Effects of polycarbosilane addition on the mechanical properties of single-walled carbon nanotube solids

Single-walled carbon nanotubes (SWCNTs) are often produced in a form of bundles during their synthesis process. However, the bundles could slide easily on each other as they are held together by a weak van der Waals interaction. This weak cohesion is one of the major obstacles in the preparation of strong macroscopic solid structures composed of SWCNTs. Here, we have attempted to improve the stability of the links between SWCNTs within and between the bundles by introducing polycarbosilane (PCS) (10 mass%) to purified SWCNTs. Then, the SWCNT-PCS composite was prepared by the hot-pressing the SWCNT-PCS mixture at temperatures between 1000 and 1800°C under a pressure of 120 MPa. The effect of processing temperatures on the mechanical properties of the composites was examined by conducting three-point bending tests. For comparison, SWCNT solids were also prepared without addition of PCS. In the case of the SWCNT-PCS composite prepared at 1000°C, the specific strength and specific modulus were about two and four times higher than that of the binder-free SWCNT solid, respectively. The reason for the increment is believed due to the stable PCS links formed between SWCNTs within and between the bundles.