İbrahim Uslu

Preparation and Characterization of PVA/PVP Nanofibers as Promising Materials for Wound Dressing

The PVA/PVP, PVA/PVP with 5% and 10% chitosan and PVA/PVP-Iodine fibers were produced via electrospinning technique. Their morphological and chemical characteristics were examined with SEM, TGA, FT-IR, viscometer and four-point probe conductivity measurement apparatus. The addition of chitosan increased the viscosity and the electrical conductivity of the polymer. The increase chitosan contents resulted in the diameters of the fibers smaller than expected. This was attributed to the increase in the viscosity of the solution and the electrical conductivity of the resulting fibers. The DSC results show that iodine was efficiently cross-linked with the polymer, forming an amorphous structure.

Frequency and Temperature Dependence of Dielectric Properties of Au/Polyvinyl Alcohol (Co, Ni-Doped)/n-Si Schottky Diodes

The dielectric properties and AC conductivity of Au/polyvinyl alcohol (Co, Ni-doped)/n-Si Schottky diodes (SDs) were investigated in the frequency range 1 kHz–1 MHz and in the temperature range 80–400 K. The frequency and temperature dependence of dielectric constant (ϵ′), dielectric loss (ϵ″), loss tangent (tan δ), AC electrical conductivity (σ ac ) and the real and imaginary parts of the electric modulus (M′ and M″) were found to be a strong function of frequency and temperature. The values of ϵ′, ϵ″ and tan δ decrease with increasing frequency, while they increase with increasing temperature, especially above 275 K. The values of σ ac increase with both increasing frequency and temperature. Such temperature-related behavior of σ ac can be attributed to the high mobility of free charges at high temperature. Electric modulus formalism was also analyzed to obtain experimental dielectric data. The values of M′ and M″ increase with increasing frequency, while they decrease with increasing temperature. The interfacial polarization, which more easily occurs at low frequencies and high temperatures, consequently contributes to the improvement of the dielectric properties of SDs.

Preparation and Characterization of Neodymia Doped PVA/Zr-Ce Oxide Nanocrystalline Composites via Electrospinning Technique

In this study, neodymia doped poly(vinyl) alcohol/zirconium–cerium acetate (PVA/Zr-Ce) nanofibers were prepared using the electrospinning technique, and then calcined at 800°C for 2 hours. For this purpose, PVA/Zr-Ce polymer solutions doped with different concentrations of neodymia were prepared using electrospinning technique, and then calcined and sintered at 800°C for 2 hours. The effect of neodymia doping was investigated in terms of solution properties, morphological changes and thermal characteristics. The fibers were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The measurements showed that the conductivity, pH, viscosity, and surface tension of the hybrid polymer solutions have decreased with increasing Nd acetate content. The FT-IR spectra of the fibers were in good accordance with the literature. The average crystal size values for calcined and sintered samples which were obtained from precursor solutions were calculated. XRD analysis showed that the crystallite size was decreased with increasing Nd content. This result is verified by the calculation of the total areas of the peaks appeared in the XRD spectra. The very sharp and high intense peaks found in the diffraction patterns revealed the crystalline nature of the product. Moreover, the SEM micrograph of the fibers showed that the average fiber diameters decreased with increasing Nd content.

Synthesis and Characterization of Poly(vinyl alcohol)/Poly(vinyl pyrrolidone)-Iodine Nanofibers with Poloxamer 188 and Chitosan

This study focuses on the fabrication of poly(vinyl alcohol)/ poly(vinyl pyrrolidone)-Iodine nanofibers via electrospinning. Electrospun fibers were characterized by FT-IR, DSC and SEM techniques. DSC results indicated that the thermal stability of nanofibers were improved after the addition of chitosan and poloxamer 188. SEM images showed that the spongiform structure is much more compact and fibrous in the case of added chitosan, with an average fiber diameter of 374 nm, whereas the addition of poloxamer 188 resulted in a more porous and beaded composition, with average fiber diameter of 489 nm.

Powder characteristics and microstructure of uranium dioxide and uranium dioxide-gadolinium oxide fuel

Three different fuels UO2-only, UO2-Gd203(5%), and UO2-Gd203(10%) were produced by sol-gel technique. Their powder characteristics such as flowability, BET surface area, average pore diameter, and cumulative pore volume were determined. The pore size distributions of powders, green pellets, and sintered fuels were determined by using a mercury porosimeter. The theoretical densities of sintered fuels were found to be 98.01, 95.3, and 95.9%, respectively. Their ruggedness fractal dimensions were 1.111, 1.044, and 1.042, while the fractal dimensions associated with the size distribution of grains were 1.44, 1.58, and 1.60, respectively.

Promising Materials for Wound Dressing: PVA/PAA/PVP Electrospun Nanofibers

In this study, PVA/PAA, PVA/PAA/PVP, PVA/PAA/PVP-I and PVA/PAA/PVP/Chitosan fiber mats were prepared via electrospinning. Synthesized nanofibers were characterized by DSC, FT-IR and SEM. DSC results showed that the nanofibers were degraded at 400°C and 450°C. The addition of PVP-K30, PVP-I and chitosan to PVA/PAA structure increased the thermal stability of the nanofibers. SEM micrographs showed that synthesized nanofibers are linear. Fiber diameter measurements showed that average diameters of the fibers are less than 0.5 micron. The average diameters of PVA/PAA, PVA/PAA/PVP, PVA/PAA/PVP-I and PVA/PAA/PVP/Chitosan fibers were calculated as 458 nm, 237 nm, 139 nm, and 270 nm, respectively.

PVA/PAA-Based Antibacterial Wound Dressing Material with Aloe Vera

The incorporation of drugs into the dressings make these dressings antimicrobial and help in control of infection around the wound. The wound dressing materials based on PVA/PAA, ciprofloxacin HCl, and aloe vera have been designed and developed so that the wound undergoes proper healing and scar formation is minimal. These wound dressing materials are produced using the electrospinning method. The wound dressing materials are characterized using the FT-IR, DSC, DTA, TGA, and SEM techniques. The wound dressing materials are tested for microbial activity tests and drug release experiments. Controlled ciprofloxacin HCl release is observed.

Preparation and Characterization of PVA/Boron Polymer Produced by an Electrospinning Technique.

Abstract In this study, poly(vinyl alcohol) were cross-linked with boron in varying concentrations and blend fibers were obtained with diameters ranging from 0.3 μ to 4.0 μm with the use of electrospinning process. The resulting product was characterized by SEM, DSC, and FT-IR techniques. There is no beading tendency in either boron doped or undoped fibers. When the amount of boric acid in PVA solutions was increased the conductivity of the polymer decreased. The data indicated the existence of boron oxide in the polymeric structure and the formation of B-O-C bond. SEM micrographs reveal that higher viscosity favors the formation of thicker fibers. Boron addition seems to disturb the easy detachment of the fibers from the tip of the Taylor Cone

Electrical characteristics of Au/n-Si (MS) Schottky Diodes (SDs) with and without different rates (graphene + Ca1.9Pr0.1Co4Ox-doped poly(vinyl alcohol)) interfacial layer

In order to see effects of interfacial (with and without different graphene (GP) + Ca1.9Pr0.1Co4Ox-doped PVA) layer on the electrical characteristics of conventional Au/n-Si (MS) contacts. Therefore, Au/(GP + Ca1.9Pr0.1Co4Ox-doped PVA)/n-Si (MPS) structures were fabricated with different rates of (%3 GP, %7 GP) PVA and were fabricated on same n-Si wafer. Au/n-Si (MS), Au/PVA/n-Si, Au/%3GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si and Au/%7GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si structures were fabricated and their main electrical characteristics compared each other by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of with and without GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si at room temperature were studied to investigate its main electrical parameters. The energy density distribution profile of the interface states (Nss) was obtained from the forward bias I–V data by taking into account voltage dependent ideality factor (n(v)) and effective barrier height (Φe) and they increase from at about mid-gap energy of Si to bottom of conductance band edge. In addition, voltage dependent profile of resistivity of the structure was obtained from I–V data for four different structures. The analysis of experimental results reveals that the existence of GP + Ca1.9Pr0.1Co4Ox-doped PVA interfacial layer improves the performance of MS structure. In order to determine the dominant current-transport mechanism (CTM) in the whole forward bias region of these structures, the double logarithmic forward bias I–V plots were also drawn. These plots exhibit two distinct linear region with different slopes which are corresponding to intermediate and high forward bias voltages. The slope of these plots show that in the region 1 (low biases) the dominant CTM is trap-charge-limited current (TCLC), whereas in the region 2 (high biases) is space-charge-limited current (SCLC) for four diodes.

Preparation and Characterization of PVA/Zinc Acetate/ Boron Composite Fibers

Abstract The objective of this work was to synthesize boron incorporated PVA/Zinc acetate nano precursor composite polymer fibers using electrospinning technique. Produced fibers, are useful reagents in organic synthesis of zinc oxide nano structures which have gained wide interest because of their potential applications in the fabrication of microelectronic devices. Boron incorporated PVA/Zinc acetate not only improve the electrical properties of ZnO films but also has an influence on the crystal structure of ZnO films. The fibers were measured and characterized by conductiometer (with four-point probe), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The formation of boron incorporated PVA/Zinc acetate hybrid polymer was confirmed by FT-IR spectra. SEM micrographs clearly reveal that there are random-growth oriented fibers on aluminum foil with diameters ranging from 0.5 to 1 μm. According to the TGA analysis decomposition of zinc acetate from the PVA chain was observed around 273 °C, 368 °C and 447 °C. Boron incorporated PVA/Zinc acetate nano composite polymer fibers have been successfully synthesized for the first time using electrospinning technique and characterized in detail as precursor material for ZnO. Electrospinning process has been a widely used, simple and versatile method and in future may be used for large-scale preparation of nanofibers of ZnO.