Simulation of the Heat Transfer Process of Superconducting Films in the Resistive State

Technical Physics - The heat transfer in a contact–film–substrate system was analyzed under conditions in which the heat removal from a sample to the substrate is insufficient to avoid...     

Special features of preparation of nanosized zirconium diboride powders of various dispersity

Products of the zirconium powder reaction with amorphous boron in a Na₂B₄O₇ ionic melt at 650–850°C and those of the ZrCl₄ reaction with NaBH₄ at 300–725°C have been studied by means of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry, and elemental analysis. At temperature ≥750°C, single-phase ZrB₂ with the particle size of 60–80 nm is formed in a Na₂B₄O₇ ionic melt, whereas the ZrB₂ powder obtained via the reaction of ZrCl₄ with NaBH₄ at temperature ≥575°C consists of particles differing in the shape, some of which are close to spherical with diameter of 10–35 nm.     

Nanosized Vanadium Diboride: Synthesis,Structure, and Properties

Russian Journal of General Chemistry - X-ray diffraction, scanning electron microscopic, and X-ray photoelectron spectroscopic examinations, as well as energy dispersive X-ray and elemental...     

Upper critical field of niobium nitride thin films

The temperature dependences of the superconducting transition of niobium nitride (NbN) thin films have been investigated via the first harmonic of the voltage in dc magnetic fields of up to 8 T. The temperature dependence of the second critical field of NbN has been determined. The parameter responsible for the effect of spin paramagnetism in this material and the temperature dependence of the upper critical field that describes well the experimental data have been found in terms of the Werthamer–Helfand–Hohenberg (WHH) theory. The key parameters of the superconductor have been estimated from the transport and optical measurements.     

Synthesis of nano-sized titanium diboride in a melt of anhydrous sodium tetraborate

X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, and elemental analysis were used to study the interaction of titanium powder with finely powdered boron of particle size 10?C20 ??m in Na₂B₄O₇ ionic melt, in the temperature range 973?C1088 K, at the 5?C10 h contact duration. The TiB₂ formation was shown to occur at the temperatures 1018 K or above, that is, at the borax melting temperature. According to the scanning electron microscopy, theTiB₂ powder consists of the 70?C75 nm particles, and its coherent scattering region calculated from the XRD data amounts to 55 nm.     

Electron work function of intermetallic compounds in the cerium-cobalt system

The concentration dependences of the electron work function for lithium samples in the cobaltrich region of the state diagram of the Ce-Co binary mixture is studied by the contact potential difference method at 20°C. It is shown that the electron work function isotherm has the shape of a broken line with kinks corresponding to intermetallic compounds formed in the cerium-cobalt binary system.     

Electron work function of LaNi5 ? x T x (T = Al, Cu, Fe; x = 0, 1) intermetallics

The method of contact potential difference is applied to determine the electron work function of ingots and pellets (compacted powder) of LaNi_{5 ? x} T _x (T = Al, Cu, Fe; x = 0, 1) intermetallics at 293 K. A correlation is revealed between the electron work function and the heats of formation of the intermetallics and their hydrides.     

Electron work function in YNi3 − x T x (T = Cu,Fe, Mn; x = 0, 0.5) intermetallics

The electron work function in cast samples and cylindrical compacts of YNi_{3 ? x} T _x (T = Cu, Fe, Mn; x = 0, 0.5) intermetallics is determined using the contact potential difference method. A correlation is found between the electron work function and the electronegativity of elements substituting Ni in the YNi₃ structure.     

Partial Regularity of Weak Solutions of the Stationary 3D-Boussinesq System

In this paper, we study the smoothness of weak solutions of the three-dimensional stationary Boussinesq system describing steady-state motion of viscous heat-convergent Newtonian fluid whose viscosity may depend on the temperature of the fluid. The principal feature of the system under consideration is the occurrence of the dissipative term in the equation of energy balance. This term is equal to the product of the stress and the strain velocity tensors and has a quadratic growth with respect to the gradient of the velocity field. We prove the partial regularity of solutions to this system and give an estimate of the Hausdorff measure of the singular set. Bibliography: 14 titles.     

On Coercive Estimates for Solutions of Linear Systems of Hydrodynamic Type

Local and nonlocal coercive estimates in Lebesgue, Hölder, and Morrey–Campanato spaces are proved for solutions of linear stationary systems of hydrodynamic type. For this purpose, the technique proposed by Italian mathematicians for the study of solutions to equations and systems of elliptic and parabolic types is developed. Bibliography: 14 titles.