bluuebunny/crossref_metadata_2025_split huggingface dataset:
High resolution electron microscopy and atomic positions in gadolinium silicate
Authors: Nissen H.-U. , Wessicken R. 
Published: June 2020

We have investigated the possibilities of imaging atomic positions having distances below 2Å in the example of a silicate, the monoclinic Gd2SiO5 which has a high degree of stability in the electron beam, intermediate cell parameters (a = 9.12, b = 7.06, c = 6.73 Å, β = 107°35', space group P21/c) and two species of atoms (Gd,Si) as main contributors to the contrast. The atomic parameters of the structure used for contrast calculations were given by Smolin and Tkachev (1969).Through-focus series for the projections along [100] and [001] were made for several specimens using a JEM 100 C electron microscope equipped with a high resolution objective pole piece (Yanaka et al., 1974). Powder flakes with platy surfaces show cleavage steps (terraces) along margins, each of which has a rather constant thickness. The contrast pattern varies within a single terrace, most likely as a result of minute differences in orientation due to bending of the crystal flake.
Characteristics of phase contrast in STEM
Authors: Isakozawa S. , Todokoro H. , Nomura S. , Tonomura A. , Komoda T. 
Published: June 2020

Observation of atoms and elemental analysis of micro-area by energy analyzer have been made with our field emission scanning transmission electron microscope(FESTE M), whose point resolution is around o.3nm, and the phase contrast resolution is better than 0.2nm(Fig. 1). With this instrument, the fundamental characteristics of phase contrast images were studied. Especially it is interesting to know if illuminating electron beam can get information of lattice spacing when the spacing is fairly larger than the spot diameter, and the behavior of lattice image by STEM is the same as that obtained by CTEM.In the present experiment, phase contrast, bright field and dark field images are observed under the detecting angles of β1≤ 10-3 rad., β2≤ 10-2 rad. andrad, respectively (Fig. 2).Th-phthalocyanine is selected as a specimen whose lattice spacing (d=1.34nm) is quite larger than the point resolution of the STEM (Fig. 3). The bright and dark field images are found to be almost the same at any defocus, except the reversed contrast
HRTEM observation of stacking and ordered interstratification in rectorite
Authors: Mckee Thomas R. , Buseck Peter R. 
Published: June 2020

Rectorite (=allevardite) is a perfectly ordered mixed layer clay mineral consisting of double layer units of alternating 2:1 (or T-O-T) nonexpandable mica-like and expandable smectite-like 10Å component layers (1,2). Complete dispersion of Na-saturated rectorite results in flakes equal in thickness to the basic unexpanded (20Å) double layer unit. Mixed layered (or interstratified) clay minerals are ubiquitous in both sediments and epithermal deposits; however their routine identification is difficult and is based upon various assumptions concerning their X-ray powder diffraction characteristics. Therefore, rectorite was studied by high resolution transmission electron microscopy (HRTEM) to test existing mixed layering models.Oriented specimens of air-dried rectorite (Fort Sandeman district, Baluchistan, Pakistan) were prepared by three methods: (a) ultrasonic dispersion in acetone, (b) diamond knife ultrathin-sectioning of epoxy embedded dispersions and (c) ion thinning of epoxy embedded aggregates. Dispersed mounts were also prepared after treatment with n-dodecylammonium ions to expand the smectite-like interlayers, producing a double layer repeat of 28Å (3).
High resolution electron microscopy of lanthanum phosphate crystals
Authors: Wheatley J. C. , Cowley J. M. 
Published: June 2020

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).
Structure images of Si, Ge and Mos2 crystals and some application to radiation damage studies
Authors: Izui K. , Nishida T. , Furuno S. , Otsu H. , Kuwabara S. 
Published: June 2020

Recently we have observed the structure images of silicon in the (110), (111) and (100) projection respectively, and then examined the optimum defocus and thickness ranges for the formation of such images on the basis of calculations of image contrasts using the n-slice theory. The present paper reports the effects of a chromatic aberration and a slight misorientation on the images, and also presents some applications of structure images of Si, Ge and MoS2 to the radiation damage studies.(1) Effect of a chromatic aberration and slight misorientation: There is an inevitable fluctuation in the amount of defocus due to a chromatic aberration originating from the fluctuations both in the energies of electrons and in the magnetic lens current. The actual image is a results of superposition of those fluctuated images during the exposure time. Assuming the Gaussian distribution for defocus, Δf around the optimum defocus value Δf0, the intensity distribution, I(x,y) in the image formed by this fluctuation is given by
1 MV super-high-resolution electron microscopy of Nb2O5-WO3complex compounds with TTB type subcells
Authors: Horiuchi Shigeo 
Published: June 2020

It is known that, over a composition range in a Nb2-O5-WO3 system, the crystal structure
of compounds is composed of subcells with tetragonal tungsten bronze ( TIB ) type.) Different models have however been reported for some of them. The crystals are usually prepared in sealed tubes and sometimes show different colours due to a reduction in spite of a definite starting composition. Moreover, they frequently include small domains, which make the structure analysis by x-ray diffraction very difficult. In the present study we examine a series of these compounds, prepared under various conditions, by a super-high-resolution, high-voltage electron microscope ( Hitachi 1250 ),in which the lattice fringes of 2.0 Å in width can be resolved at an accelerating voltage of 1 MV under an axial illumination with equipping a specimen goniometer.2)Fig.l is a crystal structure image of 4Nb2O5.9WO3. According to electron diffractions the lattice parameters are a=12.3, b=36.6 and c=3.94 Å (orthorhombic).
High resolution lattice images of aluminum-copper alloy containing Guinier-Preston zones
Authors: yoshida H. , Hashimoto H. , Yokota Y. 
Published: June 2020

Imaging of atomic structure of sinple crystals such as A1 and Au by the conventional high resolution electron microscope operated at 100 kV is still not very easy, because the lattice spacing of the crystals are smaller than about 2. 3 A, which equivalent to the resolving power of the microscopes. However, if the crystal lattice image is taken at the “Aberration Free Focus” condition(l), the fine structure of the crystal lattice can be photographed. Using this technique, atomic structure arround G.P. zone is studied in the present paper. Since local orientation in the specimen film disturbes the Bragg condition, we did not succeed to observe the atomic structure but could see the lattice fringes, which are formed by the systematic reflection from the crystal position. The fringe position obtained such condition corresponds to the position of atomic rows.Disc specimens were spark-cut from the sheet of an Al-3.97%Cu alloy.
On alloy lattice images
Authors: Boyes E.D. , Gai P.L. , Skarnulis A.J. 
Published: June 2020

The models that are suggested to describe precipitation reactions and phase transformations are almost always on the atomic scale, but the experimental techniques that can be used to examine the phenomena often either integrate the information from many events or operate at somewhat lower resolution. However, phase-contrast lattice imaging and possibly weak beam (Yoshida et al. 1976) techniques of transmission electron microscopy and field-ion microscopy (FIM) (e.g. Boyes et al. 1975 and 1977) can be useful. In principle the images can be interpreted to yield microanalytical data about individual planes or layers of atoms.Images of (200) lattice planes, or more correctly fringes, have been produced from a rolled high purity Aluminium 4.3% Copper alloy containing GP2 or θ" zones. The polycrystalline material is used since the composition is more representative of the applications of this alloy. It was more difficult to produce images of this material than, for example of the visual gold test specimens: it is suggested that this may be due to the increased inelastic cross-sections.
Pipe diffusion along the segment of faulted dislocation loops in aluminum
Authors: Yamaguchi H. , Kawamoto H. , Yoshida S. 
Published: June 2020

The motion of a perfect dislocation loop during annealing was examined by several workers. They proposed a mechanism of pipe diffusion and analyzed this motion. However, these studies on pipe diffusion may have some errors caused by the prismatic glide. In this paper we studied on the motion of faulted dislocation loops under the mutual interaction and estimated the activation energy for pipe diffusion along the dislocation segment of faulted loops.Figure 1 shows schematically a pair of regular hexagonal faulted dislocation loops lying on the (111) plane in quenched aluminum as well as their images observed with an electron microscope, where (a) is the one taken from [001] direction before annealing, (b) and (c) are those taken from [001] and [011] directions after annealing at 95°C for 2 hours, respectively. In order to determine the vector S which connects the center of loop 1 and that of loop 2 in Fig. 1, three different coordinate systems (X1, Y1, Z1), (X2, Y2, Z2), (X3, Y3, Z3) are set up on a specimen, an electron microscope and a micrograph, respectively,(Fig. 2).
Electron microscope studies of climb of dissociated dislocations
Authors: Carter C.B. , Cherns D. , Hirsch P.B. , Saka H. 
Published: June 2020

The mechanism of climb of dissociated dislocations in f.c.c. metals and alloys is not well understood. Climb of dislocations by absorption or emission of vacancies at existing jogs in dissociated dislocations has been observed using the “weak-beam” technique of electron microscopy, but the mechanism of nucleation of jogs is not clear. In this paper we report some results of experiments designed to study the nucleation problem, and more generally the mechanism of absorption of point defects under conditions of high supersaturation.Thin (111) sections of deformed single crystals of Cu-Al alloys, of various compositions, have been electron irradiated in an AEI EM7 HVEM up to 1 MeV, either at room temperature, or elevated temperatures up to 200°C, using a goniometer heating stage. Observations under weak beam conditions have been made a) in situ in the HVEM b) at 100kV in an JEM100B, following irradiation in the HVEM. Interstitials produced by the irradiation are expected to be preferentially attracted to the dislocations because of the strong dislocation-interstitial interaction.
Observations of multipoles in creep deformed 20 Cr 30 Ni steel
Authors: Nilsson J.-O. , Dunlop G. L. 
Published: June 2020

Introduction: Previously, reports have been made on the existence of multipoles in f.c.c. single crystals deformed in easy glide at room temperatures and theories have been developed for their effect on work hardening. It has been suggested that multipoles consist of a series of dipoles held closely together hy interaction of their strain fields (Fig.1) so that often individual dislocations cannot he resolved hy conventional techniques. The present investigation has analysed multipoles which have heen observed in a 20 Cr 30 Ni austenitic stainless steel deformed in creep at 800°C and a tensile stress of 30 MPa.Results and Discussion: An example of multipoles seen in crept material is shown in Fig. 2. Adjacent dislocations in multipoles were identified as having burgers vectors of opposite sign by observing the change in dislocation image spacing obtained with equal and opposite diffracting vectors (+g and -g). An example of this is shown in Fig. 3.
The influence of the vacuum environment on the growth of electron irradiation induced voids
Authors: Buswell J.T. , Baker C. , Rickards G.K. 
Published: June 2020

The variability of the void swelling in nimonic alloy P.E.16 produced by electron irradiation in the high voltage electron microscope has indicated some influence of the vacuum environment on the nucleation and growth of voids.Specimens of double vacuum remelted nimonic alloy P.E.16 prepared under controlled conditions were preheated at 550°C for 1 hour in the microscope and then irradiated at temperature with 1 Mev electrons at a displacement rate of 2 x 10-3 per sec to a total dose of 10 - 20 displacements per atom.Measurement of the vacuum environment around the specimen was made with a Vacuum Generators Micromass 2A mass spectrometer fitted with a long sampling tube extending to within 10cm of the specimen position. Control of the specimen environment was achieved by bleeding in a chosen gas by way of a Leybold leak valve fixed into the side of the specimen chamber so as to introduce the gas to a point within 5cm of the specimen position and on the same plane.
Bending of zirconium thin foils by in-situ ion irradiation
Authors: Parsons J.R. , Gilbert R.W. 
Published: June 2020

In the present experiment the effects of neutron irradiation on zirconium were simulated by an in-microscope ion irradiation of prethinned foils on both sides of which were 60 to 80 Å of room-temperature oxide. Electron microscope observations were made of suitable thin areas prior to irradiation, during irradiation and after each incremental ion dose.Ion Irradiation:- Specimens were irradiated in a Phillips 300 electron microscope with 100 keV oxygen ions emanating from oxide-coated emission filaments. The details involved in the preparation and activation of these filaments have been described elsewhere. Once activated the beam from the filaments consisted of oxygen ions and electrons thus permitting the simultaneous irradiation and observation of the specimen. Both ions and electrons had the same energy as determined by the microscope high voltage selector position. For all irradiations to be described, ions with an energy of 100 keV were used. Determination of the ion flux of approximately 1010to l012 ions cm-2sec-1, depending on the coated filament used, was made with a Faraday cage located just above the microscope final fluorescent screen
Electron microscopy investigation of clusters created in nickel by “in situ” rare gas ion irradiation
Authors: Lerme M. , Ruault M.O. 
Published: June 2020

Irradiations by rare gas ions of 10 to 50 keV have been performed in nickel [10 ppm impurity) at temperatures between 100 and 500 K. The clusters have been observed “in situ” in a conventional electron microscope during irradiation(1).1)Dose effect - Problems of cascade efficiency - For Argon ions of 25 and 50 keV and at irradiation temperatures between 100 and 500 K, the variation of the cluster density as a function of the dose is the same [see fig. 1). Two points are of interest :-the existence of a dose threshold (do) below which no defect is detectable : do ⋍ 1013ions/cm2;the small number of clusters compared to the number of implanted ions [between 1/1000 and 5/1000). This phenomenon has never been observed before for irradiations with metallic ions(2,3).The most likely interpretation is the creation of microclusters [smaller than 10 Å) due to the presence of rare gas ions.
An HVEM study of interstitial loop growth in nickel
Authors: Kosel T.H. 
Published: June 2020

Previous investigators of radiation-induced growth of interstitial loops in nickel have reported observations of rounded Frank loops. Observations of Frank interstitial loops in copper have shown that during growth these loops assume a hexagonal shape with sides lying along <110> directions, due to the splitting of the Frank partial into a Shockley and a stair rod, making jog nucleation more difficult. This splitting should be much less in nickel due to its high stacking fault energy so that jog nucleation should proceed easily, leading to the observed rounded shape. The larger splitting of perfect dislocations should make jog nucleation on perfect loops more difficult than on dissociated Frank loops.In the present work, the observation of rhombus shaped perfect loops growing near rounded Frank loops (Fig. 1) can be explained by the above reasoning. However, the occurrence of a low jog density growth form does not necessarily imply a large departure from diffusion controlled climb rates.
Depth distribution of cavities in 20- and 500-KeV4 He+-irradiated nickel
Authors: Das S. K. , Fenske G. , Kaminsky M. 
Published: June 2020

Studies on depth distribution of damage and of cavities (voids and bubbles) in ion irradiated metals are of importance for an understanding of the mechanisms of radiation blistering and are of general interest to the field of radiation damage.The present paper describes transmission electron microscopy results on depth distribution of cavities and of dislocation damage in nickel irradiated at 500°C with 20- and 500-keV 4He+ ions. The results are compared with calculated projected range and damage energy distributions.High purity (99.995%) annealed polycrystalline nickel foils were irradiated at 500°C with either 20- or 500-keV 4He+ ions to total doses of 2.9 x 1016 and 1 x 1017 ions/cm2, respectively. Thin foils suitable for transmission electron microscopy were prepared from the irradiated samples by a transverse sectioning technique described elsewhere, which allows one to obtain depth distribution of damage and of bubbles from a single specimen.Figure 1 shows typical bright field transmission electron micrographs of the plated and irradiated regions of annealed polycrystalline nickel irradiated at 500°C with 500-keV 4He+ ions to a dose of 1 x 1017 ions/cm2.
Lattice defects in deformed and irradiated Zr3al
Authors: Howe L.M. , Rainville M.H. 
Published: June 2020

Zr3Al is an ordered f.c.c. alloy of the Ll2 type which forms via a peritectoid reaction. It has not been possible to disorder Zr3Al by quenching and no antiphase domain boundaries have been observed, in either annealed or quenched material which indicates that Zr3Al is normally present in a highly ordered state. In deformed Zr3Al the superlattice dislocations were observed to be extended i.e. they consisted of intrinsic stacking faults on {111} bounded by partial dislocations (figure 1). The total Burgers vector is of the type <110> and the superlattice dislocations have dissociated as follows:. The Burgers vectors were determined using the criterion that the partial dislocations will be out of contrast for g.b = 0, ± 1/3 as well as for g.b = -2/3 when s > 0.During high temperature annealing of the deformed material, dislocation networks were produced in which all of the dislocation nodes were extended: hence intrinsic (I) and extrinsic (E) stacking faults must alternate at the nodes (figure 2).
Pulse switching of magnetic films at low temperatures
Authors: Bostanjoglo O. , Gemünd H.P. 
Published: June 2020

Magnetic wall motion is expected to keep below a maximum velocity, about 800 m/s for NiFe films (1). However, previous measurements on extraordinary viscous (2) wall motion (3), did not reveal any maximum velocity. This paper reports on vestigations extending to higher fields than in (3).The wall velocity v in uniaxial 83 at % NiFe films was determined as a function of easy axis magnetic field H and temperature. The field pulse method was used and the wall displacements were detected by electron microscopy within the range of extraordinary viscosity (4... 30 K).The field pulses were generated by a Helmholtz coil (fig. 1) energized by the discharge of a coaxial cable via a pulse shaping spark gap. Rectangular pulses up to 25 kA/m and of widths 10 ns... 3 us with rise/decay time below 15 ns were attained. For cooling the specimen down to 4 K and to minimize distortions of the field due to eddy currents, the specimen holder was a single crystal sapphire, gripped by a high-purity copper holder outside the magnetic field and mounted in a liquid He cooling stage for TEM.
Transformation-induced defects in α-cristobalite
Authors: Lally J.S. , Nord G.L. , Heuer A.H. , Christie J.M. 
Published: June 2020

Transformation-induced twins and antiphase domain boundaries have been observed in both lunar and terrestrial cristobalite. The lunar cristobalite is from mare basalts 12038, 12053 and 70017, whereas the terrestrial material is from San Cristobal, Mexico. All of these samples contained defects resulting from the transformation of the high temperature or β polymorph, usually assumed to be face-centered cubic Fd3m, to α- cristobalite, the low temperature form which is primitive tetragonal P41 212 or P43 22 2. The distribution of defects in all samples is quite heterogeneous; the San Cristobal sample had more defects than the lunar samples. In addition, electron-beam damage is considerably slowed in the lunar cristobalite.Two types of defects were present (Fig. 1). The first consists of twin boundaries which form because any of the three cube axes can become the tetragonal c-axis; this has been previously observed optically and by X-ray diffraction. A second defect consists of domain boundaries (Fig. 2) which appeared to have been produced after the twin boundaries were formed.
The detection of latent nuclear particle tracks in some common minerals with conventional TEM
Authors: Fraundorf P. 
Published: June 2020

Although the first direct photographs of nuclear particle tracks in solids were obtained using a TEM (1), the tendency of the tracks to fade in natural micas under the electron beam, as well as the difficulty of preparing suitably thin samples, resulted in the use of optical and scanning electron microscopy to observe chemically enlarged (etched) tracks in the study of lunar soils and gas-rich meteorites in the early 1970's. However, the possibility of useful applications for conventional (100 kV) TEM in the examination of latent tracks was seldom mentioned.More recently, the emphasis on the study of submicron-sized grains in extraterrestrial materials research has made feasible the use of conventional TEM for ultrastructural studies without the complications of, or need for, ion thinning techniques (e.g. 3, & 4). In the process, many of the minerals examined have shown that latent fission-fragment tracks are easily observed with conventional TEM. The tracks, usually introduced by spontaneous fission from a “thin” Cf2 5 2source, appear to exhibit “density” contrast from a straight core whose average width depends upon the mineral.