フッ素系高分子からなるイオン穿孔膜の孔径・形状制御; 照射効果の直接利用

Pore size and shape control of fluoropolymer-based ion-track membranes; Direct use of irradiation effect

八巻 徹也; Nuryanthi, N.*; 越川 博; 澤田 真一; 箱田 照幸; 長谷川 伸; 浅野 雅春; 前川 康成; Voss, K.-O.*; Trautmann, C.*

Yamaki, Tetsuya; Nuryanthi, N.*; Koshikawa, Hiroshi; Sawada, Shinichi; Hakoda, Teruyuki; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Voss, K.-O.*; Trautmann, C.*

本研究では、穏和なエッチング条件の下で、より効率的にポリフッ化ビニリデンイオン穿孔膜を作製することを目指し、イオンビーム照射条件が穿孔形成に及ぼす影響を調べた。その結果、化学エッチングが潜在飛跡のみに限定され、その周囲の未照射部(バルク領域)ではほとんど起こらないため、潜在飛跡の構造だけで孔径が決まるという興味深い事実を得た。つまり、他の多くのイオン穿孔膜とは異なり、エッチング条件による複雑な影響を受けることなく、"イオンビームの照射効果を直接利用"することで孔径と形状が制御可能であった。

We investigated the track-structure-dependent pore formation by scanning electron microscopy and conductometry to control the pore size and shape by direct use of the irradiation effect. PVDF films of 25 and 100 m thicknesses were bombarded with heavy ions in the energy range between a few hundred MeV and GeV, and then etched in a 9 M KOH aqueous solution at 80C. A very low bulk-etch rate was seen because of the mild etching conditions and high chemical stability of pristine PVDF. This finding suggests that the differences in the track structure, mainly depending on the LET, would be the most crucial factor of the resulting pore size. The depth distribution of the LET was applied to control the pore shape, in other words, to prepare nanopores with a conical as well as cylindrical shape. Importantly, direct use of the ion-beam irradiation effect without any concern for etching conditions provided this controllability.