Abdullayev, A.; Avcioglu, C.; Fey, T.; Hilger, A.; Osenberg, M.; Manke, I.; Henning, L.M.; Gurlo, A.; Bekheet, M.F.: Fabrication and characterization of porous mullite ceramics derived from fluoride-assisted Metakaolin-Al(OH)3 annealing for filtration applications. Open Ceramics 9 (2022), p. 100240/1-9
10.1016/j.oceram.2022.100240
Open Access Version
Abstract:
In this work, polycrystalline mullite whiskers are synthesized by fluoride-assisted method from metakaolin and several aluminum-containing compounds such as γ-Al(OH)3, AlF3·3H2O, and α-Al2O3 (corundum). The mullite formation and crystallization are assessed both in ex situ and in situ synchrotron X-ray diffraction experiments under synthesis conditions. Polycrystalline mullite starts to form from metakaolin, Al(OH)3, and AlF3·3H2O reactants at 680 °C, whereas mullite does not form even at 1000 °C when corundum is used. Porous mullite ceracmics are fabricated at sintering temperatures between 1000 and 1700 °C and tested for water permeance. Scanning Electron Microscopy (SEM) and synchrotron X-ray tomography (μCT) reveal that ceramics are comprised of pore channels with an interlocked network of mullite whiskers. With competitive porosity (up to 63 %), compressive strength (up to 20 MPa), and pure water flux (up to 579 L/m2·h at 1 bar), fabricated mullite ceramics are promising candidates for water filtration and purification.