Abstract
Theoretical research and specific surface area analysis of nitrogen adsorption indicated that a lot of structural micropores exist in sepiolite minerals fibers. However, the microporous size, existing form, and the distribution relationship between microporous structures were not proved yet. In this paper, the section TEM samples of nanofibers were prepared on the basis of the metal embedding and cutting technique, and the inner structure of sepiolite nanofibers was observed by TEM. The results showed that sepiolite fibers have multiplayer structure similar to concentric circles, and many micropores with the size of about 2–5 nm are normal and parallel to thec-axis. The reason for the previously mentioned phenomenon was explained by using BET analysis and X-ray diffraction analysis results.
Highlights
Sepiolite is a kind of fibrous silicate clay mineral rich of magnesium with a structure of layer and chain
The results showed that sepiolite fibers have multiplayer structure similar to concentric circles, and many micropores with the size of about 2–5 nm are normal and parallel to the c-axis
The inner structure of sepiolite nanofibers was observed by TEM in order to study the forms of existence Journal of Nanomaterials a b b a and rules of distribution in sepiolite minerals fibers, which were further explained by using BET analysis and X-ray diffraction analysis results
Summary
Sepiolite is a kind of fibrous silicate clay mineral rich of magnesium with a structure of layer and chain. Nagy believed that sepiolite crystal was amphibole chain composed of two pyroxene chains, with silicon-oxy tetrahedron on each side in standard spacing. According to Brauner’s model, the theoretical structure of sepiolite was Si12Mg8O30(OH)4(OH2)4·8H2O, whose fibrous structures were composed of two layers of silicon-oxy tetrahedron units connected by oxygen atoms and central magnesium octahedron layers. Silicon-oxy tetrahedron layers were continuous, and were inverted at intervals of six tetrahedron units, leading to the existence of channels of dimensions of 0.37 nm × 1.06 nm running parallel to the length of the fibers. The two models mentioned previously were not different obviously in terms of the sizes of crystal, but they had eight and nine of octahedron cations in Brauner’s and Nagy’s model, separately. Rules of distribution in sepiolite minerals fibers, which were further explained by using BET analysis and X-ray diffraction analysis results
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