Surface microstructure
To observe the dispersion of CNFs microscopically for more information concerning the interfacial interaction between the CNFs and rice straw fibers, the surfaces of films were further investigated by SEM. The micrograph of pure rice straw film (without CNFs) shows relatively rough surface and a certain degree of phase separation (Fig. 2a). However, the specimen films filled with 10 wt% CNFs exhibits relatively smooth and homogeneous surface without any phase separation (Fig. 2b). Apparently, it is observed in Fig. 2b that CNFs were uniformly dispersed and embedded into the rice straw fiber network. As mentioned earlier, the preparation process of the sheets was carried out by a papermaking-like process. The process delivered very low loss especially considering that the ultrafiltration mesh alone would be able to hold the nano-sized CNFs. The micro-sized rice straw fibers seem to act as an additional sieve for the CNFs, which have been trapped by sticking to the surface of the rice straw fibers during the sheet forming.