Sharif Digital Repository

This present work is an introduction of a new electrochemical sensor toward the determination of biomolecule. A simple electrodeposition method was employed to construct a thin film modifier of palladium–gold nanoparticles (Pd–AuNPs) decorated multi-walled carbon nanotube (MWCNT) on the surface of glassy carbon electrode (GCE). Morphological characterization of the modified electrode was performed by the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and cyclic voltammetry (CV) techniques. This nanostructured film modified electrode effectively exhibited enhanced properties for the detection of ceftazidime (CFZ). The effects of various experimental variables such... 

In this study, transformation of austenite to ferrite under continuous cooling condition of a low carbon steel was investigated. In the first step, a heat transfer model was employedconsidering governing heat transfer boundary conditions and a microstructure model based on Cellular Automaton method was used simultaneouslyto predict austenite to ferrite transformation progress. The influence of pre-heating temperature and primary austenite grain size on the final ferrite grain size and distribution were perdected. To verify the simulation results, experimental processes were utilized. The microstructure distribution was determined by means of Clemex Pro software then, these results were... 

The present work is based on the, synthesis and investigation of photocatalytic activity of TiO2, TiO2/MWCNT, ZnO and ZnO/MWCNT nanostructures. The nanostructures were prepared using multi-walled carbonnanotubes (MWCNT) as templates.The SEM images of TiO2 and ZnO nanoparticles and TiO2/MWCNT andZnO/MWCNT showed that nanosize TiO2 and ZnO particles homogeneously and densely supported on the surfaces of multiwall carbon nanotubes the photocatalytic activity of the TiO2, TiO2 /MWCNT, ZnO and ZnO/MWCNT was examined by the degradation of Basic Blue 41(BB41) under UV and Vis lights. The optimum conditions for degradation of BB41 on TiO2 where found to be: calcination temperature (450 °C), dye... 

In this research, initially the Triethylene glycol and Diglycol amine liquid membrane which is supported by PVDF, was prepared in order to separate the Carbone dioxide from CO2-Air mixture. A polyvinylidene fluoride (PVDF) membrane was chosen to have chemical resistance to solution. The effect of Pressure, Concentration of TEG and DGA solution and the percentage of carbon dioxide in feed; in rate and permeability of CO2, N2 and O2 and also selectivity of CO2/ N2 , CO2/ O2 and N2/ O2 was investigated. Transport of CO2 was facilitated due to reversible chemical reaction between CO2 and amine solution. The experiments were done in 0.4, 0.6 and 0.8bar and different concentration of solution.... 

Polyvinylalcohol/MWCNT nanocomposite films were fabricated via solution casting method. Glycerol was added to the polymer matrix as plasticizer in order to improve the flexibility and toughness of resultant films. Surface modification of MWCNTs were carried out by subjecting to gamma irradiation of 60Co source to total doses of 50.0 and 75 kGy in pure ethanol and in a solution with equal volume fraction of water and ethanol. The produced nanocomposites in each case which contain different type of modified MWCNTs were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical and electrical measurements. The... 

An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition (CVD). By varying CVD parameters, aligned CNTs (A-MWCNTs) with diameter between 20-100 nm and length of some micrometers with bamboo-like shapes were produced. Free-standing MWCNTs arrays were functionalized and purified through electrochemical oxidation. Then in order to improve the performance, facile template-free electrochemical routes were developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, sheet and rod on A-CNTs at room temperature. The results showed that the... 

Molten carbonate fuel cell (MCFC) is a kind of high operating temperature fuel cells (600-800℃), tupically used for stationary power plant. These fuel cells have high efficiency (about 50%), but expensive to produce electricity. Hence, fuel cells are integrated into gas turbine cycle to decrease cost and increase efficiency of system. In this work, an integrated pressurized molten carbonate fuel cell is selected. Then, structure of selected process is changed and two new systems have proposed. Then, steady-state and dynamic behaviors of three systems were simulated separately, and their performances were compared. Efficiency increased about 5% in two new structures. Total power of system,... 

The use of carbon nanotubes in Nano-switches is the new technology employed in NEMS. Nano-switches can also perform as a micro-switch where nano-switches have longer life time, consume lower power and have smaller size with respect to micro-switches. As the dimensions get smaller, continuous models lose their accuracy and molecular methods should be utilized. Non local theory, is attempting to change the responses of continuum models assuaging them to the molecular results. In the current project, non local theory is used to rewrite the governing equations of nano tubes motion and the results are compared with the classical results. In this modeling, the axial force and the mid-plane... 

A low-carbon steel, containing 0.05 C, 0.203 Mn and 0.0229 Si (all in wt%) rapidly annealed in temperature range 300 ºC - 900 ºC, after severe plastic deformation (SPD) by constrained groove pressing (CGP). Microstructure evolution was investigated by Scanning Electron and Optical Microscopy. Mechanical properties were evaluated by hardness measurements and Shear Punch Testing (SPT). The result showed a thermal stability at 300 ºC and 400 ºC, which recrystallization did not occurred in these temperatures up to 2 h holding time. By annealing at 500 ºC and 600 ºC, the onset of recrystallization observed after holding times of 10 min and 20 s, respectively. Predicting the kinetic of... 

Mobile Sources are the main source of air pollutant emission in Tehran, the capital city of Iran. Everyday thousands of vehicles commute in roads and highways. Unfortunately, People are exposed to high level of particulate matter and gaseous contaminants in automobile cabins. Even though this environment is exposed to high pollutant concentration emitted by on-road vehicle, In comparison with other built environment, in-cabin commuter exposure and its key parameters has never been quantified. In general, this work entails measurement of in-cabin air quality, predicting mathematical models for calculating Air-Exchange-Rate (AER) in vehicles and on-road vehicle emission measurement. Our... 

A Coiled Carbon Nanotube (CCNT) can be geometrically viewed as a graphene sheet whose rolled and twisted to form a helically coiled nanotube. It is the strongest material ever measured with strengthexceeding more than hundred times of steel.The strength of a CCNT iscritically influenced by temperature, tube diameter, strain rate and pitch angle. In this study,a Molecular Dynamics (MD) simulationis performed to understand the effect of temperature, strain rate, tube diameter and pitch angle on the mechanical properties of CCNTs. Results indicate thatexisting the stone-wales defects is necessaryfor thermodynamic stability of CCNTs.According to the stress-strain curves it was observed thatyield... 

Interfacial Tension (IFT) behavior of crude oil/CO2 system is recognized as the main factor affecting the efficiency of CO2 flooding during enhanced oil recovery (EOR) process. Adding paraffin group hydrocarbon to asphaltenic crude oils as an asphaltene precipitant component is aimed to mimic asphaltene precipitation process during crude oil production and transportation. Asphaltene precipitation would critically effects the IFT behavior of crude oil/CO2 systems. In the first part of this study, the equilibrium densities of oil samples which contain different heptane ratio were measured at different pressures and the temperature of 323 K. Then, the equilibrium IFT between CO2 and the crude... 

Nowadays, the reduction of crude oil quality and the growth of environmental restrictions are the main challenges in oil refineries worldwide. The high demand of lighter refinery products and the shrinking market of the heavy products, highlighted the role of heavy residues conversion technologies.Gasification technology consumes these heavy refinery residues and produces clean syngas. By this way and the integration of gasification with power generation cycles, more value added products such as electrical energy, steam and hydrogen can be provided. For this aim to be achieved, three different scenarios are developed and investigated in this project. The first scenario includes the... 

Sulfur containing compounds are known as the most applicable group of organic compounds. Due to their medicinal and biological applications, dithiocarbamates are the most considerable among the many sulfur containing compounds. There are many procedures reported to synthesize these compounds as synthetic intermediates instead of thiophosgen and isothiocyanates. The reaction of amine and carbon disulfide is reported as the best and least hazardous way to synthesize this functional group. In this project heterocyclic compounds such as thiazoles, thiazolidine-2-thione, and 2-(alkylthio)thiazol-4(5H)-one derivatives were synthesized from the reaction of prepared dithiocarbamates with in situ... 

There is increasing evidence that injecting modified brines has a significant impact on the amount of oil recovered, but the exact mechanism by which this occurs is an unsettled issue, and is supposed to be a cause of the complex interactions occurring between the phases insitu. In this thesis, surface chemistry of smart water has been investigated. Fluid/solid and fluid/fluid interactions for Bangestan crude oil in tfhe presence of designed solutions and a set of dilutions of Persian Gulf seawater have been studied and compared. Fluid/solid interactions were investigated through wettability studies. Impact of salinity and ionic composition on this interaction was measured through contact... 

In the current work, jatropha oil was studied in the hetrogenious solid catalytic transesterfication reaction. For this perpous, KOH/CNT catalyst which was prepared by dry impregnation method was used. SEM, XRD and TGA were applied for the catalyst characterization. The results showed that for the KOH/CNT catalyst, by increasing the loading of KOH, the activity of the catalyst increased and the most active catalyst was prepared by 20% loading of KOH. The optimum conditions for transesterfication reaction in the percense of this catalyst were: 4.7% catalyst weigth and the 24.5 molar ratio of methanol to oil and also the reaction time of 2 houres which the rate of reaction at this time is... 

In the current research, Anatase-Rutile Titania hollow spheres were synthesized using hydrothermally prepared carbon spheres as template. Different calcination temperatures were used to remove carbon template and crysalized Titania. The characterizations for the physicochemical properties of prepared samples were carried out by XRD, FESEM, XPS, DRS, UV-Vis and FTIR.It is found that doping of carbon in the crystal structure of Titania hollow sphere, cause red shift in band gap wavelenght and the absorption wavelength edge was expanded to the visible light region and the additional diffusive electronic states were observed on the valence band spectra of samples.The photoelectric conversion... 

In this research, the effect of feed flow concentration on the separation of gas mixture of carbon dioxide and oxygen was investigated by using supported liquid membrane in the presence of nano particles. In order to achieve this purpose, supported liquid membranes were prepared by impregnating a porous hydrophilic PVDF support with TEG, cyclohexanol, TEG/Fe3O4 nano particles and cyclohexanol/ Fe3O4 nano particles. Permeability and selectivity of mixed gases CO2 and O2 were examined at five different CO2 concentrations in feed flow, constant feed flow rate and constant total pressure difference.
In all tests, the permeance of carbon dioxide through cyclohexanol and TEG membranes was... 

By increasing growth of the composite materials and achieving nano-materials and understanding the unique and specific properties, using materials for production with ideal specifications widely spread. So far nano-materials were used for strengthening materials and producing composite and then nano composites were produced.
Regarding to widespread use of polymer matrix composites, nano particles for reinforcement polymers were used. Thus desirable and unexpected properties were observed in polymer matrix nano composites.
In this project, due to the unique properties of carbon nano tubes such as high strength and modulus, low density, and high ratio of length to diameter. They are... 

In this work the effect of recycling process and nanometric CaCO3 on the rheological and heat-sealing properties of co-polymer Polypropylene (R40) was studied. Nanocomposites with recycled and neat matrix were prepared with twin extruder. Complex viscosity, dynamic modulus, flexural and tensile properties, impact strength and sealing ability of nanocomposites of neat Co-PP (R40) and Recycled Co-PP (RPP) determined according to the relevant standard specifications.Rheological analysis revealed that incorporation of nanofiller enhances values of Complex viscosity and dynamic modulus, broadening molecular weight distribution (MWD) and decrease cross over point (ωc, GC) for RPP. In this study,...