A kinetic and microscopic study has been completed for the gas-solid reaction KBr plus Cl//2 yields KCl plus BrCl to elucidate the mechanism of this nucleation and growth process. The work was concerned with reaction in two temperature intervals, under 400 K and over 450 K: reactivity was negligible in the intervening range (400-450 K). The low temperature reaction (273-320 K in 25 kPa Cl//2) was characterized by long induction periods followed by a strongly acceleratory nucleation process yielding 'half-cube' shaped nuclei which grew at constant rate. Nucleation was catalyzed by SnCl//4. Growth of nuclei ceased and required a second induction period for resumption of growth when reaction was interrupted by evacuation. The red-brown coloration of nuclei is attributed to liquid halogen (Br//2) retention; this was confirmed by titration. Product KCl crystallites were oriented in the KBr (111) direction, shapes of nuclei varied with reaction conditions. From kinetic measurements, and microscopic examinations of interface textures, it is concluded that reaction occurs within a thin zone (of around 10 mu m) at the nucleus periphery, the chemical change proceeding between participants dissolved in liquid halogen.
|Number of pages||24|
|Journal||Philosophical Transactions of the Royal Society of London (Series) A: Mathematical and Physical Sc|
|Publication status||Published - Jan 1 1984|
ASJC Scopus subject areas
- Physics and Astronomy(all)