Ordered 3D Hexagonal Mesoporous Silica Membranes: Synthesis and Characterization
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AA8.6.1
Ordered 3D Hexagonal Mesoporous Silica Membranes : Synthesis and Characterization Michaela Klotz1, Sophie Besson1, Christian Ricolleau2, Florence Bosc3, André Ayral3 1)
Laboratoire CNRS / Saint-Gobain «Surface du Verre et Interface» UMR 125 ;39 Quai Lucien Lefranc ; F- 93303 Aubervilliers cedex, France 2) Laboratoire de Minéralogie, Cristallographie, UMR 7590 ; Université Paris VI et Paris VII, 4 place Jussieu, F-75252 Paris cedex 05, France 3) Institut Européen des Membranes, UMR 5635 ; CC047, Université Montpellier II, F-34095 Montpellier cedex 5, France
Abstract A ceramic membrane with an ordered mesoporous top layer has been developed. The active layer possesses a close-packed hexagonal network of spherical pores. Results on permeation of helium and argon through the membrane are presented and correlated with the structural and textural properties of the top layer. New insights are given on the porosity of this close-packed hexagonal structure.
1.
Introduction
Ceramic membranes are studied for their thermal and chemical stability and chemical resistance. Membranes with small mesopores are promising for the separation of rather bulky molecules or for gas treatment. This kind of membranes are generally obtained by the sol-gel process but exhibit rather large pore size distributions which decrease their selectivity. Since the discovery of ordered mesoporous materials [1], work has been done to develop silica membranes with uniform pore sizes using templating mesophases [2-7]. In a previous work [8], we prepared structured silica membranes consisting of a hexagonal packing of cylindrical pores. In the case of these columnar structures, the orientation of the pores is usually parallel to the substrate which is unfavorable for membrane applications. The introduction of colloidal particles [7] enabled us to study the influence of pore orientation on the permeability. The cylindrical pores of this system are not interconnected and the gas permeation is limited by the microporosity of the silica walls. In the present work, we investigate a different pore network consisting of spherical pores arranged in a hexagonal close-packed structure [9]. It is however not yet clear if these spherical pores are interconnected or isolated. Moreover, if the pores are interconnected, the pore diameter which will actually be involved in a filtration process is the neck between two adjacent pores. It is thus important to accurately characterize the porosity of this structure by static and dynamic methods.
AA8.6.2
2.
Experimental Section
Sample preparation The coating solution was prepared using tetraethoxysilane (TEOS) as precursor of the silica network. In a first step, TEOS (>98% purity), acidic water (pH 1.25, adjusted with HCl) and ethanol (99.8% purity) were refluxed at 60°C for 1h. A cationic surfactant, cetyltrimethyl ammonium bromide (CTAB, >98% purity), was diluted in ethanol and then added to the mixture. Final composition was: 1 TEOS : 5 H2O : 10 Ethanol : 0.1 CTAB. The mesoporous silica layer was deposited b
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