THERMAL STUDIES OF C-60 TRANSFORMED BY TEMPERATURE AND PRESSURE TREATMENTS

Samples of fullerene C-60 submitted previously to temperatures and pre ssures up to 973 K and 9.5 GPa have been heated in a differential scan ning calorimeter in the interval 220-725 K. In nearly all of them, the first heating showed an irreversible endothermic peak extending betwe en 450 and 550 K which was interpreted as a depolymerization reaction. Subsequent heating of the resulting products often revealed the prese nce of a double endothermic peak between 270 and 300 K and/or the char acteristic transition peak of [60] fullerene around 250 K. All these f acts have been taken as the consequences of depolymerization of the in itial samples. Where the endothermic peak was not observed, no [60] fu llerene was produced. In one case a glass transition appeared. (C) 199 7 Elsevier Science Ltd.