Laser-heated microfurnace: gas analysis & graphite morphology
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Date
2009-06-04
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Publisher
Cambridge University Press
Abstract
preparing ultra-small graphite samples from CO2 at the ~5 μg of carbon level (Smith et al. 2006, 2007, 2008). Recent effort has focused on automation using a LABview interface, which has permitted feedback control of the catalyst temperature as the reaction proceeds and logging of reaction parameters. Additionally, an automatic system has been developed to control the temperature of the cold finger for trapping CO2 (–196°C), trapping H2O (–80°C) and releasing these gases (25°C) during sample transfer and during the reaction. We have utilized a quadrupole mass spectrometer to study the gas composition during the reaction, in order to better understand the underlying chemical reactions for such small samples and to better estimate the overall efficiency of the process. Early results show that all CO2 is converted to CO by reduction on the iron catalyst within a few minutes of applying laser power. The reaction pressure stabilizes after ~20 minutes; however, some CO is not converted to graphite. The cold trap temperature of –80°C is effective at trapping H2O so there is little CH4 production. We have trialled a number of different iron catalysts (Cerac -325, Sigma Aldrich -400 and 25 nm Fe nanopowder) as well as Fe2O3 (reduced in situ to Fe) and have studied the graphite morphology by scanning electron microscopy (SEM). There is a marked difference in morphology with catalyst type; however, each graphite performs well in the cesium sputter ion source of the ANTARES AMS facility. These developments allow us to systematically optimize the performance of the apparatus and to develop a second generation device.
Description
Keywords
Graphite, Carbon, Gas analysis, Morphology, Furnaces, Laser-radiation heating
Citation
Smith, A. M., Yang, B., Hua, Q., & Mann, M. (2009). Laser-heated microfurnace: gas analysis & graphite morphology. Presentation to the 20th International Radiocarbon Conference, 31st May - 5th June 2009. Big Island, Hawaii: Kailua-Kona. In Radiocarbon, 52(2), 769-782. doi:10.1017/S0033822200045781