K. A. Kuterbekov

Effect of structural parameters of Ni-ScSZ cermet components on the SOFC anodes characteristics

The effect of the degree of dispersion and the ratio of initial components of metalloceramic composites based on Ni and Sc2O3-stabilized ZrO2 (Ni/ScSZ) on the kinetics of sintering, conductivity, and polarization resistance of the corresponding anodes in solid-oxide fuel cells (SOFC) is studied. The composites are prepared from nano- and submicrosized powders of NiO and ScSZ (10.5 mol % Sc2O3) containing particles with the average size of 0.02–0.33 μm. Anode composites of three types differing in the ratio of initial components (NiO-ScSZ) with different degrees of dispersion: micro-micro, nano-micro, and nano-nano are studied. Due to the ratio of particle sizes, the anodic composites of the nano-nano type demonstrate the preferential electronic conduction (the percolation threshold) starting from the Ni content of about 35 vol %, in contrast to the other two types of anodic composites for which this threshold is achieved at 30 vol %. The lowest polarization resistance is typical of anode composites with the Ni content of about 40 vol %. The use of one or both components in the nanosized state makes it possible to decrease the anodic polarization up to two times. It is demonstrated that an active cermet anode for SOFC can be fabricated in the form of a planar three-layer structure Ni/ScSZ-ScSZ-Ni/ScSZ prepared from nanosized powders by the tape casting technique and cosintering.

Influence of the cation sublattice defectness on the electronic thermoelectric power of Li x Cu(2−x)−δ (x ≤ 0.25)

This paper presents an experimental study of the electronic thermoelectric power as a function of copper content for LixCu(2−x)−δS (x ≤ 0.25) electronic-ionic mixed conductors. Using a vacancy model for lattice defects, we calculate their electronic thermoelectric power as a function of x. By adjusting the hole effective mass, we reach satisfactory agreement with experimental data.

Transport phenomena in superionic Na х Cu2 − х S (х = 0.05; 0.1; 0.15; 0.2) compounds

The electronic and ionic conductivity, the electronic and ionic Seebeck coefficients, and the thermal conductivity of NaxCu2xa0−xa0xS (xxa0=xa00.05, 0.1, 0.15, 0.2) compounds were measured in the temperature range of 20–450xa0°С. The total cationic conductivity of Na0.2Cu1.8S is about 2xa0S/cm at 400xa0°С (the activation energyxa0≈xa00.21xa0eV). Over the studied compounds, the composition Na0.2Cu1.8S has the highest electronic conductivity (500–800xa0S/cm) in the temperature range from 20 to 300xa0°С, and the highest electronic Seebeck coefficient (about 0.2xa0mV/K) in the same temperature range is observed for Na0.15Cu1.85S composition; the electronic Seebeck coefficient increases abruptly above 300xa0°С for all compounds. The thermal conductivity of superionic Na0.2Cu1.8S is low, which causes high values of the dimensionless thermoelectric figure of merit ZT from 0.4 to 1 at temperatures from 150 to 340xa0°С.

Synthesis and properties of solid electrolyte Ce0.9Gd0.1O2–δ with Co, Cu, Mn, Zn doping

The influence of small additions (1, 3, 5 mol %) of transition metal (Co, Cu, Mn, Zn) oxides on the properties of solid electrolyte Ce0.9Gd0.1O2–δ (GDC) have been investigated. It has been shown that the addition of dopants results in intensification of GDC sintering and reduction of the shrinkage end temperature by 300–400°C, which decreases in the sequence Zn–Mn–Co–Cu. The ultimate dopant concentration above which the further activation of GDC sintering does not occur is about 3 mol % for Co, Cu, and Mn and about 1 mol % for Zn. It has been shown that Co and Cu increase the total conductivity of GDC, while Mn and Zn decrease it.

Integrated Ecological Survey of the Tailing Ponds of Koshkar-Ata

The main purpose of this work is a comprehensive study of the environmental situation prevailing in the areas located near the tailing ponds of Koshkar-Ata and the development of rehabilitation events, taking into account the soil and climatic features of the area.

Pore-Forming Agents for the Supporting Ni-Based SOFC Anode

The effect of the type (semolina, starch, and ashless filter paper) and amount (5 and 10 wt %) of pore-forming agents on the structure of supporting Ni-cermet anodes and characteristics of solid-oxide fuel cells on their basis has been studied. It has been found that the use of paper fibers as the pore-forming agent doubles the open porosity of the anode as compared with equal amounts of semolina or starch. It has been shown that the long cylindrical pores formed by fibers allow fast transport of gases through the anode bulk, which has a positive effect on the fuel cell characteristics.

Electronic and ionic zeebeck coefficients in mixed conductors of Ag0.25–δCu1.75Se, Ag1.2–δCu0.8Se

The paper presents the studies of ionic and electronic Zeebeck coefficients and electronic conductivity in nonstoichiometric Ag0.25–δCu1.75Se, Ag1.2–δCu0.8Se solid solutions existing on the basis of the cubic phase of copper selenide. It is shown that Ag1.2–δCu0.8Se is a bilateral variable composition phase manifesting inversion of the sign of predominant charge carriers under variation of the chemical composition by silver within the homogeneity region. Mobilities of electrons and electron holes are estimated on the basis of the concentration dependences.

Microhardness and fracture toughness of ZrO2–Sc2O3 solid electrolyte, doped with rare-earth and transition metals

The influence of low concentrations (1 mol %) of co-dopants (Y, Ce, Gd, Er, La, Zn, Mn, Co and Cu) on the microhardness and fracture toughness of Zr0.81Sc0.19O2–δ (10.5ScSZ) solid electrolyte was studied by the indentation method. It was shown that co-doping of 10.5ScSZ by the rare-earth elements (Y, Ce, Gd, Er) results in microhardness increase on 4–45% due to stabilization of cubic phase in the grains, while the microhardness changing upon transition metals (Mn, Cu, Co, Zn) introduction is caused by the grain boundaries modification. The microhardness decreases on ~4 and 10% upon doping by Mn and Cu, accordingly, whereas the introduction of Co and Zn results in its increase approximately by 2 times. It was shown also that the influence of all investigated dopants on the fracture toughness is insignificant. The maximal effect observed for Cu was the fracture toughness increase from 2.1 up to 2.6 MPa m0.5.

Luminescent materials based on nanoparticles of silicon dioxide for solar cells

The report considers luminescent mesoporous silica dioxide particles of activated RE ions and lead sulfide nanocrystals of different sizes. For the purpose of assessing the possibility of converting by lead sulfide nanoclusters of solar radiation into the red-orange light, the following methods will be drawn to the attention: mesoporous silica particles sol-gel synthesis, additional light scattering method as an additional approach for the determination of particle size. The element composition of a particle size of 300 ± 40 nm was identified using the scanning electron microscope with the system of energy disperse analysis. Particle images were obtained using the field scanning electron microscope. Zeta Potential Analyzer was used to measure the surface charge of the particles. Particles in solution were excited by near ultraviolet and visible light. The intensity of intrinsic emission was registered in the range of 400–550 nm. The diagnosis made visible the electron induced energy transmission from the matrix to the Eu3+ and Tb3+. Emission of Eu3+ and Tb3+ has been registered at 300K. It is assumed that the identical matrixes could work as converters of solar emission spectrum, to which some solar cells are sensitive.