Kaolinite basal spacing

The least compHcated clay minerals are the 1 1 clay minerals composed of one tetrahedral (T) layer and one octahedral (O) layer (see Fig. 1). These 1 1 clay minerals are also referred to as TO minerals. The TO package has a basal spacing (nominal thickness) of 0.7 nm (7 E) and they are commonly referred to as 7 E minerals. Kaolinite, the dioctahedral 1 1 mineral, has filling two of three octahedral sites, and serpentine [12168-92-2J, (Mg)3Si205(0H)4, the trioctahedral 1 1 mineral has filling all three octahedral sites. The kaolin minerals have limited substitution in the octahedral... 

Clay groups (phyllosilicates) in shale are characterized by different basal spacings in X-ray diffraction tests using glycerol-treated oriented clay specimens K=Kaolinite (7.2 A), I=Illite (9.9 A), C=Chlorite (14 A), V=Vermiculite (14.8 A), and S=Smectite (17 A) are the common families. 

Disaggregation of kaolinite in DMSO can be conveniently monitored by XRD (Fig. 2). The kaolinite lamellae open up and the original basal spacing of di = 0J2mn increases to 1.12 nm as a result of the intercalation of DMSO (Fig. 2). 

Table 2 Basal spacing and particle size of palladium/ kaolinite samples...

Noble metal/kaolinite composites were prepared in aqueous dispersions. The particles formed were stabilized with polymers and the lamellae of clay minerals. Silver nanoparticles were prepared on disaggregated kaolinite. It was proven by the change in basal spacing of kaolinite that a fraction of the nanoparticles was formed in the interlamellar space. However, the particle sizes obtained by TEM show that larger particles were also generated and that these are located on the external surfaces and on the edges. Both TEM and XRD measurements show that the average size of the silver... 

The distinction between kaolinite and halloysite can be difficult. Even when techniques of X-ray diffraction, differential thermal analysis, electron microscopy, and chemical treatments are combined, the result may still be doubtful. If hydrated halloysite is present, it can be detected by a basal spacing of 7.3 A or larger, which shifts to smaller spacings when the sample... 

Interlamellar distances in the liquid crystalline mesophase and basal spacing in montmorillonite and kaolinite were determined by X-ray diffraction measurements in a Philips PW-1830 diffractometer (CuKa radiation, A = 0.154... 

To produce Pd nanocrystals in kaoUnite it is necessary to open the interlamellar space for the synthesis of nanoparticles i.e., the hydrogen bonds between the kaolinite lamellae must be broken. A schematic diagram of the synthesis is presented in Fig. 12. Disaggregation was nearly 100% complete after the formation of the DMSO/kaolinite intercalation complex. Changes in the basal spacing of kaolinite studied by X-ray diffraction measurements... 

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. 

The position of the intercalated DMSO molecule in the interlayer space of kaolinite is such that the first S-C group is almost parallel with the surface of kaolinite and the second S-C group is directed into the tetrahedral cavity of kaolinite [130, 131]. The S=0 group has 40.3° inclination to the basal surface of kaolinite. The methyl group of DMSO is influenced by both the opposing mineral surfaces. In addition, the intercalation of DMSO molecule results in the expansion of kaolinite from 7.2 to 11.19 A phase [132]. The formation of H-bonds between DMSO and surface OH groups of the octahedral side and weak H-bonds with the tetrahedral side of kaolinite was suggested [133-139]. 

The best-known example of a 1 1 (two-sheet) type clay is kaolinite. A pictorial impression of the ideal kaolinite structure is given in Figure 11.1. The upper and lower basal surfaces of the two-sheet layer are clearly quite different. The layer repeat distance, or c-spacing, is c. 0.72 nm, which is the distance between atom centres in two contiguous layers. This is approximately the same as the sum of the atomic radii and therefore in an ideal structure there is insufficient space to accommodate any interlayer material such as intercalated water. 

These give (02, 11), (13, 20), and (06, 33) reflections. The latter is a doublet, 1.49 and 1.50 A, corresponding to kaolinite and montmorillonite. Basal reflections are almost absent, but a broad band occurs in the region 5 to 12° 20, i.e., 7 to 15 A spacings. There also exist two broad bands at 3 to 5 A and 2 to 5 A approximating to 002 and 003 kaolinite. Heat treatment at 500°C weakens all reflections, as does ethylene glycol treatment even the (02,11) and (13, 20) reflections become broad, like one-dimensional crystal reflections (Figure 29). 

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