Sol-gel strategies for amorphous inorganic membranes exhibiting molecular sieving characteristics
- New Mexico Univ., Albuquerque, NM (United States)
We have used several sol-gel strategies to prepare supported inorganic membranes by a process that combines the features of slip-casting and dip-coating. To be viable the deposited membranes must exhibit both high flux and high selectivity. For porous membranes these requirements are met by extremely thin, defect-free porous films exhibiting a narrow size distribution of very small pores. This paper considers the use of polymeric silica and hybrid-organosilyl precursor sols in the context of the underlying physics and chemistry of the membrane deposition process. Since the average membrane pore size is ultimately established by the collapse of the gel network upon drying, it is necessary to promote polymer interpenetration and collapse during membrane deposition in order to achieve the very small pore sizes necessary for molecular sieving. For polymeric sols, this is accomplished using rather weakly branched polymers characterized by fractal dimension D < 1.5 under deposition conditions in which the silica condensation rate is minimized. By analogy to organic polymer sols and gels, we believe that the breadth of the pore size distribution can be influenced by the occurrence of micro-phase separation during membrane deposition. Minimization of the condensation rate not only fosters polymer collapse but should inhibit phase separation, leading to a narrower pore size distribution. The formation of microporosity through collapse of the gel network requires that small pores are achieved at the expense of membrane porosity. Incorporation of organic template ligands within a dense silica matrix followed by their removal allows us to independently control pore size and pore volume through the size and volume fraction of the organic template. Such strategies can be used to create microporous films with large volume fraction porosities.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States); Electric Power Research Inst., Palo Alto, CA (United States); Gas Research Inst., Chicago, IL (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 102326
- Report Number(s):
- SAND-95-1354C; CONF-940713-3; ON: DE95014884
- Resource Relation:
- Conference: 3. international conference on inorganic membranes, Worcester, MA (United States), 10-14 Jul 1994; Other Information: PBD: [1994]
- Country of Publication:
- United States
- Language:
- English
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