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Accumulation of microcracks in response to point impact damage in MgAl2O4 ceramics doped with Cr3+ ions has been studied using acoustic emission measurements. The results demonstrate that the maximum crack length at a higher chromium concentration in the ceramics is smaller than that at lower doping levels. By contrast, doping with LiF (in addition to Cr3+) reduces the decrease in microcrack length caused by chromium oxide.

We obtained a Raman spectrum for a surface layer of porous carbon ceramic (porosity ≈5%) of ≈80 nm thick. The analysis of the spectrum showed that the ceramics contain crystals of silicon carbide 6H‑SiC and silicon. The destruction of ceramics by diamond microcrystals resulted in fractoluminescence (FL). Its spectrum contained two bands at 1.6 and 1.9 eV. The first is emerged at the destruction of silicon crystals, and the second is emerged at 6H-SiC crystals. We obtained the time dependence of the intensity of the fractoluminescence signals with a time resolution of 2 ns. Three types of signals were observed: one is formed when the 6H-SiC crystals are destroyed; the second is formed when silicon crystals are destroyed; the third is formed when these crystals are simultaneously destroyed. The appearance of signals is associated with the formation of cracks arising from the breakthrough of barriers formed at the intersection of slip planes of dislocations in silicon carbide and silicon crystals. The size of cracks in 6H-SiC has been estimated: the smallest is 5.5 nm, and the largest is ≈18 nm.

The mechanisms of radiative recombination and electroluminescence in the structures based on the films of perovskite nanocrystals CsPbBr3 in the matrix of a semiconductor polymer MEH-PPV have been considered. It has been shown that two mechanisms determine the electroluminescence intensity in light-emitting field-effect transistors with active layers based on the MEH-PPV films:CsPbBr3 (nanocrystals): recombination of the charged carriers injected into the polymer matrix and recombination at the interface polymer/perovskite nanocrystals. The results of theoretical and experimental studies have shown that the superlinear dependence of the electroluminescence intensity on the level of electrical excitation in the light-emitting field-effect transistors based on MEH-PPV:CsPbBr3(nanocrystals) is due to the mechanism of electron tunneling through a potential barrier at the electrode.

It is found using triboluminescence (TL) that nanocrystals of silicon (ncSi) with linear dimensions of about 4 nm are formed from a single crystal of silicon (Si) under friction. The time dependence of the intensity of TL signals is investigated. It consists of many superimposed signals. An analysis of their dynamics shows that nanocrystals are located on the microcrack faces formed during fracture. At the same time, a powder flies out of the friction region. Using the photoluminescence (PL) and Raman spectroscopy methods, the size of silicon nanocrystals in the powder was determined. It is about 2.2 nm. Probably, microcracks grow further in the time interval between friction and recording the Raman and PL spectra (several hours), which leads to an approximately twofold decrease in the size of nanocrystals.

Mechanoluminescence (ML) from deformed ductile materials is caused by sliding of charged dislocations. The main source of the ML in loaded brittle solids is the interatomic bond breakage. In this work, the ML from impact damaged ductile ZnS ceramics was studied. It was revealed that the time series of ML pulses exhibited two well-separated peaks. A two-stage ML excitation of this kind in ZnS ceramics was observed when the applied load exceeded an ultimate plastic deformation. The positions of each peak along the time axis were found to be dependent in different ways on physical and mechanical properties of crystallites that constituted the given ceramics. The investigated ceramics were produced by four different technological methods. The obtained samples differing in the dimensions of grains and separation of grain boundaries were tested. The statistical analysis of a temporal pattern of the ML lighting showed that the mechanisms of excitation of the two peaks were not the same. The first ML peak was assigned to the plastic deformation preceding the ceramics cracking. The second peak originated from the interatomic bond breakage in nucleated and growing cracks.

The spectra of the plasma emitted from the studied samples consist of several dozens of narrow bands superimposed on each other. Tables of spectral lines were used to interpret the spectra. It turned out that the largest number of bands corresponds to the radiation of positively charged ions and atoms of elements that make up the crystal lattices of minerals that make up the studied rocks. Thus, the spectra of the plasma emitted from quartz corresponded to the radiation of atoms and positively charged silicon ions, the charge of which varied from 1 to 4, as well as atoms and positively charged oxygen ions, the charge of which varied from 1 to 3. Positively charged ions and atoms of Si, O, K, Ca, Al and Na, which are part of the crystal lattices of quartz and feldspar, flew out of granites. Positively charged ions and Ca, C and O atoms flew out of the calcite.

The ion-implantation of silica is widely used in optoelectronics and neighboring areas. Si + ions serve for formation of clusters/nanocrystals in components of microelectronic devices; Ge+, P+, and B+ are used for controlling refraction index in lightguides. All enumerated ions interact chemically with oxygen atoms in SiO2, thus shading the stoichiometric distortions caused by direct impact interactions of particles with a host. In this research, the optically-active defects in the silica network were induced by embedding of chemically inert Ar + ions and thermal neutrons. A set of bands belonging to neutral oxygen vacancies (≡Si-Si≡), non-bridging oxygen hole centers (NBOHC) and some other point defects were detected in the photoluminescence spectra of implanted/irradiated samples. The intensity variation of the bands at the Ar + fluence increase was found to be caused by a competition between defect nucleation and their annealing or/and concentration quenching at high fluence. The ionization of atoms by charged particles resulted in the multivariant spectral manifestation of the defects of the same type due to their arrangement in differently distorted host localities. The diversification of defects produced by neutrons was lesser, because the neutron impact on the silica host was limited by the interactions with nuclei.

The growth rate and size of microcracks, formed in the surface layer of a heterogeneous natural solid (sandstone) under friction were studied via triboluminescence. It was discovered that destruction of the crystal lattice of plagioclase and quartz, composing sandstones, induces triboluminescence signals. Each s-ignal corresponds to a microcrack, whose surface contains electronically excited free radicals ≡Si–O– and Fe3+ ions. The size and growth rate of microcracks were assessed by means of analysis of the rate and duration of the buildup of these signals. The growth rate of microcracks turned out to be less than the elastic wave velocity (~700 m/s) and varied from ∼380 to ∼650 m/s. The size of microcracks varied from ∼4 to ∼7 μm. It was assumed that the variation in the size and growth rate of microcracks were caused by differences in value of the barriers, upon breaking which the microcracks appear.

In contrast to damage accumulation in rocks subjected to constant or growing load wherein local failures increase with time, the strongest fracture events at the shock forcing occur at the very beginning of the loading. An inverse trend in the stress variation could be expected to affect some parameters of the rock behavior specific for a quasi-static pressure exposure. In this study, shock waves in uniaxially compressed granites were generated by an electric discharge, and the nucleation of microcracks was detected by the acoustic emission (AE) method. The experiment represented some conditions, under which deep underground rocks response on the impact forcing (explosions, shocks, etc.). The compression varied from zero to a pre-damage level. Fine-grained Sesam Black granite (grain size ∼1 mm) and coarse-grained Rapakivi granite (5–7 mm) were tested. The energy release distributions in all AE time series followed a Gutenberg-Richter type relation (power law) in both compressed and free samples with a departure from the log-linear dependences for the most intensive AE peaks. At the same time in a compressed fine-grained sample, a high-energy reminder of the power law distribution followed a well-defined exponential (Poisson-like) function; in coarse-grained granite, the higher-energy part of the energy distribution could not be described with any explicit expression. The specificities in the mechanical behavior of the tested fine- and coarse-grained granites were considered from the viewpoint of the hierarchical structure of rocks.

In this paper, we obtained intensity distributions of beams of positively charged ions emitted from the surface of uniaxially compressed granites under the effect of a shock wave. The intensity of beams decreases exponentially with an increase in the number of shock waves. The ions fly out at the moments when the dislocations reach the surface moving in intersecting slip planes. A compressive load suppresses the dislocation release and the intensity of ion beams.

Light-emitting organic field-effect transistors (LE-FETs) on the basis of composite films that consist of perovskite nanocrystals (CsPbBr3) embedded in a matrix of conjugated polymer—polyfluorene (PFO)—have been obtained, and their electrical and optical properties have been investigated. Output and transfer current-voltage characteristics (I-Vs) of FETs based on PFO : CsPbBr3 films (component ratio 1 : 1) have a slight hysteresis at temperatures of 100–300 K and are characteristic of hole transport. The hole mobility is ∼3.3 and ∼1.9 cm2/(V s) at the modes of the saturation and low fields, respectively, at 250 K and reaches ∼5 cm2/(V s) at 100 K. It has been shown that the application of pulsed voltage to LE-FETs based on PFO : CsPbBr3 can reduce the ionic conductivity and provide electroluminescence in this structure at 300 K.

The electrical properties of the films of organometallic perovskites CH3NH3PbBr3 and CH3NH3PbI3 were studied. Current–voltage characteristics for the CH3NH3PbBr3 and CH3NH3PbI3 samples were measured in a temperature range of 300–80 K, from which the temperature dependences of resistivity ρ(T) having characteristic points of inflection in a range of 160–240 K were determined. The activation energies of charge carriers prior to and after points of inflection were determined. It is assumed that the observed features in the temperature dependences of resistivity (temperature at the points of inflection) correlate with the temperatures of tetragonal-to-orthorhombic phase transitions for two studied organometallic perovskites (CH3NH3PbBr3 and CH3NH3PbI3).

Solution-processed hybrid perovskite materials are attracting considerable attention as active layers of solar cells and hybrid light-emitting diodes (LEDs). Introducing perovskite CsPbBr3 nanocrystals (NCs) into light-emitting polymer (MEH-PPV) matrix can improve the processability and stability of such hybrid LEDs. In this work we investigate experimentally and consider theoretically the nonradiative excitation energy transfer from perovskite CsPbBr3 NCs to organic conjugated polymer MEH-PPV matrix along with experimental investigation of optical properties of such MEH-PPV:CsPbBr3 hybrid thin film structures. The theoretical analysis is carried out based on the Forster theory. The relative photoluminescence (PL) intensity of the MEH-PPV matrix is calculated as a function of the embed CsPbBr3 NC concentration. The decrease of the PL intensity with the increase of the CsPbBr3 NC concentration is found both theoretically and experimentally. It was found that the PL decay obtained experimentally is stronger with respect to that found theoretically. The reasons for the quantitative distinctions between the experimental data and as a result of the theoretical consideration are discussed.

IR windows made of ZnS ceramics serve as protective elements for the thermal imaging systems established on mobile carriers, whereon they suffer from weathering and dust impacts. In this study, the erosion of ZnS ceramics was simulated by the abrasive damaging of polished specimens, and the response of the crystal lattice on the external forcing was investigated by the method of photoluminescence (PL). Impacts of isolated hard particles were modelled with the discrete shocks of a pointed striker, and fractoluminescence (FL) from the damaged spot was detected. The FL evidenced that the impact forcing triggers a two-stage mechanism of damage nucleation in this ductile ceramic. The dislocation motion at the stage of initial deformation followed by the interatomic bonds breakage at the stage of cracking. The PL data showed the higher stability of crystallites in chemically vapor-deposited (CVD) ZnS ceramics as compared with the same compounds obtained by the hot pressing (HP) or physical vapor-deposition (PVD) technologies. The abrasive treatment of ZnS-CVD did not affect significantly the entirety of crystallites because of plasticity of intercrystallite substance, in which the impact-induced tension dissipated. Undamaged crystallites retained their optical properties that is did not exhibit additional absorbance. Thus, the decrease of the transmissive capability under particle impacts occurs predominantly due to light scattering on the newly-formed surface irregularities.

Chemically inert 40 keV Ar+ ions were implanted into fused SiO2 with doses in the range of 1×1014 to 1×1016 ion/cm2. The implanted specimens were subjected to the localized impact damaging by a pointed striker. The acoustic emission method was applied to assess the dependence of the microcracking process on the implantation dose. The fractoluminescence method showed the generation of non-bridged oxygen hole centers (NBOHC) [ Si–O–] in newly formed microcracks. The performed experiments revealed a critical fluence, which affected in a non-linear manner the fractoluminescent activity due to changes in the mechanical properties of the Ar+-treated surface layer. An interplay between random and correlated damage accumulation at various structural levels was demonstrated.

The conventional tubing supplied to oilfields with low aggressive environments: with pCO2 up to 0.3 atm and pH2S up to 0.005 atm often shows signs of pitting carbon dioxide corrosion after operation. To solve the problem, a new sparingly alloyed steel of 25KhGB was developed for K steel grade tubing with increased set of performance characteristics obtained after thermomechanical treatment.

We have investigated the photoluminescence (PL) and photoconductivity of lead halide perovskite (CH3NH3PbBr3) films modified with different mixed cellulose esters (CEs). It was shown that the absorbance and PL spectra of CH3NH3PbBr3 : CE films contain contributions of both the CH3NH3PbBr3 and CE with the dominant contribution to the PL from perovskite component. The dependences of the integral PL intensities of the CH3NH3PbBr3 : CE films on the optical excitation power turned out to be sublinear. This indicates that exciton recombination, as well as recombination via impurity levels, occur in CH3NH3PbBr3 : CE films at high excitation power levels. The conductivity of CH3NH3PbBr3 : CE films at 300 K increases up to ~90 times when illuminated by a solar simulator, and this effect is environmentally stable due to the formation of hydrogen bonds between CE and the lead halide perovskite CH3NH3PbBr3. It is expected that appropriate selection of CE and optimization of CE inclusion will improve the optoelectronic properties and stability of composite films based on lead halide perovskite-CE composites.

The effects of resistive switching were investigated in composite films based on multifunctional nonconjugated polymers such as poly(9-vinylcarbazole)—PVK mixed with particles of graphene (Gr) and graphene oxide (GO). The concentration of Gr and GO particles in the PVK matrix was varied in the range of 1–3 wt%, which is close to the percolation threshold in these systems. It was found that the effect of switching in structures of the form Al/PVK:Gr(GO)/ITO/PET manifests itself in a sharp change of the electrical resistance of the composite film from a low-conducting state to a relatively high-conducting state when applying a bias to Al–ITO electrodes of ∼0.2–0.4 V, which is below the threshold switching voltages for similar composites. The cyclic voltammetric measurements of PVK:Gr(GO) films were carried out. It was found that the potential of redox transition of Gr/GO belongs to the interval of redox-switching voltage of PVK:Gr(GO)/ITO/PET composite films with effect of the resistive switching. The possible mechanism of the resistive switching, which is associated with the redox processes as well as with processes of capture and accumulation of charge carriers by Gr (GO) particles introduced into the matrices of the PVK polymer due to reduction/oxidation processes is discussed.

Samples of SiC ceramics differing in porosity in the range 1–9 % were damaged by a falling weight, and the acoustic emission (AE) and fractoluminescence (FL) activity lasting up to 1.3 μs was detected. The recorded time series of AE and FL pulses were used for constructing the energy release distributions in individual damage events occurring at the microscopic and nanostructural scale levels, respectively. A critical pore concentration was found, at the transition over which the random energy release in primary defect nucleation changes for the scaling one at the nanostructural level. These changes in the mechanical behavior were explained by the growth of the area of the oxidized film on the pore surface in more porous sintered samples. At the microstructural scale level, any qualitative changes in the scaling mechanical behavior of ceramics were not observed.

The acoustic emission (AE) and fractoluminescence (FL) techniques were applied to study the impact damage in sintered powders of SiO2, SiC and Al2O3 and their single crystal counterparts. The measured AE intensities and FL amplitudes are proportional to the energy release in events of microcrack nucleation and chemical bond breakage, respectively. In crystals, the AE method showed the random energy release in crystals, and the scaling energy distributions in powders. The FL method evidenced the self-similar energy distributions in α-SiO2 and α-SiC due to nanostructural heterogeneity inherent even to homogeneous solids, while luminescence from α-Al2O3 was specific for the random process.

The optical and electrical properties of films and field-effect transistors (FETs) based on pure MEH-PPV, neat CsPbBr3 nanocrystals (NCs), and MEH-PPV:CsPbBr3 NCs composites with different contents of CsPbBr3 NCs are investigated. The films were characterized by absorbance, atomic-force microscope and current-voltage characteristics (I-Vs) techniques. Relative PL and EL intensities and PL spectra of the pure MEH-PPV, neat CsPbBr3 NCs and MEH-PPV:CsPbBr3 NCs films were measured at 300 K at various levels of optical and electrical excitation power; these dependencies of the PL and EL intensities turned out to be sublinear and superlinear respectively. FETs based on MEH-PPV:CsPbBr3 NCs (1:1) films exhibit I-Vs at 290 – 100 K a dominant hole transport mechanism. The mobility of charge carriers was determined at 290 K for neat CsPbBr3 NCs (for electrons: 2.7 10−2 cm2/Vs) and MEH-PPV:CsPbBr3 NCs (1:1) (for holes: 9 cm2/Vs). The temperature dependence of the hole mobility μFET(T) of FETs based on MEH-PPV:CsPbBr3 NCs (1:1) films characteristic of the hopping mode. It was found that the superlinearity of the dependence of EL of MEH-PPV:CsPbBr3 NCs LE-FETs at 290 K increases with increasing concentration of CsPbBr3 NCs due to efficient energy transfer between CsPbBr3 NCs and the MEH-PPV polymer matrix, and also because of the probability of electron tunneling through the potential barrier to electrode. It is expected that the obtained MEH-PPV:CsPbBr3 NCs nanocomposite films will be useful for efficient applications in nanotechnology LEDs, FETs and LE-FETs.

The results of modeling a composite nickel-phosphorus coating obtained by chemical deposition are presented. The state of structural-phase disordering of the coating surface is considered. The analysis of possible structural states in the surface layers of the coating is carried out. A graph of Me atoms volume changes in phosphorus-containing compounds MexPy(Ме – Fe, Cr, Ni) and the maximum stability temperature NixPyis plotted depending on the composition. The idealized images of the projections of tetragonal and trigonal phosphorus-containing phases structures are constructed.

The acoustic emission (AE) technique was applied for monitoring the high-speed cracking process in three kinds of impact-damaged granites at temperatures 20 °C to 600 °C. The analysis of the amplitude-frequency response of the AE time series showed the presence of a few populations of cracks differing in size in the range 0.25 mm to 2.3 mm. The dependence of the appearance/growth/decay of any given population on temperature and physical and mechanical properties of granites evidenced the interplay between inter- and intragranular cracking under various thermal conditions. At room temperature (pure mechanical forcing), the intergranular damages along boundaries between the same minerals prevail; at 200 °C (impact forcing plus thermoelastic stress), the cracking between grains of quartz and feldspar emerge; finally, in the range 500 °C to 600 °C, the intragranular damages appear.

We report on a solution processed hybrid organic field-effect transistors (OFETs) incorporating both organic semiconductor – poly(9-vinylcarbazole) (PVK) and graphene oxide (GO) flakes. We have found that PVK:GO hybrid OFETs with Au–Al source–drain electrodes exhibit the mobility as high as 3.8–6.7 cm 2 V −1 s −1 under concentration of the GO flakes varies from 3 up to 9.5 wt.% respectively. The on/off ratio of PVK:GO hybrid OFETs is found to be ∼10 2 –10 3 at source–drain and gate operating voltages below ∼5 V. The reversible switching of the source–drain current (from low to high I SD and back) is found at positive and negative V SD ∼ 12–13 V in the PVK:GO OFET structures (GO ∼ 3 wt.%) with Au–Al source–drain electrodes. The possible mechanism of enhancing field-effect mobility in the PVK:GO OFET structures is discussed.

Composite films based on bacterial cellulose (BC) modified with conductive polymer PEDOT/PSS are synthesized. Structural, optical and electrical properties of such composite films are investigated. It was found that the obtained BC:PEDOT/PSS films characterized by strong absorption in the red and near-infrared spectral region and by weak intensity of photoluminescence at 300 K. The temperature dependence of the resistivity of the BC:PEDOT/PSS films follows a power law in the temperature interval 300–80 K and the resistivity values vary weakly with time. The charge carrier transport in the BC:PEDOT/PSS composite films governed mainly by the charge transport in the conducting polymer. The obtained BC:PEDOT/PSS films are promising for application as biocompatible electrodes, temperature sensors and other biochips, which are compatible with technology of printable organic electronics.

Ductile semiconductor ceramics ZnSe and ZnS were damaged by a falling weight, and the time series of mechanoluminescence (ML) and acoustic emission (AE) pulses were recorded with the nanosecond resolution. The ML lighting appeared in the instance of shock but the AE generation emerged with a delay of 50-100 μsec; however, the maxima of the light and sound emissions coincided in time. This difference in temporal profiles was explained by the difference in prevailing sources of emissions of two types. The detected luminescence in A2 B6 compounds was excited, mainly, by moving and multiplying dislocations, while the sound was generated by nucleating and growing cracks. The statistical analysis showed that at the stage of pre-failure deformation, the ensemble of dislocations exhibited a trend to self-organizing; the cracking was fully random. The effect of intergranular boundaries on the dislocation motion manifested itself in the statistics of mechanoluminescence generation.

We demonstrated flexible light-emitting transparent bacterial cellulose (BC) paper modified with semiconducting polymer operated by pulse voltage. We prepared thin (~ 35 μm) transparent BC films modified with luminescent conjugated polymer MEH:PPV with Ag electrodes. It was shown that the photoluminescence (PL) spectrum of BC/MEH:PPV films contains emission contributions from both BC and MEH:PPV components and that the PL intensity of BC and MEH:PPV maxima versus excitation power is sublinear. This indicates that exciton–exciton annihilation occurs in the light-emitting polymer at high excitation power. We found that the dependences of the spike-like electroluminescence (EL) intensity of BC/MEH:PPV films excited by the pulse voltage at different frequencies versus applied pulse bias and pulse frequency are superlinear. We assume that the turn-on and turn-off spikes originate from the recombination of charges accumulated in the bulk of the semiconducting polymer (bulk de-trapping) during the voltage pulse. The results demonstrate that such composites are prospective for application as flexible, transparent and environmentally friendly light-emitting cellulose-based papers for displays and lighting as well as biosensors.

We report on the effect of electric field on the photoluminescence, PL, from a composite consisting of a conjugated polymer mixed with zinc oxide nanoparticles. We have found that in the absence of electric field PL emission from the composite film has two maxima in the blue and green-yellow regions. Application of a voltage bias to planar gold electrodes suppresses the green-yellow emission and shifts the only PL emission maximum towards the blue region. Current-voltage characteristics of the polymer-nanoparticles composite exhibit the non-linear behavior typical of non-homogeneous polymer-inorganic structures. Generation of excited states in the composite structure implies the presence of several radiative recombination mechanisms including formation of polymer-nanoparticle complexes including exciplex states and charge transfer between the polymer and nanoparticle that can be controlled by an electric field., Comment: 5 pages, 5 figures. accepted for publication in Solid State Communications

We report on a light-emitting organic field-effect transistor (LE-OFET) based on a polyfluorene (PFO)–ZnO nanoparticles film. We have analysed the behaviour of absorption, photoluminescence spectra and electroluminescence (EL) intensity of the PFO : ZnO hybrid films with different ZnO concentrations prepared in the FET configuration. We have found that the PFO : ZnO LE-OFET exhibits the current–voltage characteristics of a unipolar FET with saturation behaviour and operates in the hole accumulation mode. The FET mobility values in the PFO : ZnO films with a high ZnO concentration are close to the mobility of polycrystalline ZnO. A significant increase in the EL intensity of the hybrid films has been observed with an increase in the concentration of ZnO nanoparticles and with the application of gate voltages. The working mechanism of the LE-OFET device is discussed.

We report on the investigation of the electrical and optical properties of hybrid active layers for organic devices consisting of a conjugated polymer MEH-PPV mixed with ZnO and Si nanoparticles. The effect of an electric field on the photoluminescence (PL) from a MEH-PPV : ZnO composite film is studied. We have found that in the absence of an electric field PL emission from the MEH-PPV : ZnO composites have two main maxima in the blue–red regions. Three additional minor PL maxima attributed to the exciplex states were found at ~420–480 nm. Application of a voltage bias to planar electrodes significantly suppresses the blue emission. Generation of excited states in the MEH-PPV : ZnO structures implies the presence of several radiative recombination mechanisms with the formation of polymer–nanoparticle complexes including exciplex states and charge transfer between the polymer and nanoparticles that can be controlled by an electric field. This effect provides the possibility to tune by an electric field the emission colour of organic light emitting diodes by combining an efficient emission from both organic/inorganic materials involved.