1999

Joutsensaari, Jorma

Aerosol synthesis methods for production of nanostructured fullerene particles have been developed. The nanostructured, ultrafine fullerene particles were produced in continuous flow reactor systems. The study demonstrated that ultrafine (30-60 nm) fullerene particles can be generated by vapor condensation. The particles are spherical, solid and polycrystalline at processing temperatures of 500 °C and above. The larger fullerene particles with sizes around 100 nm were produced via an aerosol droplet drying and crystallization method. The particles are mainly nanocrystalline at processing temperatures of 20-200 °C and polycrystalline at 300-400 °C. At 500-600 °C the fullerene particles are mainly single crystals and sometimes clearly faceted. The most common shapes among perfectly faceted particles were hexagonal plate-like, decahedral and icosahedral. The plate-like particles are lamellar twinned and the decahedral and icosahedral particles are multiply twinned. The lamellar-twinned particles probably grow rapidly on the side-faces in the direction parallel to the twins by a re-entrant corner growth mechanism. No uniform mechanism was found for the formation of multiply-twinned particles. They probably grow layer-by-layer around the exiting decahedral and icosahedral nuclei or are formed during grain growth from polycrystalline particles. The growth of particles with well-defined crystal habits is often promoted by defects, such as twins and stacking faults. The vaporization of fullerene particles in the heated zone of the reactor plays an important role during the formation and growth of particles with a clearly faceted shape. The study shows that fullerene particles with controlled size and crystallinity can be produced by aerosol synthesis methods.