ガス放出挙動からみた鉄超微粉の表面状態と表面酸化層の還元

抄録

Surface conditions of three kinds of iron ultrafine powders (UFPs) were estimated by thermal desorption measurements. The iron UFPs exposed to air contain mixtures of Fe₃O₄ and γ-Fe₂O₃ phases and in some case additional α-Fe₂O₃ phase. Moreover, iron oxyhydroxide or its precursor compounds are produced by the reaction of surface oxides of UFPs with moisture in air.
Reduction experiments were carried out with thermogravimetry in a stream of hydrogen. The reduction is rate-controlled by the interface reaction and the reduction rate of the iron UFPs depends on the oxidation level, where the higher oxidized UFPs tend to lower the reduction rate. Activation energies of the reduction rate constants of two kinds of iron UFPs are 54 and 59 kJ/mol.