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GaAsBi nanowires represent a novel and promising material platform for future nano-photonics. However, the growth of high-quality GaAsBi nanowires and GaAsBi alloy is still a challenge due to a large miscibility gap between GaAs and GaBi. In this work we investigate effects of Bi incorporation on lattice dynamics and carrier recombination processes in GaAs/GaAsBi core/shell nanowires grown by molecular-beam epitaxy. By employing photoluminescence (PL), PL excitation, and Raman scattering spectroscopies complemented by scanning electron microscopy, we show that increasing Bi-beam equivalent pressure (BEP) during the growth does not necessarily result in a higher alloy composition but largely affects the carrier localization in GaAsBi. Specifically, it is found that under high BEP, bismuth tends either to be expelled from a nanowire shell towards its surface or to form larger clusters within the GaAsBi shell. Due to these two processes the bandgap of the Bi-containing shell remains practically independent of the Bi BEP, while the emission spectra of the NWs experience a significant red shift under increased Bi supply as a result of the localization effect. [ABSTRACT FROM AUTHOR]

GaAsBi nanowires represent a novel and promising material platform for future nano-photonics. However, the growth of high-quality GaAsBi nanowires and GaAsBi alloy is still a challenge due to a large miscibility gap between GaAs and GaBi. In this work we investigate effects of Bi incorporation on lattice dynamics and carrier recombination processes in GaAs/GaAsBi core/shell nanowires grown by molecular-beam epitaxy. By employing photoluminescence (PL), PL excitation, and Raman scattering spectroscopies complemented by scanning electron microscopy, we show that increasing Bi-beam equivalent pressure (BEP) during the growth does not necessarily result in a higher alloy composition but largely affects the carrier localization in GaAsBi. Specifically, it is found that under high BEP, bismuth tends either to be expelled from a nanowire shell towards its surface or to form larger clusters within the GaAsBi shell. Due to these two processes the bandgap of the Bi-containing shell remains practically independent of the Bi BEP, while the emission spectra of the NWs experience a significant red shift under increased Bi supply as a result of the localization effect. [ABSTRACT FROM AUTHOR]

A two-dimensional complex plasma containing active Janus particles was experimentally studied. A single layer of micrometer-sized plastic microspheres was suspended in the plasma sheath of a radio frequency discharge in argon at low pressure. The particle sample used was a mixture of regular particles and Janus particles, which were coated on one side with a thin layer of platinum. Unlike a suspension consisting of regular particles only, the suspension with the inclusion of Janus particles did not form an ordered lattice in the experimental conditions used. Instead, the particles moved around with high kinetic energy in a disordered suspension. Unexpectedly, the mean kinetic energy of the particles declined as the illumination laser power was increased. This is explained by the competition of two driving forces: the photophoretic force and the oppositely directed ion drag force. The mean-squared displacement of the particles scaled as t α with α = 2 at small times t indicating ballistic motion and α = 0.56 ± 0.27 at longer times due to the combined effect of the Janus particle propensity to move in circular trajectories and external confinement. [ABSTRACT FROM AUTHOR]

Amplification of a dosimetric EPR signal in mineralized biological materials available in limited quantities has been demonstrated in this paper. Powders of irradiated enamel, dentin, and bone tissue were placed into silica ampoules with the outer diameter close to 1.4 mm. To amplify the signal, the dielectric insert in the form of cylinder with the outer radius 2.85 mm, the inner radius 0.75 mm, and the height 1.85 mm made of a high-κ and low-loss ceramic material BaTi4O9 + 8.5% ZnO has been used. It has been shown that maximum signal amplification (about an order of magnitude) has been achieved when the sample is completely inserted into this dielectric. It has been found that the line shape of the dosimetric signal is not distorted, if using the dielectric insert. Decomposition of the amplified EPR spectra allowed us to determine the relative contribution of two types of CO2- radicals to the dosimetric signal, which coincides with the literature data. [ABSTRACT FROM AUTHOR]

Heat transport in a three-dimensional complex (dusty) plasma was experimentally studied in microgravity conditions using a Plasmakristall-4 (PK-4) instrument on board the International Space Station (ISS). An extended suspension of microparticles was locally heated by a shear flow created by applying the radiation pressure force of the manipulation-laser beam. Individual particle trajectories in the flow were analyzed, and from these, using a fluid heat transport equation that takes viscous heating and neutral gas drag into account, the complex plasma's thermal diffusivity and kinematic viscosity were calculated. Their values are compared with previous results reported in ground-based experiments with complex plasmas. [ABSTRACT FROM AUTHOR]

Complex plasma crystals are popular model systems where various plasma-specific or generic phenomena can be studied at the level of individual particles. Addressing the growing need for larger two-dimensional (2D) plasma crystals, a new plasma setup was built at the DLR Institute of Materials Physics in Space. The setup allows obtaining larger than before, highly ordered 2D plasma crystals and exploring new parameter ranges. It is based on a relatively large (90 cm in diameter) vacuum chamber where a capacitively coupled radio-frequency discharge is used to levitate polymer microparticles. The discharge is created between the lower rf electrode and the grounded chamber walls, the particles levitate in the plasma (pre)sheath above the electrode and are observed by video microscopy through the large top glass window and through the side windows. The first observations of plasma crystals in the new setup are reported. [ABSTRACT FROM AUTHOR]

Mode-coupling instability (MCI) in a single-layer complex plasma crystal was studied experimentally in the regime of strong neutral gas damping. To trigger MCI, the discharge power was reduced at constant gas pressure. Surprisingly, at the onset of MCI the mean interparticle spacing became larger and the normalized neutral gas damping rate marginally increased. A steady-state regime where MCI occurred but was suppressed by the neutral gas friction was observed. Suppressed MCI caused heating up of the plasma crystal but did not lead to its melting. A theoretical model is proposed which describes well our experimental observations. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) imaging of a single-layer plasma crystal was performed using a commercial plenoptic camera. To enhance the out-of-plane oscillations of particles in the crystal, the mode-coupling instability (MCI) was triggered in it by lowering the discharge power below a threshold. 3D coordinates of all particles in the crystal were extracted from the recorded videos. All three fundamental wave modes of the plasma crystal were calculated from these data. In the out-of-plane spectrum, only the MCI-induced hot spots (corresponding to the unstable hybrid mode) were resolved. The results are in agreement with theory and show that plenoptic cameras can be used to measure the 3D dynamics of plasma crystals. [ABSTRACT FROM AUTHOR]

Recent progress in experimental and theoretical studies of melting of two-dimensional (2D) plasma crystals is summarized. Several generic, equilibrium and non-equilibrium processes which can be observed and investigated in 2D complex plasmas are discussed, such as KTHNY, grain-boundary-induced, and shear-induced melting. Furthermore, the key features of the dominant plasma-specific mechanism of melting operating in 2D plasma crystals, the mode-coupling instability, are presented. The onset of the instability, which is characterized by threshold values of the experimental parameters, identifies the 'dividing line' between the regimes when 2D complex plasmas can be employed to study generic strong-coupling phenomena, and the situations when the melting occurs due to specific processes peculiar to complex plasmas. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Particle pairing in a complex plasma was experimentally studied with the emphasis on pair spatial extent and stability. Micron-size particles were suspended in the (pre)sheath area above the lower electrode in a capacitively coupled radio-frequency discharge in argon. They formed vertical pairs due to the ion wakes created by the flow of ions past particles. We discuss the confinement mecha-nism for the lower particle, resulting from a combination of the wake field and the field of non-uniform sheath. A model of particle pairs is proposed, which provides good description for the dependence of pair size and stability on experimental parameters. [ABSTRACT FROM AUTHOR]

The observadon is presented of naturally occurring pairing of particles and their cooperative drift in a two-dimensional plasma crystal. A single layer of plastic microspheres was suspended in the plasma sheath of a capacitively coupled radio-frequency discharge in argon at a low pressure of 1 Pa. The particle dynamics were studied by combining the top-view and side-view imaging of the suspension. Cross-analysis of the particle trajectories allowed us to identify naturally occurring metastable pairs of particles. The lifetime of pairs was long enough for their reliable identification. [ABSTRACT FROM AUTHOR]

A two-dimensional plasma crystal was melted by suddenly applying localized shear stress. A stripe of particles in the crystal was pushed by the radiation pressure force of a laser beam. We found that the response of the plasma crystal to stress and the eventual shear melting depended strongly on the crystal's angular orientation relative to the laser beam. Shear stress and strain rate were measured, from which the spatially resolved shear viscosity was calculated. The latter was shown to have minima in the regions with highest strain rate, thus demonstrating shear thinning. Shear-induced reordering was observed in the steady-state flow, where particles formed strings aligned in the flow direction. [ABSTRACT FROM AUTHOR]

The microstructure of a strongly coupled liquid undergoing a shear flow was studied experimentally. The liquid was a shear melted two-dimensional plasma crystal, i.e., a single-layer suspension of micrometer-size particles in a rf discharge plasma. Trajectories of particles were measured using video microscopy. The resulting microstructure was anisotropic, with compressional and extensional axes at around ±45° to the flow direction. Corresponding ellipticity of the pair correlation function g(r) or static structure factor S(k) gives the (normalized) shear rate of the flow. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper the influence of RE alloying additions (Y, Gd, Tb and Dy) on magnetic properties (Curie temperatures, low temperature magnetization, zero field cooling–field cooling curves, domain structure, room temperature magnetostriction and magnetic permeability) of amorphous alloys of type Fe82Nb2B14RE2 are carefully examined. It was shown that substituting of yttrium atoms by magnetic elements, i.e. Gd, Tb and Dy leads to (i) an increase of the Curie temperature of amorphous phase from 416K (for Fe82Nb2B14Y2) to 450K (for Fe82Nb2B14Gd2) and (ii) a decrease of magnetization in saturation (magnetic field 7T) which can be explained by antiferromagnetic Fe–RE coupling resulting in a decrease of magnetic moment calculated per magnetic atom from 2.00μB for the Fe82Nb2B14Y2 alloy (Fe in amorphous phase) to 1.51μB for the Fe82Nb2B14Tb2 alloy. It was concluded that Tb and Dy alloying additions introduce a local magnetic anisotropy responsible for significant decrease of initial magnetic permeability (about 5 times in relation to Fe82Nb2B14Y2 or Fe82Nb2B14Gd2 alloy), increase of magnetic irreversibility effect measured at 2K (about 10 times in relation to the same alloys) and appearing of the finger-print magnetic domain regions (not observed for the Fe82Nb2B14Y2 and Fe82Nb2B14Gd2 alloys). [Copyright &y& Elsevier]

The effect of rotating electric field on 3D particle clusters suspended in rf plasma was studied experimentally. Spheroidal clusters were suspended inside a glass box mounted on the lower horizontal rf electrode, with gravity partially balanced by thermophoretic force. Clusters rotated in the horizontal plane, in response to rotating electric field that was created inside the box using conducting coating on its inner surfaces ('rotating wall' technique). Cluster rotation was always in the direction of applied field and had a shear in the vertical direction. The angular speed of rotation was 104-107 times lower than applied frequency. The experiment is compared to a recent theory. [ABSTRACT FROM AUTHOR]

Abstract: The work concerns influence of rare earth elements on crystallization of Fe82Nb2B14RE2 (RE=Y, Gd, Tb, and Dy) group of amorphous alloys. The samples were obtained by typical melt spinning technique. The crystallization studies were carried out with the use of (i) differential scanning calorimetry (DSC) in the temperature range from 300K to 850K with different heating rates and (ii) standard magnetic balance (Faraday type). The crystalline structure before and after the first stage of crystallization were checked by XRD and HRTEM techniques. The measurements allow the determining crystallization temperatures, activation energies of crystallization, average size of nanograins formed during crystallization and the Curie temperatures. In the paper all the obtained results are widely discussed in the context of different rare earth alloying additions. [ABSTRACT FROM AUTHOR]

It is shown that strong electrostatic interaction of highly charged microparticles (which is common for many laboratory experiments) can significantly modify the behavior of dust acoustic waves in a complex plasma giving rise to their transition, at large wave numbers, into a new regime similar to the dust thermal mode. Examples of the dispersion curves are calculated for realistic complex plasma parameters and a comparison with a recent experiment is presented. Excellent agreement is found between the theory and the experiment. [ABSTRACT FROM AUTHOR]

The rotation of monolayer particle clusters suspended in the sheath of a rf discharge plasma was observed experimentally. The cluster rotation was driven by an electric field that rotated uniformly in the horizontal plane (“rotating wall” technique). No external magnetic field was applied. The cluster rotation velocity depended nonmonotonically on the manipulation field frequency that was much higher than the dust plasma frequency. Mechanisms of rotation are proposed based on the interplay between the electric and ion-drag forces. Possible applications of rotating electric fields in complex plasmas are discussed. [ABSTRACT FROM AUTHOR]

Dislocation nucleation and dynamics were observed in a two-dimensional plasma crystal. The observations were performed in real time at an atomistic (kinetic) level. The basic stages of edge dislocation nucleation were identified and studied, from gradual pile-up of shear strain in the crystal to eventual escape of free dislocations. After nucleation, dislocations moved supersonically with respect to the shear waves and generated shear-wave Mach cones. [ABSTRACT FROM AUTHOR]

The excitation and propagation of solitary waves is studied experimentally in a two-dimensional strongly coupled dusty (complex) plasma. A single layer with ≈5000 microspheres (8 μm diam) was suspended in an argon plasma with a neutral gas pressure of 3.0 mTorr. The measured Debye shielding parameter was κ≈1.6, where κ=a/λ is the ratio of the lattice constant a to the Debye length λ. Nonlinear, planar longitudinal waves were launched by pushing all the particles in a rectangular region at the center of the crystal in the same direction using an 18 W green laser. Compressive solitary waves with density perturbations δn/n0≲0.8 and widths ≲5a were found to propagate in the forward direction at speeds exceeding the dust acoustic speed. For small amplitude solitary waves, the relations between amplitude, width, and velocity are consistent with those predicted for Korteweg–deVries solitons. Rarefactive perturbations were not observed to evolve into solitary waves. However, oscillatory shocks were seen to move in the backward direction after the laser force was removed. [ABSTRACT FROM AUTHOR]

The ion drag force acting on dust grains was measured experimentally in a low-pressure Ar plasma in the regime of strong ion-grain coupling. Argon ions were drifting in the axial ambipolar electric field naturally present in a hot-filament dc discharge plasma. Following the method of Hirt et al. [Phys. Plasmas 11, 5690 (2004)], hollow glass microspheres were dropped into the plasma and allowed to fall due to gravity. The ion drag force was derived from the particle trajectory deflection from the vertical direction. The result is in reasonable agreement with a theoretical model that takes strong ion-grain coupling into account. [ABSTRACT FROM AUTHOR]

The propagation of transverse waves in a two-dimensional particle suspension in a plasma is studied in the solid and liquid phase. The different states of the suspension are realized by raising the kinetic temperature of the dust particles with a new laser method. An additional laser beam is used to excite shear waves and the wave is observed by videomicroscopy in terms of the individual velocities of the dust particles. For recovering the spatial wave patterns the method of singular value decomposition is applied and compared with the method of spatial Fourier analysis of complex wave numbers. In the solid phase, weakly damped waves are found which follow the expected dispersion relation. In the liquid phase the existence of strongly damped waves is demonstrated. The real part of the wave number is in overall agreement with the predictions of the Quasi Localized Charge Approximation model for a two-dimensional system. The damping of the waves is discussed. [ABSTRACT FROM AUTHOR]

A method has been developed to heat and control temperature in a two-dimensional monolayer dusty plasma. A monolayer of highly charged polymer microspheres was suspended in a plasma sheath. The microspheres interacted with a Yukawa potential and formed a triangular lattice. Laser manipulation was used to apply random kicks to the particles. Two focused laser beams were moved rapidly around drawing Lissajous figures in the monolayer. The kinetic temperature of the particles increased with the laser power applied, and above a threshold a melting transition was observed. Characteristics of a thermal equilibrium of the laser-heated dusty plasma in solid and liquid states are discussed. [ABSTRACT FROM AUTHOR]

The interaction of a focused powerful laser beam with micron-sized melamine formaldehyde (MF) particles was studied experimentally. The microspheres had a thin palladium coating on their surface and were suspended in a radio frequency argon plasma as a single layer (plasma crystal). A particle hit by the laser beam usually accelerated in the direction of the laser beam, consistent with the radiation pressure force mechanism. However, random-direction acceleration up to the speeds on the order 1 m/s was sometimes observed. Rocket-force mechanism is proposed to account for the random-direction acceleration. Similar, but much less pronounced, effect was also observed for MF particles without palladium coating. [ABSTRACT FROM AUTHOR]

We point out a deficiency in our previous analytic calculation of the ion drag force for conditions of the experiment by Nosenko et al. [Phys. Plasmas 14, 103702 (2007)]. An inaccurate approximation is corrected and the ion drag force is recalculated. The improved model yields better overall agreement with the experimental results as compared to the original calculation. [ABSTRACT FROM AUTHOR]

The full melting of a two-dimensional plasma crystal was induced in a principally stable monolayer by localized laser stimulation. Two distinct behaviors of the crystal after laser stimulation were observed depending on the amount of injected energy: (i) below a well-defined threshold, the laser melted area recrystallized; (ii) above the threshold, it expanded outwards in a similar fashion to mode-coupling instability-induced melting, rapidly destroying the crystalline order of the whole complex plasma monolayer. The reported experimental observations are due to the fluid mode-coupling instability, which can pump energy into the particle monolayer at a rate surpassing the heat transport and damping rates in the energetic localized melted spot, resulting in its further growth. This behavior exhibits remarkable similarities with impulsive spot heating in ordinary reactive matter. [ABSTRACT FROM AUTHOR]

Spontaneous formation of spinning pairs of particles, or torsions, is studied in a single-layer complex plasma crystal by reducing the discharge power at constant neutral gas pressure. At higher gas pressures, torsions spontaneously form below a certain power threshold. Further reduction of the discharge power leads to the formation of multiple torsions. However, at lower gas pressures the torsion formation is preceded by mode-coupling instability (MCI). The crystal dynamics are studied with the help of the fluctuation spectra of crystal particles' in-plane velocities. Surprisingly, the spectra of the crystal with torsions and MCI are rather similar and contain hot spots at similar locations on the (k,ω) plane, despite very different appearances of the respective particle trajectories. The torsion rotation speed is close (slightly below) to the maximum frequency of the in-plane compressional mode. When multiple torsions form, their rotation speeds are distributed in a narrow range slightly below the maximum frequency. [ABSTRACT FROM AUTHOR]

Domains of the square lattice have been observed in a quasi-two-dimensional binary complex plasma. The longitudinal and transverse modes of the wave spectra were measured. To compare with the experiment, Langevin dynamics simulations of a binary mixture were carried out, where the non-reciprocal interactions between different species were modeled with a point-wake Yukawa potential. A strong dependence of the wave spectra on the relative magnitude of the point-wake charge is revealed. [ABSTRACT FROM AUTHOR]

An interferometric imaging technique has been proposed to instantly measure the diameter of individual spherical dust particles suspended in a gas discharge plasma. The technique is based on the defocused image analysis of both spherical particles and their binary agglomerates. Above a critical diameter, the defocused images of spherical particles contain stationary interference fringe patterns and the fringe number increases with particle diameters. Below this critical diameter, the particle size has been measured using the rotational interference fringe patterns which appear only on the defocused images of binary agglomerates. In this case, a lower cutoff limit of particle diameter has been predicted, below which no such rotational fringe patterns are observed for the binary agglomerates. The method can be useful as a diagnostics for complex plasma experiments on earth as well as under microgravity conditions. [ABSTRACT FROM AUTHOR]

New complex-plasma facility, Plasmakristall-4 (PK-4), has been recently commissioned on board the International Space Station. In complex plasmas, the subsystem of μm-sized microparticles immersed in low-pressure weakly ionized gas-discharge plasmas becomes strongly coupled due to the high (103-104 e) electric charge on the microparticle surface. The microparticle subsystem of complex plasmas is available for the observation at the kinetic level, which makes complex plasmas appropriate for particle-resolved modeling of classical condensed matter phenomena. The main purpose of PK-4 is the investigation of flowing complex plasmas. To generate plasma, PK-4 makes use of a classical dc discharge in a glass tube, whose polarity can be switched with the frequency of the order of 100 Hz. This frequency is high enough not to be felt by the relatively heavy microparticles. The duty cycle of the polarity switching can be also varied allowing to vary the drift velocity of the microparticles and (when necessary) to trap them. The facility is equipped with two videocameras and illumination laser for the microparticle imaging, kaleidoscopic plasma glow observation system and minispectrometer for plasma diagnostics and various microparticle manipulation devices (e.g., powerful manipulation laser). Scientific experiments are programmed in the form of scripts written with the help of specially developed C scripting language libraries. PK-4 is mainly operated from the ground (control center CADMOS in Toulouse, France) with the support of the space station crew. Data recorded during the experiments are later on delivered to the ground on the removable hard disk drives and distributed to participating scientists for the detailed analysis. [ABSTRACT FROM AUTHOR]

A defocusing imaging technique has been used as a diagnostic to identify binary agglomerates (dimers) in complex plasmas. Quasi-two-dimensional plasma crystal consisting of monodisperse spheres and binary agglomerates has been created where the agglomerated particles levitate just below the spherical particles without forming vertical pairs. Unlike spherical particles, the defocused images of binary agglomerates show distinct, stationary/periodically rotating interference fringe patterns. The results can be of fundamental importance for future experiments on complex plasmas. [ABSTRACT FROM AUTHOR]

The influence of the elemental composition of strip amorphous alloys Fe80.0Si6.0B14.0, Fe78.5Ni1.0Mo0.5Si6.0B14.0; Fe73.1Cu1.0Nb3.0Si15.5B7.4; Fe51.7Ni21.7Cr6.2Mo0.6V1.5Si5.2B13.1 on corrosion resistance in 0.5 M aqueous solutions of NaCl, HCl, and KOH at T = (293 ± 1) K was investigated. The high corrosion resistance of Fe51.7Ni21.7Cr6.2Mo0.6V1.5Si5.2B13.1 and Fe73.1Cu1.0Nb3.0Si15.5B7.4 alloys in aggressive environments was established. Electrochemical parameters obtained both by the method of cyclic voltammetry and electrochemical impedance spectroscopy (EIS) indicate the formation of more durable surface layers in a 0.5 M potassium hydroxide aqueous solution on these alloys. The Cl– ions (especially at low pH) under their long-term action are the more aggressive oxidizers of amorphous alloys compared to OH– ions. During the passivation film formation in highly aggressive environments such alloy elements, which do not participate in this process, actively dissolve, and the main film-forming elements accumulate under the film, thus improving its protective properties. [ABSTRACT FROM AUTHOR]

In an argon plasma of 20W rf discharge at a pressure of 1.38 Pa, a stable highly ordered monolayer of microparticles is suspended. We observe spontaneous particle pairing when suddenly reducing the gas pressure. Special types of dynamical activity, in particular, entanglement and cooperative movements of coupled particles have been registered. In the course of the experiment first appeared single vertical pairs of particles, in further they gradually accumulated causing melting of the entire crystal. To record pairing events, the particle suspension is side-view imaged using a vertically extended laser sheet. The long-lasting pre-melting phase assured the credible recording and identification of isolated particle pairs. The high monolayer charge density is crucial to explain the spontaneous pairing events observed in our experiments as the mutual repulsion between the particles comprising the monolayer make its vertical extend thicker. [ABSTRACT FROM AUTHOR]

The kinematics of dust particles during the early stage of mode-coupling induced melting of a two-dimensional plasma crystal is explored. It is found that the formation of the hybrid mode causes the particle vibrations to partially synchronize at the hybrid frequency. Phase- and frequency-locked hybrid particle motion in both vertical and horizontal directions (hybrid mode) is observed. The system self-organizes in a rhythmic pattern of alternating in-phase and antiphase oscillating chains of particles. The spatial orientation of the synchronization pattern correlates well with the directions of the maximal increment of the shear-free hybrid mode. [ABSTRACT FROM AUTHOR]

• Form of used TiO 2 affects microstructure of Zn 2 TiO 4 :Mn ceramics and Mn charge state. • Ceramics become denser and show grain growth with increase of annealing temperature. • Ceramics made from anatase show abnormal grain growth and preferred grain orientation. • Ceramics made from rutile have larger content of Mn4+ and smaller content of Mn2+. • Rutile is preferable for making Mn4+-activated red phosphor. The influence of crystalline form of TiO 2 (rutile and anatase) on microstructure and optical properties of Zn 2 TiO 4 ceramics doped with manganese has been investigated by X-ray diffraction, Scanning electron microscopy, as well as by optical and electron paramagnetic resonance (EPR) methods. The ceramics was produced by sintering in the air at temperatures in the range of 900–1200 °C of a mixture of ZnO and TiO 2 powders. Both types of ceramics became denser and demonstrated growth of grains in size with the increase of annealing temperature. Meanwhile, the ceramics made from anatase show abnormal grain growth and formation of preferred crystallographic grain orientation. The grain size of the ceramics made from anatase was larger for all annealing temperatures and increased from submicron up to tens of microns at 1100 and 1200 °C. This is attributed to known stimulating role of anatase in the formation of cubic Zn 2 TiO 4 phase and/or anatase-to-rutile transformation. The concurrent optical absorption, photoluminescence (PL) and EPR studies of the ceramics revealed Mn2+ and Mn4+ ions in the Zn 2 TiO 4 crystal phase. For all annealing temperatures the Zn 2 TiO 4 made from anatase have larger content of Mn2+, while the Zn 2 TiO 4 made from rutile show larger content of Mn4+ and about twice higher intensity of red PL caused by 2E→4A 2 spin forbidden transitions of Mn4+. The PL intensity decreased in several times at high annealing temperatures starting from 1100 °C for the ceramics made of anatase, whereas from 1200 °C for that made of rutile. This effect strongly correlates with densification of ceramic's microstructure and is ascribed mainly to the reduction of Mn4+ to Mn2+. It is concluded that rutile is preferable for creating Mn4+ centers in the Zn 2 TiO 4 and making Mn4+-activated red phosphor. [ABSTRACT FROM AUTHOR]

By the method of cyclic voltammetry, we study the corrosion resistance of amorphous and crystalline Al87Ni8Y5 alloys in a 0.5 M aqueous NaCl solution for different sweep rates of potential of the electrode surface (10, 20, 50, and 100 mV/sec). We find the electrochemical characteristics of crystalline Al, Ni, and Y in solutions of sodium chloride. The diffusion coefficients of Al3+ and Ni2+ ions are determined. It is shown that the alloys are ionized in this solution in three stages and the diffusion rate of Al3+ from the near-electrode layer is lower than for Ni2+ ions. [ABSTRACT FROM AUTHOR]

Powder metallurgy methods are used to produce soft magnetic compact materials from amorphous and nanocrystalline alloys. Toroid-shaped samples are warm-pressed from nanocrystalline FeSiBCuNb alloy powders and SFP-012A resin binder. The method does not require additional thermal treatment and the samples are ready to use. The key influence on the properties of soft magnetic powder materials is produced by ferromagnetic filling factor (FFF). The optimal experimental conditions to make samples with the minimum porosity and maximum FFF are determined. The density of the samples depending on compaction parameters and resin content is established. [ABSTRACT FROM AUTHOR]

Measurements are reported for the radiation pressure and gas drag forces acting on a single melamine-formaldehyde microsphere. The radiation pressure force coefficient q, which would be unity if all incident photons were absorbed, has the value q = 0.94 ± 0.11. For argon, the Epstein gas drag force coefficient δ, which would be unity if impinging molecules underwent specular reflection, has the value δ = 1.26±0.13 as measured with our single-particle laser acceleration method, or δ= 1.44±0.19 as measured using the vertical resonance method. [ABSTRACT FROM AUTHOR]

Experiments and simulations are reported for a monolayer plasma crystal that is disturbed by an extra particle moving in a plane below the monolayer. Numerical simulations and experiments are performed to find an explanation for the motion of the extra particle. In contrast to earlier simulations where an extra particle did not move spontaneously as in the experiment, here an ion wakefield downstream of the monolayer of particles is included. This resulted in the spontaneous motion of an extra particle as in the experiment, so that it is concluded that the wakefield produces this motion. In both the experiment and the simulation a trend is observed where the orbit of an extra particle becomes more crooked and less energetic when the gas damping is stronger. The simulation reveals that the energy of the extra particle exhibits distinctive transitions between three regimes. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Four ZnS nanopowders containing an uncontrolled impurity of manganese were studied using EPR technique. The powders with the average sizes (6...8 nm) were synthesized by either joint or sequential decomposition of diethyldithiocarbamate complexes of zinc and europium in high-boiling solvents at various temperatures. All samples demonstrated the EPR signal that is not typical for ZnS powders with µm-sized particles. Computer simulation showed that EPR spectra of all the samples could be fitted by two components. The first component with g = 2.0022 ± 0.0002, (63.5 0.5) 10-4 cm-1 A = - ± × , 0 4 1 4 3.5 10 cm- - b × was assigned to Mn2+ ions in the cubic surrounding, Mn(C). The parameters of the second component were g = 2.0022 ± 0.0002, (63.5 0.5) 10-4cm-1 A = - ± × , 0 () 4 1 2 36 1 10 cm- - b = - ± ×; this component was attributed to Mn2+ ions associated with a planar lattice defect (stacking fault), Mn2+(D). The ratio of centers amounts Mn2+(C)/Mn2+(D) for the samples studied was 2.1/1 (in the samples 1 and 4) and 1.7/1 (in the samples 2 and 3), respectively. EPR of Mn2+ ions was shown to be an effective method for detecting planar lattice defects in ZnS nanoparticles. [ABSTRACT FROM AUTHOR]

We have studied the EPR of Mn2+ ions in three samples of cubic nano-ZnS made by different technologies and having different nanoparticle sizes. Manganese occurs in the samples as an uncontrolled impurity. The EPR spectra can be described by two components: the spectrum of the Mn2+ in a cubic environment (Mn2+(C)) with parameters g = 2.0022 ± 0.0002, A = (–63.5 ± 0.5)·10–4 cm–1, 0 b4 ≥ 3.5·10–4 cm–1; and the spectrum of the Mn2+ ion associated with a planar lattice stacking fault (Mn2+ (F)), with parameters g = 2.0022 ± 0.0002, A = (–63.5 ± 0.5)·10–4 cm–1, b 2 0 = (–36 ± 1)·10–4 cm–1. The ratio of the number of centers Mn2+(C)/Mn2+(F) is 2.1:1 for sample 1 and 1.7:1 for samples 2 and 3. Planar stacking faults are typical lattice faults for cubic nano-ZnS. EPR of the Mn2+ ions lets us monitor the presence of these ions. [ABSTRACT FROM AUTHOR]

Research results are given for use of FluMag high-magnesia flux mainly containing brucite Mg(OH) during steel production in oxygen converters and electric steel smelting furnaces. Data are provided for FluMag flux physicochemical properties. The effect of using the flux in different periods of converter smelting on molten slag chemical composition and other process parameters, and also the increase in efficiency of applying a slag skull the converter lining are determined. Comparative analysis is carried out for molten slag foaming during steel smelting in electric furnaces and formation of a slag skull on the furnace lining with the use of magnesia fluxes of different compositions. [ABSTRACT FROM AUTHOR]

A unique type of quasi-two-dimensional complex plasma system was observed which consisted of monodisperse microspheres and their binary agglomerations (dimers). The particles and their dimers levitated in a plasma sheath at slightly different heights and formed two distinct sublayers. The system did not crystallize and may be characterized as a disordered solid. The dimers were identified based on their characteristic appearance in defocused images, i.e., rotating interference fringe patterns. The in-plane and interplane particle separations exhibit nonmonotonic dependence on the discharge pressure. [ABSTRACT FROM AUTHOR]

Structures of low-dimensional ZnS powders doped with Cu, Co, and Mn were studied using Mn ions as a paramagnetic probe. Particle sizes were 5-7 μm for ZnS:Cu, 7-10 μm for ZnS:Co, and 50-200 nm for ZnS:Mn. Spin-Hamiltonian parameters describing electron paramagnetic resonance spectra were obtained. Analysis of the spectra revealed that ZnS:Cu powder has cubic structure, ZnS:Mn powder has hexagonal structure with orthorhombic distortion, whereas ZnS:Co powder is a mixture of cubic and hexagonal phases in a 1:10 ratio. [ABSTRACT FROM AUTHOR]