Using Fluctuation Microscopy to Characterize Structural Order in Metallic Glasses

2003 ◽  
Vol 9 (6) ◽  
pp. 509-515 ◽  
Author(s):  
Jing Li ◽  
X. Gu ◽  
T.C. Hufnagel
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Metallic Glass ◽  
Metallic Glasses ◽  
The Other ◽  
Structural Order ◽  
Transmission Electron ◽  
Medium Range ◽  
Fluctuation Microscopy

We have used fluctuation microscopy to reveal the presence of structural order on length scales of 1–2 nm in metallic glasses. We compare results of fluctuation microscopy measurements with high resolution transmission electron microscopy and electron diffraction observations on a series of metallic glass samples with differing degrees of structural order. The agreement between the fluctuation microscopy results and those of the other techniques is good. In particular, we show that the technique used to make thin specimens for electron microscopy affects the structure of the metallic glass, with ion thinning inducing more structural order than electropolishing. We also show that relatively minor changes in the composition of the alloy can have a significant effect on the medium-range order; this increased order is correlated with changes in mechanical behavior.

Multiple twinning of diamond synthesized by acetylene flame

2004 ◽  
Vol 219 (8) ◽  
Author(s):  
Sam Ick Son ◽  
Su Jin Chung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Back Scatter Diffraction ◽  
The Other ◽  
Hrtem Image ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Multiple Twinning ◽  
Ebsd Method

AbstractThe relation between the domains and domain boundaries of multiple twins of diamond were investigated by the electron back scatter diffraction (EBSD) method and high resolution transmission electron microscopy (HRTEM). Multiple twinned diamonds have two types of icosahedral morphologies. One is an almost perfect icosahedron in which all of the faces are {111} faces. The other is a hollow icosahedron similar to one of the Kepler-Poinsot polyhedrons. The indented negative trigonal faces are formed from the {100} faces of a cube. It was confirmed that the convex edges of the twinned icosahedron corresponded to the Σ3 boundaries, whereas the concave edges were assigned to the Σ9 twin boundary by means of the EBSD analysis.It was confirmed from the HRTEM image that a series of dislocations compensate for the mismatching angle which occurs after five successive twinning.

Observation of Dislocation Cutting Ω Phase and its Strengthening Mechanism in an Al-Cu-Mg-Ag Alloy

1997 ◽  
Vol 3 (2) ◽  
pp. 139-145 ◽  
Author(s):  
Bernard Q. Li ◽  
Franklin E. Wawner
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Strengthening Mechanism ◽  
The Other ◽  
Step Height ◽  
Conventional Transmission Electron Microscopy ◽  
Ω Phase ◽  
Transmission Electron ◽  
High Resolution Tem

Abstract: This investigation presents the interaction of dislocations and semicoherent precipitates (Ω phase) in an Al-Cu-Mg-Ag alloy. The study shows that the semicoherent precipitate is cut by dislocations during deformation. Conventional transmission electron microscopy (TEM) and high resolution TEM (HRTEM) observations demonstrate that shearing of precipitates by dislocations occurs by multiple cutting in the precipitate. The step height caused by cutting on the Ω precipitate is only several atomic layers of the Ω phase. The Ω phase is strengthened after shearing by dislocations. A strengthening mechanism is proposed on the basis of this observation. The strengthening mechanism is not only applicable to the Ω precipitate in Al-Cu-Mg-Ag alloys but also to the other semicoherent precipitates in other alloys.

Edge dislocations in fibrous grunerite

1981 ◽  
Vol 44 (335) ◽  
pp. 287-291
Author(s):  
E. J. W. Whittaker ◽  
B. A. Cressey ◽  
J. L. Hutchison
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Cross Sections ◽  
The Other ◽  
Two Dimensional ◽  
Equal Frequency ◽  
Burgers Vector ◽  
Transmission Electron ◽  
Edge Dislocations

AbstractSections perpendicular to [001] of ion-thinned specimens of fibrous grunerite (amosite) have been examined by high-resolution transmission electron microscopy. In this orientation, two kinds of dislocation have been observed with about equal frequency. One lies on [001] and has a Burgers vector a. The other is on [001] and has a Burgers vector ½a+½b Interpretation of features associated with these dislocations has been assisted by the use of two-dimensional models of I-beam cross-sections which can be interlocked to simulate the possible modes of stacking.

Surface atomie resolution microscopy of sulfated-zirconia and Fe/Mn promoted sulfated zirconia

1996 ◽  
Vol 466 ◽  
Author(s):  
M. Benaissa ◽  
J. G. Santiesteban ◽  
G. Diaz ◽  
M. José-Yacamán
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Sulfated Zirconia ◽  
Tetragonal Zirconia ◽  
The Other ◽  
Transmission Electron ◽  
Mn Species ◽  
Zirconia Phase ◽  
Sulfated Zirconia Catalysts

ABSTRACTBy using high-resolution transmission electron microscopy (HRTEM), it was possible to elucidate edge-on views of the surface atomic structure of sulfated zirconia and Fe/Mn promoted sulfated-zirconia catalysts. The results indicate that the presence of sulfate groups and Fe/Mn species not only stabilizes the tetragonal zirconia phase, but also induces the formation of well-faceted small zirconia crystallites. The shape of the sulfated zirconia crystallites exhibits two types of surfaces: long smooth and relatively few short rough planes, with the long smooth (110) plane being clearly predominant. HRTEM images of this plane revealed the presence of an adsorbed sulfate layer. On the other hand, the presence of Fe and Mn species were apparent on the (001) and (110) surfaces of zirconia particles.

Twinning and defects in N-Nb2O5

2000 ◽  
Vol 56 (5) ◽  
pp. 780-784 ◽  
Author(s):  
Franziska E. Rohrer ◽  
Ann-Kristin Larsson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Stacking Faults ◽  
Twin Plane ◽  
The Other ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Block Arrangement

N-Nb2O5 [C2/m (No. 12), a = 28.51, b = 3.830 and c = 17.48 Å, and β = 124.8°] has been investigated by means of selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). N-Nb2O5 is domain twinned, with the twin plane perpendicular to the c* axis. The domains are rather small and the domain twinning can sometimes be best explained as stacking faults. A second type of coherent twinning at an angle of 90° to the other two domain directions was also found. These domains are linked together by areas containing blocks of different sizes, similar to the disordered block arrangement observed in M-Nb2O5.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

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