Nanoscale Casting Using Supercritical Fluid

Abstract

Porous silica fibers were synthesized by templating activated carbon fibers using supercritical fluid as a solvent. A precursor of silica, tetraethyl orthosilicate was dissolved in supercritical CO₂ and attached to the base-activated carbon. The base-activated carbon in the sample coated with SiO₂ was removed by calcination or O₂-plasma treatment. Not only the fibrous macro shape, but also the meso structure of the base-activated carbon fiber were faithfully replicated in the silica products. These results suggested the great advantage of supercritical fluid for fabricating ceramic replicates of templates with complex structure, such as activated carbon. We have demonstrated that activated carbon with micropores acts not only as a mold for macroscopic shape control but also as a template for nanoscale structure control, when a supercritical fluid was used as a solvent. The advantage of the supercritical fluid as a medium for replication is attributed to the inability of the supercritical fluid to produce a condensed phase.