Dehydroxylation, inhomogeneous

Daw et al. [632] made a microscopic and crystallographic study of talc dehydroxylation. Nucleation, to yield enstatite, occurs inhomogeneously within the particles, perhaps at dislocations. Later, this product is topo-tactically orientated with respect to the reactant lattice, though with extensive faulting on the (010) plane owing to misfit, in addition to the attempt to preserve the oxygen lattice. In an isothermal study (1100— 1160 K) of the same reaction, Ward [633] found first-order obedience and the value of E determined (422 kJ mole-1) is close to that estimated for... 

Daw et al. [61] used microscopy and X-ray diffraction to investigate the dehydroxylation and formation of enstatite during the heating of talc. Dehydration proceeds inhomogeneously with the formation of bubbles, possibly initiated at dislocations. The orientation of the first-formed enstatite was more random than that subsequently attained, in which the product was preferentially aligned in three possible directions with respect to the reactant, controlled by oxygen lattice preservation and cation distribution. 

The interpretation of the dehydroxylation process is consistent with the advancing interface concept rather than the inhomogeneous mechanism since the tunneling of protons explains the reaction of hydroxyl groups in adjacent layers. This mechanism also maintains electroneutrality, so the postulate of Mg2+ countermigration is no longer required. 

Taylor, H. F. W., 1962. Homogeneous and inhomogeneous mechanisms in the dehydroxylation of minerals. Clay Min. Bull. 5 45. 

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