Double perovskite oxides BaGd0.8La0.2Co2O6−δ (BGLC), BaGdCo1.8Fe0.2O6−δ (BGCF), BaPrCo2O6−δ (BPC) and BaPrCo1.4Fe0.6O6−δ (BPCF) were investigated as oxygen electrodes on mixed conducting ...BaZr0.7Ce0.2Y0.1O3 (BZCY72) electrolyte using impedance spectroscopy vs temperature, pO2, and pH2O. We propose and have applied a novel approach to extract and parameterise the charge transfer and diffusion impedances of the electrode reactions in a system comprising charge transport of protons, oxide ions, and electrons. Given by the properties of the BZCY72, transport of protons dominates at lower temperatures and high pH2O, oxide ions at higher temperatures, and electron holes increasingly at high temperatures and high pO2. The electrodes showed good performance, with the lowest total apparent polarisation resistance for BGLC/BZCY72 being 0.05 and 10Ωcm2 at 650 and 350°C, respectively. The low temperature rate limiting reaction step is a surface related process, involving protonic species, with an activation energy of approximately 50kJmol−1 for BGLC/BZCY72. The oxide ion transport taking over at higher temperatures exhibits a higher activation energy typical of SOFC cathodes. Thermogravimetric studies revealed that BGLC exhibits considerable protonation at 300–400°C, which may be interpreted as hydration with an enthalpy of approximately –50kJmol−1. The resulting mixed proton electron conduction may explain its good performance as electrode on BZCY72.
•Novel oxygen electrode for Proton Ceramic Fuel Cells•Hydration of mixed conducting perovskite•Modelling of electrode reactions for protons and oxide ions at the oxygen electrode•Correcting for partial electronic conductivity under characterization conditions•Polarisation resistance of 0.05 and 10Ωcm2 at 650 and 350°C, respectively
•Enthalpies of solution of hybrid perovskites CH3NH3PbX3 (X=Cl, Br, I) in DMSO were measured using solution calorimetry.•Standard enthalpies and Gibbs free energies of formation of CH3NH3PbX3 (X=Cl, ...Br, I) from halides were calculated on the basis of experimental data.•Entropy contribution was shown to play a major role in the stability of hybrid organic–inorganic perovskites.
Enthalpies of solution of hybrid perovskites CH3NH3PbX3 (X=Cl, Br, I) in DMSO were measured using solution calorimetry. Standard enthalpies and Gibbs free energies of formation of CH3NH3PbX3 (X=Cl, Br, I) hybrid perovskites from halides as well as from elements at 298K were calculated on the basis of experimental data obtained and compared with the data available in literature. Excellent agreement was obtained between the standard Gibbs free energy of decomposition of CH3NH3PbX3 into solid PbX2, gaseous HX and methylamine calculated on the basis of our data and that evaluated on the basis of vapor pressure measurement results reported by other authors. Entropy contribution was shown to play a major role in the stability of hybrid organic–inorganic perovskites with respect to their decomposition on constituent halides.
We suggest a novel class of active nanoantennas based on diamond nanoparticles with embedded nitrogen-vacancy centres coupled to Mie resonances of nanoparticles. We theoretically study the optical ...properties of such nanoantennas including the field enhancement and Purcell effect, and experimentally demonstrate the enhancement of the fluorescence rate of the emitters due to particle resonances, as compared to a nonresonant regime. Our results pave the way towards active dielectric nanophotonics for quantum light sources, bioimaging, and quantum information processing.
The localization behavior of plastic flow was investigated for a range of pure metals and alloys. The localized plastic flow is regarded as an autowave process having a fixed set of features, i.e. ...propagation rate, wave number and dispersion law. Using the method of speckle photography, the autowave propagation rate has been determined experimentally for the stage of linear work hardening. Moreover, a dispersion relation of quadratic form and wave number dependencies of phase and group rates have been derived for localized plastic flow autowaves. A detailed quantitative comparison is made of the phase and group rates of the autowaves. This suggests that the two types of wave rates are closely related.
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•The displacement vector fields are recorded using the speckle photography method.•The local strain pattern is defined by the work hardening law acting of flow stage.•The localization patterns are viewed as different types of autowave processes.•The dispersion relation has quadratic form and describes nonlinear processes.
For the first time, the defect structure of mayenite was developed on the basis of conventional Kröger–Vink method and successfully verified using available data on its properties such as total ...conductivity, hydration/dehydration and oxidation/reduction. As a consequence, equilibrium constants of the quasichemical reactions of mayenite reduction and hydration were determined as a function of temperature. This allowed estimation of Ca12Al14O33−δ enthalpy of reduction and hydration. The former was found to be equal to 360kJ/mol while the latter was estimated as −238kJ/mol. The defect structure model proposed enabled estimation of oxygen nonstoichiometry in mayenite.
•High temperature red/ox behavior and hydration of mayenite was modeled.•Conventional Kröger–Vink method was successfully applied.•Mayenite enthalpy of reduction was found to be equal to 360kJ/mol.•Mayenite hydration enthalpy was found to be equal to −238kJ/mol.•Mayenite oxygen nonstoichiometry was estimated.
Two-stage compression of laser pulses with a power of 250 TW is experimentally realised by broadening their spectrum during self-phase modulation in fused silica and subsequent dispersion ...compensation upon reflection from chirping mirrors. A five-fold decrease in the duration is demonstrated, from 75 to 15 fs, with a B-integral value of about 5 at each stage. It is possible to avoid small-scale self-focusing due to self-filtering of the laser beam during free propagation in vacuum. With optimal parameters of the dispersive mirror, the pulse can be compressed to a duration of less than 5 fs.
We have developed the design and experimentally studied aperiodic and stack broadband Mo/Si mirrors for the purposes of the KORTES project, optimised for uniform reflection in the 17 - 21 nm ...wavelength range. It is shown that stack structures with an insignificant loss in the reflection coefficient are much more preferable from the point of view of manufacturing and certification, which, in turn, makes it possible to correct the deposition process and to reach the calculated parameters of a multilayer mirror in a small number of iterations.
A series of new liquid crystalline oligomers based on 1,6-hexamethylene diisocyanate and its di- or trimers (uretdione, biuret, or isocyanurate) and 4′-ω -hydroxyalkyl-4-cyano-biphenyls was ...synthesized. The resulting set of oligomers is a structural model for liquid crystalline polymers containing mesogenic groups in the main and side chains, as well as star polymers. Mesomorphic properties of the oligomers were evaluated using differential scanning calorimetry and polarization optical microscopy. Structure and dipole architecture of the central unit of synthesized oligomers cause a decisive influence on their mesomorphic properties. The formation of network of interchain hydrogen bonds significantly stabilized the liquid crystalline state, which was confirmed by IR spectroscopy.
