bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron Microscope investigation of crack path selection and crack interface interactions in a W-ZrO2(Y2O3) directionally solidified eutectic (DSE)
Authors: Isabell T.C. , Dravid V.P. , Hill D.N. 
Published: June 2020

Metal-ceramic composites play a vital materials role in many technologically important industries due to their unique electrical, thermal and structural properties. The mechanical properties of metal-oxide materials are largely controlled by the properties of the metal-ceramic interface, specifically its structure and chemistry which govern the bonding between the constituents. For a brittle matrix composite, the fracture properties of the interface can determine the failure response of the composite as a whole.The W-ZrO2(Y2O3) directionally solidified eutectic was grown by a skull melting technique described elsewhere. Composites were grown with 10 mol % yttria and ~ 6 w% tungsten. Figure 1 is a scanning electron micrograph showing that the tungsten grows as parallel fibers approximately lujn in diameter in a zirconia matrix. Selected area diffraction of the composite (Figure 2) reveals the growth direction to be: <110>zrO2 // <11l>w.Electron microscopy of microindentation cracks, of pre-existing microcracks due to thermal expansion anisotropy and of short cracks inadvertently introduced during specimen preparation shows four different crack-interface interactions:
Martensitic transformation in zirconia-alumina nanolaminates
Authors: Gajdardziska-Josifovska M. , Aita C. R. 
Published: June 2020

With an eye towards developing transformation-toughening ceramic coatings, we grew multilayers of polycrystalline zirconia and amorphous alumina in which the layer spacing was scaled to insure nanosize zirconia crystallites. In this manner, nanolaminates with a high volume fraction of tetragonal zirconia (t-ZrO2) were produced, independent of the deposition parameters and without the use of dopants.For a coating to be of practical use, not only must it contain a significant amount of t-ZrO2, but this phase must also transform locally to the monoclinic phase (m-ZrO2) m response to stress. In bulk zirconia-alumina composites, with dopant stabilized tetragonal zirconia, the martensitic t → m transition is auto-catalytic, resulting in widespread transformation of the parent phase. Twinning and slip are the recognized transformation mechanisms. In this work, we study the transformation mechanism in zirconia-alumina nanolaminates using high resolution electron microscopy (HREM).The multilayers were grown by reactive sputter deposition in a multiple target if diode system.1 Si (111) wafers were used as substrates for the multilayers studied by microscopy.
In Situ hot-stage high-resolution Transmission Electron Microscope studies of the mechanisms and kinetics of precipitation reactions
Authors: Howe James M. 
Published: June 2020

In situ hot-stage high-resolution transmission electron microscopy (HRTEM) provides unique capabilities for quantifying the mechanisms and kinetics of precipitation reactions at the atomic level. Such information is required to understand phase transformations and the behavior of material interfaces. This paper provides a brief summary of the in situ hot-stage HRTEM technique and illustrates the use of this technique to obtain information about heterogeneous nucleation processes in precipitation and crystallization reactions. Examples of other types of in situ HRTEM studies can be found in previous papers by Sinclair et al. and Howe et al.The specimen and microscope requirements for in situ hot-stage HRTEM are the same as those for static HRTEM except that one must have a hot-stage specimen holder and equipment for recording and analyzing dynamic images. A high-resolution television-rate camera connected to a standard videocassette recorder (VCR) can be used to store hours of data for low cost. The dynamic images can then be analyzed directly during playback or sent to a computer for image processing and analysis.
Analytical ultra high-voltage Electron Microscope equipped with EDS and energy-filtered imaging system at NRIM
Authors: Furuya K. , Osaki M. , Hagiwara S. , Saito T. 
Published: June 2020

The ultra high voltage transmission electron microscope (UHV-TEM) having an acceleration voltage of 1000 kV or more has been used for the observation of atomic structure of materials because of its high resolution approaching to 0.1 nm. Few effort has been done to develop an analytical UHV-TEM with energy dispersive x-ray spectroscope (EDS) for in-situ experiments such as ion irradiation, because high density of hard x-ray accompanied with primary electrons is supposed to prevent to measure the characteristic x-ray from the specimen. However, the observation of the heterostructures and interfaces requires analytical capability of determining the local chemical composition compatible with high resolution electron microscopy. This paper describes about a new analytical UHV-TEM (AHV-TEM) equipped with EDS and energy filtered imaging system and its application to Ni silicide thin film.The AHV-TEM in this study is based on JEM-ARM1000 with a side entry goniometer. Figure 1 shows the comparison of calculated CTF and optical diffractogram of amorphous Ge taken near Scherzer defocus with E=1000 keV, Cs=2.6 mm, Cc=3.4 mm and Qi=0.3 mrad.
Where are the limits to spatial resolution in the HRTEM?
Authors: O'Keefe Michael A. 
Published: June 2020

In discussing resolution limits, it is important to distinguish between the resolution of a microscope and the resolutions of the images produced by the microscope. The spatial resolution of a high-resolution transmission electron microscope (HRTEM) is an upper bound on the resolution of images that can be produced by that microscope, but there is no guarantee that any particular image from the microscope will attain this bound. In addition to instrumental limits, properties of the specimen will act to degrade image resolutions. For specimens that beam-damage rapidly, image resolution depends upon electron energy and electron dose. For small-cell crystalline specimens, Bragg's law mandates that allowable resolutions be quantized, preventing image resolution from reaching microscope resolution. However, improving the resolution of a HRTEM gives it the capability to produce higher resolution images.Image “resolution” is a measure of the spatial frequencies transferred from the image amplitude spectrum (specimen exit-surface wavefunction) into the image intensity spectrum (Fourier transform of the image intensity).
Practical limits on the spatial resolution in energy-filtered mapping
Authors: Crozier P.A. 
Published: June 2020

One parameter of importance in energy-filtered elemental mapping is the achievable spatial resolution. In practice, the resolution in a particular experiment depends on the energy loss used to form the image. Moreover, the importance of critical factors for defining the resolution, namely quantum localization, chromatic aberration and statistics, change with energy loss.The fundamental limit on the spatial resolution in any energy-loss experiment is determined by the localization of the inelastic scattering process. Kohl and Rose (1985) have undertaken detailed quantum mechanical calculations of the influence of inelastic scattering on high resolution images. Fig 1 shows the results from these calculations for the change in spatial resolution as a function of energy loss for typical experimental conditions on the Zeiss 912.Chromatic aberration in the electron optical column causes electrons of different energy to be focused in different planes causing image blurring. The resulting diameter d of the disk of least confusion depends on the energy and angular spread of the beam through the equation:
Impurities and grain boundaries in sintered titanium diboride
Authors: Pettersen G. , Bardal A. , Høier R. 
Published: June 2020

In conventional Al-electrolysis the electrodes suffer from degradation when used in the harsh environment of an aluminium electrolysis cell. The carbon cathode, which is placed at the cell bottom, is not well wetted by aluminium, and must be covered by a pad of liquid Al in order to establish a good electrical contact. To avoid short circuiting of the cell the anode-to-cathode distance (ACD) must be kept above 4-6 centimetres. Replacing the carbon cathode with a new, inert cathode, well wetted by liquid aluminium, would allow new cell designs where only a thin film of aluminium covers the cathode during cell operation, thereby allowing the ACD to be lowered. This in turn opens for substantial reductions in the energy consumption of an electrolysis cell, and combined with an inert anode the outlet of CO2 and fluorides harmful to the environment could be reduced.The most promising candidate for use as an inert cathode is titaniumdiboride (TiB2), a ceramic material which exhibits promising properties such as a high electrical conductivity, sufficient mechanical strength, good resistance to chemical attack and low solubility in liquid aluminium, and which is also well wetted by liquid aluminium.
Characterization of modified ceramic fiber surfaces using AFM
Authors: Amold C. L. , More K. L. , Lara-Curzio E. 
Published: June 2020

Several models have been developed to describe the interfacial behavior of fiber-reinforced ceramic matrix composites. However, these models are limited in that they do not take into account the effect of fiber surface roughness on the fiber sliding resistance. Clearly, the fiber surface roughness will play an important role in extensive fiber/matrix debonding and fiber pull-out behavior which are characteristic of a toughened composite. In this study, a Topometrix TMX2010 Atomic Force Microscope (AFM) was used to quantitatively evaluate the surface topography of a SiC fiber subjected to a series of surface modification treatments. The relationship between interfacial properties determined from fiber push-out tests and the surface roughness will be used to modify existing mathematical models.In order to systematically study the effect of surface roughness on the interfacial properties of ceramic matrix composites, a “model” single fiber composite having varying degrees of fiber surface roughness was developed. This was accomplished by using a single manufacturer's ceramic fiber which was subjected to a series of treatments in order to alter the surface.
High-resolution TEM study of ion beam irradiation induced amorphization in ceramic materials
Authors: Wang L.M. , Ewing R.C. , Weber W.J. 
Published: June 2020

Radiation damage of nuclear materials (e.g. fast- or fusion-neutron damage in reactor structural components, fission-fragment damage in nuclear fuels and alpha decay damage in nuclear waste forms) has been one of the major challenges faced by the material science community. Ion beam irradiation and implantation experiments have been used extensively in the past few decades not only for simulating these damaging process in materials but also for improving material properties for many technological applications.As an energetic particle traverses a crystalline target, it loses its energy predominantly through electronic (ionization) and nuclear (elastic collision) interactions with the atoms in the lattice. The target atom which receives sufficient energy from the interactions may get displaced from its lattice site and may further displace other target atoms, thus creating a displacement cascade which is usually a few nanometers in scale. Just at the end of the collision phase, which lasts for only a few tenths of a picosecond, a displacement cascade contains a very dense cluster of point defects and the region may be considered amorphous.
Crystal structure of Tl-substituted HG-1223 superconductor with critical temperature of 138K under atmospheric pressure
Authors: Feng Y. , Larbalestier D.C. , Sun G.F. , Xin Y. , Wong K.W. , Osofsky M.S. , Tom L.E. , Ikeda S. , Fujii H. , Kumakura H. , Togano K. 
Published: June 2020

Since the discovery of the Hg-Ba-Ca-Cu-O superconductors, several members of the system bearing the formula HgBa2Can−1CunO2n+2+x (n=l,2,3) were synthesized. The highest critical temperature Tc of 133.5K under atmospheric pressure was achieved from the Hg-1223 compound (n=3). The Hg-compounds are structurally analogous to the single-layer Tl-based compounds TlBa2Can−1CunO2n+2+x. In Hg-1223, oxygen is almost absent in the Hg-O plane at the stoichiometric (x=0) composition. In contrast, the oxygen sites in the Tl-O plane are nearly fully occupied. The difference in oxygen occupancy of the corresponding rock-salt Hg-O and Tl-O planes in Hg- 1223 and Tl-2223 is due to the difference in valence of Hg2+ and Tl3+.To create a necessary fractional oxygen occupation in the Hg-O planes, a partial substitution of Tl for Hg was carried out and the Tc of the Tl-substituted sample raised up to 138K. We report here on the crystal structure of the new compound. Synthesis and properties has been published elsewhere.
Electron holography of catalysts
Authors: Datye A. K. , Kalakkad D. S. , Allard L. F. , Völkl E. 
Published: June 2020

The active phase in heterogeneous catalysts consists of nanometer-sized metal or oxide particles dispersed within the tortuous pore structure of a high surface area matrix. Such catalysts are extensively used for controlling emissions from automobile exhausts or in industrial processes such as the refining of crude oil to produce gasoline. The morphology of these nano-particles is of great interest to catalytic chemists since it affects the activity and selectivity for a class of reactions known as structure-sensitive reactions. In this paper, we describe some of the challenges in the study of heterogeneous catalysts, and provide examples of how electron holography can help in extracting details of particle structure and morphology on an atomic scale.Conventional high-resolution TEM imaging methods permit the image intensity to be recorded, but the phase information in the complex image wave is lost. However, it is the phase information which is sensitive at the atomic scale to changes in specimen thickness and composition, and thus analysis of the phase image can yield important information on morphological details at the nanometer level.
Observation of grain superstructure in thin aluminum films by orientation imaging microscopy
Authors: Alvis Roger , Dingley David , Field David 
Published: June 2020

The correlation of aluminum alloy reliability data to microstructure has long been the goal of those scientists seeking to model electromigration behavior of interconnects. Traditionally, microstructural information has been acquired through x-ray diffraction , and transmission electron microscopy (TEM). However, each of these techniques is capable of delivering only part of the characterization whole. We describe the application of orientation imaging microscopy (OIM) to thin aluminum alloy films and demonstrate its versatility in providing the key microstructural reliability parameters: namely texture and grain size, as well as providing insight to the microstructure of grain boundaries.OIM was performed on an electromigration test structure (figure 1). The Al-alloy was deposited on titanium and capped with an anti-reflective titanium nitride. Subsequently, the test structure was patterned and capped with a multilayer blanket consisting of silicon nitride (SiN), and SiO2. The structure was annealed after the SOG deposition at 450° C for 90 minutes, seeing no electrical stressing. The die was removed from the package and deprocessed before the OIM was acquired.
Strain measurement in In0.2Ga0.8As/GaAs quantum wires by convergent beam electron diffraction
Authors: Hillyard S. , Chen Y.-P. , Reed J.D. , Schaff W.J. , Eastman L.F. , Silcox J. 
Published: June 2020

The positions of high-order Laue zone (HOLZ) lines in the zero order disc of convergent beam electron diffraction (CBED) patterns are extremely sensitive to local lattice parameters. With proper care, these can be measured to a level of one part in 104 in nanometer sized areas. Recent upgrades to the Cornell UHV STEM have made energy filtered CBED possible with a slow scan CCD, and this technique has been applied to the measurement of strain in In0.2Ga0.8 As wires.Semiconductor quantum wire structures have attracted much interest for potential device applications. For example, semiconductor lasers with quantum wires should exhibit an improvement in performance over quantum well counterparts. Strained quantum wires are expected to have even better performance. However, not much is known about the true behavior of strain in actual structures, a parameter critical to their performance.
Evolution of the microstructure of Cu(Ti)/SiO2 layers annealed in NH3
Authors: Liu J. , Theodore N. D. , Adams D. , Russell S. , Alford T. L. , Mayer J. W. 
Published: June 2020

Copper-based metallization has recently attracted extensive research because of its potential application in ultra-large-scale integration (ULSI) of semiconductor devices. The feasibility of copper metallization is, however, limited due to its thermal stability issues. In order to utilize copper in metallization systems diffusion barriers such as titanium nitride and other refractory materials, have been employed to enhance the thermal stability of copper. Titanium nitride layers can be formed by annealing Cu(Ti) alloy film evaporated on thermally grown SiO2 substrates in an ammonia ambient. We report here the microstructural evolution of Cu(Ti)/SiO2 layers during annealing in NH3 flowing ambient.The Cu(Ti) films used in this experiment were prepared by electron beam evaporation onto thermally grown SiO2 substrates. The nominal composition of the Cu(Ti) alloy was Cu73Ti27. Thermal treatments were conducted in NH3 flowing ambient for 30 minutes at temperatures ranging from 450°C to 650°C. Cross-section TEM specimens were prepared by the standard procedure.
Interpretation of HREM images of m-barium ferrite taken under dynamical scattering conditions
Authors: Kwon Dongchul , Rabenberg Lew 
Published: June 2020

In HREM analyses of extended structural defects in complex compounds, it is desirable to be able to image atomic columns composed of light elements as well as those composed of heavy elements. For the thinnest possible specimens, HREM image contrast tends to be dominated by the heavy elements, however, it is possible to increase the contribution of the light elements to the image by imaging specimens of somewhat greater thicknesses. This paper presents results from a HREM study of extended defects in M-barium ferrite in which this approach has been successfully applied.Hexagonal ferrites, of which M-barium ferrite, BaFe12O19, is an example, form a versatile class of compunds built up from varied stackings of simpler structural units denoted R, S , and T. Mbarium ferrite takes the magnetoplumbite structure - a simple alternation of R blocks and S blocks. HREM techniques have been widely used to charcterize defects in stacking sequences, intergrowths, and polytypes in these materials.
Precipitation of NiHfsi phase in NiAl single crystals containing Hf
Authors: Garg A. , Noebe R. D. , Darolia R. 
Published: June 2020

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.
EELS characterization of “Smut” layer films on steel surface prepared for chrome plating by anodic etching
Authors: Wang E Y. , Cherian J. T. , Madsen A. , Fisher R. M. 
Published: June 2020

Many steel parts are electro-plated with chromium to protect them against corrosion and to improve their wear-resistance. Good adhesion of the chrome plate to the steel surface, which is essential for long term durability of the part, is extremely dependent on surface preparation prior to plating. Recently, McDonnell Douglas developed a new pre-treatment method for chrome plating in which the steel is anodically etched in a sulfuric acid and hydrofluoric acid solution. On carbon steel surfaces, this anodic pre-treatment produces a dark, loosely adhering material that is commonly called the “smut” layer. On stainless steels and nickel alloys, the surface is only darkened by the anodic pre-treatment and little residue is produced. Anodic pre-treatment prior to hard chrome plating results in much better adherence to both carbon and alloy steels.We have characterized the anodic pre-treated steel surface and the resulting “smut” layer using various techniques including electron spectroscopy for chemical analysis (ESCA) on bulk samples and transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) on stripped films.
TEM examination of wear debris from a self-lubricating metal-matrix composite prepared by ultramicrotomy
Authors: Prasad S. V. , Walck S. D. , Lloyd P. F. 
Published: June 2020

Self-lubricating materials are usually multi-phase composites comprising of a solid lubricant dispersed in a matrix of a metal or a polymer. During sliding contact, chemical reactions among the constituent phases of the composite, the counterface and the gases in the surrounding environment are inevitable. The wear debris is a product of such chemical (or tribochemical) reactions. Determination of the chemistry and the crystal structure of the wear debris is therefore crucial to the understanding of the wear mechanisms. In self-lubricating composites, the quantity of the debris generated is often too small to perform x-ray diffraction.It has been previously demonstrated that self-lubricating aluminum metal-matrix composites can be synthesized by dispersing silicon carbide and tungsten disulfide particles in commercial aluminum alloy matrices. A typical microstructure of an Al-0.10SiC-0.05WS2 MMC is shown in Fig. 1. The friction and wear test was performed, in a ball-on-disk configuration, on a polished disk of the aluminum MMC against a 440C steel ball.