Some kinetic problems of inorganic topochemistry

Rapid Nondiffusional Penetration of Oxide Melts along Grain Boundaries of Oxide Ceramics

“…Estimations show that the kinetic mode of the liquid groove growth, which is limited by the reaction, allows one to obtain deep narrow grooves with a dihedral angle in the vertex of 0 < < at V ≈ 1 cm/min and the V 0 values, which are typical of topochemical reactions and equal to 10 −3 -1 cm/min. 21 It was found that liquid can also interact (according to the mechanism that is proposed in the present work) with the onedimensional defects (dislocations) of solids, penetrating into the bulk of the solids with a high velocity. Figure 4 exhibits the microstructure of a CuO ceramic, where transcrystallite penetration (into the bulk of a grain) of a liquid is observed.…”

“…The activation energy of this process is 87 kJ/mol, which is characteristic of topochemical reactions. 21 This is the reason why relation (2) is also valid in our case for the liquid-channel growth rate, except that now, V 0 is the rate of a reaction proceeding on the flat surface of a solid. Estimations show that the kinetic mode of the liquid groove growth, which is limited by the reaction, allows one to obtain deep narrow grooves with a dihedral angle in the vertex of 0 < < at V ≈ 1 cm/min and the V 0 values, which are typical of topochemical reactions and equal to 10 −3 -1 cm/min.…”

Reactions in solid state: Localized and delocalized

“…Attempts to systematize these and other described [11][12][13] types of intrinsic reactions in solids and to clarify their place in the classification systems of reactions show that the division of chemical transformations of solids into homogeneous (delocalized) and non-homogeneous (localized) is conventional and have to be defined more exactly [5,14,15].…”