Formation of a Ni3O4 Spinel Phase on the Surface of NiO During Electron Irradiation

1988 ◽  
Vol 129 ◽  
Author(s):  
Mary I. Buckett ◽  
L. D. Marks
Keyword(s):  
Surface Science ◽  
Electron Irradiation ◽  
Structural Changes ◽  
Science Studies ◽  
Spinel Phase ◽  
Preparation Conditions ◽  
Variable Voltage ◽  
Resolution Electron ◽  
High Resolution Electron Microscope

ABSTRACTStructural changes occurring at the surface of NiO during electron irradiation were examined in-situ with a variable voltage high resolution electron microscope. The interaction of the specimen with the electron beam was found to be highly dependent on the state of the surface prior to irradiation. It was observed that by varying the sample preparation conditions, the Ni on the surface of NiO could either be oxidized to Ni304 spinel phase or reduced to islands of metallic Ni. The formation of the Ni3O4 spinel phase is in agreement with previous surface science studies, where chemical shift information identified the presence of Ni3+ species at the surface. This has previously been interpreted as the formation of Ni203

HREM In-Situ Studies of Electron Irradiation Effects in Oxides

1988 ◽  
Vol 100 ◽  
Author(s):  
D. E. Luzzi ◽  
L. D. Marks ◽  
M. I. Buckett ◽  
J. W. Strane ◽  
B. W. Wessels ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Point Of View ◽  
Irradiation Damage ◽  
Original Material ◽  
Irradiation Effects ◽  
Resolution Electron ◽  
Wide Range ◽  
Electronic Irradiation ◽  
High Resolution Electron Microscope

ABSTRACTHigh resolution electron microscope (HREM) studies provide the ability to study desorption and sputtering from the perspective of the analysis of the resultant materials, their structure, composition and atomic registry (orientation with respect to the original,material and the irradiation). This is a neglected facet of surface irradiation effects research, yet it is the most important from the technological point of view. In the current study, surface electron irradiation processes in oxides were studied in-situ in a Hitachi H-9000 HREM operated at incident electron energies of 100–300 keV. It was found that a wide range of processes occur in the HREM which are dependent on the energy and flux of the incident electrons and on the material properties. Both ballistic and electronic irradiation damage was observed and the material responses included surface sputtering, amorphisation, chemical disordering, desorption of O and metal surface layer creation, surface roughening and bulk defect creation.

HREM of electron-irradiated silicas

1993 ◽  
Vol 51 ◽  
pp. 1102-1103 ◽  
Author(s):  
L.C. Qin
Keyword(s):  
Electron Irradiation ◽  
Structural Changes ◽  
High Resolution Electron Microscopy ◽  
Nucleation And Growth ◽  
Sharp Boundary ◽  
Quartz Crystals ◽  
Resolution Electron ◽  
Silica Crystals ◽  
Crystalline Matrix

Silica (SiO2) crystals exist in various polymorphs which have different densities and different crystal structures, such as quartz, tridymite, and cristobalite, though all of these have in common the network structure which is formed by corner-sharing of SiO4 tetranedra. All these structures are sensitive to electron irradiation. Amorphization occurs when they are irradiated by energetic electrons.In the present study three polymorphs of silica crystals, α-quartz, α-tridymite and α-cristobalite crystals2 were used as starting materials. Electron irradiation experiments were carried out in situ in the electron microscope. The structural changes of the specimens were monitored using high-resolution electron microscopy (HREM).The amorphization of α-quartz crystals was found to progress through two morphologies: (a) nucleation and growth of amorphous nuclei with a sharp boundary with the crystalline matrix (figure 1); and (b) crystallinity lost gradually and more uniformly. Figure 2 shows a series of HREM images showing the amorphization of a tridymite crystal.

HREM Observations of Deformation Recovery on and Near Surfaces of Eu2O3

1990 ◽  
Vol 48 (1) ◽  
pp. 344-345
Author(s):  
X.G. Ning ◽  
H.Q. Ye
Keyword(s):  
Surface Science ◽  
Electron Irradiation ◽  
Surface Deformation ◽  
Stacking Fault ◽  
Stacking Fault Energy ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
The Right ◽  
Deformation Recovery

Profile imaging technigue has been achieved very much in the field of surface science since it was first proposed. This work will show the deformation recovery on and near the surfaces of Eu2O3 under electron irradiation. The experiment was carried out in a JEOL-200CX high-resolution electron microscope. The Eu2O3 phase has a complex cubic structure with a=1.087 nm. A projected unit cell has been marked in Fig. la. It has been indicated that only Eu3+ ions , which are located in f.c.c. sublattice, appeared in HR images under certain defocus and in the thin areas of specimen. The structural character of Eu2O3 shown by HR images may be analyzed based upon comparing with that of simple f.c.c. structure.It can be seen from Fig. la that the surfaces of Eu2O3 are clean and Eu3+ ions on the (111) surfaces S1 and S2 moved /12 towards to the right (it is actually surface stacking fault). In Fig.lb the stacking fault on S2 was removed under electron irradiation but remained on S1. The stacking fault energy of Eu2O3 is high in the bulk. From Fig.l it can be known that the stacking fault energy may become lower on the (111) surface due to less constrained factors there. This kind of surface stacking fault is related to surface partial dislocations, and both of them may act as the main forms of surface deformation under electron irradiation.

New approaches to characterizing advanced materials

1995 ◽  
Vol 53 ◽  
pp. 74-75
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscope ◽  
Materials Science ◽  
Semiconductor Industry ◽  
Atomic Scale ◽  
Advanced Materials ◽  
Preparation Conditions ◽  
Composition And Structure ◽  
Resolution Electron ◽  
Recent Developments ◽  
High Resolution Electron Microscope

Motivations for using the electron microscope are obviously many and varied. For example, engineers in the semiconductor industry might be primarily interested in establishing reasons for device failure. Chemists in the petrochemical industry could be concerned with analyzing the composition and structure of novel catalytic materials. Many researchers seek to characterize microstructure and establish definitive connections with preparation conditions and/or some pertinent macroscopic behavior. Instrumentation for the high-resolution electron microscope (HREM) has continued to evolve to the extent that imaging on the atomic scale and microanalysis on the sub-nanometer scale are oftentimes available from the same microscope. Such instruments are thus highly attractive to all those people interested in characterizing advanced materials. Our purpose here is to provide a brief overview of some recent developments in instrumentation and techniques and to highlight their relevance for materials science applications.

Onion-Like Nanoscale Structures and Fullerene-Type Cages Formed by Electron Irradiation of Turbostratic Bx.C1-x (x<0.2)

1997 ◽  
Vol 481 ◽  
Author(s):  
D. Golberg ◽  
Y. Bando ◽  
K. Kurashima ◽  
T. Sasaki
Keyword(s):  
Electron Irradiation ◽  
Soap Bubble ◽  
Electron Dose ◽  
Nanoscale Structures ◽  
Linear Dimensions ◽  
Resolution Electron ◽  
Continuous Bending ◽  
High Resolution Electron Microscope ◽  
Electron Energy Loss ◽  
Intense Electron

ABSTRACTFlakes of CVD grown BxC1-x, (x<0.2) films were exposed to intense electron irradiation (flux density up to ∼100 A/cm2) in a 300 kV high resolution electron microscope equipped with a field emission gun. The starting flakes revealed a turbostratic BxC1-x structure. The composition of the starting materials and irradiated products was determined by using electron energy loss spectroscopy (EELS). Depending on the electron dose applied, irradiation of the turbostratic material led to formation of soap-bubble-like irregularly-shaped objects (linear dimensions of ∼2–5 nm), onion- and semi-onion-like structures (d∼10nm), nested fullerenes (3–14 shells) and elementary fullerene-type cages (d∼0.7 nm). It is thought that these curled and closed nanostructures arise from a continuous bending of the hexagonal Bx C1-x sheets under electron irradiation. Finally, some possible structural models of BxC1-x fullerenes are considered.

In Situ Observations of Beam-Induced Effects During High-Resolution Electron Microscopy

1990 ◽  
Vol 201 ◽  
Author(s):  
David J. Smith ◽  
Ping Lu ◽  
M. R. McCartney ◽  
R. Sharma
Keyword(s):  
Electron Irradiation ◽  
Rapid Development ◽  
Compound Semiconductors ◽  
High Resolution Electron Microscopy ◽  
Ex Situ ◽  
Oxidation Reduction ◽  
Resolution Electron ◽  
Irradiation Level ◽  
In Situ Observations

AbstractA variety of electron-beam-induced effects, including oxidation, reduction and surface rearrangements are observed to occur at surfaces of oxides, fluorides and compound semiconductors during electron irradiation within the electron microscope. The extent and type of surface modifications observed are shown to depend upon the irradiation level, the residual microscope vacuum and the specimen temperature. For example, ex situ annealing of compound semiconductors leads to different end-products compared with in situ irradiation, thus showing that residual gas components can have a strong influence on the surface reactions. Electron irradiation of rutile during annealing at high temperature under ultrahigh vacuum conditions caused the rapid development of well-facetted holes without the usual intermediary phase seen at room temperature in conventional vacuum.

scholarly journals First-Principles Characterization and Comparison of Clean, Hydrated, and Defect α-Al2O3 (110) Surfaces

2019 ◽  
Author(s):  
ali abbaspour tamijani ◽  
Jennifer Bjorklund ◽  
Jeffrey Catalano ◽  
Sara E. Mason
Keyword(s):  
Surface Science ◽  
Density Functional ◽  
Chemical Potential ◽  
Surface Preparation ◽  
Experimental Characterization ◽  
Free Energies ◽  
Preparation Conditions ◽  
Thermodynamics Modeling ◽  
Α Al2o3

Structural models of the (110) termination of α-Al2O3 are studied using density functional theory (DFT) calculations and thermodynamics modeling to determine the details of the mineral-water interface structure. It has been established for other facets of both alumina and isostructural hematite that surface preparation conditions can influence the stoichiometry and structure observed during in situ experimental characterization studies. To this end, we use theory and modeling to determine the thermodynamically preferred surface structures as a function of the chemical environment, in terms of the oxygen chemical potential, pressure, and temperature. Consistent with studies of other facets of alumina, we find that thermodynamically unfavorable defect structures, upon hydration and hydroxylation, can show greater stability than the hydrated forms of ideal terminations. The model results are compared to experimental characterization of the hydrated (110) surface, with good agreement in terms of layer spacings and calculated surface-free energies. The electronic structure of the exposed surface functional groups is presented and discussed in terms of structure-reactivity concepts used in geochemical surface science.

In-Situ Tem Dynamic Magnetizing Experiments Used To Identify The Pinning Centers In Hard Magnets Re13.75fe80.25b6 (Re=Nd, Pr).

1999 ◽  
Vol 5 (S2) ◽  
pp. 20-21
Author(s):  
V.V. Volkov ◽  
Y. Zhu
Keyword(s):  
Control Mode ◽  
Objective Lens ◽  
In Situ Tem ◽  
Soft Magnets ◽  
Pinning Centers ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Hard Magnets ◽  
Free Environment

The new JEOL 3000F high resolution electron microscope at BNL has been optimized for Lorentz imaging. The necessary field-free environment around the sample is obtained by switching off the objective lens in the free-lens control mode, and the associated reduction in magnification is compensated for by a Gatan post-column image filter (GIF) at ∼ 20x magnification. Fresnel imaging is obtained by defocusing with objective mini-lens (OM). The use of low angle diffraction with an aperture located at the back focal plane makes it possible to obtain Foucault images.In-situTEM dynamic magnetizing experiments combined with Lorentz magnetrc microscopy both in Fresnel and Foucault modes were used to characterize the magnetic structure of some hard and relatively soft magnets, Nd13.75Fe80.25B6 and Pr13.75Fe80.25B6, prepared by different processing routes. The goal of these in-situexperiments was to develop a reliable and effective procedure to search for, identify, and classify the different pinning centers present in real magnets that accord with their “pinning power” versus applied magnetic field.

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