Carbon nanotube-SiO2 composites by colloidal processing

The surfactants assisted colloidal processing of 1.0 wt-% carbon nanotube ( CNT)-SiO2 composites using acid treated CNTs and colloidal silica has been investigated. By using different combinations of anionic and cationic surfactants five systems were developed with the aim of coating the CNTs with silica particles and creating a homogenously dispersed composite. Sintering of CNT-SiO2 composites was performed for 3 h at 1300 degrees C in argon atmosphere. Pressureless sintering yielded composites with a density > 95% of the theoretical. X-ray diffraction analysis showed the presence of cristobalite, but no other crystalline phases were detected in the sintered composites. Microstructural observation revealed isolated CNTs in the SiO2 matrix both in the as dried powder and in the sintered samples. It is concluded that the simple colloidal process developed here can be a convenient alternative to the sol-gel based methods used for fabrication of inorganic matrix composites containing CNTs.