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Vol 478, No 2 (2018)
- Year: 2018
- Articles: 5
- URL: https://journals.rcsi.science/0012-5016/issue/view/9238
Physical Chemistry
On the Mechanism of the Initial Stage of Titanium–Carbon Interaction
Abstract
High-speed micro video recording and electron and atomic force microscopy have been used to obtain new experimental data at the initial stage of the titanium melt spreading along a carbon material (oriented pyrolytic graphite) and the formation of a reaction product. It has been shown that the melt spreading at the initial stages takes place along a framework of flat submicron crystalline grains of TiC with an open porosity. The grains form an island structure at the reagent contact boundary with gaps of about 100 nm in width between them, and these gaps are connected to each other to give a continuous network of channels along which the melt spreads. Thus, at the initial stage of the interaction, despite the formation of a solid product, direct contact of the reagents is retained, which ensures a high process speed.
27-30
Rocket Engine with Continuous Detonation Combustion of the Natural Gas–Oxygen Propellant System
Abstract
In a demonstrator of a detonation rocket engine (DRE) using the natural gas–oxygen propellant system, a high (270 s) specific impulse at sea level at a low (32 atm) mean combustor pressure was experimentally obtained for the first time. Comparison of these characteristics with the respective ones (263 s and 61 atm) of the well-known Russian RD 170-A liquid-propellant rocket engine using deflagration combustion of the kerosene–oxygen propellant system showed that the specific impulse at sea level in the DRE is close to that in the deflagration-combustion engine but is produced at half as high a mean combustor pressure. This indicates that the energy efficiency of detonation combustion exceeds that of deflagration combustion, and that there is room to improve the weight–size characteristics of the turbopump unit in the DRE.
31-34
Cathode Materials for Hybrid Supercapacitors Based on Ozonated Reduced Graphene Oxide
Abstract
A carbon material capable of reversible electrochemical oxidation and reduction with relatively high electrical conductivity was prepared by ozonation of thermally reduced graphene oxide. The specific discharge energy for such materials used in lithium ion electrochemical cell cathodes with non-aqueous electrolytes (LP-71) can reach 540 W h/kg at 40 mA/g current, while the average specific discharge power is 11.5 kW/kg at 5 A/g current. The specific charge after 2500 charge/discharge cycles at 5 A/g current was at a level of 93% of the initial value. The obtained materials appear promising for the design of new electricity storage systems.
35-38
Formation of Dissipative Structures in an Amorphous Film
Abstract
The formation of nanothin spatial dissipative structures (SDSs) of hexagonal selenium with elastic rotational curvature of the lattice about [001] in an amorphous film was considered. It was established that nanothin SDSs form in thermal gradient treatment of an amorphous film by one-side heating of its lower surface at T = 453 K. The state of pseudo-single crystal, which precedes the formation of a nanothin SDS in an amorphous film, is a state with a high concentration of vacancies. Under the action of the temperature difference ΔT, vacancies and selenium atoms undergo thermal diffusion in the direction perpendicular to the surface of the pseudo-single crystal. It was shown that, when ΔT reaches critical values, there is a transition from the structure of a pseudo-single crystal to the structure of a rhombic nanothin SDS of hexagonal selenium. The heat flux through the nanothin SDS in the direction perpendicular to its surface ensures the entropy export to the environment. After the thermal gradient treatment of the amorphous film, the nanothin SDS is quenched by cooling it in air; in this process, there is quenching of nonequilibrium structural defects—atoms and vacancies displaced from equilibrium positions. The quenching makes the nanothin SDS stable. The formation of nanothin SDSs of hexagonal selenium with elastic rotational curvature of the lattice about [001] in an amorphous film occurs under conditions satisfying the theory of the formation of dissipative structures.
39-41
Stability Analysis of YbFe2O4 under Low Partial Oxygen Pressure
Abstract
YbFe2O4 has been synthesized for the first time at 1090°C under reduced oxygen pressure. A distinctive feature of the synthesis is the use of a gas mixture consisting of an inert gas and a controlled amount of oxygen. Static method in combination with X-ray diffraction methods have been used to determine the thermal stability ranges for YbFe2O4. On the basis of the P–T–X data obtained, the Yb–Fe–O system diagram has been supplemented with low-temperature fragments, which is important for selecting the conditions for synthesis and operation of the compound.
42-46