Electric properties of oxyfluorides Ba2In2O 5-0.5x F x with brownmillerite structure

Synthesis of fluoro-substituted substances based on brownmillerite Ba 2In2O5 is carried out. The width of the homogeneity region of the Ba2In2O5-0.5x F x (0 < x ≤ 0.25) solid solution was established using X-ray analysis. Measurement of temperature dependences of conductivity in atmospheres with different partial pressure of water vapor (pH2O = 3.3 and 2 Ч 103 Pa) showed an increase in conductivity at T ≤ 550 C in a humid atmosphere, which is due to appearance of proton transport. The dependence of conductivity on partial oxygen pressure (pO2 = 0.21 Ч 105 to 10-15 Pa) is studied in the temperature range of 500-1000 C; ion transport numbers are calculated. The method of polarization measurements was used to determine transport numbers of fluoride. Total conductivity is divided into ion (proton, oxygen, and fluoride ion) and electron components. Analysis of concentration dependences of conductivities showed that low concentrations of fluoride allow increasing both the total and partial conductivities (oxygen-ion and proton) and, besides, allow shifting the "order-disorder" phase transition by 100 C to the low temperature range. © 2013 Pleiades Publishing, Ltd

Изучение закономерностей осаждения тонких сорбционно-активных пленок диоксида марганца на различных полимерных носителях

Manganese dioxide (MnO2) is used as a sorption material for the isolation of a wide range of substances from aqueous media. A number of composite materials containing MnO2 are known, while in the scientific literature there are no systematic data on the possibilities of obtaining flat thin-layer sorbents of manganese dioxide on other polymer carriers. In this study, a number of flat thin-layer sorbents, consisting of manganese dioxide deposited on the surface of various carriers, were synthesized. The most common flat materials were used as carriers - polyethylene (PE), polypropylene (PP), biaxially oriented polypropylene film (BOPF), polyethylene terephthalate (PET), cellulose triacetate (CTA). The films were kept in an acidic solution of potassium permanganate, washed, and the manganese content was determined. It was shown that according to the rate of deposition of manganese dioxide on the surface of the carrier, these materials are arranged in a row: CTA >> PE> BOPF> PET ≈ PP. It was found that the dependences of the specific content of manganese dioxide on the surface of polymer carriers were well approximated by straight lines (R2 = 0.964 - 0.997); the results of linear processing of the dependences were used to determine the deposition rates of manganese dioxide, ranging from 1.55 ± 0.26 μg/(cm2 day) for PP up to 166 ± 11 μg/(cm2 day) for CTA. It was shown that the high rate of deposition of manganese dioxide on the surface of the CTA in comparison with other polymer carriers was most likely due to the macroporous texture of the CTA surface. It was also shown that with a specific content of manganese dioxide of the order of 150-300 μg/cm2 achieved after 1-2 days of CTA treatment in a permanganate solution, a continuous uniform sorption-active layer was formed, and with a longer exposure time, an increase in the average layer thickness occurred due to the growth of individual crystallites already on the surface of a continuous layer of manganese dioxide, leading to a significant heterogeneity of the sorption-active surface, as well as to a stable deformation of the film. The sorption of 223Ra was studied on a series of obtained sorbents. It was shown that the amount of manganese dioxide phase in the composition of thin-layer sorbents had practically no effect on the sorption of radium from a salt-free solution, but strongly influenced sorption from 0.5 M NaCl. Also, for the MnO2-CTA sorbent the deterioration of the quality of the alpha spectrum due to the diffusion of radium deep into the sorbent was demonstrated. © 2021 Semenishchev V.S., Oglezneva V.Yu., Titova S.M.,Malyshev A.S., Filinkova V.K.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 20-03-00931