Finger-like voids induced by viscous fingering during phase inversion of alumina/PES/NMP suspensions
KAUST DepartmentAdvanced Membranes and Porous Materials Research Center
Biological and Environmental Sciences and Engineering (BESE) Division
Physical Sciences and Engineering (PSE) Division
Chemical and Biological Engineering Program
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AbstractThe formation mechanism of phase-inversion ceramic hollow fibre membranes has not been well understood. In this paper, we report on the formation of finger-like macrovoids during non-solvent-induced phase inversion of alumina/PES/NMP suspensions. A membrane structure without such finger-like macrovoids was observed when the suspension was slowly immersed into pure ethanol or a mixture of 70. wt% NMP and 30. wt% water, whereas finger-like macrovoids occurred when the suspension was slid into the non-solvents at higher speeds. We found that the formation process of finger-like macrovoids could be fully or partially reversed when nascent membranes were taken out from water shortly after immersion, depending on the duration of the immersion. Splitting of the fingers during the formation of the macrovoids was also observed during the phase inversion of two alumina/PES/NMP suspensions. These experimental observations were not predicted by current theories of finger-like macrovoid formation in polymer membranes, but appear to mimic the well-known viscous fingering phenomenon. We therefore propose that in the phase inversion of ceramic suspensions, the viscous fingering phenomenon is an important mechanism in the formation of finger-like voids. © 2012 Elsevier B.V.
SponsorsThis work was supported by baselines funds to Z.P. Lai from King Abdullah University of Science and Technology. B. Wang acknowledges support from the Ministry of Education of China (Contract No. 210093). We thank Dr. S.H. Choi for stimulating discussions and Dr. P. Wang for providing access to the microscope.
JournalJournal of Membrane Science