The decomposition of magnesium hydroxide in an electron microscope

1958 ◽  
Vol 247 (1250) ◽  
pp. 346-352 ◽  
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Single Crystals ◽  
Magnesium Oxide ◽  
Magnesium Hydroxide ◽  
Basal Plane ◽  
Morphological Changes ◽  
Water Molecules ◽  
Two Stages

The beam of an electron microscope has been used to dehydrate single crystals of magnesium hydroxide to magnesium oxide. Electron diffraction photographs and electron micrographs were taken at various stages to follow the crystallographic and morphological changes which accompany decomposition. The decomposition may be considered to occur in two stages. First, there is a small shrinkage in the basal plane, and the resulting strain causes a maze of cracks in the crystal. This change is followed by a collapse of the planes down the original [0001] of magnesium hydroxide. The collapse is controlled by the migration of water molecules from between the planes to a surface where they can escape. The product is a highly oriented aggregate of micro-crystallites of magnesium oxide. More intense irradiation in the electron beam occasionally causes bulk movement of the solid.

In situ observation of the motion of ferroelectric domain walls in Bi4Ti3O12 single crystals

2016 ◽  
Vol 49 (5) ◽  
pp. 1645-1652 ◽  
Author(s):  
Wanneng Ye ◽  
Lingli Tang ◽  
Chaojing Lu ◽  
Huabing Li ◽  
Yichun Zhou
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Single Crystals ◽  
Transmission Electron Microscope ◽  
Domain Walls ◽  
Domain Switching ◽  
Ferroelectric Domain ◽  
In Situ Observation ◽  
Transmission Electron

Five types of ferroelectric domain walls (DWs) are present in Bi4Ti3O12 single crystals (Ye et al., 2015). Here their motion was investigated in situ using transmission electron microscopy and optical microscopy. The motion of P (a)-90° DWs, P (a)-180° DWs and P (c)-180° DWs was observed through electron beam poling in a transmission electron microscope. The growth of new P s(a)-180° nanodomains was frequently seen and they tended to nucleate at preexisting P s(a)-90° DWs. Irregularly curved P (c)-180° DWs exhibit the highest mobility, while migration over a short range occurs occasionally for faceted P s(a)-90° DWs. In addition, the motion of P s(a)-90° DWs and the growth/annihilation of new needle-like P s(a)-90° domains in a 20 µm-thick crystal were observed under an external electric field on an optical microscope. Most of the new needle-like P s(a)-90° domains nucleate at preexisting P s(a)-90° DWs and the former are much smaller than the latter. This is very similar to the situation for P s(a)-180° domain switching induced by electron beam poling in a transmission electron microscope. Our observations suggest the energy hierarchy for different domains of P s(c)-180° ≤ P s(a)-180° ≤ P s(a)-90° ≤ new needle-like P s(a)-90° in ferroelectric Bi4Ti3O12.

Annealing Effects in Ten Films of Thoria

1968 ◽  
Vol 26 ◽  
pp. 392-393
Author(s):  
S. E. Bronisz ◽  
Dana L. Douglass
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Electron Microscope ◽  
Single Crystals ◽  
Crystalline Materials ◽  
Transmission Electron ◽  
Annealing Effects ◽  
Diffraction Effects

Thin films of thoria, either cleaved from air-fired material or vacuum deposited on polished copper substrates, were examined by transmission electron microscopy. As prepared, the two types of samples were considerably different, but after being heated in the electron microscope they were closely similar.The cleaved samples were obtained by means of extraction replication of fracture surfaces of polycrystalline thoria. The thin flakes ranged from about 0.1 to 20 μm in diameter. Most of them were single crystals exhibiting the diffraction effects expected of crystalline materials and containing many long dislocations. Upon heating with the unapertured electron beam the dislocations disappeared, the crystals became more electron transparent, and the striated microstructure shown in Fig. 1 developed. The orientations of most of the cleaved crystals were equally divided among ﹛110﹜, ﹛111﹜, and ﹛112﹜. The striae were usually parallel to <110> or <135>.

Direct Observation of the Surface Topography of Single Crystals in a Transmission Electron Microscope

1981 ◽  
Vol 39 ◽  
pp. 208-211
Author(s):  
G. Lehmpfuhl ◽  
Y. Uchida
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Surface Topography ◽  
Single Crystals ◽  
Dynamic Effect ◽  
Thickness Variation ◽  
Crystal Thickness ◽  
Kinematic Effect ◽  
Diffraction Patterns ◽  
Small Change

From the analysis of convergent-beam electron diffraction patterns it is well known that the intensity of some reflections may become most sensitive to the crystal thickness variation at special conditions for thickness and orientation. This can be understood as a dynamic effect as well as a kinematic effect of electron diffraction. Using such a diffracted beam for imaging, a small change in thickness of a single crystal can be observed in an electron microscope. At the beginning of the application of this technique only weak beams were used for imaging the surface topography of undistorted single crystals. Thickness differences down to the atomic level could be detected in darkfield micrographs of MgO and Au. However, the intensity of the weak beams was so low that long exposure times up to 2 minutes were necessary to record a micrograph at a magnification of 20,000. This magnification is the upper limit for the weak-beam darkfield technique for reasons of stability of the electron microscope. The thickness contrast can be explained already by the kinematical theory of electron diffraction.

On the oriented conversion of Ca(OH)2 to CaO

1966 ◽  
Vol 35 (274) ◽  
pp. 867-870 ◽  
Author(s):  
S. Chatterji ◽  
J. W. Jeffery
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Initial Stage ◽  
Degree Of Orientation ◽  
High Degree ◽  
Orientational Relationship

SummaryIn order to study the orientational relationship between Ca(OH)2 and CaO, the transformation was carried out in stages inside an electron microscope by condensing the electron beam, and the process was monitored by electron diffraction. It has been found that at the initial stage all the hexagonal spots of Ca(OH)2 split into two ; on further heating one set of spots disappear. The remaining set of spots corresponds to the CaO structure, which has an orientational relationship to the hydroxide structure. To estimate the degree of orientation, a sample of brucite was treated in a similar way to the Ca(OH)2; a comparison shows that a high degree of orientation is preserved in the conversion of Ca(OH)2 to CaO. This observation is contrary to earlier reports.

Spherulite morphology in thin films of natural rubber

1962 ◽  
Vol 270 (1341) ◽  
pp. 232-241 ◽  
Keyword(s):  
Thin Films ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Natural Rubber ◽  
Single Crystals ◽  
Growth Mechanism ◽  
Electron Irradiation ◽  
Electron Diffraction Data ◽  
Dilute Solution ◽  
Spherulite Morphology

Crystalline ‘spherulites’ grown in ultra-thin films of natural rubber at — 26 °C were examined in the electron microscope. The spherulites form hollow domes, like blisters in the film, which collapse under electron irradiation producing remarkable fibre-like patterns of folds and creases. Within the spherulite, crystalline and amorphous regions coexist and the former appear to grow to a preferred thickness of a few hundred Angstroms with the molecular chains oriented perpendicular to the film. The molecules are thus almost certainly folded as in polymer single crystals grown from dilute solution. Electron diffraction data suggest that relatively large regions of the spherulite correspond to single crystals. A growth mechanism for the spherulites is proposed.

scholarly journals Diffraction of electrons by metal crystals and by mica

1935 ◽  
Vol 152 (875) ◽  
pp. 104-123 ◽  
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Single Crystals ◽  
Diffraction Spot ◽  
Two Dimensional ◽  
Crystalline Film ◽  
Dimensional Effects ◽  
Direct Bearing

The object of the research was to study the spot patterns produced when an electron beam of homogeneous velocity ~ 30 kV is transmitted through a thin crystalline film. Such spot patterns were first reported by Kikuchi, and their importance lies in the fact that they are regarded as being due to single crystals of matter; the study of the diffraction of electrons by single crystals must necessarily precede the exact explanation of the Debye-Scherrer patterns obtained when random aggregates are employed. The results described below have a direct bearing on the latter problem. Electron diffraction spot patterns due to the transmission of 30 kV electrons have been studied by Thomson, Kirchner, Trillat and Hirsch, Lassen. But the interpretations of these pseudo-two-dimensional effects has remained uncertain.

Domains in single crystals of poly-4-methyl-pentene-1

1987 ◽  
Vol 45 ◽  
pp. 488-489
Author(s):  
P. Pradère ◽  
J.-F. Revol ◽  
R. St. John Manley
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Single Crystals ◽  
Solution Concentration ◽  
Dark Field ◽  
Dilute Solution ◽  
Contrast Imaging ◽  
Slow Cooling ◽  
Carbon Coated ◽  
Isothermal Crystallisation

Polymer single crystals are generally considered to be structurally homogeneous. In this paper it is shown that in a given single crystal of poly-4-methyl-pentene-1 (P4MP1) there exist narrowly delimited domains that give rise to different electron diffraction (ED) patterns. The shape and location of these domains is characterized by diffraction contrast imaging in the dark field (DF) mode.Monolayer single crystals of P4MP1 polymorphs I and III were prepared in dilute solution (concentration ranging from 0.01 to 0.05%). Form I was obtained by slow cooling of a hexadecane solution whereas form III was prepared by isothermal crystallisation in xylene at 60°C. Crystals were deposited on carbon coated grids and observed with a Philips EM 400 T electron microscope operated at 120 kV. The crystals are very radiation sensitive and the total end point dose, measured by the fading of the ED pattern is 27 C m-2.

The Structure and Texture of Y2O3:Tb Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
J. Taylor ◽  
M. Libera ◽  
E. Goldburt ◽  
R. Bhargava
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Selected Area Electron Diffraction ◽  
Incident Electron Beam ◽  
Transmission Electron ◽  
Cubic Structure ◽  
Diffraction Patterns ◽  
Electron Energy Loss ◽  
Microstructural Studies

AbstractThis paper presents the results of microstructural studies of terbium-doped yttria quantum nanocrystals by imaging and diffraction in a transmission electron microscope. The nanocrystals are typically found in clusters of varying size. Electron energy-loss spectroscopy confirms that the particles consist of yttrium and oxygen. Analysis of selected-area electron diffraction patterns shows that the nanocrystals largely have the cubic structure found in bulk yttria. These patterns furthermore suggest that within each cluster the nanocrystals align themselves with a preferred orientation relative to the incident electron beam as well as to each other.

STUDY OF IONIC CRYSTALS UNDER ELECTRON BOMBARDMENT

1951 ◽  
Vol 29 (2) ◽  
pp. 122-128 ◽  
Author(s):  
D. E. McLennan
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Crystal Lattice ◽  
High Intensity ◽  
Alkali Halides ◽  
Electron Bombardment ◽  
High Electron ◽  
Ionic Crystals ◽  
Small Crystals

Electron bombardment experiments have been carried out on small crystals of the alkali halides within the electron microscope. Crystals of two size ranges were bombarded at high intensity, and evidence of a generalized photographic effect within the ionic group of solids is presented. The first group of crystal specimens ranged in size from 0.2 to 0.002 cm., the bombardment causing the formation of F-centers and entrapped metal colloids in the crystal lattice. Ionization pulses were observed to occur in the region of the specimen during bombardment. The second group ranged in size from 10 to 0.01 μ, observations on the effects of bombardment being carried out with electron diffraction techniques. A process has been suggested to explain the phenomenon of ionic crystals which appear to lose their centers under high electron beam intensity in the electron microscope.

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