Interest in core–shell-like structures Ni/Ti, Ni/TiO 2 and NiO/TiO 2 increases considering their potential application in photovoltaics, as photocatalysts for H 2 generation and CO 2 methanation, anodes in supercapacitors and fuel cells, etc. In this work, the powders were produced from Ti-Ni-Hf and Ti-Ni-Zr high-temperature shape memory alloys by the spark erosion method in cryogenic liquids. The morphology and fine structure of the nanoparticles were investigated by transmission electron microscopy (TEM), high-resolution (HRTEM) and energy-filtered (EFTEM) transmission electron microscopy. The elemental composition was measured by energy-dispersive X-ray spectroscopy (EDX). It was found that a few types of nanoparticles can be formed during spark erosion of Ti-Ni-Hf and Ti-Ni-Zr alloys in cryogenic liquids. The finest fraction (5–20 nm) consists of a mixture of TiO and NiO phases. At the same time, “core–shell” structures were observed in particles from tens to hundreds of nanometers in size. The core–shell nanoparticles have FCC structure. The core has a banded structure, and its composition is close to the eutectic between Ni and Ni 3 Ti. The shell composition is almost TiO. The formation mechanism of “core–shell” nanoparticles based on the “oxygen pump” process was proposed. Coalescence and remelting of the partially oxidized Ti and Ni particles, condensed from vapor, occur. Ni atoms tend to diffuse inside agglomerates while Ti atoms—are to the surface due to the strong affinity of Ti to the oxygen.

Plasmon resonance in metal nanoparticles depends on numerous factors. It could be characteristics of the particle - material, size and shape. And also, it could be characteristics of the surrounding medium. Localized surface plasmon resonance (LSPR) in spherical gold nanoparticles is studied. Characteristics of LSPR are controlled by changing dielectric permittivity of the surrounding medium in two ways. The first way consists of adding a transparent dielectric material to the nanoparticle sample. The main idea of the second way is to increase particle polarization using the time varying electric field. This method could be used to control characteristics of SRP in different applications.

The current transfer through a two-layer structure saturated with absorbed water, each layer of which consists of pressed ZrO2 nanoparticles with two sizes (10 and 20 nm), has been studied. The structure was obtained using the isostatic pressing the ZrO2 + H2O powders. The form of current–voltage characteristics inherent to the studied structure, that has diode properties with the rectification coefficient close to 3, has been explained by the appearance of a potential barrier at the interlayer boundary.

Performed in this work is a comparative analysis of photoluminescence, photoluminescence excitation and EPR spectra of gas-phase fraction of powdery ZnS:Mn obtained using the self-propagating high-temperature synthesis from the charge with a different Zn/S ratio. It was found that the size of particles in the synthesized materials was with in the range 10-300 nm. The size that is comparable with the Debye screening length (L). The luminescence and other characteristics of the studied material were found to differ significantly from the bulk ones. This finding has been explained by a unique energy structure of crystallites. Zn/S ratio has been shown to impact significantly on the crystallites sizes and the amount of incorporated Mn. The largest crystallite sizes and the high Mn content were observed in the powder synthesized with a stoichiometric Zn/S ratio, while the minimum particle sizes -in the powders synthesized with S excess. At sulfur excess, the size of particles is close to the Debye length, and carriers can freely migrate in the conduction band to the surface, where mainly nonradiative recombination occurs. The stoichiometric Zn/S ratio or Zn excess in the charge results in the increase of the particle sizes up to the values 2L <= d <= 3L. Such materials are characterized by minimization of non-radiative losses. This finding opens new possibilities for ZnS application.

A model has been proposed to describe the potential barrier that appears during interaction of two compacted layers consisting of hydrophilic oxide nanoparticles of different sizes in each layer upon saturation of this structure with adsorbed water. The dependence of the space charge density of the compacted powder material on the density of particles in it has been theoretically calculated. The distribution of the potential over the thickness of contact between two layers consisting of nanoparticles with different sizes has been obtained.

The ZnS:Mn, Mg powder is fabricated by self-propagating high-temperature synthesis with the simultaneous introduction of Mn and Mg impurities. It is found that the simultaneous introduction of Mn and Mg impurities leads to the nonuniform distribution of manganese forming regions with a lower and higher Mn concentration. In the latter case, the manganese ions form paramagnetic clusters. At the same time, numerous centers of self-activated luminescence form in the synthesized ZnS:Mn, Mg due to mechanical stress and lattice strain. Additional annealing leads to a more uniform Mn distribution in the formed ZnS:Mn, Mg phosphor, which is accompanied by an increase in the intensity of the manganese photoluminescence band and quenching of the self-activated luminescence band.

A simple and cheap spark erosion method was used to produce Cu/Cu2O core-shell nanoparticles. Morphological and structural studies of the obtained material showed that it consists of Cu and Cu/Cu2O core-shell nanoparticles with sizes about 9-25 and 30-50 nm, respectively. The latter demonstrate ferromagnetic properties (specific saturation magnetization is 0.27 A.m(2)/kg) without additional heat treatment in oxidizing environment. The causes of the ferromagnetic properties of the material obtained are analyzed.

ZnO nanomaterial has many practical applications in particular in microelectronics. ZnO nanopowder was obtained by spark erosion method in water. According to the X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmitting electron microscopy (TEM) data powder consists of agglomerates of ZnO particles with average size of 25 nm. Photoluminescent study shows that spark eroded ZnO nanopowder has a wide photoluminescence (PL) peak between 350 and 700 nm. It consists of minimum 7 lines which can be attributed to the donor-acceptor recombination, impurities and defects such as zinc and oxygen vacancies, interstitial Zn and surface dislocations. Therefore, the spark eroded ZnO nanopowder demonstrates a self-activated photoluminescence.

As a part of this work colloidal solutions of Fe oxides particles were fabricated by three different methods. The spark erosion method (SE), a wet mechanical grinding with ultrasonic frequency treatment in a ball mill (base liquid - water) with a surfactant sodium dodecylbenzenesulphate (SDBS)) and thermochemical polyol synthesis method (base liquid - polyethylene glycol) were carried out. The paper contains studies of particles size distributions. The particle size distributions were done with the laser sedimentograph Mastersizer 2000 with a module of liquid dispersion HydroS (Malvern Instruments, UK). The morphology and local phase composition was examined using the transmission electron microscope ΠM-Y (upgraded) equipped with a digital imaging system CA-01A. According to the research results, a conclusion about relevance of size of the particles obtained by the forementioned methods for the production of magnetic fluids needs was made in the paper.

Ferromagnetic nanoscale Co particles in a nonferromagnetic matrix can be used as materials for spintronics and a magnetoelectronics engineering. Highly dispersive Co particles were produced by spark erosion method in distilled water, ethanol and toluene. The phase composition, crystalline structure and magnetic properties were studied. The analysis of the phase composition of spark eroded powders confirms contents alpha-Co and beta-Co phases. The biggest fraction of the alpha-phase was observed in the powder produced in water (approx. 5.3 pct.), while the smallest fraction (approx. 4.3 pct.) - in toluene. A fraction of the alpha-Co in the all studied powders increases as the annealing temperature grows. The spatial dimensions of the alpha-Co crystal phases are typically much smaller compared to beta-Cos. The intensity of a martensitic transformation is low in the studied interval of temperatures and small fraction of alpha-Co can be bound to the presence of large-size particles at samples for which a martensitic transformation is possible.

The influence of Zn/S ratio in the charge on structural and optical properties of ZnS:Mn powders produced by high-temperature self-propagated synthesis was investigated. The samples was shown to consist of mixed-polytypes ZnS crystallites with hexagonal (2H) and cubic (3C) phases, the contribution of the latter increases with the sulfur content in the charge. The most homogeneous size distribution were found at stoichiometric Zn/S ratio. The Zn/S relation affects the Mn incorporation into ZnS lattice. The highest quantity of incorporated Mn is observed at stoichiometric Zn/S relation while lowest one is realized at Zn excess. Besides, the distribution of manganese ions in the blocks, which compose the crystallites, was found to be inhomogeneous, their concentration decreases from crystallites surface to the depth. Mn ions are nearer to the surface in ZnS:Mn synthesized with Zn excess. At Mn concentration in the charge of 1 wt% the shift of ZnS band edge to low energy side is observed, that is ascribed to formation of solid solution ZnS–MnS with lower band gap value.

This work was devoted to ultrafine ZnS:Cu powders obtained by self-propagating high-temperature synthesis (SHS) using NaCl as a flux. Powder particles size and morphology were characterized by scanning electron microscopy (SEM). Elemental composition was measured by local energy-dispersive X-ray spectroscopy (EDS). Photoluminescence (PL) and luminescence excitation (PLE) spectra were studied. The influence of different amount of NaCl as a flux in synthesis of ZnS:Cu on its elemental composition and luminescent characteristics was investigated.

Fine ZnS:Cu, obtained by method of self-propagating high-temperature synthesis was investigated. As flux in the mixture NaCl was used, Zn and S were taken in stoichiometric ratio; Cu concentration in charge consisted ~1.5 wt.%. Using SEM data, it was established that obtained ZnS:Cu consists from two fractions—first with particles sizes ~10 μm and more, and other with sizes 50–500 nm. It was established that composition of ZnS:Cu fractions was essentially different. According to EDS data, Cu concentration in particles of fraction with 50–500 nm sizes consists ~2 wt.%, and in particles with sizes ~10 μm and more the presence of Cu was not detected. The reasons that lead to the selective doping of particles in dependence on their size and also the role of NaCl in processes undergoing during synthesis of material are discussed.

We performed a comparative analysis of photoluminescence spectra of micro- and meso-fractions of powdery ZnS:Mn obtained by self-propagating high-temperature synthesis. It was found that manganese ions take part in excitation of ZnS self-activated luminescence. From the data on photoluminescence excitation spectra it was established that excitation of emitting Mn ion in ZnS:Mn meso-fraction is realized with participation of sensitizers (MnZn) and without charge carriers excited at interband absorption. This is explained within a model according to which, at particles size smaller than double length of the space charge region, the particle potential barrier becomes lower and Fermi level decreases owing to summation of space charge regions of opposite particle surfaces, i.e., the depletion region extends over the total particle volume.

The photoluminescence (PL) and PL excitation (PLE) spectra of undoped and thermally doped with Mn ZnS single crystals are studied. In the PL spectra, the bands caused by Mn-related and self-activated (SA) emission centers were observed. A number of narrow peaks whose intensity enhanced with increasing Mn content were found in the PLE spectra of SA emission. The same peaks were present in the PLE spectra of the Mn-related emission band. Some of these peaks were previously observed in the absorption spectra and attributed to Mn2+ ions. The appearance of Mn-related peaks in the PLE spectra of SA emission is explained by excitation transfer from the Mn2+ ions to SA emission centers. The conditions required for this transfer and possible mechanisms of the process are discussed.

Compression tests are carried out at room temperature with the as-cast and spark-plasma sintered (SPS) specimens of Ni49.0-Mn28.5-Ga22.5 (at.%) and Ni63-Al37 (at.%) alloys.For both systems, ductility of the SPS compacts increases more than by one order of magnitude.Compressive strength of Ni-Mn-Ga alloy increases from 180-240 MPa for induction melted specimens to 510-815 MPa for spark-plasma sintered specimens, depending on the regimes of processing, and for Ni-Al alloy, from 760 to 1310 MPa.Fracture stress of Ni-Mn-Ga and Ni-Al specimens raise from 185-215 to 1170 MPa and from 790 to 1870 MPa, respectively.The SEM and XRD investigations reveal that sintered samples of both systems have a composite structure, which contains the micron-size metallic particles bound by the binder phase.This phase consists of Ni 3 Al and Al 2 O 3 phases in case of Ni-Al alloy and consists of MnO with apparently small amount of Ni 3 Ga phase in case of Ni-Mn-Ga alloy.As assumed, this phase strengthens the grain boundaries.This one, in conjunction with reduction of the grain size, the manifold morphology of the Ni-Mn-Ga specimens consolidated from the hollow particles, the presence of extra ductile -phase in Ni-Al particles, provides the enhancing mechanical properties of alloys fabricated by means of the SPS method.

Investigated in this work were the photoluminescence spectra and luminescence excitation spectra of powered ZnS:Cu, obtained using the method of selfpropagating high-temperature synthesis (SHS) with addition of NaCl and MgCl 2 as a fluxing agent into the charge and without them.It was shown that increasing the amount of fraction with the particle sizes ≤5 nm in powdered ZnS:Cu-SHS, where fluxing agents are present in the charge, is caused by the decrease in temperature inside the reactor in the course of the synthesis reaction.Besides, related increasing the intensity of the PL blue band with λ max ~ 450…465 nm in powdered ZnS:Cu-SHS/MgCl 2 , which is associated with redistribution of the copper impurity in the bulk of microcrystals, probably, occurring as a result of increasing the partial pressure of Cl during synthesis.

Ni-Mn-Ga-based magnetic shape memory materials were elaborated by spark plasma sintering method. Micron sized particles were prepared by spark-erosion method in liquid argon and liquid nitrogen from preliminary melted magnetic shape memory master alloys Ni-28.5Mn-22.5G at.%. Powders were annealed in H2 gas atmosphere before sintering. Depending on the cryogenic liquids the morphology of particles alternated between spherical solid and hollow balls. The conditions of spark eroded powder elaboration strongly effect on the morphology, martensitic behavior, and structure of sintered samples. In particularly, martensite has 5M structure in bulk material; 14M and non-modulated martensites were found in annealed powders and sintered compacts correspondingly.