Low temperature synthesis of cobalt clays

摘要

Clay minerals are an important group of naturally occurring minerals found in soils and sediments. They have a sheet-like structure and the order of the sheets as well as the sheet composition contributed to the properties of the clay mineral. The tetrahedral sheets contain continuous T-O linkages with tetrahedral geometry, where T is normally Si or Al [1]. The apical oxygen of each tetrahedron forms part of the adjacent octahedral sheet, with six coordinated cations surrounded by oxygens and hydroxyls. If the cation is trivalent (eg. Al~(3+), Fe~(3+) then two out of three octahedral positions are occupied and the sheet is classified as dioctahedral. If the cation is divalent (eg. Mg~(2+), Fe~(2+), Ni~(2+), Co~(2+) then all three octahedral positions are occupied and the sheet is classified as trioctahedral. The sheets can stack with one tetrahedral sheet to one octahedral sheet giving 1:1 layers, or with two tetrahedral sheets on both sides of an octahedral sheet giving 2:1 layers. An overall negative charge on the 2:1 layers. An overall negative charge on the 2:1 layers may arise if there is a cation substitution in either the tetrahedral or octahedral position (e.g. substitution of Li~+ or cation vacancies for Me~(2+) in the octahedral position or of Al~(3+) for Si~(4+) in the tetrahedral position. Hydrated interlayer cations are incorporated between the layers to balance the charge.