bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Fe Layer Width on the Electron Structure of Ferromagnetic Face Centered Tetragonal Fe-Cu Multilayers
Authors: Lloyd SJ , Dunin-Borkowski RE 
Published: July 2020

Abstract
The mean specimen potentials across a series of short period coherent face centered ferromagnetic Fe-Cu multilayers, grown on (001) Cu by UHV DC magnetron getter sputtering, have been measured using Fresnel contrast analysis1 in the transmission electron microscope. Multilayers A, B and C nominally had 100 repeats of (Fe2/Cu15), (Fe4Cu13) and (Fe6/Cu9) in units of atomic layers, and saturation magnetizations at 0K of 1.7, 0.7 and 0.8μB/Fe atom, respectively. X-ray diffraction measurements showed that the average (002) spacing in each multilayer was much greater than conventional elasticity theory would predict from the bulk elastic constants of face centered Fe and Cu.
Energy-filtered through focal image series of each multilayer (examined in cross-section) were obtained at 397kV using a JEOL 4000FX microscope equipped with a Gatan imaging filter, and a 3.4mrad objective aperture. Fig.1 shows two of the images obtained from multilayer A. The intensity in selected regions of each such image was projected parallel to the layers, the specimen thicknesses (t) of the regions were measured and the contrast of the resulting one dimensional fringe profiles was compared with calculations in order to determine both the shapes and the magnitudes of the potential profiles across the Fe layers.
Characterization of the Interface in a TiC Reinforced Ti-6%A1-4%V Composite Using Monte Carlo Simulations and FEGSEM.
Authors: Gauvin Raynald , Wanjara Priti , Drew Robin AL , Yue Steve 
Published: July 2020

Abstract
Metal matrix composite (MMC) materials are promising materials because of their higher specific mechanical properties (e.g. strength-to-weight ratio) relative to conventional metallic alloys. However, during the processing of these materials, the development of an interfacial reaction zone between the reinforcing material (generally a ceramic) and the metallic matrix may occur, which typically degrades the mechanical properties of these materials if not controlled. Since these interfaces are generally quite small (from 5 to 500 nm), Transmission Electron Microscopy (TEM) is the technique of choice for characterization because of its outstanding spatial resolution. However, specimen preparation for TEM (e.g. ion milling) is quite difficult for MMC materials, due to the combination of two completely different material types, specifically a hard and brittle reinforcement phase incorporated in a relatively soft metallic matrix. Also, since there is only a small amount of the material which is transparent to electrons after specimen preparation, TEM as a materials characterization technique suffers from a lack of statistical robustness, which is a serious drawback.
To characterize materials with a spatial resolution close to that of TEM, low voltage field emission scanning electron microscopy is an option because of the small interaction volume of low energy electrons, as well as the small probe size of these microscopes (typically &lt; 5 nm).
Application of Crystal Orientation Mapping to Intra-Grain Misorientations
Authors: Davies Robert , Randlè Valerie 
Published: July 2020

Abstract
Crystal orientation mapping (COM), which is also referred to as orientation imaging microscopy (OIM), is a powerful tool which opens up enormous possibilities for investigation of materials. The principle of COM is that the microstructure is displayed or mapped according to the orientation of sampled volumes of crystal. These data are obtained in the scanning electron microscope by moving either the electron beam or the specimen stage through predetermined steps and collecting an electron back-scatter diffraction (EBSD) pattern. Typically, a null orientation is represented by a black pixel and colours are used to depict orientations, thus allowing discrete orientation changes such as grain boundaries to be plotted directly in a map format. This is exemplified in figure 1 which shows an orientation map generated from pure aluminium which has undergone 5% cold rolling. The diffiiseness of EBSD patterns further permits strain changes to be mapped.
Chemical Restructuring of Metal Surfaces Studied by Scanning Tunneling Microscope (STM)
Authors: Tanaka Ken-ichi 
Published: July 2020

Abstract
Metal surfaces undergo structural change by the dissociative adsorption of O2, where the reconstructuring is caused by either of the two distinctive mechanisms depending on the temperature and/or the crystalographic planes, one is the “adsorption induced reconstruction” and the other is the “formation of quasi-compounds and their array over the surface”.
The oxygen induced reconstruction of Cu(100) is the former case. When a Cu(100) surface is exposed to O2, oxygen atoms are adsored by making nano-size c(2x2) structure to avoid the convergence of the stress induced by the adsorption. When the oxygen coverage exceeds a critical value of ca 0.3 ML, Cu atoms are missed from the substrate surface to release the stress and the R45 reconstruction is established. In contrast to the Cu(l00) surface, an entirely different process takes place on a Cu( 110) surface exposed to O2, where the (-Cu-O-) string is formed and by a chemical array over the terrace occur.
Formation of Novel Cluster Compounds from Ternary Molybdenum Oxides by In- Situ Deintercalation
Authors: Ramlau R , Simon A , McCarley R E 
Published: July 2020

Abstract
Comprehensive studies by HREM, SAED, and EDXS have been recently devoted to the real structure of the ternary reduced molybdenum oxides in the series Mn±δMo4n+2O6n+4 with M = Sn,In. These compounds contain condensed clusters Mo4n+2O8n+10 with a core of n transedge-sharing molybdenum octahedra. The individual clusters are interconnected via common oxygen atoms. of course, the appropriate choice of counter-cations M is essential for the stability of the clusters, whose core of condensed molybdenum octahedra is a more or less extended metal-metal bonded structure. In tin oxomolybdates condensed clusters with n = 2,3 have been observed, in indium oxomolybdates with n = 3,4,5,6. In Sn2Mo10O16 and Sn2.8Mo14O22 each Sn atom provides 2 electrons to the cluster, in In5Mo18O28, e.g., with n = 4 an In5 7+ polycation, a metal-metal bonded unit itself, provides 7 electrons.
It became obvitalicous that both tin and indium oxomolybdates undergo a structure transformatitalicon when irradiated a 300kV electron mitaliccroscope (Philips CM30/ST, Cs = 1.15mm).
Size-Dependent Equilibrium Shapes of Solid Pb Inclusions in Al
Authors: Dahmen U , Johnson E , Xiao SQ , Paciornik S , Johansen A 
Published: July 2020

Abstract
Small Pb inclusions in Al have been studied by a number of investigators because the alloy system offers the possibility of observing the processes of melting and solidification directly. Both solids are fee, and the mutual solubility of solid Pb and Al is negligible. Despite a large difference in lattice parameter, it has been found that inclusions follow a parallel-cube orientation relationship and their equilibrium shape is a cuboctahedron, bounded by ﹛111﹜ and ﹛100﹜ facets [1]. Following Herring, the relative extent of the two types of facet directly indicates a ratio of interfacial energies γl00/γ111- However, recent investigations have shown that for inclusions in the range of a few to a few tens of nanometers the equilibrium shape becomes a function of size [2].
In the present work, this size dependence of the equilibrium shape has been investigated further. Al alloys with about lat.% Pb were prepared by rapid solidification or by ion implantation, and equilibrated by annealing at about 300°C.
Creation of Stacking Faults at Substrate Steps in Zns Thin Films Epitaxially Grown on GaAs (001)
Authors: Arnold Marcel , Wang ZL , Tong W , Wagner BK , Schön S , Summers CJ 
Published: July 2020

Abstract
Electroluminescence (EL)-based displays are an emerging technology for next generation flat panel displays. ZnS is an important component material for light emitting devices and EL-displays. To make this material useful for high efficiency and low voltage EL applications, the density of dislocations is required to be low. High quality single crystalline ZnS thin films have recently been grown by chemical beam epitaxy [1]. This paper focuses on studying the formation mechanism of stacking faults in the film and its relation with the interface structure between the substrate and the film [2].
Stacking faults are the main defects present in the film (Fig. 1). All four stacking faults (sf) are intrinsic and sf1, growing towards the left-hand side from the interface, is only of short range since after crossing sf2 the defect is terminated by a Shockley partial dislocation and the normal stacking sequence is restored. This is the mechanism that annihilates most of the stacking faults generated from the interface within the first 70 nm thickness range.
Atomic Structure of a Symmetric 27°[001] Tilt Grain Boundary in MgO
Authors: Yan Yanfa , Chisholm M F , Pennycook S J 
Published: July 2020

Abstract
The atomic structure of a symmetric 27° [001] tilt grain boundary in MgO has been determined by high-resolution Z-contrast imaging using a 300 kV VG HB603U scanning transmission electron microscope with a 1.3 Å probe. The atomic configuration in the grain boundary core is found to be considerably less open than the structures proposed earlier for similar materials.
Fig. 1 shows the Z-contrast image of the grain boundary and the projected structure derived from the image. It is clearly seen that the boundary is a shared plane of atoms with the same atomic column density as a bulk crystal {100} plane. The boundary consists of an array of separated perfect edge dislocation cores with Burgers vector b= a&lt;100&gt;. It is interesting to point out that the spacing between dislocation cores in the boundary is not uniform (as seen in Fig. 2). The arrangement, which follows the Fibonacci sequence, can be accurately predicted.
Electronic Structure Studies of Impurities In Fe.
Authors: Alvarez Jose R , Rez Peter 
Published: July 2020

Abstract
Small concentrations of impurities can dramatically change mechanical properties of metals and alloys since they modify bonding and cohesion at grain boundaries. In particular, impurities like B, C, P and S have received considerable attention for their effect on the mechanical properties of Fe. It is known that B and C behave as cohesive enhancers, whereas P and S tend to embrittle iron. Ab initio electronic structure calculations for supercell models of Fe crystals with B, C, P and S impurities have been performed to understand how these impurities modify the electronic states on surrounding atoms The calculations give the charge density distribution, localized densities of states (LDOS) and the total energy of the system. The angular momentum resolved LDOS, when multiplied by slowly varying matrix elements, can be directly related to the experimentally measured electron energy loss near edge structure.
The calculations have been performed using two different methods. One is the Linearized Augmented Plane Wave (LAPW) method, in which the Kohn-Sham equations of density functional theory are self-consistently solved within the Local Density Approximation (LDA) to obtain energies and charge distributions of a crystalline system.
Transformation Twinning and Twinning Crystallography in PrCo2Cx Magnets
Authors: Wu Lijun , Zhu Yimei 
Published: July 2020

Abstract
Pr-Co permanent magnets have attracted much attention recently due to their excellent magnetic properties and low cost; these properties can be further improved by adding small amount of carbon. In this paper, we describe the mechanism of structural transformation resulting from carbon doping in PrCo2 crystals.
We identified the heavily twinned PrCo2Cx (x=0.05-0.25) as a rhombohedral phase with space group Rm. Fig.1 shows its typical morphology of the (110) and (211) primary twins and (110)(211) secondary twins together with the corresponding diffraction patterns. We note that the Bragg spots split along the [hh0]* direction, and that the splitting increases with distance from the [110]* row. The splitting (or α angle of the rhombohedral lattice) also varies with carbon concentration.
Because PrCo2 is an untwinned FCC phase (Fdm), the formation of a twin in PrCo2Cx caused by adding carbon atoms apparently is driven by a minimization in lattice strain, which also is the origin of the cubic-rhombohedral phase-transformation.
Atomic Structure of [110] Tilt Grain Boundaries in FCC Materials
Authors: Merkle L , Thompson L J 
Published: July 2020

Abstract
High-resolution electron microscopy (HREM) has been used to study the atomic-scale structure and localized relaxations at grain boundaries (GBs) in Au, Al, and MgO. The [110] tilt GBs play an important role in polycrystalline fee metals since among all of the possible GB geometries this series of misorientations as a whole contains the lowest energies, including among others the two lowest energy GBs, the (111) and (113) twins. Therefore, studies of the atomic-scale structure of [110] tilt GBs in fee metals and systematic investigations of their dependence on misorientation and GB plane is of considerable importance to materials science. [110] tilt GBs in ceramic oxides of the fee structure are also of considerable interest, since in this misorientation range polar GBs exist, i.e. GBs in which crystallographic planes that are made up of complete layers of cations or anions can join to form a GB.
Thin singlecrystalline films of (110) Au were prepared by vacuum evaporation of Au onto (110) NaCl.
Origin of Robust Superconductivity at Twist Boundary in Bi/2212 Bicrystals
Authors: Bailey GW , Dimlich RVW , Alexander KB , McCarthy JJ , Pretlow TP , Zhu Yimei , Li Q , Tsay YN , Sabatini R , Suenaga M 
Published: July 2020

Abstract
We systematically investigated the structure and properties of [001] twist boundaries using Bi2Sr2CaCu2O8+δ (Bi/22112) bicrystals. Contrary to conventional wisdom, all these boundaries, regardless of their misorientation angle, carried the same critical current as their constituent single crystals in magnetic fields up to 9 tesla. Fig. 1 shows the ratio of the critical currents across a grain boundary to that within the grain interior as a function of misorientation of the boundaries. In striking contrast to the results of Dimos et al. with YBa2Cu3O7−δ, the twist boundaries in our bicrystals are not a limiting obstacle for supercurrent.
The origin of the robust superconducting behavior at these twist boundaries was sought by detailed structural characterization using various TEM techniques. Several notable structural features were observed: 1) all the boundaries were clean, structurally intact without any visible amorphous materials; 2) nano-probe EDS and EELS measurements showed that there was no detectable off-stochiometric composition, including oxygen/hole concentration along and across the boundaries; 3) HREM image simulation revealed that the boundaries were located in the middle of the double BiO layers without exception (Fig.2); 4) there was no detectable boundary expansion, contrary to general expectation, and the inter-planar distance of the double BiO layer {dBio =0.309± 0.005nm, measured with line-scan (Fig.3)) at the boundary was the same as those far from the boundary within measurement error; and 5) very often, there was an intercalation of a Ca/CuO2 bi-layer near the boundary, either on one, or both sides, forming a local Bi/2223 structure (Fig.2).
{111} Planar Faults in a Quenced and Annealed NiAl-0.3Hf Single Crystal Alloy
Authors: Garg A , Noebe R D , Hull D R 
Published: July 2020

Abstract
Quenched-in vacancies, vacancy agglomeration and solute-vacancy association can play a significant role in affecting the mechanical behavior of an alloy. It is well known that B2- NiAl can retain a high supersaturation of thermal vacancies which has been shown to manifest itself as dislocation loops, voids, or spiral dislocations. Dislocation climb loops formed in NiAl have been observed to emanate from impurity particles as concentric {100} loops which are prismatic in nature1. Impurity particles have also been shown to be responsible for nucleating faceted voids. However, addition of alloying elements can alter this mode of vacancy condensation and depending upon the degree of interaction between alloying element and vacancies, a completely different defect structure can result. In a recent study, addition of Boron to Fe-35 mol. % Al has been shown to produce complex {100} planar faults having both APB and stacking fault character, whereas Cr, Pd and W produced APBs on {111} planes.
Observation of Ordered Ti3Al5 Precipitates in Slightly Aluminum Rich γ-TiAl
Authors: Jayanthi S , Wiezorek JMK , Swaminathan S , Fraser HL 
Published: July 2020

Abstract
It is the accepted wisdom that off-stoichiometric TiAl alloys with slightly Aluminum rich compositions, e.g. Ti-52 at.% Al and Ti-54 at.% Al, exist as single phase materials. However, previous studies have reported that Ti3Al5 ordering occurs in Al rich γ-TiAl of compositions 54-63 at.% Al [1,2]. The Ti3Al5 ordering involves the substitution of excess Al into selected Ti sites on the pure Ti plane (001) [1]. In the current work such Ti3Al5 ordering has been observed in TiAl alloys of compositions ranging from Ti-52 at.% Al to Ti-56 at.% Al which have been produced as described in earlier reports [e.g. 3].
Experimental and simulated selected area diffraction patterns (SAD) for the [111] zone axis of TiAl are shown in figure 1. A row of extra reflections which appears between the reflections corresponding to the Ll0 structure are clearly visible in the diffraction patterns obtained from the Ti-54 and 56 at.% Al alloys (Fig. 1b,1c).
HRTEM Study of a Modulated Structure in Homologous Compounds In2O3(ZnO)m
Authors: Bando Yoshio , Li Chunfei , Nakamura Masaki , Kimizuka Noboru 
Published: July 2020

Abstract
The structure of the homologous compounds InMO3(ZnO)m (M=In, Fe, Ga, and Al, m=integer) is considered to be a layered structure, consisting of InO2 1− layer (In-O) ) interleaved with MZnmOm+1 1+ layers (M/Zn-O) along the c-axis. In the M/Zn-O layers, the distribution of two kinds of metal atoms is considered to be random fashion from X-ray diffraction analysis. However, in the previous HRTEM study of InFeO3(ZnO)m with m larger than 6, we found a modulated structure, where the image contrast showed a sinusoidal modulation curve present only in the Fe/Zn-O layers. Elemental analysis by EDS clarified that the modulated structure was caused by the ordering of Fe atoms within the Fe/Zn-O layers. In the present study, we try to observe In2O3(ZnO)m compounds, where Fe3+ atoms are replaced by In3+ atoms which have larger ionic radii. We are interested in whether the replacement of Fe3+ by In3+ atoms may cause any structural changes between In2O3(ZnO)m and InFeO3(ZnO)m.
The samples were prepared by heating powders of In2O3 and ZnO sealed in Pt tube at 1350 °C for about 3 days and then rapidly cooled down to room temperature. The electron microscope observation was performed by using JEM-2000EX, operated at an accelerating voltage of 200 kV.
Microstructural Characterization of Annealed Samples of Pure-Yttria Using Electron Microscopy
Authors: Banerjee S , Gouma P I , Mills M J 
Published: July 2020

Abstract
Yttria is an electroceramic material that has a negative temperature coefficient of resistivity (i.e. it is an NTC type semiconductor). This property, along with its high melting point and good stability, makes yttria a potential sensor material (thermistor) for measuring temperature differences in demanding applications. Recently there has been increasing interesting in studying this ceramic material. How-ever, there is very limited published information on the microstructural characteristics of pure yttria processed under various conditions. Furthermore, reported evidence on the effect of processing conditions on the electrical response of the material is still lacking. Studies within our Center have revealed a correlation between aging time and electrical behaviour in pure yttria samples. The present study examines the evolution of the microstructure of sintered yttria powder during different annealing treatments.
Yttria pellets (6mm diameter, 2mm height) were cold pressed and then sintered at 1550°C for 24h in air. The sintered pellets were then annealed at 1100°C for different times. Specimens for SEM examination were prepared by grinding the surface of the pellets (using grit paper up to 400) and subsequently polishing them using l μm alumina powders.
The Formation Process of the Microstructure of Al2O3-Al3Ti-Al In-Situ Composite
Authors: Luo HH , Wang DZ , Peng HX , Liu Cheng , Yao CK 
Published: July 2020

Abstract
In the last decade, new in-situ processing techniques, such as DIMOX™, XD™, VLS and SHS, for fabricating metal and intermetallic matrix composites have emerged. It is expected that the in-situ formed composites may reveal not only excellent dispersion of fine reinforcing particles, but high thermodynamical stability and high temperature performance. The fully dense Al2O3-Al3Ti-57Vol%Al composite was in-situ processed by combing combustion synthesis with squeeze casting utilizing the reaction between TiO2 powder (with average diameter of 0.6μm and volume fraction of 14%) and pure Al (99.5%). First, the 14Vol%TiO2/Al bulk materials were fabricated via squeeze casting method, subsequently, the TiO2/Al materials were heat treated to form final in-situ composites. Using XRD, SEM, TEM and HRTEM techniques, the microstructure and its evolution were investigated.
The X-ray diffraction pattern of the composite is shown in Fig.1 which indicates that the composite is composed of A12O3, Al3Ti and Al. According to the reaction formula between TiO2 and Al the volume fraction of Al in the composite is about 57%. Fig.2 is a typical scanning electron micrograph of the composite.
The Stability of BN Interfacial Coatings in CFCC Systems During Oxidation and Exposure to Moisture
Authors: Ailey KS , More KL , Lowden RA 
Published: July 2020

Abstract
The mechanical reliability of ceramic matrix composites (CMCs) at elevated temperatures in oxidative environments is primarily dependent upon the chemical and structural stability of the fiber/matrix interface. Graphitic carbon coatings have traditionally been used to control the interfacial properties in CMCs, however, their use is limited in high temperature oxidative environments due to the loss of carbon and subsequent oxidation of the fiber and matrix. Thus, BN is being investigated as an alternative interfacial coating since it has comparable room temperature properties to carbon with improved oxidation resistance. The stability of BN interfaces in SiC/SiC composites is being investigated at elevated temperatures in either flowing oxygen or environments containing water vapor. The effect of several factors on BN stability, including crystallographic structure, extent of BN crystallization, and impurity content, are being evaluated.
Nicalon™ fiber preforms were coated with ≈ 0.4 μm of BN by CVD using BCl3, NH3, and H2 at 1373 K. The coated preforms were densified using a forced-flow chemical vapor infiltration (FCVI) technique developed at ORNL.