405 research outputs found
On Malleability of Rhenium at Room Temperature
The problem of the malleability of rhenium at room temperature is discussed. It has shown that rhenium manufactured by the mean of the electron beam melting is able to the mechanical treatment by rolling at room temperature. The primary condition for mechanical treatment is the minor share of the tensile stress in the processing scheme. It suppresses the grain boundary sliding in a coarse-grained workpiece of this refractory HCP-metal. © Published under licence by IOP Publishing Ltd.The Russian Science Foundation supports this work (№ 18-19-00217)
Pressure effect on magnetic susceptibility of LaCoO
The effect of pressure on magnetic properties of LaCoO is studied
experimentally and theoretically. The pressure dependence of magnetic
susceptibility of LaCoO is obtained by precise measurements of
as a function of the hydrostatic pressure up to 2 kbar in the
temperature range from 78 K to 300 K. A pronounced magnitude of the pressure
effect is found to be negative in sign and strongly temperature dependent. The
obtained experimental data are analysed by using a two-level model and DFT+U
calculations of the electronic structure of LaCoO. In particular, the fixed
spin moment method was employed to obtain a volume dependence of the total
energy difference between the low spin and the intermediate spin
states of LaCoO. Analysis of the obtained experimental dependence
within the two-level model, as well as our DFT+U calculations, have revealed
the anomalous large decrease in the energy difference with increasing
of the unit cell volume. This effect, taking into account a thermal expansion,
can be responsible for the temperatures dependence of , predicting its
vanishing near room temperature.Comment: 7 pages, 9 figure
Helicoidal instability of a scroll vortex in three-dimensional reaction-diffusion systems
We study the dynamics of scroll vortices in excitable reaction-diffusion
systems analytically and numerically. We demonstrate that intrinsic
three-dimensional instability of a straight scroll leads to the formation of
helicoidal structures. This behavior originates from the competition between
the scroll curvature and unstable core dynamics. We show that the obtained
instability persists even beyond the meander core instability of
two-dimensional spiral wave.Comment: 4 pages, 5 figures, revte
On deformation behaviour of polycrystalline iridium at room temperature
Deformation and fracture behaviour of cold drawing iridium wire under tension at room temperature is examined. High purity polycrystalline iridium was manufactured using pyrometallurgical technology. During the initial stage of cold rolling, iridium wire has its usual grain structure and exhibits brittle deformation behaviour: Poor plasticity and brittle transgranular fracture (BTF). However, the wire begins demonstrating high plasticity including necking in spite of the brittle fracture mode when the lamellar structure has been formed in iridium during cold drawing. © 2021 Johnson Matthey Public Limited Company. All rights reserved.The Russian Science Foundation supports this research project (#18-19-00217)
- …