Unidirectional solution-based freeze cast polymer-derived ceramics: influence of freezing conditions and templating solvent on capillary transport in isothermal wicking
|D. Schumacher, P.H. da Rosa Braun, M. Wilhelm, K. Rezwan, Unidirectional solution-based freeze cast polymer-derived ceramics_influence_2019_accepted_version_Deckblatt_pdfa1.pdf||2.16 MB||Adobe PDF||View/Open|
da Rosa Braun, Pedro Henrique
Porous SiOC monoliths were prepared by solution-based freeze casting of polysiloxane at constant freezing temperature or constant freezing front velocity. Dendritic and prismatic pore structures were obtained by using cyclohexane and tert-butyl alcohol as solvent, respectively. Gradients in freezing velocity lead to gradients in pore window size, whereas a constant freezing velocity (3.3–6.8 µm/s) generates homogeneous pore structures. The water permeability varies from 1.12 × 10−13 to 1.03 × 10−11 m2 and correlates with the pore window diameter (10–59 µm) and the porosity (51–82%). In wicking tests, the gradient in pore window size is clearly reflected by a pronounced decrease in the wicking speed. Contrary, a homogeneous pore structure results in wicking curves which are closer to the prediction according to the Lucas–Washburn equation. However, this theoretical approach based on the three parameters, pore window size, porosity and permeability, is insufficient to describe complex three-dimensional pore structures. Besides the porosity, the pore morphology was found to be a major influencing factor on the wicking. The filling of secondary dendrites slows down the wicking into the dendritic structure. Fastest wicking was observed for a prismatic pore structure at low freezing front velocity (6.6 µm/s) and high porosity (78%), whereas slowest wicking occurred into the dendritic structure with high porosity (76%) and constant freezing temperature (− 20 °C). The knowledge of the relationship between structural properties and the resulting wicking behavior can address a variety of pivotal applications in chemical engineering for capillary transport.
|Keywords:||Mimenima||Issue Date:||23-Dec-2019||Publisher:||Springer||Project:||MIMENIMA GRK 1860||Funders:||Deutsche Forschungsgemeinschaft||Grant number:||601090||Journal/Edited collection:||Journal of Materials Science||Start page:||4157||End page:||4169||Band:||55||Type:||Artikel/Aufsatz||ISSN:||0022-2461||Secondary publication:||yes||Document version:||Postprint||DOI:||10.26092/elib/2481||URN:||urn:nbn:de:gbv:46-elib71603||Institution:||Universität Bremen||Faculty:||Zentrale Wissenschaftliche Einrichtungen und Kooperationen||Institute:||MAPEX Center for Materials and Processes|
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checked on Dec 9, 2023
checked on Dec 9, 2023
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