An investigation of the relationship between position within coater and pyrolytic carbon characteristics using nanoindentation

Pyrolytic carbon samples were formed at several locations within a fluidized bed reactor by depositing onto stationary graphite rods, which were suspended parallel to the coater's axis. The samples were examined metallographically and using nanoindentation. The sample densities and mass deposition rare as a function of position were also determined. Homogeneous material was formed primarily at positions along the coater's central axis and near the reactor's gas inlet. Porous coatings were formed far from the central axis or far from the gas inlet. Nanoindentation measurements indicated the homogeneous material had a higher elastic modulus and hardness and greater elastic recovery, as compared to the porous material. Both materials were seen to be: isotropic. The homogeneous coatings were seen to be the densest and the mass deposition rate was seen to increase with increasing distance from the gas inlet. It has been proposed that these observations can be explained in light of the spatial distribution of the time averaged fluidized bed particle kinetic energy and number density. (C) 2000 Elsevier Science Ltd. All rights reserved.