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Advanced filters: Author: Hiroyoshi Kawakami Clear advanced filters

  • Effects of processing parameters, such as applied voltage, feed rate, viscosity of polymer solution, salt as additive and humidity in electrospinning, on morphologies such as diameter and uniformity of nanofibers were investigated, and preparation of bead-free ultrafine uniform nanofibers was carried out. Nanofibers fabricated from fluorinated polyimide indicated an ultrafine uniform diameter and, finally, we succeeded in preparing a uniform nonbeaded nanofiber with a diameter of less than 40 nm.

    • Satoshi Fukushima
    • Yuki Karube
    • Hiroyoshi Kawakami
    Research
    Polymer Journal
    Volume: 42, P: 514-518

  • Research on composite electrolyte membranes composed of polymer nanofibers and a polymer matrix has attracted significant interest because of their improved ion conductivity, excellent membrane durability, and ability to fabricate thinner membranes. Polymeric nanofiber-containing polymer electrolyte membranes are expected to be applied not only to electrolyte membranes for fuel cells and water electrolysis but also to all-solid-state Li-ion batteries. This focus review presents the latest information on these topics.

    • Hiroyoshi Kawakami
    ReviewsOpen Access
    Polymer Journal
    Volume: 57, P: 623-633

  • Novel electrical conductive carbon nanofibers were prepared by a combination of electrospinning and ion-beam irradiation techniques. Four types of polymer nanofibers, including polyimides (6FDA-6FAP and 6FDA-APPS), polysulfone and polyacrylonitrile, were prepared by the electrospinning method. The obtained polymer nanofibrous membranes were irradiated by Kr+ to give carbonized nanofibers. Electrical conductivities of the electrospun 6FDA-6FAP nanofibrous membrane reached up to ca. 10−1 S cm−1 with 1016 ion cm−2 of Kr+. The influences of starting polymers on electrical conductivity of the carbon nanofibers were studied by Raman and X-ray photoelectron spectroscopy analyses.

    • Katsuya Sode
    • Tomoki Sato
    • Hiroyoshi Kawakami
    Research
    Polymer Journal
    Volume: 45, P: 1210-1215

  • Novel core/shell-like structured ultrafine branch nanofibers were successfully fabricated by a phase-separation process using simple polymer blend (polyacrylonitrile (PAN) and fluorinated polyimide (PI)) solutions with electrospinning. The obtained core/shell-like structured branch nanofibrous membranes showed strong hydrophobicity based on the hydrophobic shell polymer and ultrafine branch nanostructures. This simple process could be used to prepare core/shell structured branch nanofibers composed of other blend polymers and would also provide novel opportunities for industrial applications, such as nanocoating, nanoreinforcement, nanocomposite, nanomedicine and a drug-release system.

    • Makoto Konno
    • Yuuko Kishi
    • Hiroyoshi Kawakami
    Research
    Polymer Journal
    Volume: 46, P: 792-799

  • This Focus Review provides an overview of our recent study and related work on ion conductive polymer nanofibers and their applications in polymer electrolyte fuel cells. We succeeded in evaluating the intrinsic proton and anion conductivity of electrospun nanofibers and revealed their distinguished ion conductive properties, which were quite different from those of the corresponding polymer membranes. These ion conductive nanofibers have potential utility as polymer electrolyte composite membranes to improve fuel cell performance by utilizing efficient ion conduction both inside and at the surfaces of nanofibers.

    • Manabu Tanaka
    Reviews
    Polymer Journal
    Volume: 48, P: 51-58