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

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

ВЛИЯНИЕ МЕТОД А СПЕКАНИЯ НА МИКРОСТРУКТУРУ КЕРА МИКИ ND0,4SR1,6NIO

Two different methods have been employed for fabrication of Nd0.4Sr1.6NiO4–d ceramics with focus on the microstructure and density of ceramic samples. Conventional sintering at 1100–1300 °C has been found to yield porous materials. Rapid grain growth at ≥1 300 °C induces the development of microcracks associated with a strongly anisotropic expansion ofNd0.4Sr1.6NiO4–d tetragonal lattice. On the contrary, spark plasma sintering (SPS) at 1100 °C enables fabrication of dense gastight ceramics, but is accompanied by the structural transformation from tetragonal (I4/mmm) to orthorhombic (Immm) symmetry due to oxygen losses from the lattice under low-p(O2) conditions of SPS process. The post-treatment conditions were optimized to oxidize sintered samples and to restore tetragonal structure while preserving gas-tightness of ceramics.Исследовано влияние методов свободного спекания и плазменного искрового спекания (ПИС) на микроструктуру керамики Nd0,4Sr1,6NiO4–d. Установлено, что керамика, изготовленная свободным спеканием, является пористой независимо от температуры отжига. Керамика, полученная методом плазменного искрового спекания, – газоплот-ная. однако в результате применения восстановительной атмосферы вакуума в процессе ПИС происходит структурное превращение тетрагональной ячейки I4/mmm в орторомбическую Immm. В результате проведенной серии термообработок керамики были найдены оптимальные условия последующего отжига керамики, приводящие к восстановлению тетрагональной структуры оксида (Immm→I/4mmm) и сохранению газоплотности керамики Nd0,4Sr1,6NiO4–d

ТЕРМИЧЕСКОЕ РАСШИРЕНИЕ, ЭЛЕКТРИЧЕСКАЯ ПРОВОДИМОСТЬ И КИСЛОРОДНАЯ НЕСТЕХИОМЕТРИЯ НИКЕЛАТОВ La2-xSrxNiO4-δ КАК ПОТЕНЦИАЛЬНЫХ КАТОДНЫХ МАТЕРИАЛОВ TОТЭ

La2-xSrxNiO4-δ (x = 1.0–1.6) nickelates were evaluated as potential cathode materials for solid oxide fuel cells, with focus on the structural stability, oxygen nonstoichiometry and electrical conductivity under oxidizing conditions. All studied ceramic materials were found to preserve K2NiF4-type tetragonal structure under oxidizing conditions at 25–900  °С.La2-xSrxNiO4-δ (x = 1.0–1.6) nickelates demonstrate oxygen deficiency at temperatures above 500 °С, with oxygen nonstoichiometry increasing with temperature and strontium content. The electrical conductivity is p-type and show metallic-like behavior under oxidizing conditions at 500–1000 °С. The highest conductivity values, 220 S/cm at 900 °С and 440  S/cm at 600 °С in air, are measured for La0,8Sr1,2NiO4-δ ceramics. While the high-temperature XRD studies revealed strongly anisotropic thermal expansion of La2-xSrxNiO4-δ crystal lattice, the lattice volume show nearly linear dependence on temperature, with average linear thermal expansion coefficients varying in the range (14.2–15.6) · 10-6 K-1.Оксиды системы La2-xSrxNiO4-δ (x = 1,0–1,6) были исследованы в качестве  потенциальных катодных материалов для твердооксидных топливных элементов. Были изучены структурная стабильность, кислородная нестехиометрия и электрическая  проводимость. Установлено, что все оксиды сохраняют кристаллическую структуру типа K2NiF4 в окислительных условиях в температурной области 25–900 °С. Оксиды данной системы являются дефицитными по кислороду при температурах выше 500 °С, и  кислородная нестехиометрия повышается с ростом температуры и увеличением содержания стронция. Исследованные никелаты обладают псевдометаллической электропроводностью p-типа в окислительных условиях при температурах 500–1000 °С. Наибольшая электрическая проводимость характерна для La0,8Sr1,2NiO4-δ (220 См/см при 900 °С и 440 См/см при 600 °С). Методом высокотемпературной рентгеновской дифракции установлено, что никелаты La2-xSrxNiO4-δ проявляют анизотропное термическое расширение кристаллической решетки, однако объемное термическое расширение носит практически линейную зависимость от температуры; значения линейных коэффициентов термического расширения составляют (14,2–15,6) · 10-6 K-1

Can pulsed ultrasound increase tissue damage during ischemia? A study of the effects of ultrasound on infarcted and non-infarcted myocardium in anesthetized pigs

BACKGROUND: The same mechanisms by which ultrasound enhances thrombolysis are described in connection with non-beneficial effects of ultrasound. The present safety study was therefore designed to explore effects of beneficial ultrasound characteristics on the infarcted and non-infarcted myocardium. METHODS: In an open chest porcine model (n = 17), myocardial infarction was induced by ligating a coronary diagonal branch. Pulsed ultrasound of frequency 1 MHz and intensity 0.1 W/cm(2 )(I(SATA)) was applied during one hour to both infarcted and non-infarcted myocardial tissue. These ultrasound characteristics are similar to those used in studies of ultrasound enhanced thrombolysis. Using blinded assessment technique, myocardial damage was rated according to histopathological criteria. RESULTS: Infarcted myocardium exhibited a significant increase in damage score compared to non-infarcted myocardium: 6.2 ± 2.0 vs. 4.3 ± 1.5 (mean ± standard deviation), (p = 0.004). In the infarcted myocardium, ultrasound exposure yielded a further significant increase of damage scores: 8.1 ± 1.7 vs. 6.2 ± 2.0 (p = 0.027). CONCLUSION: Our results suggest an instantaneous additive effect on the ischemic damage in myocardial tissue when exposed to ultrasound of stated characteristics. The ultimate damage degree remains to be clarified

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

ECMO for COVID-19 patients in Europe and Israel

Since March 15th, 2020, 177 centres from Europe and Israel have joined the study, routinely reporting on the ECMO support they provide to COVID-19 patients. The mean annual number of cases treated with ECMO in the participating centres before the pandemic (2019) was 55. The number of COVID-19 patients has increased rapidly each week reaching 1531 treated patients as of September 14th. The greatest number of cases has been reported from France (n = 385), UK (n = 193), Germany (n = 176), Spain (n = 166), and Italy (n = 136) .The mean age of treated patients was 52.6 years (range 16–80), 79% were male. The ECMO configuration used was VV in 91% of cases, VA in 5% and other in 4%. The mean PaO2 before ECMO implantation was 65 mmHg. The mean duration of ECMO support thus far has been 18 days and the mean ICU length of stay of these patients was 33 days. As of the 14th September, overall 841 patients have been weaned from ECMO support, 601 died during ECMO support, 71 died after withdrawal of ECMO, 79 are still receiving ECMO support and for 10 patients status n.a. . Our preliminary data suggest that patients placed on ECMO with severe refractory respiratory or cardiac failure secondary to COVID-19 have a reasonable (55%) chance of survival. Further extensive data analysis is expected to provide invaluable information on the demographics, severity of illness, indications and different ECMO management strategies in these patients