Microstructure kaolinite

Muller, J. Joubert, J.C. (1974) Synthese en milieu hydrothermal et caracterisation de Voxyhydroxyde de vanadium V OOH et d une nouvelle variete allotropic du dioxide VO2. J. Solid State Chem. 11 79—87 Muller, J.P. Bocquier, G. (1986) Dissolution of kaolinites and accumulation of iron oxides in lateritic-ferruginous nodules Mineralogical and microstructural transformations. Geoderma 37 113-136... 

In dilute suspensions clays tend to form gels. The classical model is the house of cards structure of kaolinite in which the face-to-edge association leads to an open 3-D structure (van Olphen, 1965). In the case of smectite-water systems it now seems more likely that the microstructure is mainly controlled by the face-to-face interactions (Van Damme et al., 1985). 

At repeated hydrate formation in the studied soils the amount of hydrate accumulation varies in different ways. During the second cycle of cooling sand samples with kaolinite show a decrease of hydrate accumulation as compared to the first cycle. On the contrary, samples with montmorillonite indicate a trend for an increased hydrate accumulation in the second cycle (Table 2). This behaviour may be explained by a response of the soil microstructure to phase transformations and concomitant changes in the pore space arrangement which is different for soils of different composition... 

The mineral composition of the soil will also influence the kinetics of gas hydrates dissociation in frozen soils. Our results show, that gas hydrate formations in pore space of samples with montmorillonite particles dissociate less markedly as compared to the samples with kaolinite admixture. This influence may be explained by microstructural specificities of pore hydrate saturated samples but undoubtedly requires additional micro-morphological studies for a full understanding. 

Norsy, M.S., Galal, A.F., and Abo-El Enein, S.A. (1998) Effect of temperature on phase composition and microstructure of artificial pozzolana-cement pastes containing burnt kaolinite clay. Cement and Concrete Research 28, 1157-1164. 

The microstructural changes occurring upon con-sohdation were studied for the cases of uniaxial compression in odometer and for the cases of tri-axial isotropic compression in stabilometer on the model systems, i.e., kaolinite and montmorillon-ite powder moistened above the liquid limit and thoroughly mixed up. Samples were compacted according to a standard technique up to the load of 1 MPa. After the end of consohdation, samples were collected for microstructural analyses, and the anisotropy of sample properties was investigated. Simultaneously, the rate of clay-particles order was studied by X-ray method. 

The analysis of sample microstructure proved that the samples compacted in odometer acquired the noticeable direction of particles normal to the applied load direction (Fig. 4a), whereas the samples compressed in stabilometer showed no direction of particles (Fig. 4b). Kaolinite samples manifested the most pronounced structural transformation, which is related to the platy shape and larger size of kaolinite particles as compared to montmorillonite. 

The X-ray study of microstructures showed that the direction rate of kaolinite particles compacted in odometer is equal to 0.88 in the horizontal plane. The same index for particles in the sample compressed in stabilometer turned out to be equal to 0.52, which corresponds to virtually nonoriented structure. 

Coagulation in clay disperse systems and the micro structure of forming clay sediments are mainly controlled by the mineral composition and particle size of sediments. As is seen from Figure 3, the microstructures of Na-form of clay sediments of kaolinite, illite and montmorillonite differ substantially. 

With a change in the composition of exchange cations, the microstructure of kaolinite sediments is practically unchanged (Fig. 4). 

Figure 3. Microstructures of Na+ forms of artificial clays edimetns obtained in distilled water and in neutral medium (a) kaolinite, (b) illite, (c) montmorillonite.

Figure 4. Microstructure of sediment of different cation forms of kaolinite in distilled water (a) Na-i- kaolinite (b) K+ kaolinite, and (c) Ca2+ kaolinite.

Figure 8. Microstructure of artificial Na+ kaolinite sediment obtained (a) in acid medium (pH = 3.5), (b) in alkaline medium (pH = 12), (c) scheme of electrostatic interaction between two particles in the acid medium.

FIGURE 2.12 High -resolution scanning electron microscopy images of (a) Birdwood soil kaolinite finest colloidal fraction and (b) Georgia soil kaolinite finest colloidal fraction. (Reprinted from Journal of Colloid and Interface Science, 339, Zbik and Frost, Microstructure differences in kaolinite suspensions, 110-116. Copyright 2009, with permission from Elsevier.)... 

Morsy, M. S., Abo El-Enein, S. A., and Hanna, G. B., Microstructure and Hydration Characteristics of Artificial Pozzolan Cement Pastes Containing Burnt Kaolinite Clay, Cement Conor. Res., 27 1307-1312 (1997)... 

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