Encapsulation of TiC and HFC crystallites within graphite cages by arc discharge

Fine crystallites of titanium and hafnium carbides encapsulated within graphite cages were formed by an are discharge between a metal/carbon composite anode and a graphite cathode. Soot particles grown in various places within the are reaction chamber were studied by transmission electron microscopy. Encapsulated TiC crystallites ranging from 30 to 150 nm in size were found in carbonaceous materials formed around a cathode (called "slag-like hard deposit" and "cathode soot" on it). Short, single-walled carbon nanotubes were also observed, extruding from carbon layers with complicated structures which surround TiC crystallites. For hafnium whose vapor pressure is lower than that of carbon at high temperatures, the formation of HfC crystallites (20 to 80 nm in diameter) was limited within a slag-like deposit, and they were also encapsulated in graphite cages. (C) 1997 Elsevier Science Ltd.