Key Engineering Materials Vol. 685

Abstract: In this paper presents the study of the process of interaction between helium (He) and methane (СH₄) molecules and the energy barrier created by a single-layer carbon nanotube. The interaction potential fields for the case of a tube as a nano-scale object interacting with single molecules or atoms were determined. Calculations show the dependence of molecular velocity within the symmetry axis of a single-layer carbon nanotube on the axial coordinate. The influence of the tube radius on the character of molecular passage through the open tube is considered.

Abstract: Tribological properties of a composite mixture based on zinc oxide nanoparticles and nanolamellar tungsten and molybdenum disulfide powders have been studied. XRD and TEM of ZnO nanoparticles produced by electric discharge of metallic granules in an H₂O₂ solution were analyzed. The tribological tests showed ZnO nanoparticles additive in metal disulfide powders did not practically change the friction coefficient in comparison with pure WS₂ and MoS₂ powders at 25 °C in air. At 400 °C zinc oxide nanoparticles in composite lubricants positively affect the wear resistance.

Abstract: The analytical method of residual strains determination on joints of layers of a glass-metal cylindrical shell arising in the course of its cooling description is provided in article. For the numerical implementation of the proposed model modern numerical and digital-analytical methods were used. In connection with the exponential change of the required functions close to butt ends of the shell numerical methods lead to instability of calculation. In order to overcome this obstacle, Godunov’s method of discrete orthogonalization was applied. It has significantly leveled disturbance peaks of strains on the surfaces conjunction of the composite shell layers.

Abstract: This paper presents the investigation of the influence of an added filling agent on the strength and hardness of composites based on the ultra-high molecular polyethylene UHMWPE. The results of the volume resistivity definition are demonstrated for the range of polyethylenes and composites based on UHMWPE.

Abstract: Nano- and microstructured composite materials have opened a new era for multifunctional materials. In particular, barium hexaferrites and carbon nanotubes can be applied in order to improve electromagnetic properties in composites. Magnetic materials with a texture based on barium ferrite and carbon nanotubes were obtained. The electromagnetic properties of Z – hexaferrites / carbon nanotubes composites were measured at microwave frequencies. It was shown, that imaginary permeability of barium hexaferrites/carbon nanotubes multilayer composites with double texture is as much as that of an isotropic samples at regions 3.4 – 8.5 GHz and 7.1 – 11.6 GHz.

Abstract: The authors investigated the mechanical mixing and compacting briquettes of nickel powder (particle size 30...75 μm) and nanopowder modifier SiC+Si₃N₄ (particle size 70...100 nanometers), obtained by the azide technology SHS. The mixtures containing 5%, 10%, 15%, 20% of the modifier were investigated. Mechanical mixing was carried out during 60 minutes in planetary mill «Pulverizette-5». Some physic-technological properties of the obtained powder mixtures, such as, particle size distribution, density, bulk weight and flowability, are determined. The powder compositions' pressing was carried out on hydraulic press PSU-50 with pressure 65...700 MPa. Nanopowder ligature briquettes of 18.2 mm diameter, height to 4.2 mm, weighing 5 grams, with relative density 70...89% and porosity 11...30%, intended for subsequent input in aluminum melt with the aim of modification are obtained.

Abstract: The “inverse” cathodic peak of gold nanoparticles is observed in the reaction mixture used to obtain gold nanoparticles HAuCl₄:Na₃C₆H₅O₇:NaBH₄=125:8:1 and accumulation time is 90 s. The conditions in which methionine has the greatest electrochemical activity were determined. They are as follows: the molar ratio of reagents HAuCl₄:Na₃C₆H₅O₇:NaBH₄=125:8:1 and accumulation time is 90 s, 0.1 M NaOH. The mechanism of methionine oxidation is proposed to be on the surface of the graphite electrode modified with gold nanoparticles in 0.1 M NaOH. The determination limit of methionine is 0.7 •10^-14 M. The proposed method is simple, sensitive, and does not need toxic substances.

Abstract: Novel electrically conductive SWCNT-reinforced composites were studied in this work. Incorporating SWCNT into CB/polymer composites provides lowering the percolation threshold. Adding a small quantity of single-walled carbon nanotubes into CB/polymer composites allows reducing CB content in electrically conductive composites and improving rheological and processing properties.

Abstract: The multilevel approach towards the study of a deformable solid considers a determining role in the deformation and failure of coupling factors and the necessity for combined deformation of its surface layers and volume. At high-cycle fatigue under the reverse bending conditions the plastic deformation is practically concentrated on surface layers. The paper presents the mechanisms of fatigue deformation for high-purity aluminium at various fatigue stages.

Abstract: The composite powder of AlN-BN is of interest from the point of view of the use for sintering the AlN-BN composite ceramics. The ceramics compared with AlN ceramics would have better thermal shock resistance, less britlleness, better machinability, good heat conductivity and tribological properties. Possibility of obtaining a composite powder of AlN-BN with the application of process of self-propagating high-temperature synthesis (SHS) from powder mixtures of NaN₃ and precursors of aluminum and boron was investigated. Halide salts AlF₃, Na₃AlF₆, KBF₄ and NH₄BF₄ were used as the precursors. It was shown that these mixtures are capable of burning and obtaining agglomerated composite powders from nanosized (50-170 nm) particles.