Nitrogen Distribution at 77.7 K in Mesoporous Gelsil 50 Generated via Evolutionary Minimization with Statistical Descriptors Derived from Adsorption and In Situ SANS

Eschricht, N.; Hoinkis, E.; Mädler, Fritz

doi:10.1021/la062587m

Cited by 15 publications

(18 citation statements)

References 31 publications

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“…Differences mainly arise from the broad pore size distribution together with network effects attributed to highly disordered pore structures. A vapor bubble formed in a larger cavity, for instance, can invade neighboring smaller voids, a process which leads to ramified vapor clusters . Thus, one expects that a localized cavitation event taking place in a wider cavity advances the evaporation from smaller pores connected to it.…”

Section: Resultsmentioning

confidence: 99%

Cavitation and Pore Blocking in Nanoporous Glasses

et al. 2011

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In gas adsorption studies, porous glasses are frequently referred to as model materials for highly disordered mesopore systems. Numerous works suggest that an accurate interpretation of physisorption isotherms requires a complete understanding of network effects upon adsorption and desorption, respectively. The present article deals with nitrogen and argon adsorption at different temperatures (77 and 87 K) performed on a series of novel nanoporous glasses (NPG) with different mean pore widths. NPG samples contain smaller mesopores and significantly higher microporosity than porous Vycor glass or controlled pore glass. Since the mean pore width of NPG can be tuned sensitively, the evolution of adsorption characteristics with respect to a broadening pore network can be investigated starting from the narrowest nanopore width. With an increasing mean pore width, a H2-type hysteresis develops gradually which finally transforms into a H1-type. In this connection, a transition from a cavitation-induced desorption toward desorption controlled by pore blocking can be observed. Furthermore, we find concrete hints for a pore size dependence of the relative pressure of cavitation in highly disordered pore systems. By comparing nitrogen and argon adsorption, a comprehensive insight into adsorption mechanisms in novel disordered materials is provided.

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Section: Resultsmentioning

confidence: 99%

Cavitation and Pore Blocking in Nanoporous Glasses

et al. 2011

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“…Therefore, these ordered cagelike materials have attracted a great deal of interest because of their unique pore structures and potential applications in immobilization of biomolecules, drug delivery, separation, and catalysis. On adsorption, nitrogen behaves quite independently in different parts of the pore system . With increasing pressure, necks of larger size are progressively filled with liquid nitrogen.…”

Section: Introductionmentioning

confidence: 99%

“…On adsorption, nitrogen behaves quite independently in different parts of the pore system. 23 With increasing pressure, necks of larger size are progressively filled with liquid nitrogen. After all the necks are filled, capillary condensation of nitrogen takes place in the large cages with further increase in pressure.…”

Section: ■ Introductionmentioning

confidence: 99%

Estimation of Neck Size Distribution in Ordered Cagelike Materials Using Nitrogen and Water Desorption Isotherms

Morishige

2017

J. Phys. Chem. C

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To estimate the neck size distributions in ordered cagelike materials KIT-5 with prolonged hydrothermal treatments, we measured the desorption isotherms of water at 293 K on the cagelike materials and then calculated the desorption isotherms of nitrogen at 77 K and water at 293 K based on the model pore networks with normal distributions of neck sizes that mimic the pore structure of KIT-5. First, it was found that the position of the desorption isotherms does not at all reflect the mean size of necks unless the width of the neck size distribution is fixed, and thus the simple analysis of the desorption isotherms in the absence of networking effects leads to erroneous distribution of neck sizes. The gradual desorption isotherms of nitrogen and water observed for KIT-5 samples were not well reproduced based on the model pore networks with no correlation in the spatial distribution of neck sizes. On the other hand, inclusion of correlation in the spatial distribution of neck sizes led to exceedingly better fits between the experimental and calculated desorption isotherms of nitrogen and water on KIT-5. From the point of view of estimation of neck size distributions in the ordered cagelike materials, the water adsorption method at 293 K is superior to the nitrogen adsorption method at 77 K.

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“…Use of nitrogen in conjunction with SANS is based on the fact that the SLD of liquid nitrogen at T ffi 78 K (ρ [31], and SBA-15 [32] shows that the ratio of the intensity measured from the samples after complete pore filling (I(Q) filled ) and the intensity (I(Q) VAC ) from evacuated samples ) ( 1 is nearly met for capillary-condensed nitrogen in silica. Thus, assuming that the density of the adsorbed film formed on pore walls is similar to that of bulk liquid nitrogen, SANS from completely or partially filled pores can be approximated by the two-phase model: the solid silica matrix with liquid nitrogen (phase 1), and the liquid-free space (phase 2) [33].…”

mentioning

confidence: 99%

Neutron and X-Ray Porosimetry

Melnichenko

2016

Small-Angle Scattering From Confined and Interfacial Fluids

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This Chapter considers principles of the neutron-and x-ray scattering-based porosimetry, which exploits contrast variation and contrast matching method. The coherent scattering from porous solids arises largely from the contrast between the empty and filled pores. A porous medium is exposed to a solvent vapor having the same neutron scattering length density or electron density as the matrix skeleton. The smallest pores are filled with a condensed liquid already at low relative pressure, followed by filling of progressively larger pores. Thus, measured as a function of the relative pressure, SAS probes sub-populations of pores of increasing average size, which is calculated using the Kelvin equation. Illustrative examples are given of how SAS can be used for structural characterization of various types of porous materials including low-dielectric constant polymer films, porous silicas, carbonaceous materials, and Nafion membranes.

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Nitrogen Distribution at 77.7 K in Mesoporous Gelsil 50 Generated via Evolutionary Minimization with Statistical Descriptors Derived from Adsorption and In Situ SANS

Cited by 15 publications

References 31 publications

Cavitation and Pore Blocking in Nanoporous Glasses

Cavitation and Pore Blocking in Nanoporous Glasses

Estimation of Neck Size Distribution in Ordered Cagelike Materials Using Nitrogen and Water Desorption Isotherms

Neutron and X-Ray Porosimetry

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