Copper-containing nanocomposites on the basis of isotactic polypropylene and butadiene-nitrile rubber

The influence of additives of nanofillers (NF) containing nanoparticles of copper oxides stabilized by a polymer matrix of high-pressure polyethylene (PE) obtained by the mechanochemical method on the structure and properties features of metal-containing nanocomposites based on isotactic polypropylene (PP) and butadiene-nitrile rubber (BNK) is studied by X-ray phase (XRD) and differential thermal analyses(DTA). The improvement of strength, deformation and rheological parameters, as well as thermal-oxidative stability of the obtained nanocomposites was revealed, which, apparently, is associated with the synergistic effect of interfacial interaction of copper-containing nanoparticles in the PE matrix with the components of the PP/BNK polymer composition. It is shown that nanocomposites based on PP/BNK/NF can be processed both by pressing method and by injection molding and extrusion methods, which expands the scope of its application.

Microwave carbonization of cotton fiber for the production of carbon materials

This article presents the results of comparative studies of the structural and physico-chemical features of cotton lint samples carbonized by the microwave method and the standard (thermal) method. The dependences of the temperature change of the samples during the microwave carbonization process are obtained. The heterogeneity of the morphology of the fiber surface along the cross-section of the microwave carbonized sample was revealed. It is shown that the structure of the surface layers is characterized by two mechanisms of fiber destruction: numerous brittle transverse fractures and coloring of the fibers in places of swellings (a sharp increase in their diameter) and fluffing of the surface into convoluted fibrils with a transverse size of 50 – 300 nm due to the destruction of the outer layers of the secondary fiber wall. In the central region, the destruction of fibers occurs by the formation of longitudinal interfibrillary slits and the delamination of the secondary fiber wall, which leads to the formation of pores with dimensions of 50 – 200 nm. It is established that during the microwave carbonization process, the central part of the sample is almost completely freed from impurities that are deposited on the fibers of the surface layers. It is shown that the integral adsorption capacity of the microwave carbonized sample is higher than the adsorption capacity of the sample carbonized by the thermal method (126 mg/g and 47 mg/g, respectively). It was found that during microwave exposure more than 10 minutes, regions with an adsorption capacity of ~ 350 – 450 mg/g appear in the carbonized material, that is comparable to the capacity of samples activated by the standard method.

Study of a highly porous composite material based on an aluminum matrix with an ordered cellular structure formed by hollow copper-graphite spherical granules

The structure and properties of a highly porous cellular composite material based on a framework of hollow spherical granules with a thin copper-graphite coating impregnated with an aluminum alloy have been investigated. Highly porous composite composite casting with molten form, filled with expanded polystyrene spherical granules with a thin copper-graphite layer applied to their surface. When the polymer core of the granules burns out in the casting, a highly porous cellular composite material is formed with an aluminum matrix filled with spherical pores ∅ 4 – 8 mm, adjoining the metal matrices through a thin (300 – 500 μm) copper shell. The density of the porous composite material obtained in this way is 1.67 g/cm3. In order to fill the space between the granules with aluminum melt, their surfaces were coated with a thin layer of titanium, molybdenum, or chromium borides, which positively affected the strength characteristics of the composite material as a whole. Estimated calculation of the shock absorber index of a new highly porous structural material based on aluminum matrices with a cellular structure made of spherical hollow granules regularly distributed over the volume proved the prospects of its subsequent use as an absorber of shock energy in shock-absorbing devices.

Influence of the processing method on the heat resistance of the secondary block copolymer of propylene and ethylene filled with rice hulls

Polymer composites based on secondary thermoplastic polymers filled with biodegradable components of plant origin was developed. Repeated thermal and mechanical action on polymers during their processing in the presence of dispersed phase particles leads to a change in the thermophysical and strength characteristics of finished products. The paper studies the regularities of changes in the heat resistance of polymer composites based on a secondary block copolymer of propylene and ethylene, and rice husks, processed by injection molding and pressing. It is shown that filling the secondary polymer with rice hulls leads to an increase in the heat resistance of composites, which is characterized by an increase in the bending temperature under load, Vicat softening temperature, and decomposition temperature during thermogravimetric analysis in an inert atmosphere. Compared to the injection molding method, the processing of polymer composites by pressing makes it possible to obtain more heat-resistant plastic products. Obviously, this is due to the different degrees of crystallinity of the polymer phase. The high cooling rate of the polymer composite melt during the filling of the injection mold reduces the time required for the corresponding change in the conformation of macromolecules and the formation of the crystalline phase. As a consequence, an increase in the content of the amorphous phase of the secondary block copolymer of propylene and ethylene decreases the heat resistance of the prototypes.

The structure and properties of sheets from the new alloy V-1381 of the Al – Mg – Si system

The results of the development of a new alloy of the Al – Mg – Si system of the 6xxx series, which received the V-1381 grade, are presented. The influence of the composition and modes of heat treatment on the mechanical and corrosion properties of sheets with a thickness of 1,0 and 3,0 mm, manufactured under the conditions of FSUE “VIAM”, was investigated. Average level of sheet properties: UTS = 410 MPa, YTS = 360 MPa, El = 11.5 %; fatigue crack growth (dl/dN) = 0,59 mm/kcycle at ΔK = 18,6 MPa·m1/2, intergranular corrosion ≤ 0,15 mm, exfoliation corrosion 4 points. It was found that the structure of the sheets is recrystallized, the main strengthening phase is the coherent matrix β’(Mg2Si)-phase evenly distributed in the volume of grains with a high density. There is also a heterogeneous origin of β′-phase on dislocations and dispersoids. At grain boundaries there are zones free from emissions with a width of 15 – 20 nm. Dispersoids of various morphologies are observed in the tested samples. Temperature and heat values of phase transformations in ingots and sheets are determined and established liquidus and solidus points. The sheet weldability was evaluated by automatic argon-arc welding and the critical rate of deformation of the weld metal during crystallization was determined, at which no cracks were formed in it. Laser welding mode has been developed to ensure optimal formation of geometric parameters of the weld.

Gradient structures of Ni – Zn ferrites for electromagnetic radiation protection devices

Increasing the reliability requirements for electromagnetic compatibility of electronic equipment requires the creation of protective coatings that absorb electromagnetic radiation or the development of new radio-absorbing materials. In the frequency range up to 1 GHz, radio-absorbing materials based on Ni – Zn ferrites are of the greatest interest. The absorption of electromagnetic radiation by ferrites occurs due to resonant phenomena at the level of domains and atoms. Improving the performance of ferrites is possible by modifying their surface properties. In this paper, gradient structures for electromagnetic radiation protection products are obtained by treating the surface of Ni – Zn ferrite samples with a low-energy electron beam. To generate the electron beam, a unique development was used — a forevacuum plasma electronic source that allows forming and transporting a beam with a power density of up to 105 W/cm2 under conditions of high pressure and high gas release. As a result of processing, gradient structures were found on the surface of ferrites. A theoretical analysis and experimental study of the obtained structures “non – magnetic conductor – ferrite”, characterized by an increased attenuation coefficient and a reduced reflection coefficient of electromagnetic radiation in the frequency range from 0.5 to 2.5 GHz. The possibility of obtaining near-surface layers depleted in zinc with increased electrical conductivity and reduced magnetic permeability is shown.

The air permeability of composite fiber material

The air permeability of composite materials obtained by impregnating a non-woven needle-punched cloth with latex was investigated. The permeability of composite materials with different rubber content was estimated by the coefficient of air permeability at a pressure drop of 49 and 100 Pa. The dependence of the air permeability coefficient on the degree of impregnation of the fabric showed that at 15 – 20 % of the rubber content, the maximum air permeability coefficient is observed, and when the degree of impregnation increases, the air permeability coefficient decreases. The process of forming a porous structure of composite materials and its influence on air transport is considered. The increase of the coefficient of permeability is explained by the fixation of the fibers of the surface layer with limited mobility under the action of air flow, and a reduction in the coefficient of air permeability by reducing pore space and an increase in fiber matrix composite materials in the process of sushi-Ki-impregnated material. The air permeability of composite materials is determined by the ratio between the processes of increasing the volume of the fibrous matrix and reducing porosity when filling the space between the portages with rubber particles. A model is proposed for calculating the coefficient of breathability of composite materials of known density.

Features of damage and modification of surface layers of Al and its alloys by powerful energy flows in a plasma focus device

The results of the analysis of damageability and modification of the structural-phase state of the surface layers of aluminum and its alloys by powerful flows of fast high-energy ions and high-temperature plasma in Plasma focus devices, as well as using pulsed laser radiation. Pure Al, an alloy of the Al – Mg – Li system, a duralumin alloy, and a composition of a ceramic coating Al2O3 on an Al substrate are considered. It is shown that in the regime of Al irradiation with a power density of q ≈ 106 – 107 W/cm2 in the nano- and microsecond range of pulse durations, ultrafast crystallization of melted surface layer occurs with the formation of a wavy surface relief and the structural fragments of sub-microcrystalline and nanoscale size. After the action of deuterium plasma flows on a duralumin alloy tube located along the axis of the Plasma focus device a modification of the structural-phase state of the alloy is observed: the initial two-phase state of an αAl-solid solution of copper in aluminum and inclusions of the second phase of CuAl2 became fine-grained and single-phase due to the dissolution of CuAl2 particles in the melt. Irradiation of an alloy of the Al – Mg – Li system containing (wt %) 2 % Li and 5 % Mg at q = 5·106 W/cm2, t = 50 – 100 ns after four pulsed impacts of fast ions and deuterium plasma led to the modification the structural-phase state of the surface layer of the alloy, associated with an increase in the content of magnesium oxide and a decrease in the crystal lattice parameter of the Al-based solid solution. The formation of spherical cavities due to the evaporation of lithium into the internal micropores of the surface layer was also found. The low damage and structural stability of Al2O3 ceramics on an Al substrate under beam-plasma impacts in plasma focus device with a radiation power density q ≤ 108 – 109 W/cm2 in the nano- and microsecond range of pulse duration is noted. At the same time, the Al2O3/Al composition was unstable to pulsed laser radiation in the free-running mode (q = 105 – 106 W/cm2, t = 0.7 ms) and Q-switch mode (q = 107 – 108 W/cm2, t = 80 ns). In both cases the coating peeled off from the substrate.

Analysis of plasma effect on ultrahigh-molecular weight polyethylene fibers’ surface energy on strength of fibers and fiber reinforced composites

Completely saturated chemical bonds in ultrahigh-molecular-weight polyethylene (UHMWPE) fibers — are a reason for their low surface energy (FSE), i.e. inert properties. Elongated crystal structure of UHMWPE molecules ensures high anisotropic tensile strength of the fibers. An inertness is a problem for utilization these fibers in high-strength composites production. Surface energy (SE) difference of the fibers and a binder in fiber/matrix system hinders chemical interaction at interphase boundary and worsens fiber wettability. Increase in their FSE is a topical task for this problem decision. Necessary condition of FSE increase is the integrity of molecule structure, lying under modified surface. Low temperature, nonequilibrium plasma (LTP) treatment in a medium of argon and argon/propane mixture, used in this work for plasma activation of fibers’ surface, permits to abide by this condition. However, plasma ion bombardment during a process of activation can modify interior crystal structure and, as a result, decrease their strength. The rovings SK75 (Holland) and D800 (China) were used for study of the properties of UHMWPE fibers after plasma treatment. Activation effect on FSE, strength, and fibers’ wetting by water and epoxy binder before and after ageing was studied. Capillary wetting of the fibers by distilled water used for FSE evaluation. The data of filaments surface structure and their diameter change at maximal load, obtained by optical microscope study, were used for the analysis of FSE and epoxy matrix effect on the strength of fiber/matrix systems. Essential distinction of SK75 and D800 fibers properties is ascertained. Negative effect of fibers’ and matrix’s stiffness, as well as increased FSE of stiff fibers on the strength of fiber/matrix system is revealed.

Electrical properties of aluminum oxide ceramics film on a metal

The work is devoted to the study of electrical properties (temperature dependences of conductivity, relative dielectric constant, dielectric loss tangent for various frequencies) of an aluminum oxide ceramic film deposited on a metal substrate. The film was created by the original method of electron beam evaporation of a non-conductive target, consisting of a compressed alumina powder, using a plasma electron source, which is able to reliably operate in the fore-vacuum pressure range (5 – 100 Pa). Such increased working gas pressures ensures the generation of a dense beam plasma near the target, which neutralizes the charging of a non-conducting target and thereby provides its effective melting and electron beam evaporation.