Brandes, Christoph
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Brandes, Christoph
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Brandes, Christoph
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Item-typ:Veröffentlichung, Gel casting of large area micro- and sub-micropatterned thin ceramic tapes(Elsevier {BV}, 2016-01-20); ; ; ; In this study an easy-to-use ceramic processing technique based on temperature-controlled ionotropic gelation of alginate is presented. This method is the breakthrough for simultaneously large scale tape casting and high quality patterning of thin ceramic tapes. Alumina powder (d50¼ 205 nm) is used to cast flexible and on demand shapeable tapes. Compared to conventional ceramic micropatterning, ionotropic gelation combines complexity of the patterned structure over large-scale areas, a high pattern resolution down to sub-mm regime (400 nm) and tape thickness below 300 mm. Obtained green and sintered (1350 1C) micro- and sub-micropatterns are characterized by SEM and quantitative 3D-profilometry focusing on both, pattern quality and pattern aspect ratio. The results show that reproducible thin ceramic tapes featuring positive and negative patterns maintain their aspect ratios after demolding, drying and sintering. This processing route represents a versatile tool for designing tailored ceramics for e.g. microelectromechanical engineered systems, biomaterial or microfluidic applications.Wissenschaftlicher ArtikelBand:42Heft:498 90 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Aluminium acetate as alternative cross-linker for temperature controlled gel-casting and joining of ceramics(Elsevier, 2016-01-15); ; ; ; In an earlier established gel-casting process, the biopolymer alginate is cross-linked with Ca2+-ions released through the temperature controlled dissolution of calcium iodate-particles (Ca(IO3)2). In this study, aluminum acetate (AlAc) is compared to Ca(IO3)2 as an alternative temperature controlled cross-linker for an alginate–alumina slurry. Both cross-linkers are characterized regarding gel-forming properties, resulting microstructure, impurities, mechanics of sintered parts and the ability of joining ceramic blocks in the green state via connecting gelation with and without adding slurry. Rheological measurements show that both cross-linker have a similar gelling behavior and lead to gelled blocks of high quality. AlAc-particle create a denser and more homogenous microstructure, while Ca(IO3)2-particles induce pores, abnormal grain growth and lower mechanical values. Nevertheless Ca(IO3)2 shows excellent joining properties which makes it a suitable alternative to pressure joining. In summary, AlAc is an excellent alternative cross-linker but Ca(IO3)2 remains the method of choice for joining gelled bodies.Wissenschaftlicher ArtikelBand:36Heft:5124 122 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Production of ceramic membranes with different pore sizes for virus retention(Elsevier, 2014-11-12); ; ; ; Abstract Porous ceramic capillary membranes made of yttria-stabilised zirconia (YSZ) are presented, which are conditioned for virus filtration by varying the initial YSZ particle size. Compared to polymeric membranes, ceramic membranes offer remarkable advantages for filtration processes as they show excellent chemical, thermal and mechanical stability and can easily be cleaned by backflushing. YSZ powders with different particle sizes (30 nm, 40 nm and 90 nm) are individually and mixed processed by extrusion, dried and finally sintered at 1050 °C for 2 h. The sintered YSZ capillaries are characterised by microstructural analysis including Hg-porosimetry, BET analysis and 3-point bending tests. By increasing the initial YSZ particle size, increased average membrane pore sizes ranging from 24 nm to 146 nm are obtained. Mechanically stable membranes are provided showing high open porosities of ∼45% and ∼36% for capillaries composed of single and mixed YSZ powders, respectively. By increasing the membrane pore size, reduced virus retention capacities in combination with increased water permeate fluxes are achieved. Capillaries made of YSZ-40 nm ensure both, log reduction values (LRV) ≥ 4 for small model bacteriophages MS2 and PhiX174 and high water permeate fluxes (∼30 L/(m2 hbar)), being suitable for sustainable virus filtration as requested by the World Health Organisation (WHO) and the United States Environmental Protection Agency (USEPA). Due to long-term virus filtration for two weeks, membrane pore plugging is successfully avoided by iterative backflushing and relatively high membrane fluxes in combination with requested LRV 4 level fulfilling the virus filter criterion are achieved.Wissenschaftlicher Artikel109 115