THE CAUSE OF SURFACE-TENSION INCREASE WITH TEMPERATURE IN MULTICOMPONENT ALUMINOSILICATES DERIVED FROM COAL-ASH SLAGS

An explanation is proposed for the increase of surface tension with te mperature in multicomponent aluminosilicate systems such as those deri ved from coal-ash stags. Two major factors are considered: (1) depolym erization of aluminosilicates caused by rearrangements of intermediate structures in the surface layers, and (2) the increase in surface ent ropy caused by evaporation of some ash slag components. Electron spect roscopy for chemical analysis spectra were recorded for oxygen Is phot oelectrons on quenched bulk slags and on sessile drops to gain insight into the depolymerization of coal-ash stags with temperature. The tes ts performed on quenched bulk slags indicated replacement of bridging oxygen [Si-O] with non-bridging oxygen atoms [Si-O-] as a function of increasing temperature. Mossbauer spectra showed an increase in ferrou s iron from 4% to 12% of total iron as temperature rose from 1400 degr ees C to 1500 degrees C. The increase in non-bridging oxygens resulted from the reduction of tetrahedrally coordinated Fe3+ to octahedrally coordinated Fe2+. Also, the intensity of the non-bridging oxygen Is ph otoelectron peak was higher when detected on the surface of a sessile drop than when detected from the bulk of the drop.