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ECN publication
Minimizing the defect density of macroporous support coatings for molecular separation membranes
Published by: Publication date:
ECN Energy Efficiency in Industry 1-6-2005
ECN report number: Document type:
ECN-RX--05-120 Conference Paper
Number of pages: Full text:
11 Download PDF  

Presented at: International conference Porous Ceramic Materials (PCM2005), Bruges, Belgium, 20-21 oktober 2005.

Bubble number porometry and Hg porosimetry were used to investigate the density and size of percolating channels in gross macroporous support tubes, support tubes coated with one or two macroporous a-alumina layers and the latter coated with a thin mesoporous g-alumina layer. The key factor in obtaining macroporous thin layers with bulk properties is found in the application of multiple layers rather than the use of a single thicker layer. The breakthrough pressure of the layered macroporous substrate system increases drastically only when two coatings are applied with sufficient total thickness to shield larger voids. The bubble percolation behaviour of a mesoporous g-alumina coating is determined by the width of the Hg intrusion curve of the underlying macroporous substrate coating(s). The mean macropore diameter is sufficiently low for depositing a sol-gel layer by colloidal filtration. However the largest pores in the distribution cause percolating channels in this layer. Hence the bubble point size/ mean pore size ratio of the g-alumina coating is still >>1 and needs to be improved by applying one or more macroporous coatings where the large pore size of the distribution is smaller than 100 nm.

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