Transient Structural Evolution Upon Thermal Dehydration in Layered-Hectorite Nanoparticles

Sato, K.; Numata, Kazuomi; Fujimoto, Koichiro

doi:10.1142/s0219581x12400339

Cited by 7 publications

(6 citation statements)

References 16 publications

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“…1 This auto-agglomeration process enhanced by H 2 O molecules, the so-called molecular self-assembly of 2D nanosheets, is increasingly of importance for dealing with global environmental issues. [2][3][4] For example, long-term self-assembly in layered saponite creates novel types of local structures, in which Cs cations are bound so strongly that they cannot be removed by strong hydrochloric acid solution. 2 In the recent model of giant earthquake nucleation, hydration of pore fluid in the interlayer spaces of clay minerals is associated with earthquake slip, which may lead to a weakening of plate-boundary faults.…”

Section: Introductionmentioning

confidence: 99%

“…2 In the recent model of giant earthquake nucleation, hydration of pore fluid in the interlayer spaces of clay minerals is associated with earthquake slip, which may lead to a weakening of plate-boundary faults. 3,4 Besides the global environmental issues, self-assembly is nowadays a disciplined technique for nanofabrication being not accessible for conventional techniques of materials synthesis. [5][6][7] Smectites are inorganic layered materials with 2D nanosheets consisting of tetrahedral and octahedral units, which undergo a self-assembly aided by H 2 O molecules existing in the Ångstromscale interlayer spaces.…”

Section: Introductionmentioning

confidence: 99%

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Long-term self-assembly of inorganic layered materials influenced by the local states of the interlayer cations

Sato

Numata

Dai

et al. 2014

Phys. Chem. Chem. Phys.

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A wide variety of parameters as, e.g., temperature, humidity, particle size, and cation state are known to influence the agglomeration process of two-dimensional (2D) nanosheets, called self-assembly, in inorganic layered materials. The detailed studies on which parameters are decisive and how they influence the self-assembly, however, have not been performed yet. Here, the long-term self-assembly was studied for layered stevensite and hectorite, and compared with our previous data of saponite for elucidating an influence of local states of the interlayer cations. The results were analyzed with respect to a recently established rheological model, in which 2D nanosheets migrate parallel to the layer direction aided by water molecules as lubricants [K. Sato et al., J. Phys. Chem. C, 2012, 116, 22954]. With decreasing the strength of the local electric fields facing to the interlayer spaces, cation positions split into two or three, which makes the distribution of water molecules more uniformly. These water molecules enhance the rheological motion of the 2D nanosheets parallel to the layer direction, thus accelerating the self-assembly process.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Long-term self-assembly of inorganic layered materials influenced by the local states of the interlayer cations

Sato

Numata

Dai

et al. 2014

Phys. Chem. Chem. Phys.

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“…It has been found that the above-mentioned two nanosheet insertion type local molecular structure, referred to as type B, appearing during self-assembly is associated with a number of global environmental issues [4][5][6]. For example, the characteristic local structures as a nanosheet edge and a wedge-shaped frayed part available in the voids of type B are responsible for site specific Cs adsorption [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…For example, the characteristic local structures as a nanosheet edge and a wedge-shaped frayed part available in the voids of type B are responsible for site specific Cs adsorption [4,5]. Pore fluid in this local structure has been suggested to be related to earthquake slip weakening in plate-boundary faults [6]. In the present study, the reversibility of self-assembly involving the rheological motion of 2D nanosheets with the aid of H 2 O molecules was studied for saponite inorganic layered nanoparticles by means of X-ray diffraction (XRD), dilatometry (DLT), and Ps annihilation spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Study of reversibility of self-assembly in saponite layered nanoparticles

Numata

Sato

2014

JJAP Conf. Proc.

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The reversible process of self-assembly involving the rheological motion of 2-dimensional nanosheets with the aid of water molecules was studied for saponite inorganic layered nanoparticles by dilatometry and positronium lifetime spectroscopy. The two nanosheet insertion type local molecular structure, dominant in the dehydrated state, was not fully reproducible upon dehydration for the self-assembled sample. The two nanosheet insertion type local structure could thus disappear when saponite goes through self-assembly several times. It was furthermore found that a local structure with a void size slightly larger than that in the two nanosheet insertion type structure exists before self-assembly. This structure, presumably due to curved nanosheets, is metastable and gradually disappears during self-assembly.

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“…It is known that 2D nanosheets spontaneously agglomerate with well-defined local structures through their mutual interactions with the aid of H 2 O molecules. This agglomeration process toward structural densification, so-called self-assembly of 2D nanosheets, is increasingly of importance for dealing with global environmental issues [2][3][4][5]. For example, the local molecular structures appearing upon self-assembly have been found to play an important role in the Cs adsorption site [2,3].…”

Section: Introductionmentioning

confidence: 99%

Study of self-assembly for mechanochemically-milled saponite nanoparticles

2014

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The rheological mechanism of long-term self-assembly triggered by H 2 O molecules was studied for unmilled and mechanochemically-milled saponite nanoparticles by means of thermogravimetry and differential thermal analysis (TG-DTA), dilatometry (DLT), and positronium (Ps) lifetime spectroscopy. For unmilled saponite, the adsorption of H 2 O molecules due to hydration caused volume expansion arising from an increase in the basal spacing as well as weight gain with a time scale of ∼10 h. Ps lifetime spectroscopy revealed two kinds of voids with sizes of ∼0.3 nm and ∼0.9 nm for unmilled saponite before hydration. The intensity of the larger void component in the annihilation spectra decreased from ∼9 % to ∼5 % with increasing time up to ∼100 h and correspondingly the intensity of the smaller void component increased from ∼5 % to ∼9 % due to long-term rheological self-assembly. Both the weight gain and volume expansion were largely suppressed for milled saponite, indicating that the adsorption of H 2 O molecules is reduced. Furthermore, the larger void disappeared and a single void component, corresponding to a void size slightly larger than the original smaller void, was formed for milled saponite. The intensity of this void, created as a result of destruction, decreased with increasing time up to ∼100 h.

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Transient Structural Evolution Upon Thermal Dehydration in Layered-Hectorite Nanoparticles

Cited by 7 publications

References 16 publications

Long-term self-assembly of inorganic layered materials influenced by the local states of the interlayer cations

Long-term self-assembly of inorganic layered materials influenced by the local states of the interlayer cations

Study of reversibility of self-assembly in saponite layered nanoparticles

Study of self-assembly for mechanochemically-milled saponite nanoparticles

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