| 1. |
- Aiello, R., et al.
(författare)
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Zeolite synthesis in microgravity
- 2005
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Ingår i: Topical teams in life & physical sciences. - Noordwijk, Netherlands : ESTEC. - 929092974X ; , s. 78-85
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The results of activities performed by the members of the Topical Team on 'Zeolites synthesis in microgravity' are discussed. A method was developed using a two-temperature synthesis procedure to distinguish between the nucleation and growth phase of the crystallization. The experiments have investigated the possibility of suppressing secondary nucleation by imposing a temperature gradient. Optical thickness of the solution has been monitored by interferometry. The Team, on the basis of findings, has elaborated a research program on zeolite film deposition that includes microgravity experimentation.
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| 2. |
- Andersson, Charlotte, et al.
(författare)
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Silicalite-1 membranes with small crystal size
- 2004
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Ingår i: Recent advances in the science and technology of zeolites and related materials. Part A. - Amsterdam : Elsevier. - 0444518274 ; , s. 626-631
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Konferensbidrag (refereegranskat)abstract
- Silicalite-1 membranes with small crystal size were prepared using a multiseeding method, where the support was repeatedly seeded and exposed to a short hydrothermal treatment up to five times. The film were characterized using SEM, single gas permeation, porosimetry and mixture separation experiment Films with three or four layers were of high quality i.e with minor defects according to the porosimetry experiments but showed poor separation of binary mixtures. This result may be attributed to the small crystal size and/or large amount of grain boundaries in the films.
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| 3. |
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| 4. |
- Bjorklund, Robert B., et al.
(författare)
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Vapor adsorption in thin silicalite-1 films studied by spectroscopic ellipsometry
- 1998
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 102:12, s. 2245-2250
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of silicalite-1 grown on silicon substrates were studied by spectroscopic ellipsometry. Analysis of spectra using an optical model consisting of a single porous layer on silicon yielded average film thicknesses of 84 and 223 nm for films synthesized for 10 and 30 h. Void fraction for the films was 0.32-0.33. Vapor adsorption from a nitrogen carrier gas at room temperature was monitored by ellipsometry. Isotherms for different adsorbates were obtained by analysis of spectra taken at different vapor concentrations using an optical model where the void volume was filled with both nitrogen and condensed vapors. Quantification of the condensed vapor amount was based on the changes in refractive index when adsorbates replaced nitrogen in the pores. Adsorbate volumes for water, toluene, 1-propanol, and hexane were 0.12, 0.12, 0.15, and 0.17 cm3 liquid g-1 film, respectively.
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| 5. |
- Dyhr, Kurt, et al.
(författare)
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Effects of zeolite addition on the manganese catalyzed decomposition of hydrogen peroxide
- 1999
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Ingår i: Journal of porous materials. - 1380-2224 .- 1573-4854. ; 6:4, s. 275-282
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Tidskriftsartikel (refereegranskat)abstract
- Manganese catalyzed decomposition of hydrogen peroxide in the presence of various zeolites was investigated at different pH values, Mn concentrations and zeolite: Mn ratios. Depending upon the level of these parameters the zeolites studied displayed both catalytic and inhibitive effects on the rate of decomposition. At a high pH (10.8) Mordenite 10A in a twofold excess on an ion-exchange capacity basis acted as an inhibitor whereas the other zeolites had little or no effect on the reaction rate. At a lower pH (9.0) zeolite A when added in large excess resulted in a remarkable inhibitive effect whereas the same zeolite resulted in a promotion of the catalytic action of manganese at an intermediate pH (9.9). The complex catalytic nature of zeolite-peroxide-Mn systems is discussed.
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| 6. |
- Dyhr, Kurt, et al.
(författare)
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Use of zeolites in hydrogen peroxide bleaching of pulp
- 1998
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 13:4, s. 257-262
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Tidskriftsartikel (refereegranskat)abstract
- The use of zeolites for inhibition of transition metal catalyzed decomposition of hydrogen peroxide was evaluated. A number of zeolite types (A, P, Y, and mordenite 10A), with different crystal structures and ion-exchange characteristics, were tested as additives in bleaching experiments using a mechanical (TMP) pulp and a chemical (kraft) pulp. For the mechanical pulp, addition of zeolites A and P at a moderate alkali charge resulted in a significant improvement of the bleaching performance as signified by an increase in both brightness and residual peroxide content of the bleaching liquor. The other zeolite types studied did not give any positive effects at the bleaching conditions used. For the chemical pulp, no significant improvements were obtained at any alkali charge using zeolite A as an additive. At high alkali charges, addition of zeolite A resulted in a substantially lower brightness than that reached in a zeolite free reference experiment. The effects of zeolite addition upon the bleaching of pulp are complex and dependent upon a number of factors. Parameters of great importance are the bleaching pH, consistency and the zeolite type and charge
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| 7. |
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| 8. |
- Edin, M., et al.
(författare)
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Hot melt adhesion of liner sized with alkylketene dimer
- 2002
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 17:4, s. 395-400
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the sizing agent alkylketene dimer (AKD) on hot melt adhesive joint strength was studied. By varying the amount of AKD added, and varying the degrees of beating and calendering, sheets with different surface energies, surface structures, and strength properties, were obtained. The sheets were adhesively bonded using a commercial packaging machine, and the adhesive joints were tested in T-peel and creep tests. Contact angles, water absorptivity, delamination strength, density, and surface roughness were measured to study the way in which the addition of AKD, beating, and calendering influence these paper properties. The results indicate that neither sizing with AKD nor calendering or beating have any pronounced effect on the adhesive joint strength, at least not under the conditions used. Most of the differences observed are within the limits of the experimental error. The greatest influence on the joint strength was observed when samples had been stored at low temperature.
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| 9. |
- Elvin, F.J., et al.
(författare)
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Processes for demetalization of fluid cracking catalysts
- 1988
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Ingår i: Fluid catalytic cracking. - Washington, DC : American Chemical Society (ACS). - 0841215340 ; , s. 229-236
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Konferensbidrag (refereegranskat)abstract
- Three processes, Demet III, Demet X and New Demet, for demetallization of metal poisoned octacat fluid cracking catalysts were investigated. These processes removed a significant part of the V (30-40%) from the catalyst. The New Demet and Demet III were very effective in removing Ni (88% and 80%, respectively) while practically no Ni could be removed by Demet X. The Demet procedures also proved effective in removing other contaminants like Fe and Cu. All Demet methods resulted in increased cracking activities as determined by the micro-activity test. The conversions increased from 65% for the untreated catalyst to 76-78% for samples treated according to the different Demet procedures. The increase in activity was accompanied by a corresponding increase in gasoline yield of 5.0-6.5%.
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| 10. |
- Engström, V., et al.
(författare)
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The effect of seed size on the growth of silicalite-1 films on gold surfaces
- 2000
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 38:1, s. 51-60
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Tidskriftsartikel (refereegranskat)abstract
- Silicalite-1 films grown on gold surfaces seeded with colloidal crystals with a size of 60, 165 and 320 nm were investigated by reflection–absorption infrared spectroscopy, scanning electron microscopy and X-ray diffraction in order to follow up the formation of nano-scale defects and to determine the optimal synthesis conditions for preparation of silicalite-1 films with a low concentration of defects. Using 60-nm-sized colloidal crystals, the seeding method was capable of producing silicalite-1 films with low concentrations of defects and with thicknesses ranging from 100 to 300 nm, which are predominantly oriented with the a-axis perpendicular to the surface. Hydrothermal treatment times of the 60-nm-seeded surfaces longer than 36 h as well as the seeding with 165 or 320 nm colloidal crystals substantially enhanced the formation of defects in the films.
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| 11. |
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| 12. |
- Grahn, Mattias, et al.
(författare)
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Silicalite-1 coated ATR elements as sensitive chemical sensor probes
- 2005
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 81:1-3, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- A novel sensitive chemical sensor probe has been fabricated. The sensor principle is based on silicalite-1 coated ATR (attenuated total reflection) elements and FTIR spectroscopy. The microporous silicalite-1 film enriches the analyte to the probe surface, thus increasing the sensitivity. At a relative pressure of n-hexane in helium of 6 × 10−5 the sensitivity of the probe is approximately 85 times higher for the silicalite-1 coated element compared to a 10 cm transmission gas cell and ca. 180 times higher compared to an uncoated element. The performance of the probe is illustrated by determination of an adsorption isotherm for n-hexane in silicalite-1.
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| 13. |
- Haglund, R., et al.
(författare)
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Upgrading of hydropyrolysis coal tar by hydroprocessing
- 1991
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Ingår i: Erdöl Erdgas Kohle. - 0179-3187. ; 107:5, s. 232-235
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Tidskriftsartikel (refereegranskat)abstract
- Upgrading of a hydropyrolysis coal tar by hydroprocessing was investigated using different process conditions. The response of the hydropyrolysis tar to hydroprocessing was compared to those of a conventional coal tar and two heavy oil fractions. At comparable conditions, the removal of heteroatoms from the hydropyrolysis tar was more effective than from the conventional tar and, in particular, than from the oil fractions. Using conditions typical for hydroprocessing of heavy oil fractions, the contents of N, O as well as S in the hydropyrolysis tar were reduced by more than 90%. Hydroprocessing also resulted in a considerable increase in the gasoline fraction of the tar.
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| 14. |
- Hedlund, Jonas, et al.
(författare)
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Controlling the preferred orientation in silicalite-1 films synthesized by seeding
- 1999
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 28:1, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- Single crystal silicon (100) wafers were seeded with colloidal silicalite-1 crystals and hydrothermally treated in a precursor solution to grow thin silicalite-1 films. A total of 28 experiments in eight series were investigated with SEM and XRD to evaluate the preferred orientation of the crystals constituting the films. The investigated parameters in the film formation process were seed crystal size, amount of adsorbed seed crystals and film thickness after hydrothermal treatment of the seeded substrates. In thin films, most of the crystalline material is oriented with the b-axis perpendicular to the substrate surface. In thick films, most of the crystalline material is oriented with the a-axis perpendicular to the substrate surface. The change in preferred orientation with film thickness is faster when small seeds are used. The amount of adsorbed seeds has a larger influence on the preferred orientation when large seeds are used. A mechanism explaining these trends is proposed. The choice of size and coverage of seeds can be used to control the preferred orientation of the crystals in a film of given thickness within certain limitations.
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| 15. |
- Hedlund, Jonas, et al.
(författare)
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High-flux MFI membranes
- 2002
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Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 52:3, s. 179-189
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and evaluation of high performance MFI-type membranes is described. These systems exhibit fluxes that are one to two orders of magnitude higher than previous literature reports, with comparable selectivities, when tested for various single component gases and for mixtures of C4, C6 and xylene isomers.These materials are the result of a rational fabrication approach targeting ultra-thin, defect-free MFI films on open supports by using a two-step support masking technique and a monolayer of colloidal nucleation seeds, followed by in situ hydrothermal growth, producing a defect-free film with a thickness of 0.5 μm. Reproducibility of the membrane preparation was excellent.
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| 16. |
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| 17. |
- Hedlund, Jonas, et al.
(författare)
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Synthesis of thin molecular sieve films
- 1999
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Ingår i: Nanostructured materials. - 0965-9773 .- 1872-9150. ; 12:1-4, s. 413-416
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Tidskriftsartikel (refereegranskat)abstract
- A method to synthesize thin films of various molecular sieves on a number of substrates employing pre-seeding has been developed. The substrate is modified to enable adsorption of seed crystals. Substrates with an originally negative surface charge are charge reversed by adsorption of cationic polymer molecules. Nobel metal substrates are first silanized to obtain a negative surface charge. Nano seed crystals are adsorbed on the modified substrates from a sol and induced to grow in a synthesis solution to form a dense film with controlled thickness. The versatility of the method may be of great value in the development of novel applications. Films have been tested in membrane and sensor applications with successful results.
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| 18. |
- Hedlund, Jonas, et al.
(författare)
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Synthesis of ultra thin films of molecular sieves by the seed film method
- 1997
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Ingår i: Progress in zeolite and microporous materials. - Amsterdam : Elsevier. - 0444823441 ; , s. 2203-2210
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Konferensbidrag (refereegranskat)abstract
- A novel and flexible technique for synthesizing continuous ultra thin (<100 nm) molecular sieve films on substrates has been developed. The technique consists of two steps. A monolayer of discrete colloidal zeolite seed crystals is adsorbed on the substrate, whereafter the crystals are allowed to grow into a continuous film upon hydrothermal treatment in a molecular sieve precursor solution. The technique is exemplified by the formation of silicalite-1 films on silicon wafers. The final film thickness in the examples presented was in the range 80 and 800 nm. The films are continuous and crystalline as confirmed by SEM, Kr-adsorption data, ellipsometry, XRD and FTIR.
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| 19. |
- Hedlund, Jonas, et al.
(författare)
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Thin zeolite NA films by the seed film method
- 1999
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Ingår i: Proceedings of the 12th International Zeolite Conference. - Warrendale, Pa : Materials Research Society. - 1558994637 ; , s. 1857-1862
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Konferensbidrag (refereegranskat)
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| 20. |
- Hedlund, Jonas, et al.
(författare)
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Ultrathin oriented zeolite LTA films
- 1997
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Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; :13, s. 1193-1194
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Tidskriftsartikel (refereegranskat)abstract
- Ultrathin oriented films of zeolite LTA are prepared on single-crystal alumina supports by a method including adsorption of LTA seeds on the support followed by hydrothermal film crystallization.
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| 21. |
- Hedlund, Jonas, et al.
(författare)
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ZSM-5 membranes synthesized without organic templates using a seeding technique
- 1999
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Ingår i: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 159:1-2, s. 263-273
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Tidskriftsartikel (refereegranskat)abstract
- Porous α-alumina supports were seeded with colloidal TPA-silicalite-1 crystals and calcined. The supports were treated in a synthesis solution to grow the seed crystals into ZSM-5 films. The synthesis solution was free from organic template molecules in order to avoid the calcination step which often introduces cracks in the synthesized zeolite film. An SEM investigation indicated that the zeolite films on the supports were defect free and that the film thickness was approximately 1.5 μm. XRD data showed that the film consisted of well-crystallized ZSM-5. The permeance in single gas experiments decreased in the order H2O, H2, CO2, O2, N2 and CH4. The difference in permeance between each molecular species in the series was almost one order of magnitude which indicated that the membranes were of a high quality. Molecules larger than CH4 permeated with similar and low rates, independent of their kinetic diameters, indicating a non-selective permeation path through defects in the zeolite films. However, the permeance of these larger molecules was less than 1/10 000 of that for H2O. The highest measured separation factors for binary mixtures of N2/SF6 and H2/i-C4 were 110 and 99.
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| 22. |
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| 23. |
- Jareman, Fredrik, et al.
(författare)
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Effects of aluminum content on the separation properties of MFI membranes
- 2003
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Ingår i: Separation and Purification Technology. - 1383-5866 .- 1873-3794. ; 32:1-3, s. 159-163
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Tidskriftsartikel (refereegranskat)abstract
- MFI membranes with almost identical film thickness and defect distribution but different Si/Al ratio were evaluated by separation of butane and hexane isomers. Film thickness was evaluated by SEM and defect distribution by porosimetry. When the temperature was varied, the membranes showed similar separation trends for butanes, but clear differences were observed for hexane separation. The hexane separation factor varied with temperature for the silicalite-1 membrane but was constant for the ZSM-5 membrane. It is believed that this difference may be a result of differences in adsorption properties.
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| 24. |
- Jareman, Fredrik, et al.
(författare)
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Modelling of single gas permeation in real MFI membranes
- 2004
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Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 236:1-2, s. 81-89
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Tidskriftsartikel (refereegranskat)abstract
- A novel permeation model for flow through defects and zeolite pores in real MFI membranes, also accounting for substrate effects has been developed. Defect distributions for two types of MFI membranes were determined from porosimetry data using the model, which incorporated the Horvath Kawazoe (micropores) or the Kelvin equation (mesopores). The narrowest (1.08 nm) and also most common defects were found to be separated with a distance of 10–40 μm according to the model. Diffusion coefficients for hydrogen, helium, nitrogen and SF6 in the zeolite were further determined from single gas permeation data using the model using the independently determined defect distribution. The coefficients are consistent with values previously reported in the literature.
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| 25. |
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