Silicon-aluminum ratio aluminosilicate

The ratio of silicon, aluminum, and oxygen (Si Al 0) at the very surface of the exposed nylon 6 nanocomposite is 22.96% 9.14% 60.2%, which is 2.5 1 6.5. This ratio corresponds well to that generally anticipated for low-magnesium montmorillonite (2.3 1 6.8, (Ai3.5Mgo.5)Si802o(OH)4 (5)). This further indicates a thin layer of aluminosilicate covers the surface of the oxygen plasma treated nanocomposite film. 

Two adjacent aluminum tetrahedra, sharing a corner, contribute two bonds of strength f to the shared oxygen atom. The total of (which might be increased by a small amount by bonds from alkali or alkaline-earth ions) represents a deviation from the electrostatic valence rule such that in general in aluminosilicates of the tetrahedral framework type the Al/Si ratio does not exceed 1, and when it equals 1 there is good ordering, with alternation of the aluminum and silicon tetrahedra. 

The acidic destruction of montmorillonite results in the release of silicon and aluminum. The initial fast exchange of surface cations by hydrogen ions is followed by the release of aluminum and silicon. The dissolution rate of Si is higher than that of A1 and is influenced by the relative ratios of basal siloxane and edge surfaces. The shift of pH to more basic values by the ion-exchange processes and the hydrolysis of dissolved species induce the formation of secondary amorphous solids, initiating the formation of amorphous aluminosilicates (Sondi et al. 2008). 

As described above for the amorphous aluminosilicates the acid strength of a zeolite increases with increasing Si Al ratios. Species with particularly high ratios have been prepared by removing some of the aluminum by reaction with materials such as silicon tetrachloride. On the other hand, the basic character of these materials increases with increasing numbers of A104 species so aluminum-rich zeolites are better bases, particularly when the Na" " is replaced with a large cation such as Cs. 52... 

The relative amount of surface A1 wrt. Si increases very markedly when cum-mingtonite is treated with cells as compared to a firesh sample or one that is placed only in a medium. The Si/A1 ratio can decrease in two ways—either Al+ ions are released from the tetrahedral and octahedral lattices and drawn to the cell/silicate interface in the presence of cells, or the reverse happens to the silicon. On the other hand, no aluminum was detected either in the medium or in the cells after contact with the aluminosilicate. During cell/silicate interaction there is also a definite increase in the concentration of Fe on the surface and a slight increase in the level of Mg. 

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