Curious structural characteristics from the carbon deposits on the graphitic electrodes subjected to arc evaporation

Abstract

We report the transmission electron microscopic investigations made on the tips of the graphite electrodes used for production of C60-buckminsterfullerene. This was achieved by triggering an electrical arc (150 A, 20V, ac) in helium (100 Torr) atmosphere between the graphite electrodes and then scraping the tip of the electrode to prepare sample for electron microscopy. The scraped material was investigated in the CM-12 Philips transmission electron microscope both in diffraction and imaging modes. An abundance of tubules were found and the diffraction patterns from them exhibited sharp diffraction spots arranged along elliptical rings. On tilting the specimen the major axis of the ellipse varied in definite was depending on the relative orientations of electron beam, tubule axis and tilt axis. A detailed geometrical exemplification has been proposed which explains the observed features in the diffraction patterns. The occurrence of possibly a new form of carbon corresponding to primitive cubic with a = 2.14 Å and nucleation of diamond on ac electrical arc treated graphite electrode are also mentioned.