Technical Physics Letters最新文献

Abstract—The behavior of a “water-in-oil” emulsion stabilized with asphaltenes under the action of an inhomogeneous alternating electric field has been studied. The experimental technique was based on the use of microfluidics, optical microscopy, and high-speed video filming. The dependences of quantitative estimates of the parameters characterizing the dynamics of the emulsion destruction on the frequency and amplitude of the applied field have been obtained. The technique will be useful in developing efficient methods for breaking emulsions and modifying the existing technologies for separating oil emulsions into phases.

A new approach to the creation of millimeter-wave radio imaging systems is proposed. This approach is based on the use of an array receiver consisting of a densely packed (pixel size of 4 mm) array of planar mixers located in the focal plane of a quasi-optical objective, with application of the frequency-modulated continuous-wave radar technique. It has been demonstrated that the implementation of the heterodyne type of reception makes it possible to increase the distance range of the array radio imaging system up to ~100 m while maintaining the angular resolution at the previous level.

The dynamics of the interfacial tension coefficient at the interface between water and model solutions of asphaltenes of different concentrations in toluene has been studied. It has been shown that, over time, the interfacial tension decreases due to the adsorption of asphaltene molecules at the interface. With an increase in the concentration of asphaltenes in the solution, the decrease in interfacial tension occurs more intensively. The results of a study of the elongation of a water drop in a solution under the influence of an electric field are presented. It is shown that after the formation of an adsorption film, a higher electric field must be applied to stretch the droplet, and the relative elongation depends nonlinearly on the applied voltage.

It was found that in the region of the percolation threshold, depending on the dominance of one or another conduction mechanism, the temperature dependence of the specific volume resistivity ρ(T) of the polymer composite based on a matrix of ethylene vinyl acetate is significantly transformed. With an increase in the CB content, there is a decrease by several orders of magnitude in the maximum value of the relative resistivity ρ(T)_max/ρ₂₀ in its temperature dependence. Peroxide crosslinking of matrix macromolecules leads to a change in the nature of the temperature dependence of resistivity.

Abstract—To form a multibeam radiation pattern, it is proposed to use the axial geometry of acousto-optic interaction in paratellurite. In the single frequency mode, the use of this geometry for angular scanning is characterized by a dip in the frequency response. Optimization of a multifrequency radio signal makes it possible to efficiently divide laser radiation into several beams with maintaining the fundamental advantages of axial geometry: minimum crystal size and power consumption.

The main results of non-linear optical, spectral and current–voltage characteristics research of pyridine organic conjugated molecule-carbon nanoparticles combined system have been presented. The perspective of these materials further study in global trends of modern search of materials for optical limiting has been demonstrated also in the present paper.

A plasma-chemical method for the modification of silicon carbide particles is presented, which makes it possible to obtain particles with a controlled surface morphology. The variable parameter of particle processing was the ratio of the fraction of plasma-forming (Ar) and additional (H) gases. It was shown that at Ar/H = 100/0, the formation of a carbon shell is observed; at Ar/H ratios of 91/9 and 84/16, the particles are characterized by a carbon shell decorated with silicon nanoparticles or nanowires, respectively. The modified particles were analyzed using scanning electron microscopy and Raman spectroscopy.

Abstract—The growth mechanism of monolayer on the top facet of Ga-catalyzed GaAs and GaP nanowires is investigated. Within the framework of a theoretical model, the maximal monolayer coverage due to the material in the catalyst droplet, the nanowire growth rate and the content of group V atoms in the droplet are found depending on the growth conditions. The estimates of the phosphorus re-evaporation coefficient from neighboring nanowires and substrate are obtained by comparing the theoretical and experimental growth rate of Ga-catalyzed GaP nanowires.

The functionalization of multi-walled carbon nanotubes in He:O plasma is investigated. It is shown that plasma treatment leads to the removal of defective outer graphene layers and their fragments due to oxidation. It is established that the surface of functionalized multi-walled carbon nanotubes contains numerous uncoordinated carbon atoms and oxygen-containing functional groups. The preservation of the structure of the internal graphene layers of nanotubes and the formation of broken chemical bonds ensure a decrease in electrical resistance. At the same time, there is a narrowing of the distribution of electrical resistance values of nanotube ensembles.

The properties of c-oriented thin films of Sr_0.5Ba_0.5Nb₂O₆ grown on a Si(001) (p-type) substrate with a pre-deposited Ba_0.2Sr_0.8TiO₃ layer were studied using scanning probe microscopy and dielectric spectroscopy. It is established that the Sr_0.5Ba_0.5Nb₂O₆ films are characterized by low surface roughness (less than 6 nm) and average crystallite size of ~93 nm. It is shown that there is spontaneous polarization in the film directed from its surface to the substrate, which causes the manifestation of the field effect for the case of the Si substrate with p-type conductivity without the external field effect. Differences in the magnitudes of the surface potential signal for regions polarized by an external electric field of different polarities (+10 and –10 V), as well as in their relaxation to the initial state, are revealed. The reasons for the established patterns are discussed.