Carbon nanofiber reinforced aluminum matrix composite fabricated by combined process of spark plasma sintering and hot extrusion

Spark plasma sintering and hot extrusion processes have been employed for fabricating carbon nanofiber (CNF)-aluminum (Al) matrix bulk materials. The Al powder and the CNFs were mixed in a mixing medium of natural rubber. The CNFs were well dispersed onto the Al particles. After removal of the natural rubber, the Al-CNF mixture powders were highly densified. From the microstructural viewpoint, the composite materials were observed by optical, field-emission scanning electron, and high-resolution transmission electron microscopies. The CNFs were found to be located on every grain boundary and aligned with the extrusion direction of the Al-CNF bulk materials. Some Al carbides (Al ₄C ₃) were also observed at the surface of the CNFs. This carbide was created by a reaction between the Al and the disordered CNF. The CNFs and the formation of Al ₄C ₃ play an important role in the enhancement of the mechanical properties of the Al-CNF bulk material. The CNFs can also be used for engineering reinforcement of other matrix materials such as ceramics, polymers and more complex matrices.