Papers by Keyword: Electrospinning

Abstract: This research examines the development of a low cost mobile electrospinning system for fabricating nanofiber. The electrospinning system developed in this study consists of a horizontal needle arrangement and a motor which supports the working system that controls the solution flow rate without an external syringe pump. In order to discover the equipment operating conditions for nanofiber fabrication, the distance from the needle to the target was studied. A PVA solution of 8wt% was used and voltage was applied at 13 kV. The needle to target distances were varied from 8-18 cm. At a distance of 10 cm, the SEM images showed that the smallest diameter of the fiber was 119 nm. The average diameter was in the range of 119-240 nm. Concentrations of the 3 different solutions of PVA, PEO and PCL with the variation of voltage at each concentration were studied. The results show the diameter of PVA at 8 wt% and 12%wt are in the range of 127-197 nm and 222-402 nm, respectively. The diameter of PCL solution at a 20 wt% concentration is in the range of 32-60 nm. PEO at 2 wt% and 4wt% was not able to form as a fiber.

Abstract: In this work, Carbon Nanofiber mates (CNF) were fabricated by carbonization of electrospun non-conducting PolyAcryloNitrile (PAN) and PAN/PolyvinylAlcohol (PVA) nanofiber mates at 1100°C. PAN acts as a carbon source while PVA acts as a scarifying material to create porosity which leads to increase the accessible surface area. Two types of samples have been produced, carbon nanofiber mate (CNF) and Porous carbon nanofiber mate (P-CNF). The samples were first characterized by XRD, FTIR and SEM then examined as novel electrodes for supercapacitor applications. The specific capacitance (SC) results of the CNFs based on electrospun PAN mate and P-CNF based on electrospun PAN/PVA mate precursors, were 170 and 202 Fgm^-1 respectively. The porous structure of P-CNF mate not only increased SC but also increased the capacitive retention and cyclic stability at discharging current density three times higher than that applied in case of CNFs. These results confirm that the tailored P-CNFs have potential for lightweight and durable flexible supercapacitor applications.

Abstract: In this study the needle-less electrospinning by means of “Nanospider^TM“ (ELMARCO) as technology for the preparation of fine α-Al₂O₃ fibers with diameters of 0.5 - 1.5 µm is presented. The fabrication consists of three steps: i) preparation of spinning solution, ii) electrospinning of the prepared solution and collection of the composite fibers, iii) calcination of the composite precursor fibers. The electrospun fibers were prepared from polyacrylonitrile/N,N-dimethylformamide (PAN/DMF) polymer solution and Al(NO₃)₃.9H₂O in ratio 1/10/1. Thereafter, the precursor fibers were calcined in the furnace at 900, 1100 and 1200 °C with a rate of 5 °C/min in air. The formation of crystalline phases, surface morphology and diameters of metastable and final alumina fibers were characterized using thermogravimetric analysis, X-ray diffraction analysis, the scanning electron microscopy and transmission electron microscopy. The precursor PAN/Al(NO₃)₃ fibers were amorphous. The thermal treatment leads to the phase transition from γ-Al₂O₃ to α-Al₂O₃ accompanied by removing of polyacrylonitrile (PAN). The fine porous microfibers composed of pure α-Al₂O₃ phase were prepared after calcinations at 1200 °C.

Abstract: In this study, a fine fibers mat were produced from SPEEK/Cloisite solution and the effect of the dope concentration on the fibers morphology was performed.The electrospun fibers were denoted as e-spunCL and fabricated as dense membrane (SP/e-spunCL) by immersing electrospun fibers into half-solidified SPEEK solution The fiber’s mechanical stability study was also conducted. The fibers diameters and morphology were observed by using Scanning Electron Microscopy (SEM).While the mechanical properties of the fibers was observed via tensile strength test. The results showed that as the concentration increased (0.05 wt%, 0.10 wt%, 0.17 wt%, 0.25 wt% and 0.30 wt%), the fibers diameters become larger which varies from 9.257 μm to 495.4 nm. The highest tensile strength among all fibers was recorded from SP/e-SpunCL17 which was found to be 19.96882±1.49458MPa. SP/e-spunCL17 showed the most promising physico chemical properties with the highest water uptake and proton conductivity of 25.87±1.9827 %, 12.12±0.2837 mScm^-1 and the lowest methanol permeability with 1.22±0.3748 x10^-8 cm²s^-1.

Abstract: Biodegradable polymeric fibers with nanoand submicron diameters, produced by electrospinning can be used as scaffolds in tissue engineering. It is necessary to characterize their mechanical properties especially at the nanoscale. The Force Spectroscopy is suitable atomic force microscopy mode, which allows to probe mechanical properties of the material, such as: reduced Young's modulus, deformation, adhesion, and dissipation. If combined with standard operating mode: contact or semicontact, it will also provide advanced topographical analysis. In this paper we are presenting results of Force Spectroscopy characterization of two kinds of electrospun fibers: polycaprolactone and polycaprolactone with hydroxyapatite addition. The average calculated from Johnson-Kendall-Roberts theory Young's modulus was 4 ± 1 MPa for pure polymer mesh and 20 ± 3 MPa for composite mesh.

Abstract: The nanofiber textile was made by electrospinning on device Nanospider LB 500 (Elmarco, CR). The original basic polymer solution contains polyvinyl alcohol and additional supplement: a glyoxal and phosphoric acid for thermal stabilization and copper sulphate as a biotic agent. The concentration of copper sulphate pentahydrate (CuSO₄·5H₂O) in original basic polymer solution was 0.5 and 1% and it follows that the theoretical concentration of copper ions in nanofibers was 0.95 and 1.89%. Subsequently the nanofibers had stabilized by thermal heat (140 °C, 10 min), and by chemical cross linking methods with using of soaking in solution with glutaraldehyde, methanol. The stabilized nanofibers were characterized by scanning electron microscope (SEM) and atomic absorption spectrum (AAS). The results showed that the thermal stabilization did not change nanostructures too much, but subsequent soaking showed, that their structure has changed after 24 hour leaching, the crosslinked points has not sharp line. This measurement leads to conclusion, that the stabilization by heat is not fully absolute. Chemical stabilization nanofibers by glutaraldehyde changed the nanoproperties only in range a few percent and the solubility in water was absolutely completed. The stabilization by methanol has destroyed nanostructures of the fabrics, and the nanofiber textile looks like thin layer or thick membrane. The nanostructures didn't change their character nor after water soaking. The content of copper in nanofiber had measured by (AAS) and thus proved that the copper concentration in nanofiber is independent on original concentration in solution. The next results from this measurement confirm the assumption that the concentrations of copper are dependent on kind stabilization. The next results from this measurement confirm the assumption that the concentrations of copper are dependent on kind stabilization. The stabilization by soaking in stabilization solution leads to decrease of concentration of copper in nanofiber. The thermal stabilization didn't change final content of copper in nanofiber, the stabilization by glutaraldehyde changed the concentration, it was lower by 2 mg/g and the stabilization by methanol made nanofiber with one quarter original value of copper.

Abstract: ZnO nanofibers were successfully prepared by electrospinning a precursor mixture of polyvinylpyrrolidone (PVP)/zinc acetate, followed by calcination treatment of the electrospun composite nanofibers. The effect of applied voltage to the morphology of nanofibers was studied. Both PVP/Zn acetate and ZnO nanofibers were characterized by FESEM and XRD. The results show that the diameter of the nanofibers changed with applied voltage. Results found that the optimum calcined temperature was 500°C to produce continuous ZnO nanofibers.

Abstract: Poly(lactic acid) (PLA) is blended with Poly(ethylene glycol) (PEG) and magnetic nanoparticles (MNPs). A series of mixtures are converted to fibers via electrospinning at room temperature. The fiber diameter of PLA decreases on blending with PEG from 6 down to 3 micrometers and with PEG + MNPs down ca. 1 micrometer. The thermogravimetric study confirms the effect of blending, enhancing the stability on adding PEG to PLA. The magnetic properties of polymer fibers containing different concentrations of MNPs are studied by vibrating sample magnetometer. The fiber blends shows proportionally reduced saturation magnetization compared to pure magnetic nanoparticles. The MNPs –incorporated PLA-PEG nanocomposite mat show magnetization and therefore promise the possibility for temperature effects, such as hyperthermia treatment.

Abstract: In this study, we fabricated poly vinyl alcohol/polyamide 6 (PVA/PA6) hybrid nanofiber yarns and examined the influence of PA6 content on tensile properties of hybrid nanofiber yarns. The surface morphology of nanofiber yarns was studied by scanning electron microscope (SEM). The average diameters of nanofibers in pure PA6 and pure PVA nanofibers yarns were 83±12 nm and 187±21 nm, respectively. The results showed that the strength of hybrid yarns was descending for PA6 contents below 16.5 % and ascending for higher contents. Also, by increasing the PA6 ratio in the hybrid yarn, the elongation at break was decreased. Three various models including: Hamburger, simple rule of mixtures (ROM) and hybrid models were applied to predict the tensile behavior of hybrid yarns. This study showed that neither ROM nor Hamburger’s models were capable of predicting the tensile properties of hybrid yarns. Whiles, hybrid model can predict properties with the lowest error (6.44 % error in strength values and 13.06 % error in elongation values prediction). Moreover, this model was modified further for higher performance. Our results demonstrate that the hybrid model can be applied in engineered tensile properties of nanofibrous yarns.

Abstract: The electrospun poly(vinylidene fluoride-co-hexafluoropropylene)/montmorillonite nanofibrous composite membranes (esCPMs) were prepared by electrospinning technique using a mixture of different amounts of montmorillonite (0, 3, 5, 7 and 10 wt%) into 16 wt% of PVDF-HFP polymer solution in 7:3 wt% of acetone and dimethylacetamide as the solvent. The effect of montmorillonite (MMT) on electrospun PVdF-HFP membrane has been studied by XRD, DSC, TGA and tensile strength analysis. It is found that electrospun PVDF-HFP/MMT nanofibrous composite membrane obtained using 5wt% MMT has a higher porosity, electrolyte uptake, ionic conductivity, electrochemical stability window and showed higher specific capacitance and good compatibility with electrode materials.