Atmospheric carbon

Just recently (Wilde et al. 2000), half a century after the indirect demonstration, it has at last become possible to see carbon atmospheres around dislocations in steel directly, by means of atom-probe imaging (see Section 6.2.4). The maximum carbon concentration in such atmospheres was estimated at 8 2 at.% of carbon. 

Proceedings of the Symposium on Particulate Carbon Atmospheric Life Cycle. Wolff, G.T. Klimisch, R.L., Eds.,... 

Chang, S. G., R. Brodzinsky, L. A. Gundel, and T. Novakov, Chemical and Catalytic Properties of Elemental Carbon, in Particulate Carbon Atmospheric Life Cycle (G. T. Wolff and R. L. Klimsch, Eds.), pp. 159-181, Plenum, New York, 1982. 

Wolff, G. T and R. L. Klimisch, Eds., Particulate Carbon Atmospheric Life Cycle, Plenum, New York, 1982. 

Samples of catalysts B and C were investigated using Transmission Electron Microscopy coupled with Energy Dispersive X-ray Analysis (TEM/EDX). This technique makes it possible to gather elemental data from discreet areas of the catalyst and allows comparison between the nickel areas and the support. The catalyst samples examined had been exposed to the molten carbonate atmosphere for 0, 50,100, 1000 and 2500 hours. 

The nickel signal from the surface of catalyst A exposed to a molten carbonate atmosphere for 50 hours was not present. This observation may be due to a thick layer of carbonate covering the active component, and blocking out the signal from the nickel. The carbonate layer is not as substantial in the examples treated for longer periods due to the carbonate being more evenly distributed by the action of heat and the gas stream. 

Cass, G. R., Boone, P. M., and Macias, E. S. (1982) Emissions and air quality relationships for atmospheric carbon particles in Los Angeles air in Particulate Carbon Atmospheric Life Cycle, edited by G. T. Wolff and R. L. Klimisch. Plenum Press, New York, pp. 207-240. 

Fig. 6.6 Repeated carbonation/calcination cycles of naturally occurring limestone conducted in a TGA. The experiment was performed isothermally at 750 °C using a carbonation atmosphere containing 40 vol.% CO2...

Kdntor,T. (1992) Considerations in the gas flow design of a graphite furnace vaporization interface effects of a halo-carbon atmosphere and sample matrix. Invited lecture. /. Anal. At. Spectrom., 7, 219-224. 

The production process for synthesis gas can indeed satisfy the conditions to produce an atmosphere with Uc >> 1, and thus a strong carbonizing atmosphere. This is in particular the case at temperatures in the range of 600-750° C and low steam dilution ratios. 

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