Thesis

Studies of the growth kinetics and habit modification of sodium chlorate crystals

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Awarding institution
  • University of Strathclyde
Date of award
  • 1989
Thesis identifier
  • T6462
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Department, School or Faculty
Abstract
  • The thesis describes the results of studies on the morphology, growth kinetics and defect structure of sodium chlorate crystals grown from aqueous solutions at temperatures near the ambient. For the investigation of the growth morphology and habit modification of the crystals as a function of supersaturation and concentration of Na₂S₂0₆·2H₂0 impurity, experimental data on the morphological importance of different faces were supplemented by examination of the surface topography, the dislocation structure land changes in the lattice parameter of the crystals. The results showed that the habit of the crystals grown from pure solutions is cubic at high supersaturations, while it is cuboid with relatively small {110} and {111} faces at low supersaturations. Optical examination of the as-grown surfaces did not reveal the presence of growth spirals or hillocks, but screw, edge and mixed dislocations were identified by Lang topography at both low and high values of supersaturations (undercooling). Addition of the impurity to the growth solution led to the development of tetrahedral faces with randomly situated hillocks of different sizes at the expense of cubic faces, and to an increase in the lattice parameter of the grown crystals. The influence of the impurity was also studied on the nucleation kinetics of the compound. Effects of applied supersaturation on the regeneration process at the seed and the dislocation structure at the seed-crystal interface, and of the strain, applied externally on large crystals and inherently present in small crystals of dimensions 50 - 150 µm, on growth rates were investigated by using X-ray diffraction topography. It was found that the strain generated at the newly-grown interface and the numerical density of dislocations formed therefrom increase with the value of the supersaturation used for the refacetting process. It was unequivocally established that the growth rates of crystals decrease with an increase in the strain applied externally on large crystals and inherently present in small crystals.
Resource Type
DOI
EThOS ID
  • uk.bl.ethos.500676
Date Created
  • 1989
Former identifier
  • 478284

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