Development and application of very high temperature
mass spectrometry. Vapor pressure determinations over liquid refractories*
J. W. Hastie**, D. W. Bonnell, and P. K. Schenck
National Institute of Standards and Technology (NIST),
Gaithersburg, Maryland 20899-8522, USA
Abstract: Existing thermodynamic and vaporization data for liquid
refractories are based either on estimates or on data extrapolated from
studies on the solids obtained at much lower temperatures. Previously,
we have shown that pulsed laser heating, coupled with time-dependent
mass spectrometry of the free-expansion vapor plume, can be used for
semi-quantitative measurements of vaporization thermochemistry. The
present work extends this approach with the development of (a) more
direct, and more accurate, methods for determining the system temperature
and pressure; (b) improved experimental and theoretical determinations
of key parameters such as ionization cross sections; and (c) improved
characterization of the gas dynamic expansion and thermal equilibration
processes. Example material systems considered include C, SiC, Al2O3,
ZrO27%Y2O3, and Y2O3
at temperatures and total pressures typically in the range of 3000 to
5000 K and 0.01 to 10 bar, respectively (1 bar = 105 Nm-2).
*Lectures from the 10th International Conference
on High Temperature Materials Chemistry (HTMC-X), Jülich, Germany,
10-14 April 2000. Other presentations are published in this issue, pp.
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