Spaser operation in the presence of external optical field

The operation of surface plasmon amplifier by stimulated emission of radiation (spaser) in the presence of external optical field is analyzed. The range of external field amplitude E and mismatch Δ of the external field frequency and the spaser generation frequency (Arnold tongue) E > E _synchr(Δ) in which the spaser works at the external field frequency is determined. The analytical and numerical calculations at the given mismatch Δ yield three ranges: E < E _synchr(Δ) (the spaser exhibits stochastic regime and point (Δ, E) is outside the Arnold tongue), E _synchr(Δ) < E < E _L (Δ) (transient range where the spaser polarization weakly depends on the field amplitude and is mainly determined by the pump level), and E > E _L (the spaser generation is suppressed and the spaser polarization is equal to the polarization of nanoparticle in the presence of external field).     

Current flow through metal shunts in ohmic contacts to n +-Si

It is experimentally found that an ohmic contact based on Au-Pt-Ti-Pd-n ⁺-Si metallization is formed due to nanoscale metal shunts containing Si, Au, and Pt in the region of the interface with n ⁺-Si, which appears during heat treatment at T = 450°C for 10 min in a vacuum chamber with a residual pressure of 10^?6 Torr. The high density of shunts adjoining dislocations and other imperfections is confirmed by the temperature dependence of the specific contact resistance ρ _c (T). The density of conductive dislocations, calculated from the temperature dependence of ρ _c is ～5 × 10⁹ cm^?2 which correlates with the density of structural defects, determined by the etch pits after removal of the metallization layers.     

About the Nature of Quasi-Cleavage in Low-Carbon Steel Embrittled with Hydrogen

Metal Science and Heat Treatment - Scanning electron microscopy and confocal laser scanning microscopy are used to study a fracture surface of hydrogen-charged low-carbon steel, which has been...     

Phosphate-hydroxyquinoline method for separation and volumetric determination of zirconium

The proposed method consists of a combination of the well-known phosphate method for separation of zirconium, and determination of zirconium as the hydroxyquinolate. The separation of zirconium hydroxyquinolate from an oxalate medium after solution of the phosphate preccipitate in oxalic acid has been used for the first time. The conditions of separation of zirconium from titanium and thorium in the phosphate precipitation, and from niobium and tantalum in precipitation of the hydroxyquinolate, have been studied. By this method it is possible to separate zirconium in practice from all accompanying elements (except hafnium), and to determine small amounts of zirconium (2–5 mg) by a volumetric method to an accuracy of ± 2–4%.     

Sintering of nanostructured powders

Results are provided for a study of the internal structure of submicron spherical particles in ZrO₂–Y₂O₃ aerosol powders synthesized by ultrasonic atomization pyrolysis. It is shown the sintering potential for these powders is determined mainly by their internal nanostructural parameters, and not the degree of starting powder fineness. It is detected that the activity of submicron nanostructured powders is commensurate with the activity of ultrafine powders. In contrast to the latter, these powders consist of individual particles not joined in stable multiparticle formations, i.e., agglomerates. This simplifies considerably their practical application without loss of quality for the material obtained.     

Effect of Acidic Peptization on Formation of Highly Photoactive TiO2 Films Prepared without Heat Treatment

Nowadays, it is a great challenge to synthesize crystalline TiO₂ nanostructures using low‐temperature methods without annealing stage. Such an approach allows to perform functional and structural modification in the formed crystalline phase by thermally unstable compounds, such as biomaterials, MOFs, dye sets in situ, which was previously considered impossible. In this work, we have developed and analyzed the effect of acidic peptization on formation of highly photoactive titania crystallites in an aqueous solution using titanium tetraisopropylate as a precursor. Acids with different dissociation degrees in water were used as peptizing mediators to determine the effect of protonation on sol formation. The dip‐coating films were obtained with consequent drying of the sols via evaporation of the solvent. The as‐prepared catalysts were characterized by X‐ray diffraction, AFM microscopy, UV–V is spectroscopy, Brunauer–Emmett–Teller surface area. The aggregate size of TiO₂ in the colloidal suspension solution was measured by dynamic light scattering. Photocatalytic activity of films was studied by decomposition of Rhodamine B dye. It is found that the size of colloids in an aqueous solution is proportional to the protonation degree of the surface of particles and does not depend on the [Ti⁴⁺]/[H⁺] ratio, and peptization under weakly acidic conditions leads to anisotropic rod‐like nanoparticles. The highest photocatalytic activity was exhibited by the TiO₂–HCl‐based coatings, ~3.5 times higher than that of the Acet.‐prepared sample.     

Effect of Shell Material on the Detonation of an Explosive Charge

The effect of shell material (copper and silicon carbide) on the detonation of a cylindrical explosive charge was analyzed. The wave patterns in the detonation products and the shells are substantially different, which is due to different sound velocities and the rapid destruction of the ceramic under explosive loading. The wave pattern at the explosive/ceramic interface was found to be affected by desensitization of the explosive due to its loading by an advancing wave from the shell side, resulting in a decrease in pressure, blurring of the detonation front, and an increase in particle velocity. Throughout the process, there is a continuous increase in the time of explosive decomposition near the interface between the explosive and the ceramic shell. An extended region with a constant pressure close to the Chapman–Jouguet pressure was observed on the axis of symmetry behind the detonation front of the explosive charge in the ceramic shell.     

The microstructure of composite cermet coatings produced by carbo-vibroarc surfacing

The results of investigation of the microstructure of composite coatings produced by carbo-vibroarc surfacing using cermet pastes are presented. It is shown that the composite cermet coating consists of two zones – the main and transition. The main zone of the coating contains the Fe₂B hardening phase with nickel and chromium atoms implanted in the crystal lattice of the phase. The zone is situated in the matrix of the solid solution of iron and nickel Ni₃Fe. The transition zone of the coating is formed by the mutual diffusion of the coating and the substrate and consists of the (Fe, Ni)₂B hardening phase and the Ni₃Fe matrix. It is also shown that the hardening phases form plate-shaped grains with thicknesses of 1–4 μm and more than 100 μm long, distributed in the form of colonies throughout the entire volume of the coating zone. In the direction to the transition zone, the shape of the structural components changes to circular with the diameter of up to 5 μm.     

Study of Deformation Phenomena in TRIP/TWIP Steels by Acoustic Emission and Scanning Electron Microscopy

Modern metastable steels with TRIP/TWIP effects have a unique set of physical-mechanical properties. They combine both high-strength and high-plasticity characteristics, which is governed by processes activated during deformation, namely, twinning, the formation of stacking faults, and martensitic transformations. To study the behavior of these phenomena in CrMnNi TRIP/TWIP steels and stainless CrNiMo steel, which does not have these effects in the temperature range under study, we used the method of acoustic emission and modern methods of signal processing, including the cluster analysis of spectral-density functions. The results of this study have been compared with a detailed microstructural analysis performed with a scanning electron microscope using electron backscatter diffraction (EBSD).