The results of an experimental study of the optical characteristics and microstructure of the dispersed phase of the products of combustion of organic fuel in oxygen and atmospheric air are analyzed. ...For gaseous fuels CmHn, the concentration of soot sol increases with an increase in the ratio of elements Cm / Hn. The microstructure of soot sol strongly depends on the residence time of the combustion products in the flame zone (chemical reaction zone) and the thermodynamic temperature. The maximum ash content is observed at thermodynamic temperatures of 1500-1800K zone of chemical reactions. The minimum ash content is observed when burning fossil fuels in oxygen with a value of the coefficient of excess oxygen α = 1,03. A technique is proposed for measuring the microstructure of soot sol in atmospheric emissions of the combustion products of turbojet engines, vehicles, and power plants. The results of studies of the microstructure of the dispersed phase of fuel combustion products are used to calculate the light scattering matrices of carbon black sol according to the Mi theory. The radiation characteristics of soot sols are simulated by their superposition for different fractions i of the sol microstructure with normalization to optical density |τi| and a wavelength of λ = 0.55mkm. The optical densities |τi| for λ=0,55mkm for components i are given in numerical form depending on the height z in the combustion chamber. The radiation characteristics (absorption, scattering cross section and scattering indicatrix) are presented in the spectral region of 0.2-40mkm in the form of an electronic computer database for various gamma distributions of the carbon structure of soot sol.
In this work, we synthesized the glasses of the SiO
2
–Al
2
O
3
–CaO–Na
2
O–MgO–K
2
O–B
2
O
3
–Y
2
O
3
system and investigated their thermal properties under changes in the ratios between the ...components in both modifying (MgO/CaO) and glass-forming (SiO
2
/B
2
O
3
) oxides. In addition, the effects of crystallization on both the properties of sealants and their behaviour at the boundary with ceramic yttria-stabilized zirconia (YSZ) electrolyte have been studied. X-ray diffraction analysis was used to determine the phase composition of the glasses both after quenching, dilatometric measurements and sealing of the glasses with the YSZ ceramic support. The thermal expansion coefficients (CTEs) found for the glasses and glass–ceramics are shown to be in good agreement with those of other cell components. The sealing temperatures of these materials are found to be lower than the operating temperature limit of the interconnector alloy. It is shown that Mg-rich glasses exhibit higher resistance to interaction with Cr compared to other compositions under study. The scanning electron microscopy and energy dispersive spectroscopy studies have confirmed the formation of gas-tight connections by the sealants under investigation. The glass demonstrating the highest stability in contact with the Crofer22APU alloy has been tested as a sealant for a tubular cell. This material is established to ensure a tight connection without cracks during operation at 850 °C for 250 h. The materials are thus found to be promising candidates for use as sealants for solid oxide fuel cells (SOFCs).
The results of long-term experimental studies of the spectral radiation characteristics of the gas phase of the combustion products, performed on measuring complexes of medium and high spectral ...resolution in the temperature range 200-2800 K, are carried out. The spectral transmission functions are parametrized by the two-parameter equivalent mass method, which makes it possible to solve radiation heat transfer problems in structurally inhomogeneous high - temperature multicomponent gas environments of the products of combustion of energy fuels of the combustion chambers of energy units to generate thermal and electrical energy. The results of modeling radiation heat transfer in combustion chambers and heat exchangers of multi - chamber furnaces with hearth multi-row burner devices and bottom feeding of solid fuel combustion products into a radiation heat exchanger from cyclone furnaces are discussed.
The formation of microporous metal structures during the electrochemical dealloying of a single-phase Ag
0.58
Au
0.37
Pd
0.05
alloy in the following molten salts is investigated: in the LiCl
0.57
...CsCl
0.26
KCl
0.17
at a temperature of 306°C and in CsCl
0.455
KCl
0.245
NaCl
0.30
+ 3 mol % AgCl at 510, 600, 700, and 815°C. The electrolysis potentials are chosen using potentiodynamic curves. As a result of selective anodic dissolution in the potentiostatic mode, typical mutually continuous structures with pore and ligament sizes of 0.5–10 μm are formed. The appearance of pores can be traced up to 815°C, but their specific density on the surface is significantly decreased. An increase in the process temperature causes coarsening or recrystallization of the porous structure, an increase in the pore size, and a decrease in the selectivity of silver dissolution. Almost complete removal of silver from the alloy is achieved at the lowest temperature (306°C) as a result of anodic dissolution at a potential of 0.6 V relative to a silver chloride reference electrode (Ag/LiCl
0.57
CsCl
0.26
KCl
0.17
+ 3 mol % AgCl).
For the first time, the volatilities of UCl
4
and RbCl from their molten mixtures containing 2.0, 5.0, 12.3, 25.2, 32.6, and 48.8 mol % UCl
4
are measured in the temperature range from 890 to 1200 K ...using the transpiration technique. The chemical composition of the saturated vapors is determined. The commensurable amounts of binary compounds with the presumably RbUCl
5
composition are found to be present in the vapor phase along with UCl
4
and RbCl monomers and Rb
2
Cl
2
dimers. The variation of the temperature and concentration of the UCl
4
–RbCl molten mixtures with significant negative deviations from ideal behavior can change the volatility of uranium tetrachloride by several orders of magnitude. The laws of changing the volatility of uranium tetrachloride from its molten mixtures with various alkaline metal chlorides are discussed. The experimental data obtained by us earlier and in this work indicate that, in the medium of molten alkaline metal chlorides, the U
4+
ions enter the composition of complex anionic groups, the strength of which increases with a decrease in the uranium ion concentration in solutions and a decrease in the counterpolarizing effect of the alkaline cations on the anionic groups on going from LiCl to CsCl. This leads to a decrease in the volatility of UCl
4
in the same direction. An almost linear change in
as a function of the inverse radius (ionic moment) of the alkaline cations is observed.
The volatilities of the components of the saturated vapors of molten UCl
4
–NaCl–KCl mixtures containing 2.0, 5.0, 12.2, 25.1, 32.9, and 49.7 mol % UCl
4
are measured by a transpiration technique in ...the temperature range 880–1200 K. The chemical composition of the saturated vapors is determined. The vapor phase is most likely to contain the binary NaUCl
5
and KUCl
5
compounds, which make a significant contribution to the total vapor pressure over the molten mixtures. The molten mixtures are found to exhibit negative deviations from ideal behavior.
The absorption and emission spectra of NO, N
2
O, NO
2
, and N
2
O4 nitrogen oxides have been studied with high and intermediate spectral resolution in the range 0.25–25 μm under conditions of ...self-broadening and nitrogen-induced broadening at room and enhanced temperatures. The experimental data on the spectral transmittance function have been parameterized by the two-parameter equivalent mass method. The rovibrational band intensities have been measured and the data on the absorption induced by the pressure in collisions of NO
2
–NO
2
molecules have been obtained.
The distillation of chlorides from their molten mixtures is experimentally studied under various conditions. In all cases, the dilute solutions of BaCl
2
, SrCl
2
, and NdCl
3
(1–2 mol % each), as ...representatives of alkaline, alkaline earth, and rare earth metal chlorides, in the molten LiCl–KCl eutectic mixture are subjected to evaporation at a low pressure (down to ~1 Pa) and a temperature of 753–1033°C. The sublimate and salt melt compositions before and after distillation are analyzed, and conclusions are drawn about the degree of distillation, the selectivity of evaporation of the molten mixture components, and the relative volatilities of various chlorides.
We report on an observation of a fast 1.5 microm photoluminescence band from Er3+ ions embedded in an SiO2 matrix doped with Si nanocrystals, which appears and decays within the first microsecond ...after the laser excitation pulse. We argue that the fast excitation and quenching are facilitated by Auger processes related to transitions of confined electrons or holes between the space-quantized levels of Si nanocrystals dispersed in SiO2. We show that a great part--about 50%--of all Er dopants is involved in these fast processes and contributes to the submicrosecond emission.
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