7 research outputs found
Application of thermal analysis to study of phase composition changes in blast furnace sinters
Mössbauer-Effect Study of Ca-Substituted Magnetites
CaxFe3-xO4 samples, with x≤0.28, prepared from αFe2O3 and CaO by the Bridgeman method were investigated by means of 57 Fe Mössbauer spectroscopy. Room temperature spectra gave evidence that the samples were multi-phase with 73% to 99% contribution of the calciomagnetite, depending on the sample. Analysis of the subspectra associated with the calciomagnetite enabled to conclude that Ca-ions reside on the tetrahedral (A) sites and have not random distribution. They reduce the hyperfine field at Fe nuclei occupying the octahedral positions (B) by 12.3(1.0)kOe per one Ca-ion and cause a decrease of the average hyperfine field, /dx at the rate of 29 kOe/mol% for x≤0.07 and of 387 kOe/mol% for larger x. A linear correlation between and the average isomer shift was revealed to hold. It permitted to conclude that Ca-doping causes a decrease of the spin-density and an increase of the charge-density at Fe nuclei occupying the B-sites of magnetite
Mössbauer-Effect Study of Calciomagnetites
CaFeO samples, with x ≤ 0.28 , prepared from α-FeO and CaO by the Bridgman method were investigated by means of Fe Mössbauer spectroscopy. Room temperature spectra gave evidence that the samples were multiphase, the calciomagnetite being the dominant phase with a contribution of 73% to 99%, depending on the sample. Analysis of the subspectra associated with the calciomagnetite gave evidence that Ca-ions reside on the tetrahedral (A) sites and have not random distribution. Their presence on those sites causes a reduction of the hyperfine field at Fe nuclei occupying the octahedral positions (B) by 12.3(1.0) kOe per one Ca-ion and a decrease in the average hf field, 〈H〉/dx, at the rate of 29 kOe/mol% for x ≤ 0.07 and of 387 kOe/mol% for larger x. In addition, a linear correlation between 〈H〉 and the average isomer shift, 〈I〉, was revealed to hold. It indicates that addition of Ca-ions into the magnetite causes a decrease in the spin-density and an increase in the charge-density at Fe nuclei occupying the B-sites