An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X24120019

A sample made from a ribbon of austenitic-martensitic steel 0.3C–13Cr–10Mn–3Si–1V, pre-deformed in the shape of a circular arc with a deflection of 3 mm, was subjected to fast neutron irradiation with a fluence of 6 × 1019 cm–2 in the vertical wet channel of the IVV-2M reactor at a temperature of 80°C. This material belongs to the class of stainless manganese austenitic steels with the shape memory effect (SME). Initially, it was expected that irradiation would reduce the SME magnitude after subsequent heating of the studied sample in comparison with the reference one. But instead, the manifestation of SME was revealed already after irradiation, with a decrease in the deflection by approximately 21

Using X-ray diffraction analysis, the effect of Ar+ ions with an energy of 15−20 keV (at ion current densities of 100−300 μA/cm2) on the microstructure, the level of internal microstresses and the texture of cold rolled ribbons of alloy Ni – 13.9 wt.% W is studied. It is found out that short-term irradiation of 80 μm thick ribbons with a fluence of 3.1·1016 cm–2 (for 50 s) at temperatures T ≤ 370°C and T = 630°C leads to a decrease in microstresses in their entire volume, while the original texture is retained. With an increase in the fluence to 9.7·1017 cm–2 at T = 630°C, the texture changes from (220) to (200). Changes in microstresses and texture on the irradiated and non-irradiated sides of 80-μm-thick ribbons are comparable to each other, despite the fact that the projected range of Ar+ ions with an energy of 15−20 keV in the alloy is only ~7 nm. It is known that annealing of such ribbons in an oven (700°C, 30 min) does not cause their recrystallization. At 850°C, the microstresses are relieved and the texture dramatically changes from (220) to (200) both as a result of annealing in a furnace (15 s) and as a result of irradiation with a fluence of 3.2·1016 cm–2 for 17 s, but the effect of stress removal in the course of furnace annealing is 3 times lower than that of irradiation. Thus, the following facts have been established: 1) the occurrence of recrystallization processes in the alloy under study during irradiation at a temperature lower than the temperature of the onset of thermally activated recrystallization and 2) a higher rate of microstress drop (and to lower values) in the course of irradiation than during furnace annealing. This indicates a significant role of nanoscale radiation-dynamic effects at the cascade-forming irradiation of metastable media.

Samples of Na4–xZr2-xNbxSi3O12 (x = 0–0.4) system are synthesized, phase analysis is performed, and the conductivity is measured. Samples with x = 0–0.25 are single-phase with a NASICON-type trigonal symmetry, space group R-3c. Na3.85Zr1.85Nb0.15Si3O12 solid electrolyte exhibits the highest sodium-cation conductivity (1.7 × 10−2 S × cm−1 at 300°, 10−5 S × cm−1 at 25 °C). High-temperature X-ray studies in the range of 25 to 727 °C were performed for this composition. Full-profile analysis was carried out for all temperatures to refine the structural parameters. Based on the experimental data, two elementary channels open for sodium cation migration were found using the method of tilings; the channels form a continuous three-dimensional network of migration paths. It is shown that the break of the lgσ–1/T plot at 480 °C is due to a sharp decrease in the strength of the Na–O bond in NaO6 octahedra and the consequent increase in the mobility of sodium cations in 6b (000) sites.

In the work, a specially prepared powder of the model ordered Cu3Au alloy was used to investigate peculiarities of internal processes that take place in the ordered precipitates similarly to those occurring in austenitic reactor steel under irradiation with fast neutrons. It is shown that, unlike the thermal or deformation disordering, in the case of such impact, the dependence of the lattice parameter on the degree of long-range order presents a kink that testifies to the development under irradiation of competitive processes in the defect structure of the studied material.

Crystal structure features of NaFeO2 and NaAlO2 were studied using neutron diffraction and X-ray powder diffraction. The conductivity of these compounds was also investigated. The migration paths in the structure of sodium ferrite and aluminate were modeled by topological (tiling) and DFT methods. The sizes of through sodium-cations migration channels in low-temperature β-modifications of the compounds in question were determined using the ToposPro software package. It is shown that an increase in the size of these migration channels correlates with an increase in ionic conductivity. The conductivity in high-temperature γ-phases of NaFeO2 and NaAlO2 is determined by two competing processes: an increase in activation energy caused by a decrease in the cross-sections of the channels and a transition from one-dimensional conductivity to three-dimensional one.

The crystalline and magnetic structure of the nonstoichiometric intermetallic compound Tm 2 Fe 18 has been investigated in the temperature interval from 3 to 300 K using the methods of neutron diffraction, synchrotron radiation, and ultra-small-angle neutron scattering. A theoretical interpretation of the spin-reorientation transition has been given and the value and temperature dependence of the first constants of magnetic anisotropy for the sublattices of iron and thulium have been determined. Based on the results of experiments and theoretical interpretation of small-angle neutron scattering, a conclusion has been made on a reconstruction of the domain structure upon spin-reorientation phase transition.

Samples of fuel claddings after their operation life in the BN-600 reactor have been investigated. They were irradiated with fast neutrons with a damage dose from the range 1.5-81.4 dpa and at temperatures from 643 to 798 K. Using the FullProf program analysis, data on the microstructure, texture, and microdeformations were gained. From the anisotropic broadening of reflections estimated by the Williamson-Hall method, the density of dislocations and their type were calculated. A conclusion is made on a significant impact of the irradiation temperature on the dislocation density. It is shown that neutron diffraction is an attractive way of investigation of microstructure of massive samples subjected to such high irradiation doses without leading the staff into any radiation danger. Published by Elsevier B.V.

The applicability of the method of high-resolution neutron diffraction for determining defects (dislocations) in the bulk of a material is shown based on the example of a standard sample of deformed copper. The structural state of several samples of fuel-element claddings made of cold-worked steel 16Cr–15Ni–2Mo–2Mn–Ti–V–B (grade ChS68-ID) used in the BN-600 reactor, which were prepared by two producers, i.e., at the PJSC Mashinostroitel’nyi Zavod (MSZ) and at the PJSC Pervoural’sk Novotrubnyi Zavod (PNTZ), have been investigated. The conclusion has been drawn that the claddings have a texture in which the crystallographic planes of grains are oriented along the axis of the shells. It has been shown that the main defects in these claddings are edge dislocations; their density has been determined.

Analysis of correlation between structural features and rubidium ion conductivity is performed for RbFeO2 polymorphs in a wide temperature range of 296–843 K. To explore the migration maps of Rb+ cations, we used neutron diffraction data for low- and high-temperature RbFeO2 polymorphs and natural tiling concept implemented in the TOPOS software. Five independent elementary channels for the Rb+ cation migration have been revealed whose cross- sections were found to be essentially different in the low-temperature form, indicating a high anisotropy of the cation conductivity. During the transition to the cubic high-temperature phase all five channels become equivalent with sharply increased cross-sections, which accounts for the increase of cations mobility and gives rise to the three-dimensional character of conductivity.

The structure peculiarities of K0.9Fe0.9Ti0.1O2 that favor the emergence of a superionic state have been studied using neutron powder diffraction data as a function of temperature. The migration paths in the structure of both, undoped and doped potassium ferrite were modeled by topological (tiling) and DFT methods. It is shown that heating of the low-temperature phase leads to increase of the ionic conductivity thanks to widening the migration channels and the appearance of thermally induced cation vacancies. The calculated migration barrier is found to not exceed 0.3 eV/ion in all phases, which is consistent with the experimental data. Doping also increases the ionic conductivity, but up to about 10% of Ti only; then the experimental activation energy even increases. The DFT modeling shows that it can be caused by growth of the regions unavailable for the mobile cations; the regions are formed around the dopant atoms.

Crystal structure and magnetic and thermomagnetic properties of the (TmxPr1-x)(2)Fe-17 system have been studied. The alloys with x = 0-0.4 and x = 0.8-1 crystallize into a rhombohedral structure of the Th2Zn17-type and into a hexagonal structure of the Th2Ni17-type, respectively. Both these structures coexist in the concentration range x = 0.5-0.75. The compounds with 0 < x < 0.6 are ferrimagnets, while in the compounds with x = 0.6-1, an additional high-temperature helimagnetic state appears. The lattice parameters, spontaneous magnetization, and the peak entropy change -Delta S-M of the (TmxPr1-x)(2)Fe-17 system decrease with increasing Tm content. The temperatures of helimagnetic ordering and ferrimagnet-to-helimagnet transition decrease non-monotonically as Tm content increases, with the minimum values being for the composition with x = 0.8. Microdeformations in the alloys with x = 0.5-0.9 have been detected by means of neutron diffraction. (C) 2017 Elsevier B.V. All rights reserved.

Методом высокотемпературной нейтронографии исследована кристаллическая структура галлата рубидия RbGaO2 в интервале температур 300-853 K. Методом компьютерного моделирования с использованием программы TOPOS определены каналы, доступные для движения катионов рубидия в низко- и высокотемпературной формах RbGaO2. Установлена корреляция между радиусом сечения каналов миграции и рубидий-катионной проводимостью. Работа выполнена с использованием УНУ "НМК ИФМ" в рамках государственного задания ФАНО России (тема "Поток", N 01201463334).

The crystal structure of rubidium gallate RbGaO2 in the temperature range of 300–853 K has been investigated using high-temperature neutron diffraction. The channels available for the motion of rubidium cations in the low-temperature and high-temperature modifications of RbGaO2 have been determined using the computer simulation with the TOPOS program. A correlation between the radius of the migration channel cross section and the rubidium cation conductivity has been established.

Nickel specimens subjected to fast-neutron irradiation followed by annealings have been examined using neutron and X-ray diffraction. The type of structural defects, which result from the fast-neutron irradiation of nickel crystals, has been first identified using neutron diffraction and the experimental dependence of the lattice parameter on the concentration of interstitial defects has been determined. It is shown that the changes in the lattice parameters due to both irradiation and annealings are primary related to the variations in the concentration of interstitial atoms in the lattice.

A quantitative assessment is presented of the dislocation density and relative fractions of edge and screw dislocations in reactor-steel samples 16Cr–15Ni–3Mo–1Ti subjected to preliminary cold deformation by rolling and subsequent fast neutron irradiation using neutron diffraction analysis. The Williamson–Hall modified method was used for calculations. It is shown that the fast neutron irradiation leads to a decrease in the density of dislocations that appeared after samples deformation. The applicability of neutron diffraction analysis to the examination of dislocation structure of deformed and irradiated materials is shown.

Understanding the mechanisms of radiation-induced phenomena in FCC-materials is of fundamental significance for the development of new austenitic reactor steels.An important role in these phenomena, along with the crystal structure and chemical composition of the matrix, belongs to doping elements and the microstructure of the material.In this paper, peculiarities of competing processes that proceed under fast neutron irradiation in Cr-Ni-Mo steels doped with Ti are studied by means of neutron diffraction.It is demonstrated that, on the one hand, new Ni 3 Ti -phase particles are formed and, on the other hand, they dissolve to form interstitial Ti atoms.Besides, there is radiation-induced relaxation of microscopic stresses, which, in the case of large neutron fluences, overlaps with additional microstresses resulting from the accumulation of radiation-induced defects.The observed effects agree with the results we obtained for other austenitic steels.