Accession Number : AD0638140

Title :   THE EFFECT OF HIGH PRESSURE ON CRYSTALLIZATION KINETICS: FUSED SILICA.

Descriptive Note : Technical rept.

Corporate Author : HARVARD UNIV CAMBRIDGE MASS DIV OF ENGINEERING AND APPLIED PHYSICS

Personal Author(s) : Uhlmann,D. R. ; Hays,J. F. ; Turnbull,D.

Report Date : APR 1966

Pagination or Media Count : 39

Abstract : A thermodynamic theory is developed for the effect of pressure on the kinetics of phase transformations. The results suggest that application of pressure may have a profound effect in increasing the rate of crystal nucleation, but that its effect on growth rate should generally be a smaller inhibitory one. Observations on SiO2 carried out in a Bridgman-anvil high pressure device demonstrated the occurrence of crystallization under conditions of temperature and pressure where none had been anticipated from the kinetic formalism. A number of hypotheses are suggested to account for the observations, the most satisfactory of which is based on the effect of water, and the possible existence of a water-rich region at the interface at high pressure, in enhancing the extent of crystallization in a given time. (Author)

Descriptors :   (*SILICON COMPOUNDS, *CRYSTALLIZATION), (*PHASE STUDIES, SILICON COMPOUNDS), HIGH PRESSURE, NUCLEATION, DYNAMICS, GLASS, GELS, DIOXIDES, QUARTZ, WATER

Subject Categories : Geology, Geochemistry and Mineralogy
      Ceramics, Refractories and Glass
      Crystallography
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE