Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

Observation of antiphase domain boundaries in GaAs on silicon by transmission electron microscopy

1988 ◽  
Vol 53 (13) ◽  
pp. 1207-1209 ◽  
Author(s):  
J. B. Posthill ◽  
J. C. L. Tarn ◽  
K. Das ◽  
T. P. Humphreys ◽  
N. R. Parikh
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Antiphase Domain ◽  
Transmission Electron ◽  
Domain Boundaries

Features of the ferroelectric domain structure in the multiferroic material YbMnO3

MRS Advances ◽  
2016 ◽  
Vol 1 (9) ◽  
pp. 591-596
Author(s):  
Takumi Inoshita ◽  
Yasuhide Inoue ◽  
Yoichi Horibe ◽  
Yasumasa Koyama
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Domain Structure ◽  
Ferroelectric Domain ◽  
Multiferroic Material ◽  
Ferroelectric State ◽  
Hexagonal Axis ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries

ABSTRACTThe multiferroic material YbMnO3 has been reported to exhibit both ferroelectric and antiferromagnetic orders in the ground state. Of these two orders, the ferroelectric order is associated with the P63/mmc-to-P63cm structural transition, which occurs around 1270 K. The interesting feature of the ferroelectric state is that a cloverleaf domain structure with a pseudo-six-fold symmetry is observed in transmission electron microscopy images with the beam incidence parallel to the hexagonal axis. To understand the origin of the formation of the cloverleaf domain structure, we have examined the crystallographic features of the ferroelectric state in YbMnO3 by transmission electron microscopy. In this study, particularly, we adopted the experimental condition that electron beam incidences are perpendicular to the hexagonal axis. It was, as a result, found that there existed various ferroelectric domain structures including the cloverleaf domain structure under the present condition. The notable feature of domain structures found in this study is that each domain structure basically consists of six domains, whose domain boundaries are terminated at one point. Because this feature makes us reminiscent of a discommensurate structure in an incommensurate state, we took high-resolution electron micrographs of areas including domain boundaries. Their analysis indicated that a domain boundary could be identified as a discommensuration with a phase slip of π/3. It is thus understood that the cloverleaf domain structure should be one of domain morphologies for a discommensurate structure, which is related to the break of the translational symmetry.

Observation of vortex domain structures in multiferroic hexagonal manganites RMnO3by transmission electron microscopy

Microscopy ◽  
2014 ◽  
Vol 63 (suppl 1) ◽  
pp. i22.3-i22
Author(s):  
Yoichi Horibe ◽  
Fei-Ting Huang ◽  
Taekjib Choi ◽  
Nara Lee ◽  
Sang-Wook Cheong
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Domain Structures ◽  
Transmission Electron ◽  
Hexagonal Manganites

Void Morphology In NiAl

2000 ◽  
Vol 646 ◽  
Author(s):  
M. Zakaria ◽  
P.R. Munroe
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Energy ◽  
Annealing Temperature ◽  
Void Formation ◽  
Dislocation Climb ◽  
Annealing Temperatures ◽  
Relative Incidence ◽  
Transmission Electron ◽  
Void Shape

ABSTRACTVoid formation in stoichiometric NiAl was studied through controlled heat treatments and transmission electron microscopy. Voids formed at temperatures as low as 400°C, but dissolved during annealing at 900°C. Both cuboidal and rhombic dodecahedral voids were observed, often at the same annealing temperature. At higher annealing temperatures (>800°C) extensive dislocation climb was noted. The relative incidence of void formation and dislocation climb can be related to the mobility of vacancies at each annealing temperature. Further, differences in void shape can be described in terms of their relative surface energy and mode of nucleation.

The Crystal Structure of the β’-Phase Including Ag in Al-Mg-Si-Ag Alloy

2011 ◽  
Vol 409 ◽  
pp. 67-70 ◽  
Author(s):  
Junya Nakamura ◽  
Kenji Matsuda ◽  
Tatsuo Sato ◽  
Calin D. Marioara ◽  
Sigmund J. Andersen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dark Field ◽  
Unit Cell ◽  
Atomic Column ◽  
Direction Parallel ◽  
Ag Addition ◽  
Domain Structures ◽  
Β Phase ◽  
Transmission Electron

In the present work, b’ phase in alloys Al -1.0 mass% Mg2Si -0.5 mass% Ag (Ag-addition) and Al -1.0 mass% Mg2Si (base) was investigated by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) to understand the effect of Ag addition. The b’ phase is rod-shape with the longest direction parallel to <001>Al. HRTEM images and SAED patterns obtained along the direction were similar for the b’ phase in both alloys. The unit cell of b’-phase in Ag-addition alloy is hexagonal with the same c-axis dimension as the Ag-free b’, but shorter a-axis. Ag was found in the composition of the rod-shaped precipitates in Ag-addition alloy by energy dispersive X-ray spectroscopy (EDS). In addition, the distribution of Ag was investigated by energy filtered mapping and high annular angular dark field scanning transmission electron microscopy (HAADF-STEM). The Ag-containing atomic column was observed in every b’ unit cell, and the unit cell symmetry is slightly changed as compared with the Ag-free b’. The Ag-containing b’ rods have complicated domain structures. The interfaces of these particles are enriched with Ag atoms that occupy the lattice positions in the Al matrix. The occupancy of the Ag-containing atomic columns seem to vary both inside particles, as well as at the interfaces.

Conversion of platelets into dislocation loops and voidite formation in type IaB diamonds

1995 ◽  
Vol 449 (1936) ◽  
pp. 295-313 ◽  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Local Mode ◽  
Diamond Structure ◽  
Dislocation Loops ◽  
X Ray ◽  
Regular Type ◽  
Transmission Electron ◽  
Stable Conditions ◽  
The One

Type la natural diamonds have been heated in the temperature range of 2400-2700°C under stabilizing pressures. The specimens studied are mainly regular type IaB diamonds. Transmission electron microscopy studies of treated speci­mens show that platelets are converted to interstitial ½ a 0 <011> dislocation loops; voidites are also formed. When all the platelets have been converted, the ex­perimental features associated with them also disappear, i. e. the X-ray extra reflections (spikes), the B' local-mode absorption and the lattice absorption in the one-phonon region termed the D spectrum. It is discovered that when diamonds are heated under graphite-stable rather than diamond-stable conditions, the rate of conversion is considerably enhanced; for instance, at 2650°C there is an increase in the rate of about three orders of magnitude. This enhancement is considered to be due to the instability of the diamond structure itself and a reason for this enhancement is suggested.

In-Situ Transmission Electron Microscopy and Computer Simulation Study of the Kinetics of Oxygen Loss in Yba2Cu3OZ

1989 ◽  
Vol 169 ◽  
Author(s):  
C. P. Burmester ◽  
L. T. Wille ◽  
R. Gronsky ◽  
B. T. Ahn ◽  
V. Y. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulation Study ◽  
Oxygen Loss ◽  
Domain Structures ◽  
Transmission Electron ◽  
Kinetics Of ◽  
Image Simulations

AbstractHigh resolution transmission electron microscopy during in‐situ quenching of YBa2Cu3Oz is used to study the kinetics of microdomain formation during oxygen loss in this system. Image simulations based on atomic models of oxygen‐vacancy order in the basal plane of this material generated by Monte Carlo calculations are used to interpret high resolution micrographs of the structures obtained by quenching. The observed domain structures agree well with those obtained from the simualtions.

CoSi2 Precipitate Coarsening During Formation of Buried Epitaxial Cosi2 Layers By Ion Beam Synthesis

1990 ◽  
Vol 201 ◽  
Author(s):  
R. Jebasinski ◽  
S. Mantl ◽  
K. Radermacher ◽  
P. Fichtner ◽  
W. Jăger ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Microstructural Evolution ◽  
Annealing Temperature ◽  
Ion Beam ◽  
Precipitate Coarsening ◽  
Annealing Temperatures ◽  
Transmission Electron

AbstractThe coarsening of CoSi2 precipitates and the microstructural evolution of (111) Si implanted with 200 keV Co+ ions at 350°C and fluences of 1×1016cm−2 and 6×1016cm−2 were investigated as a function of depth, annealing temperature and annealing time using Rutherford Backscattering Spectroscopy (RBS) and Transmission Electron Microscopy (TEM). After annealing cross-section TEM micrographs show a layered array of platelet-shaped precipitates with preferred facets on {111} planes. The fraction of Co-atoms, that were redistributed during the different annealing temperatures and times, has been used to determine an activation energy for the precipitate coarsening. By applying the Meechan-Brinkman and the change-of-slope methods, we obtained activation energies in the range of 3.2 – 3.6 eV.

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