Sharif Digital Repository

In this research,Graphene Oxide nanoplatelets (GO) were synthesized by chemically modified Hummer's method.After the GO nanosheets electrochemically reduced to graphene, nanoparticles imposed to this thin film.This optimized nanostructure coating was utilized for investigating the Hydrogen Evolution Reaction (HER) over the copper substrate. In order to optimize the kinetic of electrodeposition and reduction, diverse electrochemical approaches such as cyclic voltammetry, chronoamperometic and potentiometric as well as pulse electrodeposition methods were employed. Electrochemical procedures were aligned by Design of Experiment (DOE) ... 

Silver is a resistant metal against the oxidation under normal atmospheric conditions, but it reacts readily with sulfur bearing species in the environment and corrodes. Alloying silver with more noble elements, such as Palladium, is a promising approach for increasing corrosion resistance against the sulfur pollutants. The purpose of this research is to develop a plating bath for deposition of Silver-Palladium alloy with acceptable appearance and higher corrosion resistance than pure silver. For this purpose, a bath based on thiosulfate complexing agent was investigated. In this solution, with a bath containing 10 mM of each cation, deposits with palladium content of 6, 11 and 14 % were... 

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... 

TLP diffusion bonding method refers to a method in which two metal pieces can be bonded by putting an interlayer between two pieces and heating to a temperature lower than base metal melting point. Theoretically, this process shows that the bonding line disappears completely at the end of the process and it is not possible to recognize it. However, these assumptions were not accomplished in practice. Therefore, various parameters such as material of interlayer, thickness of interlayer, temperature and time of bonding, temperature and time of homogenizing and applied pressure on metal pieces should be controlled to achieve the best shearing strength results. Aluminum based composites have... 

Biodegradable implants are new generation of implants that require no secondary surgery for their removal. Mg exhibits a great potential to be used as the biodegradable implant. However, mechanical properties and biocorrosion behavior of Mg are not suitable for being used as biodegradable implants. In this study, effects of Sr additions, heat treatments (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biocorrosion behavior of Mg-4Zn-xSr alloys, and also the effect of hydrothermal coating on the biocorrosion behavior of Mg-4Zn-0.3Sr alloy were investigated. Potentiodynamic polarization and hydrogen evolution methods were used to... 

Considering the importance of biocompatibility of implantable prothesis’, metallic alloys have weaker corrosion resistance than ceramics. In order to extend usage of nanomaterials to improve the bio-properties of materials, Nano-structured ceramic coatings are being suggested to improve corrosion resistance and biocompatibility of prosthesis. Meanwhile, very good properties of TiN, such as corrosion resistance and mechanical properties as a thin film coating are undeniable. In this study, TiN and Ti2N thin film were deposited on Ti-based substrate, using PVD and Magnetron sputtering at different argon to nitrogen ratio. The crystal structure of the films was examined using Grazing XRD... 

In several electro-optic and optoelectronic devices, we require the structures with simultaneous high electrical conductivity and optical transparency so as to transmit the incident light. Transparent Conductive Electrodes (TCEs) that are both highly conductive and transparent were introduced to be an answer to the mentioned challenge. Periodic arrays of metallic holes are amongst the most important structures that are used as transparent electrodes. Using the metals with low electrical resistivity, such as Au and Ag, provides these structures with high electrical conductance. On the other hand, since these micro/nano structures support the propagation of guided electromagnetic waves, light... 

An optimization condition for obtaining Ni-Zn-P electroless alloy coating has been developed. The sulphate bath with sodium hypophosphate as a reducer and sodium citrate and ammonium chloride as complexing agents were used. The effect of variation in the pH level , temperature , time of deposition and reactants concentration on stability of bath, coating composition, microstructure, microhardness and corrosion resistance of coatings was investigated. The composition of coatings was obtained by using the EDAX analysis. To investigate coating morphology, SEM images were taken and to study the corrosion behavior of coatings potentidynamic polarization, Electrochemical Impedance Spectroscopy... 

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... 

Nowadays, the development of different polymer blend nanocomposites is of great importance for achieving electrical and antistatic properties for various applications such as auto parts and the packaging industry. Immiscible polymer blends with conductive nanoparticles such as carbon nanotube, graphene, etc. can reach the conductivity threshold with low amounts of nanoparticles and produce desired electrical properties. In the present study, we have attempted to develop a polystyrene(PS)/ethylene-octene copolymer(EOC)/carbon nanotube(CNT) blend nanocomposite with suitable electrical conductivity. The compounding was performed by melt mixing at two weight percent of 80/20 and 50/50 (PS/EOC)... 

The purpose of this study is to study heterogeneous nanocatalysts for the production of biofuels by the method of exchange of styrene using oil and methanol as a fossil fuel alternative. Preparation of nanocatalysts, performing characteristic tests and investigating the reaction in different operating conditions in the batch reactor has already been studied. Therefore, in this study, the production of biodiesel fuel using the trans-esterification of canola oil with nanocatalysts in the micro-reactor reactor will be discussed. Previously, a heterogeneous catalyst (lithium based on calcium-lanthanum) was constructed using a co-incineration method and a wet inoculum, and as active and stable... 

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... 

This study investigated the effect of oxidized molybdenum disulfide (MoS2) nanosheets on the anti-corrosion and rheological properties of epoxy resin. Raw MoS2 sheets were obtained as layered nanosheets with a thickness of 50 to 100 nm using acid washing, oxidation, and heat shock methods. The use of nanoparticle characterization tests such as XRD, FT-IR, FE-SEM, EDS, and TGA supports this claim. Then, in the next step, epoxy coatings containing different percentages (0, 0.3, 0.5, 0.8, and 1.5 wt%) of MoS2 nanosheets were prepared with polyamide hardener to investigate the effect of adding nanosheets and the optimal percentage. The best effect on the corrosion properties of the coating in a... 

Iron oxide nanoparticles were synthesized using microemulsion technique as MRI contrast agents. Utilization of nanoparticles for biological applications and in this case as MRI contrast agents needs particles to be of small size and also narrow size distribution. For this aim, the effect of several parameters on size and size distribution has been studied. These parameters include water/surfactant ratio, precursor’s concentration and amount of polymer employed to improve nanoparticles colloidal stability. XRD, FE-SEM and TEM results reveal that the synthesized nanoparticles had small size (about 10 nm iron oxide core and 20 nm overall diameter) and possessed narrow size distribution (15-21... 

Nowadays, proper design and retrofitting of structures against natural and manmade disasters, is among the main concerns of researchers and designers in order to reduce financial and human costs. Extensive research has been carried out on the structures resistance against earthquake up to now. Although, the vast amount of research has resulted various regulations and guidelines, there is still a long way ahead to achieve the desirable results. Due to high sensitivity of the steel to temperature variations, fire exposure is more destructive for steel structures compared with the concrete ones. The performance of an intermediate three-storey steel moment frame with 4 spans was studied in this... 

The aim of this thesis was creating Titania/RGO coating with electrophoretic method to evaluate the corrosion resistance of stainless steel 316. At first Graphene Oxide were synthesized with modified Hammers method and their physical, chemical and morphological properties have been investigated using XRD, FTIR, EDX, TGA, UV-Vis and Raman analysis. then Graphene Oxide was added to the bath of titanium and was deposited on 316 stainless steel substrates. Moreover, corrosion protection of coating has been examined using Poarization test and Electrochemical Impedance Spectrometry. The effect of deposition parameters on corrosion properties of composite coatings were examined. The key variables... 

The present study's main aim is to investigate the drag-reduction ability of liquid-infused surfaces inspired by the pitcher plant. The present study can be divided into experimental and numerical sections. In the numerical section, the drag reduction ability of these surfaces was investigated in the internal flows. For this purpose, the effect of different parameters, such as Reynolds number, viscosity and density ratio of working fluid and lubricant, overlayer film thickness, and Ohnesorge number representing the interfacial tension, on the drag reduction was investigated. The results revealed that the variation in density ratio and Ohnesorge number had insignificant impact on drag... 

This research is divided in three parts. In the first part of this research, we report the one-pot synthesis of carbonate-coated nanostructured LLO (Li2CO3@LLO) through a polyol-assisted method as a Li-ion battery cathode. Carbonate protects the cathode from adverse reactions with the electrolyte, also reduces the layered-to-spinel phase transition, thereby stabilizing the cathode structure. LLO nanostructure provides a fast Li+ diffusion. The target material exhibits excellent long-term stability with 77% capacity retention after 1000 cycles at 0.2C-rate. In the second part of research, Li(Na-doped)-Mn-Ni-O oxides were synthesized by different LiOH.H2O amount, type and amount of reducing... 

It is well-known that classical continuum theory has certain deficiencies in capturing the size effects and predicting the nanoscopic behavior of materials in the vicinity of nano-inhomogeneities and nano-defects with reasonable accuracy. Couple stress theory which is associated with an internal length scale for the medium is one of the higher order continuum theories capable of overcoming such difficulties. Since most reinforcements may not be perfectly bonded to their surrounding matrix, the perfect bonding condition is often inadequate in describing the physical and mechanical behavior of real composite materials. In this work, the problem of a nano-size fiber embedded in an unbounded... 

It has always been a challenge to make self-cleaning coatings based on super-hydrophobic properties that can provide the necessary features to be operational in the industry. One of these necessary features is the ability to easily apply the coating on the substrate and reduce the cost by finding the optimal amount of consumables. Therefore, in this research, at first, it was tried to produce silica nanoparticles with a particle size of less than 011 nm using the Stober method, and then the surface of the synthesized nanoparticles was coated with HDTMS (Hexadecyltrimethoxysilane) to make the silica particles, which are hydrophilic in nature, hydrophobic. According to the conducted studies,...