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Preparation and Characterizations of Anisotropic Chitosan Nanofibers via Electrospinning
R. Nirmala,Baek Woo Il,R. Navamathavan,Mohamed H. El-Newehy,김학용 한국고분자학회 2011 Macromolecular Research Vol.19 No.4
We report the preparation of anisotropic chitosan nanofibers prepared using an electrospinning technique. The effect of electrospinning on the formation of nanofibers was examined from results of bulk chitosan. The morphological, structural characterizations and thermal properties of the chitosan bulk and electrospun nanofibers were analyzed by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), Fourier transform infrared (FTIR), and Raman spectroscopy. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) was performed to accurately characterize the high aspect ratio nanofiber structure by the direct identification of mass resolved chains. FE-SEM showed that the electrospun chitosan nanofibers had diameters ranging from 10 to 1,200 nm with an anisotropic nature. MALDI-TOF revealed the presence of lower mass group protonated amino groups, which was the main constituent for the formation of the ultrafine nanofibers in chitosan.
Preparation and Properties of Low-dielectric-constant SiOC(-H) Thin Films Deposited by Using PECVD
R. Navamathavan,이철로,R. Nirmala,김창영,Chi Kyu Choi 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.3
Low-dielectric-constant SiOC(-H) films were deposited on p-type Si(100) substrates by using plasma enhanced chemical vapor deposition (PECVD) with methyltriethoxysilane (MTES) and oxygen gas as the precursors. The SiOC(-H) films were deposited at various substrate temperatures while all the other experimental parameters were kept constant. The SiOC(-H) film’s properties,such as the deposition rate, refractive index, thickness, current-voltage (C-V) characteristics and the dielectric constant, were evaluated. The deposition rate decreased with increasing substrate temperature. The activation energies of the SiOC(-H) films were found to be -0.036 and -0.021 eV,for lower substrate temperature (RT - 200 C) and higher substrate temperature (beyond 200 C),respectively. When the substrate temperature was increased, the precursor molecules dissociated completely due to a breaking of the cage structures (voids), resulting in the formation of denser SiOC(-H) films. The dielectric constant of the SiOC(-H) film increased from 2.53 to 2.96 with increasing substrate temperature from RT to 350 ℃.
R. Navamathavan,김창영,최치규,Heon Ju Lee 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.5
We report on the electrical conduction of as-deposited and annealed SiOC(-H) films deposited by using plasma enhanced chemical vapor deposition (PECVD). The leakage current density was reduced to a low value of 3.02 × 10−8 A/cm2 for the film annealed at 400 ˚C. Both Schottky and Poole-Frenkel emissions were observed to occur in all SiOC(-H) films deposited at different flow rate ratios. However, both emissions were found to be more dominant with increasing flow rate ratio, which may be due to the lower surface state density with increasing flow rate ratio. Furthermore, annealing of the SiOC(-H) film significantly enhanced the electrical properties. The leakage current density was reduced by about one order and the breakdown strength was increased from 1.61 for the as-deposited sample and to 2.81 MV/cm for sample annealed at 400 ˚C for a flow rate ratio of 90 %. The value of the dielectric constant calculated from the I-V plots was consistent with that calculated from the C-V measurements. We report on the electrical conduction of as-deposited and annealed SiOC(-H) films deposited by using plasma enhanced chemical vapor deposition (PECVD). The leakage current density was reduced to a low value of 3.02 × 10−8 A/cm2 for the film annealed at 400 ˚C. Both Schottky and Poole-Frenkel emissions were observed to occur in all SiOC(-H) films deposited at different flow rate ratios. However, both emissions were found to be more dominant with increasing flow rate ratio, which may be due to the lower surface state density with increasing flow rate ratio. Furthermore, annealing of the SiOC(-H) film significantly enhanced the electrical properties. The leakage current density was reduced by about one order and the breakdown strength was increased from 1.61 for the as-deposited sample and to 2.81 MV/cm for sample annealed at 400 ˚C for a flow rate ratio of 90 %. The value of the dielectric constant calculated from the I-V plots was consistent with that calculated from the C-V measurements.
A Study on Electrospun Nylon-6/TiO2 Composite Nanofibers
R. Nirmala,Jeong Jin Won,김학용,R. Navamathavan,Yi Chuan,Mohamed El-Newehy,Salem S Al-Deyab 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10
We report on the preparation and the characterization of TiO2 nanoparticles incorporated with nylon-6 composite nanofibers by using electrospinning technique. Two different composite nanofiber mats with TiO2 nanoparticles sizes of 20 and 300 nm were prepared. The resultant nanofibers exhibited good incorporation of TiO2 nanoparticles. The doping of TiO2 nanoparticles into the nylon-6 nanofibers was confirmed by using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy. The measurement of the electrical conductivity of the TiO2 nanoparticles incorporated with nylon-6 nanofibers were carried out. Current-voltage (I–V) characteristics revealed that the current was enhanced for the sample with 300 nm TiO2 nanoparticles compared to that with 20-nm TiO2 nanoparticles.