Adsorption-Induced Deformation of Hierarchically Structured Mesoporous Silica—Effect of Pore-Level Anisotropy

Balzer, Christian; Waag, Anna; Gehret, Stefan; Reichenauer, Gudrun; Putz, Florian; Hüsing, Nicola; Paris, Oskar; Bernstein, Noam; Gor, Gennady Y.; Neimark, Alexander V.

doi:10.1021/acs.langmuir.7b00468

Cited by 49 publications

(109 citation statements)

References 77 publications

(153 reference statements)

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“…The stress induced by adsorption can be anisotropic (e.g., in a cylindrical pore, adsorptioninduced stresses are not identical in the axial and in the radial directions [7,8]). Also, pores can be organized in an anisotropic manner, or the mechanical behavior of the material can also be anisotropic.…”

Section: B Anisotropymentioning

confidence: 99%

“…In coal for instance, the anisotropy of the adsorption-induced strains was shown to be mostly due to the anisotropy of the mechanical behavior, while the adsorption stress itself is mostly isotropic [44]. Anisotropic effects can also add or counterbalance each other: in silica struts containing parallel cylindrical mesopores [7], the cylindrical pore geometry makes the axial adsorption-induced stress about 3 times larger than the radial one but, as consequence of the anisotropy of the mechanical properties of the porous struts, deformations at the scale of a strut are roughly isotropic.…”

Section: B Anisotropymentioning

confidence: 99%

“…To estimate the adsorption-induced deformations of an anisotropic mesoporous silica body made of parallel cylindrical channels, both the thermodynamic approach [7] and the surface stress approach [8] were used recently. The two approaches are compared in [8]: above capillary condensation, they yield identical results, while, below capillary condensation (i.e., in the film regime), they provide qualitatively similar but quantitatively different responses.…”

Section: Introductionmentioning

confidence: 99%

“…The two approaches are compared in [8]: above capillary condensation, they yield identical results, while, below capillary condensation (i.e., in the film regime), they provide qualitatively similar but quantitatively different responses. To me, this difference might at least partly be due to the fact that the input parameters for the two works are different: for instance, the relation between thickness of adsorbed film and relative pressure is given by the BET model in [8], while it is given by the DBdB theory in [7].…”

Section: Introductionmentioning

confidence: 99%

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Coupling between adsorption and mechanics (and vice versa)

Vandamme

2019

Current Opinion in Chemical Engineering

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Adsorption can deform porous solids, and mechanical stresses or strains can impact the adsorption process: this mini-review is dedicated to this coupling. After introducing some frameworks used to predict adsorption-induced strains, the question of how important it is to take into account the impact of mechanics on the adsorption process is addressed. Finally, some specific complexities (e.g., of the microstructure, or of the mechanical behavior of the adsorbent) that the community aims at integrating into the prediction of adsorption-induced strains are addressed. 2. Some frameworks to predict adsorption-induced strains The discussion in this section is quite generic and disregards specific complexities of the material, which will be addressed later in the manuscript. A first pore-scale approach to predict adsorption-induced strains is a thermodynamic one, which consists in identifying the energy to minimize in the so-called osmotic ensemble, which is the right thermodynamic ensemble to address adsorption-induced deformations [4]. Through this approach, Ravikovitch and Neimark [5] first showed that adsorption induces a mechanical stress (sometimes

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Section: B Anisotropymentioning

confidence: 99%

Section: B Anisotropymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Coupling between adsorption and mechanics (and vice versa)

Vandamme

2019

Current Opinion in Chemical Engineering

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“…Together with the printed shape and the macroporous network of struts, these anisotropic mesopores form three geometrically well‐defined hierarchy levels. This offers a huge playground for advanced characterization methods or even for mechanical modeling, but also for a number of applications, including separation, sensing and actuation, or bioinspired materials design, to name just a few.…”

mentioning

confidence: 99%

3D Printing of Hierarchical Porous Silica and α‐Quartz

Putz

Scherer

Ober

et al. 2018

Adv Materials Technologies

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The ability to macroscopically shape highly porous oxide materials while concomitantly tailoring the porous network structure as desired by simple and environmentally friendly processes is of great importance in many fields. Here, a purely aqueous printing process toward deliberately shaped, hierarchically organized amorphous silica and the corresponding polycrystalline quartz analogues based on a direct ink writing process (DIW) is presented. The key to success is the careful development of the sol–gel ink, which is based on an acidic aqueous sol of a glycolated silane and structure‐directing agents. The resulting 3D (DIW) printed silica consists of a macroporous network of struts comprising hexagonally arranged mesopores on a 2D hexagonal lattice. Together with a printed porous superstructure on the millimeter scale, well‐defined pore sizes and shapes on at least three hierarchy levels can thus be fabricated. The introduction of devitrifying agents in the printed green part and subsequent heat treatment allows for the transformation of the silica structure into polycrystalline α‐quartz. While small pores (micro‐ and mesopores below 10 nm) are lost, the printed morphology and the macroporous network of struts is preserved during crystallization.

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Condensation‐Controlled Toposelective Vapor Deposition in Nano‐ and Microcavities: Theory, Methods, Applications, and Related Technologies

Lovikka¹

2022

Adv Materials Inter

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fabricable while we are facing increasing complexity in, for example, microelectronics. [6,7] For these reasons, challenges such as bad pattern alignment, [8,9] or pinch-off of pores and void formation [10][11][12][13] in top-down fabrication need to be addressed. On the other hand, a continuous film causes tradeoffs in desirable properties in many nanotechnological applications, such as losing mesoporosity while increasing the mechanical properties of an aerogel [14] or reducing catalytic activity while increasing catalyst stability against sintering. [15] To counter these problems, even atomic layer deposition (ALD), a method known for its superior conformality, has been expanded into area-selective fabrication by the addition of etching and functionalization steps in the workflow. [16][17][18][19] However, additional steps make the workflow increasingly slow, complex, and dependent on surface chemistries. There is also a growing interest in area-selectivity based on properties of precursors and substrates in ALD, [20] but new requirements on precursors would narrow down potential reagents. Furthermore, even conformal methods would leave voids inside ink-bottle-shaped pores and under composite undercuts [21] because conformal methods would clog the pore mouths before filling the internal parts. These problems have very recently revoked calls for profound changes and even a paradigm shift toward selective functionalization in the nanoscale. [18,20,[22][23][24][25] Special attention should be paid to inherently non-conformal methods, especially if they are surface-selective towards cavities. This includes both surface-selective subconformal coatings, those that coat only extremities and protrusions of a substrate, and surface-selective superconformal coatings, those that fill or coat cavities.Bottom-up approaches could eliminate the aforementioned problems while reducing the needed steps for surface-selective treatments-instead of breaking or carving things smaller and using miniaturized techniques (top-down), coatings could be grown self-aligning (bottom-up). One bottom-up category is surface-shape-selective deposition. Currently, this category has limited approaches, which are often based on either anisotropic processes such as directional plasma etching [26] or reagent flux, force fields, [27] competitive adsorption, [28] or reagents and additives with specific properties. [22] Truly bottom-up gap-filling technologies, especially those free of line-of-sight limitations, Nanotechnology drives technological progress in many frontiers, from electronics to medicine, from tougher composites to adaptive surfaces. As the feature sizes are made smaller, the importance of surfaces is increased. Many of the most powerful methods for surface manipulation are variants of vapor deposition (VD). However, VD is typically not surface-selective and, therefore, extra work steps are needed to integrate the methods into nanofabrication routines. Furthermore, many fields are moving toward 3D nanostructures, which unavoidably means...

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Adsorption-Induced Deformation of Hierarchically Structured Mesoporous Silica—Effect of Pore-Level Anisotropy

Cited by 49 publications

References 77 publications

Coupling between adsorption and mechanics (and vice versa)

Coupling between adsorption and mechanics (and vice versa)

3D Printing of Hierarchical Porous Silica and α‐Quartz

Condensation‐Controlled Toposelective Vapor Deposition in Nano‐ and Microcavities: Theory, Methods, Applications, and Related Technologies

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