TiB2-SiC ceramics with multi-wall carbon nanotubes (MW-CNT) were reactively hot pressed at 1800°C and 30 MPa. Carbon nanotubes survived the process and could be clearly observed in the sintered ceramics. The in-situ exothermic reactions between TiC, B4C and Si accelerated the densification and produced nonporous TiB2-SiC ultrahigh-temperature ceramics within one minute at 1800 °C. Although the toughness of the ceramic was not significantly affected by the CNT addition, remaining around 6 MPa•m 1/2 , the CNT presence resulted in a substantial improvement in TiB2-SiC thermal shock resistance. The Vickers hardness decreased from 27GPa for the CNT-free matrix to 21GPa for ceramic with maximum CNT content (7.4 wt.%).

Multi-walled carbon nanotubes have been synthesized by Aerosol-Chemical Vapor Deposition method. Carbon nanotubes firstly have been used as filler in affordable and prevalent natural Azerbaijani bentonite clays for fabrication electroconductive ceramic composites. In this paper, multi-walled carbon nanotubes/natural Azerbaijani bentonite ceramic composites were prepared by two-factor mechanical method and followed by calcination at 1050℃ in an inert atmosphere. The ceramic composites were characterized by scanning electron microscope, atomic force microscope, X-ray diffraction and thermogravimetric-differential-thermal analysis. X-ray diffraction analysis confirmed the presence of two principal components – multi-walled carbon nanotube and bentonite in composites. From the thermogravimetric-differential-thermal data, it was revealed that multi-walled carbon nanotube/ bentonite ceramic composites demonstrate thermo-oxidative stability up to 580–640℃. Scanning electron microscope images demonstrated a sufficiently high dispersibility of carbon nanotubes and satisfactory homogeneity in the composites. Experimental results demonstrated that by increasing the mass fraction of multi-walled carbon nanotubes from 1% to 8% in multi-walled carbon nanotube/bentonite ceramic composites, the electrical conductivity enhances substantially. The enhancement of electrical conductivity of the composites explained the mass fraction of multi-walled carbon nanotubes, as well as the uniform dispersion of multi-walled carbon nanotubes in the bentonite clays. Compared with other 8% multi-walled carbon nanotubes/bentonite ceramic composites, the electrical conductivity of heptane-multi-walled carbon nanotube/Gobu bentonite (σ = 397 S·m−1) and heptane-multi-walled carbon nanotubes/Atyali (σ = 305 S·m−1) composites is 2–5 times higher than the conductivity of composites obtained with cyclohexane carbon nanotubes- cyclohexane-multi-walled carbon nanotube/Atyali (σ = 78 S·m−1), cyclohexane-multi-walled carbon nanotube/Gobu (σ = 111,5 S·m−1). These results can be explained with the structure, the number of layers, purity and diameter distribution, as well as the type and amount of defects in internal and external layers of Hep-multi-walled carbon nanotubes which cause better dispersion in bentonite clays. Due to the high conductivity and high temperature stability, these composites can be used as promising material for fabrication heating elements, electrodes, substrates for microelectronic devices, etc.

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The article presents simple kinetic approaches to study the effect of multi-walled carbon nanotubes (MWCNTs) additives on the aerobic oxidation of hydrocarbons and to propose real acceptable mechanisms of the process. The aerobic liquid phase low-temperature oxidation of ethylbenzene conducted in the presence of multi-walled carbon nanotubes has been used as a model pattern. Kinetic analysis established the catalytic action associated with the presence of the iron compounds in inner channels of MWCNTs. These compounds are identified as ferric carbides provoking decomposition of the ethylbenzene hydroperoxide and thereby suppressing the competitive route of alky-peroxide radicals addition to the nanocarbon cage. Thus the reaction finally proceeds in the autocatalytic mode.Contradictory conclusions on the effect of CNTs on the oxidation chain processes existing in the literature are associated with the lack of control over nature and content of metal impurities in channels of nanotubes.

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In this paper, polyurethane/MW-CNT, silicone/MW-CNT, and epoxy/MW-CNT nanocomposites were prepared, and their electrical and gas-sensitive properties were investigated. The aerosol-assisted chemical vapor deposition method was used to synthesize MW-CNTs from acetonitrile as a carbon source. These nanocomposites were prepared by an irreversible dispersion method that was developed by our group. SEM analysis results proved that smooth-surfaced, less defective MW-CNTs with 30–60 nm diameter and 60-50 μm length were synthesized successfully. The electrical conductivity of the prepared nanocomposites reveals the correspondence between the degree of uniformity of distribution of MW-CNTs inside polymers and the electrical conductivity of nanocomposites. The electrical conductivity graphs for Epoxy/x MW-CNTs and PU/x MW-CNTs nanocomposites have the same shape, and there is a sharp increase in electrical conductivity from 4% of MW-CNTs, but the values are different: Epoxy/x MW-CNTs (x = 8%) (1000 S/m) and PU/x MW-CNTs (x = 8%) (24.39 S/m). The electrical conductivity graph of silicone/x MW-CNT has a different shape, and percolation began at 2% of MW-CNT and increased sharply till 4%, then there was observed saturation. These results proved that the nanocomposite’s electrical conductivity properties depend on the polymer matrix nature. Simultaneously, the gas-sensitive properties of these nanocomposites were discovered. Thus, it was determined that the highest resistance change was observed for PVAc/x MW-CNT (x = 4%) nanocomposite under CO gas. Except for PVAl/x-MW-CNT (x = 4%), other nanocomposites show a gas-sensitive effect depending on gas types. Moreover, the resistance of all nanocomposites decreases with increasing temperature (from 20 to 120°C) and their behavior as semiconductors. However, the shapes of the graphs of the resistance depending on temperature are different depending on the nanocomposites, and their values are also different, some of them in the Om, KOm, and MOm ranges.

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