Wadsley–Roth phases accommodate variable cation charge by crystallographic shear planes delineating blocks of the parent ReO3 structure. The homologous series TiNb x O2+2.5x provides possible new ...anode materials for lithium-ion batteries. The thermodynamic stability of three of these shear phases was determined by high-temperature oxide melt solution calorimetry. TiNb2O7, TiNb24O62, and TiNb5O14.5 (often called Ti2Nb10O29) all have positive enthalpies of formation from binary oxides (TiO2 and Nb2O5), implying that they are entropy-stabilized and only stable above some minimum temperature. Hence, shear phases may represent a new and extensive class of “entropy-stabilized oxides”. Their thermodynamic stability decreases with the increasing Nb content. Entropies of formation were calculated using the measured enthalpy of formation and assuming that their synthesis temperature is their lowest temperature of stability and using calculated configurational entropies arising from cation disorder. TiNb24O62 has a high entropy consistent with extensive disorder, whereas TiNb2O7 and TiNb5O14.5 appear to be substantially more ordered. These entropy values are further constrained by considering the stability of the Wadsley–Roth phases with respect to each other. TiNb2O7 and TiNb5O14.5 can be relatively stable intercalating anode materials, while TiNb24O62 is likely to decompose near room temperature during extended battery cycling. This work accentuates the underlying role of thermodynamic studies in engineering electrochemically active materials with enhanced stability for next-generation lithium-ion batteries and beyond.
High entropy oxides (HEOs) have experienced a meteoric rise in the past decade. Here, we report a new class of entropy stabilized A6B2O17 (A = Zr, Hf; B = Nb, Ta) oxides whose enthalpies of formation ...have been determined by high temperature oxide melt solution calorimetry. All four compounds have endothermic enthalpies of formation from binary oxides (AO2 and B2O5), indicating that these modulated phases are entropy stabilized. The unfavorable energetics of formation are counterbalanced by large configurational entropy arising from cation disorder. The calculated configurational entropy per formula unit for A6B2O17 is 4.50R J/mol⋅K, which is ~2.8 times higher than the maximum configurational entropy value of 1.61R for an equimolar five cation containing “high entropy oxide”. Based on X-ray and neutron diffraction data, measured enthalpies of formation and calculated configurational entropies, one can infer that all four compounds have a high degree of disorder.
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The stability of functional materials in water-containing environments is critical for their industrial applications. A wide variety of metal–organic frameworks (MOFs) synthesized in the past decade ...have strikingly different apparent stabilities in contact with liquid or gaseous H2O, ranging from rapid hydrolysis to persistence over days to months. Here, we show using newly determined thermochemical data obtained by high-temperature drop combustion calorimetry that these differences are thermodynamically driven rather than primarily kinetically controlled. The formation reaction of a MOF from metal oxide (MO) and a linker generally liberates water by the reaction MO + linker = MOF + H2O. Newly measured enthalpies of formation of Mg-MOF-74(s) + H2O(l) and Ni-MOF-74(s) + H2O(l) from their crystalline dense components, namely, the divalent MO (MgO or NiO) and 2,5-dihydroxyterephthalic acid, are 303.9 ± 17.2 kJ/mol of Mg for Mg-MOF-74 and 264.4 ± 19.4 kJ/mol of Ni for Ni-MOF-74. These strongly endothermic enthalpies of formation indicate that the reverse reaction, namely, the hydrolysis of these MOFs, is highly exothermic, strongly suggesting that this large thermodynamic driving force for hydrolysis is the reason why the MOF-74 family cannot be synthesized via hydrothermal routes and why these MOFs decompose on contact with moist air or water even at room temperature. In contrast, other MOFs studied previously, namely, zeolitic imidazolate frameworks (ZIF-zni, ZIF-1, ZIF-4, Zn(CF3Im)2, and ZIF-8), show enthalpies of formation in the range 20–40 kJ per mole of metal atom. These modest endothermic enthalpies of formation can be partially compensated by positive entropy terms arising from water release, and these materials do not react appreciably with H2O under ambient conditions. Thus, these differences in reactivity with water are thermodynamically controlled and energetics of formation, either measured or predicted, can be used to assess the extent of water sensitivity for different possible MOFs.
Order-disorder on both cation and oxygen sites is a hallmark of fluorite-derived structures, including pyrochlores. Ordering can occur on long- and short-range scales and can result in persistent ...metastable states. In various cubic oxide systems, different types of disorder are seen. The purpose of this paper is to review and compare the types and energetics of order-disorder phenomena in several families of cubic oxides having pyrochlore, weberite, defect fluorite, perovskite, rocksalt, and spinel structures. The goal is to better understand how structure, composition, and thermodynamic parameters (enthalpy and entropy) determine the feasibility of different competing ordering processes and structures in these diverse systems.
Macroeconomic regulation has always been one of the most pressing economic issues. The paper intends to assess the impact of the government policy on maintaining macroeconomic stability on the ...economic growth in the Republic of Armenia. Methodologically, the study relies on the propositions of economics; applies methods of qualitative and statistical analysis, observation and synthesis. The data are sourced from the National Statistics Service of the Republic of Armenia and the Central Bank of the Republic of Armenia. The paper considers the key theoretical approaches to the policy on maintaining macroeconomic stability and the major tools of its implementation, identifies positive and negative consequences of this policy for Armenia’s economic growth. The analysis of the monetary, currency, and fiscal policies of the country proves that the policy of macroeconomic stability adopted during the last 10 years leads to the decreasing rates of economic growth, especially in the long run. The ambiguity of the said policy in terms of the efficiency and balance of its outcomes confirms the necessity to reconsider its relevance in the emerging economies.
A renaissance of interest in crystallographic shear structures and our recent work in this remarkable class of materials inspired this review. We first summarize the geometrical aspects of shear ...plane formation and possible transformations in ReO
3
, rutile, and perovskite-based structures. Then we provide a mechanistic overview of crystallographic shear formation, plane ordering, and propagation. Next we describe the energetics of planar defect formation and interaction, equilibria between point and extended defect structures, and thermodynamic stability of shear compounds. Finally, we emphasize the remaining challenges and propose future directions in this exciting area.
To evaluate the exposure to crisis leadership theory already present in Council on Education for Public Health (CEPH) accredited Master of Public Health (MPH) programs in the United States and ...provide a compelling case for its future inclusion.
This was a narrative review.
We compiled a comprehensive list of 179 CEPH schools that offered an MPH program. During January through March 2021, we examined 179 websites for the core courses and elective courses offered in the MPH degree program to determine if any courses covered the topics of leadership, crisis leadership, or crisis management in either the course title or description.
Leadership courses were available in only 55.31% of CEPH-accredited schools. Only a single program (0.56%) offers a crisis leadership course.
The current global COVID-19 pandemic and reality of climate-induced disasters have brought crises to the forefront for health systems. Successful leadership for the future requires public health leaders to have training in crisis leadership. The evaluation and revision of public health curricula must focus on leadership competency development to prepare graduates to lead complex multiple crisis events and system shocks simultaneously.
Modern anthropogenic warming changes all climatic characteristics: temperature, precipitation, cloudiness, duration of snow cover, etc.The article analyzes the impact of global climate change on the ...forest ecosystems of Krasnodar region. The conclusion about the moderately negative contribution of the climatic factor to the forecast dynamics of forestry is substantiated.
The article examines the specifics of operating power plants in special environmental control areas, following the restrictions of the International Maritime Organization introduced in 2020. It ...focuses on innovative technologies such as the use of low-sulphur fuels, the implementation of SCR technology, the development of new logistical solutions and the use of new fuels. The method for controlling the emission of sulphur oxides into the atmosphere from power plants must be an integrated one, combining primary and secondary measures. Primary activities include purification of fuel from pollutants - improvement of fuel quality (enrichment of feedstock, use of alternative fuels); suppression of formation of harmful substances during combustion by improving fossil fuel combustion processes (by improving furnace designs, technological methods and regime measures, organization of mixture formation and combustion processes, improvement of fuel injection system). Secondary measures include technologies for capturing pollutants from flue gases, including methods designed for coarse and fine flue gas cleaning (flue gas recirculation, catalytic flue gas cleaning, wet methods, dry methods, absorbers for the cleaning of combustion products of sulphur oxides, cyclone-foam apparatus). The solution to the pollution of the World ocean, and in particular the special environmental control zones, by sulphur emissions from diesel engines primarily depends on the development of highly effective technologies to reduce its concentration at the diesel plant outlet.
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