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

Abstract

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.

Chemical Trapping of CO2 by Clay Minerals at Reservoir Conditions: Two Mechanisms Observed by in Situ High-Pressure and -Temperature Experiments

“…The peak at 3.6 ppm is diagnostic of the hydrated H 3 O + ion . The peak near 1 ppm is readily assignable to structural OH – of the octahedral sheet . The peak at 5 ppm is probably 1 H background from the probe head and some signal from adsorbed H 2 O.…”

“…57 The peak near 1 ppm is readily assignable to structural OH − of the octahedral sheet. 59 The peak at 5 ppm is probably 1 H background from the probe head and some signal from adsorbed H 2 O. solution with HCO 3 − as the dominant anion. At elevated temperatures, the K a values for these reactions are displaced to lower pH values, but to our knowledge the equilibrium constants are not known at the temperature and pressure used here.…”

“…Ex situ 1 H MAS NMR spectra of unreacted Pb-SHCa-1 (black), Pb-SHCa-1 exposed to scCO 2 at 85% RH at T = 323 K and P fluid = 90 bar in the IR titration experiments for 30 h (red), and the difference spectrum with intensity increased by a factor of ∼3 (blue).The peak at 3.6 ppm is diagnostic of the hydrated H 3 O + ion 57. The peak near 1 ppm is readily assignable to structural OH − of the octahedral sheet 59. The peak at 5 ppm is probably 1 H background from the probe head and some signal from adsorbed H 2 O.…”

Carbon dioxide adsorption in open nanospaces formed by overlap of saponite clay nanosheets

“…This results in the formation of nanoscale open spaces (see Fig. 1b), which have been identified by positronium (Ps) annihilation spectroscopy together with molecular dynamics simulation as is detailed later [15][16][17] . Naturally, there exist local molecular sites in the interior of above open spaces such as nanosheet edges that are chemically active owing to the presence of unpaired electrons at ionically bound octahedron 18 .…”

Instantaneous Ex Situ Mineral Carbonation Relevant to Alkali Metals in Clay Nanoparticles

“…A silicate clay mineral such as saponite has two-dimensional (2D) nanosheets with a variety of sizes, which cannot be perfectly stacked resulting in partial overlapping. The above CO 2 adsorption property originates from the edge sites of 2D nanosheets consisting of tetrahedra and distorted octahedra located in the interior of open nanospace due to their partial overlap. − The O atoms are weakly bound to the octahedral sheet by ionic bonding here, in contrast to the strong semicovalent bonding of O and Si atoms in the tetrahedron. Injected CO 2 gas molecules are physisorbed at the alkali metal cations on the interior surfaces of open spaces by the quadrupole interaction, thereby picking up the O atoms weakly bound to the nanosheet edges.…”