Spectra of layer silicates

The analysis of 29Si MAS NMR spectra of layer silicates with a wide range of tetrahedral compositions (Si/Al ratio 2.7-1.7) indicates (483, 486) that the distribution of Si and Al in these materials is indeed determined by (i) the local balance of charges, and (ii) the Loewenstein rule. In muscovite, phlogopite, and vermiculite, aluminum is randomly distributed in... 

Bookin AS, Dainyak LG, Drits VA (1978) Interpretation of the Mossbauer spectra of layer silicates on the basis of stmctirral modeling. Abstr 11th Mtg IntT Mineral Assoc 3 58-59 Bowen LH, Weed SB, Stevens JG (1969) Mossbauer study of micas and their potassirrm-depleted products. Am Mineral 54 72-84... 

Figure 4. XRD spectra of layered silicate (sodium fluorohectorite) reinforced nanocomposites of various compositions.

Farmer, V. C., and J. D. Russell, 1964. The infrared spectra of layer silicates. Spectrochim. Acta 20 1149. Foster, M. D. 1956. Correlation of dioctahedral potassium micas on the basis of their charge relations. U.S. Geol. Survey Bull. 1036-D 57. 

Figure 6. Spectra of layer silicates, using randomly oriented samples in K.Br disks (/ ) and oriented layers at normal incidence (iV). RN indicates spectra independent of orientation. Bands showing perpendicular polarization are indicated by 1. (a) kaolinite (b) nacrite (c) pyrophyllite (d) Skyrve-dalen montmorillonite (e) lepidolite (f) ferric celadonite (g) beidellite (h) rectorite (Farmer and Russell, 1964).

Another method for the intercalation of metalloporphy-rins into clays has been explored using porphyrins and metalloporphyrins as organic templates in the hydrothermal synthesis of layered silicates. X-ray powder-diffraction data indicate that the porphyrins are intercalated parallel to the silicate layers. Microanalysis and UV-visible diffuse-reflectance spectra indicate that the porphyrins are incorporated intact. 

Similarly, pyridinium ions, C5H5NH+, adopt different orientations in the interlayer space of layer silicates, depending on the layer charge of the substrate, as shown by IR and X-ray diffraction results (25,26). Thus, in montmorillonite, pyridinium ions are arranged with their planes parallel to the silicate layers in vermiculite, the plane and C2 axis of the pyridinium ion are essentially perpendicular to the layers. In the latter case, monodimensional X-ray Fourier analysis confirms the orientation obtained from IR spectra (Fig. 4). 

In contrast, the XRD spectra for the nanocomposite fibres recorded only two peaks at 20 position of 2.2 and 4.4°. The disappearance of the third and fourth order peaks (at 6 to 9° region) further suggest exfoliation of layered-silicate during the melt-spinning process. This may be associated with the elongational deformation of the the PP matrix during melt-spuming, which... 

Secondly, because the XRD spectra of PPEX did not show any peak in the compounded feedstock form, its absence in the fibre spectra could not be taken as convincing evidence of layered-silicate exfoliation associated with the melt-spinning. However, given that the HRTEM images of PPEX fibre have manifested layered-silicates of thinner lateral dimension and more uniform dispersion than the injection-moulded PPEX, this would imply the occurrence of exfoliation during the melt-spinning process. 

However, when protonated TEMPAMINE adsorbs by cation exchange on fully hydrated layer silicate clays (10, 11), the spectrum becomes less symmetrical as shown in Figure 5. The beidellite and montmorillonite spectra have line shapes typical for nitroxide molecules with rotational frequencies on the order of 10 Hz (17). 

Cu Adsorbed on Layer Silicates. While the basic principles of ESR used to interpret the nitroxide spectra also apply to Cu +, several significant spectral differences need to be explained. 

In order to obtain satisfactory absorption spectra of the substance under investigation it is essential that the beam pass through a large number of adsorbed monomolecular layers. In practice this is most satisfactorily achieved by adsorption on transparent microporous solids with a high surface area to mass ratio (200-600 m2/g). The solids found most suitable have been silica gel, silicic acid, and microporous glass. 

Goethites Condensation of arginine and glucose at 37 °C C and N fractions yields FTIR spectra of solid residue and supernatant humic substances Clay-Size Layer Silicates Gonzalez and Laird (2004)... 

Chloritoid. Optical spectra of chloritoids, again studied mainly on account of the Fe2+ —> Fe3+ IVCT band at 16,300 cm-1 (Faye et al., 1968 H lenius et al., 1981), also contain features assignable to CF transitions in Fe2+ ions. These cations are located in the M1B positions in brucite layers which are surrounded by four OH" ions and two trans- non-bridging oxygens belonging to isolated [Si04] tetrahedra in silicate layers in the chloritoid structure. The two absorption bands at 10,900 cm-1 and 8,000 cm-1 yield approximate values of A0 = 9,000 cm-1 and CFSE = 4,050 cm-1, respectively, for the Fe2+ ions. 

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