Thornton, Matthew James
Catalytic carbon deposition on 3-dimensional carbon fibre supports.
PhD thesis, University of Nottingham.
Catalytic carbon deposition reactions, using methane, ethane or synthetic natural gas (1.8 vol. % propane, 6.7 vol. % ethane and balance methane) as the carbon-containing gas feedstock with or without the addition of hydrogen, have been investigated over nickel, cobalt and iron catalysts supported on 3-dimensional carbon fibre supports, using both a horizontal tube furnace and an isothermal, isobaric induction furnace.
The transition metal catalysts were prepared by impregnating 3-dimensional carbon fibre supports with a methanolic solution of the metal nitrate, using a wet impregnation technique, and the effects of temperature, gas composition and deposition time on their catalytic behaviour was studied. Samples were characterised using a number of complementary techniques, including X-ray diffraction, scanning electron microscopy, polarised light microscopy, transmission electron microscopy, thermogravimetric analysis, digital photography and weight change measurements. The findings from these techniques were used to explain the observed type and amount of carbon deposited.
Nickel was found to be the most active catalyst and methane was found to be a poor carbon precursor for the catalytic deposition of carbon, from these findings nickel was chosen as the catalyst and ethane and synthetic natural gas were used as the carbon precursors, with and without the addition of hydrogen.
The activity of the nickel catalyst was found to be dependant on a number of factors; weight percent used, temperature, gas feedstock used and deposition time. It was found, in all cases, that increasing the deposition temperature resulted in higher deposition rates, ethane was found to yield higher deposition rates than synthetic natural gas and the effect of hydrogen addition had a negligible effect upon the rate of carbon deposition for the reactions carried out in ethane whereas it was significant for the reactions carried out in synthetic natural gas. The majority of the carbon deposition took place in the first three hours of deposition, with extended deposition times only yielding small increases in the overall rate of carbon deposition.
The type of carbon deposited varied from filamentous carbon i.e. carbon nanotubes, nanofibres and microcoils, to encapsulation. The factors affecting the type of carbon deposited were, the temperature of carbon deposition, with higher temperatures (800C) yielding encapsulation and lower temperatures (650C) yielding filamentous carbon, and the addition of hydrogen, with higher hydrogen concentrations favouring the formation of filamentous carbon over encapsulation. It was also found that the addition of hydrogen did not extend the lifetime of the catalysts.
It was found that nickel catalysts could be used within larger carbon fibre preforms to catalytically deposit carbon at lower temperatures than those used in industry for the manufacture of carbon-carbon composites (> 1000C).
Thesis (University of Nottingham only)
||catalytic carbon, carbon nanofibres, carbon nanofibers, carbon nanotubes, carbon-carbon composites, CVI, CVD, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, chemical vapour infiltration, chemical vapor infiltration, chemical vapour deposition, chemical vapor deposition, induction heating, filamentous carbon, carbon nanofilaments, carbon, nickel
||T Technology > TA Engineering (General). Civil engineering (General)
||UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
||04 Jan 2006
||13 Sep 2016 15:25
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