Peculiarities of aluminium interaction with Ga85In15 eutectics as evidenced by X-ray synchrotron diagnostics

A set of X-ray synchrotron techniques, viz., diffraction, EXAFS/XANES spectroscopy and microtomography, is applied to elucidate microstructural changes in a technical aluminium alloy treated with GaIn eutectics. Such a treatment gives rise simultaneously to a prominent enbrittlement of the material and its activation towards reaction with water with the hydrogen evolution. The latter fact makes the activated aluminium a promising energy carrier for the small-scale hydrogen energetics. It is demonstrated that both phenomena are caused by the fast diffusion of the eutectics along intergrain boundaries and microcracks throughout the bulk of polycrystalline Al. The diffusion is promoted by the formation of (Al-Ga-In) solid solution in near-surface regions of Al crystalline grains. The progressive loss of activity of aluminium treated with GaIn eutectics upon a prolonged storage in humid air is due to the decomposition of the eutectics accompanied by the segregation of indium metal and partial gallium oxidation.     

XAFS studies of the local environment of Pb impurity atoms in barium,strontium, and calcium titanates

The local environment of Pb impurity atoms in BaTiO₃, SrTiO₃, and CaTiO₃ crystals was studied by XAFS technique. It is shown that, in both polar and nonpolar phases of BaTiO₃ and in SrTiO₃, the Pb atoms are displaced from the A lattice sites by ～0.15 Å; in CaTiO₃ this displacement is absent. Large values of Debye-Waller factors (0.05–0.10 Ų) for the atoms in the first shell of Pb observed in all the three crystals indicate the distortion of the oxygen environment of Pb atoms. The appearance of these features was explained by the fact that the Pb-O chemical bond has a noticeable covalent component and a Pb atom can form strong bonds only with four of the 12 surrounding oxygen atoms. The obtained data were used to determine the main factors responsible for the occurrence of ferroelectric phase transition in SrTiO₃ and CaTiO₃ and for the increase of the Curie temperature of BaTiO₃ when it is doped with Pb.     

Vector singularities of superposition of mutually incoherent orthogonally polarized beams

It is shown that, at an incoherent superposition of orthogonally polarized laser beams, a special type of singularities are formed in the cross section of a combined beam in place of the well-known singularities, such as optical vortices (for scalar fields); C points, at which the polarization is circular; and L lines, along which the polarization is linear (for coherent vector fields). These new singularities are U lines, along which the degree of polarization is zero and the state of polarization is undetermined, and P points, at which the degree of polarization is equal to unity and the state of polarization is determined by the nonzero component of the combined beam. Conditions of topological stability of U and P singularities are discussed, as well as peculiarities of the spatial distribution of the degree of polarization of the field in the vicinity of such singularities. First experimental results on the reconstruction of a vector skeleton formed by U and P singularities in combined speckle fields are presented.     

Interplay of spin conversion and structural phase transformations: re-entrant phase transitions in the 2-propanol solvate of tris(2-picolylamine)iron(II) dichloride

Crystal structures, magnetic and thermodynamic properties of the spin-crossover compound tris(2-picolylamine)iron(II) dichloride (with 2-propanol solvent molecules) have been measured in the temperature range from 15 to 293 K. X-ray diffraction, SQUID, and calorimetric experiments all showed two first-order phase transitions with hysteresis loops, a narrow one at T(1) approximately 196 K and a broad, triangular one covering the range 153相似文献   

Thermometry in a Gas Discharge Cell of an Optical Wavelength Calibrator

Temperature and pressure in a sealed Ar cell of an optical wavelength calibrator are measured using diode laser spectroscopy. The values of the thermodynamic parameters allowed determination of the fluctuations of the shift of the argon line at 811.5 nm. The expected fluctuation amplitude appears lower than ±15 MHz. The result obtained indicates the applicability of the studied calibrator as an optical reference and the correctness of previous measurements of pressure shift coefficients of the 811.5 nm argon line.     

Correction to: Finding False Paths in Sequential Circuits

Russian Physics Journal - A reference on the grant “The study was partially supported by Russian Science Foundation research project №14-19-00218” has been missed.     

Regioselective single-reactor synthesis of arylsulfonyl derivatives of 3,5-diamino-1,2,4-triazole

Arylsulfonylation of 1-acetyl-3,5-diamino-1,2,4-triazole with arylsulfonyl chlorides in pyridine, with the subsequent hydrolysis of the acetyl group, was studied; a new regioselective method for synthesis of N-(5-amino-1H-1,2,4-triazol-3-yl)arylsulfonamides was developed.     

The propagation of shock waves in viscous media

The question of the thickness of shock waves in a viscous gas was treated in papers [1, 2]. The present paper derives general equations for solving problems concerning the flow of a medium inside a shock wave layer, and the change of this layer in viscous media. By way of an example we consider a problem of this type for a Kelvin medium.