chemia - Studia

SILVIA BORSACCHI, MARCO GEPPI, LUCIA RICCI, ANGELA CARDELLI, GIACOMO RUGGERI
Figure 3. X-Ray diffractograms of Laponite RD, Laponite-2C 18 and Laponite Blue
SEM micrograph highlighted a non-homogeneous distribution of the
particles size in both Laponite RD and Laponite Blue (Figure 4). The surface
of Laponite Blue appears rougher than that of Laponite RD, probably because
of the treatment with 2C 18 and MB.
Figure 4. SEM micrograph of (left) Laponite RD and (right) Laponite Blue
Solid state NMR
In Figure 5 the 29 Si CP-MAS spectra of Laponite Blue, Laponite RD
and Laponite-2C 18 are shown. The most intense peak in all spectra, observed
at -94.7 ppm, arises from Q 3 Si(OMg)(OSi) 3 silicon nuclei of the tetrahedral
sheets, while the small and broad signal centered at about -85 ppm must
be attributed to not fully condensed Q 2 silicon nuclei, mostly present as
Si(OMg)(OSi) 2 (OH) . In the two modified Laponite samples this signal clearly
shows the presence of two components. In a previous work [6], we could
assign the peak at -84.5 ppm to silanols present on the clay platelet edges,
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