Thermal studies of C60 transformed by temperature and pressure treatments Original Research Article

Samples of fullerene C60 submitted previously to temperatures and pressures up to 973 K and 9.5 GPa have been heated in a differential scanning calorimeter in the interval 220–725 K. In nearly all of them, the first heating showed an irreversible endothermic peak extending between 450 and 550 K which was interpreted as a depolymerization reaction. Subsequent heating of the resulting products often revealed the presence of a double endothermic peak between 270 and 300 K and/or the characteristic transition peak of [60]fullerene around 250 K. All these facts have been taken as the consequences of depolymerization of the initial samples. Where the endothermic peak was not observed, no [60]fullerene was produced. In one case a glass transition appeared.