Preparation of the nanocrystalline iron carbide in reaction of iron
with methane or methane/hydrogen mixture
W. Arabczyk, W. Konicki, U. Narkiewicz
Technical University of Szczecin, Institute of Chemical and
Environment Engineering, Pulaskiego 10, 70-322 Szczecin, Poland
The nanocrystalline iron samples used in experiments contained small
amounts of additives (Al[2]O[3],CaO) applied as structural modifier,
to avoid the sintering of small iron crystallites at high
temperatures. The nanocrystalline iron carbide has been obtained by
the reaction of pure methane, or CH[4]/H[2] (2 :1) gas mixture with
nanocrystalline iron under atmospheric pressure, at 580OC. The
carburisation process has been controlled by a thermobalance.
The rate of the carburisation process has depended on chemical
composition of the iron surface and on the conditions of the process
(temperature and the composition of the gas mixture) As a result of
the carburisation the iron carbide is obtained together with
unconverted a-iron or together with a carbon deposit. The optimal
conditions to obtain only iron carbide can be reached when the
reaction rate is lowered, by the dilution of methane with hydrogen or
by a modification of nanocrystalline iron surface with sulphur or with
potassium.
The samples before and after the carburisation process have been
characterised using the following methods: XRD and SEM. The average
size of the obtained iron carbide crystallites amounts 35 nm.
|