Efficient Separation of Giant Graphite Balls from As-Grown Single-Wall Carbon Nanohorns

概要

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We show in this report an easy and efficient method of purifying single-wall carbon nanohorns (SWNHs). The major impurities of SWNHs are micrometer-order graphite-based particles, named giant graphite (GG) balls, the content of which is within 5–15 wt %. GG balls cannot be removed by combustion because they are burned at higher temperature than SWNHs. However, we found that gravitational sedimentation is very effective for the removal of GG balls: As-grown SWNHs were dispersed in ethanol using a bath-type ultrasonicator, and then the dispersion was left to stand for 17 h. GG balls settled down, while SWNHs dispersed in the supernatant. The purity of the SWNHs in the supernatant was almost 100%, as estimated by thermogravimetric analysis. This separation was understandable because Brownian motion more predominantly affects the motion of SWNH aggregates with a smaller size and a lower density, while gravitational sedimentation predominantly affects the movement of GG balls with a higher density and larger size. Since gravitational sedimentation is simple and convenient, it can be easily applied to the large-scale purification of SWNHs.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2009-01-25