抄録
Ferrugineous sinters from various origins and synthetic hydrous ferric oxide were investigated by DTA, TG, and X-ray diffraction techniques and chemical analysis. The samples studied showed an endothermic peak at 100° due to dehydration and an exothermic peak at 850°, possibly due to the formation of α-Fe2O3. From DTA curve, natural samples can be divided in the following three groups: (1) Those having an endothermic peak at 650°, which is characteristic to the sinters formed at pH's below 5.4. The peak represents the elimination of SO3. (2) Those having an exothermic peak at 650°, but without any weight loss. The sinters, high in SiO2 and/or Al2O3 and formed at pH's above 5.6, belong to this group. (3) Those having exothermic peaks at 650° and 750°. No weight change was recorded for these peaks. The sinters of this group are similar to those the second group in the chemical composition, but low in SiO2. The effect of formation pH on thermal behavior of the sinters was also confirmed by synthetic studies.
