Advances in the mass spectrometric study of the laser vaporization of graphite

Abstract

Reliable experimental data on graphite vaporization and especially on carbon vapor composition exist only up to 2500–3000 K. Data measured at higher temperatures are questionable due to several experimental limitations, such as the difficult temperature determination and the not straightforward correlation of measured temperatures and intensities of signals in mass spectra. That is why a new method of high-temperature mass spectrometry with laser vaporization was developed, in order to extend the accessible temperature range while overcoming these limitations and to shed more light on the still poorly known behavior of carbon at high temperatures. Thus, carbon sublimation relative partial pressures of the species C1, C2, C3, C4, and C5 were measured up to 4100 K. Moreover, the values of the relative vaporization coefficients of C1, C2, C3, C4, and C5, estimated by comparison of the experimentally obtained partial pressures with the predicted equilibrium ones, are proposed.

Investigations of SP-AMS Carbon Ion Distributions as a Function of Refractory Black Carbon Particle Type

“…Several previous laser-assisted studies have reported the mass spectrometric detection of fullerene ions from rBC materials (Rohlfing et al 1984;Spencer et al 2008;Maricq 2009), and high laser power densities (>10 8 W/cm 2 ) have been shown to produce fullerene ions as artifacts of the vaporization process (Buseck 2002). In contrast, low laser power densities (10 3 -10 5 W/cm 2 ) have been shown to be less prone to generate species not originally present and yield carbon cluster distributions similar to thermal desorption results, indicating the minimal influence of laser power density on the resulting carbon clusters, including fullerenes (Buseck et al 1992;Wilson et al 1993;Pflieger et al 2008). …”

“…Previous work has shown that neutral C 1 -C 5 carbon clusters represent the main vapor components from heated graphitic carbon materials (Pflieger et al 2008) and the most stable geometries of these clusters are linear (von Helden et al 1993). The positive and negative ion mass spectra for Regal black show that the measured carbon ion fraction in the low carbon category (C 1 C -C 5 C or C 2 ¡ -C 10 ¡ ) is more than 99%.…”

“…The laser energy deposited into a single rBC particle is estimated to be »1 nJ (or »1 erg/pg), assuming a typical rBC particle mass of »6 fg (volume equivalent diameter of 200 nm and effective density of 1.4 g/cm 3 ) (Schwarz et al 2006). Previous studies suggest that this energy density is below the threshold for plasma formation from black carbon materials (Buseck et al 1992;Gamaly et al 1999;Pflieger et al 2008), although the particles' temperature increase and heating rates may induce partial annealing (Vander Wal and Choi 1999).…”

“…Laser vaporization mass spectrometry was employed to study carbon clusters (i.e., pure carbon molecules) in supersonic beams, specifically for clusters with greater than four carbon atoms (Rohlfing et al 1984;Pflieger et al 2008). Such studies led to the discovery of buckminsterfullerene (C 60 ) and the classification of fullerenes, in general, as a carbon allotrope (Kroto et al 1985;.…”

“…High-resolution transmission electron microscopy (HR-TEM) studies have shown partial annealing of BC particles due to heat treatment via pulsed laser light (e.g., laser-induced incandescence techniques), even for extremely rapid (greater than 10 9 K/s) heating and cooling rates and total times at elevated temperatures of the order of microseconds (Vander Wal and Jensen 1998;Vander Wal and Choi 1999). A subgroup of these studies focused on vaporizing carbon using laser beams with light intensities below the threshold for plasma formation to investigate the thermodynamic parameters of vaporized carbon clusters or the presence of fullerenes (Buseck et al 1992;Wilson et al 1993;Pflieger et al 2008).…”