Mass-Spectrometric Studies of Graphite Vaporization at High Temperatures.
Interim technical rept. 1 Jul 68-30 Jun 69,
MIDWEST RESEARCH INST KANSAS CITY MO
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In connection with a goal to extend the thermodynamics and kinetics of carbon vaporization toward the one atmosphere regime, the authors review, briefly, related work currently under way in several laboratories. The authors first years research is then described in terms of prospective sources of carbon vapor, the problems of cold-probe sampling of hot gases and the important continuum sampling effects of mass separation and nucleation. Studies of cold-probe, hot-gas interaction were carried out using the Bendix TOF direct sampling system. With flames at about 2500 2500K time-of-flight velocity analysis indicated the possibility of serious cooling by heat exchange to the cold orifice. Better controlled experiments at 1000, using rare gases heated in a furnace flow system, gave no definite indication that sampling was not adiabatic. Considerations of free-jet expansion behavior serve to allow estimates of the conditions of carbon vaporization at which continuum effects may become important. Continuum effects could be quite significant in laser evaporation and in free evaporation from large surfaces about 1 in. above 3000K. A new, high pumping speed, 3-stage differentially pumped, modulated beam, direct sampling system is described. Beams are detected by a Nuclide mass spectrometer with several data acquisition options. Author
- Atomic and Molecular Physics and Spectroscopy