N-heptane adsorption and desorption in mesoporous materials

Zaleski, R.; Gorgol, M.; Blazewicz, A; Kierys, Agnieszka; Goworek, J.

doi:10.1088/1742-6596/618/1/012040

Cited by 4 publications

(5 citation statements)

References 15 publications

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“…In consequence, the o -Ps pick-off lifetime can be used to evaluate free volume size. The great advantage of the o -Ps probe is the ability to track in situ changes of free volume size and concentration during adsorption–desorption process and provide unique information that can help in revealing the underlying mechanism of the studied phenomena. − …”

Section: Introductionmentioning

confidence: 99%

Positron Probing of Liquid-free Volume To Investigate Adsorption–Desorption Behavior of Water in Two-Dimensional Mesoporous SBA-3

et al. 2017

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Transport of fluids through channels and cavities of nano/mesoporous materials is of paramount importance in various fields of science and industry. The transport properties can be well derived from the adsorption− desorption behavior of fluids. Positron annihilation lifetime spectroscopy (PALS) allows probing adsorption−desorption of water from 2D mesopores of SBA-3. In situ study of the size of evolving water-free volumes during successive stages of adsorption and desorption is a sensitive way to elucidate the course of pore filling and emptying. The changes of positron annihilation parameters indicate that adsorption of water is mediated through the formation of isles on the surface of the pore walls, and these, in turn, develop into water plugs. Subsequently, these plugs grow and consecutively join together when the distance between them decreases to ca. 1 nm until the complete capillary condensation occurs. Akin to adsorption, desorption of water from the pores involves the formation of cavities capped with water plugs. The final stage of desorption shows the presence of water trapped in micropores in the pore walls. The linear dependence between the volume of water and the intensity of the water-related positronium component allows to estimate the amount of water in the system. The study highlights an approach to understand adsorption−desorption mechanism of liquids in mesopores by probing liquid-free volumes using ortho-positronium.

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Section: Introductionmentioning

confidence: 99%

Positron Probing of Liquid-free Volume To Investigate Adsorption–Desorption Behavior of Water in Two-Dimensional Mesoporous SBA-3

et al. 2017

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“…Undoubtedly, TEOS is located mostly in micropores at this stage, which is confirmed by the decrease of their size (τ 4 ) and concentration ( I 4 ). The other changes may be the consequence of the suppression of the o-Ps migration, , i.e., the o-Ps fraction formed in the polymer intrachain spaces, which were open to micropores before swelling, can no longer migrate through micropores to mesopores. Such “sealing” of the polymer may be also the reason for the small shortening of τ 3 due to the initial TEOS penetration of the largest intrachain spaces.…”

Section: Resultsmentioning

confidence: 99%

Macro- and Nanoscopic Studies of Porous Polymer Swelling

et al. 2017

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A commercial Amberlite XAD7HP resin was investigated as a typical porous polymer which swells in tetraethoxysilane (TEOS). TEOS appears to be an extremely effective polymer swelling agent; thus, it serves as an easily assimilable silica source in polymer−silica composites. The present study discusses the application of light microscopy (LM) and positron annihilation lifetime spectroscopy (PALS) for the studies of macroscopic and microscopic features during the progress of polymer swelling. LM offers precise information on the swelling in the solvent vapor, especially for the well-defined, spherically shaped particles of the polymer. The swelling of a porous polymer consists of the swelling of pore walls and adsorption of the solvent on the internal surface of the walls. PALS provides an opportunity to recognize the sequence of solvent penetration into porous polymer particles. It allows in situ monitoring of the evolution of every free volume in the sample under study.

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“…The interparticle component predominates in the spectrum which is the result of o-Ps migration outside mesopores [15,19]. The introduction of oil causes that o-Ps forms also at the oil-silicon interface (τ 3 = 1.50(6) ns) and in bubbles distended by o-Ps in the oil (τ 4 = 3.22(2) ns), while the contribution of micropores becomes negligible.…”

Section: Resultsmentioning

confidence: 99%

“…The popular model material is MCM-41, which pores are relatively long, unconnected cylinders of uniform size [11]. Numerous PALS studies of this material [12][13][14][15] make it sufficiently well known to be a preferable choice for calibration of positron porosimetry. However, tailoring of the total pore volume and specific surface of MCM-41 in the wide range, which is required for the calibration, is impossible at the synthesis stage.…”

Section: Introductionmentioning

confidence: 99%

Controlled Porosity of MCM-41 Obtained by Partial Blocking of Pores by Silicon Oil

et al. 2017

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Partial blocking of mesopores in the ordered MCM-41 silica by DC550 silicon oil was proposed as a preparation method of the material with controlled porosity and fixed pore size. The porosity of the samples with various content of DC550 was examined with the use of low temperature nitrogen sorption and positron annihilation lifetime spectroscopy. It was shown that the oil blocks the primary pores by forming the plugs near its entrances, but also partially locates in the interparticle spaces. The comparison of the results obtained from both investigation techniques was used to make the first attempt to obtain the calibration of ortho-positronium intensity, depending on pore volume. This is necessary to improve the utility of positron annihilation lifetime spectroscopy as a porosimetric technique. The need to take the migration of positronium to larger free volume into account is discussed.

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N-heptane adsorption and desorption in mesoporous materials

Cited by 4 publications

References 15 publications

Positron Probing of Liquid-free Volume To Investigate Adsorption–Desorption Behavior of Water in Two-Dimensional Mesoporous SBA-3

Positron Probing of Liquid-free Volume To Investigate Adsorption–Desorption Behavior of Water in Two-Dimensional Mesoporous SBA-3

Macro- and Nanoscopic Studies of Porous Polymer Swelling

Controlled Porosity of MCM-41 Obtained by Partial Blocking of Pores by Silicon Oil

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