Synthesis and characterization of in situ grown carbon nanofiber/nano-tube reinforced carbon/carbon composites

摘要

Carbon nanotubes (CNTs) have aroused great interest as a reinforcement in composites research in the last decade because of their ultra-high mechanical properties and excellent thermal conductivity combined with their rather low density 1, Nevertheless, there are many difficulties when converting the nanoscale powder into a macroscale engineering material, such as weak interfacial bonding, inhomogeneous dispersion and low upper limit of the quantity of added CNTs. As a result, in most cases, only a moderate increase in mechanical properties for CNT reinforced composites is achieved 2,3. In addition, the production of CNTs in the range of kilograms per day with uniform diameter and perfect microstructure cannot currently be realized by a chemical vapor deposition (CVD) process. Carbon nanofibers (CNFs), though not as perfect in structure or as good in properties, would be a good alternative to CNTs as an additive in composites 4, because the industrial production of the large quantity of CNFs required in the plastics and composite industry is definitely more feasible 5,6. Most research on the direct use of CNTs/CNFs alone for composite reinforcement would be less valuable when compared to corresponding composites with low-cost soot products or carbon fibers as additives. Because CNTs/CNFs cannot form a connected integrated network as a preform, as can carbon fibers, and the lack of strong bonding between dispersed individual CNTs or CNFs, the potential properties of CNTs cannot be realized in most cases. Therefore in situ catalytic grown CNFs/CNTs have been explored as a second reinforcement in traditional carbon fiber reinforced carbon matrix (C/C) composites. CNFs/CNTs can function as a bridge between the micron-scaled carbon fibers and the carbon matrix and may also affect the microstructure of the deposited matrix carbon. The properties of this composite will be considered in a later paper.