Beryllium vapor pressure studies

The vacuum microbalance can be applied to the study of vapor pressures of metals and in particular to the effect on the vapor pressure of films of oxide, nitride, and other protective layers on the metal surfaces. We studied the vapor pressure of several metals including beryllium and chromium and in this section will discuss the work on beryllium (43). 

Two studies on the vapor pressure of beryllium have been published. The earlier work was by Schuman and Garrett (44) in 1944, and the more recent was reported by Holden, Speiser, and Johnston (45) in 1948. The values given for the vapor pressure P in the two publications differ by about 300%. We were particularly interested in studying the effect of oxide and nitride films on the vapor pressure and the relation of this effect to the rate of oxidation. 

The vapor pressure of beryllium and the effect of oxide and nitride films of various thicknesses were studied, using Langmuir s method. According to Langmuir, the vapor pressure P in atmospheres is related to the rate of evaporation m in grams per square centimeter per second at the absolute temperature T by the formula... 

At room temperature dime thy Ibetyllium forms colorless crystals with very low vapor pressure. An X-ray diffraction study by Snow and Rundle showed the crystal to consist of infinite straight chains of beryllium atoms bridged by methyl groups (Fig. 1). This was the first case in which bridging methyl groups were established by X-ray diffraction ... 

K. A. Sense et al., Vapor Pressure and Equilibrium Studies of the Sodium Fluoride-Beryllium Fluoride System, US.VEC Report BMI-1186, Battelle Memorial Institute, May 27, 1957. 

No Bc2 molecule has been detected in the mass spectra of the vapor above beryllium melts. Any bond between the atoms in Be2 is obviously too weak for the molecule to survive at temperatures above 1300°C. The bond might be strong enough to prevent dissociation at room temperature, but how to produce and study Be2 in the gas phase at this temperature where the vapour pressure above the metal is too low to be measured ... 

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