Clays lamellae

A possible explanation is that access of O2 to the exchange or Fe(OH)3 sites where the Fe + is adsorbed is restricted. Possibly Fe(OH)3 is precipitated between clay lamellae at the oxidation sites and it partially blocks the original exchange sites. This mechanism would also imply a wide range of reaction rates between soils, with ks values ranging by perhaps an order of magnitude, as in Figure 4.15. 

Fig. 10 Structure of cationic MPPBT molecule and schematics of the 2D confinement between clay lamellas (courtesy of Dr. K. Kamada)...

Tombacz, E. et al.. Surface charge heterogeneity and aggregation of clay lamellae in aqueous suspensions. Prog. Colloid Polym. Sci., 125, 206, 2004. 

Intercalation of Monomers/Polymers into the Clay Lamellae. 175... 

Conventional composites in conventional composites, the clay tactoids exist in their original aggregated states with no intercalation of the polymer matrix into the clay lamellae. 

The structure investigation of Pd-HDAM samples revealed that the orientation of the clay lamellae was substantially modified via formation of internal Pd particles. However, the occurrence of regular intercalation was found to be unlikely [10]. Therefore, we propose that the particles occupy defect sites of montmorillonite, similarly to a model introduced by Giannelis et al [11]. 

The hydrogenation of 1-octene was studied in toluene. According to XRD measurements, toluene provides a considerable expansion of the clay lamellae (dL = 4.07 nm), which opens access for reactant molecules to interlayer active sites. As a result, the reaction of 1-octene may take place in the interlamellar space of Pd-HDAM samples. 

In a poor solvent (cyclohexane), the clay lamella packages form aggregates due to adhesion of the secondary particles (a card house structure is formed). Furthermore, the value of dt is very close to the thickness of the silicate layer plus the cross sections of two alkyl chains. It follows that in a poor solvent, the alkyl chains are laying flat on the surface and no swelling takes place. In that case, the interstitial sites are not available for reactants and reaction proceeds on the external surface sites. 

In a good solvent (toluene, ethanol, or tetrahydrofurane), the clay particles undergo desaggregation and swelling. The distance between the clay lamellae increases and the alkyl chains are lifted away from the basal planes. As a result, the reactants can penetrate the interlamellar space and interlayer reaction may occur [14],... 

Despite aggregation and compactness of clay lamellae in cyclohexane, the interlamellar space is not completely inaccessible, as styrene, even at small concentrations, may induce swelling. However, the hydrogenation rate may be limited by transport phenomena and diffusion control may develop. It is established that dL > 3 nm represents a sufficiently large distance between the clay lamellae for the reactants to enter the interlayer space and undergo hydrogenation there. 

Coagulation structures form when disperse system undergoes aggregation if there is a sufficient amount of dispersed phase, armoring of the entire volume of disperse system takes place. The amount of dispersed phase that is needed to solidify liquid dispersion medium may sometimes be very small, especially if the system contains very fine and anisotropic particles this may be only 6% by weight in the case of bentonite clay lamella suspension, and even less for a suspension of thread-like particles of V205. 

Depending on the nature of the components used (layered silicate, organic cation, and polymer matrix) and the preparation method, three types of hybrid PCNs can be obtained [17]. Phase-separated microcomposites (conventional composites) are obtained when the polymer chains are unable to intercalate within the inorganic sheets clay lamellae remain stacked in structures marked as tactoids as in the pristine mineral. Otherwise, when the polymer chains penetrate in between the clay galleries, an intercalative system is obtained. In this case, the nanocomposite shows, at least in principle, a well-ordered multilayer morphology built up with alternating polymeric and clay layers. When clay platelets are randomly dispersed in the polymer matrix and the lamellae are far apart from each other, so that the periodicity of this platelet arrangement is totally lost, an exfoliated structure is achieved. 

Surface charge heterogeneity and assregation of clay lamellae in aqueous suspensions... 

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