scholarly journals Devitrification of Zr55Cu30Al15Ni5Bulk Metallic Glass under Heating and HPT Deformation

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1329 ◽  
Author(s):  
Galina Abrosimova ◽  
Boris Gnesin ◽  
Dmitry Gunderov ◽  
Alexandra Drozdenko ◽  
Danila Matveev ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Metallic Glass ◽  
Metastable Phase ◽  
Hexagonal Structure ◽  
Crystalline Phases ◽  
Space Group ◽  
Activation Energy Of Crystallization ◽  
Nanocrystal Formation ◽  
Crystallization Stage

The nanocrystal formation in Zr55Cu30Al15Ni5 bulk metallic glass was studied under heat treatment and deformation. The activation energy of crystallization under heating is 278 kJ/mol. Different crystalline phases were found to be formed during crystallization under heating and deformation. At the first crystallization stage, the metastable phase with a hexagonal structure (lattice of space group P63/mmc with the parameters a = 8.66 Å, c = 14.99 Å) is formed under heat treatment. When the temperature rises, the metastable phase decays with the formation of stable crystalline phases. The crystalline Zr2Cu phase with the lattice of space group Fd3m is formed during crystallization under the action of deformation. It was determined that during deformation nanocrystals are formed primarily in the subsurface regions of the samples.

scholarly journals Interplay between Oxo and Fluoro in Vanadium Oxyfluorides for Centrosymmetric and Non-Centrosymmetric Structure Formation

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 603
Author(s):  
Prashanth Sandineni ◽  
Hooman Yaghoobnejad Asl ◽  
Weiguo Zhang ◽  
P. Shiv Halasyamani ◽  
Kartik Ghosh ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Metastable Phase ◽  
Compound I ◽  
Hydrothermal Route ◽  
Prolonged Heating ◽  
Space Group ◽  
Lithium Vanadium Oxide ◽  
Compound Ii ◽  
Unambiguous Assignment ◽  
Centrosymmetric Structure

Herein, we report the syntheses of two lithium-vanadium oxide-fluoride compounds crystallized from the same reaction mixture through a time variation experiment. A low temperature hydrothermal route employing a viscous paste of V2O5, oxalic acid, LiF, and HF allowed the crystallization of one metastable phase initially, Li2VO0.55(H2O)0.45F5⋅2H2O (I), which on prolonged heating transforms to a chemically similar yet structurally different phase, Li3VOF5 (II). Compound I crystallizes in centrosymmetric space group, I2/a with a = 6.052(3), b = 7.928(4), c = 12.461(6) Å, and β = 103.99(2)°, while compound II crystallizes in a non-centrosymmetric (NCS) space group, Pna21 with a = 5.1173(2), b = 8.612(3), c = 9.346(3) Å. Synthesis of NCS crystals are highly sought after in solid-state chemistry for their second-harmonic-generation (SHG) response and compound II exhibits SHG activity albeit non-phase-matchable. In this article, we also describe their magnetic properties which helped in unambiguous assignment of mixed valency of V (+4/+5) for Li2VO0.55(H2O)0.45F5⋅2H2O (I) and +4 valency of V for Li3VOF5 (II).

New Perovskite Based Structures in the Bi-Sr-O System

1992 ◽  
Vol 275 ◽  
Author(s):  
Bokhimi ◽  
M. Portilla
Keyword(s):  
Cell Parameter ◽  
Crystalline Phases ◽  
Space Group ◽  
Crystalline Structures ◽  
Cell Parameters ◽  
Group I

ABSTRACTWe report one amorphous and four new crystalline phases in the Bi-Sr-0 system. The structure of three of the crystalline phases was identified. The Br10Bi6O24-y phase, which is cubic with space group Fm3m and cell parameter a = 0.8471(1) nm. The SreBi10O27-y phase, which is tetragonal with the space group I/mmm, and cell parameters a = 0.6007(1), c = 0.8376(1) nm. The SreBi10O27-y phase, which is tetragonal with space group I/mmm and cell parameters a = 1.3221(1), c = 0.4249(1) nm. We show that in the crystalline structures Sr and Bi occupy equivalent sites.

Magnetic Properties, Nanostructure, and Ordering Kinetics of Nb Additive FePtCu Films

2010 ◽  
Vol 638-642 ◽  
pp. 1743-1748
Author(s):  
G.J. Chen ◽  
Y.H. Shih ◽  
Jason S.C. Jang ◽  
S.R. Jian ◽  
P.H. Tsai ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Magnetic Properties ◽  
Heating Rates ◽  
Fept Alloy ◽  
Ordering Kinetics ◽  
Nb Content ◽  
Kinetics Of ◽  
Nb Addition ◽  
Microstructure And Magnetic Properties

In this study,the (FePt)94-xCu6Nbx (x=0, 2.87, 4.52, 5.67) alloy films were prepared by co-sputtering. The effects of Nb addition content and heat treatment on the microstructure and magnetic properties of the polycrystalline FePtCu films are reported. Our previous experiments showed that the ordering temperature of the (FePt)94Cu6 films reduced to 320 °C, which is much lower than that of the FePt alloy. However, the grain growth after heat treatment limited the practical application in recording media. By adding the Nb content in the (FePt)94Cu6 film, the grain sizes of the films can be adjusted from 50 to 18nm, even for the films annealed at temperature as high as 600°C. DSC traces of as-deposited disorder films at different heating rates, to evaluate the crystallization of the order phase, revealed that the addition of Nb enhanced the activation energy of ordering from 87 kJ/mol to 288 kJ/mol for the (FePt)94-xCu6Nbx (x=0 and 2.87, respectively) films. The reduction of the grain size and the corresponding increase in the activation energy of the Fe-Pt-Cu-Nb films might result from the precipitation of the Nb atoms around the ordering FePt phase. The (FePt)94-xCu6Nbx (x=2.87) film showed a coercive force of 13.4 kOe and the magnetization of 687 emu/cc.

Diffusion Coefficients of Interest for the Simulation of Heat Treatment in Rare-Earth Transition Metal Magnets

2012 ◽  
Vol 727-728 ◽  
pp. 163-168 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Activation Energy ◽  
Rare Earth ◽  
Transition Metal ◽  
Impurity Atom ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Atom Diffusion ◽  
Essential Input

In the case of the modeling of sintering and heat treatments, the diffusion coefficients are an essential input. However, experimental data in the literature about diffusion coefficients for rare-earth transition metal intermetallics is scarce. In this study, the available data concerning diffusion coefficients relevant for rare-earth transition metal magnets are reviewed and commented. Some empirical rules are discussed, for example the activation energy is affected by the size of the diffusing impurity atom. Diffusion coefficients for Dy, Nd and Fe into Nd2Fe14B are given according an Arrhenius equation D=D0exp (-Q/RT). For Dy diffusion into Nd2Fe14B, Q 315 kJ/mol and D08 . 10-4m2/s.

Influence of the heat treatment on the crystallization mechanisms of Al85Y5Ni8Co2 metallic glass

2004 ◽  
Vol 343 (1-3) ◽  
pp. 143-149 ◽  
Author(s):  
Á. Révész ◽  
L.K. Varga ◽  
S. Suriñach ◽  
M.D. Baró
Keyword(s):  
Heat Treatment ◽  
Metallic Glass

Study of Corrosion Behavior of Conventional and Nanostructured WC-Co HVOF Sprayed Coats

2010 ◽  
Vol 64 ◽  
pp. 13-18 ◽  
Author(s):  
Shahin Khameneh Asl ◽  
Mohammad Reza Saghi Beyragh ◽  
Mahdi Ghassemi Kakroudi
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Heat Treating ◽  
Crystalline Phases ◽  
Chemical Test ◽  
Transmission Electron ◽  
Hvof Spray ◽  
Wear And Corrosion Resistance

Interest in nanomaterials has increased in recent years. This is due to the potential of size reduction to nanometric scale to provide properties of materials such as hardness, toughness, wear, and corrosion resistance. The current study is focused on WC-Co cermet coats, materials that are extensively used in applications requiring wear resistance. In this work, WC-17Co powder was thermally sprayed onto mild steel using High Velocity Oxy Fuel (HVOF) spray technique. The nanostructured specimen was produced from sprayed sample by heat-treating at 1100°C in a vacuum chamber. Their structures were studied by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Polarization and electrochemical impedance spectroscopy (EIS) tests were performed on the both types of coated samples in 3.5% NaCl solution. The amorphous phase in WC-17Co coating was transformed to crystalline phases by heat treatment at high temperatures. The heat treatment of these coatings at high temperature also resulted in partially dissolution of WC particles and formation of new crystalline phases. Generation of these phases produced the nanostructured coating with better mechanical properties. Comparative electro chemical test results showed that, the heat treatment could improve corrosion resistance of the nanostructured WC-17Co coat than the as sprayed coats.

Defect Spectroscopy on Damp-Heat Treated ZnO/CdS/Cu(In,Ga)(S,Se)2/Mo Heterojunction Solar Cells

2003 ◽  
Vol 58 (12) ◽  
pp. 691-702 ◽  
Author(s):  
C. Deibel ◽  
V. Dyakonov ◽  
J. Parisi
Keyword(s):  
Heat Treatment ◽  
Activation Energy ◽  
Solar Cells ◽  
Deep Level ◽  
Heat Exposure ◽  
Continuous Distribution ◽  
Open Circuit ◽  
Defect States ◽  
Band Bending ◽  
Test Cells

The changes of defect characteristics induced by accelerated lifetime tests on solar cells of the heterostructure ZnO/CdS/Cu(In,Ga)(S,Se)2/Mo are investigated. Encapsulated modules were shown to be stable against water vapor and oxygen under outdoor conditions, whereas the fill factor and open-circuit voltage of non-encapsulated test cells are reduced after prolonged damp heat treatment in the laboratory, leading to a reduced energy conversion efficiency. We subjected non-encapsulated test cells to extended damp heat exposure at 85 ◦C ambient temperature and 85% relative humidity for various time periods (6 h, 24 h, 144 h, 294 h, and 438 h). In order to understand the origin of the pronounced changes of the cells, we applied temperature-dependent current-voltage and capacitance voltage measurements, admittance spectroscopy, and deep-level transient spectroscopy. We observed the presence of electronic defect states which show an increasing activation energy due to damp heat exposure. The corresponding attempt-to-escape frequency and activation energy of these defect states obey the Meyer-Neldel relation. We conclude that the response originates from an energetically continuous distribution of defect states in the vicinity of the CdS/chalcopyrite interface. The increase in activation energy indicates a reduced band bending at the Cu(In,Ga)(S,Se)2 surface.We also observed changes in the bulk defect spectra due to the damp-heat treatment. - PACS: 73.20.hb, 73.61.Le

scholarly journals Влияние режима получения образцов и термообработки на локальную структуру халькогенидного полупроводника Ge-=SUB=-2-=/SUB=-Sb-=SUB=-2-=/SUB=-Te-=SUB=-5-=/SUB=-

2022 ◽  
Vol 56 (3) ◽  
pp. 291
Author(s):  
С.Н. Гарибова ◽  
А.И. Исаев ◽  
С.И. Мехтиева ◽  
С.У. Атаева ◽  
Р.И. Алекперов
Keyword(s):  
Heat Treatment ◽  
Thermal Processing ◽  
Thermal Evaporation ◽  
Amorphous State ◽  
Hexagonal Structure ◽  
Structural Elements ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Matrix ◽  
Close Range

Specifics of "amorphous state - crystal" phase transitions in dependence on the samples obtaining method and thermal processing, as well as changes in the structure and close range order in the arrangement of the atoms of Ge20Sb20.5Te51 chalcogenide semiconductors have been studied by the x-ray diffraction and Raman spectroscopy. It has been shown that Ge20Sb20.5Te51 films obtained by thermal evaporation on an unheated substrate are amorphous; after heat treatment at 220 and 400 °C, transform into a crystalline phase with a cubic and hexagonal structure. The chemical bonds and the main structural elements that form the matrix of the investigated objects, as well as the changes that occur in them during heat treatment, have been determined.

Influence of heat-treatment on magnetic, magnetostrictive and piezomagnetic properties and structure of Fe64Ni10Nb3Cu1Si13B9 metallic glass

2004 ◽  
Vol 375-377 ◽  
pp. 1065-1068 ◽  
Author(s):  
Z. Kaczkowski ◽  
G. Vlasák ◽  
P. Švec ◽  
P. Duhaj ◽  
P. Ruuskanen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Metallic Glass
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