Investigation of Phase Transformations and Ordering During Combustion Synthesis

1995 ◽  
Vol 398 ◽  
Author(s):  
C.R. Kachelmyer ◽  
A. Varma ◽  
I.O. Khomenko ◽  
A.S. Rogachev ◽  
A.G. Merzhanov
Keyword(s):  
Phase Transformations ◽  
Combustion Synthesis ◽  
High Temperature Phase ◽  
Process Models ◽  
Advanced Materials ◽  
In Situ Observation ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Time Resolved

ABSTRACTTwo complementary experimental techniques are presented that describe the mechanisms during the combustion synthesis of NiAl and Ti5Si3. The first involves quenching a reacting wedge-shaped sample imbedded in a copper block where the propagating combustion front extinguishes while traveling to the apex. The second technique, time-resolved X-ray diffraction (TRXRD), provides a direct in-situ observation of the sequence of high temperature phase transformations. The information obtained from this investigation will be useful in developing improved process models of combustion synthesis, which can lead to the production of advanced materials with tailored microstructure and properties.

In Situ Time-Resolved X-Ray Diffraction Investigation of the ω→ψ Transition in Al-Cu-Fe Quasicrystal-Forming Alloys

2007 ◽  
Vol 558-559 ◽  
pp. 943-947 ◽  
Author(s):  
E. Otterstein ◽  
R. Nicula ◽  
J. Bednarčík ◽  
M. Stir ◽  
E. Burkel
Keyword(s):  
Large Scale ◽  
Applied Pressure ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
In Situ Xrd ◽  
Kinetics Of

Quasicrystals are aperiodic long-range ordered solids with a high potential for many modern applications. Interest is nowadays paid to the development of economically viable large-scale synthesis procedures of quasicrystalline materials involving solid-state transformations. The kinetics of the high-temperature phase transition from the complex ω-phase to the icosahedral quasicrystalline (iQC) ψ-phase in AlCuFe nanopowders was here examined by in-situ time-resolved X-ray diffraction experiments using synchrotron radiation. In-situ XRD experiments will allow insight on the influence of uniaxial applied pressure on the kinetics of phase transitions leading to the formation of single-phase QC nanopowders and further contribute to the optimization of sintering procedures for nano-quasicrystalline AlCuFe alloy powders.

scholarly journals Kinetics of a Phonon-Mediated Laser-Driven Structural Phase Transition in Sn2P2Se6

2019 ◽  
Vol 9 (3) ◽  
pp. 525
Author(s):  
Martin Kubli ◽  
Matteo Savoini ◽  
Elsa Abreu ◽  
Bulat Burganov ◽  
Gabriel Lantz ◽  
...  
Keyword(s):  
Structural Phase ◽  
Higher Order ◽  
High Temperature Phase ◽  
Incommensurate Phase ◽  
Temperature Phase ◽  
Complete Disappearance ◽  
X Ray Diffraction ◽  
Optical Pump ◽  
Time Resolved ◽  
The Time Domain

We investigate the structural dynamics of the incommensurately modulated phase of Sn 2P 2Se 6 by means of time-resolved X-ray diffraction following excitation by an optical pump. Tracking the incommensurable distortion in the time domain enables us to identify the transport effects leading to a complete disappearance of the incommensurate phase over the course of 100 ns. These observations suggest that a thin surface layer of the high-temperature phase forms quickly after photo-excitation and then propagates into the material with a constant velocity of 3.7 m/s. Complementary static structural measurements reveal previously unreported higher-order satellite reflection in the incommensurate phase. These higher-order reflections are attributed to cubic vibrational terms in the Hamiltonian.

Kinetics of high-pressure mineral phase transformations using in situ time-resolved X-ray diffraction in the Paris-Edinburgh cell: a practical guide for data acquisition and treatment

2008 ◽  
Vol 72 (2) ◽  
pp. 683-695 ◽  
Author(s):  
J. P. Perrillat
Keyword(s):  
High Pressure ◽  
Phase Transformations ◽  
Kinetic Studies ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Practical Guide ◽  
Set Up ◽  
Isothermal Kinetic

AbstractSynchrotron X-ray diffraction (XRD) is a powerful technique to study in situ and in real-time the structural and kinetic processes of pressure-induced phase transformations. This paper presents the experimental set-up developed at beamline ID27 of the ESRF to perform time-resolved angle dispersive XRD in the Paris-Edinburgh cell. It provides a practical guide for the acquisition of isobaric-isothermal kinetic data and the construction of transformation-time plots. The interpretation of experimental data in terms of reaction mechanisms and transformation rates is supported by an overview of the kinetic theory of solid-solid transformations, with each step of data processing illustrated by experimental results of relevance to the geosciences. Reaction kinetics may be affected by several factors such as the sample microstructure, impurities or differential stress. Further high-pressure kinetic studies should investigate the influence of such processes, in order to acquire kinetic information more akin to natural or technological processes.

Crystal structure of a high-pressure/high-temperature phase of alumina by in situ X-ray diffraction

2004 ◽  
Vol 3 (6) ◽  
pp. 389-393 ◽  
Author(s):  
Jung-Fu Lin ◽  
Olga Degtyareva ◽  
Charles T. Prewitt ◽  
Przemyslaw Dera ◽  
Nagayoshi Sata ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Pressure High Temperature

The stability of Fe5O6 and Fe4O5 at high pressure and temperature

2019 ◽  
Vol 104 (9) ◽  
pp. 1356-1359
Author(s):  
Koutaro Hikosaka ◽  
Ryosuke Sinmyo ◽  
Kei Hirose ◽  
Takayuki Ishii ◽  
Yasuo Ohishi
Keyword(s):  
High Pressure ◽  
Iron Oxides ◽  
High Temperature Phase ◽  
Chemical Compositions ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Diamond Anvil ◽  
The Stability ◽  
Laser Heated

Abstract The oxygen fugacity in the interior of the Earth is largely controlled by iron-bearing minerals. Recent studies have reported various iron oxides with chemical compositions between FeO and Fe3O4 above ~10 GPa. However, the stabilities of these high-pressure iron oxides remain mostly uninvestigated. In this study, we performed in situ X-ray diffraction (XRD) measurements in a laser-heated diamond-anvil cell (DAC) to determine the phase relations in both Fe5O6 and Fe4O5 bulk compositions to 61 GPa and to 2720 K. The results show that Fe5O6 is a high-temperature phase stable above 1600 K and ~10 GPa, while FeO + Fe4O5 are formed at relatively low temperatures. We observed the decomposition of Fe5O6 into 2FeO + Fe3O4 above 38 GPa and the decomposition of Fe4O5 into FeO + h-Fe3O4 at a similar pressure range. The coexistence of FeO and Fe3O4 indicates that none of the recently discovered compounds between FeO and Fe3O4 (i.e., Fe5O6, Fe9O11, Fe4O5, and Fe7O9) are formed beyond ~40 GPa at 1800 K, corresponding to conditions in the shallow lower mantle. Additionally, as some superdeep diamonds have genetic links with these high-pressure iron oxides, our results give constraints on pressure and temperature conditions of their formation.

Phase Transformation and Structural Studies of EUROFER RAFM Alloy

2006 ◽  
Vol 514-516 ◽  
pp. 500-504 ◽  
Author(s):  
A. Paúl ◽  
A. Beirante ◽  
Nuno Franco ◽  
Eduardo Alves ◽  
José Antonio Odriozola
Keyword(s):  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
High Concentration ◽  
Slow Cooling ◽  
Austenitic Phase ◽  
Full Transformation ◽  
X Ray ◽  
Rafm Steel

High temperature phase transformations in EUROFER reduced activation ferritic martensitic (RAFM) steel were studied in-situ by means of X-ray diffraction. Results show that, during slow cooling, the austenite to ferrite transformation takes place around 755 oC. Full transformation of the austenitic phase into pure martensite is observed for cooling above 5 oC/min. This transformation was found in samples annealed at 950 oC for 3 h and quenched in liquid nitrogen. TEM analyses reveal a high concentration of carbides along the grain boundaries of the martensitic structure. The thermal expansion coefficient derived from the measurements was 12.7x10-6 K-1.

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