Direct amorphous-structure analysis: How are surface/bulk structure and activity of titania photocatalyst particles changed by milling?

In order to improve the electrochemical cycle stability of the La-Mg-Ni system A2B7-type electrode alloys, La in the alloy was partially substituted by Zr. The melt-spinning technology was used for preparing La0.75−xZrxMg0.25Ni3.2Co0.2Al0.1(x = 0, 0.05, 0.1, 0.15, 0.2) electrode alloys. The influences of both the substitution of Zr for La and the melt spinning on the structures and the electrochemical cycle stability of the alloys were investigated in detail. The structure analysis of XRD, SEM and TEM reveals that the as-cast and spun alloys have a multiphase structure, composing of two main phases (La, Mg)2Ni7and LaNi5as well as a residual phase LaNi2. The substitution of Zr for La facilitates to form a like amorphous structure in the as-spun alloy without altering the structures of two major phases. The electrochemical measurement indicates that both the substitution of Zr for La and the melt spinning remarkably improves cycle stability of the alloys. The capacity retaining rate (S100) of the Zr0.2alloy at 100th charging/discharging cycle is enhanced from 76.69 to 85.18% by growing spinning rate from 0 (as-cast was defined as the spinning rate of 0 m/s) to 30 m/s. And that of the as-spun (10 m/s) alloys is increased from 69.25 to 83.09% by rising Zr content from 0 to 0.2.

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Observations on the Structure of Ta2O5

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095959 ◽

1972 ◽

Vol 30 ◽

pp. 540-541

Author(s):

P. S. Kotval ◽

C. J. Dewit

Keyword(s):

Electron Microscope ◽

Structural Features ◽

Amorphous Structure ◽

Polished Surface ◽

Distilled Water ◽

Anodic Films ◽

Amorphous Films ◽

Beam Heating ◽

Diffraction Patterns ◽

Hexagonal Arrays

The structure of Ta2O5 has been described in the literature in several different crystallographic forms with varying unit cell lattice parameters. Earlier studies on films of Ta2O5 produced by anodization of tantalum have revealed structural features which are not consistent with the parameters of “bulk” Ta2O5 crystalsFilms of Ta2O5 were prepared by anodizing a well-polished surface of pure tantalum sheet. The anodic films were floated off in distilled water, collected on grids, dried and directly examined in the electron microscope. In all cases the films were found to exhibit diffraction patterns representative of an amorphous structure. Using beam heating in the electron microscope, recrystallization of the amorphous films can be accomplished as shown in Fig. 1. As suggested by earlier work, the recrystallized regions exhibit diffraction patterns which consist of hexagonal arrays of main spots together with subsidiary rows of super lattice spots which develop as recrystallization progresses (Figs. 2a and b).

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Decoration technique and surface physics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010932x ◽

1978 ◽

Vol 36 (1) ◽

pp. 436-437 ◽

Cited By ~ 1

Author(s):

H. Bethge

Keyword(s):

Diffusion Path ◽

Special Importance ◽

Surface Physics ◽

Step Structure ◽

Initial Stage ◽

Special Cases ◽

Atomic Surface ◽

The Mean ◽

Bulk Structure ◽

Decoration Technique

Besides the atomic surface structure, diverging in special cases with respect to the bulk structure, the real structure of a surface Is determined by the step structure. Using the decoration technique /1/ it is possible to image step structures having step heights down to a single lattice plane distance electron-microscopically. For a number of problems the knowledge of the monatomic step structures is important, because numerous problems of surface physics are directly connected with processes taking place at these steps, e.g. crystal growth or evaporation, sorption and nucleatlon as initial stage of overgrowth of thin films.To demonstrate the decoration technique by means of evaporation of heavy metals Fig. 1 from our former investigations shows the monatomic step structure of an evaporated NaCI crystal. of special Importance Is the detection of the movement of steps during the growth or evaporation of a crystal. From the velocity of a step fundamental quantities for the molecular processes can be determined, e.g. the mean free diffusion path of molecules.

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Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117339 ◽

1985 ◽

Vol 43 ◽

pp. 52-53

Author(s):

G. M. Michal ◽

T. K. Glasgow ◽

T. J. Moore

Keyword(s):

Austenitic Steel ◽

Room Temperature ◽

Elevated Temperatures ◽

Large Range ◽

Amorphous Structure ◽

Nucleation And Growth ◽

Ni Alloys ◽

Melt Spun ◽

Crystal Fibers ◽

Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

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200kv superconducting cryo electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127645 ◽

1987 ◽

Vol 45 ◽

pp. 642-643

Author(s):

M. Iwatsuki ◽

Y. Kokubo ◽

Y. Harada ◽

J. Lehman

Keyword(s):

Electron Microscope ◽

Structure Analysis ◽

Organic Materials ◽

Strong Interactions ◽

Specimen Preparation ◽

Great Effort ◽

Electron Microscopic ◽

Crystal Fields ◽

Special Skill ◽

Long Time

In recent years, the electron microscope has been significantly improved in resolution and we can obtain routinely atomic-level high resolution images without any special skill. With this improvement, the structure analysis of organic materials has become one of the interesting targets in the biological and polymer crystal fields.Up to now, X-ray structure analysis has been mainly used for such materials. With this method, however, great effort and a long time are required for specimen preparation because of the need for larger crystals. This method can analyze average crystal structure but is insufficient for interpreting it on the atomic or molecular level. The electron microscopic method for organic materials has not only the advantage of specimen preparation but also the capability of providing various information from extremely small specimen regions, using strong interactions between electrons and the substance. On the other hand, however, this strong interaction has a big disadvantage in high radiation damage.

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Profile Imaging of Silicon Surface Reconstructions

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118229 ◽

1985 ◽

Vol 43 ◽

pp. 262-263

Author(s):

O.L. Krivanek ◽

G.J. Wood

Keyword(s):

Electron Microscopy ◽

Surface Structure ◽

Structure Determination ◽

Silicon Surface ◽

Good Resolution ◽

Surface Reconstructions ◽

Bulk Structure ◽

Point To Point ◽

The Relationship

Electron microscopy at 0.2nm point-to-point resolution, 10-10 torr specimei region vacuum and facilities for in-situ specimen cleaning presents intere; ing possibilities for surface structure determination. Three methods for examining the surfaces are available: reflection (REM), transmission (TEM) and profile imaging. Profile imaging is particularly useful because it giv good resolution perpendicular as well as parallel to the surface, and can therefore be used to determine the relationship between the surface and the bulk structure.

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