GROWTH OF BUCKYTUBES ON THE ANODE AT ARC-DISCHARGE

It is shown that for an are discharge between carbon electrodes in an inert gas atmosphere the temperatures at the electrode surfaces play a key role in determining the structure and the electrode on which a de posit can grow. The heat balance equations determine that the anode te mperature is higher due to the energy carried by the electrons. This l eads to anode sublimation and deposition on the cathode. It is shown t hat by cathode heating, by anode cooling or by a combination of these, a deposit may be obtained on the anode due to cathode erosion. The de posit grown by the ''inverse'' method is compared with a deposit obtai ned on the cathode under the same conditions but at reverse supply vol tage polarity. The material from both deposits, studied by TEM, shows that there are graphite crystals within the anode deposit, and that th e carbon forms within have a relatively small number of structural def ects while the buckytubes are greater in length than those within the cathode deposit. The reasons for these differences are discussed. In t he ''inverse'' method, the constant decrease in cooling of the anode s urface leads to an equalization of the anode and cathode temperatures. This creates conditions that favor buckytube growth.