Mansoor Keyanpour-Rad

MORPHOLOGICAL AND OPTICAL CHARACTERIZATION OF ELECTROSPUN ZINC OXIDE NANOFIBERS

A combination of the remarkably simple technique of electrospinning, developed to fabricate polymer nanofibers, and sol–gel processing has been utilized to produce fine zinc oxide nanofibers with an average diameter of 70 nm. A non-toxic precursor solution of polyvinyl alcohol and zinc acetate was electrospun and the resulting fibers were then calcined at a relatively low temperature to produce ZnO nanofibers. Simultaneous thermal analyses were used to study the formation of ZnO nanofibers from the precursor material. X-ray diffraction was employed to analyze the phases and different microscopy techniques, such as scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to study the morphology and size of the fibers. Fourier transform infrared spectroscopy was employed to investigate the composition of the precursor and ZnO fibers. The specific surface area of the electrospun nanofibers was determined using the Brunauer–Emmett–Teller method and optical properties were measured by UV-Vis and PL spectroscopy. The very high specific surface area of the ZnO fibers makes them potential candidates for nanodevice applications in gas sensing, dye-sensitized solar cells, and UV/blue emission devices.

Impedance Characteristics of Electrospun Nylon-6/TiO2 Nanocomposite for Humidity Sensor

Resistive relative humidity (RH) sensors were fabricated by nano composites of nylon-6 and titanium dioxide nanopowders. The results indicated that these sensors can be fabricated as a reliable, low cost and fast response instruments. Different percentages of nylon-6 and TiO2 were studied and average diameters of the resultant nanofibers were found the 80 to 120 nm. The nano composite of nylon-6/TiO2 nanofibers was electrospun on the interdigital gold electrode on the glass substrate. It was found that the impedance of the mat ranged from 107 Ω to 102 Ω while the relative humidity was increased from 11% RH and 97.3% at room temperature. Transition electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the morphology of the nano composite.

Photocatalytic Decolorization of Red Dye in Aqueous ZnO-TiO2 Suspensions

The photocatalytic decolorization of aqueous solutions of Direct Red 27 in the presence of various amounts of semiconductor powder suspensions has been investigated in a batch reactor with the use of artificial light sources. ZnO and TiO2 have been found the most active photocatalysts; the effect of catalyst loading and type on the reaction rate was optimized for maximum degradation. The results imply that 1:1 ratio is proper for the photocatalytic removal of Direct Red 27. In addition, the effects of particle size and surface area were examined in this photocatalytic process. The results showed that the decolorization efficiency increases with increase in surface area, and decrease in powder size. The efficiency is related to mechanism of reactions on the active sites of the catalyst surface and broad adsorption of compounds with different band gaps

Atmospheric tail-pipe emissions from motorcycles in Tehran, Iran

Worsening environmental conditions in large cities of Iran, such as Tehran, are impeding economic development and creating adverse health consequences. As a common means of transportation, the number of different brands of motorcycles has grown rapidly in Tehran over the past few years. In this study the tail-pipe emissions of randomly selected 2- and 4-stroker have been measured and studied. Motorcycles currently being used in Tehran were tested for carbon monoxide (CO), carbon dioxide (CO2), and hydrocarbons (HC) and compared with emission standards already enforced in some Asian countries like China and Taiwan. It was found that the emissions of CO from some common 4-stroke motorcycles were much higher than from 2-stroke ones, while the CO2 emissions were almost equal to HC emissions for the 2-stroke motorcycles, which was approximately 14000 ppm for all brands. Except for one of the brand of the 4-stroke motorcycles, emissions of HC were less than 1000 ppm.

ELECTROSPINNING OF CONTINUOUS CARBON NAONOFIBER-FILLED COMPOSITE FIBERS

In order to translate the superior properties of carbon nanofibers (CNFs) to macro-scale structures, an electrospinning route capable of placing CNFs into a continuous nano-scale composite fibril is introduced. In this work, composite fibers were produced by electrospinning solution of polyacrylonitrile (PAN) with carbon nanofibers dispersed in dimethylformamide (DMF), which is an effective solvent for carbon nanofibers. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) demonstrated rough and globular surfaces on the CNF containing fibers. Raman spectra confirmed the presence of CNFs in the polymer fibers prepared employing the electrospinning method. Raman observation served as the direct evidence of successful filling of PAN fibers with CNFs and complemented the results obtained by SEM and AFM studies.

Dependency of polycyclic aromatic hydrocarbon concentrations on particle size distribution in Tehran atmosphere

In this work, the airborne particulate matter with an aerodynamic diameter less than 10 µm (PM10) was fractionated in a six-stage high-volume cascade impactor to identify particulate size distribution in Tehran atmosphere. The study was conducted at 15 sites located in the north, south, east, west, and central parts of Tehran in 2005. Air samples were analyzed for 16 polycyclic aromatic hydrocarbons (PAHs) by HPLC. The daily PM10 concentrations at the peak of traffic in roadside areas were found to be 106–560 µg m−3. The cumulated concentration sum of PAHs, based on 16 species, was found to have an average concentration of 380 ng m−3. Furthermore, it was found that more than 60% of PAHs belonged to the small particulate size range, having sizes of less than 0.49 µm, some containing benzo(ghi)perylene and indeno(123cd)pyrene (high molecular weight) with average concentrations of 8 and 6 ng m−3 and fluorene, phenanthrene, and fluoranthene (low molecular weight) with average concentrations of 14, 13, and 19 ng m−3, respectively. In addition, the results revealed that the lighter three- and four-ring PAH compounds were the most abundant pollutants in the air collected at all the sampling sites.

Modification in Synthesis of Anatase Titanium Oxide and Comparison of the Synthesis Methods

In this research work, anatase titanium dioxide (TiO2) was prepared by precipitation route using TiCl4 in neutral pH. The dehydration of precipitate was performed by azeotropic extraction using benzene as solvent. After calcinations of product at 600 °C anatase form of titania was confirmed by XRD analysis. Precipitating TiCl4 in pH=3 gives a product of mostly rutile and anatase. The sizes of titania nanoparticles obtained was less than 30 nm as determined by transmission electron microscopy (TEM) studies. In the other method of synthesis, titanium tetra isopropoxide was used in neutral pH. After calcinations of product at 600 °C, most of the titania obtained was brookite and anatase. Increasing the pH by addition of ammonia, Ti (OH)xCl4−x will be formed first, and this increases the concentration of hydroxyl group in solution. In general when pH is higher, the amount of x in Ti(OH)xCl4−x is more. FT‐IR studies before calcination revealed that even in neutral pH this composition is present. Meanwhile the ...

Effects Of Nanoscale Surface Defects On Electropolymerization

Surface defects on the substrate electrode have significant effects on electropolymerization processes. Influence of surface defects mechanically formed on a Pt electrode on electrochemical polymerization of aniline was investigated. Interestingly, it was found that existence of such surface defects leads to more favorable electropolymerization. In this case, surface defects acts as nucleation centers for subsequent growth of the conductive polymer. This is accompanied by the formation of denser polymer film with smoother surface. This smoothness also exists in nanoscale. These are interesting advantages for application purposes.