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Influence of drying conditions on processing properties of ceramic spray granules

: Eckhard, S.; Fries, M.; Höhn, S.; Nebelung, M.

Tsotsas, E.:
Drying 2010. 17th International Drying Symposium, IDS 2010. Proceedings. Vol.B : Magdeburg, Germany, 3-6 October, 2010
Magdeburg: Docupoint GmbH, 2010
ISBN: 978-3-86912-036-2
International Drying Symposium (IDS) <17, 2010, Magdeburg>
Fraunhofer IKTS ()
spray drying; ceramic granules; internal structure; mechanical property; deformation

Granules from identical ceramic suspensions were spray dried at different drying conditions. A subjective inspection of the resulting granules showed comparable internal structures but different mechanical properties. Image analysis was used for analyzing specially prepared porous ceramic structures in a micro and macro structural level. It is shown that differences in mechanical properties can be explained with objective quantified structure parameters. One sample showed a higher amount of homogenous granules and a denser packed shell than the other one. Additional the generation of different internal structures was explained and correlations to the chosen drying conditions were investigated. The two produced granules showed subjectively comparable internal granule structures. In every batch hollow and homogeneous granules could be found. Analysing the amount of different structures leads to more hollow granules than homogeneous ones in both batches. The amount of homogeneous granules of sample two is 10 % higher than for sample one. The calculated average parameter relating all void area to all granule area per image gives comparable values of 0.073 for sample one and 0.075 for sample two. The calculated average shell thickness is for both granules 73 %. Micro structural differences could be measured concerning shell porosities and primary particle distances. Sample two seems to have lower average shell porosities (32.9 %) and lower average particle distances (103 nm) than sample one what leads to denser packed shells. Measured single granule strengths were higher for sample two (1.7 MPa) than for sample one (1.3 MPa) and can be explained with different internal micro structures as a result of different drying conditions.