Synthesis and Structure of Valleriite, a Layered Metal Hydroxide/Sulfide Composite

An experimental study on the hydrothermal preparation of tochilinite nanotubes and tochilinite–serpentine-intergrowth nanotubes from metal particles

“…4a and b) (from run No. 177 and 366 of Table A2), like those reported in the works of Hughes et al (1993) and Kakos et al (1994). The average lattice parameters of these nanotubes are: the sulfide layer a S = b S = 3.6-3.8 Å , and the hydroxide layer a H = b H = 3.0-3.1 Å , and c = 10.6-11.1 Å .…”

“…4 shows representative ED patterns of FeMgAl tochilinite nanotubes and flakes. The main feature of these ED patterns is that almost all the ED patterns are composed of two sets of diffractions: one sharp and strong (probably originating from the sulfide layers of FeMgAl tochilinite) and the other weak and diffuse (probably produced from the hydroxide layers; Organova et al, 1974;Hughes et al, 1993;Kakos et al, 1994). Rotational twinning is also common for both the sulfide and the hydroxide layers.…”

“…The valleriite-like ED patterns have a common characteristic, i.e. the dispersive diffraction spots or streaks originating from the sulfide and the hydroxide layers almost always tend to appear in pairs, which might indicate relatively strong interactions between structural units (or nanocrystalline islands) of the sulfide and the hydroxide layers (Hughes et al, 1993;Kakos et al, 1994). This kind of structural feature may be the reason that some FeMgAl tochilinite crystallites can contain tetrahedrally coordinated Si 4+ as a component (analyses b and d in Table 1), even though normally Si 4+ cannot exist in the octahedrally coordinated hydroxide layer of tochilinite (Organova et al, 1974).…”

“…The mineral valleriite has a similar structure to tochilinite (Organova et al, 1974). Evans and Allmann (1968) and Hughes et al (1993) postulate that the hydroxide layer in valleriite possesses positive charges and the sulfide layer contains (delocalized) negative charges. We think that this scenario may also apply to the structure of tochilinite.…”

An experimental study on the preparation of tochilinite-originated intercalation compounds comprised of Fe1−xS host layers and various kinds of guest layers

“…The highly changeable hydroxide layer of tochilinite suggests that the tochilinite structure possesses some characteristics of ionic crystals or polar molecules. A similar suggestion has been put forward by Qin et al (1996) for the mineral valleriite, which has a similar structure to tochilinite (Organova et al, 1974;Hughes et al, 1993). Thus, the interaction between the sulfide layers and the hydroxide layers of tochilinite is at least partly ionic.…”