Point Defects and Microstructural Stability of Glasses Under Irradiation

1981 ◽  
Vol 6 ◽  
Author(s):  
Marcello Antonini ◽  
Samuel N. Buckley ◽  
Paolo Camagni ◽  
Peter N. Gibson ◽  
Adriano Manara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Relative Number ◽  
Beam Current ◽  
Microstructural Stability ◽  
Dose Rates ◽  
Pure Silica ◽  
Long Term Storage ◽  
Transmission Electron ◽  
Defect Interactions

ABSTRACTThe results of previous optical absorption experiments aiming to investigate the behaviour of atomic defects in silica based glasses irradiated with various types of particles have been extended to examine the effects of multiple irradiations which take place during long term storage of glasses containing HLW. In addition, point defect clustering phenomena have been investigated by means of high voltage transmission electron microscopy. It has been found that due to the large number of defects already present in amorphous silica prior to irradiations, the contributions of different bombarding particles to the total damage cannot be considered fully additive in terms of the relative number of displaced atoms, but some consideration has to be made of defect interactions and ionization damage. Clustering effects, while being absent in pure silica, are present in borosilicates at large dose rates (≳1022 electrons m−2 sec−1 ). At lower beam current densities and doses comparable to those achieved after 10–100 years of HLW storage, phase separation into a microcrystalline compound has been detected by transmission electron microscopy.

Detection efficiency and estimation of the performance of high voltage STEM

1978 ◽  
Vol 36 (1) ◽  
pp. 84-85
Author(s):  
A. Ishikawa ◽  
C. Morita ◽  
M. Hibino ◽  
S. Maruse
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Radiation Damage ◽  
High Voltage ◽  
Detection Efficiency ◽  
Beam Current ◽  
High Energy ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron

One of the problems which are met in conventional transmission electron microscopy (CTEM) at high voltages is the reduction of the sensitivity of photographic films for high energy electron beams, resulting in the necessity of using high beam current. This cancels out an advantage of high voltage electron microscopy which is otherwise expected from the reduction of the inelastic scattering in the specimen, that is the reduced radiation damage of the specimen during observations. However, it is expected that the efficiency of the detector of scanning transmission electron microscopy (STEM) can be superior to that of CTEM, since the divergence of the electron beam in the detecting material does not affect the quality of the image. In addition to observation with less radiation damage, high voltage STEM with high detection efficiency is very attractive for observations of weak contrast objects since the enhancement of the contrast (which is an important advantage of STEM) is easily realized electrically.

scholarly journals Characterization of light-absorbing carbon particles at three altitudes in East Asian outflow by transmission electron microscopy

2013 ◽  
Vol 13 (13) ◽  
pp. 6359-6371 ◽  
Author(s):  
J. Zhu ◽  
P. A. Crozier ◽  
J. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Size Fraction ◽  
Relative Number ◽  
The Yellow Sea ◽  
High Concentration ◽  
Carbonaceous Particles ◽  
Carbon Particles ◽  
Transmission Electron ◽  
Significant Difference

Abstract. The morphology, microstructure, and composition of the submicron fraction of individual light-absorbing carbon (LAC) particles collected by research aircraft during the ACE-Asia (Asian Pacific Regional Aerosol Characterization Experiment) project above the Yellow Sea at altitudes of 120, 450 and 1500 m are investigated by transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Two types of carbonaceous particles, small spherule soot with graphitic spherules and amorphous carbonaceous spheres (brown carbon), are found at all altitudes in high concentration. For soot particles, emphasis of the study is on the component subparticles (spherules). The nanoscopic structures of the small spherule soot show no significant difference at three altitudes although the size distribution of primary spherules showed that 70% of the total volume lies in the ranges 30–50, 50–85 and 30–50 nm, respectively. For the amorphous carbonaceous spheres, 70% of the total volume from three altitudes lies in the range 200–350, 160–470 and 150–320 nm, respectively. Within the size fraction studied (submicron, with most particles in the range 50 to 500 nm) the number concentration ratios of the amorphous carbonaceous spheres to primary spherules in soot at altitudes of 120, 450 and 1500 m are about 1, 1.5 and 10, respectively and their volume ratios are about 260, 50 and 1400. Lower relative concentrations of large spherule soot with intermediate graphitic structure were observed at 120 m. Also, low relative number concentrations of carbon cenospheres were observed at 120 and 1500 m. A key result of the study is that in vertically stratified outflow from East Asia, the character of LAC may have strong variance with altitude thus resulting in optical characteristics that vary with altitude. Also, apparent "aging" of LAC deduced from samples at multiple ground stations may instead reflect differences in the original carbon aerosols.

Irreversible transformation in as-cast FeAl B2-ordered alloy obtained by melt spinning

2000 ◽  
Vol 15 (3) ◽  
pp. 659-664 ◽  
Author(s):  
E. Bonetti ◽  
R. Montanari ◽  
C. Testani ◽  
G. Valdrè
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Melt Spinning ◽  
Al Alloy ◽  
Microstructural Stability ◽  
X Ray Diffraction ◽  
Repeated Heating ◽  
X Ray ◽  
Transmission Electron ◽  
Stage Process

The aim of the work described in the present paper was to investigate the microstructural stability during annealing treatments of a Fe–Al alloy obtained by melt spinning. To this purpose internal friction (IF) and dynamic modulus (Md) measurements were employed, and the results correlated with x-ray diffraction, optical microscopy, and scanning and transmission electron microscopy observations. In particular, the B2-ordered Fe–38A1–2Cr–0.015C–0.003B (in at.%) alloy was studied during repeated heating runs from room temperature to 823 K by IF and Md. The modulus exhibited a broad maximum (in the range of 600–800 K) only in the first run. On the basis of transmission electron microscopy and x-ray diffraction analysis, the irreversible transformation was explained by considering a two-stage process that occurs when vacancies in supersaturation move toward dislocations. The first stage is connected to dislocation locking; the second one is due to annihilation of some vacancies by dislocation climb.

Phase separation in SiO2–TiO2 gel and glassy films studied by atomic force microscopy and transmission electron microscopy

2001 ◽  
Vol 16 (6) ◽  
pp. 1626-1631 ◽  
Author(s):  
A. Karthikeyan ◽  
Rui M. Almeida
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Phase Separation ◽  
Sol Gel ◽  
Force Microscopy ◽  
Pure Silica ◽  
Atomic Force ◽  
Transmission Electron

An investigation of phase separation phenomena in gel and glassy thin films of silica–titania, with TiO2 contents of 20 and 40 mol%, has been carried out by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The thin films were prepared by spin coating of a precursor sol on silicon wafers. Both the TEM measurements (carried out on scrapped thin film flakes) and the AFM measurements (carried out on films coated on the silicon substrates) for samples with different heat treatments suggest that spinodal-like structural inhomogeneities occur in these samples, unlike the corresponding observations in pure silica films, which are known to be homogeneous. Changes in the microstructure of the films have been noticed with the thermal treatment, in agreement with earlier x-ray photoemission studies. The finer characteristic dimensions of the phase separated regions reveal that silica–titania samples prepared by sol-gel processing exhibit a more intimate mixing of the phases.

scholarly journals Characterization of light-absorbing carbon particles at three altitudes in East Asian outflow by transmission electron microscopy

2012 ◽  
Vol 12 (12) ◽  
pp. 32945-32983
Author(s):  
J. Zhu ◽  
P. A. Crozier ◽  
J. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Size Fraction ◽  
Relative Number ◽  
The Yellow Sea ◽  
High Concentration ◽  
Carbonaceous Particles ◽  
Carbon Particles ◽  
Transmission Electron ◽  
Significant Difference

Abstract. The morphology, microstructure, and composition of the submicron fraction of individual light-absorbing carbon (LAC) particles collected by research aircraft during the ACE-Asia project above the Yellow Sea at altitudes of 120, 450 and 1500 m are investigated by transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Two types of carbonaceous particles, small spherule soot with graphitic spherules and amorphous carbonaceous spheres (brown carbon), are found at all altitudes in high concentration. For soot particles, emphasis of the study is on the component subparticles (spherules). The nanoscopic structures of the small spherule soot show no significant difference at three altitudes although the size distribution of primary spherules showed that 70% of the total volume lies in the ranges 30–50, 50–85 and 30–50 nm, respectively. For the amorphous carbonaceous spheres, 70% of the total volume from three altitudes lies in the range 200–350, 160–470 and 150–320 nm, respectively. Within the size fraction studied (submicron, with most particles in the range 50 to 500 nm) the number concentration ratios of the amorphous carbonaceous spheres to primary spherules in soot at altitudes of 120, 450 and 1500 m are about 1, 1.5 and 10, respectively and their volume ratios are about 260, 50 and 1400. Lower relative concentrations of large spherule soot with intermediate graphitic structure were observed at 120 m. Also, low relative number concentrations of carbon cenosphere were observed at 120 and 1500 m. A key result of the study is that in vertically stratified outflow from East Asia, the character of LAC may have strong variance with altitude thus resulting in optical characteristics that vary with altitude. Also, apparent "aging" of LAC deduced from samples at multiple ground stations may instead reflect differences in the original carbon aerosols.

scholarly journals Mitigation of radiation damage in biological macromolecules via tunable picosecond pulsed transmission electron microscopy

2020 ◽  
Author(s):  
Hyeokmin Choe ◽  
Ilya Ponomarev ◽  
Eric Montgomery ◽  
June W. Lau ◽  
Yimei Zhu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Radiation Damage ◽  
Low Dose ◽  
Beam Current ◽  
Mitigation Strategies ◽  
Biological Macromolecules ◽  
Transmission Electron ◽  
Particle Imaging ◽  
Single Particle Imaging

AbstractWe report mitigation of electron-beam-induced radiation damage in biological macromolecules using rapid, low-dose transmission electron microscopy (TEM) with a new, tunable, retrofittable picosecond pulser. Damage mitigation strategies historically consisted of sample cryoprotection and ultra-low beam current; ultrafast laser-pulsed systems have shown promise, but with day-long acquisition times. We show the first practical, fast, laser-free tunable system, with acquisition of diffraction series in minutes at 5.2 GHz and 10 pA. This is the largest study to date: two materials (C36H74 paraffin and purple membrane), two beam energies (200 keV and 300 keV), two independent microscopes (Schottky and LaB6), two modes (pulsed and continuous), and unsurpassed repetition rate tunability. Critical dose at room temperature doubled versus continuous beam for ∼100 MHz single-electron repetition rates. Results herald a new class of highly-tunable, ultrafast pulsers with future applications in cryogenic electron microscopy (CryoEM), high resolution single particle imaging, and rapid low-dose TEM.

Structural Effects of Radiation Damage in Silica Based Glasses

1981 ◽  
Vol 11 ◽  
Author(s):  
A. Manara ◽  
P.N Gibson ◽  
M. Antonini
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Optical Absorption ◽  
Dose Rate ◽  
Etching Rate ◽  
Borosilicate Glasses ◽  
Structural Effects ◽  
Pure Silica ◽  
Transmission Electron ◽  
Effects Of Radiation

ABSTRACTThe results of recent measurements of optical absorption, etching rate and transmission electron microscopy in pure silica and borosilicate glasses are reported and discussed. At dose saturation conditions, the dependence of the optical density associated with the production of single atomic defects from the mass of the impinging particle shows a marked saturation at masses ≥ 20 amu. The corresponding etching rates increase by about 4 times with respect to unirradiated samples. In borosilicate glasses, the temperature dependence of the threshold dose rate of electrons to initiate the nucleation of bubbles shows a marked increase from about 300° to 600° K.

Focused Ion Beam Milling for Site Specific Scanning and Transmission Electron Microscopy Specimen Preparation

1997 ◽  
Vol 3 (S2) ◽  
pp. 347-348
Author(s):  
L.A. Giannuzzi ◽  
J.L. Drownt ◽  
S.R. Brown ◽  
R.B. Irwin ◽  
F.A. Stevie
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Region Of Interest ◽  
Beam Current ◽  
Specimen Preparation ◽  
Site Specific ◽  
Sem Image ◽  
Transmission Electron

It has been shown that a focused ion beam (FIB) instrument may be used to prepare site specific cross-sectioned specimens to within < 0.1 μm for both scanning and transmission electron microscopy (SEM and TEM, respectively). FIB specimen preparation has been used almost exclusively in the microelectronics industry. Recently, FIB specimen preparation has been utilized for other materials systems and applications.A cross-sectioned SEM specimen is produced by sputtering away a trench of material from near the region of interest. Large amounts of material are sputtered using large ion beam diameters (e.g., l00’s nm) and high beam current (e.g., l000’s pA), while the final sputtering operations are achieved using smaller beam diameters (e.g., < 10 nm) and lower beam current (e.g., 10’s of pA). The SEM specimen may then be etched to reveal particular microstructural features of interest. A low magnification SEM image of a multi-layered device prepared for cross-section analysis by the FIB method is shown in FIG. 1.

The Use of a Cold Gas Plasma for the Final Processing of Contamination-Free Tem Specimens

1997 ◽  
Vol 480 ◽  
Author(s):  
P. E. Fischione ◽  
J. Ringnada ◽  
Y. Feng ◽  
T. Krekels ◽  
M Hayies ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Materials Science ◽  
Analytical Data ◽  
Beam Current ◽  
High Brightness ◽  
Gas Plasma ◽  
Transmission Electron ◽  
Electron Microscopes

AbstractThe issue of specimen contamination becomes more important at a rate proportional to the use of high-brightness electron source Transmission Electron Microscopes (TMM). The trend in the transmission electron microscopy of materials science specimens is to use higher-voltage microscopes incorporating field emission gun technology [1]. These FEG TEMs combine smaller electron probes with increased beam current, allowing high resolution specimen imaging and enhanced analytical data collection. This is of particular importance for semiconductor specimens which demand fine-probe microanalyis.

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