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We study the aggregation of carbon allotrope nanofillers in the matrix of isotactic polypropylene with direct small-angle neutron scattering measurements. With the ATSAS software, we analyzed the d...

Appearance of the rheological explosion in PE pellets with different molecular weights is investigated. The duration of the first and second stages of the rheological explosion is almost independent of MW. The moment of irreversible destruction of the sample and the value of rheological explosion threshold linearly decrease with an increase in the length of the polymer chain. As a result of the explosion, the heat of melting of polymers with MW values equal to 3 × 105 and 1 × 106 decreases, while for PE with M = 3.5 × 104 the heat of melting remains almost unchanged. Electric current pulses are recorded. Their Fourier images are in the form of band spectra described by the Lorentz models for a damped harmonic oscillator and the Havriliak–Negami model for dielectric relaxation. Experimental data suggest that the rheological explosion is associated with the accumulation of elastic energy in the amorphous phase of PE and, during the rheological explosion, polymer chains are broken to generate radicals •RO2.

Low-temperature nitrogen adsorption, X-ray phase analysis (XRD), and electron microscopy are used to analyze the physicochemical properties (morphology, texture, phase composition, specific surface area, and porosity) of ASD-4 ultrafine powder and the products of the reaction between ASD-4 nanopowder and Mn, Fe, Co, and Ni formates. Results from studying the morphology and phase composition of oxidation products are presented, and the specific surfaces and porosities of the powders are calculated. Features of the adsorption isotherms of the studied samples after modifying them with formates are discussed in terms of their conformity to a specific type, according to the recommendations of the International Union of Pure and Applied Chemistry (IUPAC), and to certain types of porosity. The data show that the ASD-4 + 2% Mn and ASD-4 + 2% Ni samples are the ones with the highest adsorption activity. The specific surface area is 19.7907 m2/g for ASD-4 + 2% Mn and 10.1244 m2/g for ASD-4 + 2% Ni. The ASD-4 + 2% Mn and ASD‑4 + 2% Ni samples have more pores of mixed shape (slit-like and cylindrical) with widths of around 48.7234 and 44.2675 A, respectively. The pore volumes are 0.028250 and 0.012156 cm3/g for the ASD-4 + 2% Mn and ASD-4 + 2% Ni, respectively.

The surface structure and volume of a 3D article produced by the method of selective laser melting from a powder of the D-16 alloy has been studied. Using the XPS method, it has been determined that there is an Al2O3 layer on its surface and a metal alloy Al–Cu with a copper content of ~5% under it, which coincides with the data of energy dispersive X-ray analysis conducted on the initial powder by the method of scanning electron microscopy. Local areas with an increased copper content (up to 13 at %) were revealed at the boundaries of the crystal grains. A high porosity of the obtained material has been established, which resulted from the specifics of crystallization of the Al–Cu system’s alloys related to the transfer of substance along the interfaces, as a consequence of the presence of concentration, temperature and, surface tension gradients along with nonoptimal 3D printing conditions.

The effect of induced mechanical activation of radio-frequency superradiance in a parametric mode under the action of an external rheological explosion at high pressure on a paramagnetic composite—a system of crossed spins based on binuclear complexes Co (QH)2–O–Co(QH)2 or Mn(QH)2–O–Mn(QH)2 (QH is a ligand based on 3,6-di-tert-butylpyrocatechol) in a polystyrene matrix—is found. Possible methods for processing data on the pulsed mechanical effect and a possible scheme of the initiation of the effect are proposed.

Based on the concept of collective vibrations of ions in the bulk of metal systems, the frequency of vibrations of an oxygen molecule on the aluminum–cerium alloy surface has been evaluated. Numerical estimation of the physical adsorption isobar has been carried out in accordance with the Henry law using these data and the heats of oxygen adsorption on the surface of this alloy in amorphous and polycrystalline states obtained on the basis of optical experiment data. It has been shown that changes in the alloy’s electronic structure upon splitting of the conduction band for the amorphous state has a significant effect on the qualitative characteristics of the adsorption process.

The frequency dependences of electrical conductivity with both real and imaginary components of a dielectric permittivity of polydimethylsiloxane oil suspensions filled by halloysite nanotubes having different amount of water are studied by dielectric spectroscopy. An analysis of frequency dependences of dielectric loss on temperature made it possible to assess the energy of activation of relaxation processes proceeded in suspensions. An effect of a low amount of water on the relaxation processes is considered.

This paper presents carbon nanotubes-containing polymer composites with layered gradient structure having electromagnetic interference (EMI) shielding properties. Polymer composite films we...

The electron structures of pure and oxidized aluminum surfaces at ambient temperature have been studied while analyzing the results of a simulation of optical conductance on the basis of optical experiments. It is established that oxidation of an aluminum surface in the solid state leads to splitting of the conduction band when it contains forbidden state regions. The heat of oxygen adsorption on aluminum stated has been determined on the basis of properties of surface states.

The effect of small additives of manganese, iron, cobalt, and nickel oxides on the oxidation of aluminum powder of ASD-4 grade while heating in air is studied. Composites of Al/MOx were prepared by impregnating the metal powder with saturated solutions of M(HCOO)2 ⋅ 2H2O (M = Mn, Fe, Co, and Ni) formates and thermal treatment of the mixtures in air with a maximum annealing temperature of 375°C. It has been established that the effect of modifiers on the intensity of oxidation depends on the nature of the interfacial interaction on the surface of particles. The formation of a liquid phase in the interaction of aluminum oxides and iron leads to the loss of the protective properties by the barrier layer of oxidation products and acceleration of the process.

Dielectric properties of two series of magnetoactive elastomers (MAEs) based on a soft silicone matrix containing 35 vol% of magnetic particles were studied experimentally in a wide temperature range. In the first series, a hybrid filler representing a mixture of magnetically hard NdFeB particles of irregular shape and an average size of 50 μm and magnetically soft carbonyl iron (CI) of 4.5 μm in diameter was used for MAE fabrication. MAEs of the second series contained only NdFeB particles. The presence of magnetically hard NdFeB filler made it possible to passively control MAE dielectric response by magnetizing the samples. It was shown that although the hopping mechanism of MAEs conductivity did not change upon magnetization, a significant component of DC conductivity appeared in the magnetized MAEs presumably due to denser clustering of interacting particles resulting in decreasing interparticle distances. The transition from a non-conducting to a conducting state was more pronounced for hybrid MAEs containing both NdFeB and Fe particles with a tenfold size mismatch. Hybrid MAEs also demonstrated a considerable increase in the real part of the complex relative permittivity upon magnetization and its asymmetric behavior in external magnetic fields of various directions. The effects of magnetic filler composition and magnetization field on the dielectric properties of MAEs are important for practical applications of MAEs as elements with a tunable dielectric response.

The adsorption properties of an unmodified ASD-4 aluminum powder and the powder modified with a V2O5 hydrogel are studied via low-temperature nitrogen adsorption. Special purity grade nitrogen is used as the adsorbate. Adsorption isotherms are measured, the specific surface area and porosity of the powders are calculated, and the results from morphological studies are described. The dependence of the structural and adsorption properties of the nanopowders on their composition is shown. Due to the island structure of the xerogel, the specific surface area of the modified aluminum powder is greater than that of the unmodified material by several tens of times. The specific surface areas of the ASD-4 and ASD-4–1% V samples are 0.6511 and 16.8752 m2/g, respectively. It is found that the layered structure of the deposited xerogel ensures the formation of mesopores with a size of 45 A in the modified sample.

Data on the effect of electromagnetic fields on polymerization processes are analyzed and integrated. The results of investigation of the response of polymeric systems including polymerization mixtures, polymer solutions, melts and gels to external electromagnetic fields are discussed. Mechanisms of changes in the kinetic parameters of cationic polymerization of certain monomers are considered. They are based on ideas of spatial redistribution of growing macroions and counterions depending on the degree of dissociation of the active sites, which can lead to an increase in the polymerization rate, stabilize it or slow down the process. It is shown that these mechanisms are universal for other ionic systems. Almost all types of polymerization processes are discussed to reveal potential fields of their application in additive manufacturing technologies. High demand for further studies of the effect of electromagnetic fields on polymeric objects is pointed out in connection with the need to solve problems in the design of novel materials and functional structures. The bibliography includes 214 references.

The sequence of phase formation in the oxidation of ASD-4 aluminum powder modified by vanadium pentoxide during heating in air in the temperature range 873–1073 K has been studied by synchrotron radiation x-ray diffraction. It has been shown that the sharp acceleration of the oxidation of the modified powder is related to the loss of the protective properties of the oxide shell on the particle surface due to the polyvalence of vanadium, which provides structural and phase changes on the surface and in the depth of the oxidized metal.

A magnetoelectric effect was discovered in polystyrene/organoelemental binuclear cobalt complexes with ligands of spatially hindered phenols at room temperature. The Dzyaloshinskii–Moriya interaction (dipole–dipole and anisotropic exchange interaction of unpaired electrons on cobalt ions at 77 K and room temperature) is fulfilled in such complexes. A novel class of high-temperature multiferroics—polymer composites—can be produced on the basis of such molecular structures.

A new class of high-temperature multiferroics has been created. They are polymer composites based on a polystyrene matrix and nucleus–shell nanoparticles, where the nucleus consists of silica nanoparticles and the shell consists of Fe(III) spin-variable ions.

Two catalytic systems, metallocene-based and Ti-based were used to synthesize by in situ polymerization the composites of polypropylene and few-layer graphene nanoparticles, prepared by chemical or thermal reduction of graphite oxide. The effect of metallocene and titanium catalytic systems on the properties of nanocomposites and distribution of nanoparticles in polymer matrix is investigated in detail. The data on electrical and thermal properties of nanocomposites are presented. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

The synthesis, structure, and electrophysical properties of a polymer-inorganic biocompatible composite based on unsaturated chitosan ether, namely, allyl chitosan, and vinyltriethoxysilane are studied. During composite synthesis, allyl chitosan forms an individual nanophase with vinyltriethoxysilane and its condensation products in the polymer matrix of allyl chitosan. The size of nanoparticles embedded in a polymer matrix increases from 50 to 1000 nm as the fraction of the added vinyltriethoxysilane grows. Under exposure to UV radiation, both homopolycondensation and heteropolycondensation occur in the composite films via crosslinking according to the radical mechanism and the composite becomes insoluble in water. It has been shown that the resulting composites feature ionic conductivity under application of both direct current and high-frequency electric fields to the sample. Conductivity is provided by a proton–electron ensemble that concentrates at the nanoparticle/polymer matrix interface.

A magnetoelectric effect has been found at room temperature in a polymer composite—polystyrene–metal–organic manganese dimers with ligands of spatially hindered phenol. It is shown that these metal-organic manganese dimers implement the Dzyaloshinskii–Moriya interaction and are weakly ferromagnetic. It is suggested that a new class of high-temperature multiferroics can be created on the basis of such molecular structures.

The adsorption and structural features of Al–5% Pb alloy powder before and after reacting with water are analyzed. Results from studying the morphology and phase composition of the oxidation products are presented, and the specific surface area and porosity of the powders are calculated. It is shown experimentally that water treatment of Al–5% Pb alloy powder even at room temperature leads to the formation of new phases and affects the powder’s morphology. It is established that a major role in the properties of the watertreated powders is played by nanopores that form between crystallites on a particle’s surface during waterinduced oxidation and subsequent thermal dehydration.

Poly(p-xylylene) – titanium thin film nanocomposites were synthesized by vacuum deposition polymerization and proposed to serve as a gas sensor. They can reversibly and selectively detect several parts per thousand water, ethanol and even n-propyl benzene vapors with short response time. The presence of polar molecules affects conductance and capacitance, while nonpolar vapors such as benzene and toluene have no effect on electrical properties. Polarization and depolarization currents were recorded and it was found that composition of gaseous medium affected the parameters of dielectric response function. The frequency dependences of complex capacitance were fit by the Debye equations; correlations of the fit parameters and titanium concentration, as well as dipole moment of analyte molecules in atmosphere were found. The model was proposed, that explains dielectric behavior of nanocomposites and assumes the existence of several dielectric relaxation processes with different characteristic times: orientation of physically adsorbed polar molecules, charge exchange of surface states, generated by chemisorbed molecules at the interface nanoparticle/polymer matrix and Maxwell-Wagner interfacial polarization phenomena.

The self-organization of detonation nanodiamond particles in dielectric liquid polydimethylsiloxane has been studied by broadband dielectric spectroscopy. Frequency dependences of the conductivity and the complex modulus of dielectric permittivity were measured. The structure of nanodiamond suspensions has been studied by small-angle X-ray scattering as well. Electrophysical properties of detonation nanodiamond suspensions, namely conductivity and permittivity, strongly depend on the particle surface chemistry. The temperature dependences show the activation nature of polarization processes. The model explaining observed effects has been proposed.

In view of the great practical utility of aluminum–rare earth metal (REM) powders as adsorbents and catalyst supports, the dispersion composition and morphology of Al–3%Y alloy powder particles obtained by various methods (gas plasma recondensation, nitrogen sputtering) were studied by low-temperature nitrogen adsorption, scanning electron microscopy, XRD, etc. The phase composition of the powders was determined, and the amount of active aluminum was calculated. The nitrogen adsorption on the powder surface was studied experimentally at–196°С at relative pressures of Р/Рs = 10–3–0.999. The specific surface areas of the powders were determined.

Reaction mixtures in which polymerization processes proceed are investigated both in an electric field and under classical conditions. The observed kinetic effects are explained using a model concept of the primary contribution to the revealed field effects from the dissociation of ion pairs due to the spatial redistribution of ions. This model may be applied to both cationic and anionic polymerization processes.