Synthesis and X-ray Diffraction Characterization of FeNdSbS4, an Analog of Berthierite

A rare-earth-containing analog of the mineral berthierite, with the composition FeNdSbS₄, was synthesized for the first time. FeNdSbS₄ is isostructural with FeSb₂S₄ and crystallizes in orthorhombic symmetry (sp. gr. Pbam, Z = 4) with lattice parameters a= 11.395 Å, b = 14.136 Å, and c = 3.747 Å.     

Paramagnetic Meissner Effect in Electrochemically Doped Indium-Tin Oxide Films

Transparent conductive indium-tin oxide (ITO) thin films, electrochemically intercalated with alkali (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺), alkali earth (Mg⁺², Ca⁺²), or complex NH\(_{4}^{+}\) ions, show tunable superconducting transitions with dome-shaped behavior of T _c versus electron density around the maximum at ～ 5 K. On field cooling, the transition into the superconducting state is accompanied by a paramagnetic response, i.e., an increase of magnetization, rather than the usual diamagnetic Meissner response. We provide an extensive study of this so-called paramagnetic Meissner effect (PME), using DC SQUID, transport measurements and a variety of sample sizes and growth conditions. We show that the PME in electrochemically doped ITO films results from a higher T _c at the sample edges than at the center of disk-shaped samples, causing flux to be expelled towards the center of the disk, following the flux-compression theory of Koshelev and Larkin. Changing to the opposite spatial T _c profile largely removes the paramagnetic response. The paramagnetic magnetization is strongly influenced by sample geometry and flux pinning conditions. The reduction of pinning defects by thermal annealing removes the paramagnetic response. An alternation of the external magnetic field restores the usual Meissner diamagnetism.     

Development of Technologies for Reducing the Error of Traditional Algorithms of Correlation Analysis of Noisy Signals

Measurement Techniques - The factors that have an effect on estimation errors of the correlation functions of noisy signals in using traditional algorithms to evaluate them are analyzed. It is...     

Thermophysical properties of polymer composite based on multiwalled carbon nanotubes,obtained by electrospinning

The heat capacity and thermal diffusivity of a polymer composite based on multiwalled carbon nanotubes (95%), produced by electrospinning in the temperature range of 300 ≤ Т < 450 K, are investigated during heating and cooling. Temperature hystereses are detected characteristic of first-order phase transitions.     

An apparatus for thermodiffusion synthesis of multicomponent semiconductor compounds

An apparatus for thermodiffusion synthesis of multicomponent semiconductor compounds is described. CuInSe₂ polycrystalline films were obtained in the selenization temperature range 300°C ≤ Т_sel ≤ 400°C. The chemical analysis showed that the composition of the films that were synthesized at a selenization temperature of Т_sel = 400°C is stoichiometric. A series of diffraction lines that is characteristic of the chalcopyrite structure is present in the line X-ray diffraction patterns of these films.     

Oxidative dehydrogenation of cyclohexane over modified zeolite catalysts

The catalytic activity of modified zeolites in selective oxidative dehydrogenation of cyclohexane has been studied. It has been established that polymetallic zeolite catalyst, namely, CuZnCoCr-clinoptilolite (0.5% Cu²⁺, 0.2% Zn²⁺; 0.1% Co²⁺; 0.1% Cr³⁺) manifests the highest activity in the reaction under consideration. The kinetic scheme of the reaction mechanism has been proposed, and a kinetic model of the process has been developed on the basis of stepwise mechanism schemes. The numerical values of the kinetic parameters are calculated.