Dynamics of the Kinetic Energy in the Atmospheric Boundary Layer from the Results of Minisodar Measurements

Russian Physics Journal - Based on acoustic remote measurements of vertical profiles of three wind velocity components in a 200-meter boundary layer of the atmosphere, values of the kinetic energy...     

Hydrothermal synthesis and microstructure of α-Zn<Subscript>2</Subscript>SiO<Subscript>4</Subscript>:V crystal phosphor

A morphologically uniform single-phase crystal phosphor α-Zn₂SiO₄:V was prepared by one-pot hydrothermal synthesis. Energy dispersive analysis showed that a zinc silicate-base solid solution was formed with a vanadium content of 10 ± 1 at %. Its luminescence spectrum was a broad luminescence band in the region 400–700 nm with a peak near 540 nm.     

The effect of the synthesis method on the morphological and luminescence characteristics of α-Zn<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript>

A promising yellow phosphor, α-Zn₂V₂O₇, was synthesized at temperatures below the phase transition temperature (610 ± 5°C) by three different methods: solid-phase and microwave processes and thermolysis of a water–salt composition. According to powder X-ray diffraction, the structures of all samples belonged to space group C/2c. Depending on the method of synthesis, the particle size varied from 500 nm (thermolysis of a water–salt composition) to 5–8 μm (ceramic and microwave methods). The excitation spectra of all samples are in the UV region (220–400 nm) and the emission spectra are in the 400–750 nm wavelength range. The photoluminescence spectra of the samples are non-elementary, which is caused by specific features of the electronic charge transfer in the structural VO₄ tetrahedra.     

Effect of thermal transformations of constituent polyhedra of the crystal structure on the properties of Cd2V2O7

Analysis of variations in the linear and angular parameters of constituent polyhedra of the cadmium pyrovanadate Cd₂V₂O₇ structure, namely, VO₄ tetrahedra and CdO₆ octahedra, as calculated from the results of in situ high-temperature X-ray diffraction experiments in the range from 25 to 900°C, showed that, in the range from 600 to 720°C, the thermal expansion coefficient (tec) of CdO₆ polyhedra is near zero, whereas VO₄ tetrahedra increase in volume, although less strongly than in other temperature ranges. A structural interpretation is given to anomalous temperature dependences of cadmium ion emission and electrical conductivity on the basis of different thermal behavior patterns of the constituent polyhedra of the Cd₂V₂O₇ structure.     

Diagrams of phase equilibria: a basis for implementing technologies of technogenic waste product conversion

Diagrams of the phase equilibria of multicomponent systems simulating the composition of technogenic waste products of thermal power stations’ burning of vanadium-containing fuel were obtained. The possibility of controlling the degree of vanadium extraction during oxidative calcinations was shown by varying the proportions of the mixture of two types of waste: thermal power station energy silts and wastewater treatment silts.     

Thermally activated transformations in stable and metastable copper(II) pyrovanadate polymorphs

The structural transformations of α- and β′-Cu₂V₂O₇ phases over the entire temperature range of their existence and α → β′-Cu₂V₂O₇ and β′ → β-Cu₂V₂O₇ polymorphic transitions in α-Cu₂V₂O₇ are described from the crystal-chemical standpoint. Variations in the parameters of the polyhedral blocks of the α-Cu₂V₂O₇ structure implies that the greatest deformations occur with a negative and near-zero bulk thermal expansion in the range from room temperature to 400°C. The compression and rotation of vanadium-oxygen diortho groups is accompanied by unbending of zigzag copper-oxygen chains, with the distances between them unchanged, which is the reason for the anomalous volume expansion of the structure. Thermal distortion of β′-Cu₂V₂O₇ is insignificant. The thermal expansion coefficients (TECs) of unit cell parameters are as follows: α _a = ?1.36 × 10^?5 1/K, α _b = 1.95 × 10^?5 1/K, α _c = 1.37 × 10^?5 1/K, α_β = ?0.18 × 10^?5 1/K, and α _V = 1.93 × 10^?5 1/K. We demonstrate that the low-temperature Cu₂V₂O₇ phase can be formed without admixtures of metastable β-Cu₂V₂O₇ upon slow cooling (at about 1 K/min) of the high-temperature phase.     

Phase relations in the Zn<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript>-Cu<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> system from room temperature to melting

Phase relations in the Zn₂V₂O₇-Cu₂V₂O₇ system were studied by high-temperature X-ray diffraction and differential thermal analysis. The major phase constituents of the system are solid solutions based on Zn₂V₂O₇ and Cu₂V₂O₇ polymorphs and their coexistence regions. The generation of α-Zn_{2 − 2x} Cu_2x V₂O₇ solid solution, where 0 ≤ x ≤ 0.30, leaves almost unchanged the stabilization temperature of the high-temperature zinc pyrovanadate phase. The α-Cu_{2 − 2x} Zn_2x V₂O₇ homogeneity range is 5 mol % Zn₂V₂O₇. In the range 0.050 ≤ x ≤ 0.09 from 20 to ∼ 620°C, there is the two-phase field of α-Cu₂V₂O₇ and β-Cu₂V₂O₇ base solid solutions. At still higher temperatures, β-Zn_{2 − 2x} Cu_2x V₂O₇ and α-Cu_{2 − 2x} Zn_2x V₂O₇ coexist in the mixed-phase region. β-Zn_{2 − 2x} Cu_2x V₂O₇ solid solution, where 0 ≤ x ≤ 0.30, exists above 610 ± 5°C. The extent of the β′-Cu₂V₂O₇-base solid solution is 9 to 65 mol % Zn₂V₂O₇ at 615 ± 5°C, expanding to 0 mol % Zn₂V₂O₇ with rising temperature. Original Russian Text ￠ T.I. Krasnenko, M.V. Rotermel’, S.A. Petrova, R.G. Zakharov, O.V. Sivtsova, A.N. Chvanova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1755–1762.     

Sound generation in the atmosphere upon exposure to high-power milli- and microsecond laser pulses

A review of works on generation of acoustic pulses in the atmosphere upon exposure to high-power laser pulses is presented in this paper. Characteristics of sound pulses in the atmosphere accompanying the propagation of high-power milli- and microsecond laser pulses, including the peak sound pressure level and the shape and spectrum of acoustic pulses, are discussed. The special features of acoustic pulses from individual liquid and solid aerosol particles and ensembles of monodisperse particles and polydisperse atmospheric aerosol are discussed. The characteristics of acoustic signals from long laser sparks and collective optical discharges are considered.     

<Superscript>51</Superscript>V NMR in Mn<Subscript>2−2<Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript>2<Emphasis Type="Italic">x</Emphasis></Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> solid solutions

⁵¹V NMR, DTA, and thermogravimetric analysis are used to study the thermal behavior of a manganesenickel pyrovanadate complex Mn_2?2x Ni_2x V₂O₇. It is shown that the nature of ⁵¹V hyperfine interactions in manganese pyrovanadate and solid solutions based on its polymorphic modifications is specified by the structurally activated oxygen exchange with the gaseous phase.