Thermochemistry of Materials by Laser Vaporization Mass Spectrometry, Part 2 - Graphite

摘要

In an earlier study (Part I of this series) an experimental approach which couples laser heating of refractory materials under vacuum with mass spectrometric detection of the vapor plume, for thermochemical determinations, of 2900 K was demonstrated using the BN refractory system at 2900 K. The paper describes the results of a similar study on graphite at temperatures around 4100 K and total species pressures in the vicinity of an atmosphere (1 atm = 1.01325 x 10 to the 5th power Nm-2). A Nd/YAG laser system, focused to power densities in the range of 10 to the 9th power - 10 to the 10th power W/sq. cm., was found to be a convenient energy source for producing controlled vapor plumes and with negligible post-vaporization perturbation of the neutral species identity and concentration. The principal vapor species were found to be Cn (n = 1 - 9) and their relative intensities were found to be more consistent with the JANAF Thermochemical Tables than more recent literature assessments and results.