C₆₀ Fullerene Polymers

Abstract

TEM investigations were performed on high temperature and pressure C₆₀ fullerene. A mixed phase of alternating rhombohedral lamellae and tetragonal domains is formed. At higher temperatures 900–1173 K graphitic ‘hard’ carbon phases formed, via an inter-polymer interface instability and/or shear mechanism. This phase exhibited a hardness of 10–15 GPa and a high degree of elastic recovery under indentation. The kinetics of graphitisation were slow and proceeded via cross-linked intermediates, which influenced the hardness markedly, up to 33.5 GPa. In-situ investigations into the P/T field of C₆₀ were performed using energy dispersive X-Ray diffraction techniques. The P/T history and pressure isotropy were investigated to confirm and optimise conditions for 3-D polymer formation. Formation of 3-D polymers has been carried out in-situ, however the reclaimed sample failed to live up to hardness expectations, due to depolymerisation problems on pressure release. Isotropy in the pressure field promoted formation and retention of the 3-D FCC structure. The existence of a series of ferromagnetic rhombohedral C₆₀ polymers has been realised. This property has been shown to occur over a range of preparation temperatures at 9 GPa. The structure is shown to be crystalline in nature containing whole undamaged Buckyballs. Formation of radicals is most likely due to thermally activated shearing of the bridging bond resulting in dangling bond formation.