The effects of pre-treatment and catalyst composition on growth of carbon nanofibers at low temperature

Carbon nanofiber films have been grown on Fe-Ni alloy catalysts at 400°C by a thermal chemical vapor deposition (CVD) method using acetylene as a carbon source. Fe-Ni-C alloy catalysts were found to be more suitable for carbon nanofiber growth at 400°C than pure Ni or Fe-Ni catalysts. When Fe-Ni catalysts were pre-treated in hydrogen at a low temperature (400°C), the catalyst lost its activity in growing carbon nanofibers at 400°C by forming an amorphous carbon layer covering catalytic sites on the surface. The growth rate of carbon nanofibers was improved significantly by pre-treating the catalyst with a low concentration of carbon source (e.g. acetylene, carbon monoxide) forming Fe-Ni-C alloy during the temperature-rising step before growth. Carbon nanofiber walls consisted of imperfect graphite structure as characterized by transmission electron microscopy.