Dip-coating of fibrous natural materials for alumina tube manufacturing

Results from preliminary studies for development of hollow ceramic tubes by dip-coating of fibrous plants with water based gel-casting slurries are presented. Hemp and coconut fibres have been tested as templates reflecting in different macro and micro structures of the obtained ceramic tubes. Good correlation between the diameters of the template fibres and the developed channels has been documented, the ordering of the channels inside the tubes being function of the mode of fibres implementation: as singles or as bundles. By coating hemp fibres in bundle, multi channel pattern has been developed, resulting from splitting of the bundle. By using single coconut fibre as template, uniform mono channels with 250 – 400 µm in diameter were observed. The developed tubes have been characterized by good end finish. The observed differences in their microstructure offer possibilities for adjusting the physical properties towards prospective application niches.