Zinc-Ferriteに関する研究 (第4報)

酸溶解の機構について

抄録

In order to clarify the dissolution mechanism of zinc-ferrite, the effects of the cooling rate, Fe₂O₃/ZnO ratio, and the formation atmosphere on the dissolution rate were investigated.
In the present experiments, the following results were obtained.
(1) The zinc-ferrite formed at 1000°C has the same intrinsic dissolution rate k (g·min^-1·m^-2) irrespective of the cooling rate. The dissolution rate of that formed above 1100°C, depends on the coolingrate and, if cooled rapidly, the rate increases considerably, whereas, if cooled slowly, the rate remainsto. be much the same as thas of 1000°C.
(2) If excess Fe₂O₃ is present in zinc-ferrite in solid solution, the intrinsic dissolution ratedecreases and the more Fe₂O₃ in zinc-ferrite, the smaller is the dissolution rate. The rate increases againif Fe₂O₃ is precipitated during slow cooling.
(3) If the zinc-ferrite formed at 1200°C is heated in vacuum at 1000°C, the intrinsic dissolutionrate increases considerably, while, if heated in air at 1000°C, the rate becomes almost the same value asthat of the zinc-ferrite originally formed at 1000°C.
From these results, it can be concluded that the zinc-ferrite of 0^2-deficient composition dissolvesin dilute sulfuric acid more rapidly than that of stoichiometric composition, and that therefore the dissolutionof zinc-ferrite-is initiated from the anion vacancy sites and the rate is controlled by the concentrationof anion vacancies.