MASS SPECTROMETRIC STUDY OF ZIRCONIUM DIBORIDE
UNION CARBIDE RESEARCH INST TARRYTOWN NY
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A mass spectrometer was used with a high temperature Knudsen effusion source to obtain vapor pressure data for zirconium diboride in the temperature range 2267 to 2445 K. The heat of vaporization at 298 K determined from a Third Law analysis of the data is 454.5 5.3 kcalmole. Vapor pressure data from zirconium and boron were also obtained. The Third-Law heats of vaporization are 141.8 3.3 kcal mole for zirconium and 130.3 3.3 kcalmole for boron. The corresponding heat of formation of zirconium diboride at 298 K is -72.1 kcal mole. Separate vapor-pressure measurements made on ZrB2 mixed with C in a graphite crucible gave a value of -74.5 kcalmole.
- Inorganic Chemistry