MAGNETIC PROPERTIES OF CARBON NANOTUBES ENCAPSULATING NANOSIZED NICKEL PARTICLES

Multi walled carbon nanotubes were synthesized by the catalytic chemical vapor decomposition method, and a binary aerogel with a 1.20∶1 nickel silica weight ratio was used as catalyst, which was prepared by the sol gel supercritical fluid drying method. The synthesis of carbon nanotubes was conducted in a quartz tube furnace. The catalysts in the quartz boat were heat treated to the required temperature under nitrogen atmosphere and reduced by flowing hydrogen for 30?min. Then the gas mixture of hydrogen and methane was introduced into the furnace and pyrolyzed for 30?min～60?min. Finally, the product obtained was cooled to room temperature under a nitrogen atmosphere. The samples were characterized by XRD, SEM, TEM, HRTEM, Raman spectra and susceptibility tests. The results showed that the pyrolytic product was composed of multi walled carbon nanotubes and nanosized nickel particles, which were encapsulated at the tip of the carbon nanotubes. Magnetic analysis showed that the carbon nanotubes encapsulating nickel had a specific saturation magnetization of 0.66?A·m 2·kg -1 and a coercivity of 20?157?A·m -1 .