Optical models of the molecular atmosphere

The use of optical and laser methods for performing atmospheric investigations has stimulated the development of the optical models of the atmosphere. The principles of constructing the optical models of molecular atmosphere for radiation with different spectral composition (wideband, narrowband, and monochromatic) are considered in the case of linear and nonlinear absorptions. The example of the development of a system which provides for the modeling of the processes of optical-wave energy transfer in the atmosphere is presented. Its physical foundations, structure, programming software, and functioning were considered

A combined Raman lidar for low tropospheric studies

One of the main goals of laser sensing of the atmosphere was the development of techniques and facilities for remote determination of atmospheric meteorological and optical parameters. Of lidar techniques known at present the Raman-lidar technique occupies a specific place. On the one hand Raman lidar returns due to scattering on different molecular species are very simple for interpretation and for extracting the information on the atmospheric parameters sought, but, on the other hand, the performance of these techniques in a lidar facility is overburdened with some serious technical difficulties due to extremely low cross sections of Raman effect. Some results of investigations into this problem is presented which enables the construction of a combined Raman lidar capable of acquiring simultaneously the profiles of atmospheric temperature, humidity, and some optical characteristics in the ground atmospheric layer up to 1 km height. The operation of this system is briefly discussed

Crystal structure and oxygen content of the double perovskites GdBaCo 2-xFexO6-δ

The iron solubility limit, x, in GdBaCo2-xFexO 6-δ determined by means of X-ray diffraction was found to be close to 0.65 in air. The crystal structure changes of the double perovskites GdBaCo2-xFexO6-δ (x=0-0.6) were studied by means of in situ X-ray diffraction in temperature range from 25 to 900 °C in air. The oxygen content, 6-δ, was determined for these double perovskites in air as a function of temperature by means of thermogravimetric technique in range 25≤T, °C≤ 1100. The Pmmm-P4/mmm structure transition was found to occur in GdBaCo2-xFexO 6-δ (0≤x≤0.4) with increasing temperature. This transition is observed at the same temperature for the compositions with 0≤x≤0.1 while the transition temperature reaches maximum for x=0.2 and that decreases linearly with further iron increase. The double perovskite GdBaCo1.4Fe0.6O6-δ was shown to have the tetragonal P4/mmm structure at room temperature. The P4/mmm-Pmmm structure transition occurs at temperature as low as 170 °C for this double perovskite while reverse one is already observed at 290 °C in air. The Pmmm-P4/mmm structure transition was found to be strongly related to the oxygen content for the undoped and slightly doped (x≤0.2) double perovskites while there is no such relation for the double perovskites enriched by iron (x≥0.2). © 2012 Elsevier Inc. All rights reserved

Investigation of GdBaCo2-xFexO6-δ (x = 0, 0.2) - Ce0.8Sm0.2O2 composite cathodes for intermediate temperature solid oxide fuel cells

The double perovskites GdBaCo2-xFexO 6-δ (x = 0, 0.2) and composites (100 - y) GdBaCo 2-xFexO6-δ (x = 0, 0.2) - y Ce 0.8Sm0.2O2 (y = 10-50 wt.%) were investigated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Chemical compatibility of GdBaCo2-xFexO 6-δ (x = 0, 0.2) with solid electrolyte Ce0.8Sm 0.2O2, thermal expansion, DC conductivity and electrochemical performance of (100 - y) GdBaCo2-xFe xO6-δ (x = 0, 0.2) - y Ce0.8Sm 0.2O2 (y = 10-50 wt.%) were studied. Partial substitution of Fe for Co was shown to lead to decrease of double perovskite GdBaCo 2-xFexO6-δ reactivity with the solid electrolyte Ce0.8Sm0.2O2. Polarization resistance of cathodes studied was found to depend significantly on firing temperature. Variation of solid electrolyte content in (100 - y) GdBaCo 2-xFexO6-δ (x = 0, 0.2) - y Ce 0.8Sm0.2O2 (y = 10-50 wt.%) composites was shown to allow to optimize their electrochemical performance. Cathode materials of 80 wt.% GdBaCo2O6-δ - 20 wt.% Ce 0.8Sm0.2O2 and 65 wt.% GdBaCo 1.8Fe0.2O6-δ - 35 wt.% Ce 0.8Sm0.2O2 were found to have the lowest polarization resistances and reasonable values of thermal expansion coefficient (TEC) and, therefore, can be considered as promising cathode materials for IT-SOFCs. © 2013 Elsevier B.V. All rights reserved

Multifrequency dial sensing of the atmospheric gaseous constituents using the first and second harmonics of a tunable CO2 laser radiation

The results of field measurements of concentration of some gaseous components of the atmosphere along the paths, in Sofia, Bulgaria, using a gas analyzer based on the use of a CO2 laser radiation frequency-doubled with ZnGeP2 monocrystals are presented. The gas analyzer is a traditional long path absorption meter. Radiation from the tunable CO2 laser of low pressure and from an additional He-Ne laser is directed to a colliminating hundredfold Gregori telescope with a 300 mm diameter of the principal mirror. The dimensions of the mirrors of a retroreflector 500 x 500 mm and a receiving telescope allow one to totally intercept the beam passed through the atmospheric layer under study and back

Coherent lidars based on intracavity heterodyning of echo signals

The development and technical realization of the method of laser sounding of the atmosphere based on the effects of mixing of reference and external fields of scattering inside a laser cavity are presented. An approximate theory of the method was developed on the basis of the investigations using the model of a three-mirror laser. The nonlinear effect of a wideband laser on frequency-dependent external influences of the atmosphere was investigated. The field measurements of gaseous composition of the atmosphere were performed on the basis of a given method of coherent reception using a tunable CO2 laser

Properties of the amorphous-nanocrystalline Gd2O3 powder prepared by pulsed electron beam evaporation

An amorphous-nanocrystalline Gd2O3 powder with a specific surface area of 155 m2/g has been prepared using pulsed electron beam evaporation in vacuum. The nanopowder consists of 20- to 500-nm agglomerates formed by crystalline nanoparticles (3-12 nm in diameter) connected by amorphous-nanocrystalline strands. At room temperature, the Gd2O3 nanopowder exhibits a paramagnetic behavior. The phase transformations occurring in the powder have been investigated using differential scanning calorimetry and thermogravimetry (40-1400°C). The amorphous phase of the nanopowder is thermally stable up to a temperature of 1080°C. It has been found that the amorphous phase has an inhibitory effect on the temperature of the polymorphic transformation from the cubic phase into the monoclinic phase. It has been revealed that, compared with the microcrystalline powder, the Gd2O3 nanopowder is characterized by a complete quenching of photoluminescence. © 2013 Pleiades Publishing, Ltd

Physical properties of fluorides barium and calcium nanopowders produced by the pulsed electron beam evaporation method

The mesoporous nanocrystal powders BaF 2 and CaF 2 with a specific surface up to 34.8 and 88.7 sq.m/g, respectively, are produced by the pulsed electron beam evaporation method in vacuum. The influence of thermal annealing of nanoparticles on air in the range of temperature from 200 to 900°C on the size, morphology of particles and change of their magnetic and luminescent properties investigated have been investigared. The essential stoichiometric impurity (overage of metals) and significant growth in a specific surface of nanopowders (NP) BaF 2 and CaF 2 after annealing at the temperature of 200°C have been detected. It is established that the synthesized NP BaF 2 is a paramagnetic while initial material in the bulk state is diamagnetic. After annealing at 900°C appears the small ferromagnetic contribution at NP BaF 2 . Produced NP CaF 2 showed ferromagnetic behavior. In literature there is no information about the ferromagnetism of CaF 2 . Appearance of the ferromagnetic response can be explained with formation of structural and radiation defects (F-centers, etc.). The analysis of PCL and magnetization curves of samples BaF 2 and CaF 2 allows drawing conclusions about their connection. © Published under licence by IOP Publishing Ltd.The authors are grateful to Pryanichnikov S.V., a researcher of the shared equipment center “Ural” of the Institute of Metallurgy of the Ural division of RAS, for the X-ray phase analysis; to the researchers of the Institute of Electrophysics of the Ural division of RAS Demina T.M. for the texture analysis, Murzakayev A.M. and Timashenkova O.R. for the microscopic analysis, Spirina A.V. for the PCL analysis. This work has been carried out within the scope of government order No. 0389-2015-0026 and with partial support of RFBR project No. 18-08-00514. The magnetic measurements were carried out within the scope of government order under the topic MAGNIT, state registration No. AAAA-A18-118020290129-5

Oxygen content and thermodynamic stability of YBaCo2O6-δdouble perovskite

The thermodynamic stability of the double perovskite YBaCo2O6-δ was studied using the coulometric titration technique and verified by measurements of the overall conductivity depending on oxygen partial pressure at a given temperature. As a result, the stability diagram of YBaCo2O6-δ was plotted. YBaCo2O6-δ was found to be thermodynamically stable in air at 850°C and higher temperatures, whereas its thermodynamic stability at 900°C is limited by the range of oxygen partial pressures -3.56 ≤ log(pO2/atm) ≤ -0.14. Oxygen content in YBaCo2O6-δ slightly decreases at 900°C from 5.035 at log(pO2/atm) = -0.14 to 4.989 in the atmosphere with log(pO2/atm) = -3.565 indicating a crucial role which variation of Co+3/Co+2 ratio plays in its stability. YBaCo2O6-δ decomposes into the mixture of YCoO3 and BaCoO3-z at the high pO2 stability limit, whereas YBaCo4O7, BaCo1-xYxO3-γ, and Y2O3 were identified as the products of its decomposition at the low pO2 one. Copyright © 2018 Anton L. Sednev et al