Influence of iron impurity interaction in copper-iron dilute magnetic alloy at low temperatures

The electrical conductivity and absolute thermoelectric power of AuSb2 and Cu2Sb have been measured between 2.5° and 300 °K. Room-temperature Hall coefficients were also determined. Iron impurity causes a giant diffusion thermoelectric power at low temperatures in the compound Cu2Sb, as it has previously been found to do in Cu, Ag, and Au.

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Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111458 ◽

1984 ◽

Vol 42 ◽

pp. 268-269

Author(s):

E. Knapek ◽

H. Formanek ◽

G. Lefranc ◽

I. Dietrich

Keyword(s):

Low Temperatures ◽

Carbon Films ◽

Organic Crystals ◽

Wide Spread ◽

Lens System ◽

Preparation Conditions ◽

Thin Carbon ◽

Electron Diffractograms ◽

Diffraction Patterns ◽

Induced Changes

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.

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Radiation Damage of Support Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096862 ◽

1981 ◽

Vol 39 ◽

pp. 28-29

Author(s):

H.A. Cohen ◽

W. Chiu

Keyword(s):

Transfer Function ◽

Low Temperatures ◽

Carbon Support ◽

Contrast Transfer Function ◽

Electron Dose ◽

Imaging Parameters ◽

Negative Stain ◽

Phase Corrections ◽

Two Parameters ◽

Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

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In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113913 ◽

1975 ◽

Vol 33 ◽

pp. 58-59

Author(s):

F. H. Louchet ◽

L. P. Kubin

Keyword(s):

Electron Microscope ◽

Transition Temperature ◽

Low Temperature ◽

Slip System ◽

Low Temperatures ◽

Tensile Axis ◽

Image Intensifier ◽

Screw Dislocations ◽

Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

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Ultrastructure of the soil fungus, Geomyces pannorus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113573 ◽

1984 ◽

Vol 42 ◽

pp. 738-739

Author(s):

J. A. Traquair ◽

E. G. Kokko

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Fine Structure ◽

Low Temperatures ◽

Soil Fungus ◽

Organic Soils ◽

Anatomical Studies ◽

Transmission Electron ◽

Electron Microscopical ◽

Scanning Electron

With the advent of improved dehydration techniques, scanning electron microscopy has become routine in anatomical studies of fungi. Fine structure of hyphae and spore surfaces has been illustrated for many hyphomycetes, and yet, the ultrastructure of the ubiquitous soil fungus, Geomyces pannorus (Link) Sigler & Carmichael has been neglected. This presentation shows that scanning and transmission electron microscopical data must be correlated in resolving septal structure and conidial release in G. pannorus.Although it is reported to be cellulolytic but not keratinolytic, G. pannorus is found on human skin, animals, birds, mushrooms, dung, roots, and frozen meat in addition to various organic soils. In fact, it readily adapts to growth at low temperatures.

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Structure and Orientation of As Precipitates in LT-MBE Grown GaAs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088816 ◽

1991 ◽

Vol 49 ◽

pp. 900-901 ◽

Cited By ~ 1

Author(s):

Alain Claverie ◽

Zuzanna Liliental-Weber

Keyword(s):

Transport Properties ◽

Layer Thickness ◽

Growth Temperature ◽

Low Temperatures ◽

Lattice Parameter ◽

Crystalline Quality ◽

Insulating Properties ◽

Lt Gaas

GaAs layers grown by MBE at low temperatures (in the 200°C range, LT-GaAs) have been reported to have very interesting electronic and transport properties. Previous studies have shown that, before annealing, the crystalline quality of the layers is related to the growth temperature. Lowering the temperature or increasing the layer thickness generally results in some columnar polycrystalline growth. For the best “temperature-thickness” combinations, the layers may be very As rich (up to 1.25%) resulting in an up to 0.15% increase of the lattice parameter, consistent with the excess As. Only after annealing are the technologically important semi-insulating properties of these layers observed. When annealed in As atmosphere at about 600°C a decrease of the lattice parameter to the substrate value is observed. TEM studies show formation of precipitates which are supposed to be As related since the average As concentration remains almost unchanged upon annealing.

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Point and planar defects in the iron sulfide compounds Fe1-xS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011221x ◽

1984 ◽

Vol 42 ◽

pp. 434-435

Author(s):

Thao A. Nguyen

Keyword(s):

Low Temperatures ◽

Direct Evidence ◽

Iron Sulfide ◽

Planar Defects ◽

Selective Area ◽

Vacancy Ordering ◽

Different Types ◽

Lattice Images ◽

The Subject ◽

Beam Lattice

It is well known that the large deviations from stoichiometry in iron sulfide compounds, Fe1-xS (0≤x≤0.125), are accommodated by iron vacancies which order and form superstructures at low temperatures. Although the ordering of the iron vacancies has been well established, the modes of vacancy ordering, hence superstructures, as a function of composition and temperature are still the subject of much controversy. This investigation gives direct evidence from many-beam lattice images of Fe1-xS that the 4C superstructure transforms into the 3C superstructure (Fig. 1) rather than the MC phase as previously suggested. Also observed are an intrinsic stacking fault in the sulfur sublattice and two different types of vacancy-ordering antiphase boundaries. Evidence from selective area optical diffractograms suggests that these planar defects complicate the diffraction pattern greatly.

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Transmission Electron Microscopy of oriented Co84Cr14Ta2 thin films for longitudinal magnetic recording

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088099 ◽

1991 ◽

Vol 49 ◽

pp. 756-757

Author(s):

T. P. Nolan

Keyword(s):

Thin Film ◽

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Low Cost ◽

Low Noise ◽

Information Storage ◽

High Coercivity ◽

Magnetic Alloy ◽

Magnetic Media ◽

Transmission Electron

Thin film magnetic media are being used as low cost, high density forms of information storage. The development of this technology requires the study, at the sub-micron level, of morphological, crystallographic, and magnetic properties, throughout the depth of the deposited films. As the microstructure becomes increasingly fine, widi grain sizes approaching 100Å, the unique characterization capabilities of transmission electron microscopy (TEM) have become indispensable to the analysis of such thin film magnetic media.Films were deposited at 225°C, on two NiP plated Al substrates, one polished, and one circumferentially textured with a mean roughness of 55Å. Three layers, a 750Å chromium underlayer, a 600Å layer of magnetic alloy of composition Co84Cr14Ta2, and a 300Å amorphous carbon overcoat were then sputter deposited using a dc magnetron system at a power of 1kW, in a chamber evacuated below 10-6 torr and filled to 12μm Ar pressure. The textured medium is presently used in industry owing to its high coercivity, Hc, and relatively low noise. One important feature is that the coercivity in the circumferential read/write direction is significandy higher than that in the radial direction.

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Ordering in Ni4Mo by TEM and APFIM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012597x ◽

1987 ◽

Vol 45 ◽

pp. 214-215

Author(s):

E.A. Kenik ◽

T.A. Zagula ◽

M.K. Miller ◽

J. Bentley

Keyword(s):

Electron Irradiation ◽

Low Temperatures ◽

Short Range ◽

Atom Probe ◽

Range Order ◽

Considerable Time ◽

Probe Field ◽

Disordered Phase ◽

Transmission Electron ◽

Diffraction Patterns

The state of long-range order (LRO) and short-range order (SRO) in Ni4Mo has been a topic of interest for a considerable time (see Brooks et al.). The SRO is often referred to as 1½0 order from the apparent position of the diffuse maxima in diffraction patterns, which differs from the positions of the LRO (D1a) structure. Various studies have shown that a fully disordered state cannot be retained by quenching, as the atomic arrangements responsible for the 1½0 maxima are present at temperatures above the critical ordering temperature for LRO. Over 20 studies have attempted to identify the atomic arrangements associated with this state of order. A variety of models have been proposed, but no consensus has been reached. It has also been shown that 1 MeV electron irradiation at low temperatures (∼100 K) can produce the disordered phase in Ni4Mo. Transmission electron microscopy (TEM), atom probe field ion microscopy (APFIM), and electron irradiation disordering have been applied in the current study to further the understanding of the ordering processes in Ni4Mo.

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Point Defect Absorption and Dislocation Loop Formation at Grain Boundaries in Hvem-Irradiated Zr and Its Alloys:1. Influence of Solute Addition

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010011862x ◽

1985 ◽

Vol 43 ◽

pp. 350-351

Author(s):

R.A. Herring ◽

M. Griffiths ◽

M.H Loretto ◽

R.E. Smallman

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Point Defect ◽

Reactor Core ◽

Solute Concentration ◽

Nuclear Industry ◽

Dislocation Loops ◽

Loop Formation ◽

Component Material ◽

Impurity Interaction

Because Zr is used in the nuclear industry to sheath fuel and as structural component material within the reactor core, it is important to understand Zr's point defect properties. In the present work point defect-impurity interaction has been assessed by measuring the influence of grain boundaries on the width of the zone denuded of dislocation loops in a series of irradiated Zr alloys. Electropolished Zr and its alloys have been irradiated using an AEI EM7 HVEM at 1 MeV, ∼675 K and ∼10-6 torr vacuum pressure. During some HVEM irradiations it has been seen that there is a difference in the loop nucleation and growth behaviour adjacent to the grain boundary as compared with the mid-grain region. The width of the region influenced by the presence of the grain boundary should be a function of the irradiation temperature, dose rate, solute concentration and crystallographic orientation.

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