First, using ultrasonication... 

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... 

The purpose of this thesis is the construction of hard and tough Zirconia bodies from economical raw materials using minimum sintering time and temperature.
Stabilizers cause tetragonal particles to be remained in cubic phase. Most additives are Ca, Ce, Mg and Y ions the whole of which are rare earth elements and make solid solutions with Zirconia.
In this project different percents of CaO, MgO, CeO2, and Y2O3 were mixed with ZrO2 and they were sintered after granulation, cold pressing and Cold Isostatic Pressing. Using jar milling and fast milling, the particle size of purchased ZrO2 was reduced to 0.7 um. The whole needed additives were purchased with particle size below 300 nm.... 

Magnesium alloys are used in various industries, due to their excellent combination of low density, high strength to weight ratio and biocompatibility. However, a main drawback of Mg alloys is their poor corrosion and tribological behavior which could be improved by different surface treatments such as plasma electrolytic oxidation (PEO). Recently, PEO method as a simple and economic process is used to provide thick ceramic coating on Mg alloys. Based on some problems in zirconia coating on Mg substrates, two step PEO coating was introduced. The aim of the present study is to prepare and investigate the properties of zirconia-containing coating by two-step PEO process on the AZ31 Mg alloy... 

To study the kinetics of the yttria-stabilized zirconia produced by co-precipitation method from the chemical engineering point of view, this process was studied in two parts of hydrolysis and precipitation. the hydrolysis reaction was studied by titration method, and the rate constant and fraction of formation of hydrous zirconia was determined by applying Avrami equation. The results showed that the percentage of zirconia formation until the boiling time of 12 hours was zero and after 48 hours boiling was 2.81%. moment definitions were used In order to study the kinetics of precipitation. changes in precipitated powder concentration with pH of the solution was obtained based on the... 

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... 

In this research, role of zirconia nanoparticles as a biocompatible material which has great mechanical properties, was investigated on corrosion behavior and bonding strength of HA coating. HA- ZrO2 composite prepared by a 2-step pulse electrodeposition method. Effect of pH (3.5, 4.5), bath temperature (60, 80 ͦC), current density (0.5, 1, 2 mA/cm2) and zirconia concentration (5, 10, 15 g/L) on coating characteristics were studied. X-ray diffraction was employed for phase analysis. Morphology and microstructure of samples observed utilizing scanning electron microscope (SEM) and elemental analysis was done by EDS. In order to corrosion studies electrochemical impedance spectroscopy (EIS)... 

Alumina as an engineering ceramic has special characteristics such as hardness, high abrasive, fatigue and corrosion resistance but suffers from low toughness. One effective method in improving toughness is adding second phases such as tetragonal zirconia and carbon nanotubes.
In this research, alumina- zirconia nanopowders has been prepared by solution combustion method and carbon nanotubes was added to it by two different ways: 1) in situ synthesis of CNTs by CVD 2) dispersion of CNTs by heterocoagulation method. In the case of in situ synthesis of CNTs in AZ matrix, the synthesis temperature and flow ratio of N2/C2H2 gases was investigated and optimum conditions were 800̊C and 300/30,... 

Zirconium is one of the most applicable metals in the production of chemical materials’ industry due to its great corrosion resistance. Coating method of microarc oxidation is a novel method to manufacture oxide coatings on metal substrates. Lots of studies have been done on the creation of these coatings on light metals such as Aluminum, Magnesium and Titanium hitherto; however, there is a scarcity regarding manufacture of zirconium oxide on zirconium metal via MAO method. In the current study, aiming to create proper zirconia coatings on zirconium substrate, firstly, by the change of process parameters like current waveform, electrolyte concentration, current density, time and frequency,... 

In this study solid lubricants MoS2 nanoparticles with average size 50 nm and hard ZrO2 nanoparticles with average size 51 nm were used in watts bath and Ni/ZrO2-MoS2 composite coatings were prepared by pulse plating technique. Effect of current density, frequency, duty cycle, surfactant type and concentration of particles in the electrolyte on the amount of particles in the coatings were investigated and optimum conditions were determined to create composite coatings. Scanning Electron Microscopy (SEM) and x-ray diffraction (XRD) analysis were performed to study the morphology, structure, chemical composition of coatings. Corrosion testing of coatings by potentiodynamic polarization in... 

In this study, the joint of co-sintered zirconia/stainless steel is investigated. To this end ZrO2-3mol%Y2O3 (TZP) and 430L stainless steel powders were utilized. The joining parameters of co-sintering in zirconia/metal were studied. In order to study the microstructure, diffusion and probable reactions at the joint boundary, HRSEM, HRTEM, EPMA and micro-focused XRD methods were employed. Shear strength of the joint was also measured. Finite element simulation of residual stresses and thermodynamic studies are utilized in the next step to analyze the experimental results. It is found that the direct joining of zirconia to 430L stainless steel is feasible by co-sintering at 1350 °C under low... 

Zirconia Toughened Alumina (ZTA) is a well-known ceramic matrix composite due to its high fracture toughness and good mechanical properties. Addition of spinel (MgAl2O4) to ZTA inhibits alumina grain growth and produces phase boundaries with low strength. This phenomenon leads to formation of a ceramic matrix composite with special mechanical properties such as high temperature super plastic deformation. However, the room temperature mechanical properties of alumina-spinel-zirconia (AMZ) composite such as fracture toughness were rarely investigated by researchers. In this research the AMZ nanocomposite powders were synthesized via solution combustion method. The dense AMZ composite samples... 

Interest in lithium sources has been increasing because of wide applications of the metal in high-energystorage lithium batteries and its compounds in otherfields.Lithium appears in lake, brines and several minerals such as spodumene, petallite, and lepidolite. Several methods such as ion exchange (adsorption), solvent extraction, and coprecipitation have been investigated for the extraction of lithium from seawater, brine, and geothermal water. The adsorption method is suitable for recovery of lithium from seawater because certain inorganicion-exchange materials show extremely high selectivity for lithium ions only.The objective of this study is to evaluate the applicability of nano...