Search

A turbidimetric photometer with a pulsed mode of operation of a light source is analyzed. The device makes it possible to conduct sedimentation studies of nanoscale object in terms of laboratory background illumination with a study duration of more than 500 hours. The functional diagram of the laboratory device sample is described and experimental surveys of some characteristics are presented.

A method using a vapor phase approach to formation of a polymer shell on the surfaces of submicron particles (SP) has been investigated. The method is based on the condensation of monomer vapors and their subsequent polymerization on surfaces of charged and dispersed SP. This method makes it possible to vary the thickness of the polymer shell from a few to hundreds of nanometers. This is achieved by choosing the ratio of the flow rates of SP and monomer in two miscible two-phase flows. It is shown that the polymer shell possesses good adhesion to the surfaces of the SP. Apparently, this will make it possible to introduce encapsulated particles, while maintaining the polymer shell, into the polymer matrix of thermoplastics at their softening temperature.

Temperatures have been identified in the corona hood and streamer of a plasma-chemical reactor during the formation of a polymer film with carbon nanosized particles. A semiempirical procedure has been proposed to estimate these temperatures. It has been shown that in the case where the temperature in the streamer volume is ~600°C and it is ~1400°C in the corona hood, polycrystalline carbon nanoparticles are formed in the plasma-chemical reactor whose agglomerates penetrate into the polymer film.

The results of studies into the influence of the thickness of a polystyrene shell applied to surfaces of dispersed corundum (Al2O3) filler particles on the structure and mechanical properties of the composition of an acrylonitrile butadiene styrene plastic are presented. It is shown that the mechanical properties of the composition depend at least on two factors: the interaction between shell molecules and the polymer matrix, and the ratio of shell thickness to the average size of submicron particles of the filler. The change in the mechanical properties of the composition is explained by the decreasing mobility of polymer macromolecules near the encapsulated filler particles due to the increasing adhesion of macromolecules to the polymer shell. It was shown experimentally that the Martens hardness, elastic modulus, tensile strength, and rupture strain can be changed in some range by varying the thickness of the polymer shell on the surfaces of corundum particles.

MCM-41 type mesoporous silica particles were obtained using a template method in an alkaline medium and cetyltrimethylammonium bromide as a matrix. The structural and adsorption characteristics of the mesoporous material were studied by dynamic light scattering, scanning electron microscopy, low-temperature adsorption—desorption of nitrogen, IR spectroscopy, and simultaneous thermal analysis. It was shown that the obtained mesoporous material possesses high porosity with the specific pore volume in excess of 1 cm3 g−1. It was established that the size of silica particles does not exceed 200 nm, which is a value acceptable for the penetration of drugs through cell membranes. The optimal compositions of aqueous dispersions of MCM-41 with minimal sedimentation processes were determined. A drug (indomethacin) was encapsulated into the silica pores using the precipitation method at various temperatures (40 and 60 °C), the quantitative parameters of loading efficiency were calculated. The infl uence of temperature on the encapsulation ability was demonstrated.

A technique for measuring the internal stresses in polymer films deposited on a glass substrate in gas discharge plasma is developed. Using this technique, the dependence of internal stress in thin films of polymethylmethacrylate and polystyrene on the deposition time and the current density of the barrier discharge at atmospheric pressure is studied. It is found that, when forming thin polymer coatings from monomers with high polymerization efficiency, the average value of internal stresses is higher than that for coatings obtained from monomers having low polymerization efficiency in barrier discharge plasma at atmospheric pressure. This can be explained by an increase in the specific number of cross-links in the first type of films under the action of ultraviolet radiation from the plasma. The quasi-optimal deposition time of the polymer film coating from styrene is found in which the value of the internal stress is minimal at a film thickness acceptable for a number of practical applications.

The study of a method for controlling the structural integrity of monolithic polycarbonate under cyclic loads is presented in the article. In particular, the influence of external cyclic loads on crack formation in polycarbonate was determined. The carried out experimental studies have shown the structural changes in polycarbonate (the appearance of microdefects) can be detected by a decrease in the level of the piezoelectric voltage amplitude U compared to the initial level by ∼25% for more than 104 load cycles.

В работе предлагается математическая модель динамического измерения концентрации полимерной оболочки на поверхности дисперсных частиц их наполнителя, взвешенных в жидкости в процессе их седиментации. Математическая модель предусматривает движение осаждаемых частиц под действием силы тяжести, гидростатической подъемной силы, силы сопротивления движении. В модели учитывается влияние броуновского (теплового) движения растворителя на перемещение частиц на основе упругого столкновения, влияние неупругого столкновения частиц друг с другом. Кроме того, учитывается влияние движения жидкости под действием градиента температуры на движение осаждаемых частиц, для чего построена математическая модель движения жидкости. Оценка концентрации частиц осуществляется на основе моделирования рассеяния Рэлея. Проведено сравнение данных расчетов с результатами натурного эксперимента.

Novel nanocomposite system based on mesoporous silica nanoparticles (MSNs) noncovalently modified with hexadecyltriphenylphosphonium bromide (HTPPB) has been prepared, thoroughly characterized and used for encapsulation of model cargo Rhodamine B (RhB). The high encapsulation efficacy of this dye by HTPPB-modified mesoporous particles was demonstrated by spectrophotometry and thermography techniques. The bioavailability of MSN@HTPPB was testified. Cytotoxicity assay revealed that a marked suppression of M−HeLa cancer cells (epithelioid carcinoma of the cervix) occurs at concentration of 0.06 μg/mL, while the higher viability of Chang liver normal cell line was preserved in the concentration range of 0.98–0.06 μg/mL. Hemolysis assay demonstrated that only 2% of red blood cells are destructed at ~ 30 μg/mL concentration. This allows us to select the most harmless compositions based on MSN@HTPPB with minimal side effects toward normal cells and recommend them for the development of antitumor formulations. Fluorescence microscopy technique testified satisfactory penetration of HTPPB-modified carriers into M−HeLa cells. Importantly, modification of the MSN with HTPPB is shown to promote efficient delivery to mitochondria. To the best of our knowledge, it is one of the first successful examples of noncovalent surface modification of the MSNs with lipophilic phosphonium cation that improves targeted delivery of loads to mitochondria.

—We study the formation mechanism of carbon nanoparticles with simultaneous formation of a polystyrene film in a AC barrier corona discharge at atmospheric pressure. The importance of the research stems from the need to control the allotropic form of carbon nanoparticles, which affects the physical and technical characteristics of polymer films obtained by this method. It is shown that nucleation of polycrystalline onion-like carbon nanoparticle agglomerates is the basis for graphene flake formation in the corona sheath. Graphene flakes form from these nucleation sites in gas discharge streamers owing to the destruction of monomer molecules remaining in the agglomerates of nucleation sites. It was revealed that the allotropic form of such particles is determined not only by the energy—in this case the barrier corona discharge—but also by the ratio of the duration of its exposure to the characteristic destruction and formation times of covalent bonds participating in the particle process.

The structure and mechanical properties of a composition on the basic of polycarbonate filled with three types of dispersed particles (submicron corundum, micron boron nitride, and glass fiber ones) were investigated. It is shown that the method of sample preparation proposed ensures a uniform distribution of filler particles in them. Slight changes in the supramolecular structure of polycarbonate were seen only in the case of introduction of submicron corundum particles. No such changes occurred in the case of micron boron nitride or glass fiber particles in amounts providing an optical transparency no less than 70%, which can be explained by insufficient interaction forces between filler particles and polycarbonate molecules. It is shown that filling polycarbonate with various fillers allowing the retention of its optical transparency does not make it possible to increase its wear resistance and softening temperature. The weight parts of dispersed filler at which the transparency does not decrease below 70 % are ~0.06, ~0.03, and ~1.0% for corundum, boron nitride, and glass fiber particles, respectively.

The results of experimental studies of anti-acing property of passive organosilicon coatings with hydrophobic groups are presented. The high efficiency of that coating with hydrophobic groups -CF3 is found. It is shown that such coatings can provide low icing intensity and, at the same time, high abrasion resistance.

The results of the polymer film investigation are considered in that paper. These films are obtained in atmospheric pressure barrier discharge from aniline with simultaneous generation of carbon particles in the films. It is demonstrated that the structure of these films corresponds to one of the amorphous polymers. Carbon particles produce agglomerates with a concentration that slightly depends on the discharge energy density. The authors show that the conductivity of aniline films with carbon particles mainly depends on water saturation.

The influence of the nature of stabilizing amphiphilic additives on the dispersion and precipitation of carbon nanoparticles was evaluated. The stabilized systems were tested for adsorption properties with respect to spectral probes and drugs for which purpose the degree of removal and the amount adsorbed were determined spectrophotometrically for dye Orange OT and anti-inflammatory drug indomethacin.

The physical mechanism underlying the effect of generation of Auger duplexes as a consequence of the electronic level transformation in the case of local energetic effect in the atoms of complex oxides is suggested. It has been established that the effect of the formation of Auger duplexes is independent of the type of radiation acting on an object and is determined by the energy of the affecting particles and by the time of irradiation leading to accumulation of the reactions induced by electrons (ions).

The formation mechanism of argon clathrates with carbon dendrites obtained in the plasma of an atmospheric-pressure gas discharge has been studied. It has been shown that the formation of these clathrates is due to the difference between characteristic times: the lifetime of molecules surrounding argon atoms and the time of C–C bonding. It has been noted that argon clathrates with carbon dendrites can form only if a number of conditions are met: formation of molecular traps in the discharge, provision of a sufficiently low temperature at the center of the arc discharge, and the presence of active carbon particles arising from plasma decomposition of hydrocarbon precursors. Whether or not these conditions are met depends primarily on the composition of the initial hydrocarbon mixture and discharge current density, as follows from experimental data.

The technique of deposition of polymer films from the barrier gas discharge plasma on top of dielectric substrates is developed. The film precursor is a monomer material highly dispersed in a transport plasma gas. The plasma formation of the continuous polymer film can be divided into two stages. The first stage is deposition of liquid monomer droplets with subsequent polymerization on the dielectric barrier surface resulting in growth of a discontinuous film. It is found that the ratio of the height of droplets to their lateral size is almost constant and for polystyrene it is equal to ~0.01. The second stage is expansion of the droplets into islands and their coalescence into a continuous polymer film on the dielectric barrier surface. The polymer coating thickness and the amount of cross bonds essentially depend on the current density and concentration of the monomer in the transport discharge gas. A continuous polymer film, which is not contaminated with the monomer destruction products, can be obtained in the current density range of 7–25 mA/cm2. Experiments with several monomers, like methylmethacrylate, styrene and acrylonitrile, have shown that the growth rate is maximal for monomers with oxygen-free molecules. At the same time, a higher growth rate provides low cross-bond coatings, whereas to get high density of the cross-linked bonds one has to utilize low deposition rates. The minimal thickness at which continuity of the film is achieved increases when the monomer concentration in the plasma rises. In general, the coating thickness depends linearly on the discharge current density; the particular figures depend on the type and concentration of the monomer. The technological parameters are established and given for the three aforementioned monomers.

The autogenerating method of polycarbonate piezoelectric voltage measurement is considered in the article, and the schematic diagram models of autogenerators are given. By use of simulation was determined that the most appropriate frequency range of autogenerators according to the Klapp scheme is 4÷9 MHz with subsequent separation of their beat signal. The carried out experimental studies have confirmed the adequacy of the modeling and have shown that frequency stability of ∼ 10−2 is sufficient to control the ultimate strength of monolithic polycarbonate glasses.

The structure and mechanical properties of composites based on an ED-20 epoxy resin, modified with ZnO and ZnO particles untreated or encapsulated in polystyrene, were studied. It is shown that the introduction of polystyrene-encapsulated ZnO submicroparticles into the epoxy resin changed its supramolecular structure in comparison with that of the resin filled with untreated ones. It was established that the presence of shell on the filler particles affected the mechanical properties of the polymer composites — their hardness increased by 22.5% and elastic modulus by 13%.

The influence of growth conditions on the carbon dendrite structure has been investigated. The threshold values of the ratio between electron temperature Te and kinetic temperature T of the gas near a needle electrode and of the discharge current density, which are necessary for dendritic growth, have been determined. It has been shown that the hexagonal structure of submicron carbon particles arises when a number of hydrocarbons are used to synthesize dendrites. It has been found that the degree of order in the carbon structure can be controlled by applying external actions at the stage of graphite particle nucleation. The characteristic frequencies of inertial actions that may be energetically appropriate must exceed 10 kHz.

Results of theoretical and experimental investigations of the efficiency of an integral electrothermal anti-ice system based on fluoroplastic films are presented. It is shown that the use of this system makes it possible to decrease the energy expended for the de-icing by 30% as compared to the existing electrothermal anti-ice systems and that an integral electrothermal anti-ice system can be used in small and midget aircrafts including unmanned ones.

The experimental results of relationship between tensile strength and piezoelectric voltage in transparent monolithic polycarbonate are presented in that paper. The most useful location of electrodes on the surface of monolithic polycarbonate samples for measurement the piezoelectric voltage was determined. It was showing that the first derivative of piezoelectric voltage by time passes through the zero when the cracks in polycarbonate start arising. Moreover, the local maximums of the piezoelectric voltage and a tensile strength come a little bit earlier than the cracks in polycarbonate start arising. That allows using piezoelectric effect to diagnostics the maximum allowable strength in transparent monolithic polycarbonate.

The studies of the peculiarities of inertial effects (IE) application for stabilization of multimode nonlinear systems and complex structures are considered in that paper. It is showing that stabilizing effects in the field of influence of inertial properties of nonlinear systems do not require strict restrictions on their phasing and open up new possibilities of control and stabilization of multimode nonlinear systems and complex structures.

In the work we give the results of an experiment during which carbon dendrite structures were formed in the plasma of an atmospheric-pressure gas discharge by using depolymerization products of polymer materials.

The diagnostics method for multimode nonlinear radiophysical systems with chaotic dynamics based on the multimode models is offered. It is shown that quasi-resonance and inertial controlling influence on the system's parameters can ensure the dominance of necessary chaotic or regular behavior mode of multimode nonlinear radio physics systems. A new approach in diagnostics of gas discharge plasma condition on the bases of generalized multimode model was offered. This diagnostic was made on the bases of analyses of absolute and dissipative terms of generalized oscillators of multimode model which taking into account the nonlinearity of gas discharge plasma.

This article presents the results of experimental studies of polymer shell formation on the surface of submicron (including nano-) particles due to mixing of a pair of two-phase gas flows of submicron particles and fine-dispersed liquid monomer droplets. The possibility of changing the polymer shell thickness on the surface of submicron particles by controlling the ratio of charges and particle sizes due to variations of electrical field strength in discharge cameras for charging and the dispersion of submicron particles and fine-dispersed liquid monomer droplets is shown.

This work presents the results of experimental tests of a synthesis method of multilayer polymer films with given physicochemical properties of individual layers and determination of the type of bonds between binder-layer molecules and surface molecules of glued polymer films. Thus, for initiation of the reaction of radical surface graft polymerization, the corona discharge was used.

Conditions in which fractal carbon structures are formed in barrier-discharge plasma under atmospheric pressure to obtain submicrometer carbon particles have been studied.

The Bragg microwave structures on the coaxial waveguide, constructed on the basis of the transfer optical technologies similar to the Bragg fiber grating, are considered. It is offered to use versions of such coaxial Bragg microwave structures in sensor application, in particular, creation of strain gauges, instruments for measuring dielectric constant of liquids and liquid products' level is considered. Methods for description of periodic inhomogeneous microwave structures characteristics and ways to modify the form of the frequency dependence of scattering parameters are viewed.

The implementation of non-absorbent polymers thermal destruction initiated by indirect heating in an intense electromagnetic microwave field using carbon thermal conversion elements is considered. Results of theoretical analysis based on mathematical modeling and experimental investigation into depolymerization of the polymer are analyzed. Polystyrene and polymethylmethacrylate are the investigated polymers; their destruction products are styrene and methyl methacrylate.

The technology of fiber Bragg gratings is used as one of the most applicable technologies for construction of fiber optic sensors and telecommunication systems. Periodic irregular wave resistance located in the guiding waveguide can be regarded as analog of the fiber Bragg grating structure in the field of radio-frequency. Coaxial waveguide can be used as a guide system, so a special case of this structure is the Bragg grating on coaxial cable. Recently, the special structure of sensors were beginning to be used with heterogeneity as a discrete phase π-shift. Based on the properties analysis of the Bragg reflection characteristics of structures with a phase shift in the optical and microwave range shown advantage of using these devices in measuring systems.

Parameters of external inertial actions capable of stabilizing a fractal oscillator so as to ensure a required regime (mode) of its dynamic behavior are determined. It is shown that the restoring force in the nonlinear fractal oscillator under consideration depends on the square amplitude of the external harmonic action and on an alternating-sign factor.