Local microstructural organization in carbogenic molecular sieves
- Univ. of Delaware, Newark, DE (United States)
The microstructure of nanoporous, carbogenic molecular sieves (CMS) was studied using high resolution electron microscopy and neutron diffraction. The narrow range of pore sizes observed in these complex materials suggests that although these materials are globally amorphous, the local microstructural features are more organized. This work, focused on poly(furfuryl alcohol)-derived CMS, is aimed at characterizing the evolution of this microstructure. Microscopy results show that materials synthesized at low temperature have some degree of organization but that the microstructure is featureless and symmetric at longer length scales. This symmetry is broken at higher synthesis temperatures as thermodynamic driving forces lead to further organization of the carbon atoms into more ordered structures but the length scales remain short. Micrographs of high temperature CMS show a high degree of curvature and features reminiscent of fullerene. The connectivity of the carbon atoms in the CMS has been probed using powder neutron diffraction. This data suggests that the atoms in the CMS form ordered structures on the length scale of 15{angstrom} which are distinctly different from the structure of graphite. These observed changes in the microstructure directly impact the adsorptive and molecular sieving characteristics of the CMS as illustrated by the marked differences between the diffusivities of oxygen and nitrogen. This property is crucial for the very demanding separation of nitrogen from oxygen in air.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- DOE Contract Number:
- W-31109-ENG-38; AC05-84OR21400
- OSTI ID:
- 462717
- Report Number(s):
- CONF-960401-; ISBN 1-55899-334-7; TRN: IM9719%%187
- Resource Relation:
- Conference: Spring meeting of the Materials Research Society (MRS), San Francisco, CA (United States), 8-12 Apr 1996; Other Information: PBD: 1996; Related Information: Is Part Of Microporous and macroporous materials; Lobo, R.F. [ed.] [Univ. of Delaware, Newark, DE (United States)]; Beck, J.S. [ed.] [Mobil Technology Co., Paulsboro, NJ (United States)]; Suib, S.L. [ed.] [Univ. of Connecticut, Storrs, CT (United States)]; Corbin, D.R. [ed.] [E.I. Dupont de Nemours and Co., Wilmington, DE (United States)]; Davis, M.E. [ed.] [California Inst. of Tech., Pasadena, CA (United States)]; Iton, L.E. [ed.] [Argonne National Lab., IL (United States)]; Zones, S.I. [ed.] [Chevron Research and Technology Co., Richmond, CA (United States)]; PB: 566 p.; Materials Research Society symposium proceedings, Volume 431
- Country of Publication:
- United States
- Language:
- English
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