Porous alumina ceramics prepared with wheat flour |
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| Authors: | Eva Gregorová Willi Pabst Zuzana Živcová Ivona Sedlářová Svatava Holíková |
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| Affiliation: | 1. Institute of Chemical Technology, Prague (ICT Prague), Department of Glass and Ceramics, Technická 5, 166 28 Prague 6, Czech Republic;2. Institute of Chemical Technology, Prague (ICT Prague), Department of Inorganic Technology, Technická 5, 166 28 Prague 6, Czech Republic;1. School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, PR China;2. State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China;3. Department of Materials Science and Engineering, Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, FL 32816, USA;1. The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China;2. Luoyang Cen-Lon Ceramics Co. Ltd., Luoyang 471003, China;3. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK;1. Centre Technique du Papier, BP 251, 38044 Grenoble Cedex 9, France;2. Laboratoire de Génie Chimique (LGC), CNRS-Université de Toulouse (INPT), BP 84234, 31432 Toulouse, France;1. School of Metallurgy, Northeastern University, Shenyang 110819, PR China;2. Electron Microscope Unit, Mark Wainwright Analytical Centre, The University of New South Wales, Sydney, NSW 2032, Australia;1. School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, PR China;2. School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, PR China;3. Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32816, USA |
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| Abstract: | It is shown that wheat flour can be used as a pore-forming and body-forming agent in ceramic technology. In contrast to pure native starch, however, the pores do not result from the swelling starch granules alone but are mainly due to protein-assisted foaming. Therefore the porosity is significantly higher and the pore size larger than that resulting from the starch granules alone, and the wet milling time applied for homogenizing the ceramic suspensions becomes the most critical process parameter. Alumina suspensions with 70 wt.% alumina and 20–30 vol.% wheat flour with different initial particle size (fine grade and semolina, respectively) have been prepared using milling times of up to 8 h. Porosities of up to approx. 60% can be achieved with only 20 vol.% of flour or semolina after 8 h of milling time, with the cell sizes (diameters of pore cavities resulting from foam bubbles) being essentially independent of the milling time (median diameters of 120–240 μm). Effective pore throat sizes (i.e. diameters of cell windows or channels between cells), measured via mercury porosimetry, are 1–2 μm for short milling times (2–3 h), but for long milling times (8 h) they change by more than one order of magnitude to median sizes of 20–30 μm, closely corresponding to the median size of wheat starch granules (approx. 20 μm). |
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