In this work, the combustion process of chromium powder in the co-flow filtration mode was studied. The effect of nitrogen-containing gas flow rate on the nitridation of combustion products is shown. The effect of the amount of argon in the nitrogen–argon mixture on the burning rate and the burning temperature of the chromium powder is shown. It was found that an increase in the percentage of argon in the nitrogen–argon mixture can lead to the formation of an inverse combustion wave. The actual burning temperature is higher than adiabatic burning temperature in the co-flow filtration mode, thus the phenomenon of superadiabatic heating is observed. The phase composition of the obtained combustion products was studied. It was shown that the forced filtration mode allows for synthesizing non-stoichiometric Cr2N nitride.
This paper proposes a modified carbon-based concrete filler composition, which can potentially be used as a self-de-icing pavement. Carbon fibers (CNFs), graphene-like porous carbon (GLC), and a CNF/GLC composite were developed to reinforce concrete with the aim to improve its electrical conductivity and mechanical properties. The effect of the CNF and GLC loadings on the electrical conductivity of the filled concrete was evaluated in a climatic chamber at temperatures simulating water-freezing conditions on a concrete road. The results show that even a negligible loading (0.2 wt.%) of concrete with CNF/GLC results in a dramatic decrease in its resistance when compared to the same loadings for CNF and GLC added separately. Depending on the number of fillers, the temperature of the modified concrete samples reached up to +19.8 °C at low voltage (10 V) at −10 °C, demonstrating the perspective of their heat output for anti-icing applications. Additionally, this study shows that adding 2.0 wt.% of the CNF/GLC composite to the concrete improves its compressive strength by 33.93% compared to the unmodified concrete.
Supercapacitors are one of the promising devices for the accumulation and storage of electrical energy. The purpose of this study is to develop a synthesis and modification method of carbon material to improve the electrochemical characteristics of a supercapacitor. In the proposed study, by varying the sequence and parameters of the processes of carbonization, mechanoactivation and thermochemical activation, the conditions for obtaining nanoporous carbon with a specific surface area of 2200 (±50) m2/g from walnut shells (WSs) are optimized. In addition, to increase the electrochemical efficiency of the electrode material, the resulting nanoporous carbon was modified with nickel oxide (NiO) nanoparticles by the thermochemical method. It is shown that the modification with nickel oxide nanoparticles makes it possible to increase the specific capacitance of the supercapacitor electrode by 16% compared to the original unmodified nanoporous carbon material.
In this work, we considered an original setup that allows us to study the combustion of metal powders in a co-flow gas stream, and also presents the results of experimental studies on the combustion of chromium powder in a confined nitrogen-containing gas stream. This method has high energy efficiency and allows to get nitrides without the use of high pressures. The study of chromium combustion is justified by its high melting point at a relatively low exothermicity, which eliminates the influence of melting of the initial powder and synthesis products on the filtration process. This article presents the results of combustion of chromium powder with particle size δ = 63÷80 µm and δ = 500÷1000 μm. X-ray phase studies of the obtained powders were carried out. The effect of nitrogen-containing gas consumption on the degree of nitriding of combustion products is shown. It is established that the forced filtration mode allows the synthesis of non-stoichiometric chromium nitride Cr2N. The nitrogen content in the obtained Cr2N samples reached 9.6%.
The combustion of the titanium and chromium powders in the co-current filtration mode was considered. We considered an original equipment that allows us to study the combustion of metal powders in a co-flow gas stream. It was demonstrated that the proportion of argon in a binary gas mixture has a greater influence on the burning temperature of titanium powder than the specific flow rate of the gas mixture. It was found that the actual burning temperature of chromium in the forced filtration mode is higher than the adiabatic temperature and the phenomenon of superadiabatic heating takes place. This method has high energy efficiency and allows you to get nitrides without the use of high pressures. It was found that co-current filtration promotes the formation of Cr2N nitride.
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