Electrical and thermoelectric properties of ZnO under atmospheric and hydrostatic pressure

Temperature (for T = 77–400 K) and pressure (for P ≤ 8 GPa) dependences of conductivity σ(T,P). Hall coefficient R _H(T, P), and Seebeck coefficient Q(T) were studied in single-crystal n-ZnO samples with the impurity concentration N _i = 10¹⁷ ? 10¹⁸ cm^?3 and free-electron concentration n = 10¹³?10¹⁷ cm^?3. Single crystals were grown by the hydrothermal method. Dependence of the ionization energy of a shallow donor level on the impurity concentration E _d1(N _d) is determined, along with the pressure coefficients for the ionization energy ?E _d1/?P and static dielectric constant ?x/?P. A deep defect level with the energy E _d2 = 0.3 eV below the bottom of the conduction band is found. The electron effective mass is calculated from the obtained data on the kinetic coefficients R _H(T) and Q(T).     

Physicochemical properties of solutions and ultrathin films of triple-decker gadolinium tetra-15-crown-5-phthalocyaninate

The ability of the triple-decker gadolinium complex with tetra-15-crown-5-phthalocyanine Gd₂(R₄Pc)₃, (R = 15-crown-5) (1) to form monolayers and Langmuir-Blodgett films (LBFs) was studied for the first time. The charge characteristics of molecules of a triple-decker phthalocyaninate in monolayer, as well as their orientation and adhesion to the water subphase, were controlled by changing the surface pressure, pH, and subphase composition (aqueous solutions containing triethylenetetramine (TETA) and metal cations). It was shown that the presence of Na⁺ and protonated TETA aminogroups in resulted in an increasing limiting monolayer area and significant decreasing of the monolayer liquid state region. It is proven that the observed effects are caused by the conformational and charge transitions of peripheral crown ethers induced by their interaction with cations. A comparison of the differential reflectance spectra of the complex monolayer on the deionized water surface with UV-Vis absorption spectra of three-layer Gd₂(R₄Pc)₃ LBF and complex solution in chloroform shows that partial complex oxidation and intensive stacking formation occurs already at the stage of monolayer formation on the subphase surface. Electrochemical studies of three-layer LBFs performed at the indium-tin-oxide electrodes (ITO-electrodes) using cyclic voltammetry (CV) showed three reversible redox waves in the potential range −200 to +1100 mV (vs. Ag⁺/AgCl). All registered peaks remain the same position and intensity upon multiple cycling. plasmon resonance (SPR) measurements allow to register three stable redox states of studied LBF upon applying the external potential. Such behavior shows the possibility to use multistep redox transformations of studied complex LBF for developing of stable and reproducible switchable optoelectronic systems.     

Phase transformation of <Emphasis Type="Italic">p</Emphasis>-Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>GeAs<Subscript>2</Subscript> single crystals at 5.5 GPa

The electrical resistivity and Hall coefficient of oriented single-crystal p-Cd_{1 − x} Mn _x GeAs₂ samples have been measured at high pressures. The results indicate that the crystals undergo a reversible structural transformation at 5.5 GPa, which is independent on the sample orientation.     

Measurement of the Levels of Multicomponent Media by a High-Frequency Method

A high-frequency method of measuring the levels of multicomponent media is described which enables up to five interfaces to be measured simultaneously. A mathematical model of the propagation of the signal in the pickup and ways of simplifying it for use in engineering problems is proposed. An example of a practical form of the method for measuring the position of the boundaries in a three-component system is given.     

Resistivity and Hall Coefficient of Zinc Diarsenide at Hydrostatic Pressures of up to 9 GPa

The electrical properties of ZnAs₂ single crystals were measured along the [001] direction in the pressure range from 0 to 9 GPa. The electrical resistivity of the crystals was found to decrease by one order of magnitude as the pressure increases from 0 to 7 GPa, without significant changes at higher pressures. The Hall coefficient drops by two orders of magnitude as the pressure increases from 0 to 7 GPa and remains constant in the range from 7 to 9 GPa.     

Stripping of hydrogen sulfide from visbreaking resid

Technical and production solutions ensuring a commercial boiler fuel with a hydrogen sulfide content of no more than 2 ppm are developed as a result of the basic design of a unit for stripping hydrogen sulfide from visbreaking resid. The potential exists for a further increase in the output of the visbreaking plant to 2 million tons/year, where the actual output achieved is 1.4 million tons/year.     

Reconstruction of the Interface Region of Epoxy Polymer-Aluminium Coating Systems in an Aqueous Medium

This paper reports a study of the process of reorganization of the epoxy polymer-aluminium interface during the storage of the coating systems in water. The storage in water first leads to the separation of the system components and then to the restoration of its integrity. As a result, the initial level of adhesion strength is reached or even exceeded. Of all the variable parameters (the solution composition and pH, the sign of the potential applied to the substrate surface, the method of its treatment, the type of hardener used and the conditions of deposition of oligomer from solution and the curing of the system, etc.), temperature was found to have the most significant effect on the rate of the restoration of the adhesion bonds in an aqueous medium. A mechanism of the process was proposed based on the sorption and calorimetric studies of the adhesion systems in an aqueous medium. This mechanism allows for the effect of the electrostatic interactions on the coalescence of the polymer and substrate surfaces with a thin water interlayer between them.