화학공학소재연구정보센터
Materials Chemistry and Physics, Vol.148, No.3, 846-853, 2014
Hierarchically porous carbon membranes containing designed nanochannel architectures obtained by pyrolysis of ion-track etched polyimide
Well-defined, porous carbon monoliths are highly promising materials for electrochemical applications, separation, purification and catalysis. In this work, we present an approach allowing to transfer the remarkable degree of synthetic control given by the ion-track etching technology to the fabrication of carbon membranes with porosity structured on multiple length scales. The carbonization and pore formation processes were examined with Raman, Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements, while model experiments demonstrated the viability of the carbon membranes as catalyst support and pollutant adsorbent. Using ion-track etching, specifically designed, continuous channel-shaped pores were introduced into polyimide foils with precise control over channel diameter, orientation, density and interconnection. At a pyrolysis temperature of 950 degrees C, the artificially created channels shrunk in size, but their shape was preserved, while the polymer was transformed to microporous, amorphous carbon. Channel diameters ranging from similar to 10 to several 100 nm could be achieved. The channels also gave access to previously closed micropore volume. Substantial surface increase was realized, as it was shown by introducing a network consisting of 1.4 x 10(10) channels per cm(2) of 30 nm diameter, which more than tripled the mass-normalized surface of the pyrolytic carbon from 205 m(2) g(-1) to 732 m(2) g(-1). At a pyrolysis temperature of 3000 degrees C, membranes consisting of highly ordered graphite were obtained. In this case, the channel shape was severely altered, resulting in a pronounced conical geometry in which the channel diameter quickly decreased with increasing distance to the membrane surface. (C) 2014 Elsevier B.V. All rights reserved.