Interlayer free spacing

For AI-PILM, the basal spacing of the sample was evaluated from the dmw diffraction peak and the interlayer free spacing between the clay sheets, which is regarded as indicative... 

Nowadays, the pillaring of clays is a well estabUshed technique in the preparation of new porous soHds. It is an easy and controllable way to introduce porosity in a rather inexpensive substrate. A variety of pillaring species is available, all with specific sizes and compositions. In this way, it is possible to prepare PILCs with different interlayer free spacings which determine the pore size. The interpillar distance can be tuned by varying the charge of both host and pillars. 

The direct intercalation of metal oxide sols (DIMOS) according to Pinnavaia is a good technique to achieve stable oxide pillars [31]. Aqueous oxide sols with uniform particle sizes of 20-80 A can be used to create mesoporous pillared clays. The materials are also called supergallery PILCs, a term covering all substrates with an interlayer distance substantially larger than the thickness of the host layers. Ti-sol prepared from Ti-alkoxides results in Ti-PILCs with interlayer free spacings of 13 A and surface areas of 300 m /g. 

Mixed sols of Si02-Ti02 create interlayer free spacings of 25-35 A. The pore size is, however, not of the same dimension, the spherical sol particles pack irregularly between the layers and form pores of non-uniform size in the micro-porous range. A schematic representation of this mixed supergallery PILC is given in Fig. 3. 

Among them, only the Al-PILC exhibits a narrow pore size distribution [16]. The hydrolysis is the most easy to control, and the pillar dimensions are not very sensitive to differences in the hydrolysis conditions. Interlayer free spacings between 7 and 10 A are always obtained. 

Pillar species Surface area (m /g) Interlayer free spacing (A)... 

TiCl4 or Ti-alkoxides rapidly hydrolyze in HCl and polymerize to a sol which results in large polynuclear species with the formula [TiO(OH)2]n- Broad pore size distributions with a maximum interlayer free spacing of 30 A and surface areas up to 300 mVg have been reported. 

The evaluated minimum thickness of the interlayer was shown in Fig. 2(a). The minimum thickness was evaluated by using the assumption that the oxide formed by the oxidation of the healing agent is filled with the free space between crack walls. A simply model of the fiber... 

The number and exact composition of the sheets is used to classify the phyllosilicates. The most important classification for our purposes is the distinction between 1 1 and 2 1-type minerals (Figure 2.1). In 1 1 minerals such as kaolinite, the basal oxygens of the tetrahedral sheet are free to interact with octahedral OH groups forming hydrogen bonds. In contrast, 2 1 minerals such as pyrophyllite or talc contain two tetrahedral sheets sandwiched around an octahedral sheet. These minerals have only basal oxygens exposed on the faces of the tetrahedral sheets and are linked by weak van der Waals forces. The weaker interaction of one 2 1 layer with a second 2 1 layer results in interlayer spaces which, depending on the particular mineral, may be available for contaminant intercalation. 

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