Nuclear gamma-resonance spectroscopy on ⁵⁷Fe nuclei, X-ray diffraction, and scanning electron microscopy have been used to study the narrow fractions of fly ash formed after combustion of the Ekibastuz coal. Two groups of samples of magnetic (ferrospheres) and non-magnetic type have been separated by granulometric and magnetic separation. A number of regularities associated with the granules size of fly ash have been established. According to the data of Mössbauer spectroscopy, a decrease in the magnetically ordered contribution has been identified with the growth of the particle size. After magnetic separation, iron in ferrospheres was found mainly in the structure of Fe₃O₄/γ-Fe₂O₃ and α-Fe₂O₃. The dominant phase was Fe₃O₄ (60–77%), the amount of which decreases with the growth of the grain size. With the growth of the particle size, the ratio of [Fe]^tetra/[Fe]^octa positions occupancy in Fe₃O₄ approaches 0.5; the structure of magnetite tends to the stoichiometric composition. α-Fe was found in the composition of ferrospheres, and a mechanism of its formation was proposed. The main components of the non-magnetic fractions of fly ash are mullite, hercynite, and silicate glass.

Mössbauer spectroscopy and X-ray diffraction have been used to study samples of fly ashes formed after combustion of coal from the Ekibastuz basin at the thermal power plants TPP-2 and TPP-3 in Almaty (Kazakhstan). It has been established that the fractions of fly ashes contain iron in the form of magnetite Fe₃O₄ and hematite α-Fe₂O₃. The mixed valence of iron Fe³⁺ ↔ Fe²⁺ in the octahedral sublattice of magnetite is destroyed by isostructural substitution impurities. Maghemite γ-Fe₂O₃ is additionally present in the fly ash of TPP-3 as a product of magnetite slow oxidation. It was shown that at T ≥ 1400 °C the proportion of magnetite in fly ashes increases due to decomposition of hematite, maghemite, hercynite and the drop of iron content in mullite. It was concluded that the amount of iron in magnetite is a temperature indicator of fly ashes formation. The parameters of hyperfine interactions have been determined in the iron-containing minerals of fly ashes. It was identified that formation of the fly ashes structure occurs in oxidizing atmosphere, since no traces were revealed of reducing environment effect on the phase composition.

Conversion electron Mössbauer spectroscopy was used to study the thin films obtained by co-precipitation of coatings from two sources: magnetron sputtering of a metal tantalum target and thermovacuum...