Particle coating by chemical vapor deposition in the fluidized bed

Vom Promotionsausschuss der Technischen Universität Hamburg-Harburg zur Erlangung des akademischen Grades Doktor-Ingenieur genehmigte Dissertation: „Aluminum coatings were created on glass beads by chemical vapor deposition in a ? uidized bed reactor. Two di? erent routes of precursor injection were examined, one being the introduction of gaseous precursor by a saturated carrier gas stream, the other being liquid spray injection. Tri-isobutyl-aluminum (TIBA) was thermally decomposed inside the ? uidized bed to deposit elemental aluminum. Di? erent glass beads were used as ? uidized bed materials and as substrates for the deposition reaction. To ensure homogeneous coating of the bed material, the ? uidizing conditions necessary to avoid agglomeration were investigated for a broad range of temperatures. The deposition reaction was modelled numerically on the basis of a discrete particle simulation to gain insight into the mechanisms of the coating process. Based on this modelling, statements about the homogeneity and thickness of the coating throughout the bed material could be made. In particular, the take-up of aluminum was traced for selected particles on their way throughout the reactor volume with time. This simulation was used to predict zones of potential agglomeration due to high precursor concentrations and insu? cient solids mixing rate.“