Vol 10, No 2 (2019)

The microstructure of Al₈₅Ni₅Fe₇La₃ amorphous alloy after high-speed quenching, isothermal annealing, and flash lamp annealing (FLA) was studied by electron microscopy (including the high-resolution transmission electron microscopy), electron and X-ray diffraction, energy-dispersive X-ray microanalysis, and differential scanning calorimetry. A comparative analysis of the structures with respect to phase composition and phase morphology was performed. It was shown that, after the quenching, an X-ray amorphous structure is formed in the alloy. Critical parameters of heat treatment of the amorphous alloy which lead to single-phase or multiphase crystallization and volumetric or gradient structure were determined. The phase composition of the nanocomposite formed during crystallization was determined. The identity of the emerging structures with respect to the phase composition and phase morphology was determined for certain parameters of isothermal and flash lamp annealing to which close values of microhardness significantly exceeding the hardness of the alloy in the amorphous state correspond.

This article analyzes thermophysical properties of disperse-filled metal polymer composites, also known as feedstocks, which are used in injection molding. Analytical models of specific heat capacity, effective thermal conductivity, and thermal diffusivity of such materials are reviewed. It is mentioned that the existing models can be applied only for an evaluative calculation of thermophysical properties of feedstocks. Differential scanning calorimetry (DSC) has been applied to measurement of temperatures characterizing melting of polyoxymethylene in binder of Catamold 42CrMo4 feedstock used for injection molding of parts of 42CrMo4 steel, an analog of 38KhMA steel. The specific heat of this phase transition has been determined. The temperature dependences of specific heat capacity, effective thermal conductivity, and thermal diffusivity of Catamold 42CrMo4 feedstock have been estimated. The calculated thermal diffusivity and specific heat of the considered feedstock have been verified with experimental data obtained by laser flash analysis (LFA) and DSC. It has been demonstrated that the thermophysical properties of feedstocks differ significantly from those of both metals and unfilled polymers. Specific thermophysical properties of feedstocks lead to variations of norms of technological molding modes applied in the plastics industry and norms of technological molding modes of feedstocks.

In the manufacture of products instead of unfilled polymers, such as ultra-high-molecular-weight polyethylene (UHMWPE), it is more effective to use composite systems with reinforcing inclusions. The paper discusses the possibility of creating a composition with the given physical and mechanical properties. An approach to the determination of control parameters (phase composition, phase properties) giving the material the specified effective properties or their entry into predetermined intervals is proposed. In accordance with this approach, on the basis of the analysis of experimental data containing information about the effective characteristics depending on the values of the control parameters, the corresponding surfaces of the response of physical and mechanical characteristics to the values of the control parameters are constructed in the state space. The obtained surfaces make it possible to identify the range of control parameters for the given characteristics of multicomponent polymer compositions based on UHMWPE.

The regularities of the effect of the variation in the chemical composition of the new Russian β‑solidifying TiAl-alloy (Ti–44.5 Al–2 V–1 Nb–2 Cr/1 Zr–(0–0.1) Gd, at %) within the chromium content from 1.5 to 2.5 at % (2.0–3.5 wt %) and zirconium from 0.5 to 1.5 at % (1.2–3.5 wt %), as well as the effect of gadolinium microalloying on the phase composition and the structure of ingots, have been studied. The ingots were obtained using double vacuum-arc remelting with the subsequent vacuum-induction melting and pouring of the melt into the steel chill mold at the melting-casting unit with a cold crucible. It is shown that 0.1 at % gadolinium microaddition results in a decrease in the average size of the macro grains from 3000 ± 500 μm to 400 ± 80 μm in the peripheral part of the ingots after the first remelting. It was found that the phase composition of TiAl-alloy compositions with Cr and Zr is represented by three main phases: γ-TiAl, α₂-Ti₃Al, and β-phase. The volume fraction of β-phase does not exceed 2–3% in ingots containing Zr, while it reaches 5–6% in ingots containing Cr. It was revealed that the microstructure of the ingots of all studied chemical compositions has a lamellar morphology. Sprouting of lamellar colonies through the grain boundaries was noted for ingots containing Zr.

The formation of a terrace-step surface nanostructure disoriented with respect to the R-plane on sapphire crystals is studied. The possibility of the formation of atomically smooth steps with a height about 0.34 nm is shown. This size corresponds to the interplanar distance of 0.34 nm along the direction [012] in a sapphire crystal. The substrates prepared in such a way are used in the course of the epitaxy of Fe₂O₃ and In₂O₃ films. A method of a high-temperature oxidation of previously deposited iron and indium films under atmospheric conditions is used. It is shown that the structural and geometrical similarity of Fe₂O₃ and sapphire crystal lattices promotes the growth of epitaxial films aligned with respect to the substrate. It is determined that the stress occurring in the growing In₂O₃ films in the course of oxidation and solid-phase epitaxy, as well as owing to a discrepancy between the lattice parameters at the film–substrate interface, is insufficient for the formation of the metastable rhombohedral In₂O₃ phase. The influence of terrace-step nanostructure of the surface of substrates at the initial stages of the growth of epitaxial films is discussed.

Capillary-porous systems (CPS) with liquid lithium are considered as a prospective alternative to traditional structural materials (W, Be, CFC) during the production of in-vessel elements contacting plasma of stationary thermonuclear reactors. The behavior of CPS with liquid lithium under the impact of pulsed deuterium plasma flows is considered. The basic processes determining the high stability of CPS against damage are revealed and the critical parameters defining the CPS resistance are specified. The behavior of the tungsten-lithium CPS after its interaction with atmospheric gases is studied in experiments on a plasma facility at the Ioffe Physical-Technical Institute. The irradiated samples of the CPS were studied by optical and scanning electronic microscopy and local X-ray spectral and X-ray diffraction analyses. The surface temperature was measured using a bicolored pyrometer during deuterium plasma irradiation. The outcome of the plasma effect on the heavily oxidized CPS surface substantially differs from that for a pure surface: there is damage to the CPS structure. The specific power of the plasma flow was 22–41 GW/m², and the number of pulses per irradiated target was 100.

The following investigation of the damageability of the Al₂O₃ oxide ceramic coating on the aluminum substrate under the influence of the concentrated energy fluxes of different nature and pulse duration performed: pulsed laser radiation in the free running mode (at the power density of q = 10⁵–2 × 10⁶ W/cm² and pulse duration of τ_i = 0.7 ms) and modulated Q-switched mode (q = 10⁷–10⁸ W/cm², τ_i = 80 ns), as well as the beam-plasma influence at q = 10⁷–10⁹ W/cm², τ = 50–100 ns. It is shown that, under the influence of laser radiation within the millisecond and nanosecond ranges of the pulse impact on a semitransparent ceramic coating, the partial destruction and peeling of the ceramic layer from the metal substrate is observed. The mechanisms of the observed damageability are determined. The threshold values of the laser radiation flux at which the coating is damaged, caused by peeling, are experimentally estimated. The distribution of the temperature in the surface layer of the samples was calculated by numerical simulation, and it was shown that during laser irradiation the temperature reaches its maximum values at the depth corresponding to the contact area between the coating and substrate. It was established that the impact on the aluminum samples with the ceramic coating from the fast deuterium ion fluxes and high temperature deuterium plasma in the plasma focus device results in melting and partial evaporation of the coating surface layer; but in this case, no cracking or peeling from the aluminum substrate is observed.

Investigations of the carbon film synthesis on the surface of steel orthopedic structures obtained by ions implantation of argon ions (accelerating voltage U_acc = 40–130 kV and dose range F = (1.25–3.1) × 10¹⁶ ion/cm²) in a carbon dioxide medium have been conducted. It is shown that implantation of Ar⁺ ions in a CO₂ environment leads to a significant increase in microhardness of medical steel surface (up to 31 GPa). The method of ion beam modification of the carbon diamond-like film by implantation of silver ions (accelerating voltage 50 kV and dose range 1.2 × 10¹⁶–1.8 × 10¹⁶ ion/cm²) to impart antimicrobial surface properties has been proposed. The studies in vivo have proved that the steel implants modified by the developed ion beam method efficiently take root in the bone tissue without inflammatory processes in the surrounding biostructures.

Gas-filled composite materials were obtained by foaming of low density polyethylene (PE) and introduction of natural components. Particulate chemical gas-generating agent hydrocerol was used for the polyethylene porosity. Particulate biodegradable filler, wood flour, and corn starch were used as the natural components. Investigation of structure, physical, and physicomechanical properties of the materials was performed. It is shown that the polyethylene structure became inhomogeneous: pores and foreign inclusions were observed. The density and physicomechanical properties decreased. It is noted that such peculiarities of the material as low density and the presence of pores and particles of the hydroscopic filler increase the capacity for biodegradation. Evaluation of the capacity of the material to degrade in the environment was conducted. Results of the evaluation demonstrate the weight loss of the samples with the biodegradable filler, which may be explained by the destructive effect of microorganisms, partial washing of the filler, and fragmentation of the sample. The samples of the gas-filled composite materials, with reduced performance properties but retained at a sufficient level, proved the promising outlook for their application as packaging materials and sealing packaging elements for the nonfood goods.

Protein-silica composites are a promising platform for the development of new dosage of protein drugs. The sol-gel method was used to synthesize bovine serum albumin composites with colloidal silica in the presence and absence of trehalose as a protein structure stabilizer. The structural state of the protein in the composites and after release from them and the kinetics and mechanisms of in vitro release were studied. The functional properties of the sol-gel composites were compared with similar composites obtained by the adsorption method. The strong effect of the synthesis method and the influence of trehalose on the structure of the protein and the kinetic parameters and mechanisms of its release were shown. On the basis of a comparative analysis, it was concluded that sol-gel composites have a number of advantages over adsorption-derived composites in terms of their functioning as delivery systems of protein drugs.

This paper presents the results of a study of the effect of the butyl rubber and dicumyl peroxide concentrations on the strength and thermophysical properties of polymer mixtures based on thermoplastic polyolefins. The principal possibility of synthesizing thermoplastic elastomers with predetermined physical and mechanical characteristics is shown. The butyl rubber concentration is varied from 0 to 50 wt %, and the dicumyl peroxide concentration is varied from 0.5 to 2.0 wt %. It is experimentally established that, in the process of studying the deformation–strength properties for thermoplastic polyolefins, the appearance of tensile yield stress and ultimate tensile stress is typical. However, as the concentration of butyl rubber in the thermoplastic composition increases, the difference between tensile yield stress and ultimate tensile stress is sharply reduced. And, when the difference between these strength parameters disappears completely, the polymer composition starts exhibiting the properties of a thermoplastic elastomer. The additional introduction of a crosslinking agent, namely, dicumyl peroxide, into the composition of polymer mixtures promotes the appearance of a high elasticity plateau on the thermomechanical curves, which, as is well known, is characteristic of vulcanized rubbers. The most optimal concentrations of dicumyl peroxide and butyl rubber are determined, as a result of which the highest physicomechanical properties are achieved in the polymer compositions. An interpretation for the observed regularities of the change in the physicomechanical and physicochemical properties of polymer composite materials is given.

Diesterdisulfoanhydride of 2-hydroxypropyl saccharin-6-carboxylic acid has been obtained by interaction of monoanhydride of sulfoimide of saccharin-6-carboxylyc acid with 1,3-diacetine. The composition and structure of the synthesized compound have been confirmed by the elemental analysis and IR spectroscopy data. The obtained product has been used as a curing agent and a plasticizer for industrial ED-20 epoxy resin. It has been established that diesterdisulfoanhydride of 2-hydroxypropyl saccharin-6-carboxylic acid is an effective curing agent and plasticizer for ED-20 epoxy resin. The composition curing process has been studied by differential thermal analysis using a Paulik-Paulik-Erdey derivatograph. On the basis of the data obtained, it has been revealed that the synthesized diesterdisulfoanhydride combines well with ED-20 epoxy resin but cures it in a severe temperature mode. It has been shown that, by using nadic methyl anhydride as a cocuring agent and an accelerator, the curing temperature range of the composition is shifted to a lower temperature zone. The compositions and structures of initial epoxy resin and cured products have also been determined by elemental analysis and IR spectroscopy.

To determine the possibility of maintaining the maximum possible carbon content in TiC carbide, a powder additionally doped with chromium carbide, molybdenum, and carbon was produced by plasma spraying of the cermets of the TiC–NiCr system. To reduce the effect of gases from the air atmosphere, plasma spraying was carried out using a standard plasmatron, supplemented with a special nozzle. The analysis of the oxygen, nitrogen, and carbon content in the powder manufacturing stages and in the coatings was carried out. The content of O and N is reduced in the sintering step for spraying a powder with respect to the content in the starting components, but increases again during spraying. In the coating, the quantitative distribution of the carbide phases was determined by their size. A change in the phase composition and dimensions of the crystal lattices of the phases in the powder for deposition and coatings was determined. The share of the main hardening TiC phase in the coating decreased by 9.7% with respect to the initial mixture, but taking into account the newly formed carbide phases with the participation of chromium and molybdenum, the proportion of all the carbide phases in the coating increased by 12.7%. The microhardness of the plasma coating at loads of 200 and 20 g on the indenter was 14.9 and 28.7 GPa, respectively. The reasons for the decrease in the actual microhardness of the cermet coating in relation to the theoretically possible one based on the volume fraction of the strengthening phases are analyzed.

In this paper, we analyzed the methods of synthesis and sintering of aluminum oxynitride powders. Samples of a ceramic material based on aluminum oxynitride were produced. The effectiveness of two sintering methods in induction and resistance furnaces was evaluated in the temperature range of 1750–1950°C and for the exposure time from 2 to 10 h. Structures of the obtained samples were studied by scanning electron microscopy, while the phase composition was studied using X-ray phase analysis. The effect of the heating parameters, sintering atmosphere, and quality of the initial powders on the formation of the aluminum oxynitride phase was considered. A sample sintered in a vacuum furnace without a nitrogen atmosphere did not have the aluminum oxynitride phase because of the release of nitrogen from the sample volume and had a strong shrinkage. Induction sintering in a nitrogen atmosphere made it possible to achieve ~85% concentration of the target phase, aluminum oxynitride, with density of 85% of theoretical (3.69 g/cm³). These results were obtained in the mode of exposure for 10 h at 1750°C.

This article describes the strength properties and microstructure of Al–Mg–Si alloys positioned on a quasi-binary Al–Mg₂Si cross section and doped with minor amounts of scandium with zirconium and scandium with hafnium; after quenching, these alloys were exposed to severe plastic deformation and cold rolling with subsequent aging. It was demonstrated that, in the alloys with 1.4% Mg₂Si and doped with Sc + Zr and Sc + Hf after equal channel angular extrusion and subsequent cold rolling, the highest strength was that of the alloys doped with scandium with zirconium. The lowest strength was that of the alloys both doped and not doped with scandium, zirconium, and hafnium after equal channel angular extrusion. It has been established that cold rolling of quenched alloys and alloys after equal channel angular extrusion improves strength properties after aging at 170°C in comparison with those aged at the same temperature only after equal channel angular extrusion or only after cold rolling. Analysis of the microstructure has shown that strengthening of the alloys is attributed to slight distortion of the crystalline lattice of aluminum solid solution which is achieved by cold rolling of the alloys aged after equal channel angular extrusion.

In this paper, we synthesized the organic–inorganic terpolymers based on poly(titanium oxide) ((≡TiO)_n), hydroxyethyl methacrylate (HEMA), and various organic vinyl monomers (styrene, vinylbutyl ether, butyl methacrylate, isobornyl acrylate, 2-ethylhexyl acrylate, acrylonitrile, and methyl methacrylate) by using a polycondensation-polymerization method. Independent of the composition, the terpolymers are optically transparent in the visible spectral range (transparency is T ~ 90%). Using X-ray phase analysis, the terpolymers were established to have an amorphous structure, and the poly(titanium oxide) chains are self-organized into anatase-type nanoclusters. The dimming of terpolymers occurred under the effect of UV irradiation as a result of the reversible photochromic one-electron transition Ti⁴⁺ + \(\bar {e}\)\( \rightleftarrows \) Ti³⁺. The change in the nature of monomers of terpolymers and the molar ratio of their components allows controlling the rates of both direct and reverse reactions and also leads to the modification of the strength characteristics of the materials. The biggest change in light transmission under UV exposure for 180 min is observed in terpolymers with styrene, butyl methacrylate, and acrylonitrile monomers at a molar ratio of the components [(≡TiO)_n] : [HEMA] : [M] = 1 : 5 : 1; the corresponding changes are 55, 70, and 60%. Higher rates of the Ti³⁺ → Ti⁴⁺ + \(\bar {e}\) reaction (clearing) are observed for materials of the indicated composition, as well as for terpolymers with vinylbutyl ether monomers. The effect of photoinduced superhydrophilicity was found for terpolymers; i.e., a ~60° reduction in the contact angle of their surface under UV exposure was observed.

The paper considers plasma-chemical modification of facing composite material on the basis of hollow glass microspheres with decorative protective coatings. It is shown that the technology of obtaining decorative protective coating by the method of plasma reflow is highly efficient and energy-saving, which will allow competition with traditional technologies and significantly reduce the cost of finishing work. Compositions of decorative protective coatings based on high-alumina refractory and liquid glass have been developed. It was revealed that the use of high-alumina refractory crushed material in the intermediate layer makes it possible to reduce the number of microcracks and eliminate the consequences of high-temperature impact on the matrix of fine-grained concrete. The positive effect of hollow glass microspheres on the minimization of thermal shock was established. The results of the investigation of the effect of plasma-chemical modification on the phase composition and structural features of the facing composite material on the basis of hollow glass microspheres with a decorative protective coating are presented. The regularity of layer-by-layer variation of the phase composition and the macro- and microstructure of the decorative protective coating of the facing composite material is established. It is shown that the upper layer is represented by Na–Ca–Al–Si glass, the middle glass ceramic layer is represented by the glass phase and α and β modifications of aluminum oxide, and the lower dehydration layer is represented by dehydration products of hydrosilicates and α and β modifications of alumina. High-temperature action of the plasma jet intensifies thermal diffusion, which in turn leads to a redistribution of oxides along the thickness of the decorative protective coating.

The possibility of fabrication of a gradient absorber of electromagnetic waves with small thickness having an efficient level of electromagnetic radiation absorption in the frequency range from 10.0 to 37.5 GHz in which the reflection coefficient does not exceed –15 dB is shown. The fact of formation of a gradient behavior of the distribution of concentration of conductive filler in material from a minimum value on an external surface to a maximum value on an internal surface was revealed. It was found that the developed absorber of electromagnetic waves owing to the compacted surface layer, which is produced at a formation stage, can be used without additional metallization of internal surface, which makes it possible to simplify use of a material in designs and reduce its weight. The results of comparison of frequency dependences of the reflection coefficient of the developed electromagnetic wave absorber with materials similar in composition with uniform distribution over the volume of conductive filler are presented.

Porous ceramic materials based on oxide fibers, which have lower specific density and thermal conductivity, are able to function at temperatures exceeding 1000°C, including in an oxidizing atmosphere, which allows this class of materials to have a wide range of applications in various industries. The disadvantage of such materials is the hydrophilicity caused by the chemical composition of the fibers and the highly developed porous structure, which severely limits their use, particularly in arctic and subarctic climates characterized by high humidity. The authors have investigated and proposed a method of hydrophobization using the technology of low-temperature postradiation graft polymerization of tetrafluoroethylene molecules. The technology makes it possible to apply polymer coatings to oxide fibers, providing high hydrophobic properties, which is manifested in the increased value of the contact angle of wetting the surface of the material, which in turn substantially improves their operational characteristics and expands the possibilities of practical application as heat-shielding and heat-insulating materials.

Formation the structural and functional properties of carbon black (CB) during the synthesis stage or through post-treatment is an important practical problem that will lead to the development of special types of this material, and those with superior electrical conductivity properties are of primary importance. This work is a continuation of our previous research and concerns the structure–property relationships that arise as a result of applying basic process techniques. Done and studied the effects of gas-phase thermochemical modification (thermal oxidation and thermal modification at temperature up to 3000°C) and its technological parameters on the characteristics of microstructure, texture, and surface chemistry of CB particles and the relationships between these parameters and electrical physical properties of CB powders. We study the effect that the combined treatment—thermal treatment at 3000°C followed by gas-steam activation at 900°C—has on CB powders. For the prepared CB powders, we use an array of different characterization techniques to establish the relationship between the structure and microstructure, on the hand, and the electrical conductivity, on the other hand: X-ray diffraction analysis, Raman spectroscopy, electron paramagnetic resonance, high-resolution transmission electron microscopy, and low-temperature nitrogen adsorption. The bulk electrical resistance is measured on samples prepared by compression of CB nanopowders under a pressure as high as 200 atm. We carry out a comprehensive characterization of the particle structure for different types of CB and compare them to commercial conducting types of CB of both domestic and foreign origin. The observed effects are interpreted in terms of ideal crystalline carbon systems (i.e., graphenes), which have been in spotlight of both fundamental and applied research in the past years.