scholarly journals Topological phonons in oxide perovskites controlled by light

2020 ◽  
Vol 6 (46) ◽  
pp. eabd1618
Author(s):  
Bo Peng ◽  
Yuchen Hu ◽  
Shuichi Murakami ◽  
Tiantian Zhang ◽  
Bartomeu Monserrat
Keyword(s):  
Tetragonal Phase ◽  
Structural Phase ◽  
Thermal Fluctuations ◽  
Perovskite Oxides ◽  
Phase Changes ◽  
Nodal Lines ◽  
Rich Variety ◽  
External Conditions ◽  
Photoexcited Carrier ◽  
Physical Phenomena

Perovskite oxides exhibit a rich variety of structural phases hosting different physical phenomena that generate multiple technological applications. We find that topological phonons—nodal rings, nodal lines, and Weyl points—are ubiquitous in oxide perovskites in terms of structures (tetragonal, orthorhombic, and rhombohedral), compounds (BaTiO3, PbTiO3, and SrTiO3), and external conditions (photoexcitation, strain, and temperature). In particular, in the tetragonal phase of these compounds, all types of topological phonons can simultaneously emerge when stabilized by photoexcitation, whereas the tetragonal phase stabilized by thermal fluctuations only hosts a more limited set of topological phonon states. In addition, we find that the photoexcited carrier concentration can be used to tune the topological phonon states and induce topological transitions even without associated structural phase changes. Overall, we propose oxide perovskites as a versatile platform in which to study topological phonons and their manipulation with light.

scholarly journals Protective and strengthening coatings on reinforcing steels

2020 ◽  
Vol 96 (4) ◽  
pp. 39-46
Author(s):  
S.A. Vodennikov ◽  
◽  
V.O. Skachkov ◽  
O.S. Vodennikova ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Electrochemical Oxidation ◽  
Mechanical Characteristics ◽  
Aluminide Coating ◽  
Structural Phase ◽  
Phase Changes ◽  
Electrolytic Deposition ◽  
Reinforcing Steel ◽  
Aluminum Coatings

A conceptually new technology for the application of aluminum coatings on 18G2C steel by the electrolytically deposited NaF-NaCl - AlF3 ionic melt method has been developed. To solve the tasks set in the work, a set of experimental and computational research methods was used: metallographic analysis, energy dispersion microanalysis, mechanical tests, and calculation of the oxidation rate of samples. The mechanical characteristics of the samples of reinforcing steel were determined on a rupture machine FP-100 at an active capture rate of 2.5 mm / min. The relationship between the rates of electrochemical oxidation of the aluminide coating, its mechanical properties, with the distribution of aluminum in the depth of the samples and its phase composition have been determined. The increase of mechanical characteristics of samples from 18G2S steel with an aluminum covering in comparison with usual reinforcing steel is shown. The sequence of structural-phase changes of metal in the process of aluminide coating is determined and its influence on mechanical and corrosion resistance is determined. Experimental evaluation of the rate of oxidation of 18G2C steel samples with aluminum coating under the conditions of sulfuric acid electrolyte at an electric current of 11 to 18 A has been conducted. The developed technology of electrolytic deposition of aluminum has scientific and practical interest for the construction industry. The developed coating makes it possible to increase the mechanical properties of steel by almost 12% and to increase the corrosion resistance. Keywords: aluminum coatings, 18G2C steel, electrochemical oxidation, electrolytic deposition.

scholarly journals STRUCTURAL AND PHASE CHANGES OF THE SURFACE LAYERS OF HEATRESISTANT MULTICOMPONENT COATING OF ION-PLASMA COATING Ni-Cr-Al-Y AFTER MODIFICATION BY HIGH-CURRENT ELECTRON BEAMS MICROSECOND DURATION

2020 ◽  
Vol 17 (34) ◽  
pp. 459-468
Author(s):  
Oksana A BYTSENKO ◽  
Igor G STESHENKO ◽  
Vladimir A PANOV ◽  
Victor V TISHKOV ◽  
Alexey B MARKOV
Keyword(s):  
Electron Beams ◽  
Structural Phase ◽  
Plasma Coating ◽  
Phase Changes ◽  
High Current ◽  
Surface Layers ◽  
Heat Resistant ◽  
Ion Plasma ◽  
Current Electron ◽  
High Current Electron

The development of aerospace engineering and mechanical engineering directly depends on the development of new metal materials and advanced technologies. The problem of creating materials and their types of processing to increase the level of operational properties is relevant in connection with the complication and tightening of working conditions of modern technologies. One of the most important tasks of contemporary aircraft construction is to increase the operational properties of the surface layer. The purpose of the article is to elucidate the effect of high-current electron beams of microsecond duration on changes in the surface layers of the heat-resistant multicomponent ion-plasma coating Ni-Cr-Al-Y under various conditions. Using a complex of metallophysical research methods, the physicochemical and structural-phase states of the surface layer were studied before and after modification of the samples. These samples were coated with heat-resistant condensed ion-plasma coatings of three different compositions using nine high-current electron beams in 9 modes with different values of electron energy and number of pulses in the selected interval of electron energy. An analysis of the structural phase changes occurring during modification was carried out. Cylindrical samples of targets made of heat-resistant nickel alloy ZhS36 coated with ion-plasma condensed multicomponent coating SDP-2 + VSDP-16. These samples were used according to serial technology, both with subsequent modification using highcurrent electron beams and without modification. It was found that chromium in the initial state is unevenly distributed: chromium is present in the particles; the matrix is depleted in chromium. The research results can be useful for scientists to study the properties of heat-resistant multicomponent ion-plasma coatings Ni-Cr-Al-Y and the effect of high-current electron beams on it, as well as for the manufacture of more heat-resistant materials in aerospace engineering and mechanical engineering.

Structure and Crack Resistance of N-A-XTRA-70 Steel Joints Manufactured by Hybrid Laser-Arc Welding

2018 ◽  
Vol 927 ◽  
pp. 29-34 ◽  
Author(s):  
V. Pozniakov ◽  
L. Markashova ◽  
O. Berdnikova ◽  
T. Alekseienko ◽  
S. Zhdanov
Keyword(s):  
Crack Resistance ◽  
Welded Joints ◽  
Arc Welding ◽  
Structural Phase ◽  
Consumable Electrode ◽  
Phase Changes ◽  
External Loading ◽  
Hybrid Laser Arc Welding ◽  
Source Power ◽  
Scanning Electron

Crack resistance of welded joints is one of the most important indices of service reliability of critical designation structures. The purpose of the research is the establishment of the influence of technological modes, hybrid laser-arc welding of high strength steel NA-XTRA-70 on the formation of structure in the metal welded joints, as well as analysis of the influence of this structure on their crack resistances. For the experiments the laboratory setup has been developed on which the experiments were carried out in the technological scheme that provides the location of the consumable electrode arc at a certain distance in front of the laser beam in the welding direction. Nd: YAG-laser DY 044 of company ROFIN (Germany) was a laser radiation source. Power for consumable electrode arc was carried out by welding generator PSG-500. Investigations of structural-phase changes in weld metal and HAZ were carried out by means of optical microscopy (optical microscope Versamet-2 and Neophot-32), microhardness was measured using M-400 gage of Leco company at 0.98N loading. Fractographic investigations were carried out by scanning electron microscopy (scanning electron microscope SEM-515 of PHILIPS company, Netherlands) on fractured specimens of welded joints, made as a result of impact bend tests. An analysis of crack resistance of the welded joints was carried out under different conditions of test temperatures. It was based on experimental data, received by a quantitative fractography method. It is shown that metal of a welded joint produced by hybrid laser-arc welding at Vw = 72m/h rate has mainly failure of ductile nature after external loading. This indicates sufficient level of crack resistance and further working capacity under operation conditions.

Structural phase changes of the liquid water component in Alpine snow

2003 ◽  
Vol 37 (3) ◽  
pp. 227-232 ◽  
Author(s):  
A. Denoth
Keyword(s):  
Liquid Water ◽  
Structural Phase ◽  
Phase Changes

The Fe3+-O2- pair in the diamagnetic AMF3 perovskites: A sensitive probe for EPR investigations of structural phase changes

1977 ◽  
Vol 21 (12) ◽  
pp. 1097-1100 ◽  
Author(s):  
J.Y. Buzare ◽  
J.C. Fayet
Keyword(s):  
Structural Phase ◽  
Phase Changes

Major phase transformations and magnetic property changes caused by electromagnetic fields at microwave frequencies

2002 ◽  
Vol 17 (12) ◽  
pp. 3008-3011 ◽  
Author(s):  
Rustum Roy ◽  
Ramesh Peelamedu ◽  
Craig Grimes ◽  
Jiping Cheng ◽  
Dinesh Agrawal
Keyword(s):  
Structural Phase ◽  
Phase Changes ◽  
Stoichiometric Mixture ◽  
Melting Points ◽  
Soft Magnets ◽  
Microwave Frequencies ◽  
Magnetic Structures ◽  
Hard Magnets ◽  
Property Changes ◽  
The Magnetic Field

We demonstrate in this paper that common crystalline phases can be made noncrystalline and hard magnets can be converted to soft magnets in the solid state in several seconds at temperatures far below the melting points. New crystal structures and magnetic structures of ferromagnetic oxides (ferrites such as BaFe12O19, CoFe2O4, Fe3O4, and ZnFe2O4, etc.) are formed by reacting either the stoichiometric mixture of oxides or the preformed phase-pure crystalline material in a pure H field (or E field) at microwave (2.45 GHz) frequencies. These major changes in the magnetic properties as well as major structural phase changes are caused by the magnetic field.

scholarly journals Electrochromic Devices Based on Porous Tungsten Oxide Thin Films

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Y. Djaoued ◽  
S. Balaji ◽  
R. Brüning
Keyword(s):  
Thin Films ◽  
Transition Metal Oxides ◽  
Structural Phase ◽  
Phase Changes ◽  
Optical Modulation ◽  
Electrochromic Devices ◽  
Smart Windows ◽  
Porous Thin Films ◽  
Recent Developments ◽  
Ion Intercalation

Recent developments in the synthesis of transition metal oxides in the form of porous thin films have opened up opportunities in the construction of electrochromic devices with enhanced properties. In this paper, synthesis, characterization and electrochromic applications of porous WO3thin films with different nanocrystalline phases, such as hexagonal, monoclinic, and orthorhombic, are presented. Asymmetric electrochromic devices have been constructed based on these porous WO3thin films. XRD measurements of the intercalation/deintercalation of Li+into/from the WO3layer of the device as a function of applied coloration/bleaching voltages show systematic changes in the lattice parameters associated with structural phase transitions in LixWO3. Micro-Raman studies show systematic crystalline phase changes in the spectra of WO3layers during Li+ion intercalation and deintercalation, which agree with the XRD data. These devices exhibit interesting optical modulation (up to ~70%) due to intercalation/deintercalation of Li ions into/from the WO3layer of the devices as a function of applied coloration/bleaching voltages. The obtained optical modulation of the electrochromic devices indicates that, they are suitable for applications in electrochromic smart windows.

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