Energy-filtered plasmon images of MgAl2O4 implanted with Al+ and Mg+ ions

1995 ◽  
Vol 53 ◽  
pp. 266-267
Author(s):  
N. D. Evans ◽  
J. Bentley ◽  
S. J. Zinkle
Keyword(s):  
Room Temperature ◽  
Analytical Electron Microscopy ◽  
Fusion Reactors ◽  
High Dose ◽  
Phase Identification ◽  
Magnesium Aluminate Spinel ◽  
Dose Irradiation ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Electron Energy Loss

Magnesium aluminate spinel (MgAl2O4) is a candidate material for specialized applications in proposed fusion reactors, and previously, has been irradiated with Al+ or Mg+ ions to assess the effects of high-dose irradiation. Electron energy-loss spectrometry (EELS) has been used to confirm the identity of metallic aluminum colloids located in the ion-implanted region of the spinel because electron diffraction experiments were inconclusive for phase identification. In the present study, energy-filtered plasmon images of the ionimplanted region have been obtained to reveal this colloid distribution.Following implantation with 2 MeV Al+ ions to a fluence of 3.8 × 1021 ions/m2 at 923 K, or with 2.4 MeV Mg+ to a fluence of 2.8 × 1021 ions/m2 at room temperature, spinel specimens were prepared in cross-section for analytical electron microscopy. Energy-filtered images were obtained using a Philips CM30 microscope with an attached Gatan Imaging Filter. Acquired images were 512 × 512 pixels in size and gain normalized.

Detection limits for Analytical Electron Microscopy with Electron Energy Loss Spectrometry and energy-dispersive x-ray spectrometry

1993 ◽  
Vol 51 ◽  
pp. 594-595
Author(s):  
Dale E. Newbury ◽  
Richard D. Leapman
Keyword(s):  
Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Cross Section ◽  
Analytical Electron Microscopy ◽  
Energy Dispersive ◽  
X Ray ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Electron Energy Loss

The measurement of trace level constituents, arbitrarily defined for this study as concentration levels below 1 atom percent, has always been considered problematic for analytical electron microscopy (AEM) with energy dispersive x-ray spectrometry (EDS) and electron energy loss spectrometry (EELS). In a landmark study of various microanalysis techniques, Wittry evaluated the influence of various instrumental factors (source brightness, detection efficiency, accumulation time) and physical factors (cross section, peak-to-background) upon detection limits. Although the ionization cross section, fluorescence yield, and collection efficiency favor EELS over EDS, the peak-to-background ratio of EELS spectra is much lower than that of EDS spectra, leading Wittry to suggest that the limit of detection should be 0.1 percent for EDS and 1 percent for EELS for practical measurement conditions. Recent developments in parallel detection EELS (PEELS) indicate that a re-evaluation of the situation for trace constituent determination is needed for those elements characterized by "white line" resonance structures at the ionization edge.

Trace Analysis of Nanoscale Materials by Analytical Electron Microscopy

1994 ◽  
Vol 332 ◽  
Author(s):  
Dale E. Newbury ◽  
Richard D. Leapman
Keyword(s):  
Trace Analysis ◽  
Analytical Electron Microscopy ◽  
Beam Current ◽  
Resonance Structure ◽  
White Line ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Trace Constituents ◽  
Electron Energy Loss ◽  
Microscopic Distribution

ABSTRACTTrace analysis of nanometer-scale objects can be performed with parallel-detection electron energy loss spectrometry in the analytical electron microscope. Spectra are collected in the second difference mode with the beam current chosen to maximize the spectral count rate. Numerous elements can be detected at trace levels below 100 parts per million atomic, including transition metal, alkali metal, alkaline earth, and rare earth elements, provided they have a “white line” resonance structure at the ionization edge. Trace nanoanalysis by AEM/PEELS permits direct examination of the microscopic distribution of trace constituents.

Distribution and Characterization of Iron in Implanted Silicon Carbide

1991 ◽  
Vol 235 ◽  
Author(s):  
J. Bentley ◽  
L. J. Romana ◽  
L. L. Horton ◽  
C. J. McHargue
Keyword(s):  
Electron Microscopy ◽  
Silicon Carbide ◽  
Room Temperature ◽  
Analytical Electron Microscopy ◽  
Ion Channeling ◽  
Analytical Electron ◽  
Electron Energy Loss ◽  
Fe Ions

ABSTRACTAnalytical electron microscopy (AEM) and Rutherford backscattering spectroscopy-ion channeling (RBS-C) have been used to characterize single crystal α-silicon carbide implanted at room temperature with 160 keV 57Fe ions to fluences of 1, 3, and 6×1016 ions/cm2. Best correlations among AEM, RBS, and TRIM calculations were obtained assuming a density of the amorphized implanted regions equal to that of crystalline SiC. No iron-rich precipitates or clusters were detected by AEM. Inspection of the electron energy loss fine structure for iron in the implanted specimens suggests that the iron is not metallically-bonded, supporting conclusions from earlier conversion electron Mössbauer spectroscopy (CEMS) studies. In-situ annealing surprisingly resulted in crystallization at 600°C with some redistribution of the implanted iron.

Analytical Electron Microscopy of Precipitates in Ion-Implanted Mgal2O4 Spinel

1994 ◽  
Vol 373 ◽  
Author(s):  
N. D. Evans ◽  
S. J. Zinkle ◽  
J. Bentley
Keyword(s):  
Electron Microscopy ◽  
Energy Loss ◽  
Volume Fraction ◽  
Analytical Electron Microscopy ◽  
Metallic Aluminum ◽  
X Ray ◽  
Electron Energy Loss Spectrometry ◽  
Analytical Electron ◽  
Electron Energy Loss ◽  
Ion Implanted

AbstractAnalytical electron microscopy (AEM) has been used to investigate precipitates in MgAl2O4 spinel implantated with Al+, Mg+, or Fe2+ ions. Experiments combining diffraction, energy dispersive X-ray spectrometry (EDS), electron energy-loss spectrometry (EELS), and energy-filtered imaging were employed to identify and characterize precipitates observed in the implanted ion region. Diffraction studies suggested these are metallic aluminum colloids, although EELS and energy-filtered images revealed this to be so only for the Al+ and Mg+ implantations, but not for Fe2+ ion implantations. Multiple-least-squares (MLS) fitting of EELS plasmon spectra was employed to quantify the volume fraction of metallic aluminum in the implanted ion region. Energy-filtered plasmon images of the implanted ion region clearly show the colloid distribution in the Al+ and Mg+ implanted spinel. Energy-filtered images from the Fe2+ ion implanted spinel indicate that the features visible in diffraction contrast cannot be associated with either metallic aluminum or iron-rich precipitates.

Electron Beam Damage of Biomolecules Assessed by Energy Loss Spectroscopy

1978 ◽  
Vol 36 (3) ◽  
pp. 61-69
Author(s):  
M. Isaacson ◽  
M.L. Collins ◽  
M. Listvan
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Structural Integrity ◽  
Analytical Electron Microscopy ◽  
High Dose ◽  
Dose Rates ◽  
Special Cases ◽  
Analytical Electron ◽  
Atom Migration ◽  
Beam Damage

Over the past five years it has become evident that radiation damage provides the fundamental limit to the study of blomolecular structure by electron microscopy. In some special cases structural determinations at very low doses can be achieved through superposition techniques to study periodic (Unwin & Henderson, 1975) and nonperiodic (Saxton & Frank, 1977) specimens. In addition, protection methods such as glucose embedding (Unwin & Henderson, 1975) and maintenance of specimen hydration at low temperatures (Taylor & Glaeser, 1976) have also shown promise. Despite these successes, the basic nature of radiation damage in the electron microscope is far from clear. In general we cannot predict exactly how different structures will behave during electron Irradiation at high dose rates. Moreover, with the rapid rise of analytical electron microscopy over the last few years, nvicroscopists are becoming concerned with questions of compositional as well as structural integrity. It is important to measure changes in elemental composition arising from atom migration in or loss from the specimen as a result of electron bombardment.

Phase identification in SiC whisker reinforced Al2O3-R2O3-based composites

1992 ◽  
Vol 50 (1) ◽  
pp. 152-153
Author(s):  
C.M. Sung ◽  
K.J. Ostreicher ◽  
M.L. Huckabee ◽  
S.T. Buljan
Keyword(s):  
Analytical Electron Microscopy ◽  
Phase Identification ◽  
Reinforced Composites ◽  
Ion Milling ◽  
X Ray ◽  
Binary Oxides ◽  
Analytical Electron ◽  
The Matrix ◽  
Second Phases ◽  
Convergent Beam

A series of binary oxides and SiC whisker reinforced composites both having a matrix composed of an α-(Al, R)2O3 solid solution (R: rare earth) have been studied by analytical electron microscopy (AEM). The mechanical properties of the composites as well as crystal structure, composition, and defects of both second phases and the matrix were investigated. The formation of various second phases, e.g. garnet, β-Alumina, or perovskite structures in the binary Al2O3-R2O3 and the ternary Al2O3-R2O3-SiC(w) systems are discussed.Sections of the materials having thicknesses of 100 μm - 300 μm were first diamond core drilled. The discs were then polished and dimpled. The final step was ion milling with Ar+ until breakthrough occurred. Samples prepared in this manner were then analyzed using the Philips EM400T AEM. The low-Z energy dispersive X-ray spectroscopy (EDXS) data were obtained and correlated with convergent beam electron diffraction (CBED) patterns to identify phase compositions and structures. The following EDXS parameters were maintained in the analyzed areas: accelerating voltage of 120 keV, sample tilt of 12° and 20% dead time.

Corrections for surface films in microanalysis by EDS and EELS

1992 ◽  
Vol 50 (2) ◽  
pp. 1230-1231
Author(s):  
J. Bentley ◽  
E. A. Kenik
Keyword(s):  
Hydrocarbon Contamination ◽  
Specimen Preparation ◽  
Surface Films ◽  
Ion Milling ◽  
Preferential Sputtering ◽  
Electron Energy Loss Spectrometry ◽  
Composition Determination ◽  
Analytical Electron ◽  
First Order Correction ◽  
Electron Energy Loss

Common artifacts on analytical electron microscope (AEM) specimens prepared from bulk materials are surface films with altered structure and composition that result from electropolishing, oxidation, hydrocarbon contamination, or ion milling (preferential sputtering or deposition of sputtered specimen or support material). Of course, the best solution for surface films is to avoid them by improved specimen preparation and handling procedures or to remove them by low energy ion sputter cleaning, a capability that already exists on some specialized AEMs and one that is likely to become increasingly common. However, the problem remains and it is surprising that surface films have not received more attention with respect to composition determination by energy dispersive X-ray spectrometry (EDS) and electron energy loss spectrometry (EELS).For EDS, an effective first-order correction to remove the contribution of surface films on wedge shaped specimens is to subtract from the spectrum of interest a spectrum obtained under identical conditions (probe current, diffracting conditions, acquisition live time) from a thinner region of the specimen.

The Use of ELNES for Microanalysis

1999 ◽  
Vol 5 (S2) ◽  
pp. 664-665
Author(s):  
A.J. Craven ◽  
M. MacKenzie
Keyword(s):  
Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Analytical Electron Microscopy ◽  
Local Environment ◽  
Edge Structure ◽  
Similar Shape ◽  
Analytical Electron ◽  
Electron Energy Loss ◽  
Combining Information

The performance of many materials systems depends on our ability to control the distribution of atoms on a nanometre or sub-nanometre scale within those systems. This is as true for steels as it is for semiconductors. A key requirement for improving their performance is the ability to determine the distribution of the elements resulting from processing the material under a given set of conditions. Analytical electron microscopy (AEM) provides a range of powerful techniques with which to investigate this distribution. By combining information from different techniques, many of the ambiguities of interpretation of the data from an individual technique can be eliminated. The electron energy loss near edge structure (ELNES) present on an ionisation edge in the electron energy loss spectrum reflects the local structural and chemical environments in which the particular atomic species occurs. Thus it is a useful contribution to the information available. Since a similar local environment frequently results in a similar shape, ELNES is useful as a “fingerprint”.

scholarly journals Effect of high-dose irradiation on quality characteristics of ready-to-eat broiler breast fillets stored at room temperature

2014 ◽  
Vol 93 (10) ◽  
pp. 2651-2656 ◽  
Author(s):  
R.F. Baptista ◽  
C.E. Teixeira ◽  
M. Lemos ◽  
M.L.G. Monteiro ◽  
H.C. Vital ◽  
...  
Keyword(s):  
Room Temperature ◽  
Quality Characteristics ◽  
High Dose ◽  
Dose Irradiation ◽  
Broiler Breast

Quantification of metallic aluminum profiles in Al+ implanted MgAL2O4 spinel by EELS

1991 ◽  
Vol 49 ◽  
pp. 728-729
Author(s):  
N. D. Evans ◽  
S. J. Zinkle ◽  
J. Bentley ◽  
E. A. Kenik
Keyword(s):  
Lattice Parameter ◽  
Dark Field ◽  
Magnesium Aluminate ◽  
Fusion Reactors ◽  
Phase Identification ◽  
Magnesium Aluminate Spinel ◽  
Metallic Aluminum ◽  
Dislocation Loops ◽  
Aluminum Profiles ◽  
Microstructure Of Material

Magnesium aluminate spinel (MgAl2O4) is being considered as an insulator material within fusion reactors because of its favorable damage characteristics. The microstructure of material implanted at 650°C with 2 MeV Al+ ions is shown in cross-section in Fig. 1. Little damage occurs near the surface, whereas at greater depths (0.5 - 1.0 μm) dislocation loops are formed on {110} and {111} planes. Small features thought to be metallic aluminum colloids were observed in the implanted volume near end-of-range. Phase identification by electron diffraction is complicated because the lattice parameter of spinel (0.8083 nm) is almost exactly twice that of aluminum (0.4049 nm). However, the spinel <222> reflection is weak but the aluminum <111> reflection is intense. In <222>sp<111>Al dark-field images of the implanted volume near end-of-range (Fig. 2) the bright 5-10nm diameter features were presumed to be metallic aluminum colloids.

Sign in / Sign up

Export Citation Format

Share Document