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Vol 470, No 2 (2016)
- Year: 2016
- Articles: 8
- URL: https://journals.rcsi.science/0012-5016/issue/view/9201
Physical Chemistry
Nanostructured ZnS with random close-packed structure: Synthesis, formation rate, and crystal structure study
Abstract
The chemical precipitation of nanocrystalline ZnS from aqueous alkaline solutions containing zinc ethylenediamine complex salt Zn(En)2+ and thiocarbonic acid diamide N2H4CS was studied in the course of time in terms of formal chemical kinetics. The ZnS formation rate was found to depend on the concentration of precipitation agent (N2H4CS) and to decrease with increasing the ligand (ethylenediamine) concentration, whereas the pH dependence is less pronounced. The size of resulting ZnS nanoparticles does not exceed 5 nm, and their crystal structure was identified as a random close packed structure.
141-144
SHS metallurgy of high-entropy transition metal alloys
Abstract
The first positive experience in synthesis of cast high-entropy alloys in the combustion mode, referred to as SHS metallurgy (SHS is self-propagating high-temperature synthesis) has been reported. Analysis of the data obtained enables the conclusion that the one-stage SHS method is promising for the production of cast metal materials using a new principle of formation of high-entropy polymetallic alloys.
145-149
Modeling of Low-temperature oxidation and combustion of droplets
Abstract
Key features of radiation extinguishing of spherical hot flame around a single droplet with its subsequent low-temperature oxidation and combustion under microgravity conditions—a phenomenon discovered in experiments onboard the International Space Station—have been reproduced using the mathematical model of droplet combustion and detailed kinetic mechanism of n-heptane oxidation and combustion. It has been demonstrated that experimentally observed repeated temperature flashes were blue flame flashes, and their duration was determined by the hydrogen peroxide decomposition time. In addition to this phenomenon, calculations predict the existence of new modes of low-temperature oxidation and combustion of droplets without the hot flame stage. In such modes, the basic reaction is concentrated very close to the droplet surface, and fuel vapor reacts in it only partially.
150-153
Stabilization of TiO2–Co3O4 thin films on a glass fiber material by introduction of silica into the matrix
Abstract
The TiO2–Co3O4–SiO2 oxide system supported on glass fiber was synthesized and studied. The oxide layers attached to the glass fiber surface have a porous structure. Characteristics of thin-film coatings on the glass fiber substrate (oxide layer phase composition and adhesion to the glass fiber surface) depend on the silica concentration. The obtained materials are catalytically active towards the exhaustive oxidation of propane.
154-157
Thin films of palladium oxide for gas sensors
Abstract
Thin films of PdO obtained by thermal oxidation of Pd films in air in the temperature range of 240–800°C were characterized using fast electron diffraction, transmission electron microscopy, and optical spectroscopy. The PdO films were found to be non-stoichiometric. With increasing oxidation temperature, the deviation of the PdO film composition from the stoichiometric component ratio becomes less pronounced. The resistivity response of PdO films to the presence of ozone in air was studied for the first time and good prospects for using this material for gas sensors are demonstrated.
158-161
162-164
165-167
Regime of superhigh reactivity of the YBa2Cu3O6 + δ superconductor toward the components of air
Abstract
Physicochemical features of the YBa2Cu3O6 + δ superconductor synthesized via ceramic route and subjected to a kind of modification by long-term exposure to an atmosphere with low pH2O have been studied by X-ray diffraction, thermal analysis, and magnetometry. The resulting material had a high degree of saturation with air components at room temperature and 30% humidity, up to 1.5 wt % in 30 days, which is not inherent in YBa2Cu3O6 + δ.
168-172