Morphology of fine particles of sodium chloride-potassium chloride system prepared by gas-evaporation technique

Abstract

The crystal structure and habit of fine particles of the NaCl-KCl system prepared by gas-evaporation technique were investigated by electron microscopy. No single phase particles of NaCl or KCl were found. Most of the particles were composed of two blocks of NaCl and KCl. Except for NaCl-rich particles, the KCl block showed the crystal habit of a regular cube or a rectangular parallelepiped and penetrated into the NaCl block with a parallel orientation, the external surfaces of both blocks being {100}. A hammer-shaped habit, in which the parts corresponding to the hammer head and handle were a NaCl block and a KCl block, respectively, was also observed. The growth of the two-block composites is discussed in relation to the process of separation into the two phases. Fine particles composed of many blocks of NaCl and KCl with a parallel orientation, where the size of each block is less than 50 nm, were also observed.