Dynamical dependence of thermal phase transformations in finite systems

AbstractThe crystal structure of sophiite, Zn2(SeO3)Cl2 (a = 10.251(4), b = 15.223(2), c = 7.666(5) Å, Z = 8) was solved in space group Pccn from single crystal X-ray data, and refined to R = 0.053 for 666 Fo > 4oFo. The mineral belongs to layer compounds. The threefold coordinated Se atom is at the apex of a pyramid, the base of which is formed by three O atoms; Se-O = 1.69 Å. Zn cations occupy two positions with distorted tetrahedral and octahedral coordinations. In the tetrahedra, Zn cations are surrounded by two O (2.02 Å) and two Ci (2.224 Å) atoms. Zn octahedra contain four O atoms (2.07 Å) and two CI atoms (2.701 Å). The atomic arrangement is characterized by rings containing two Se pyramids linked by their corners to two Zn tetrahedra. The rings are linked by their edges and corners to Zn octahedra to form layers parallel to (010). The layers are interconnected by residual Van der Waals bonds.Experimental results on thermal phase transformations and deformations, crystal optics and other physical properties of sophiite are presented. A structural aspect of their anisotropy is discussed.

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Experimental characterization of free convection during thermal phase transformations in shape memory alloy wires

Smart Materials and Structures ◽

10.1088/0964-1726/11/3/312 ◽

2002 ◽

Vol 11 (3) ◽

pp. 411-422 ◽

Cited By ~ 36

Author(s):

A Bhattacharyya ◽

L Sweeney ◽

M G Faulkner

Keyword(s):

Shape Memory Alloy ◽

Free Convection ◽

Shape Memory ◽

Phase Transformations ◽

Experimental Characterization ◽

Thermal Phase

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Diffusion-thermal phase transformations in titanium hydride containing a multi-quality system of hydrogen traps

Perspektivnye Materialy ◽

10.30791/1028-978x-2021-6-5-15 ◽

2021 ◽

Vol 6 ◽

pp. 5-15

Author(s):

R. N. Yastrebinsky ◽

◽

G. G. Bondarenko ◽

V. I. Pavlenko ◽

A. A. Karnaukhov ◽

...

Keyword(s):

Crystal Lattice ◽

Phase Transformations ◽

Thermal Diffusion ◽

Titanium Hydride ◽

Multilayer Coating ◽

Metallic Titanium ◽

X Ray ◽

Temperature Range ◽

Thermal Phase ◽

The Creation

Diffusion-thermal phase transformations in a modified titanium hydride containing a multiparting system of hydrogen traps. Modification of titanium hydride was carried out by the method of layer-by-layer electrochemical precipitation of metallic titanium and copper from organic and inorganic solutions of their salts. The creation on the surface of the titanium hydride of a multilayer coating (Ti – Cu) obtained by the electrochemical precipitation method increases the thermal stability of the metal hydride system by 229.7 °C. Methods of X-ray-phase, X-ray structural and electron-probe microanalysis are shown, the constancy of the phase composition of the modified titanium hydride in the temperature range of 100 – 700 °C. The most essential defects of the crystal lattice in a modified titanium hydride occur at a temperature of 500 °C — due to the hydrogenation of the modification titanium shell and blocking the microcrack of the surface with a copper coating, the period of the elementary cell and the volume of the hydride phase crystal volume changes. The largest concentration of hydrogen in the surface layer (up to 87.9 %) occurs in the temperature range of 300 – 500 °C, which ensures the maximum density of defects in the crystal lattice. At 700 °C, a dislocation density decreases and a decrease in the crystal cell parameters associated with the annealing mode of titanium hydride and hydrogen thermal diffusion into the volume of material. A metallic titanium precipitated on the titanium hydride surface is an effective structural trap of hydrogen diffusing to surface layers during thermal heating, and the creation of an additional protective copper sheath prevents the thermal diffusion of hydrogen into the environment.

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Diffusion-Thermal Phase Transformations in Titanium Hydride Containing a Multi-Barrier Systems of Hydrogen Traps

Inorganic Materials Applied Research ◽

10.1134/s2075113321050439 ◽

2021 ◽

Vol 12 (5) ◽

pp. 1206-1213

Author(s):

R. N. Yastrebinsky ◽

G. G. Bondarenko ◽

V. I. Pavlenko ◽

A. A. Karnaukhov

Keyword(s):

Phase Transformations ◽

Titanium Hydride ◽

Thermal Phase

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The use of high-resolution FESEM to study solid-state phase transformations and reactions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100172875 ◽

1994 ◽

Vol 52 ◽

pp. 1028-1029

Author(s):

P. G. Kotula ◽

D. D. Erickson ◽

C. B. Carter

Keyword(s):

Solid State ◽

High Resolution ◽

Phase Transformations ◽

High Efficiency ◽

Sol Gel ◽

Quantitative Information ◽

Solid State Reactions ◽

Critical Dimensions ◽

Backscattered Electrons ◽

Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

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The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150046 ◽

1993 ◽

Vol 51 ◽

pp. 842-843

Author(s):

K. Barmak

Keyword(s):

Thin Film ◽

Thin Films ◽

Phase Transformations ◽

Analytical Electron Microscopy ◽

Ex Situ ◽

Multilayer Thin Films ◽

Absolute Concentration ◽

Analytical Electron ◽

Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

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