An in-situ CVD coating of aluminum on VGCF for the fabrication of Al-VGCF composites

In-situ chemical vapor deposition (CVD) of aluminum on vapor grown carbon fibers (VGCF) was investigated for the fabrication of Al-VGCF composites. Reaction of aluminum powder with iodine was used to produce the aluminum vapor source. Aluminum powder, VGCF and iodine powder were placed into quartz tubes in various molar ratios and the quartz tubes were sealed in vacuum. Then they were annealed in the furnace. Annealing temperature was 673K or 773K. Obained powder was observed using a field emission transmission electron microscope (FETEM). Coated layer was successfully formed on VGCF using a molar ratio of VGCF : aluminum : iodine of 1 : 1 : 0.1 under an annealing temperature of 773K for 1.728 × 10 ⁵s. The coated layer was proved to be aluminum by characterization of crystal and chemical structure using X-ray diffraction, Fourier transform-infrared spectroscopy, and X-ray photoelectron spectroscopy. As a result of high resolution transmission electron microscope observation, mild reaction of VGCF with the aluminum coated layer at the interface, accompanied with formation of the interlayer (reaction layer) was evident. Detailed observation of the graphitic layers of VGCF revealed that graphitic layers on VGCF surface are slightly consumed due to reaction with aluminum. Crystal structure of the interlayer was determined to be aluminum oxycarbides (Al ₄O ₄C, Al ₂OC), by measurement of lattice spacing. It was also made clear that the interface (interlayer) formation process is strongly dominated by the surface structure of the VGCF.