Optical transmittance and electrical conductivity of silica glass with biserial and hierarchical network structures made of carbon nanofibers

Abstract

Silica glass composites, with biserial and hierarchical percolative network made of carbon nanofibers (CNFs), was fabricated using a layer-by-layer technique and spark plasma sintering to obtain high optical transmittance and electrical conductivity. Owing to the network, the critical volume fraction, Vc, for the CNF percolation in the silica glass-matrix composite (0.5–0.7 vol%), when the electrical conductivity of the composite drastically increased with change from insulator (∼10−10 S/m) to conductor (∼10−1 S/m), is smaller than theoretical Vc predicted for the three-dimensional random orientation of CNFs (2.6 vol% for the CNF aspect ratio of 30). The conductivity of the composite with above the Vc of CNFs (∼10 S/m) is higher than that reported for the polymer-matrix composite (∼10−5–∼10−3 S/m). Furthermore, high optical transmittance was observed for the electrically conductive composite with Vc of CNFs.