Dioctahedral 2:1 layer silicates synthesized

Since the end of the nineteenth century, some micas have been synthesized in a fluoride-solid state phase from fluorinated silicates, aluminates, and fluorinated salts such as K2SiF6 (Doelter 1888 Baur 1911 Yoder and Eugster 1955). Due to their properties, such materials have been produced on an industrial scale and are well-studied (Jackel 1952 Roy 1952). Nevertheless, dioctahedral minerals are easier to synthesize than dioctahedrd ones. In 1972, Baroid Division N.L. Corporation produced Barasym SMM 100, a 2 1 dioctahedral layer silicate described as an interstratified mica-beidellite mineral, previously synthesized by Grandquist (Grandquist and Township 1966) and characteri (Wright, Grandquist and Kennedy 1972). 

The syntheses of 2 1 dioctahedral layer silicates have been performed in an acid and fluoride medium. For the samples described in this chapter, the pH of the starting hydrogel ranged from 3.0 to 6.0, and the Si/F molar ratio from 0.65 to 5.00. Five cations were used as interlayer material in these syntheses Li+, Na+, K+, NH4+, and (C2Hs)4NM+, with different results, which were examined farther in this study. 

Figure 10-2 displays the powder XRD spectra of the five samples, as synthesized, and Table 10-3 shows, the X-ray powder diffraction data for the layer silicate phases. These spectra exhibit the charact stic bands (hk) at 4.45-4.47A, at nearly 2.56A, and at 1.49A. The 1.49A band (060) indicates the dioctahedral nature of the layer silicates. Due to the basal reflection, there is also a peak in the low-angle region, the value of which varied with interlayer cation nature and relative humidity (Table 10-4, third and fourth columns). Some samples show other peaks that may be indexed as (001) reflections such as (002), (004) or (006). 

Synthesis and characterization have been investigated in the case of M-dioctahedral 2 1 layer silicates with M = Li, Na, K, NH4 and (C2Hs)4N, and Si and A1 as structure elements. Syntheses were easily performed with Li+, Na+, and NH4+ they were more difficult with K+ and (C2H5)4N+. 

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