Laves Phase Formation in High Entropy Alloys

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfN-bVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x = 12x-VCrMoMnFe, 12x + Sc, 12x + Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x + Be alloy reveals a single-phase C14 structure with a very high concentration of structural defects and ultra-fine dendritic microstructure with an almost homogenous distribution of the constituted elements over the alloy matrix. The analysis of electrical and magnetic properties reveals that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggest that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Acknowledgments: Experiments were performed using scientific instruments included in the Collective Equipment Center “Ural-M” and the “Geoanalitik” shared research facilities of the IGG UB RAS. The re-equipment and comprehensive development of the "Geoanalitik" shared research facilities of the IGG UB RAS is financially supported by the grant of the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2021-680). The numerical calculations are carried out using computing resources of the federal collective usage center ‘Complex for Simulation and Data Processing for Mega-science Facilities’ at NRC ‘Kurchatov Institute’ (accessed on ckp.nrcki.ru/, 11 January 2021) and Joint Supercomputer Center of Russian Academy of Sciences (accessed on www.jscc.ru, 1 January 2021)

RADIATION-OPTICAL PROPERTIES OF RARE-EARTH ION DOPED ALYMINIUM OXYNITRIDE

Pulsed cathodoluminescence and X-ray luminescence spectra of Al50 6N:Ce3+ and A1506N:Eu2+ have been investigated. The concentration dependencies of luminescence intensity have been measured and discussed.Работа выполнена при финансовой поддержке Минобрнауки РФ (стипендия Президента РФ - 2015) и УрФУ (грант молодым ученым - кандидатам наук)

NEW OPTICAL MATERIALS BASED ON ALUMINUM OXYNITRIDE

Aluminum oxynitride is a promising compound for creating optical ceramics for designing phosphors, LED components and radiation detectors. Our research is focused on luminescent properties of Ce- and Eu-doped aluminum oxynitride Al5O6N

CATHODOLUMINESCENCE OF ALUMINUM OXYNITRIDE Al5O6N WITH DOUBLE DOPING BY RARE-EARTHED IONS

Pulsed cathodoluminescence of aluminum oxynitride Al5O6N doped with Er3+, Ho3+ and Ho3+, Tm3+ ions has been measured. The narrow lines registered at 460, 480 and 663 nm are related to 1D2→3F4, 1G4→3H4 transitions in Tm3+ ion and 5F5→6I8 transition in Ho3+ ion.Работа выполнена при поддержке Российского Фонда Фундаментальных Исследований (проект РФФИ № 17-03-00630_а)

PHOTOLUMINESCENCE OF ALUMINUM OXYNITRIDE Al5O6N DOPED WITH RARE-EARTH IONS

Photoluminescence (PL) spectra and pulsed PL decay curves of aluminum oxynitride Al5O6N (ALON) doped with Ce3+ and Eu2+ ions were measured. In PL spectra broad bands with maximum at 380 nm (ALON:Ce) and 500 nm (ALON: Eu) related to d-f transitions in rare-earth ions are observed. Pulsed PL decay curves approximated with exponential expression with one component (ALON:Ce) and two components (ALON: Eu), de-cay times is 24 ns and 313 ns, 1025 ns respectively.Работа выполнена при поддержке Российского Фонда Фундаментальных Исследований (проект РФФИ № 17-03-00630_а)

THERMOLUMINESCENT DETECTOR BASED ON ALUMINUM OXYNITRIDE Al5O6N:Ce3+

The new working medium for thermoluminescent dosimetry based on Сe-doped aluminum oxynitride has been proposed. It has a number of advantages for radiation monitoring due to low temperature of main dosimetric peak, high luminescence quantum yield and upper limit of linear dose dependence range at 60 Gy

Dynamics of improving the health status of students of the Ural Federal University, belonging to a special medical group

Статья содержит теоретические и практические материалы по проблеме улучшения состояния здоровья студентов ВУЗа, относящихся к специальной медицинской группе.The article contains theoretical and practical materials on the problem of improving the health status of university students belonging to a special medical group

Games and amusements of the Middle Urals as folk pedagogic tradition

В статье описаны наиболее известные народные игры и забавы, распространенные на Среднем Урале.The article describes the most famous folk games and amusements common in the Middle Urals

Physical properties of some Sn-Cu melts at high temperatures

Several physical properties (density, viscosity, ultrasound velocity, electroresistivity and magnetic susceptibility) of pure tin, copper, silver and their alloys with near eutectic compositions are investigated in the wide temperature range up to 1600 degrees C. In cases of copper and silver the temperature dependences of properties are found to be smooth. As for liquid tin, three temperature ranges with abnormal behaviour of properties were discovered: t(1) near 400 degrees C (anomalies in density and electroresistivity); t(2) = 1000-1050 degrees C (anomalies in viscosity and electroresistivity); t(3) approx. 1400 degrees C (anomalies in density, electroresistivity and magnetic susceptibility). The decrease in heating rate from 4 to 1 degrees C/min shifts t2 down to 800 degrees C, and the purification of samples from 99.9 to 99.999% provides the incoincidence of viscosity heating and cooling curves for all the temperatures below 800 degrees C. The introduction of copper into liquid tin (99.9% purity) shifts the temperature of anomaly t(2) from 1000-1050 degrees C to 790 degrees C. We connect this abnormal behaviour of physical properties at t(an) with beta-gamma structural transformation. Hence, by warring regimes of melts heat treatment before solidification it becomes possible to obtain samples with different properties in solid state

Physical properties of some Sn-based melts

The physical properties (viscosity, density, electroresistivity and magnetic susceptibility) of pure tin, copper, silver, some binary (Sn - Ag, Sn - Cu, Sn - Bi, Sn - Zn) and ternary (Sn-Ag-Cu, Sn-Bi-Ag, Sn-Bi-Zn) alloys with near eutectic compositions are investigated in wide temperature ranges. The irreversible decrease of viscosity in pure tin melt is discovered at 820 degrees C during heating. The similar anomaly with the following hysteresis of dynamic viscosity was fixed for binary and ternary alloys but at higher temperatures - 900 degrees C and 950 degrees C respectively. For all the systems it was shown that the alloys with eutectic compositions differ significantly in their electric and magnetic properties from hypo- and hypereutectic ones. Qualitative and quantitative metallographic analysis for Sn-3.8wt.%Ag-0.7wt.%Cu samples, heated low and above characteristic temperatures, showed the influence of melt overheating on crystallization kinetics