Correlations interlayer positional

Note 2 A SmF mesophase is characterised by in-plane short-range positional correlations and weak or no interlayer positional correlations. 

Tables IX and X contain correlation coefficients for the oxides and for the ions in their various structural positions. Correlations are relatively limited. There is a negative correlation between MgO and A1203 and between octahedral Mg2+ and octahedral Al3+ as would be expected. The same relation exists between ferric iron and aluminum and potassium and ferric iron. This latter correlation may reflect the fact that Fe3+ is the only major ion that can substitute in the illite structure and not increase the layer charge in fact, the layer charge may decrease (assuming tetrahedral Fe3+ is relatively uncommon). It is also possible that some of this Fe, can occur in the interlayer position. Fig.3 shows the graphical relation of K20 and Fe203.

Since this review was originally completed, Foster (1969) published a review in which similar conclusions are drawn about the glauconites and celadonites. The lack of correlation between iron and potassium content in glauconite is substantiated in her paper. Foster considered the process of glauconitization to be of two separate, unrelated processes, incorporation of iron into the crystal structure and fixation of potassium in interlayer positions, with incorporation of iron and development of negative layer charge preceding complete fixation of potassium . 

Liquid-like layers with the molecules upright on the average (fig. 1.1.5(a)) negligible in-plane and interlayer positional correlations. Thus the structure may be described as an orientationally ordered fluid on which is superimposed a onedimensional density wave. A number of polymorphic types of smectic A have been discovered (see 5.6). 

With an increase in size of the active metals, the interlayer interstitials between the triacontahedral and the penultimate icosidodecahedral shells appear to be occupied by smaller electronegative components, with variable occupancies. These interlayer interstitials are actually the centers of cubes and correspond to the Wyckoff 8c (1/4 V4 A) special position in 1/1 ACs. Strictly speaking, occupation at this site means that the structure is no longer YCd6-type but, for convenience, they are still referred to as Tsai-type phases. According to Piao and coworkers [94], occupation of these cube centers has strong correlation with the orientations of the innermost tetrahedra and distortions of the dodecahedra. 

The negative relation between K2 O and Fe2 03 also occurs in the illites and has been discussed. Fe203 is positively correlated with H20+ and presumably negatively with layer charge. H20+ (greater than 110°C) and H20 (less than 110°C) are inversely related. These correlations suggest some of the H20+ may be trapped interlayer water not easily released (at 110°C) from the clays with a high proportion of contracted layers or that chloritic layers increase as the proportion of expandable layers decrease. 

Table LXVI shows the correlation coefficients obtained for the hard and soft types. The existence of two clay populations limits the meaning of correlations found for the combined data (Hinckley, 1961). In both groups K20 and mica and K20 and Fe203 are positively correlated. In addition, for the soft type there is a positive correlation between Fe203 and mica and negative correlations between mica and books, and Fe203 and books. These interrelations suggest, but do not prove, that books are derived from the mica and that much of the K20 and Fe203 may be present in the mica or that a leaching process that altered the mica and removed its interlayer K20 also removed the iron regardless of where it occurred (pyrite, anatase, iron oxides, etc.).

In addition to the true smectic phases, there is another class of mesophases, formerly also called smectic phases, which do possess extra positional order and which are derived from the true smectics and referred to as crystal smectic phases. These phases are characterized by the appearance of interlayer correlations and, in some cases, by the loss of molecular rotational freedom. Thus, the (crystal) B, G, and J phases are SmB, SmF, and SmI phases, respectively, with interlayer correlations, whereas the E, H, and K phases are B, G, and J phases which have lost rotational freedom (note that, confusingly, there are both smectic and crystal B phases). These phases possess considerable disorder and are, therefore, properly intermediate between the solid and liquid states. 

The main purpose of middle layers is to provide additional (thermal) insulation. Nowadays, these layers are often made of fleece materials with good air entrapment properties. Their thermal conductivity (typically 0.03-0.04 W/mK) is near from air (0.026 W/mK). The thermal resistance of such layers is directly correlated with their thickness, provided that no air movement occurs within the fabric. Thermal conductivity and air permeability also are generally dependent on the fabric density (Yip and Ng, 2008). Conduction has been shown to be the main heat transfer mechanism through textile layers as long as the fibre volume fraction is higher than 9% (Woo et al., 1994). However, materials with very low density (like spacer materials) allow radiant and convective heat transfer. This was demonstrated by Das et al. (2012) who compared a spacer fabric middle layer with two non-woven middle layers and showed that the contribution of this spacer fabric to the overall insulation was higher than the two other samples in a non-convective mode, while it was the lowest in a forced convective mode. The positive effect of metallised interlayers with low emissivity on the reduction of... 

Fig. 3.2 Correlation between the interlayer spacing D12 and the oxygen position Do with respect to the topmost Cu plane (see inset) [46]. The data and references are given in Table 3.3. The symmetry points for O and Cu are —0.01 0.59 and 1.50 0.16 A. The operation of rotating the O-Cu-0 chain around its axis by 180° and shifting the axis from 1.166 (O above) to 1.540 A (O below), transforms point [8] into point [10]. This inverse symmetry of O and Cu position indicates the uncertainty of atomic positions derived from diffraction (reprinted with permission from [76])...

Boden et al. [172] showed that a thermodynamically independent nematic mesophase exists in the cesium perfluorooctanoate (CsPFO)-water system between 37% and 87% (w/w) H2O and 11-75°C. The nematic phase is intermediate to an isotropic micellar solution at higher temperatures and a smectic lamellar mesophase at lower temperatures. The isotropic phase consists of disk-shaped micelles. The lamellar phase has been described by a structure in which continuous lamellae of the surfactant are broken by irregular water-filled defects without interlayer correlations [182]. In the nematic phase, the aggregates make the transition from discrete disks to continuous lamellae [160,182]. Both positional and oriental order increase when the temperature is lowered. The nematic phase of CsPFO-water is stable over a wide range of concentrations without needing a cosurfactant or salt as a stabilizer. The disk-shaped micelles of the nematic phase orient with their unique axis parallel to the direction of an applied magnetic field. 

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