2014 Volume 55 Issue 5 Pages 827-830
Although carbon nanofibers show high thermal conductivities and excellent mechanical properties, their composites do not show superior properties because the short nanofibers are discontinuous. Casting vapor-grown-carbon-fiber-reinforced pure-aluminum-matrix (VGCF/Al) composites requires a continuous VGCF preform carbon lattice and bridging between the VGCFs. We investigated how heating affected mesophase pitch (MP) crystallization and how the VGCFs affected the MP-bridging between the VGCFs used to fabricated VGCF preform. The as-received MP and MP heated at 793 K were prepared, and the crystallinities of the two MPs were compared. The (002)-plane lattice spacing of the MP heated at 793 K was remarkably decreased. The heated-MP showed higher crystallinity than the as-received MP, indicating that the heating affected the crystallinity of the MP. The preform was prepared by heating a 1 : 9 mixture of VGCFs and MP particles at 793 K for 1 h under vacuum below 40 Pa, and the crystallinities were compared with the heated MP. The preform (002) plane showed narrow lattice spacing comparable to that of heated MP, the preform showed higher crystallinity than the heated MP, indicating that the VGCFs affected the crystallinity of the MP. The MP enclosed rather than bridged the VGCFs. Moreover, the VGCFs were randomly oriented throughout the MP. The microstructures of the VGCF consisted of linear and wavy carbon structures. The fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) analyses indicated that the wavy structure showed dislocation.
