After growing lanthanide oxide (Ln2O3) bearing materials I sometimes find small voids isotropically spread in grown crystals. Can lanthanide cabronates/oxocarbonates form during heating and decompose during cooling of the melt?
The typical process is held under the flow of Ar+5%CO2 at temperature range 100-2100 C.
I will humbly say “NO”. But at high temperatures, some fine carbon particles are struck up in the interstial voids .This can be avoided by equimolar CH4/CO2 reforming at783-883K. This fact has already been repoted during the catalytic studies of La2O3 and mixed oxides like La2O3/NiO.
Pls. find the reference:
Promotional effect of alkaline earth over Ni–La2O3 catalyst for CO2 reforming of CH4: Role of surface oxygen species on H2 production and carbon suppression. Sutthiumporn, K.; Kawi, S. International Journal of Hydrogen Energy vol. 36 issue 22 November, 2011. p. 14435-14446
The last two lines of the abstract are reproduced for your kind perusal
--------which can then react with the surface carbon species formed during DRM, resulting in higher CO2conversion and LOWER CARBON FORMATION.
Still another reference( IN BOLD LETTERS):
1. Natural Gas Conversion VIII: Proceedings of the 8th ...
books.google.co.in/books?isbn=0080497837
Fabio Bellot Noronha, Martin Schmal, Eduardo Falabella Sousa-Aguiar - 2011 - Technology & Engineering
than those of CO2 on the catalyst A, LEADING TO THE DEPOSITION OF CARBON ... A. The addition of La2O3 to the catalyst AL can improve CO2 reaction activity, which can ...higher than RP,CH4, meaning that the activated CO2 by La2O3 improves the ... 825 840 855 870 885 765 780 795 810 825 840 855 870 885 Temperature (K) ...
I find this an elegant solution to the problem. This would explain a small mass loss in temperature regime RT...400C in air.
Many thanks.
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