Behavior of the (010) face of silicalite crystal

Iwasaki, Akira; Hirata, Mitsuji; Kudo, Isao; Sano, T.

doi:10.1016/0144-2449(95)00102-6

Cited by 42 publications

(19 citation statements)

References 22 publications

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“…Zeolite crystal size and habit, for example, can be modified via the adjustment of synthesis parameters, such as the molar composition and pH of growth solutions, or synthesis temperature . Additional routes to tailor crystallization include sacrificial templating strategies, the incorporation of surfactants (capping agents), and the use of organic structure-directing agents (OSDAs) .…”

Section: Introductionmentioning

confidence: 99%

Tuning Zeolite Precursor Interactions by Switching the Valence of Polyamine Modifiers

2016

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Nonclassical mechanisms of crystal growth often involve the formation of amorphous precursors that play a direct role in what is generally referred to as crystallization by particle attachment (or CPA). One of the most studied CPA systems in the literature is zeolite MFI, which is a microporous crystal with siliceous (silicalite-1) and aluminosilicate (ZSM-5) isostructures. The self-assembly, microstructural evolution, and mechanistic role of nanoparticle precursors (1-6 nm) during silicalite-1 crystallization have been the subjects of prior investigation by combined experimental and modeling techniques. Here we investigate for the first time the effects of zeolite growth modifiers (ZGMs) on MFI precursors. ZGMs are organic molecules that alter the anisotropic rate(s) of crystal growth as a means of tailoring crystal size and/or habit. We show that most ZGMs have little effect on precursor assembly and evolution during the prenucleation stages of silicalite-1 and ZSM-5 synthesis; however, studies at varying alkalinity reveal that pH can be used as a "switch" to tune ZGM speciation and concurrently the colloidal stability of precursors. This has been proven effective for various polyamine compounds, such as spermine, that exhibit divalent (positive) charge near negatively charged nanoparticle surfaces. Our finding is consistent with colloidal models that predict a higher concentration of divalent modifiers within the diffuse double layer surrounding the surfaces of (alumino)silicate precursors. Multivalent polyamines seemingly promote precursor-precursor aggregation at elevated temperature, which is consistent with a proposed hypothesis that modifiers with two or more sufficiently spaced cationic functional moieties are capable of bridging neighboring precursor surfaces, thus overcoming an electrostatic repulsive force that contributes to their colloidal stability. Given the importance of precursor-precursor and precursor-crystal interactions in zeolite nucleation and growth, respectively, our observations provide additional insight into the role of organics in zeolite crystallization.

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Section: Introductionmentioning

confidence: 99%

Tuning Zeolite Precursor Interactions by Switching the Valence of Polyamine Modifiers

2016

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“…It is generally accepted that the adherence of new MFI nuclei in the bulk solution to the (0k0) faces of the original MFI seeds was the main reason of a-oriented twin growth during secondary growth. 23,24 The hydrophobic hydration sphere formed around TPA in aqueous solution is partially or completely replaced by silica when a sufficient amount of soluble silicate species is available. 25 The formed organic-inorganic composite species could contribute to nucleation and then evolve to zeolite crystals through several intermediate states.…”

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confidence: 99%

Rapid fabrication of highly b-oriented zeolite MFI thin films using ammonium salts as crystallization-mediating agents

et al. 2015

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“…The formation of such displacement boundaries could be because of a multi-site nucleation of subgrains at different positions on the growing (010) surface of the crystal. When separately nucleating subgrains grow larger, they will merge to form one larger intergrowth component, which was observed by in situ optical microscopy in MFI-type silicalite crystals (Iwasaki et al, 1996). However, when the different subgrains join, a displacement boundary can occur that can extend to the top surface of the crystal, as observed.…”

Section: Discussionmentioning

confidence: 89%

“…The black full circles show the diffraction spots from the underlying matrix while the gray full circles show those from the different ramps. A possible reason for the existence of the ramps can be found in the growth of the coffin-shaped crystal by small zeolite crystal precursors existing in the solution, as suggested by Iwasaki et al (1996) and Gonthier and Thompson (1994) who observed small particles around the crystals during the crystal growth that might adhere to the crystal surface and subsequently grow. When such precursors or small crystals come in contact with a crystal surface exhibiting terraces as seen in the SEM image of Figure 7a, they can be expected to attach to the crystal at an angle as indicated in the cross-section schematics of Figures 11c and 11d.…”

Section: Discussionmentioning

confidence: 95%

Intergrowth of Components and Ramps in Coffin-Shaped ZSM-5 Zeolite Crystals Unraveled by Focused Ion Beam-Assisted Transmission Electron Microscopy

Roeffaers

Bartholomeeusen

et al. 2013

Microsc Microanal

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Scanning electron microscopy, focused ion beam (FIB), and transmission electron microscopy are combined to study the intergrowth of 90° rotational components and of ramps in coffin-shaped ZSM-5 crystals. The 90° rotational boundaries with local zig-zag features between different intergrowth components are observed in the main part of crystal. Also a new kind of displacement boundary is described. At the displacement boundary there is a shift of the unit cells along the boundary without a change in orientation. Based on lamellae prepared with FIB from different positions of the ramps and crystal, the orientation relationships between ramps and the main part of the crystal are studied and the three-dimensional morphology and growth mechanism of the ramp are illustrated.

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Behavior of the (010) face of silicalite crystal

Cited by 42 publications

References 22 publications

Tuning Zeolite Precursor Interactions by Switching the Valence of Polyamine Modifiers

Tuning Zeolite Precursor Interactions by Switching the Valence of Polyamine Modifiers

Rapid fabrication of highly b-oriented zeolite MFI thin films using ammonium salts as crystallization-mediating agents

Intergrowth of Components and Ramps in Coffin-Shaped ZSM-5 Zeolite Crystals Unraveled by Focused Ion Beam-Assisted Transmission Electron Microscopy

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