Fuel, Vol.78, No.4, 489-499, 1999
Carbonization of iron-treated Loy Yang coal
Carbonization of untreated and iron-treated Loy Yang coal was carried out at selected temperatures in the range of 200 degrees C-700 degrees C. The electrical conductivity was higher in all the iron-treated samples, except for the sample prepared at 700 degrees C, which was identical. Arrhenius plots of the conductivity of carbons treated above 500 degrees C exhibited considerable non-linearity but showed that the conductivity increase was caused by a change in the pre-exponential factor rather than in the activation energy. Mossbauer measurements revealed that the three, initially dispersed, paramagnetic iron species were transformed into magnetite and then principally, alpha- and gamma-iron between 400 degrees C and 600 degrees C. The electrical conductivity depended strongly on the concentration of carboxyl groups and suggested a model in which conduction between the pi-electron reservoirs was via an electron hopping mechanism along hydrogen-bonded cross-links. The enhanced removal of the carboxyl groups by the presence of iron aids the destruction of these poorly conducting links during carbonization.
Keywords:VICTORIAN BROWN COAL;POLY(VINYLIDENE CHLORIDE);ELECTRICAL-CONDUCTIVITY;INFRARED PHOTORESPONSE;PLASMA DECOMPOSITION;METAL-IONS;MOSSBAUER;PROPYLENE;FERROCENE