bluuebunny/crossref_metadata_2025_split huggingface dataset:
FEISEM of the cell nucleus: A consideration of parameters
Authors: Allen T. D. , Goldberg M. W. , Reipert S. 
Published: June 2020

The wider usage of field emission scanning instruments over recent years has demonstrated their potential to provide useful information on internal cell structure without the necessity to prepare thin specimens in such a way that allows transmission of the electron beam. Resolution of these instruments at around lnm is comparable to that routinely achieved by TEM of biological samples, allowing high resolution surface imaging of intracellular structure. Over the past five years we have been investigating structural organisation of cell nuclei using a Topcon ABT DS130F instrument with a Schottky field emission system which incorporates a Tungsten/Zirconium oxide tip of 0.4μm radius, maintained at 1800°C and 10−8 torr with an extraction voltage of 4,800 volts which generates an emission current of around 60-80 microamps. Specification resolution of this instrument is 1nm at 30kV and 4nms at 1.0kV, using the top stage ‘in lens’ specimen position.After chemical fixation and critical point drying (optimised by maintaining absolute alcohols over molecular sieve and in line filtration of high purity CO2).
Structure of superconducting fibers prepared by laser-heated pedestal growth method
Authors: Cai L.Y. , Huo Y.J. , Mao S.N. , Liu M.L. , Li F.H. 
Published: June 2020

Superconducting fibers have drawn great attention because of the latent prospect for applications. Fibers of superior quality were obtained by means of the laser-heated pedestal growth (LHPG) method. For LHPG method a fine laser beam is focused at the “source rod” made of raw material so that a small molten zone is formed on its upper end. Then a seed crystal is introduced into the melt and drawn from it to grow crystalline fibers. In this paper the structure of bismuth based Bi-Sr-Ca-Cu-O and Bi-Pb-Sr-Ca-Cu-O superconducting fibers prepared by LHPG is reported. The values of Tc for the two kinds of fibers are 85k and 108k respectively. The critical current density Jc can reach 5150A/cm2. The diameters of fibers are ranged from 35μm-200μm. The thin fibers are flexible.Fig.1 shows the transition region between the source rod (R) and the LHPG fiber (G). It indicates that the source crystal first melts and then recrystallizes along a certain cry stenographic direction.
Microstructures of Cu- and Y-rich YBa2Cu3O7−x thin films
Authors: Marshall A.F. 
Published: June 2020

The defect microstructure of Cu- and Y-rich thin films of the high Tc superconductor YBa2Cu3O7−x (123) is of interest for several reasons. The highest Tc' reported for well-ordered stoichiometric films are typically 90-91 K. Post-annealed Cu- and Y-rich films may exhibit Tc's of 95-96 K. X-ray diffraction showed these non-stoichiometric films to be a highly faulted mixture of the 123 and 248 (Y2Ba4Cu8O16,Tc=80 K) phases. In situ films made by sputtering or electron beam evaporation typically show sharp but depressed Tc's (75-85 K); for our films these values approach 90 K when the films are Cu- and Y-rich. Both post annealed and in situ films exhibit high critical currents on and off stoichiometry; the pinning characteristics, which may be highly influenced by the defect microstructure, are superior for the in situ techniques.Transmission electron microscopy analysis shows that excess Cu and Y can be incorporated both as stacking fault (SF) defects and as second phase precipitates.
Texture formation in YBa2Cu3O7−x tapes without a substrate
Authors: Choi Jae-Sung , Javadpour Jafar , Han Chan , Thiel Bradley L. , Sarikaya Mehmet , Aksay Ilhan A. 
Published: June 2020

Texture formation in thin films of YBa2Cu3O7−x has been attributed to epitaxy due to the substrate. However, even in substrates with randomly oriented grains, or substrates which do not provide epitaxy, there is a high degree of c-axis grain alignment in the direction perpendicular to the surface in thin films. In the present study, this texture formation is observed even in tapes which do not have a substrate, We present a model which explains the texture formation in YBa2Cu3O7−x prepared in constrained geometries.The tapes used in this study were prepared by first dispersing the YBa2Cu3O7−x superconducting powder in a medium consisting of methylethylketone, ethylalcohol, menhaden fish oil, and polyvinyl butynal. The stable suspension was then cast onto a mylar surface. The green tapes were heated in air at the rate of 1° C/min to 950° C. After soaking at this temperature for 1 h, the samples were cooled to room temperature at a rate of 1° C/min.
Electron diffraction studies of amorphous and polycrystalline thin films
Authors: Cockayne D J H , McKenzie D R 
Published: June 2020

The study of amorphous and polycrystalline materials by obtaining radial density functions G(r) from X-ray or neutron diffraction patterns is a well-developed technique. We have developed a method for carrying out the same technique using electron diffraction in a standard TEM. It has the advantage that studies can be made of thin films, and on regions of specimen too small for X-ray and neutron studies. As well, it can be used to obtain nearest neighbour distances and coordination numbers from the same region of specimen from which HREM, EDS and EELS data is obtained.The reduction of the scattered intensity I(s) (s = 2sinθ/λ ) to the radial density function, G(r), assumes single and elastic scattering. For good resolution in r, data must be collected to high s. Previous work in this field includes pioneering experiments by Grigson and by Graczyk and Moss. In our work, the electron diffraction pattern from an amorphous or polycrystalline thin film is scanned across the entrance aperture to a PEELS fitted to a conventional TEM, using a ramp applied to the post specimen scan coils. The elastically scattered intensity I(s) is obtained by selecting the elastically scattered electrons with the PEELS, and collecting directly into the MCA. Figure 1 shows examples of I(s) collected from two thin ZrN films, one polycrystalline and one amorphous, prepared by evaporation while under nitrogen ion bombardment.
HREM study of amorphization of CuTi irradiated by 1 MeV electron
Authors: Xu Genbao , Chiou W.A. , Meshii M. , Okamoto P. R. 
Published: June 2020

Electron irradiation-induced amorphization of CuTi was studied by high resolution electron microscopy (HREM). Special attention was directed to correlate the spacial distribution of structural change from the perfect crystalline state to the complete amorphous state with the electron density distribution of the focussed beam which was used to amorphize the specimens.An alloy button of Cu-54 at % Ti was prepared by arc-melting and subsequently annealed at 1173K for three days. HREM samples were spark-cut and thinned by jet polishing. The samples were first examined in a Hitachi H 9000 HREM and selected for irradiation at 10K in a 1.2 MeV Kratos-AEl EM 7 high voltage electron microscope. The irradiation was carried out by a fully focused beam for which the electron density distribution was pre-determined. Finally, the irradiated samples were reexamined across the crystal/amorphous (C/A) boundary in the H 9000. The electron dose at the point of examination was estimated by carefully comparing the positions in HREM images with the interrupted position of bend contour in low magnification and utilizing the electron density distribution.
Electron microscopy of the commensurate-incommensurate phase transition with the discommensuration network in 1T-TaS2
Authors: Ishiguro Takashi , Sato Hiroshi 
Published: June 2020

Phase transitions of lT-TaS2 both on cooling from the incommensurate (IC) phase and on heating from the commensurate (C) phase are investigated by high resolution (HR) transmission electron microscopy because phase transitions are strongly hysteretic. The phases which had been identified were Normal(T>543K,no modurated wave, the Cdl2 type of structure, ao=0.336nm co=0.590nm), IC(354K< T< 543K), NC(non-commensurate or nearly commensurate, 185K<T<353K) and C(T<K). On heating from the C phase, the new phase called the T phase (nearly commensurate triclinic ) appears between 200K and 280K, and that has the discommensuration (DC) network. The HR observations at low temperature reveal both the three dimentional structure of the C phase and the DC network structure of the T phase.On cooling from the IC phase, the structure of the NC phase is essentially incommensurate in the basal plane and a continuous rotation of the moduration direction towards the C phase occurs.
In situ studies on grain boundary migration in ceria-stabilized TZP
Authors: Schmid Herbert K 
Published: June 2020

Tetragonal zirconia polycrystals (TZP) have become of interest due to their exceptionally good combination of mechanical properties. In a previous study the microstructure/microchemistry of grain boundaries (GBs) in CeO2 stabilized ZrO2 (Ce-TZP) was investigated and evidence was found on the existence of vitreous ana crystalline intergranular phases in these ceramics. Recently, the observation of wavy GBs in ceria-zirconia was reported. This phenomenon was attributed to diffusion-induced grain boundary migration (DIGM). In the present work, the in-situ TEM observation of GB migration in Ce-TZP, nominally at room temperature, is reported.Thin foils for TEM observations were prepared from a Ce-TZP ceramic nominally composed of 90 mol% ZrO2 plus 10 mol% CeO2 and were examined in a Philips EM 420 analytical STEM, operated at 120 kV. Grain boundaries were observed to migrate in specimen areas exposed to extensive electron irradiation during TEM experiments. The micrograph in Fig. 1 shows a BF image of a triple grain junction (TJ) area in the as-prepared state.
The value of Electron Microscope studies of imperfect natural diamonds
Authors: Walmsley J C , Lang A R 
Published: June 2020

Interest in the defects and impurities in natural diamond, which are found in even the most perfect stone, is driven by the fact that diamond growth occurs at a depth of over 120Km. They display characteristics associated with their origin and their journey through the mantle to the surface of the Earth. An optical classification scheme for diamond exists based largely on the presence and segregation of nitrogen. For example type Ia, which includes 98% of all natural diamonds, contain nitrogen aggregated into small non-paramagnetic clusters and usually contain sub-micrometre platelet defects on {100} planes. Numerous transmission electron microscope (TEM) studies of these platelets and associated features have been made e.g. . Some diamonds, however, contain imperfections and impurities that place them outside this main classification scheme. Two such types are described.First, coated-diamonds which possess gem quality cores enclosed by a rind that is rich in submicrometre sized mineral inclusions. The transition from core to coat is quite sharp indicating a sudden change in growth conditions, Figure 1. As part of a TEM study of the inclusions apatite has been identified as a major constituent of the impurity present in many inclusion cavities, Figure 2.
Electron Microscopy of hydrothermally treated gamma-alumina
Authors: Mansour S.A. , Halabl M. , Scholz R. 
Published: June 2020

Transmission electron microscopy (TEM) was utilized to study the microstructural changes that take place as a result of treating gamma-alumina extrudates at various temperatures for different treatment times. The value of the study comes from the numerous uses of gamma-alumina, the most important being as a support for catalysts, and from its ability to obtain valuable submicron-level information related to pore structure by TEM. The pore characteristics of the extrudates were controlled through controlling the treatment process. Extrudates were heated in an autoclave at temperatures of 150, 200 and 300°C for treatment times of 1,2,4 and 8h.A JEOL JEM-1200EX transmission electron microscope (TEM) operating at 120 kV was used. The TEM specimens were prepared by crushing the extrudates in a mortar and ultrasonically suspending the fine gamma-alumina powder in alcohol. The suspended particles were deposited on a perforated carbon film supported on a copper grid.
High-Resolution Electron Microscopy of interfaces in TiAl alloys
Authors: Singh S.R. , Howe J. M. 
Published: June 2020

Alloys based on TiAl are being considered as potential candidate materials for advanced aerospace applications. The interphase interfaces and twin interfaces in these alloys play important roles during deformation and can vary with ternary additions. Various HREM studies of interphase interfaces have been made in metallic systems during the last few years. When combined with image simulations, HREM has the capability of revealing local structural and compositional information. This investigation discusses HREM analyses of the crystallography of γ/α2 interfaces, twin interfaces and stacking faults in γ-TiAl with ternary additions of Mn and Ta.The γ-TiAl alloys were solutionized at 1200°C for 2 hrs, isothermally aged for 24 hrs at 900°C in the α2+γ phase field and quenched. Thin foil specimens were polished in a 5% sulphuric acid/methanol electrolyte at -40°C and 20V. The samples were examined in Philips EM420T and JEOL 4000EX microscopes at 120 and 400 kV, respectively. Image simulations were perfomed with the TEMPAS multislice programs, using typical operating conditions for a JEOL 4000EX.
Weak-beam electron microscopy of Σ =3 incoherent twin boundary in SUS316 austenitic stainless steel
Authors: Tanaka Koji , Mori Minoru , Ishida Yoichi 
Published: June 2020

Weak beam (α-fringe) electron microscopy allows one to determine the Burgers vector of a grain boundary dislocation unambiguously. The rigid body translation or excess volume atomic displacements at the boundary between two ajacent crystals may be measured 3 — dimentionally by this method.The specimen was commercial austenitic stainless steel SUS316, which was cold rolled to sheet specimen of about 0.2mm in thickness, annealed at 950°C for 2hr, and was furnance cooled to introduce annealing twins. The annealed specimen was polished electrically in 90% acetic acid and 10% perchloric acid solution at ice water temperature. The polished specimens were observed in a JEM-1250 high voltage electron microscope at 1000keV. The weak beam α-fringe changes only monotonously with displacement at weak beam common diffraction conditions. The translation term R is measured directly from the relative displacement of the extinction contour Δn at the interface. By the standard dynamical theory, the following equation can be derived:
High-resolution imaging of the (111) Ag/Ni interface
Authors: Gao Y. , Merkle K. L. 
Published: June 2020

Computer simulations of Ag/Ni interfaces using embedded atom potentials have predicted that the interfacial energy of the (111) Ag/Ni interface is lowest. However, the semi-coherent interface configuration implied by these calculations has not been confirmed by experimental observation. It is well known that in heterophase systems with small misfit, the misfit is accommodated by misfit dislocations at the interface, forming a semi-coherent interface. However, it is not clear whether or not and to what degree misfit localization will occur at the interfaces with as large a misfit as 14% (Ag/Ni interface). The purpose of this investigation was to examine the atomic structure of the (111) Ag/Ni interface by high-resolution electron microscopy (HREM) and to compare the result to calculated images based on relaxed and rigid models.Metal-metal composite thin films of Ni particles in a Ag matrix were produced by epitaxial growth on (110) NaCl substrates using a special technique described in detail elsewhere. HREM observations were performed using H-9000 at a Northwestern University operated at 300 kV. The images were obtained near optimum defocus without objective aperture. All image simulations were carried out using the multislice method with EMS program package.
Thermal vibrations in simulated ADF STEM
Authors: Loane R. F. , Silcox J. 
Published: June 2020

Thermal vibrations reduce Bragg scattering, create a thermal diffuse background, and disrupt channeling, all of which may affect the ADF STEM signal. There are claims that thermal vibrations can change the relative contrast of different elements in the ADF STEM image, which is different from the simple Z- contrast interpretation. Evaluating the effects of thermal vibrations may be necessary for correct interpretation of experimental results. We present an investigation of ADF STEM imaging including thermal vibrations based on the frozen phonon model.Thermal vibrations can be included in the multislice calculation with a Monte Carlo technique. Since, the interaction time for 100 keV electrons is ≤ 10-4 atomic vibration periods, the atoms may be considered stationary. The time between successive electrons in the STEM is ≥ 102 vibration periods, so the atomic positions seen by different electrons are uncorrelated. The technique is to offset every atom in the specimen (many slices) by a small random amount perpendicular to the beam before performing a standard multislice calculation. A set of random offsets freezes one phonon configuration into the specimen. The calculation is then repeated and averaged over an ensemble of different configurations.
Strain measurements using electron backscattering diffraction patterns
Authors: Dingley D J , Wilkinson A J , Burns G P 
Published: June 2020

The Electron Backscatter Diffraction (EBSP) technique, first applied to the Scanning Electron Microscope by Venables and Harland and later by Dingley et al., is now widely used, particularly for crystal orientation determination , and for the determination of crystal symmetry,. Methods have also been sought to apply it for measurement of internal strain and this paper reviews and reports the findings. Plastic strain measurements from diffraction patterns obtained using the related selected area channelling technique have been widley reported and are reviewed in reference.Elastic and plastic strain in crystals causes a shift in the diffraction line positions, line broadening, and a decrease in diffracted intensity. Measurement of these changes in EBSP is hindered by several problems peculiar to the method. As the patterns are formed by Bragg scattering of initially ine1 astica11y scattered electrons, there is a natural line broadening arising from an energy spread in the diffracted electrons amounting to 1% of the incident beam energy. This is compounded by the fact that the Bragg angle for diffraction is generally less than 2° and that dynamical diffraction effects result in the diffraction profiles being highly assymetric with long tails. Consequently there is considerable overlapp of profiles. Other problems arise from the gnomonic projection of the pattern producing a distortion which increase towards the edges of the pattern and from the need to tilt the specimen towards the recording film which produces further asymmetry in the line profile. Finally, surface contamination is observed to degrade the diffraction pattern reducing line intensity in much the same way as plastic strain.
HRTEM study of valleriite, a hydroxide-bearing copper sulfide
Authors: Wang S. , Buseck P. R. 
Published: June 2020

Valleriite is an unusual mineral, consisting of intergrowths of sulfide layers (corresponding in structure to the mineral smythite - Fe9S11) and hydroxide layers (corresponding to brucite - Mg(OH2)). It has a composition of approximately 1.526[Mg.68Al.32(OH)2].[Fe1.07Cu.93S2] and consists of two interpenetrating lattices, each of which retains its individual structural and diffraction characteristics parallel to the layering. The valleriite structure is related to that of tochilinite, an unusual iron-rich mineral that is of considerable interest for the origin of certain carbonaceous chondrite meteorites and to those of franckeite and cylindrite, two minerals that are of interest because of their unique morphological and crystallographic properties, e.g., the distinctive curved form of cylindrite and the perfect mica-like cleavage with unusual striations and the long-period wavy structure of franckeite.Our selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscope (HRTEM) images of valleriite provide new structural data. A basic structure and a new superstructure have been observed.
Observation of small vacancy detect clusters produced by high- energy collision recoils
Authors: Proennecke Stephan , Victoria Max , Gotthardt Rolf , Horsewell Andy 
Published: June 2020

The observation and analysis of small defect clusters produced by energetic particle irradiation is of importance in understanding the basic mechanisms of radiation damage. Renewed interest in fundamental studies stems from the need to understand very high energy recoil damage typical both of 14 MeV fusion neutrons and spallation neutrons produced around targets in high energy particle accelerators.The defect clusters may be of vacancy or interstitial type. Vacancy clusters occur -as vacancy loops, stacking fault tetrahedra, or three dimensional void embryos. Interstitial clusters occur as interstitial loops or three dimensional clusters. For irradiations carried out at temperatures below that which vacancies are predominantly immobile, analysis of the vacancy component of the total defect cluster population may be used to document the cascade collision processes produced by high energy recoils. The information required is defect cluster type, defect size distribution, and defect density. Since the defects of interest are generally in the size range 0.5 - 5 nm, electron microscopy imaging and analysis techniques are currently being re-assessed.
Defects in ErSi2/Si(111) epitaxial films
Authors: Meneau D'Anterroches C. 
Published: June 2020

Silicides are studied in electronic engineering for their good metallic properties. Among them the group of rare earth silicides shows particular properties. Indeed, some of them, including ErSi2, crystallize in the AIB2 structure although they do not have the exact stoechiometry, their composition being about 1.7. Thus the physical properties and the influence of vacancies on the structure are studied.The film studied in this work was obtained by in-situ annealing, in ultra high vacuum, of a Si-Er film codeposited on a clean Si (111) substrate. Details are given by F. Arnaud d'Avitaya et al. The epitaxial relationship is (111 )Si//(001 )ErSi2 and (112)Si//(100)ErSi2. According to this orientation the lattice mismatch at the interface is - 1.3 %. The films were analysed using high resolution transmission electron microscopy : they are continuous when annealed at 900°C, and show some extra-spots in their diffraction patterns depending on the zone axis. Extra spots were observed along the {111} (3) and {112} zone axes, but not along {110} (4), We will focus in this paper on the {112}Si or {120}ErSi2 zone axis, the corresponding electron diffraction pattern being in Fig. 1.
An Electron Microscopy study of the BaxLa1-xFeO3-x/2 (1/2≤x≤2/3) system
Authors: Parras M. , González-Calbet J.M. , Vallet-Regí M. , Grenier J.C. 
Published: June 2020

In a previous paper we have shown that compositional variations in BaxLa1-xFeO3-y materials prepared in air. are accommodated in a different way than in other perovskite-related ferrites probably due to the bigger size of barium.When oxidated BaxLa1-xFe3+,4+O3-y samples in the 1/2 ≤ x ≤ 2/3 range, are reduced by annealing at 1100°C for 24h. in flowing Ar-5%H2, all iron,as deduced from chemical analysis data, is found in the III state oxidation. Powder X-ray diffraction data in this range (La1/2Ba1/2FeO2.75-La1/3Ba2/3FeO2.67) can be indexed on the basis of a single cubic perovskite unit cell (ac ≃ 3.95Å)In order to elucidate the way in which anionic vacancies are accommodated in these solids an electron diffraction (ED) and microscopy study was performed, similar results being obtained in both La1/2Ba1/2 FeO2.75 and La1/3Ba2/3FeO2.67samples.