Crystallization characteristics of an amorphous Nb81Si19 alloy under high pressure and formation of the A15 phase

Wang, W. K.; Iwasaki, Hiroshi; Suryanarayana, C.; Masumoto, T.; Toyota, Naoki; Fukase, Tetsuo; Kogiku, F.

doi:10.1007/bf00752270

Cited by 37 publications

(5 citation statements)

References 17 publications

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“…However, when the same crystallization phenomenon was monitored by in situ TEM, the external pressure decreased from the values typical of a DSC experiment (10 5 Pa) down to those usually expected inside a FEG-TEM microscope's column (about 10 −4 Pa). The influence of the external pressure on the crystallization of formerly amorphous materials has been previously studied, and some papers [30][31][32][33][34] showed that in amorphous alloys, an increase of the external pressure could retard the beginning of the crystallization, thereby increasing its starting temperature, which is the opposite to what we report here. This occurrence is normally ascribed to the pressure effect on the atomic diffusion during the crystallization.…”

Section: Discussioncontrasting

confidence: 90%

In Situ TEM Crystallization of Amorphous Iron Particles

2020

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Even though sub-micron and nano-sized iron particles generally display single or polycrystalline structures, a growing interest has also been dedicated to the class of amorphous ones, whose absence of a crystal structure is capable of modifying their physical properties. Among the several routes so far described to prepare amorphous iron particles, we report here about the crystallization of those prepared by chemical reduction of Fe3+ ions using NaBH4, with sizes ranging between 80 and 200 nm and showing a high stability against oxidation. Their crystallization was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and in situ heating transmission electron microscopy (TEM). The latter technique was performed by the combined use of electron diffraction of a selected sample area, and bright and dark field TEM imaging, and allowed determining that the crystallization turns the starting amorphous particles into polycrystalline α-Fe ones. Also, under the high vacuum of the TEM column, the crystallization temperature of the particles shifted to 550 °C from the 465 °C, previously observed by DSC and XRD under 105 Pa of Ar. This indicates the pivotal role of the external pressure in influencing the starting point of phase transition. Conversely, upon both the DSC/XRD pressure and the TEM vacuum conditions, the mean size of the crystal domains increases as a consequence of further thermal increase, even if with some pressure-related differences.

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Section: Discussioncontrasting

confidence: 90%

In Situ TEM Crystallization of Amorphous Iron Particles

2020

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“…To examine the structural stability, Table lists the calculated lattice parameters and formation enthalpy of Nb 3 Si with six possible structures. It can be seen that the calculated lattice parameters of Nb 3 Si with cubic and tetragonal structures are in good agreement with the experimental data . In addition, the calculated lattice parameters of the predicted Br 3 Sm‐type are a = 6.031 Å, b = 9.488 Å, and c = 4.692 Å, and the lattice parameters of the predicted Sc 3 In‐type structure are a = 4.533 Å and c = 7.788 Å, respectively.…”

Section: Resultssupporting

confidence: 73%

“…221) and V 3 Si‐type (space group: Pm‐3n , No. 223) . Although Cu 3 Au‐type is a typical L1 2 structure, it is unstability at the ground state.…”

Section: Methodsmentioning

confidence: 99%

Prediction of New Structure, Phase Transition, Mechanical, and Thermodynamic Properties of Nb3Si

Pan

2017

Adv Eng Mater

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Although Nb-based silicides are promising high temperature materials, the high temperature application of Nb-based silicides is markedly influenced by Nb 3 Si phase. However, the structure and relevant properties of Nb 3 Si are not completely clear. To solve these problems, in this paper, we systematically investigate the structure, elastic properties, brittle or ductile behavior, and thermodynamic properties of Nb 3 Si based on the first-principle calculations. Additionally, phase transition of Nb 3 Si under high pressure is studied in detail. The calculated results show that two new Nb 3 Si phases: Br 3 Sm-type (space group: Cmcm, No.63) and Sc 3 In-type (space group: P63/mmc, No.194) are predicted. Although Nb 3 Si with Ta 3 Si-type is the most stable structure, pressure leads to phase transition from Ta 3 Si-type structure to V 3 Si-type structure at %60 GPa. We further demonstrate that Nb 3 Si is a ductile material. Importantly, we find that the heat capacity of Nb 3 Si with tetragonal structure is about 190 J (mol K) À1 , which is two times larger than that of other structures.

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“…Generally, the relative excess volume of amorphous alloy (DV am /V c ) is some several per cent, which is much smaller than that of a-Se. Assuming g/DG am is of about the same order for amorphous solids, it can be deduced from equation (6) that DV in for amorphous alloys is much smaller than that for a-Se. Smaller DV in means smaller activation energy increases under pressure according to equation (4).…”

Section: Discussionmentioning

confidence: 99%

Pressure effect on polymorphous crystallization kinetics in amorphous selenium

1998

Acta Materialia

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Crystallization characteristics of an amorphous Nb81Si19 alloy under high pressure and formation of the A15 phase

Cited by 37 publications

References 17 publications

In Situ TEM Crystallization of Amorphous Iron Particles

In Situ TEM Crystallization of Amorphous Iron Particles

Prediction of New Structure, Phase Transition, Mechanical, and Thermodynamic Properties of Nb3Si

Pressure effect on polymorphous crystallization kinetics in amorphous selenium

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