Composite LnNiO3+PrOx oxygen electrodes for solid oxide cells

Ln2NiO4+δ and its derivatives with perovskite-related K2NiF4-type structure demonstrate high mixed ionic-electronic conductivity, moderate thermal and negligible chemical expansion. As a result, these phases attracted significant attention as prospective cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFC). At the same time, perovskite-like LnNiO3 has not been considered for these applications, mostly due to the limited phase stability under ambient oxygen pressures. On heating in air, LaNiO3 decomposes at ~ 1000°C; cathodic polarization can be expected to induce the decomposition of perovskite phase at lower temperatures characteristic for IT-SOFC operation. On the contrary, redox changes imposed by anodic polarization (in solid oxide electrolysis cell mode) under oxidizing conditions should not be of risk for the phase stability of LaNiO3. The goal of the present work was the evaluation of LnNiO3-based oxygen electrodes for solid oxide fuel/electrolysis cells. The LnNiO3-δ ceramic powders with perovskite-like structure was prepared by glycine-nitrate combustion synthesis followed by calcinations in oxygen atmosphere at 800-1000°C. Porous ceramic samples for electrical and dilatometric studies were sintered in oxygen at 950-1050°C. Porous LaNiO3-δ samples were found to exhibit favorably high p-type metallic-like electrical conductivity, 400-500 S/cm at 800-600°C in air. These ceramics demonstrated also a moderate thermal expansion, with average CTE ~ 13.0 ppm/K at 25-800°C, ensuring thermomechanical compatibility with solid electrolytes. As a first step, the electrochemical performance of LaNiO3-δ electrodes was assessed in contact with three common electrolytes including (ZrO2)0.92(Y2O3)0.08 (8YSZ), Ce0.9Gd0.1O2-δ (CGO10) and (La0.8Sr0.2)0.98Ga0.8Mg0.2O3-δ (LSGM). The electrode layers were sintered at 1050°C for 2 h under oxygen flow. The studies of symmetrical cells by EIS demonstrated that the electrochemical activity of LaNiO3-δ electrodes increases in the sequence 8YSZ < CGO10 < LSGM; the corresponding values of electrode polarization resistance (Rη) at 800°C were 1.4, 0.8 and 0.25 Ohm×cm2, respectively. Significant variations of Rη with electrolyte composition correlate with the extent of chemical reactivity between LaNiO3-δ and electrolyte materials during the electrode fabrication. The Rη values of LaNiO3-δ electrodes in contact with LSGM electrolyte were further reduced to 0.03 Ohm×cm2 at 800°C and 0.11 Ohm×cm2 at 700°C by the surface modification with PrOx which is known for its electrocatalytic activity. At 750°C and current density of 0.5 A/cm3, LaNiO3+PrOx (~20 wt.%) electrodes in contact with LSGM solid electrolyte demonstrate the overpotentials of ~60 mV under cathodic polarization and ~40 mV under anodic polarization (Fig.1). The impact of substitution of lanthanum by praseodymium (in order to improve the chemical compatibility and electrochemical activity) on the relevant properties of LnNiO3 is briefly discussed.publishe

Perovskite-like LaNiO3-δ as oxygen electrode material for solid oxide electrolysis cells

Perovskite-like LaNiO3-δ was evaluated as potential oxygen electrode material for solid oxide electrolysis cells. Compared to the Ruddlesden-Popper Lan+1NinO3n+1 (n = 1,2,3) counterparts, LaNiO3-δ exhibits higher p-type metallic-like conductivity under oxidizing conditions (450 S×cm-1 at 800°C for highly porous ceramics) together with a moderate thermal expansion coefficient (13.7 ppm×K-1 in air at 25-800°C) compatible with common solid electrolytes. The measured electrode polarization resistance (Rη) in contact with YSZ, CGO and LSGM solid electrolytes was 1.4, 0.77 and 0.22 Ω×cm2 at 800°C, and 208, 123 and 7.1 Ω×cm2 at 600°C, respectively, under zero-current conditions in air. Surface modification of via PrOx infiltration resulted in lower values of Rη (0.024 Ω×cm2 at 800°C and 0.76 Ω×cm2 at 600°C) and low anodic overpotentials (20 mV at 800°C and 500 mA×cm-2) in contact with LSGM.publishe

Політичний сайт як посередник між суб'єктами політики та суспільством

У тезах розкрито роль глобальної мережі Інтернет у процесах взаємодії між політичними структурами та суспільством, а також з 'ясовано сутність концепції е-демократії як однієї із стратегій підтримки демократичних засад. Головна увага зосереджена на дослідженні особливостей використання вітчизняними політичними партіями можливостей Інтернет. При цьому проаналізовано зміст сайтів українських політичних партій та оцінено якість їхнього інформаційного наповнення. (The role of the World Wide Web in the processes of interaction between political structures and society is reviewed in the theses and also the notion of e-democracy as the strategy of democratic base's supporting is explained. Research of the usage of Internet possibilities by native political parties is the main focus of the work. Beside this, the content of the sites of Ukrainian political parties is analyzed and the quality of their information essence is evaluated.

Heat Treatment Effect on Magnetic Microstructure of Fe73.9Cu1Nb3Si13.2B8.9 Thin Films

Fe73.9Cu1Nb3Si13.2B8.9 (Finemet) thin films were deposited on the glass substrates by means of radio frequency sputtering. The films thickness was varied from 10 to 200 nm. Heat treatment at temperatures of 350, 400 and 450 °C were performed for 30 minutes in order to control thin film structural state. The X-ray powder diffractometry revealed that the crystallization of α-FeSi nanograins took place only at 450 °C whilst the other samples stayed in the amorphous state. Relation between the structure and magnetic properties of the films was discussed in the framework of random magnetic anisotropy model and the concept of stochastic magnetic domains. The latter was investigated using magnetic force microscopy (MFM). MFM data showed formation of such magnetic domains only in samples thermally treated at 450 °C. There was a tendency of the magnetic domain size reduction with the thickness decrease. © 2018 The Authors, published by EDP Sciences.The research was supported by the Ministry of Education and Science of the Russian Federation Agreement no. 02.A03.21.0006 and project no. 3.6121.2017

РЕНТА ЯК ФІНАНСОВИЙ ІНСТРУМЕНТ РЕГУЛЮВАННЯ РОЗВИТКУ АГРАРНОГО СЕКТОРУ ЕКОНОМІКИ

The development of the agrarian sector of the economy, as well as of the entire national economy, should be based on a clear and consistent state regulatory policy. Rent is one of the most effective financial instruments for regulating the development of the agrarian sector. As a whole, rent is defined as the income of any resources (production factors) owner that is not related to business activity. Onwards, economic rent is an over-income that the owner receives from using a variety of quality resources, the supply of which is limited in the long run. From the financial point of view, rent is part of the entrepreneur’s income, his unearned income. The consequence of excessive and uncontrolled macro-level rent-seeking behavior is the so-called «Dutch disease», which causes concentration of labor and capital in the services sector, its outflow from the real economy and the simultaneous replacement with unproductive inputs. It is determined that the rent saturation of the GDP of Ukraine exceeds the world average values, that designates the national economy as a commodity one, testifies to the developmental, transitive nature of the economy, its direct dependence on the developed countries. Moreover, the dynamics of the annual indices of the physical volume of Ukraine’s GDP coincides with the dynamics of its rent withdraw, which shows the direct dependency of goods production and rent, thus defining the economic system as extensive and reindustrialized. It is proved that amid non-renewable natural resources depletion, the economy of Ukraine is losing its potential and without drastic transformations, changes in technological structure and development of vertical integration, the crisis will only deepen. The implementation of the proposed measures will contribute to the return of rental over-income to those who have a constitutional right to get it, will provide additional financial resources to fulfill local budgets, especially rural territorial communities.Розвиток аграрного сектору економіки, як і всього національного господарства, має базуватися на чіткій і послідовній державній регуляторній політиці. Одним із найефективніших фінансових інструментів регулювання розвитку аграрного сектору економіки є рента. Показано, що в цілому під рентою розуміють дохід власника будь-яких ресурсів (факторів виробництва), що не пов’язаний із підприємницькою діяльністю. Економічна рента, своєю чергою, — це наддохід, що одержує власник від використання різноякісних ресурсів, пропозиція яких обмежена у довгостроковій перспективі. З фінансового погляду рента є частиною прибутку підприємця, його нетрудового доходу. Наслідком надмірної і неконтрольованої ренторієнтованої поведінки на макрорівні є так звана «голландська хвороба», що призводить до концентрації праці й капіталу у сфері послуг, його відпливу з реального сектору економіки і одночасним заміщенням непродуктивними факторами виробництва. Установлено, що рентна насиченість ВВП України перевищує середньосвітові значення, що характеризує національну економіку як рентно-сировинну, свідчить про розвитковий, транзитивний характер економіки, її пряму залежність від розвинутих країн. До того ж динаміка річних індексів фізичного обсягу ВВП України збігається з динамікою її рентного наповнення, що показує пряму залежність виробництва економічних благ і рентовидобування, тому характеризує економічну систему як екстенсивну й деіндустріалізовану. Доведено, що на тлі вичерпності невідновлювальних природних ресурсів економіка України втрачає свій потенціал і без радикальних трансформацій, зміни технологічного укладу й розвитку вертикальної інтеграції, криза тільки поглиблюватиметься. Реалізація запропонованих заходів сприятиме поверненню рентного наддоходу тим, хто має на нього конституційне право, забезпечить додаткові фінансові ресурсу для наповнення місцевих бюджетів, особливо сільських територіальних громад

Oxygen-deficient Nd0.8Sr1.2Ni0.8M0.2O4-δ (M = Ni, Co, Fe) nickelates as oxygen electrode materials for SOFC/SOEC

Ruddlesden-Popper Nd0.8Sr1.2Ni0.8M0.2O4±δ (M = Ni, Co, Fe) nickelates have been characterized as prospective oxygen electrode materials for solid electrolyte cells. XRD studies showed that these oxides retain tetragonal K2NiF4-type structure in air until at least 900°C. Average thermal expansion coefficients of Nd0.8Sr1.2Ni0.8M0.2O4±δ calculated from the structural data are in the range 14.5-15.8 ppm/K. TGA studies revealed that these nickelates are oxygen-deficient in air at temperature above 700°C but tends to oxygen stoichiometry or minor excess on cooling. Incorporation of cobalt or iron into nickel sublattice of Nd0.8Sr1.2NiO4-δ reduces oxygen deficiency and electrical conductivity. Electrochemical impedance spectroscopy studies of symmetrical cells showed that porous Nd0.8Sr1.2Ni0.8M0.2O4-δ electrodes applied onto Ce0.9Gd0.1O2-δ electrolyte exhibit quite similar performance, with lowest values of polarization resistance (0.8 Ohm×cm2 at 800°C) observed for M = Ni. The polarization resistance can be further decreased (down to 0.04 Ohm×cm2 at 800°C for M = Ni) by surface modification with PrOx.publishe

Oxygen-deficient perovskite-related (Nd0.4Sr0.6)2Ni0.8M0.2O4-δ as oxygen electrode materials for SOFC/SOEC

Perovskite-related Ln2NiO4+δ (Ln = La, Pr, Nd) nickelates with layered Ruddlesden-Popper combine redox stability with noticeable oxygen stoichiometry changes, yielding enhanced mixed transport and electrocatalytic properties. These unique features are promising for applications as oxygen electrodes with good electrochemical performance in reversible SOFC/SOEC (solid oxide fuel/electrolysis cell) systems. To date, most efforts were focused on oxygen-hyperstoichiometric Ln2NiO4+δ-based phases, whereas nickelates with oxygen-deficient lattice remain poorly explored. Recent studies demonstrated that the highest electrical conductivity in (Ln2-xSrx)2NiO4±δ series at elevated temperatures is observed for the compositions containing ~ 60 at.% of strontium in A sublattice [1,2]. The present work was focused on the characterization of (Nd0.4Sr0.6)2Ni0.8M0.2O4-δ (M = Ni, Co, Fe) nickelates for the possible use as materials for reversible oxygen electrodes. The ceramic materials were prepared by Pechini method with repeated annealings at 650-1200°C and sintered at 1250-1300°C for 5 h under oxygen atmosphere. Variable-temperature XRD studies confirmed that all studied compositions retain tetragonal K2NiF4-type structure in the temperature range 25-900°C. The results of thermogravimetric analysis showed that the prepared nickelates has oxygen-deficient lattice under oxidizing conditions at temperatures above 700°C. Partial substitution of nickel by cobalt or iron results in a decrease of p-type electronic conductivity and the concentration of oxygen vacancies in the lattice (Fig.1), but also suppresses dimensional changes associated with microcracking effects (due to anisotropic thermal expansion of tetragonal lattice). Electrochemical performance of porous (Nd0.4Sr0.6)2Ni0.8M0.2O4-δ electrodes in contact with Ce0.9Gd0.1O2-δ solid electrolyte was evaluated at 600- 800°C employing electrochemical impedance spectroscopy and steady-state polarization (anodic and cathodic) measurements.publishe

PrOx-infiltrated LnNiO3-based oxygen electrodes for solid oxide cells

Ln2NiO4+δ and its derivatives with perovskite-related K2NiF4-type structure demonstrate high mixed ionic-electronic conductivity, moderate thermal and negligible chemical expansion. As a result, these phases attracted significant attention as prospective cathode materials for intermediatetemperature solid oxide fuel cells (IT-SOFC). At the same time, perovskite-like LnNiO3 have not been considered for these applications, mostly due to the limited phase stability under ambient oxygen pressures. On heating in air, LaNiO3 decomposes at ~ 1000°C; cathodic polarization can be expected to induce the decomposition of perovskite phase at lower temperatures characteristic for IT-SOFC operation. On the contrary, redox changes imposed by anodic polarization (in solid oxide electrolysis cell mode) under oxidizing conditions should not be of risk for the phase stability of LaNiO3. The goal of the present work was the evaluation of LnNiO3-based oxygen electrodes for solid oxide fuel/electrolysis cells. The LnNiO3-δ ceramic powders with perovskite-like structure was prepared by glycine-nitrate combustion synthesis followed by calcinations in oxygen atmosphere at 800-1000°C. Porous ceramic samples for electrical and dilatometric studies were sintered in oxygen at 950-1050°C. Porous LaNiO3-δ samples were found to exhibit favorably high p-type metallic-like electrical conductivity, 400-500 S/cm at 800-600°C in air. These ceramics demonstrated also a moderate thermal expansion, with average CTE ~ 13.0 ppm/K at 25-800°C, ensuring thermomechanical compatibility with solid electrolytes. As a first step, the electrochemical performance of LaNiO3-δ electrodes was assessed in contact with three common electrolytes including (ZrO2)0.92(Y2O3)0.08 (8YSZ), Ce0.9Gd0.1O2-δ (CGO10) and (La0.8Sr0.2)0.98Ga0.8Mg0.2O3-δ (LSGM). The electrode layers were sintered at 1050°C for 2 h under oxygen flow. The studies of symmetrical cells by EIS demonstrated that the electrochemical activity of LaNiO3-δ electrodes increases in the sequence 8YSZ < CGO10 < LSGM; the corresponding values of electrode polarization resistance (Rη) at 800°C were 1.4, 0.8 and 0.25 Ohm×cm2 , respectively. Significant variations of Rη with electrolyte composition correlate with the extent of chemical reactivity between LaNiO3-δ and electrolyte materials during the electrode fabrication. The Rη values of LaNiO3-δ electrodes in contact with LSGM electrolyte were further reduced to 0.03 Ohm×cm2 at 800°C and 0.11 Ohm×cm2 at 700°C by the surface modification with PrOx which is known for its electrocatalytic activity. At 750°C and current density of 0.5 A/cm2 , LaNiO3+PrOx (~20 wt.%) electrodes in contact with LSGM solid electrolyte demonstrate the overpotentials of ~60 mV under cathodic polarization and ~40 mV under anodic polarization. The impact of substitution of lanthanum by praseodymium (in order to improve the chemical compatibility and electrochemical activity) on the relevant properties of LnNiO3 is briefly discussed.publishe