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Vol 488, No 2 (2019)
- Year: 2019
- Articles: 5
- URL: https://journals.rcsi.science/0012-5016/issue/view/9274
Physical Chemistry
Effect of the Density of Iron Nanopowders on the Parameters of Their Ignition during Heating in Air
Abstract
The ignition of iron nanopowders of bulk density and those compacted to a relative density of 0.3–0.5 during heating in air has been studied. The ignition temperature of the compacted samples is independent of the heating rate and is 100–115°C. The durations of the active stages—ignition and filtration combustion—under identical heating mode depend on the sample density, which makes it possible to develop methods to store iron nanopowders in the compacted state.
143-145
Effect of Interaction of Bacterial Cellulose with Gold Nanoparticles Obtained by Metal Vapor Synthesis
Abstract
A promising method for preparation of new functional nanocomposite materials based on bacterial cellulose and Au nanoparticles was proposed for the first time. The Au nanoparticles were obtained by biocompatible and environmentally friendly metal vapor synthesis. The structure and composition of the surface of composite films were studied by XPS, SEM, and IR spectroscopy. Gold nanoparticles were found to efficiently chemisorb nanofibrils of bacterial cellulose, which gave nanoparticles of approximately 25 nm in size with a “metal core–hydrocarbon shell” structure.
146-150
Direct Observation of Processes at Particle-to-Particle Contacts during Electric Pulse Consolidation of a Titanium Powder
Abstract
Direct high-speed micro video recording data proved the existence of highly overheated zones at contacts of powder particles through which electric current pulses about 1 ms long were sent. The overheating might exceed 1600 K and could give rise to liquid-phase sintering necks, the sizes of which correlated well with the sizes of the overheated zones. Temperature field microheterogeneities during electric pulse heating of the powder medium gave an insight into unusually high rates of consolidation of powder materials during spark plasma sintering.
151-153
Template Synthesis of Graphene
Abstract
A series of carbon-mineral composites with the carbon loading varying from 1.5 to 14.2 wt % has been synthesized by MgO carbonization in 1,3-butadiene at 600°C. The synthesized carbon-mineral composites have been studied by ESR, X-ray powder diffraction, and transmission electron microscopy. ESR has demonstrated that the MgO surface is completely covered with carbon after depositing 8–10 wt % C. MgO from the composite was dissolved by treatment with hydrochloric acid. The surface area of the carbon samples obtained after the acid treatment has been studied by thermal desorption of argon. It has been shown that the synthesized carbon material consists of a few graphene layers. The specific surface area of the synthesized graphene passes through a maximum of about 1800–1900 m2/g for samples obtained from C–MgO composites containing 8–10 wt % C.
154-157
Nanothin Spatial Dissipative Structures with Rotational Curving of the Grid around Three Mutually Perpendicular Directions
Abstract
Nanothin spatial dissipative structures (SDSs) produced by thermal gradient processing of an amorphous selenium film by means of one-sided heating of its lower surface at T = 413 K have been studied by transmission electron microscopy and microdiffraction. It has been established that the resulting nanothin SDSs of hexagonal selenium possess a specific curved habit and a nonlinear fan-shaped system of bending contours in their electron-microscopic image; the lattice of nanothin SDSs undergoes elastic-plastic rotational curvature around three mutually perpendicular directions; the lattice rotation angles of nanothin SDSs of hexagonal selenium reach 25° around [001], 32° around the direction perpendicular to [001] and lying in the plane of the amorphous film, and 35° around the direction perpendicular to the first two directions and not lying in the plane of the amorphous film.
158-160