Crystal Growth Kinetics of Boron Oxide Under Pressure

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Crystal Growth Kinetics of Boron Oxide Under Pressure

Show simple item record Turnbull, David Hays, James F. Nygren, Eric Aziz, Michael 2010-02-17T19:11:54Z 1985
dc.identifier.citation Aziz, Michael J., Eric Nygren, James F. Hays, and David Turnbull. 1985. Crystal growth kinetics of boron oxide under pressure. Journal of Applied Physics 57 (6): 2233-2242. en_US
dc.identifier.issn 0021-8979 en_US
dc.description.abstract We have measured the crystal growth rate u of B2O3-I in the amorphous phase, as it varied over five orders of magnitude with changes in temperature and pressure. We eliminated the crystal nucleation barrier by seeding the surface of boron oxide glass with crystals. u became measurable only when the pressure exceeded a threshold level near 10 kbar. Using the published thermodynamic information on the B2O3 system and a crude free-energy model for the crystal and glass phases, we account qualitatively for our results with the theory of crystal growth limited by the rate of two-dimensional nucleation of monolayers. The constants for the prefactor, activation energy, activation volume, and ledge tension are determined by fitting. By adjusting the thermodynamic parameters to a set of values that are well within the ranges delineated by their experimental uncertainties, we account quantitatively for the measured growth rates from 300 to 500 °C and from 0 to 30 kbar with the following relation: u(T,P)=(785 m/s)[||DeltaGm||/(RT)]1/6 ×exp[pi×3 Å(420 erg/cm2)2(28 cm3/mole)/(3 kTDeltaGm)]exp[−10 366 cal/mole/(RT)] ×exp[−P×16 cm3/mole/(RT)]×{1−exp[DeltaGm/(RT)]}2/3, with the driving free energy given by DeltaGm(T,P)=(13 cm3/mole) [PM(T)−P] and the melting curve given by PM(T)=(T−450 °C)/(42.6 K/kbar). The "B2O3 crystallization anomaly", that crystals have never been observed to grow at atmospheric pressure, is explained, since according to our model, the frequency of two-dimensional nucleation is negligible at all temperatures at pressures less than 10 kbar en_US
dc.description.sponsorship Engineering and Applied Sciences en_US
dc.language.iso en_US en_US
dc.publisher American Institute of Physics en_US
dc.relation.isversionof en_US
dash.license LAA
dc.subject glass en_US
dc.subject high temperature en_US
dc.subject melting en_US
dc.subject very high pressure en_US
dc.subject kinetics en_US
dc.subject crystal growth from melts en_US
dc.subject crystallization en_US
dc.subject free energy en_US
dc.subject thermodynamic properties en_US
dc.subject monolayers en_US
dc.subject phase transformations en_US
dc.subject crystal- en_US
dc.subject nucleation en_US
dc.subject activation energy en_US
dc.subject pressure effects en_US
dc.subject temperature effects en_US
dc.subject boron oxides en_US
dc.subject amorphous state en_US
dc.title Crystal Growth Kinetics of Boron Oxide Under Pressure en_US
dc.type Journal Article en_US
dc.description.version Version of Record en_US
dc.relation.journal Journal of Applied Physics en_US Aziz, Michael 2010-02-17T19:11:54Z

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