Yazar "Aksu, Mehmet Levent" seçeneğine göre listele
Listeleniyor 1 - 10 / 10
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Characterization of boron doped Cobalt/Zinc acetate composite fibers(2009) Uslu, İbrahim; Gökmeşe, Faruk; Atakol, Orhan; Aksu, Mehmet LeventPVA/cobalt acetate/zinc acetate doped with boron composite fibers were prepared by electrospinning technique. Electrospinning was performed by putting solutions at different applied voltage in a range from 13 to 18 kV. The fibers were measured and characterized by viscometer, conductiometer (with fourpoint probe), Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The viscosity of the Boron doped solution was higher and favoring the formation of thinner and uniform nanofibers. DSC analysis shows that when boron is added to the polymer it increases the crosslinking and amorphous structure of PVA/ cobalt and zinc acetate composite polymer is increased.Öğe Fabrication and Characterization of Boron Doped Ni/Zn Acetate Nanofibers(TAYLOR & FRANCIS INC, 2009) Uslu, Ibrahim; Öztürk, M. Kemal; Aksu, Mehmet Levent; Gökmeşe, FarukThis study is related to the preparation of boron doped Nickel/Zinc metal fibers prepared by the use of electrospinning technique. The originality of this study is the addition of boron to metal acetates. The addition of boron did not only increase the thermal stability of the fibers, but also increased their diameters, which gave stronger fibers. The FT-IR spectra of the fibers were in good accordance with literature. The differential scanning calorimetry (DSC) results indicate that the glass transition (Tg) and melting temperatures (Tm) showed great change with the addition of boron and boron doped fibers were observed to degrade at higher temperatures. The SEM appearance of the fibers showed that the addition of boron resulted in the formation of cross linked bright surfaced fibers.Öğe Fabrication and Characterization of Boron Supported YBCO Superconductive Nanofibers by Electrospinning(Bentham Science Publ Ltd, 2010) Uslu, İbrahim; Öztürk, Mustafa Kemal; Aksu, Mehmet Levent; Gökmeşe, FarukThis study is related to the preparation of boron supported YBa(2)Cu(3)O(7) (YBCO) superconducting material. The first step was the preparation of a composite formed by mixing yttrium, barium, and copper acetates with polyvinyl alcohol (PVA) at a suitable temperature. The resulting composite polymer was electrospun to produce nanofibers. Finally, the obtained nanofibers were subjected to thermal treatments at 500 degrees C, 600 degrees C and 1000 degrees C to elucidate their morphological properties. The conductivity of the nanofibers was measured by the four probe techniques, and the boron supported polymer was found that it had a higher conductivity. Differential Scanning Calorimetry (DSC) data for the boron doped material revealed that the addition of boron increased the thermal resistance of the fibers. Scanning electron microscopy (SEM) images of the fibers showed that they were homogeneously electrospun, and there was no beading or heaping on them.Öğe Nanofibers by electrospinning of nylon 6 doped with boron(2009) Uslu, İbrahim; Altaş, Ayşenur; Aksu, Mehmet Levent; Gökmeşe, FarukIn this study, Nylon 6 was successfully cross-linked with boron using formic acid as solution. Electrospinning process was performed by putting hybrid nylon 6/boric acid solutions at different applied voltage in a range from 20 to 25 kV using a high voltage power supply. Nylon has been widely used in industry because of its good mechanical properties. The use of boron improves the strength, flame retardant characteristics and flexibility of the nylon 6 fibers. The structures of the nanofibers synthesized are characterized by the Fourier transformed infrared spectroscopy (FTIR), thermo gravimetric and differential thermal analysis (TG/DTA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and scanning electron microscopy (SEM). DSC and TGA analysis revealed that stability of electrospun nylon 6 fiber is higher than non spun sample and increase of boric acid content increases the stability of the polymer. It is observed from the SEM images that the diameters of the fibers decreased with boron content increased. FTIR analysis revealed that all characteristic N-H structures are observed and consistent with literature.Öğe Preparation and characterization of PVA/Boron polymer produced by an electrospinning technique(EUROPEAN POLYMER FEDERATION, 2007) Uslu, İbrahim; Daştan, H.; Altaş, Ayşenur; Yaylı, Ahmet; Atakol, Orhan; Aksu, Mehmet LeventIn this study, poly(vinyl alcohol) were cross-linked with boron in varying concentrations and blend fibers were obtained with diameters ranging from 0.3 mu to 4.0 mu m 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.Öğe Preparation and characterization of PVA/zinc acetate/boron composite fiber(2007) Uslu, İbrahim; Başer, Burcu; Yaylı, Ahmet; Aksu, Mehmet LeventThe 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 ?m. 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.Öğe Preparation and characterization of PVA/Zinc acetate/boron composite fibers(WALTER DE GRUYTER GMBH, 2007) Uslu, Ibrahim; Baser, Burcu; Yayli, Ahmet; Aksu, Mehmet LeventThe 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 mu m. According to the TGA analysis decomposition of zinc acetate from the PVA chain was observed around 273 degrees C, 368 degrees C and 447 degrees 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.Öğe Preparation and Properties of Electrospun Poly(vinyl alcohol) Blended Hybrid Polymer with Aloe vera and HPMC as Wound Dressing(2010) Uslu, İbrahim; Keskin, Selda; Gül, Ali; Karabulut, Tutku Ceren; Aksu, Mehmet LeventA series of poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP)/poly(ethylene glycol) (PEG) hybrid nanofibers were fabricated by an electrospinning method, in order to be used as a potential wound dressing material. The effect of Aloe vera was investigated in terms of solution properties such as viscosity, conductivity, pH and surface tension. The nanofibrous wound dressing materials were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and differential scanning calorimetry (DSC). SEM results revealed that the fiber diameters ranged between 200-500 nm and they were linear, homogenous and free of beads. DSC thermograms indicated that the addition of Aloe vera affects the crystal structure and efficiently cross-links the hybrid polymer, forming an amorphous structure with a melting temperature (Tm) of 219°C at an Aloe vera concentration of 3%. FTIR results clearly resolved the hybrid polymer structure of nanofibers obtained.Öğe Preparation of PVA/Chitosan Doped With Boron Composite Fibers and Their Characterization(2008) Uslu, İbrahim; Çelikkan, Hüseyin; Atakol, Orhan; Aksu, Mehmet LeventIn this study, chitosan and poly(vinyl alcohol) were cross-linked with boron in varying concentrations and chitosan and poly(vinyl alcohol) blend fibers were obtained with electrospinning process. Viscosity and electrical conductivity results revealed that the increase in chitosan and boron content increased the viscosity of the solution and but decreased the electrical conductivity of the fibers. The peaks obtained with FT-IR analyses were in good agreement with literature. SEM micrographs also showed that wavy and curly fibers with relatively small diameters were obtained as the chitosan and boron concentrations were increased. Thermogravimetric data revealed that the formation of a more stable polymer structure as a result of the cross linking with boron.Öğe Thermoelectric Properties of Nickel and Boron Co-Substituted NaCo2O4 Prepared by Electrospinning Technique(TRANS TECH PUBLICATIONS LTD, 2018) Erdal, Mehmet Okan; Koyuncu, Mustafa; Aksu, Mehmet Levent; Uslu, Ibrahim; Koçyiğit, SerhatIn this study nickel and boron doped sodium cobalt oxide NaCo2-xNixByO4 (0 <= x <= 0.3, 0 <= y <= 0.1) nanocrystalline thermoelectric ceramic powders were synthesized using electrospinning techniques and then consolidated into bulk ceramics. The differences in the microstructure and thermoelectric properties of the samples as a result of doping effect have been investigated. The crystalline structures of the powders and nanofibers were characterized using Xray diffraction and scanning electron microscopy and BET Analysis before and after the calcination process at different temperatures. Nanofibers prepared by the use of electrospinning technique, have a diameter of approximately 300 nm, and the diameter of the grains of calcined powders was observed to range between 150 to 500 nanometers. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system (Lot-Oriel PPMS) in a temperature range of 15-300 K. The calculated values of dimensionless figure of merit at 300 K are 4.25 x 10(-5), 5.3 x 10(-6), 8.6 x 10(-5) and 9 x 10(-6) for sintered powders from undoped, Ni and B doped powders, respectively.
