Crystal structure of kanemite, NaHSi₂O₅.3H₂O, from the Aris Phonolite, Namibia

Formation of Novel Ordered Mesoporous Silicas with Square Channels and Their Direct Observation by Transmission Electron Microscopy

“…18 regularly with interlayer hydrated Na ions. [13,14] Following the report on the synthesis and reactivity of kanemite by Beneke and Lagaly, [15] Yanagisawa et al discovered a mesoporous silica (named as KSW-1 hereafter) by the reaction of kanemite and C n TMA surfactants. [1] A mesostructured precursor of KSW-2 was obtained from a layered C 16 TMA ± kanemite complex by adjusting the pH value below 6.0.…”

“…The spectrum of kanemite exhibited only one peak at d À 97, indicating that kanemite is composed of single-layered silicate sheets (Figure 3 a). [13,14] In the spectrum of the layered C 16 TMA ± kanemite complex several peaks due to different Q 3 environments ((SiO) 3 SiO) were mainly observed in the range from d À 95 to À 105, [12] whereas a broad peak centered at d À 110 due to a Q 4 environment ((SiO) 3 SiOSi) was detected as a minor component (Figure 3 b). This result reveals that the single silicate sheet structure in kanemite was essentially retained during the synthesis of the layered C 16 TMA ± kanemite complex.…”

Layered Sodium Disilicates as Precursors of Mesoporous Silicas. Part II: Hydration of δ-Na2Si2O5 and α-Na2Si2O5

“…The first option seems less likely in view of the fact that the phase transformation occurs in very mild conditions at room temperature. Additionally, according to Kahlenberg et al (1999), the SiO 4 tetrahedra in the d phase display higher strain than the structural units in a-Na 2 Si 2 O 5 , nevertheless in kanemite the character of the layer folding is preserved (Garvie et al 1999). For this reason we suggest that it is the different packing of the interlayer cations and water that is responsible for the lower value of basal spacing in hydrated a-Na 2 Si 2 O 5 .…”

“…However, analysis of the d values associated with the first low angle reflections observed for the hydrated a phase and for kanemite leads to some interesting observations. In kanemite, the first low angle reflection at d = 1.03 nm is the most intensive one and corresponds to the basal d spacing of the layered structure (Garvie et al 1999). It seems reasonable to assume that the most intensive low angle reflection in the pattern of hydrated a-Na 2 Si 2 O 5 corresponds also to the basal d spacing.…”

Reactivity and applications of layered silicates and layered double hydroxides

“…2a). [18][19][20] The local structures and dynamics of interlayer Na cations and water have also been studied by solid-state 1 H-, 29 Si-and 23 Na-NMR. 21 The interlayer water is present in two different states (bound as well as free) in kanemite, as revealed by quasi-elastic neutron scattering (QENS), thermogravimetry (TG) and 2 H-NMR measurements.…”