Papers by Keyword: Electrospinning Technique

Abstract: Now a days, demand for electrical energy is increasing because most of our gadgets and devices based on electricity. Due to the depletion of fossil fuel much more attention is given to renewable energy sources and devices to store that energy. Between these energy storage devices electrochemical energy storage devices has got more attention and among electrochemical energy storage devices, batteries are dominant, but they experience some safety issue, slow charge transfer and cannot meet high power requirement for numerous applications. Thus, as compare to batteries supercapacitor have high power density and fast charge transfer. So much more attention is going on to increase the performance of supercapacitors. In this study, hydrothermal method is used to synthesis rGO/NiO composite and electrospinning to fabricate rGO/NiO composite nanofibers. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) is performed to study morphological and structural properties. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are performed to study the electrochemical behavior. Reduced graphene oxide shows specific capacitance as low as 91.6 F/g. NiO nanostructures, rGO/NiO composite and rGO/NiO composite nanofibers shows specific capacitance of 256.4 F/g, 537.8 F/g and 663.8 F/g respectively.

Abstract: TiO₂ nanofibers were synthesised by means of the electrospun technique, which were annealed at high temperatures to achieve the crystalline phase transformation from amorphous to rutile through anatase and the phase mixture. The chemical stoichiometry of electrospun TiO₂ nanofibers was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. The TEM images showed clearly the formation of TiO₂ nanofibers (NF’s) that exhibit a homogeneous and continuous aspect without the presence of crystalline defects, whose surface morphology depends strongly on the annealing temperature. The crystalline phase transformation was studied by Raman spectroscopy, which revealed that annealed TiO₂ NF’s showed a crystalline phase transformation from amorphous, pure anatase, anatase-rutile mixed, to pure rutile as the annealing temperature increased, which was corroborated by X-ray diffraction and high-resolution TEM. The average grain size, inside the NF´s, increased with the crystalline phase transformation from 10 to 24 nm for anatase-TiO₂ and from 30 to 47 nm for rutile-TiO₂, which were estimated by using the Scherrer-Debye equation. By absorbance measurements at room temperature the band gap energy (E_g) was obtained, which is ranged in 3.75-2.42 eV, caused by the amorphous → anatase → anatase-rutile mixed → rutile crystalline phase transformation.

Abstract: In this work, Li_0.06(K_0.5,Na_0.5)_0.94NbO₃(KNNL) nanofibers were synthesized by sol–gel process and electrospinning technique. The thermal behaviour ofelectrospun fibers was characterized by thermogravimetric analysis (TG) to obtain the calcination temperature range. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM), respectively. The crystal structure was identified by XRD as a single-phase perovskite structure, with orthorhombic symmetry. The microstructure shows that the diameters are in the range of 80–160 nm. The electrospun fibers were calcined from 500°C to 900°C and observed the fiber morphology. With increasing calcination temperature, the fiber diameters decreased until the temperature up to 900 °C the morphology change from cylinder to square or rectangular shape grains.

Abstract: In this study, whey protein concentrate (WPC) and poly (ε-caprolactone) (PCL) composite nanofibers were prepared by electrospinning in the diameter of 50-350nm. Characterization tests of the polymer solutions such as density, viscosity, conductivity was studied. Fourier-transformed infrared spectroscopy (IR) results confirmed that the processed fibers were composed of both PCL and WPC constituents. Morphology of nanofibers composite was observed using scanning electron microscopy (SEM). Moreover the PCL/WPC nanofibers with high WPC content exhibited the maximum tensile strength (about 1.40 MPa).

Abstract: Titanium dioxide nanofibers were fabricated by electrospinning technique. The titania solutions were obtained from adding various types of Ti precursor (Ti(OBu)4, Ti(OiPr)4, and Ti(OPr)4) to an ethanol solution containing polyvinyl pyrrolidone (PVP). Acetic acid was used to stabilize the solution and to control the hydrolysis reaction. The porous and well-defined crystalline structure was obtained after calcined at 450oC for 1 h. The thermal behavior, phase composition including crystallite size, as well as the morphology of as-synthesized nanofibers was obtained from thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The average diameter of these nanofibers was in the range from 100 to 400 nm depending on titania precursor. The photocatalytic activity of TiO2 fibers were evaluated for NOx degradation in a gaseous phase. The results demonstrated that at the same catalyst loading, the photocatalytic activity of TiO2 nanofiber was higher than the commercial Degussa P-25.