Stability of fullerenes under hydrothermal conditions

Stability of fullerenes C-60 under hydrothermal conditions (200-800 degrees C, 100 MPa, 20 min-168 h) has been investigated. The reaction products have been characterized by Raman spectroscopy and x-ray diffraction, The fullerenes were stable up to 500 degrees C, but they decomposed immediately at 800 degrees C into amorphous carbon. In the transition region between 600 and 750 degrees C, longer times and higher temperatures of the hydrothermal treatment favored decomposition of C-60 With the formation of amorphous carbon. Addition of nickel to the C-60-H2O system neither suppressed hydrothermal decomposition of C-60 nor induced formation of other phases, except of the amorphous carbon.