PRODUCTION OF POLYANILINE COMPOSITE CONTAINING Fe2O3 AND CoO WITH NANOMETER SIZE USING HYDROXYPROPYLCELLULOSE AS A SURFACTANT

In this study, composite of polyaniline containing Fe2O3 and CoO with nanometer size was synthesized by a chemical method using hydroxyl-propylcellulose as a surfactant. The characteristics of products such as morphology and conductivity were studied. The results indicate that, the morphology and conductivity of product are dependent on the surfactant, the type and concentration of metallic oxide

N-2-BET surface area and FESEM studies of lime-stabilized montmorillonitic and kaolinitic soils

In this research, field emission scanning electron microscopy coupled with an energy-dispersive X-ray analyser was employed to study the micro-textural features and elemental composition of lime-stabilized soil. This technique was used to visualize the time-dependent morphological changes in different clay mineral structure and, moreover, to observe the formation of new cementing products that could not be detected by X-ray diffraction method. Due to the “surface associated” nature of soil–lime reactions, the N2-BET surface area of treated soils was also monitored with curing time. Unconfined compressive strength test as an index of soil’s improvement was performed on cured samples. Based on the results it was found that the type of cementing compounds that were formed after 8 months of curing was dependent on the type of clay minerals present. Also the progression of pozzolanic reaction was highly sensitive to the impurities present on the surface of soil particles. From an engineering point of view, the lime stabilization technique was effective in increasing the strength properties of natural soils with sodium bentonite (comprised mainly of montmorillonite mineral) showing the highest degree of improvement

Design and production of novel conducting polymer colloids

One of the problems limiting the application of conducting polymers as commercial materials has been the lack of solubility in most common solvents. An alternative approach might be the preparation of sterically stabilized conducting polymer colloids via dispersion polymerization. In general the oxidation of pyrrole and aniline is carried out in the presence of a steric stabilizer to produce a colloidal dispersion. In this work various stabilizers such as PVP, PVA, and PEO were used for colloid formation. The preparation, characterization and electrical properties of polypyrrole and polyaniline colloids have been studied. It was found that type and concentration of stabilizer affects the morphology, electroactivity, conductivity and yield of polymer. Electrocoagulation of colloids onto various substrates was considered. The electrochemical oxidation/polymerization of pyrrole and aniline monomer in the presence of steric stabilizers (PVP, PVA, PEO) and the properties of the resultant polymers was also investigated. Various techniques such as galvanostatic oxidation (constant current), potentiostatic oxidation (constant potential), and potentiodynamic (potential ramp) oxidation were used to initiate this process. It was found that the type and concentration of stabilizer affects the rate of polymerization as well as the electroactivity and morphology of the resultant colloidal sol. It was found that the rate of polymerization and the electroactivity decreased with increased concentration of stabilizer. The effect of rotation rate, type of stabilizer and stabilizer concentration on the rate of polymerization were studied. The results indicated that rate of polymerization/deposition decreased with increased electrode rotation rate and with stabilizer concentration. For the first time the use of electropolymerization in the presence of the steric stabilizers with various counterions in order to produce conducting polymer colloids has been investigated. The colloids produced are sterically stable and are electroactive. Applications for conductive polymer colloids were considered. For example, the preparation of conductive electroactive paints has been investigated using polypyrrole and polyaniline colloids mixed with standard acrylic paints. The electroactivity, conductivity and adhesive strength of the resultant paints was investigated. The use of colloids for the development of novel conductive polymer composites was studied. The electrodeposition of mixtures of polypyrrole and polyaniline colloids, polyaniline colloids and pyrrole monomer or polyaniline colloids with polystyrene sulphonate particles was investigated. Thermal degradation of polyethylene in the presence of colloidal polypyrrole and polyaniline was investigated. The results indicated that polypyrrole and polyaniline colloids might be used as a stabilizing additive to prevent the thermal degradation of polyethylene. This study indicated that conducting polymer colloids can be prepared both chemically and electrochemically and these colloids can be used for various applications

Colloidal Preparation of Polyaniline-Poly(vinyl alcohol) - SiO2 Nanocomposite and Study of its Anti-corrosive Properties

Polyaniline (PANI) is one of the most interesting conducting polymers due to its low cost and easy availability of raw materials, easy synthesis, good environmental stability and controllable electrical conductivity and redox properties. In recent years it has been shown that electrically conducting polymers such as polyaniline in integrated coating applications are able to protect steel from corrosion due to formation of passive oxide layer on the metal surface. In this report, a nanocomposite of polyaniline–nanoSiO2 (PSC) has been prepared by using poly(vinyl alcohol) (PVA) as surfactant and ammonium persulfate as an oxidant in the aqueous media. The prepared materials were characterized and compared by Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). In this method different concentrations (1, 3 and 5wt%) of emulsion nanocomposite were each mixed with polyvinyl acetate (PVAc) binder. SEM image showed good distribution of nanocomposite in the polyvinyl acetate matrix. The anti-corrosive properties of this blend on carbon steel in 3.5% NaCl and HCl (1M) were evaluated by Tafel slope analysis. The corrosion inhibition performance study was carried out at room temperature in aqueous solution of 1.0 M HCl and 3.5 % NaCl by using Tafel method. Experiments were carried out in a conventional three electrode cell assembly using Autolab Potentiostat/Galvanostat. The results showed that addition of nanocomposite to PVAc decreased the corrosion rate and corrosion current density. According to the results, the blend of 3 wt% of this nanocomposite with polyvinyl acetate has the best corrosion protection for steel St37 in both media

A comparative study on preprocessing techniques in diabetic retinopathy retinal images: Illumination correction and contrast enhancement

To investigate the effect of preprocessing techniques including contrast enhancement and illumination correction on retinal image quality, a comparative study was carried out. We studied and implemented a few illumination correction and contrast enhancement techniques on color retinal images to find out the best technique for optimum image enhancement. To compare and choose the best illumination correction technique we analyzed the corrected red and green components of color retinal images statistically and visually. The two contrast enhancement techniques were analyzed using a vessel segmentation algorithm by calculating the sensitivity and specificity. The statistical evaluation of the illumination correction techniques were carried out by calculating the coefficients of variation. The dividing method using the median filter to estimate background illumination showed the lowest coefficients of variation in the red component. The quotient and homomorphic filtering methods after the dividing method presented good results based on their low coefficients of variation . The contrast limited adaptive histogram equalization contrast limited adaptive histogram equalization increased the sensitivity of the vessel segmentation algorithm up to 5% in the same amount of accuracy. The contrast limited adaptive histogram equalization technique has a higher sensitivity than the polynomial transformation operator as a contrast enhancement technique for vessel segmentation. Three techniques including the dividing method using the median filter to estimate background, quotient based and homomorphic filtering were found as the effective illumination correction techniques based on a statistical evaluation. Applying the local contrast enhancement technique, such as contrast limited adaptive histogram equalization, for fundus images presented good potentials in enhancing the vasculature segmentation