Possibilities of usage of polymer materials are expanded considerably as a result of the addition of nanocarbon particles (carbon nanotubes, graphene, graphene oxide, and nanostructured graphite). The article contains the consideration of several examples of producing and practical applications of polymer-based composites doped with nanocarbon particles. Such particles possess high electric and thermal conductivity; therefore, the usage of nanocarbon additives permits one to obtain polymer-based composite materials with enhanced transport characteristics. Polymers doped with carbon nanoparticles exhibit percolation conduction so that the charge transport proceeds by a limited number of percolation paths formed by contacting particles. Imperfection of contacts determines the non-linear character of the conduction of such composites: the resistance decreases with the applied voltage increase. The thermal conductivity of nanocarbon particles exceeds that for polymers by 4–5 orders of magnitude; therefore, even a small additive of nanocarbon (on the level of several percent) permits one to get a polymer material with enhanced thermal conductivity. Nanocarbon-doped composites find application particularly as phase change materials, which are able to accumulate and release considerable thermal energy as a result of the phase transition. One more direction of the usage of nanocarbon-doped composites relates to the development of the optical sensor on the basis of carbon nanoparticles. In this device, amplification of the Raman signal, bringing information on the chemical composition and structural characteristics of an object, is reached as a result of the interaction of electromagnetic radiation with plasmon oscillations of conducting nanoparticles.

The arrangement of a water thermal accumulator (WTA) containing phase change materials (PCM) is presented and analyzed. The hot or cool water is used as a working body. The accumulator contains two concentric cylindrical tubes. The inner tube is used for hot or cool water flowing, while the volume between the inner and outer tubes is filled with PCM. The thermal energy in the accumulator is stored as a result of flowing the hot water through the inner tube due to the phase transition in PCM. This accumulated energy can be extracted from PCM as a result of flowing the cool water through the inner tube. For the enhancement of the thermal conduction coefficient, the PCM is doped with the nanocarbon particles having a thermal conductivity coefficient exceeding that of PCM by 4–5 orders of magnitude. The thermal balance of the accumulator is calculated on the basis of the solution of the time-dependent heat conduction equation by taking into account the heat absorbed and released as a result of the phase transition as well as the convection thermal exchange in the melted PCM. The calculation results determine the interconnection between the thermal conductivity of PCM and the characteristic time of thermal exchange between PCM and the working body. The calculations indicate that the characteristic thermal exchange time decreases as the thermal conduction coefficient enhances, so that the dependence becomes close to saturation at the thermal conductivity coefficient of about 5 W/m K. Such a coefficient can be reached by doping the paraffin-based PCM with a reduced graphene oxide at a content of about 2% (weight).

X-ray photoelectron emission spectra of thermally reduced graphene oxide samples and carbon nanotubes (CNTs) with various oxidation degrees are presented in this paper. A method for the reconstruction of differential electron inelastic scattering cross sections from the energy loss spectra of photoelectrons is described and discussed. The analysis of the part of the characteristic photoelectron energy loss spectrum adjacent to the C1 peak indicated a considerable influence of the thermal reduction of graphene oxide on the electron properties of the samples obtained. On the contrary, the oxidation of CNTs by refluxing in a concentrated HNO3 solution does not change the free electron excitation spectrum.

Уважаемые коллеги!Благодарим Вас за проявленный интерес к Четвертой российской конференции «Графен: молекула и 2D кристалл» и желание принять участие в её работе.Конференция проходит в научно-образовательном центре города Новосибирска -Академгородке.Мероприятие посвящено актуальным направлениям исследований и разработок в области углеродных и низкоразмерных материалов.Проведение конференции поможет координации усилий ученых в решении современных проблем материаловедения и привлечению молодых исследователей для решения актуальных научных задач.Оргкомитет выражает особую благодарность НГУ, Центру компетенций НТИ «Моделирование и разработка новых функциональных материалов с заданными свойствами», компаниям «Диаэм», «НТ-МДТ Спектрум Инструментс» и корпорации "Графеновая Долина" за финансовую поддержку и журналам Аналитика, Наноиндустрия и РЭНСИТ за информационную поддержку.Искренне надеемся, что пребывание в Новосибирском Академгородке и в стенах Новосибирского государственного университета оставит множество положительных эмоций и

The concept of a water thermal accumulator based on phase-change materials (PCMs) has been proposed and analyzed. In such a system, energy accumulation (release) occurs due to a phase transition in PCMs, and water is used as a working fluid. The thermal accumulator consists of identical modules, the number of which determined by the quantity of accumulated energy. Each module represents a double concentric tube, in which the inner cavity is filled with flowing water and the outer cavity is filled with PCMs. The PCM used is paraffin wax, which has a specific melting enthalpy of 216 J/g. To increase the PCM heat conductivity coefficient, an additive of thermally reduced graphene oxide is used. The passage of hot water through the inner tube results in the melting of paraffin wax, which accumulates the thermal energy corresponding to the melting enthalpy. This energy is recovered when cold water is passed through the system containing the melted paraffin wax and heated as a result of paraffin wax solidification. Some estimates of thermal accumulator regimes and the results of calculating the unsteady longitudinal and transversal temperature distributions at different time moments are given.

Phase changing materials (PCM) can accumulate and release a great quantity of energy at changing the temperature in result of the phase transition. This permits one to use PCMs as a basis of thermal accumulators storing the thermal energy at elevated temperatures and releasing it at lowering the temperature below the phase transition point. Worldwide usage of PCMs in building technology and other fields is hindered by a rather low thermal conductivity coefficient of the most PCMs which makes the response of the relevant thermal accumulators too slow and limits the possibilities of application of such devices. This drawback can be overcame through doping a PCM with particles having high thermal conduction coefficient. The present article contains results of experimental and theoretical investigations of heat propagation in PCM doped with carbon nanotubes the thermal conduction coefficient of which exceeds that of the most PCM by 4 – 5 orders of magnitude. Paraffin П-2 have been used as PCM. The experiments performed demonstrate a 2 – 3 times enhancement of thermal conductivity and 16 orders of magnitude enhancement of the electric conductivity because of doping paraffin with 10% multi-walled nanotubes. The propagation of both heat and electric current has a percolation character, so that nanotubes form conductive paths at exceeding some concentration of the dopant. The heat propagation process was modelled through the solution of the non-stationary heat conduction equation with taking into account the sorption of heat due to the phase transition. The calculations performed for composite materials with the varied thermal characteristics of a material imply that the characteristic heating time is proportional to the value of the melting enthalpy and inversely proportional to the value of the heat conduction coefficient.

Samples of thermally reduced graphene oxide are studied using differential cross sections for photoelectron inelastic energy losses. We compare different procedures for recovering cross sections from the photoelectron energy spectra resulting from multiple inelastic scattering. It is shown that the cross section for inelastic energy losses (which uniquely characterizes allotropes of carbon) in the sample containing the minimal amount of carbon oxides corresponds the best to pyrolytic graphite.

The dynamics of X-ray photoelectron emission spectra is studied in the region of the 1s carbon line with increasing treatment temperature for graphene-oxide samples. It is established that, as the degree of oxide reduction increases, the role of the mechanism related to energy losses for the excitation of π-plasmon oscillations produced in the presence of sp2 bonds in the carbon sample increases. Spectral analysis shows that the π-plasmon peak is manifested in the spectra of samples annealed at temperatures exceeding 200°C. When determining the differential cross sections for inelastic electron scattering, the difference between the energy losses in the surface sample layers and the homogeneous bulk located far from the surface is taken into account. The obtained spectra are compared with those of multilayer graphene and pyrolytic graphite. It is shown that the analysis of graphene oxide using X-ray photoelectron spectroscopy gives a picture on a nanometer scale. The obtained data can differ noticeably from the Raman spectroscopy data corresponding to the millimeter scale.

Исследуются образцы термически восстановленного оксида графена на основе анализа дифференциальных сечений неупругих потерь энергии фотоэлектронов. Сравниваются различные методики восстановления этих сечений из энергетического спектра фотоэлектронов, складывающегося в результате процессов многократного неупругого рассеяния. Показано, что в ситуации, когда в образце присутствует минимальное количество оксидов углерода, сечение неупругих потерь энергии, однозначно характеризующее аллотропную разновидность углерода, наиболее соответствует пиролитическому графиту.

The results of the analysis of carbon-containing materials are presented based on an analysis of the peaks of X-ray photoelectron spectroscopy (XPS) formed by the electrons leaving the analyzed sample in a vacuum without energy loss (peak shape analysis, PSA) and based on the interpretation of the widest possible area of energy loss adjacent to the photoelectron spectroscopy (PES) peak. It is shown that the PES analysis of diamond-like materials containing alloying additives, the concentration of which is comparable with the concentration of carbon, is not effective. The PES analysis of graphene oxide samples that were heat-treated to remove oxygen gave detailed information about the laws of the energy loss of photoelectrons emitted from the 1 s level, which determines the allotropic variety of carbon.

Carbon nanocomposites present a new class of nanomaterials in which conducting carbon nanoparticles are a small additive to a non-conducting matrix. A typical example of such composites is a polymer matrix doped with carbon nanotubes (CNT). Due to a high aspect ratio of CNTs, inserting rather low quantity of nanotubes (on the level of 0.01%) results in the percolation transition, which causes the enhancement in the conductivity of the material by 10–12 orders of magnitude. Another type of nanocarbon composite is a film produced as a result of reduction of graphene oxide (GO). Such a film is consisted of GO fragments whose conductivity is determined by the degree of reduction. A distinctive peculiarity of both types of nanocomposites relates to the dependence of the conductivity of those materials on the applied voltage. Such a behavior is caused by a non-ideal contact between neighboring carbon nanoparticles incorporated into the composite. The resistance of such a contact depends sharply on the electrical field strength and therefore on the distance between neighboring nanoparticles. Experiments demonstrating non-linear, non-Ohmic behavior of both above-mentioned types of carbon nanocomposites are considered in the present article. There has been a model description presented of such a behavior based on the quasi-classical approach to the problem of electron tunneling through the barrier formed by the electric field. The calculation results correspond qualitatively to the available experimental data.

Abstract Nanocarbon composites present a new type of nanomaterials consisted of electric conducting carbon nanoparticles and a non-conducting matrix. A typical example of such composites is a polymer matrix doped with carbon nanotubes (CNT). Due to a high aspect ratio of nanotubes insertion of very small quantity of CNT (on the level of 0.01%) promotes the percolation transition resulting in an enhancement of the conductivity of the material by 10–12 orders of magnitude. Another type of nanocarbon composite is a film consisted of partially reduced graphene oxide (GO) produced as a result of thermal reduction of graphite oxide material. Distinctive peculiarity of both types of nanocomposites relates to the dependence of the specific resistivity of the materials on the applied voltage. Such a behavior is caused by non-ideal contacts between neighboring carbon particles involving into the composite. The resistance of this contact depends drastically on the intra-contact field, which promotes the dependence of the material resistivity on the applied voltage. The model description of such a non-linear dependence has been presented. The calculation results are compared with both literature data and the measured data obtained for reduced GO thermally treated at various temperatures.

The metal surface modification by carbon nanostructures followed by high intense treatment has been realized. As carbon nanostructures were used: carbon soot formed in an arc discharge with graphite electrodes remained after extraction of fullerenes; fullerene C60; partially reduced graphene oxide. An intense pulsed laser and electron beam accelerator were used as high intense energy sources. Measurements performed indicate that the above described processing of the steel surface results in a considerable enhancement of the microhardness (up to 800%) and a notable decrease (up to 50%) in the friction coefficient. The degree of reinforcement depends on both the type of nanocarbon and the source of energy. The maximum effect of reinforcement is reached for fullerene C60 coverage and laser irradiation. The dependence of the microhardness of the treated surface on the irradiation energy has a non-monotone character reaching the maximum value of about 200 J/cm 2 at the laser irradiation and 400 J/cm 2 at the e-beam irradiation.

The effect whereby a steel surface is modified by its covering with a nanocarbon material followed by fast electron- or laser-beam irradiation is studied. The initial material is low-carbon steel. Soot produced via the thermal sputtering of graphite electrodes in an electric arc with the subsequent extraction of fullerenes is used as the nanocarbon coating. Due to the fact that nanocarbon-coated samples are irradiated with a 60-keV electron beam, the material microhardness enhances considerably. The dependence between the microhardness and the irradiation energy is nonmonotonic and reaches its maximum (about 600 ± 20 HV) under the condition that the electron-irradiation energy is 460 J/cm2 and the intensity is 1.53 kW/cm2. This corresponds to a fourfold increase in the microhardness. Electron-beam irradiation of the treated surface is accompanied by a 1.5–2-fold decrease in the friction coefficient. Experimental results are compared with data obtained under laser irradiation of the nanocarbon-coated steel surface.

The effect of Raman scattering (RLS) signal amplification by carbon nanotubes (CNTs) was studied. Single-layered nanotubes were synthesized by the chemical vapor deposition (CVD) method using methane as a carbon-containing gas. The object of study used was water, the Raman spectrum of which is rather well known. Amplification of the Raman scattering signal by several hundred percent was attained in our work. The maximum amplification of a Raman scattering signal was shown to be achieved at an optimal density of nanotubes on a substrate. This effect was due to the scattering and screening of plasmons excited in CNTs by neighboring nanotubes. The amplification mechanism and the possibilities of optimization for this effect were discussed on the basis of the theory of plasmon resonance in carbon nanotubes.