Oxides RBa₂Cu₃O_6+δ(R=Y, Nd) subjected to mechanical activation in AGO-2 mill have been studied by X-ray photoelectron spectroscopy (XPS), thermal analysis, and magnetometry. It has been shown that mechanoactivation accelerates chemical degradation under the impact of H₂O and CO₂in YBa₂Cu₃O_6+δsamples. Degradation occurs in the standard way. Investigation of mechanically activated NdBa₂Cu₃O_6+δhas revealed other results. It has been suggested that CO₂can diffuse into its structure more freely than in YBa₂Cu₃O_6+δ; as a result, carbonization may proceed directly in the volume of NdBa₂Cu₃O_6+δand independently of the hydrolysis process. In addition, the mechanism of interaction between the oxide and water is not active and not “traditional” for the homologous series REBa₂Cu₃O_6+δ(where RE = rare earth and Y)—the characteristic “color” phase (Nd₂BaCuO₅) is not formed during hydrolysis. It is known that high-temperature treatment of NdBa₂Cu₃O_6+δoxide results in partial substitution of cations Ba by Nd; which is accompanied by decrease in the superconducting transition temperature and formation of the impurity phase Ba₂Cu₃O_5+y. According to our data, mechanical activation of the resulting solid solution Nd_1+xBa_2−xCu₃O_6+δunexpectedly has led to the reverse redistribution of cations, which has been manifested in the complete disappearance of the impurity phase and increase inTc.

This paper presents a systematic review of the literature concerned with the physicochemical analysis of the thermodynamic systems Ca-Mn-O, Sr-Mn-O, and Ba-Mn-O at variable temperature and oxygen pressure in the gas phase. Available data are systematized in the form of projections of the phase diagrams of these systems onto the alkaline earth-managanese-oxygen composition triangles. Compatibility triangles are identified in the projections, and the phase relations involved are discussed. The conclusion is drawn that the physicochemical data reported to date are insufficient for the thermodynamic analysis of heterogeneous equilibria in the A-Mn-O systems, which is hindered primarily by the lack of information about the equilibrium oxygen pressure as a function of temperature for the thermal dissociation (or oxidation) of A_xMn_yO_z (A = Ca, Sr, Ba) oxides.

The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the reactions of their reduction through the solid and gas phases. Experimental data on the reduction of iron from industrial scale, obtained by the DSC (differential scanning calorimetry) method, show the kinetic dependence of the rate and completeness of recovery on external factors: pressing pressure during sample preparation and the reagents’ composition. The pressing pressure, under conditions of iron ions’ solid-phase diffusion, has the significant effect by increasing the reagents’ contact area. Under conditions of iron ions’ comprehensive diffusion, the pressing pressure does not affect the reduction processes rate. The introduction of 10 mass.% flux into the raw mixture composition leads to a partially liquid-phase diffusion of iron ions and weakens the effect of the pressing pressure in this process. An ion diffusion-catalytic mechanism is proposed to describe the observed effects during the reduction of iron oxide of technogenic origin.