Initial stages of electron beam-induced transformations in potassium β‴-Ferrite, KFe17O25

1990 ◽  
Vol 48 (4) ◽  
pp. 810-811
Author(s):  
J.L. Hutchison ◽  
Y. Matsui ◽  
F.J. Lincoln
Keyword(s):  
Electron Microscopy ◽  
Structural Changes ◽  
High Resolution Electron Microscopy ◽  
Hexagonal Structure ◽  
Atomic Level ◽  
Nominal Composition ◽  
List Type ◽  
Type Number ◽  
Resolution Electron ◽  
Topotactic Transformation

Potassium β’’’-ferrite, nominal composition KFe17O25 and isostructural with sodium β’’’- alumina, has a hexagonal structure consisting of spinel blocks (SB) separated by loosely packed conduction planes (CP) containing relatively mobile K+ cations. Various structural changes which occur during electron irradiation have been characterised by high resolution electron microscopy and may be summarised as follows:1Migration of K+ and O2−from the conduction planes, followed by2Frequent collapse of CP.3Topotactic transformation of the resulting multiply-twinned spinel layers to form broad laths of magnetite, Fe304.4Gradual growth of wüstite, Fe1-xO on exposed surfaces.We have examined KFe17O25 at 400 kV, using a JEOL 4000EX, the resolution (1.65 Å)being sufficient to resolve all cation rows along two main crystallographic directions, and We could thus monitor the earliest stages of structural transformation at the atomic level.

Advanced Computing in Electron Microscopy, Earl J. Kirkland 1998. Plenum Press, New York and London. 260 pages. ($72.50)

1999 ◽  
Vol 5 (5) ◽  
pp. 371-372
Author(s):  
John Spence
Keyword(s):  
Electron Microscopy ◽  
New York ◽  
Recent Observation ◽  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
Phase Identification ◽  
Transmission Electron ◽  
Resolution Electron ◽  
New Material ◽  
Advanced Computing

The recent observation of Bucky-tubes by S. Iijima using a transmission electron microscope (TEM) represents the first occasion in which a useful new material, subsequently available in commercial quantities, has been discovered by high-resolution electron microscopy (HREM). More commonly, the HREM method has been used for microcharacterization of materials at the atomic level, and for phase identification of submicrometer-sized microphases and polytypes.

High resolution observations of short-range ordering in disordered Au4Mn alloys

1984 ◽  
Vol 42 ◽  
pp. 426-427
Author(s):  
Nobuo Tanaka ◽  
Ken-ichi Ohshima ◽  
Jinpei Harada ◽  
J.M. Cowley
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Diffuse Scattering ◽  
Short Range ◽  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
X Ray ◽  
Direct Observations ◽  
Resolution Electron ◽  
Short Range Ordering

Observation of short range ordered (SRO) state in disordered binary alloys is the interesting topic in the point of order-disorder transition. The observation and analysis have been made with X-ray and neutron diffraction techniques which can give the SRO-parameters. These techniques, however, give only the information of an averaged structure. The ordering process is localized, so direct observations in atomic level by high resolution electron microscopy is needed for the detailed analysis.In the present study, disordered Au4Mn alloys were investigated with high resolution electron microscopy for the analysis of the origin of the characteristic SRO diffuse scattering (Fig. 1). The material was prepared by quenching and thinned by electrolytic polishing for microscopic observations. The specimen was observed along <120> direction by JEOL-200CX electron microscope (E=200keV).

High Resolution Electron Microscopy on zeolites

1990 ◽  
Vol 48 (4) ◽  
pp. 290-291
Author(s):  
H. W. Zandbergen ◽  
D. van Dyck
Keyword(s):  
High Resolution ◽  
Structural Changes ◽  
High Resolution Electron Microscopy ◽  
Pore Channel ◽  
Defect Characterization ◽  
List Type ◽  
Resolution Electron ◽  
Electron Microscopical ◽  
Small Metal Particles

Zeolites are very suitable for high-resolution electron microscopical investigation since their pore structure often allows an unambiguous interpretation of the images, especially when taken with the electron beam parallel to one of the pore channel direction. HREM can give very useful information on a number of subjects of major importance in zeolite synthesis a.Nucleation;b.Defect characterization;c.Characterization of growth mechanisms of denser phases;d.Structure determination;e.Identification of small metal particles inside the zeolite matrix.f.Structural changes due to (catalytic) reactions.

In situ high-resolution Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 512-513 ◽  
Author(s):  
Robert Sinclair
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Elevated Temperatures ◽  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
Video Recorder ◽  
Resolution Electron ◽  
Imaging Conditions ◽  
Major Impediment

In recent years, there have been many dramatic recordings of dynamic behavior, taken at the atomic level by high-resolution electron microscopy. However in the majority of cases, reliance has been placed on the imaging electron beam to bring about the changes in question. There are many disadvantages to this approach, not the least of which is the lack of experimental control available to the operator. Accordingly we have developed the application of a heating holder to achieve stable elevated temperatures at which reactions can be followed under atomic imaging conditions. This article briefly reviews our progress to-date.Our microscope system is quite conventional, showing that there is no major impediment to hot-stage HREM. We have employed a Philips EM 430 ST (300kV) instrument equipped with a Gatan image pick-up device and a commercial video-recorder. The heating holder is the Philips single tilt sideentry model (PW 6592) which we have found works well up to about 875°C. Of course a double tilt holder is preferable but we overcome the tilting limitations by judicious positioning of cross-section specimens. Image stability can be achieved by heating to a temperature below that of the observation for several minutes before "ramping up" to the desired level.

HREM STUDIES OF THE SUPERCONDUCTING PHASE Tl2Ba2Ca2Cu3Ox

1989 ◽  
Vol 03 (04) ◽  
pp. 361-367
Author(s):  
J.G. ZHENG ◽  
J. CHEN ◽  
J.G. JIANG ◽  
Y.H. LIANG ◽  
S.Y. DING ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Large Angle ◽  
Amorphous State ◽  
High Resolution Electron Microscopy ◽  
Superconducting Phase ◽  
Nominal Composition ◽  
Resolution Electron ◽  
Superconducting Ceramics

The superconducting phase Tl 2 Ba 2 Ca 2 Cu 3 O x (Tl2223) has been identified in high-T c superconducting ceramics with nominal composition of Tl 2 Ba 2 Ca 2 Cu 3. The configurations of grains and grain boundaries have also been observed directly by high resolution electron microscopy [HREM]. The small angle grain boundaries are mixed with both translation and orientation characteristics. The boundary regions are nearly parallel to (100) to (010) in crystal state, While in amorphous state, they are nearly parallel to (001). There also exists large angle grain boundaries in TlBaCaCuO superconductor.

scholarly journals TEM Studies of Precipitate Growth at the Atomic Level

1985 ◽  
Vol 62 ◽  
Author(s):  
J. M. Howe ◽  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Atomic Level ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Precipitate Growth ◽  
Convergent Beam ◽  
Microscopy Techniques

ABSTRACTRecent advances in transmission electron microscopy instrumentation and technique now make it possible to study the shape-evolution of precipitates in metallic alloys at the atomic level. This investigation demostrates how a combination of transmission electron microscopy techniques; namely, high-resolution electron microscopy, image simulation, energy-dispersive x-ray spectroscopy and convergent-beam electron diffraction are used to characterize the atomic structures, chemistry and growth mechanisms of γ' precipitate plates in an Al-4.2 a/o Ag alloy aged for 30 min. at 350°C. The complimentary information obtained from each of these techniques allows modelling of the growth process at the atomic level, thus providing insight into the basic precipitation behavior of alloys.

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