scholarly journals The Interpretation of HRTEM Images of Partially Amorphized Pyrochlore Structure Types.

1990 ◽  
Vol 183 ◽  
Author(s):  
Mark L. Miller ◽  
R. C. Ewing
Keyword(s):  
Limit Of Detection ◽  
Amorphous Material ◽  
Pyrochlore Structure ◽  
Image Contrast ◽  
Crystalline Material ◽  
Total Thickness ◽  
Volume Percent ◽  
Crystalline Materials ◽  
Image Simulations ◽  
Crystalline Matrix

AbstractThe results of image simulations on partially amorphous microlite (Ca2Ta2O7, pyrochlore structure) are presented. Results indicate that HRTEM images are not sensitive to the position of amorphous layers within a crystalline matrix. In addition, it is observed that the limit of detection of amorphous material within a crystalline matrix is dependent upon the total thickness of the sample. In thin crystals (<150 Å), up to 75 volume percent crystalline material can give rise to aperiodic images, yet the addition of a small amount of crystalline material (80 volume percent crystalline) produces a periodic image. Images calculated for isolated spheres of amorphous material distributed within crystalline microlite suggest that isolated domains of amorphization are observable at sample thicknesses less than three times the diameter of the feature. The image contrast of amorphized domains is enhanced by imaging at defocus settings significantly different than Scherzer focus. These results indicate that interpretation of HRTEM images of partially amorphized crystalline materials should be undertaken with caution, and estimates of the volume of damage considered only qualitative.

Chemical Assay and Isolation of Chick Edema Factor in Biological Materials

1966 ◽  
Vol 49 (4) ◽  
pp. 824-828
Author(s):  
T C Campbell ◽  
L Friedman
Keyword(s):  
Thin Layer ◽  
Biological Material ◽  
Absorption Maximum ◽  
Limit Of Detection ◽  
Crystalline Material ◽  
Gas Chromatograph ◽  
Crystalline Materials ◽  
Edema Factor ◽  
Chemical Assay ◽  
Approximate Limit

Abstract In the chemical assay for the chick edema factor (CEF) in biological material, the unsaponifiable matter containing the CEF is recovered from the saponification mixture and is cleaned up by column (alumina adsorption) and thin layer (silica gel adsorption) procedures. The final extract is analyzed on an electron capture gas chromatograph, and the chromatogram peaks are compared to a known standard. Recovery is good, and the approximate limit of detection is 0.2 ppb. Two CEF components that have been isolated as crystalline materials correspond to Peaks 4a and 7 of previously isolated material. The UV absorption maximum for the crystalline material is 242 mμ.

Crystallization of Pyrolyzed Polysilazanes

1990 ◽  
Vol 180 ◽  
Author(s):  
Roger L. K. Matsumoto
Keyword(s):  
Ceramic Material ◽  
Amorphous Material ◽  
Amorphous Structure ◽  
Crystalline Material ◽  
Inorganic Polymers ◽  
Processing Conditions ◽  
Polymer Backbone ◽  
Crystalline Materials

ABSTRACTPolysilazanes are inorganic polymers which convert to a ceramic material when pyrolyzed. Initial pyrolysis results in a solid, amorphous material. Further heating transforms the amorphous structure to a crystalline material. In addition to the Si-N linkages in the polymer backbone, polysilazanes generally contain appreciable amounts of carbon in side groups. Consequently, pyrolysis can result in mixed Si3N4 - SiC crystalline materials. It will be shown that either Si3N4 or SiC could be selectively crystallized depending upon processing conditions.

Scanning Transmission Microscopy Applied to Thick Specimen

1972 ◽  
Vol 30 ◽  
pp. 452-453
Author(s):  
H. Koike ◽  
T. Matsuo ◽  
K. Ueno ◽  
M. Suzuki
Keyword(s):  
Psoas Muscle ◽  
Image Intensifier ◽  
Chromatic Aberration ◽  
Image Contrast ◽  
Transmission Microscopy ◽  
Crystalline Materials ◽  
Thick Specimen ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Microscope Image

Since the identification of single atoms was achieved by Crewe et al, scanning transmission microscopy has been put into pratical use. Recently they applied this method to the quantitative mass analysis of DNA.As pointed out previously the chromatic aberration which decreases the image contrast and quality, does not affect a scanning transmission image as it does a conventional transmission electron microscope image. Thus, the STEM method is advantageous for thick specimen. Further this method employs a high sensitive photomultiplier tube which also functions as an image intensifier. This detection method is effective for the observation of living specimens or easily damaged specimens. In this respect the scanning transmission microscope with high accelerating voltage is necessary.Since Uyeda's experiments of crystalline materials, many workers have been discussed how thick specimens can be observed by CTEM. With biological specimens, R. Szirmae reported on the decrease in the image contrast of rabbit psoas muscle sections at various accelerating voltages and specimen thicknesses.

HREM image simulations for supported metal particle catalysts

1993 ◽  
Vol 51 ◽  
pp. 736-737 ◽  
Author(s):  
Ming-Hui Yao ◽  
David J. Smith
Keyword(s):  
Fine Particles ◽  
Amorphous Material ◽  
Chemical Properties ◽  
Morphological Features ◽  
Metal Particles ◽  
Plan View ◽  
Profile View ◽  
Imaging Conditions ◽  
Image Simulations ◽  
Supported Metal

The chemical properties of catalysts often depend on the size, shape and structure of the supported metal particles. To characterize these morphological features and relate them to catalysis is one of the main objectives for HREM study of catalysts. However, in plan view imaging, details of the shape and structure of ultra-fine supported particles (<2nm) are often obscured by the overlapping contrast from the support, and supported sub-nanometer particles are sometimes even invisible. Image simulations may help in the interpretation at HREM images of supported particles in particular to extract useful information about the size, shape and structure of the particles. It should also be a useful tool for evaluating the imaging conditions in terms of visibility of supported particles. P. L. Gai et al have studied contrast from metal particles supported on amorphous material using multislice simulations. In order to better understand the influence of a crystalline support on the visibility and apparent morphological features of supported fine particles, we have calculated images of Pt and Re particles supported on TiO2(rutile) in both plan view and profile view.

scholarly journals Impact of Thermal Oxidation on Morphological, Structural and Magnetic Properties of Fe-Ni Wire-Like Nanochains

2021 ◽  
Author(s):  
Marcin Krajewski ◽  
Mateusz Tokarczyk ◽  
Sabina Lewińska ◽  
Kamil Bochenek ◽  
Anna Ślawska-Waniewska
Keyword(s):  
Magnetic Properties ◽  
Thermal Oxidation ◽  
Amorphous Material ◽  
Crystalline Material ◽  
Future Application ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Structural And Magnetic Properties ◽  
Source Of Information ◽  
The Magnetic Field

AbstractThis work presents the evolution of morphological, structural and magnetic properties of amorphous Fe-Ni wire-like nanochains caused by thermal oxidation. The initial Fe1−xNix samples (x = 0.75; 0.50; 0.25) were prepared through the magnetic-field-induced synthesis, and then they were heated in dry air at 400 °C and 500 °C. These treatments led to two competing simultaneous processes occurring in the investigated samples, i.e., (i) a conversion of amorphous material into crystalline material, and (ii) their oxidation. Both of them strictly affected the morphological and structural properties of the Fe-Ni nanochains which, in turn, were associated with the amount of iron in material. It was found that the Fe0.75Ni0.25 and Fe0.50Ni0.50 nanochains were covered during thermal treatment by the nanoparticle oxides. This coverage did not constitute a good barrier against oxidation, and these samples became more oxidized than the Fe0.25Ni0.75 sample which was covered by oxide nanosheets and contained additional Ni3B phase. The specific morphological evolutions of the Fe-Ni nanochains also influenced their saturation magnetizations, whereas their coercivities did not vary significantly. The obtained results constitute an important source of information for future application of the thermally treated Fe-Ni nanochains which could be applied in the energy storage devices or catalysis.

Geochemical and Petrological Characterization of Ash Samples from Cascade Range Volcanoes

1971 ◽  
Vol 1 (2) ◽  
pp. 261-282 ◽  
Author(s):  
Keith Randle ◽  
Gordon G. Goles ◽  
Laurence R. Kittleman
Keyword(s):  
Pacific Northwest ◽  
Volcanic Ash ◽  
Cascade Range ◽  
Crystalline Material ◽  
Refractive Indices ◽  
Crystalline Materials ◽  
The Pacific ◽  
Volcanic Ashes ◽  
Different Sources

Twenty-nine samples of volcanic ash from the Pacific Northwest were analyzed by instrumental neutron activation techniques, with the aim of distinguishing among ashes from different sources. Preliminary results of petrographic studies of 42 ash or pumice samples are also reported. Geochemical characteristics of Mazama ash are defined, and problems induced by winnowing of crystalline material during transport and by weathering are discussed. Contents of La, Th, and Co, and La/Yb ratios are shown to be good discriminants. Data on refractive indices and on proportions of crystalline materials also aid in distinguishing among the various volcanic ashes studied. Ash and pumice found in archaeological contexts at Fort Rock Cave, Paisley Cave, Wildcat Canyon, and Hobo Cave are all from Mount Mazama, presumably from the culminating cruption of 7000 years ago.

Mechanism of the Crystallization of High Polymers

1954 ◽  
Vol 27 (2) ◽  
pp. 374-384 ◽  
Author(s):  
G. Schuur
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Amorphous Material ◽  
Crystalline Polymer ◽  
Longitudinal Direction ◽  
Crystalline Material ◽  
Current View ◽  
X Ray ◽  
Made In ◽  
High Polymers

Abstract The crystallization of higher polymers is a phenomenon which is not yet fully understood, one of the main difficulties being to explain how the spherulites arise. An attempt will be made in this paper to draw a clearer picture of the mechanism of crystallization and thus to account for the origin of spherulites. It will then be seen how several other phenomena involved in the crystallization of natural rubber can be shown to be logically interrelated. The current view is that a crystalline polymer consists of a continuous amorphous phase containing small crystalline regions, the crystallites. The evidence as to the size of these crystallites, however, is at present inconclusive, because only the lower limit of their size can be measured by means of x-ray examination. The reason is that, owing to the absence of reflections of a higher order, the effect of irregularities in the crystallites and of the heat motion of the molecules cannot be measured separately. Another doubtful question is whether the small angle interference maxima are to be interpreted as a measure of mean distances between the crystallites. To do this, Wallner has to resort to the assumption that the crystallites are unstable, whereas it is presumed, on the evidence of the mechanical properties of the high polymers, that a crystallite is stable and permanent. Hoffmann found 82 ± 7 per cent of crystalline material in polychlorotrifluoroethylene and Buckley, Cross, and Ray found as much as 95 per cent in polymethylene. Such high percentages make it doubtful whether the crystalline phase can be discontinuous at all. In this article any volume of material in which the molecules lie parallel is called a crystallite. The direction in which the molecules are oriented is termed the longitudinal direction of the crystallite. It is immaterial to the argument whether a crystallite consists of several crystallites, aligned in parallel separated by a small amount of amorphous material, or of a single crystallite containing large irregularities.

Laser Ablation of Crystalline Material With and Without Water on Material Surface

2019 ◽  
Author(s):  
Wenlong Yao ◽  
Li Yan ◽  
Yunshu Qi ◽  
Ning Mei
Keyword(s):  
Statistical Physics ◽  
Morphological Changes ◽  
Phase Variation ◽  
Water Layer ◽  
Density Variation ◽  
Crystalline Material ◽  
Material Surface ◽  
Ablation Process ◽  
Crystalline Materials ◽  
Atomic Image

Abstract The phase and morphological changes of crystalline material during laser internal ablation with and without water on the material surface are studied using molecular dynamics simulations. The atomic image of the material morphology was obtained by recording the velocity and position variation of atoms. Temperature distribution contour of the crystalline material along the ablation process are charted by statistical physics method. Furthermore, density variation and phase variation contour of water are also charted. The results suggest that: First, during the ablation process of crystalline materials, energy transfer occurs between water and crystalline materials. Supercritical water is formed first, which restrains the sputtering of crystalline materials due to phase explosion and puts off the sputtering. Then the physical state of water changes from liquid to gaseous. Second, with water on the surface, the cavity shape is different from that without water, the width of upper part of cavity is decreased. Third, the volume of the cavity is affected by the thickness of the water layer.

Fabrication of polycrystalline thin films of liquid crystalline materials by solution process and its application to OFETs

2008 ◽  
Vol 1091 ◽  
Author(s):  
Hiroaki Iino ◽  
Jun-ichi Hanna
Keyword(s):  
Thin Films ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Solution Process ◽  
Crystalline Material ◽  
Crystalline Materials ◽  
Polycrystalline Thin Films ◽  
Channel Performance ◽  
Liquid Crystalline Materials ◽  
Liquid Crystalline Material

AbstractWe have fabricated polycrystalline OFETs of two different liquid crystalline materials i.e., ω,ω'-dihexylquaterthipohene (6-QTP-6) and N, N'-ditridecylperylenediimide (13-Per-13) by solution process. Liquid crystalline materials help fabricating uniform thin films on the substrate when spin-coated at their temperature range of liquid crystalline phase. The FETs fabricated with 6-QTP-6 exhibited p-channel performance and its mobility was determined to be 0.04 cm2/Vs, which was comparable to that determined by time-of-flight experiments. The FETs fabricated with 13-Per-13 exhibited n-channel performance and its FET mobility was 0.008 cm2/Vs, while the mobility was increased up to 0.11 cm2/Vs after thermal annealing of the film at a liquid crystalline temperature of 220°C for an hour. Judging from these facts, the grain boundaries are controlled not so as to across the conduction channels formed by self-aligned π-conjugated aromatic cores in liquid crystalline molecules. We conclude that liquid crystalline material is a good candidate for quality polycrystalline thin films for OFETs.

The thermal fission-induced crystalline-to-amorphous transformation in U6Fe

1988 ◽  
Vol 3 (3) ◽  
pp. 453-460 ◽  
Author(s):  
Don M. Parkin ◽  
Reed O. Elliott
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystallization Behavior ◽  
Amorphous Material ◽  
Nucleation And Growth ◽  
Local Defect ◽  
Scanning Calorimetry ◽  
Dose Dependent ◽  
Limited Process ◽  
Total Resistivity ◽  
Crystalline Matrix

The crystalline-to-amorphous transformation in U6Fe produced by thermal fission fragment damage was studied using resistivity and differential scanning calorimetry. The results are described in terms of a model of radiation-produced defect buildup in the crystalline matrix followed by transformation of small regions to an amorphous phase when a critical local defect concentration is reached. This can occur directly in a single cascade or from cascade overlap. The total resistivity is modeled assuming an inhomogeneous media consisting of a crystalline matrix containing a dose-dependent concentration of defects and amorphous zones. The crystallization behavior is initially, starting at Tc = 388 K, a kinetically limited process of shrinkage of amorphous zones that gradually transforms to nucleation and growth in fully amorphous material at Tc = 555 K.

Sign in / Sign up

Export Citation Format

Share Document