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The carbon nanotubes (CNTs) embedding into metal-matrix composites is accompanied with difficulties in providing their uniform distribution within the matrix. Therefore, choosing a way to add CNTs into a metalmatrix and a general technological route for composite-material fabrication are crucial tasks. This study aims to develop copper–CNT composites by powder-metallurgy methods from composite powders and to analyse the structure and properties of such materials. The composite powders are produced by electrodeposition from the copper-bearing sulfuric acid electrolyte. The CNTs are dispersed in electrolyte, using sonication in the presence of surfactants having the different-type actions. In this research, anionic surfactant sodium lauryl sulphate NaC12H25SO4 (SDS) and cation surfactant cetyltrimethylammonium bromide C19H42BrN (CTAB) are used. Multiwalled CNTs (with outer diameter of 8–28 nm and length of 0.5–10 μm) are prepared by the chemical vapour deposition (CVD) and thermally annealed at temperature of 650C through catalysts Al2O3–Fe2O3–MoO3. The concentration of CNTs in the plating bath is of 0.15 g/l. The electrodeposited copper powder is used as a matrix for sintered samples’ fabrication. Samples for the investigation are compacted at pressure of 400 MPa and sintered at 950 C in a hydrogen atmosphere. The study of sinteredsamples’ structural characteristics is performed, using the scanning electron microscope (Tescan Mira 3 LMU). The local microanalysis of the samples’ elemental composition is made by energy dispersive spectroscopy (EDS) with a radiation detector ‘X-max 80’ (‘Oxford Instruments’, England). The amperemeter and voltmeter method is used for the resistance measurement of sintered samples. After samples’ sintering, the CNTs in the copper matrix are revealed mainly at the grain boundaries and within the pores. The CNTs content increasing (in investigated limits) reduces the electrical resistance of the sintered material. The highest content of CNTs is provided by deposition in the electrolyte with cation surfactant CTAB. The investigation results are helpful for the copper materials’ manufacture for electrical contacts. [ABSTRACT FROM AUTHOR]

The purpose of this work is to obtain information on the behaviour of the deposits of aluminium alloys depending on the time and temperature of annealing, and their effect on the mechanical properties. The cycle of tests carried out made it possible to determine the conditions for the formation of precipitation, however, in practice, the results are influenced by external factors such as the geometry of the samples, the conditions of their heating and cooling. Therefore, results of tests conducted in accordance with the requirements of the European standards (DIN), can be improved by conducting preliminary tests. The increase in the hardness of these alloys occurs due to dispersed solidification of deposits, and the maximum hardness is achieved with partially coherent deposits. The conducted SEM studies show that the hardness of the prototypes of the AlSiMg alloy depends on the temperature and time of annealing. After quenching, with an increase in the annealing time, the hardness grows until the moment of formation of partially coherent precipitates and the maximum hardness is achieved. During metallographic studies, the fracture surfaces are macro- and microscopically examined using a stereomicroscope and a scanning electron microscope. Due to comparison of the surface of fractures at different modes of heat treatment, it can be argued that the samples with the maximum hardness are characterized by a brittle fracture. The use of photogrammetric methods in SEM studies and EDX-analysis of fracture specimens permit to orient with high accuracy an investigated plane in space and promote to obtain a high quality and reliable result. In order to confirm the optimal conditions of heat treatment, it is recommended to carry out further mechanical and metallographic studies based on the results of preliminary tests. [ABSTRACT FROM AUTHOR]

The results of the investigations of structural and thermoelectric properties of thin composite films based on PbTe are given. The films of different thicknesses (10-150 nm) on glass, Al2O3 and silicon substrates were obtained by pulsed laser deposition of 1 × 10−4 Pa, and at different substrate temperatures (30°C, 200°C). The growth conditions leading to the films having different properties that could be controlled in a possibly wide range were identified. The parameters of the crystalline structure of thin films have been determined by X-ray diffractometry methods and high-energy electron diffraction methods. The surface morphology of thin PbTe composite films (initial growth stages) was investigated using a SEM scanning microscope. During the study of the morphology of the film surface, it was clearly visible that the contrasts with the main surface (matrix) of the film differ. This indicates a rather significant deviation from the stoichiometry in the process of the deposition of the films by the method of pulsed laser deposition. The temperature dependences of electrical conductivity, the Seebeck coefficient and the thermal power of thin composite films based on PbTe with inclusions have been investigated. With increasing temperature, Zeebek coefficient for the PbTe film hSb2Te3i increases in absolute value from ≈ 1 mV/K to values ≈ 11 mV/K, and the electrical conductivity decreases from σ ≈ 0.5 (Ohm·cm−1 to σ ≈ 0.08 (Ohm·cm−1 . For other films, the temperature characteristics of the similar parameters have the opposite character. The estimation of the value of thermoelectric parameters is made taking into account the dimensional effects in the processes of charge carrier transport, and the phenomenon of increase of the Seebeck coefficient at the content of Bi2Te3 is indicated. [ABSTRACT FROM AUTHOR]

The influence of the Cu2+dopant on the temperature evolution of the optical absorption edge in the region of phase transitions of [(CH3 )2CHNH3 ]4 Cd3Cl10 (IPACC) ferroelastoelectric crystals was investigated. The relative amount of Cu2+ with respect to Cd2+ in the samples of [[CH3 ]2CHNH3 ]4Cd3Cl10:Cu (IPACCC) was examined using EDX analysis available in the scanning electron microscope and was found to be 0.6-0.1 %. The performed investigations ascertained a noticeable influence of the doping with Cu2+ ions on the electron- (exciton-) phonon interaction and respectively on the shape and temperature evolution of the optical absorption edge of IPACC crystals. It has been found that the characteristic parameters of the empiric Urbach's rule show anomalous behaviour at the phase transition point T2 = 293 K in IPACCC. It was shown that the low energy tail of the charge transfer band in this crystal is formed with the participation of internal vibrations of the metal-halogen complex. On the other hand, the low energy tail of the fundamental edge for both IPACC and IPACCC is formed with the participation of the internal vibrations of the metal-halogen complex or skeletal (or translational) vibration of IPA cation. [ABSTRACT FROM AUTHOR]

By the methods of high-resolution raster electronic microscopy (SEM), it is set that addition of carbon nanotubes (CNTs) to PTFE causes a change morphology: porosity, presence of polycrystalline fibrillar lamellas, friability of packing of elements of structure, adhesion of filler, with a matrix is low, a transitional layer is poorly expressed. Coefficient of friction for samples with a different percentage CNTs differs more than on 70%. Intensity of the linear wear down diminishes for all of composites of PTFE/CNT with content 1,0;, 2,5 and 5,0 % CNT in ~ 6, 17 and 65 times from an initial value accordingly. [ABSTRACT FROM AUTHOR]

We study the influence of compacting pressure, sintering temperature and composition of iron-based composite materials doped by self-fluxing alloys in the quantity of 10-30 % vol. on the structure, density and hardness. We employ the optical microscope MIM-8M and scanning electron microscope REM-106 to study the structure of materials. Specifically, the hardness testing machine TK-2M is used to conduct hardness testing. We uncover that pressing and sintering conditions, as well as the composition impact density and hardness of materials. Impregnating allows reaching maximum value of materials density during sintering. Finally, we reveal that it is possible to obtain materials with specified structure and properties, as well as certain performance by changing the composition of basic materials and conditions for obtaining products. [ABSTRACT FROM AUTHOR]