Multi-scale alignment construction for strong and conductive carbon nanotube/carbon composites

Carbon nanotube/carbon (CNT/C) composites derived from entangled CNT network and different precursors, phenolic or pitch, were fabricated in this work. Multi-step mechanical stretching, repeated polymer infiltration pyrolysis and graphitization were subsequently performed for the preparation. CNT alignment was accomplished in CNT/C derived from both phenolic and pitch precursors, while aligned carbon matrix could be only found in CNT/pitch derived CNT/C composites. Such phenomenon provided direct evidence for the promoting effect of CNT alignment on the graphitization of the carbon matrix. Mechanisms for the stretching induced alignment and the formation of aligned carbon matrix were proposed and discussed. The planar configuration of pitch molecules and its Pi–Pi stacking with CNT walls were considered beneficial for the stress induced graphitization, thus the carbon matrix could be aligned along the CNT walls. Based on the tensile and electrical conductivity measurements, we believed that CNT alignment dominated both mechanical and conducting performances of cured (stabilized) and carbonized CNT/C composites; while the alignment of carbon matrix played the decisive role in graphitized CNT/C. In addition, the carbonized composites could exhibit tensile strength as high as 1.2 GPa, while the electrical conductivity of graphitized samples was in the scale of 105 S/m.