bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase stability of a manganese-stabilized austenitic stainless steel
Authors: Kenik E.A. , Maziasz P.J. , Klueh R.L. 
Published: June 2020

Development of manganese-stabilized stainless steels has been prompted by two objectives: (1) replacement of nickel, normally used to stabilize austenitic stainless steels, since it is an expensive, strategic material, and (2) reduction of long-term induced radioactivity of neutron-irradiated stainless steels by replacing nickel, molybdenum, and nitrogen. Klueh et al. have shown that in Fe-Cr-Mn alloys a single-phase austenite exists near Fe-12Cr-20Mn-0.25C (wt %) at high temperatures. Development of more complex alloys based on this composition with other minor alloying additions is underway. The aim is to develop alloys with improved mechanical properties, while minimizing the formation of embrittling second phases such as sigma or Laves. The stability of these alloys during thermal aging and the influence of the other alloying additions was studied in the current work for both solution-annealed and cold-worked conditions.Seven alloys based on Fe-12Cr-20Mn-0.25C were made with additions of W, Ti, V, P, and B, either singly or in combination. The alloys were hot-worked and subsequently cold-worked to sheet with intermediate anneals at 1150°C. Materials were aged at 600°C for 5000 h in both 20% cold-worked and annealed (1 h, 1050°C) conditions.
Quasicrystal structures in submicron spheres of pure nickel and nickel-chromium alloys
Authors: Lin Hong-Ming , Kelly Thomas F. 
Published: June 2020

The icosahedral quasicrystal with a fivefold rotation symmetry was first reported in Al-M (M = Cr, Mn, Fe) alloys. Later, quasicrystals with eightfold, tenfold, and twelvefold rotation symmetries were also reported. A twelvefold symmetry has been found in a Ni-70.6 at%Cr alloy and an eightfold symmetry has been found in a Cr-Ni-Si alloy. This indicates a potential for nickel-chromium alloys to form the quasicrystal phase.An intermediate state between crystalline and quasicrystalline states is also discussed by Li, Teng, et. al. in an Al-Cu-Mg alloy due to the coexistence of micro-quasicrystal and micro-crystal grains. When regions larger than 1 nm are measured, a coherent boundary is found between micro-quasicrystal and micro-crystal grains.A diffraction pattern with seemingly twelvefold symmetry is found in pure nickel and Ni-20at%Cr sphere of about 25 nm diameter as shown in Figure 1. The diffraction patterns do not have true twelvefold symmetry but the first diffraction ring is found to have twelve diffracted spots. Similar structures are found in Ni-10at%Cr and shown in Figure 2 with a series of diffraction patterns.
Peritectic solidification and precipitation of α-Re in β-NiAl Alloys containing Re additions
Authors: Webber J. G. , Van Aken D.C. 
Published: June 2020

Recently it has been shown that solidification of β-NiAl alloys which contain additions of Re will produce eutectic microstructures. The microstructure of the eutectic was determined to be composed of a matrix of β-NiAl with fibers of α-Re. It was thus concluded that a eutectic quasi-binary isopleth between β-NiAl and α-Re was present. Electron microprobe analysis of the eutectic areas showed a eutectic composition (in atomic percent) of 47.5 Ni, 51 Al and 1.5 Re.The fracture of these eutectic structures has been the primary interest in studying these materials. It appears that the α-Re may improve the fracture toughness of β-NiAl by a fiber pull-out mechanism, see Fig. 1. Careful examination of the α-Re fibers will reveal that each fiber exhibits plastic deformation. Indeed if the eutectic structure could be produced by directional solidification, the fracture toughness of this composite structure could be determined. The purpose of the present study is to further clarify the nature of this quasi-binary phase diagram.
The deformation and fracture of a dual-phase intermetallic alloy
Authors: Larsen Michael 
Published: June 2020

Ordered intermetallic alloys possess many attractive properties, yet their use as a structural material has been severely limited by a general lack of low temperature ductility. The beta/gamma-prime dual-phase Ni50Fe30A120 (atomic percent) intermetallic alloy has shown remarkable ductility, exhibiting fracture strains in excess of 20% in both tension and compression. This behavior is yet unexplained, thus an investigation was conducted to study the deformation and fracture behavior of this alloy.The material studied was a Ni50Fe30A120 (nominal composition) directionally solidified alloy. TEM specimens were made from the as cast material in an unstrained condition and with a 1% strain in compression. The foils were hand ground to a thickness of about 75 um and electrothinned in a Tenupol twin jet polisher with a methanol-based solution containing 2% perchloric acid and 35% butyl cellosolve at -20C. A JEOL 2000 FX AEM was used to examine the strained and unstrained foils. STEM microanalysis was performed on the unstrained foil with a Phillips CM-12 AEM to determine the composition of the two phases. Finally, the compression fracture surface was studied using a Hitachi S520 SEM.
Scanning tunneling microscopy of polymers: A status report
Authors: Russell P.E. , Musselman I.H. 
Published: June 2020

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.
Liquid crystalline polymer textures near the resolution limit of the light microscope
Authors: Viney C. 
Published: June 2020

The “texture” of a liquid crystal (LC) is the image obtained when thin specimens are viewed between crossed polars with a transmitted light microscope. Observation of textures, and of the way in which their appearance changes as the crossed polars are rotated, has long served as the basis for deducing the point-to-point variation of the average molecular orientation in low molecular weight LCs. Hence, the technique has been used as a means of identifying LC phases, and of elucidating their structure.Polymeric LCs show textures that are qualitatively similar to those formed by low molecular weight LCs, so it is tempting to interpret contrast in the same way in both cases . The textures of polymeric LCs are often quenchable: by means of rapid cooling, the molecular ordering characteristic of high temperatures can be preserved to room temperature. This is a consequence of the relatively slow kinetics of phase transformations in polymers, and is convenient because it allows the microscopist to work at magnifications and resolutions that are inaccessible while specimens are enclosed in a heating stage.
Characterization of machined polystyrene foam
Authors: Price C. W. , Lindsey E. F. , Franks R. M. , Lane M. A. 
Published: June 2020

Diamond-point turning is an efficient technique for machining low-density polystyrene foam, and the surface finish can be substantially improved by grinding. However, both diamond-point turning and grinding tend to tear and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Vibratoming is proving to be an excellent technique to form planar surfaces in polystyrene, and the machining characteristics of vibratoming and diamond-point turning are compared.Our work has demonstrated that proper evaluation of surface structures in low density polystyrene foam requires stereoscopic examinations; tilts of + and − 3 1/2 degrees were used for the stereo pairs. Coating does not seriously distort low-density polystyrene foam. Therefore, the specimens were gold-palladium coated and examined in a Hitachi S-800 FESEM at 5 kV.
Fine structure of inner shell electron energy loss edges of manganese oxides
Authors: Paterson James H. , Krivanek Ondrej L. , Poppa Helmut R. 
Published: June 2020

Rask et al. showed that electron energy loss spectroscopy (EELS) may be used to identify oxidation states of polyvalent cations. For the case of manganese, differences in oxidation state are reflected in the shape and position of the edges in the EELS spectrum due to inelastic scattering of incident electrons by the inner shells of manganese and oxygen. We have used a scanning transmission electron microscope (STEM) with a cold field emission gun (FEG) and a parallel-detection EELS system to re-investigate the variations in energy loss fine structure of EELS spectra of various manganese oxides with a significantly improved energy resolution.Spectra were recorded at 100 kV using a VG HB501 STEM with post-specimen lenses, and a Galan Model 666 parallel-detection electron energy loss spectrometer. The operation and performance of this system are discussed elsewhere in these proceedings. For the inner shell edges, the energy dispersion produced by the spectrometer was set to give 0.05 eV per channel. so that a complete spectrum of 1024 channels sampled a range of energy loss of 50 eV. The energy resolution, of the order of 0.4 eV, was therefore not limited by the spatial resolution of the photodiode array in the spectrometer. The oxygen K and manganese L2,3 edges were recorded separately.
Electron energy loss spectroscopy of nanometer-sized Cr crystallites in MgO single crystals
Authors: Tanaka N. , Mihama K. , Graham R. J. , Weiss J. K. , Cowley J. M. 
Published: June 2020

Conposite films including nanometer-sized metal crystallites and atomic clusters in ceramics or insulators are currently of great interest from the points of view of basic science and technology. We have developed new single crystalline composite films of magnesium oxide(MgO) and nanometer-sized metal crystallites. The crystalline structures were studied in detail by HREM and nanometer-area diffraction. In the present study, electron energy loss spectroscopy(EELS) of Chromium(Cr)-MgO composite films was performed to study the oxidation state of the Cr crystallites in the MgO matrix.Preparation methods of the composite films were described in detail in a previous paper. Cr and MgO were simultaneously deposited on a (001) cleaved surface of sodium chloride in UHV conditions of 10−6 Pa, the mean thickness of Cr and MgO being 3 nm and 30 nm, respectively. The composite films were separated from the substrate in water and mounted on a perforated carbon film. The EELS was carried out at 100 kV by using an electron microscope with a field emission gun (Philips FEG 400ST) equipped with a parallel detection spectrometer (Gatan 666).
Electron spectroscopic imaging and analysis of electron energy loss spectra with an energy filtering Electron Microscope
Authors: Godleski John J. , Stearns Rebecca C. , Millet Emil J. 
Published: June 2020

The Zeiss CEM902, energy filtering electron microscope, can be used to image the structure of unstained 30 nm sections of biologic materials, to image the distribution of selected elements in such sections, and to determine electron energy loss spectra (EELS) of elements in areas as small as 10 nm. Although the integrated computer in the latest version of the CEM902 can collect and display signals from the scintillation detector for recording EELS, our instrument did not have this capability. Therefore, we have added a Leading Edge Model D personal computer with a 20 Mbyte hard disk, Hercules compatible graphics display adapter, and a programmable gain analog to digital converter board (Metrabyte DAS16-G1) to collect and analyze voltage signals corresponding to changes in accelerating voltage and changes in the signal from the photomultiplier tube (PMT) of the scintillation detector. With this board, the gain on the PMT channel is dynamically adjusted for optimal resolution. Software is designed to monitor and display voltages, store data on the hard disk, display spectra with adjustable axes, as well as subtract spectra and determine areas beneath regions of interest.Canine alveolar macrophages with ingested cobalt oxide particles were fixed with 2.5% glutaraldehyde in 0.164M phosphate buffer, post-fixed in 1% OsO4 in 0.lM Na cacodylate buffer, dehydrated through alcohols, embedded in araldite, and sectioned at 30nm. Sections were assessed with our CEM902 as described above. The spectral range of 500 to 900 electron volts while focused on acobalt oxide particle at 20,000x is illustrated in Figure 1 .
Metastable ordered austenite in rapidly solidified Fe-Al-C alloys
Authors: Sarreal J. A. 
Published: June 2020

Conventionally cast Fe-Al-C alloys are extremely brittle containing combinations of ferrite, carbide and other phases. Rapid solidification has the potential of altering the microstructure to subsequently change the resulting mechanical properties. An apparent conflict exist concerning the effect of rapid solidification on the resulting microstructure of these alloys. Inoue and co-workers, using transmission electron microscopy (TEM) and electron diffraction analyses, reported the presence of several non-equilibrium phases including austenite (fcc - γ) and ordered austenite (Ll2-γ') structures on alloys containing 1.7 to 2.1 C and 6 to 12 Al in weight % (w/o) on melt spun ribbons 30 μm in thickness. Han and Choo, using x-ray diffraction analysis on 30-48 μm thick melt spun ribbons concluded that this ordered fee phase is rather an austenitic phase in which phase decomposition accompanied by sideband phenomenon had occured.Single roller melt spinning technique was used to make ribbons 35-70 μm thick and 0.5-5 mm wide. X-ray diffration analysis showed single phase austenite for samples 2-6 w/o AI and 2 w/o C. Samples with 8-10 w/o AI and 2 w/o C also showed several superlattice lines in addition to the fundamental fcc peaks.
Microstructural and fractographic characterization of B4C-Al cermets tested under dynamic and static loading
Authors: Kim Gyeung Ho , Sarikaya Mehmet , Milius D. L. , Aksay I. A. 
Published: June 2020

Cermets are designed to optimize the mechanical properties of ceramics (hard and strong component) and metals (ductile and tough component) into one system. However, the processing of such systems is a problem in obtaining fully dense composite without deleterious reaction products. In the lightweight (2.65 g/cc) B4C-Al cermet, many of the processing problems have been circumvented. It is now possible to process fully dense B4C-Al cermet with tailored microstructures and achieve unique combination of mechanical properties (fracture strength of over 600 MPa and fracture toughness of 12 MPa-m1/2). In this paper, microstructure and fractography of B4C-Al cermets, tested under dynamic and static loading conditions, are described.The cermet is prepared by infiltration of Al at 1150°C into partially sintered B4C compact under vacuum to full density. Fracture surface replicas were prepared by using cellulose acetate and thin-film carbon deposition. Samples were observed with a Philips 3000 at 100 kV.
Hydrogen embrittlement
Authors: Birnbaum H. K. , Robertson I. M. 
Published: June 2020

The effects of hydrogen on the fracture of metals will be reviewed using a selection of observations based on the use of in situ environmental cell experiments. These were developed to allow understanding of the mechanisms of the failure process. The in situ technique, combined with use of the environmental cell, is well suited to mechanistic studies of environmental fracture as it allows observation of crack tip processes at high resolution and in a relatively high fugacity aggressive environment. These methods have been applied to studies of the behavior of several systems. Selected examples will be discussed and a general pattern of behavior will be developed.A clear distinction will be made between the kinetics of hydrogen related fracture and the mechanisms by which fracture occurs. The rate at which hydrogen related fractures propagate depends on the factors which control the mobility and transfer of hydrogen across surfaces, on the fugacity of the hydrogen source, on the metallurgical properties of the alloys and on the stress intensities.
TEM study of ball-milled Ni-Ta alloy containing WC inclusions
Authors: Merk N. , Tanner L. E. 
Published: June 2020

High energy ball-milling of metallic powders is used extensively to achieve structural refinement. In recent years it has been found that cold-milling can induce transformations to highly metastable phases.In particular, the elemental mixing at the atomic-scale in certain systems may eventually lead to solid-state amorphization reactions (SSAR) after short periods of time. A problem that often arises in using this technique is contamination of the product from the grinding balls and container material.In this note we describe such a development in the microstructures that evolve during SSAR of a mixture of 75 atm% Ni and 25 atm% Ta high-purity powders processed for 17h in a planetary mill using WC + Co balls and container. The average composition of the ball-milled powders determined by EDS-analysis in a SEM was Ni75Ta25. X-ray diffraction confirmed the formation of an amorphous phase and also revealed the presence of sharp crystalline peaks identified as WC hexagonal phase (a=0.291 nm and c=0.283 nm); no detectable crystalline peaks from the initial Ni or Ta powders were observed. For TEM observations, small quantities of the ball-milled powders were embedded in epoxy and subsequently sectioned with a diamond knife using a Dupont-6000 ultramicrotome.
Stereoscopic analyses of surfaces on polystyrene foam
Authors: Lindsey E.F. , Price C. W. , Franks R. M. , Lane M. A. 
Published: June 2020

Analysis of surface finishes on machined polystyrene foam presents a unique challenge when the cell size of the foam is of the order of or larger than desired surface finishes. Ideally, the surface could be defined as the geometric surface formed by the locus of the severed edges of the cell walls. However, both machining and grinding tend to rip and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Machined geometric surfaces can be defined as the locus of the tips of the asperities, but the surface in between asperities can extend several cell layers below the asperities. The severe nature of this problem is emphasized by stereoscopic examinations of fractured, machined and ground, and cryo-vibratomed polystyrene surfaces in the SEM.Since coating does not seriously distort low-density polystyrene foam, the specimens were gold-palladium coated for examination in a Hitachi S-800 FESEM at 5 kV. Stereo pairs were obtained using tilts of + and − 3 1/2 degrees. The polystyrene foam had a cell size that varied between 2 to 11 μm.
Microtomy applications for materials science
Authors: Omlor R.E. , Lloyd P. F. 
Published: June 2020

Standard sample preparation techniques of various metals, composites, ceramics and polymer specimens can be very time consuming (such as dimpling and ion milling etc.), yet still introroduce artifacts during specimen preparation. With many of these materials numerous hours and sometimes even days can be spent preparing samples for TEM studies. In the past, ultramicrotomy has been used primarily for biological applications, but over the years has been tried on various polymers, metal and ceramic powders, oxide layers, etc. The main concern has been deformation introduced to the specimen while cutting. This study will demonstrate successful ultramicrotomy over a variety of non-biological specimens.Materials chosen for this experiment consist of Rapidly Solidified (RS) Al-V powders, P-120 Carbon fibers, Silicon Carbide (MMC) fibers, Kevlar and an IC semiconductor chip. Routine SEM micrographs were taken of all material as-received. All the specimens were embedded using a low viscoscity resin, L. R. White (hard grade). They were microtomed with a diamond knife at a 55-60° cutting angle using an AO/Reichert Ultracut Ultramicrotome with a slow cutting speed of 0.4 mm/sec which obtained the best results. All sections were picked up on Hex 700TB Ni grids.
A technique for preparing semiconductor cross sections for both TEM and SEM analysis
Authors: Klepeis Stanley J. , Benedict J.P. , Anderson R.M 
Published: June 2020

The ability to prepare a cross-section of a specific semiconductor structure for both SEM and TEM analysis is vital in characterizing the smaller, more complex devices that are now being designed and manufactured. In the past, a unique sample was prepared for either SEM or TEM analysis of a structure. In choosing to do SEM, valuable and unique information was lost to TEM analysis. An alternative, the SEM examination of thinned TEM samples, was frequently made difficult by topographical artifacts introduced by mechanical polishing and lengthy ion-milling. Thus, the need to produce a TEM sample from a unique,cross-sectioned SEM sample has produced this sample preparation technique.The technique is divided into an SEM and a TEM sample preparation phase. The first four steps in the SEM phase: bulk reduction, cleaning, gluing and trimming produces a reinforced sample with the area of interest in the center of the sample. This sample is then mounted on a special SEM stud. The stud is inserted into an L-shaped holder and this holder is attached to the Klepeis polisher (see figs. 1 and 2). An SEM cross-section of the sample is then prepared by mechanically polishing the sample to the area of interest using the Klepeis polisher. The polished cross-section is cleaned and the SEM stud with the attached sample, is removed from the L-shaped holder. The stud is then inserted into the ion-miller and the sample is briefly milled (less than 2 minutes) on the polished side. The sample on the stud may then be carbon coated and placed in the SEM for analysis.