Structural analysis of ion-implanted chemical-vapor-deposited diamond by transmission electron microscope

NASA Astrophysics Data System (ADS)

Jiang, N.; Deguchi, M.; Wang, C. L.; Won, J. H.; Jeon, H. M.; Mori, Y.; Hatta, A.; Kitabatake, M.; Ito, T.; Hirao, T.; Sasaki, T.; Hiraki, A.

1997-04-01

A transmission electron microscope (TEM) study of ion-implanted chemical-vapor-deposited (CVD) diamond is presented. CVD diamond used for transmission electron microscope observation was directly deposited onto Mo TEM grids. As-deposited specimens were irradiated by C (100 keV) ions at room temperature with a wide range of implantation doses (10 12-10 17/cm 2). Transmission electron diffraction (TED) patterns indicate that there exists a critical dose ( Dc) for the onset of amorphization of CVD diamond as a result of ion induced damage and the value of critical dose is confirmed to be about 3 × 10 15/cm 2. The ion-induced transformation process is clearly revealed by high resolution electron microscope (HREM) images. For a higher dose implantation (7 × 10 15/cm 2) a large amount of diamond phase is transformed into amorphous carbon and many tiny misoriented diamond blocks are found to be left in the amorphous solid. The average size of these misoriented diamond blocks is only about 1-2 nm. Further bombardment (10 17/cm 2) almost kills all of the diamond phase within the irradiated volume and moreover leads to local formation of micropolycrystalline graphite.

Differential phase acoustic microscope for micro-NDE

NASA Technical Reports Server (NTRS)

Waters, David D.; Pusateri, T. L.; Huang, S. R.

1992-01-01

A differential phase scanning acoustic microscope (DP-SAM) was developed, fabricated, and tested in this project. This includes the acoustic lens and transducers, driving and receiving electronics, scanning stage, scanning software, and display software. This DP-SAM can produce mechanically raster-scanned acoustic microscopic images of differential phase, differential amplitude, or amplitude of the time gated returned echoes of the samples. The differential phase and differential amplitude images provide better image contrast over the conventional amplitude images. A specially designed miniature dual beam lens was used to form two foci to obtain the differential phase and amplitude information of the echoes. High image resolution (1 micron) was achieved by applying high frequency (around 1 GHz) acoustic signals to the samples and placing two foci close to each other (1 micron). Tone burst was used in this system to obtain a good estimation of the phase differences between echoes from the two adjacent foci. The system can also be used to extract the V(z) acoustic signature. Since two acoustic beams and four receiving modes are available, there are 12 possible combinations to produce an image or a V(z) scan. This provides a unique feature of this system that none of the existing acoustic microscopic systems can provide for the micro-nondestructive evaluation applications. The entire system, including the lens, electronics, and scanning control software, has made a competitive industrial product for nondestructive material inspection and evaluation and has attracted interest from existing acoustic microscope manufacturers.

Crystal phase identification

DOEpatents

Michael, Joseph R.; Goehner, Raymond P.; Schlienger, Max E.

2001-01-01

A method and apparatus for determining the crystalline phase and crystalline characteristics of a sample. This invention provides a method and apparatus for unambiguously identifying and determining the crystalline phase and crystalline characteristics of a sample by using an electron beam generator, such as a scanning electron microscope, to obtain a backscattered electron Kikuchi pattern of a sample, and extracting crystallographic and composition data that is matched to database information to provide a quick and automatic method to identify crystalline phases.

Detecting Phase Boundaries in Hard-Sphere Suspensions

NASA Technical Reports Server (NTRS)

McDowell, Mark; Rogers, Richard B.; Gray, Elizabeth

2009-01-01

A special image-data-processing technique has been developed for use in experiments that involve observation, via optical microscopes equipped with electronic cameras, of moving boundaries between the colloidal-solid and colloidal-liquid phases of colloidal suspensions of monodisperse hard spheres. During an experiment, it is necessary to adjust the position of a microscope to keep the phase boundary within view. A boundary typically moves at a speed of the order of microns per hour. Because an experiment can last days or even weeks, it is impractical to require human intervention to keep the phase boundary in view. The present image-data-processing technique yields results within a computation time short enough to enable generation of automated-microscope-positioning commands to track the moving phase boundary

Atomic force microscopic imaging of Acanthamoeba castellanii and Balamuthia mandrillaris trophozoites and cysts.

PubMed

Aqeel, Yousuf; Siddiqui, Ruqaiyyah; Ateeq, Muhammad; Raza Shah, Muhammad; Kulsoom, Huma; Khan, Naveed Ahmed

2015-01-01

Light microscopy and electron microscopy have been successfully used in the study of microbes, as well as free-living protists. Unlike light microscopy, which enables us to observe living organisms or the electron microscope which provides a two-dimensional image, atomic force microscopy provides a three-dimensional surface profile. Here, we observed two free-living amoebae, Acanthamoeba castellanii and Balamuthia mandrillaris under the phase contrast inverted microscope, transmission electron microscope and atomic force microscope. Although light microscopy was of lower magnification, it revealed functional biology of live amoebae such as motility and osmoregulation using contractile vacuoles of the trophozoite stage, but it is of limited value in defining the cyst stage. In contrast, transmission electron microscopy showed significantly greater magnification and resolution to reveal the ultra-structural features of trophozoites and cysts including intracellular organelles and cyst wall characteristics but it only produced a snapshot in time of a dead amoeba cell. Atomic force microscopy produced three-dimensional images providing detailed topographic description of shape and surface, phase imaging measuring boundary stiffness, and amplitude measurements including width, height and length of A. castellanii and B. mandrillaris trophozoites and cysts. These results demonstrate the importance of the application of various microscopic methods in the biological and structural characterization of the whole cell, ultra-structural features, as well as surface components and cytoskeleton of protist pathogens. © 2014 The Author(s) Journal of Eukaryotic Microbiology © 2014 International Society of Protistologists.

Decomposition of L a2 -xS rxCu O4 into several L a2O3 phases at elevated temperatures in ultrahigh vacuum inside a transmission electron microscope

NASA Astrophysics Data System (ADS)

Jeong, Jong Seok; Wu, Wangzhou; Topsakal, Mehmet; Yu, Guichuan; Sasagawa, Takao; Greven, Martin; Mkhoyan, K. Andre

2018-05-01

We report the decomposition of L a2 -xS rxCu O4 into L a2O3 and Cu nanoparticles in ultrahigh vacuum, observed by in situ heating experiments in a transmission electron microscope. The analysis of electron diffraction data reveals that the phase decomposition process starts at about 150 °C and is considerably expedited in the temperature range of 350 °C-450 °C. Two major resultant solid phases are identified as metallic Cu and L a2O3 by electron diffraction, simulation, and electron energy-loss spectroscopy (EELS) analyses. With the aid of calculations, L a2O3 phases are further identified to be derivatives of a fluorite structure—fluorite, pyrochlore, and (distorted) bixbyite—characterized by different oxygen-vacancy order. Additionally, the bulk plasmon energy and the fine structures of the O K and La M4 ,5 EELS edges are reported for these structures, along with simulated O K x-ray absorption near-edge structure. The resultant Cu nanoparticles and L a2O3 phases remain unchanged after cooling to room temperature.

Carbon contamination in scanning transmission electron microscopy and its impact on phase-plate applications.

PubMed

Hettler, Simon; Dries, Manuel; Hermann, Peter; Obermair, Martin; Gerthsen, Dagmar; Malac, Marek

2017-05-01

We analyze electron-beam induced carbon contamination in a transmission electron microscope. The study is performed on thin films potentially suitable as phase plates for phase-contrast transmission electron microscopy. Electron energy-loss spectroscopy and phase-plate imaging is utilized to analyze the contamination. The deposited contamination layer is identified as a graphitic carbon layer which is not prone to electrostatic charging whereas a non-conductive underlying substrate charges. Several methods that inhibit contamination are evaluated and the impact of carbon contamination on phase-plate imaging is discussed. The findings are in general interesting for scanning transmission electron microscopy applications. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Phase-space foundations of electron holography

NASA Astrophysics Data System (ADS)

Lubk, A.; Röder, F.

2015-09-01

We present a unified formalism for describing various forms of electron holography in quantum mechanical phase space including their extensions to quantum-state reconstructions. The phase-space perspective allows for taking into account partial coherence as well as the quantum mechanical detection process typically hampering the unique reconstruction of a wave function. We elaborate on the limitations imposed by the electron optical elements of the transmission electron microscope as well as the scattering at the target. The results provide the basis for vastly extending the scope of electron holographic techniques towards analyzing partially coherent signals such as inelastically scattered electrons or electron pulses used in ultrafast transmission electron microscopy.

Theoretical study of ferroelectric nanoparticles using phase reconstructed electron microscopy

NASA Astrophysics Data System (ADS)

Phatak, C.; Petford-Long, A. K.; Beleggia, M.; De Graef, M.

2014-06-01

Ferroelectric nanostructures are important for a variety of applications in electronic and electro-optical devices, including nonvolatile memories and thin-film capacitors. These applications involve stability and switching of polarization using external stimuli, such as electric fields. We present a theoretical model describing how the shape of a nanoparticle affects its polarization in the absence of screening charges, and quantify the electron-optical phase shift for detecting ferroelectric signals with phase-sensitive techniques in a transmission electron microscope. We provide an example phase shift computation for a uniformly polarized prolate ellipsoid with varying aspect ratio in the absence of screening charges.

Quantum coherent optical phase modulation in an ultrafast transmission electron microscope.

PubMed

Feist, Armin; Echternkamp, Katharina E; Schauss, Jakob; Yalunin, Sergey V; Schäfer, Sascha; Ropers, Claus

2015-05-14

Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven 'quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

Quantum coherent optical phase modulation in an ultrafast transmission electron microscope

NASA Astrophysics Data System (ADS)

Feist, Armin; Echternkamp, Katharina E.; Schauss, Jakob; Yalunin, Sergey V.; Schäfer, Sascha; Ropers, Claus

2015-05-01

Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven `quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

Electron ptychographic phase imaging of light elements in crystalline materials using Wigner distribution deconvolution

DOE PAGES

Yang, Hao; MacLaren, Ian; Jones, Lewys; ...

2017-04-01

Recent development in fast pixelated detector technology has allowed a two dimensional diffraction pattern to be recorded at every probe position of a two dimensional raster scan in a scanning transmission electron microscope (STEM), forming an information-rich four dimensional (4D) dataset. Electron ptychography has been shown to enable efficient coherent phase imaging of weakly scattering objects from a 4D dataset recorded using a focused electron probe, which is optimised for simultaneous incoherent Z-contrast imaging and spectroscopy in STEM. Thus coherent phase contrast and incoherent Z-contrast imaging modes can be efficiently combined to provide a good sensitivity of both light andmore » heavy elements at atomic resolution. Here, we explore the application of electron ptychography for atomic resolution imaging of strongly scattering crystalline specimens, and present experiments on imaging crystalline specimens including samples containing defects, under dynamical channelling conditions using an aberration corrected microscope. A ptychographic reconstruction method called Wigner distribution deconvolution (WDD) was implemented. Our experimental results and simulation results suggest that ptychography provides a readily interpretable phase image and great sensitivity for imaging light elements at atomic resolution in relatively thin crystalline materials.« less

Decomposition of L a 2 – x S r x Cu O 4 into several L a 2 O 3 phases at elevated temperatures in ultrahigh vacuum inside a transmission electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, Jong Seok; Wu, Wangzhou; Topsakal, Mehmet

Here, we report the decomposition of La 2–xSr xCuO 4 into La 2O 3 and Cu nanoparticles in ultrahigh vacuum, observed by in situ heating experiments in a transmission electron microscope. The analysis of electron diffraction data reveals that the phase decomposition process starts at about 150°C and is considerably expedited in the temperature range of 350°C–450°C. Two major resultant solid phases are identified as metallic Cu and La 2O 3 by electron diffraction, simulation, and electron energy-loss spectroscopy (EELS) analyses. With the aid of calculations, La 2O 3 phases are further identified to be derivatives of a fluorite structure—fluorite,more » pyrochlore, and (distorted) bixbyite—characterized by different oxygen-vacancy order. Additionally, the bulk plasmon energy and the fine structures of the O K and LaM 4,5 EELS edges are reported for these structures, along with simulated O K x-ray absorption near-edge structure. The resultant Cu nanoparticles and La 2O 3 phases remain unchanged after cooling to room temperature.« less

Decomposition of L a 2 – x S r x Cu O 4 into several L a 2 O 3 phases at elevated temperatures in ultrahigh vacuum inside a transmission electron microscope

DOE PAGES

Jeong, Jong Seok; Wu, Wangzhou; Topsakal, Mehmet; ...

2018-05-15

Here, we report the decomposition of La 2–xSr xCuO 4 into La 2O 3 and Cu nanoparticles in ultrahigh vacuum, observed by in situ heating experiments in a transmission electron microscope. The analysis of electron diffraction data reveals that the phase decomposition process starts at about 150°C and is considerably expedited in the temperature range of 350°C–450°C. Two major resultant solid phases are identified as metallic Cu and La 2O 3 by electron diffraction, simulation, and electron energy-loss spectroscopy (EELS) analyses. With the aid of calculations, La 2O 3 phases are further identified to be derivatives of a fluorite structure—fluorite,more » pyrochlore, and (distorted) bixbyite—characterized by different oxygen-vacancy order. Additionally, the bulk plasmon energy and the fine structures of the O K and LaM 4,5 EELS edges are reported for these structures, along with simulated O K x-ray absorption near-edge structure. The resultant Cu nanoparticles and La 2O 3 phases remain unchanged after cooling to room temperature.« less

Analysis of phase transformations in Inconel 738C alloy after regenerative heat treatment

NASA Astrophysics Data System (ADS)

Kazantseva, N.; Davidov, D.; Vinogradova, N.; Ezhov, I.; Stepanova, N.

2018-03-01

Study is based on the characterization of the chemical composition the phase transformations in Inconel 738C gas turbine blade after standard regenerative heat treatment. The microstructure and chemical composition were examined by scanning electron microscope and transmission electron microscope equipped with an energy dispersive X-ray spectrometer. It was found the degradation of microstructure of the blade feather. Redistribution of the chemical elements decreasing the corrosion resistance was observed inside the blade feather. The carbide transformation and sigma phase were found in the structure of the blade feather. It is found that the standard regenerative heat treatment of the IN738 operative gas turbine blade does not effect on carbides transformation, TCP σ-phase dissolution, and thus do not guarantee the full recovery of the IN738 gas turbine blade.

Achieving atomic resolution magnetic dichroism by controlling the phase symmetry of an electron probe

DOE PAGES

Rusz, Jan; Idrobo, Juan -Carlos; Bhowmick, Somnath

2014-09-30

The calculations presented here reveal that an electron probe carrying orbital angular momentum is just a particular case of a wider class of electron beams that can be used to measure electron magnetic circular dichroism (EMCD) with atomic resolution. It is possible to obtain an EMCD signal with atomic resolution by simply breaking the symmetry of the electron probe phase front using the aberration-corrected optics of a scanning transmission electron microscope. The probe’s required phase distribution depends on the sample’s magnetic symmetry and crystal structure. The calculations indicate that EMCD signals that use the electron probe’s phase are as strongmore » as those obtained by nanodiffraction methods.« less

Comparative study viruses with computer-aided phase microscope AIRYSCAN

NASA Astrophysics Data System (ADS)

Tychinsky, Vladimir P.; Koufal, Georgy E.; Perevedentseva, Elena V.; Vyshenskaia, Tatiana V.

1996-12-01

Traditionally viruses are studied with scanning electron microscopy (SEM) after complicated procedure of sample preparation without the possibility to study it under natural conditions. We obtained images of viruses (Vaccinia virus, Rotavirus) and rickettsias (Rickettsia provazekii, Coxiella burnetti) in native state with computer-aided phase microscope airyscan -- the interference microscope of Linnik layout with phase modulation of the reference wave with dissector image tube as coordinate-sensitive photodetector and computer processing of phase image. A light source was the He-Ne laser. The main result is coincidence of dimensions and shape of phase images with available information concerning their morphology obtained with SEM and other methods. The fine structure of surface and nuclei is observed. This method may be applied for virus recognition and express identification, investigation of virus structure and the analysis of cell-virus interaction.

Analysis of Phase Separation in Czochralski Grown Single Crystal Ilmenite

NASA Technical Reports Server (NTRS)

Wilkins, R.; Powell, Kirk St. A.; Loregnard, Kieron R.; Lin, Sy-Chyi; Muthusami, Jayakumar; Zhou, Feng; Pandey, R. K.; Brown, Geoff; Hawley, M. E.

1998-01-01

Ilmenite (FeTiOs) is a wide bandgap semiconductor with an energy gap of 2.58 eV. Ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Single crystal ilmenite has been grown from the melt using the Czochralski method. Growth conditions have a profound effect on the microstructure of the samples. Here we present data from a variety of analytical techniques which indicate that some grown crystals exhibit distinct phase separation during growth. This phase separation is apparent for both post-growth annealed and unannealed samples. Under optical microscopy, there appear two distinct areas forming a matrix with an array of dots on order of 5 pm diameter. While appearing bright in the optical micrograph, atomic force microscope (AFM) shows the dots to be shallow pits on the surface. Magnetic force microscope (MFM) shows the dots to be magnetic. Phase identification via electron microprobe analysis (EMPA) indicates two major phases in the unannealed samples and four in the annealed samples, where the dots appear to be almost pure iron. This is consistent with micrographs taken with a scanning probe microscope used in the magnetic force mode. Samples that do not exhibit the phase separation have little or no discernible magnetic structure detectable by the MFM.

Path-separated electron interferometry in a scanning transmission electron microscope

NASA Astrophysics Data System (ADS)

Yasin, Fehmi S.; Harvey, Tyler R.; Chess, Jordan J.; Pierce, Jordan S.; McMorran, Benjamin J.

2018-05-01

We report a path-separated electron interferometer within a scanning transmission electron microscope. In this setup, we use a nanofabricated grating as an amplitude-division beamsplitter to prepare multiple spatially separated, coherent electron probe beams. We achieve path separations of 30 nm. We pass the  +1 diffraction order probe through amorphous carbon while passing the 0th and  ‑1 orders through vacuum. The probes are then made to interfere via imaging optics, and we observe an interference pattern at the CCD detector with up to 39.7% fringe visibility. We show preliminary experimental results in which the interference pattern was recorded during a 1D scan of the diffracted probes across a test phase object. These results qualitatively agree with a modeled interference predicted by an independent measurement of the specimen thickness. This experimental design can potentially be applied to phase contrast imaging and fundamental physics experiments, such as an exploration of electron wave packet coherence length.

Dynamic imaging with electron microscopy

ScienceCinema

Campbell, Geoffrey; McKeown, Joe; Santala, Melissa

2018-02-13

Livermore researchers have perfected an electron microscope to study fast-evolving material processes and chemical reactions. By applying engineering, microscopy, and laser expertise to the decades-old technology of electron microscopy, the dynamic transmission electron microscope (DTEM) team has developed a technique that can capture images of phenomena that are both very small and very fast. DTEM uses a precisely timed laser pulse to achieve a short but intense electron beam for imaging. When synchronized with a dynamic event in the microscope's field of view, DTEM allows scientists to record and measure material changes in action. A new movie-mode capability, which earned a 2013 R&D 100 Award from R&D Magazine, uses up to nine laser pulses to sequentially capture fast, irreversible, even one-of-a-kind material changes at the nanometer scale. DTEM projects are advancing basic and applied materials research, including such areas as nanostructure growth, phase transformations, and chemical reactions.

Technique to quantitatively measure magnetic properties of thin structures at <10 NM spatial resolution

DOEpatents

Bajt, Sasa

2003-07-08

A highly sensitive and high resolution magnetic microscope images magnetic properties quantitatively. Imaging is done with a modified transmission electron microscope that allows imaging of the sample in a zero magnetic field. Two images from closely spaced planes, one in focus and one slightly out of focus, are sufficient to calculate the absolute values of the phase change imparted to the electrons, and hence obtain the magnetization vector field distribution.

Applications of the Analytical Electron Microscope to Materials Science

NASA Technical Reports Server (NTRS)

Goldstein, J. I.

1992-01-01

In the last 20 years, the analytical electron microscope (AEM) as allowed investigators to obtain chemical and structural information from less than 50 nanometer diameter regions in thin samples of materials and to explore problems where reactions occur at boundaries and interfaces or within small particles or phases in bulk samples. Examples of the application of the AEM to materials science problems are presented in this paper and demonstrate the usefulness and the future potential of this instrument.

Microscopic Mechanism of Doping-Induced Kinetically Constrained Crystallization in Phase-Change Materials.

PubMed

Lee, Tae Hoon; Loke, Desmond; Elliott, Stephen R

2015-10-07

A comprehensive microscopic mechanism of doping-induced kinetically constrained crystallization in phase-change materials is provided by investigating structural and dynamical dopant characteristics via ab initio molecular dynamics simulations. The information gained from this study may provide a basis for a fast screening of dopant species for electronic memory devices, or for understanding the general physics involved in the crystallization of doped glasses. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Methods and devices for measuring orbital angular momentum states of electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMorran, Benjamin J.; Harvey, Tyler R.

A device for measuring electron orbital angular momentum states in an electron microscope includes the following components aligned sequentially in the following order along an electron beam axis: a phase unwrapper (U) that is a first electrostatic refractive optical element comprising an electrode and a conductive plate, where the electrode is aligned perpendicular to the conductive plate; a first electron lens system (L1); a phase corrector (C) that is a second electrostatic refractive optical element comprising an array of electrodes with alternating electrostatic bias; and a second electron lens system (L2). The phase unwrapper may be a needle electrode ormore » knife edge electrode.« less

Electron-beam-induced structure transformation of the quasicrystalline phases of the Al 62Cu 20Co 15Si 3 alloy

NASA Astrophysics Data System (ADS)

Reyes-Gasga, J.; R. Garcia, G.; Jose-Yacaman, M.

1995-02-01

Some details on the phase transformation experienced by the quasicrystalline phases of the Al 62Cu 20Co 15Si 3 alloy under a 400 kV electron beam are given. The transition is observed in situ with a high resolution electron microscope and recorded on video tape. The results show that the electron beam radiation produces a sequence of changes similar to the ones observed in an ion-beam-induced amorphization process. Considering electron radiation damage analysis, the results agree well with the "flip-flop" model [Coddens, Bellisent, Calvayrac and Ambroise (1991) Europhys. Lett.16, 271] where the transition from a quasicrystalline phase to a crystalline phase is produced by atomic displacements but not in a cascade way.

Microstructural studies of 35 degrees C copper Ni-Ti orthodontic wire and TEM confirmation of low-temperature martensite transformation.

PubMed

Brantley, William A; Guo, Wenhua; Clark, William A T; Iijima, Masahiro

2008-02-01

Previous temperature-modulated differential scanning calorimetry (TMDSC) study of nickel-titanium orthodontic wires revealed a large exothermic low-temperature peak that was attributed to transformation within martensitic NiTi. The purpose of this study was to use transmission electron microscopy (TEM) to verify this phase transformation in a clinically popular nickel-titanium wire, identify its mechanism and confirm other phase transformations found by TMDSC, and to provide detailed information about the microstructure of this wire. The 35 degrees C Copper nickel-titanium wire (Ormco) with cross-section dimensions of 0.016 in. x 0.022 in. used in the earlier TMDSC investigation was selected. Foils were prepared for TEM analyses by mechanical grinding, polishing, dimpling, ion milling and plasma cleaning. Standard bright-field and dark-field TEM images were obtained, along with convergent-beam electron diffraction patterns. A cryo-stage with the electron microscope (Phillips CM 200) permitted the specimen to be observed at -187, -45, and 50 degrees C, as well as at room temperature. Microstructures were also observed with an optical microscope and a scanning electron microscope. Room temperature microstructures had randomly oriented, elongated grains that were twinned. Electron diffraction patterns confirmed that phase transformations took place over temperature ranges previously found by TMDSC. TEM observations revealed a high dislocation density and fine-scale oxide particles, and that twinning is the mechanism for the low-temperature transformation in martensitic NiTi. TEM confirmed the low-temperature peak and other phase transformations observed by TMDSC, and revealed that twinning in martensite is the mechanism for the low-temperature peak. The high dislocation density and fine-scale oxide particles in the microstructure are the result of the wire manufacturing process.

Chemical characterization of surface precipitates in La0.7Sr0.3Co0.2Fe0.8O3-δ as cathode material for solid oxide fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Yang; Nikiforov, Alexey Y.; Kaspar, Tiffany C.

2016-11-01

In this study, a strontium doped lanthanum cobalt ferrite thin film with 30% Sr on A-site, denoted as La0.7Sr0.3Co0.2Fe0.8O3-δ or LSCF-7328, was investigated before and after annealing at 800 °C under CO2 containing atmosphere for 9 hours. The formation of secondary phases on surface of post-annealed LSCF-7328 has been observed using atomic force microscope (AFM) and scanning electron microscope (SEM). The extent of Sr segregation at the film surface was observed using the synchrotron-based total reflection X-ray fluorescence (TXRF) technique. The bonding environment of the secondary phases formed on the surface was investigated by synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES).more » Transmission electron microscope (TEM) and related spectroscopy techniques were used for microstructural and quantitative elemental analyses of the secondary phases on surface. These studies revealed that the secondary phases on surface consisted of SrO covered with a capping layer of SrCO3. The formation of Co-rich phases has also been observed on the surface of post-annealed LSCF-7328.« less

A new route for the synthesis of submicron-sized LaB{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lihong, Bao; Wurentuya,; Wei, Wei

Submicron crystalline LaB{sub 6} has been successfully synthesized by a solid-state reaction of La{sub 2}O{sub 3} with NaBH{sub 4} at 1200 °C. The effects of reaction temperature on the crystal structure, grain size and morphology were investigated by X-ray diffraction, scanning electron microscope and transmission electron microscope. It is found that when the reaction temperature is in the range of 1000–1100 °C, there are ultrafine nanoparticles and nanocrystals that coexist. When the reaction temperature elevated to 1200 °C, the grain morphology transformed from ultrafine nanoparticle to submicron crystals completely. High resolution transmission electron microscope images fully confirm the formation ofmore » LaB{sub 6} cubic structure. - Highlights: • Single-phased LaB{sub 6} have been synthesized by a solid-state reaction in a continuous evacuating process. • The reaction temperature has a important effect on the phase composition. • The grain size increase from nano-size to submicron with increasing reaction temperature.« less

Three-dimensional characterization of extreme ultraviolet mask blank defects by interference contrast photoemission electron microscopy.

PubMed

Lin, Jingquan; Weber, Nils; Escher, Matthias; Maul, Jochen; Han, Hak-Seung; Merkel, Michael; Wurm, Stefan; Schönhense, Gerd; Kleineberg, Ulf

2008-09-29

A photoemission electron microscope based on a new contrast mechanism "interference contrast" is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast photoemission electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.

The relationship between morphological changes of lens epithelial cells and intraocular lens optic material.

PubMed

Majima, K

1998-01-01

To examine the morphological changes of lens epithelial cells (LECs) occurring directly beneath and at regions contacting various intraocular lens (IOL) optic materials, human LECs were cultured on human anterior lens capsules and were further incubated upon placing above the cells lens optics made of polymethylmethacrylate, silicone, and soft acrylic material. Observations as to the morphological changes of LECs under phase-contrast microscope and scanning electron microscope were performed on the 14th day of incubation. Gatherings of LECs were observed at regions contacting the soft acrylic material under phase-contrast microscope, and gatherings of LECs were observed accurately at the same regions mentioned above under scanning electron microscope. On the other hand, LECs in contact with two other optic materials did not show morphological changes. The results suggest that LECs attached to and proliferated on not only the anterior lens capsules but also the soft acrylic IOL optics. The model used in this study may be useful in studying the relationship between cellular movement of LECs and IOL optic material.

In Situ Microstructural Control and Mechanical Testing Inside the Transmission Electron Microscope at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Wang, Baoming; Haque, M. A.

2015-08-01

With atomic-scale imaging and analytical capabilities such as electron diffraction and energy-loss spectroscopy, the transmission electron microscope has allowed access to the internal microstructure of materials like no other microscopy. It has been mostly a passive or post-mortem analysis tool, but that trend is changing with in situ straining, heating and electrical biasing. In this study, we design and demonstrate a multi-functional microchip that integrates actuators, sensors, heaters and electrodes with freestanding electron transparent specimens. In addition to mechanical testing at elevated temperatures, the chip can actively control microstructures (grain growth and phase change) of the specimen material. Using nano-crystalline aluminum, nickel and zirconium as specimen materials, we demonstrate these novel capabilities inside the microscope. Our approach of active microstructural control and quantitative testing with real-time visualization can influence mechanistic modeling by providing direct and accurate evidence of the fundamental mechanisms behind materials behavior.

Effect of high-energy electron irradiation in an electron microscope column on fluorides of alkaline earth elements (CaF2, SrF2, and BaF2)

NASA Astrophysics Data System (ADS)

Nikolaichik, V. I.; Sobolev, B. P.; Zaporozhets, M. A.; Avilov, A. S.

2012-03-01

The effect of high-energy (150 eV) electron irradiation in an electron microscope column on crystals of fluorides of alkaline earth elements CaF2, SrF2, and BaF2 is studied. During structural investigations by electron diffraction and electron microscopy, the electron irradiation causes chemical changes in MF2 crystals such as the desorption of fluorine and the accumulation of oxygen in the irradiated area with the formation of oxide MO. The fluorine desorption rate increases significantly when the electron-beam density exceeds the threshold value of ˜2 × 103 pA/cm2). In BaF2 samples, the transformation of BaO into Ba(OH)2 was observed when irradiation stopped. The renewal of irradiation is accompanied by the inverse transformation of Ba(OH)2 into BaO. In the initial stage of irradiation of all MF2 compounds, the oxide phase is in the single-crystal state with a lattice highly matched with the MF2 matrix. When the irradiation dose is increased, the oxide phase passes to the polycrystalline phase. Gaseous products of MF2 destruction (in the form of bubbles several nanometers in diameter) form a rectangular array with a period of ˜20 nm in the sample.

Microanalytical Efforts in Support of NASA's Materials Science Programs

NASA Technical Reports Server (NTRS)

Gillies, Donald C.

2004-01-01

Following a brief overview of NASA s Microgravity Materials Science programs, specific examples will be given showing electron beam and optical microscopic applications to two-phase glass structures, dendrite tip radii, solid solution semiconductors, undercooled two-phase stainless steels and meteorites.

In situ electron microscope study of the phase transformation, structure and growth of thin Te1-xSex films

NASA Astrophysics Data System (ADS)

Vermaak, J. S.; Raubenheimer, D.

1988-01-01

An in-situ electron microscope technique was utilized to observe directly the amorphous-to-crystalline phase transformation, the isothermal growth rates, as well as the orientation and structure of the recrystallized films for the Te1-xSex alloy system for x=0.2, 0.3 and 0.4. Activation energies of E=0.91, 0.93 and 0.96 eV and crystallization temperatures of Tc=-14, 81.5 and 85°C for the three alloys, respectively, were found. In all three cases the crystallization process originated from single crystalline nuclei with a hexagonal structure and with the c-axis in general parallel to the substrate surface.

Atomic resolved phase map of monolayer MoS2 retrieved by spherical aberration-corrected transport of intensity equation.

PubMed

Zhang, Xiaobin; Oshima, Yoshifumi

2016-10-01

An atomic resolution phase map, which enables us to observe charge distribution or magnetic properties at an atomic scale, has been pointed out to be retrieved by transport of intensity equation (TIE) when taking two atomic-resolved transmission electron microscope (TEM) images of small defocus difference. In this work, we firstly obtained the atomic-resolved phase maps of an exfoliated molybdenum disulfide sheet using spherical aberration-corrected transmission electron microscope. We successfully observed 60° grain boundary of mechanically exfoliated monolayer molybdenum disulfide sheet. The relative phase shift of a single molybdenum atomic column to the column consisting of two sulfur atoms was obtained to be about 0.01 rad on average, which was about half lower than the simulated TIE phase map, indicating that the individual atomic sites can be distinguished qualitatively. The appropriate condition for retrieving atomic-resolved TIE phase maps was briefly discussed. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Phase-Contrast versus Off-Axis Illumination: Is a More Complex Microscope Always More Powerful?

ERIC Educational Resources Information Center

Hostounsky, Zdenek; Pelc, Radek

2007-01-01

In this article, a practical demonstration suitable for any biology college classroom is presented. With the examples of a complex biological specimen (slug's radula) and a simple reference specimen (electron microscopical grid imprint in gelatin), both of which can be easily prepared, the capabilities of two imaging modes commonly used in optical…

Source brightness and useful beam current of carbon nanotubes and other very small emitters

NASA Astrophysics Data System (ADS)

Kruit, P.; Bezuijen, M.; Barth, J. E.

2006-01-01

The potential application of carbon nanotubes as electron sources in electron microscopes is analyzed. The resolution and probe current that can be obtained from a carbon nanotube emitter in a low-voltage scanning electron microscope are calculated and compared to the state of the art using Schottky electron sources. Many analytical equations for probe-size versus probe-current relations in different parameter regimes are obtained. It is shown that for most carbon nanotube emitters, the gun lens aberrations are larger than the emitters' virtual source size and thus restrict the microscope's performance. The result is that the advantages of the higher brightness of nanotube emitters are limited unless the angular emission current is increased over present day values or the gun lens aberrations are decreased. For some nanotubes with a closed cap, it is known that the emitted electron beam is coherent over the full emission cone. We argue that for such emitters the parameter ``brightness'' becomes meaningless. The influence of phase variations in the electron wave front emitted from such a nanotube emitter on the focusing of the electron beam is analyzed.

Light, electron microscopic and immunohistochemical study of the effect of low-dose aspirin during the proestrus phase on rat endometrium in the preimplantation period.

PubMed

Ateş, Utku; Baka, Meral; Turgut, Mehmet; Uyanikgil, Yiğit; Ulker, Sibel; Yilmaz, Ozlem; Tavmergen, Erol; Yurtseven, Mine

2007-04-01

To evaluate structural alterations in rat endometrium at preimplantation following treatment with aspirin beginning from proestrus by light microscopy, electron microscopy and immunohistochemical techniques. Twenty rats were divided into control (n = 10) and experimental (n = 10) groups. Experimental rats were treated with low-dose aspirin daily (2 mg/kg/day) during estrus, beginning from the proestrus phase, mated at end of cycle and treated with aspirin. Untreated pregnant rats were the control group. Rats in both groups were sacrificed at the 84th pregnancy hour; the uterus was rapidly removed and dissected free of surrounding adipose tissue. Uteri specimens from nonpregnant rats were transferred into fixative solution and processed for light, electron microscopic and immunohistochemical study. Light and electron microscopy of endometrium from control rats conformed to mid-diestrus phase; endometrial histology of the aspirin-treated group conformed to late diestrus phase. The endometrial layer was significantly thicker in the aspirin-treated group compared to the untreated control group (p <0.001). No significant difference was found in vessel number between groups. Staining with alphaV integrin was more dense in the aspirin-treated group. Based on histologic findings, we suggest low-dose aspirin has positive effects on preparing endometrium before implantation.

WC/Co composite surface structure and nano graphite precipitate induced by high current pulsed electron beam irradiation

NASA Astrophysics Data System (ADS)

Hao, S. Z.; Zhang, Y.; Xu, Y.; Gey, N.; Grosdidier, T.; Dong, C.

2013-11-01

High current pulsed electron beam (HCPEB) irradiation was conducted on a WC-6% Co hard alloy with accelerating voltage of 27 kV and pulse duration of 2.5 μs. The surface phase structure was examined by using glancing-angle X-ray diffraction (GAXRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) methods. The surface tribological properties were measured. It was found that after 20 pulses of HCPEB irradiation, the surface structure of WC/Co hard alloy was modified dramatically and composed of a mixture of nano-grained WC1-x, Co3W9C4, Co3W3C phases and graphite precipitate domains ˜50 nm. The friction coefficient of modified surface decreased to ˜0.38 from 0.6 of the initial state, and the wear rate reduced from 8.4 × 10-5 mm3/min to 6.3 × 10-6 mm3/min, showing a significant self-lubricating effect.

Phase study of titanium dioxide nanoparticle prepared via sol-gel process

NASA Astrophysics Data System (ADS)

Oladeji Araoyinbo, Alaba; Bakri Abdullah, Mohd Mustafa Al; Salleh, Mohd Arif Anuar Mohd; Aziz, Nurul Nadia Abdul; Iskandar Azmi, Azwan

2018-03-01

In this study, titanium dioxide nanoparticles have been prepared via sol-gel process using titanium tetraisopropoxide as a precursor with hydrochloric acid as a catalyst, and ethanol with deionized water as solvents. The value of pH used is set to 3, 7 and 8. The sols obtained were dried at 100 °C for 1 hr and calcined at 350, 550, and 750 °C for 3 hrs to observe the phase transformation of titanium dioxide nanoparticle. The samples were characterized by x-ray diffraction and field emission scanning electron microscope. The morphology analysis is obtained from field emission scanning electron microscope. The phase transformation was investigated by x-ray diffraction. It was found that the pH of the solution affect the agglomeration of titanium dioxide particle. The x-ray diffraction pattern of titanium dioxide shows the anatase phase most abundant at temperature of 350 °C. At temperature of 550 °C the anatase and rutile phase were present. At temperature of 750 °C the rutile phase was the most abundant for pH 3, 7 and 8. It was confirmed that at higher temperature the rutile phase which is the stable phase are mostly present.

Effect of phase transformation on optical and dielectric properties of zirconium oxide nanoparticles

NASA Astrophysics Data System (ADS)

Chintaparty, Rajababu; Palagiri, Bhavani; Reddy Nagireddy, Ramamanohar; subbha Reddy Imma Reddy, Venkata

2015-09-01

Zirconium oxide nanoparticle (ZrO2) is synthesized by the hydrothermal method at different calcination temperatures. The structural analysis is carried out by X-ray diffraction and Raman spectra. The sample prepared at 400 °C and 1100 °C showed the cubic and monoclinic phase, respectively, and the sample calcined at 600 °C and 800 °C showed the mixed phase with co-existence of cubic and monoclinic phases. Furthermore, the morphology and particle size of these samples were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis. The band gap estimated from UV-Vis spectra of ZrO2 (zirconia) nanocrystalline materials calcined at different temperatures from 400 °C to 1100 °C was in the range of 2.6-4.2 eV. The frequency dependence of dielectric constant and dielectric loss was investigated at room temperature. The low frequency region of dielectric constant is attributed to space charge effects.

Microstructure and Texture Evolutions of Biomedical Ti-13Nb-13Zr Alloy Processed by Hydrostatic Extrusion

NASA Astrophysics Data System (ADS)

Ozaltin, K.; Panigrahi, A.; Chrominski, W.; Bulutsuz, A. G.; Kulczyk, M.; Zehetbauer, M. J.; Lewandowska, M.

2017-11-01

A biomedical β-type Ti-13Nb-13Zr (TNZ) (wt pct) ternary alloy was subjected to severe plastic deformation by means of hydrostatic extrusion (HE) at room temperature without intermediate annealing. Its effect on microstructure, mechanical properties, phase transformations, and texture was investigated by light and electron microscopy, mechanical tests (Vickers microhardness and tensile tests), and XRD analysis. Microstructural investigations by light microscope and transmission electron microscope showed that, after HE, significant grain refinement took place, also reaching high dislocation densities. Increases in strength up to 50 pct occurred, although the elongation to fracture left after HE was almost 9 pct. Furthermore, Young's modulus of HE-processed samples showed slightly lower values than the initial state due to texture. Such mechanical properties combined with lower Young's modulus are favorable for medical applications. Phase transformation analyses demonstrated that both initial and extruded samples consist of α' and β phases but that the phase fraction of α' was slightly higher after two stages of HE.

Structural transformation study of TiO2 nanoparticles annealing at different temperatures and the photodegradation process of eosin-Y

NASA Astrophysics Data System (ADS)

Pandi, P.; Gopinathan, C.

2018-04-01

Hydrothermal method was used to prepare TiO2 nanoparticles with annealing temperature at 500 °C-700 °C. The mixture of anatase-rutile phase was investigated by powerful tool of X-ray diffraction (XRD). The structural parameters of anatase and rutile mixture phaseTiO2 nanoparticles were calculated from the Rietveld refinement. The transformation rate of rutile was increased linearly with an annealing temperature of 500 °C-700 °C. The spherical morphology of the anatase and rutile mixed phase were obtained by scanning electron microscope and transmission electron microscope. The spherical particle of the anatase and rutile TiO2 shows with great aggregation with different size and within the range of few tens nm. The EDAX study revealed the presence of titanium and oxygen. The best photocatalytic activity was identified as the 87.04% of anatase and 12.96% of rutile mixer phase of TiO2. Various factors could be involved for a better photocatalytic activity.

Nonequilibrium segregation and phase instability in alloy films during elevated-temperature irradiation in a high-voltage electron microscope

NASA Astrophysics Data System (ADS)

Lam, N. Q.; Okamoto, P. R.

1984-05-01

The effects of defect-production rate gradients, caused by the radial nonuniformity in the electron flux distribution, on solute segregation and phase stability in alloy films undergoing high-voltage electron-microscope (HVEM) irradiation at high temperatures are assessed. Two-dimensional (axially symmetric) compositional redistributions were calculated, taking into account both axial and transverse radial defect fluxes. It was found that when highly focused beams were employed radiation-induced segregation consisted of two stages: dominant axial segregation at the film surfaces at short irradiation times and competitive radial segregation at longer times. The average alloy composition within the irradiated region could differ greatly from that irradiated with a uniform beam, because of the additional atom transport from or to the region surrounding the irradiated zone under the influence of radial fluxes. Damage-rate gradient effects must be taken into account when interpreting in-situ HVEM observations of segregation-induced phase instabilities. The theoretical predictions are compared with experimental observations of the temporal and spatial dependence of segregation-induced precipitation in thin films of Ni-Al, Ni-Ge and Ni-Si solid solutions.

Effect of Silicon in U-10Mo Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kautz, Elizabeth J.; Devaraj, Arun; Kovarik, Libor

2017-08-31

This document details a method for evaluating the effect of silicon impurity content on U-10Mo alloys. Silicon concentration in U-10Mo alloys has been shown to impact the following: volume fraction of precipitate phases, effective density of the final alloy, and 235-U enrichment in the gamma-UMo matrix. This report presents a model for calculating these quantities as a function of Silicon concentration, which along with fuel foil characterization data, will serve as a reference for quality control of the U-10Mo final alloy Si content. Additionally, detailed characterization using scanning electron microscope imaging, transmission electron microscope diffraction, and atom probe tomography showedmore » that Silicon impurities present in U-10Mo alloys form a Si-rich precipitate phase.« less

Electron beam analysis of particulate cometary material

NASA Technical Reports Server (NTRS)

Bradley, John

1989-01-01

Electron microscopy will be useful for characterization of inorganic dust grains in returned comet nucleus samples. The choice of instrument(s) will depend primarily on the nature of the samples, but ultimately a variety of electron-beam methods could be employed. Scanning and analytical (transmission) electron microscopy are the logical choise for morphological, mineralogical, and bulk chemical analyses of dust grains removed from ices. It may also be possible to examine unmelted ice/dust mixtures using an environmental scanning electron microscope equipped with a cryo-transfer unit and a cold stage. Electron microscopic observations of comet nuclei might include: (1) porosities of dust grains; (2) morphologies and microstructures of individual mineral grains; (3) relative abundances of olivine, pyroxene, and glass; and (4) the presence of phases that might have resulted from aqueous alteration (layer silicates, carbonates, sulfates).

Electron microscopy study of the iron meteorite Santa Catharina

NASA Technical Reports Server (NTRS)

Zhang, J.; Williams, D. B.; Goldstein, J. I.; Clarke, R. S., Jr.

1990-01-01

A characterization of the microstructural features of Santa Catharina (SC) from the millimeter to submicron scale is presented. The same specimen was examined using an optical microscope, a scanning electron microscope, an electron probe microanalyzer, and an analytical electron microscope. Findings include the fact that SC metal nodules may have different bulk Ni values, leading to different microstructures upon cooling; that SC USNM 6293 is the less corroded sample, as tetrataenite exists as less than 10 nm ordered domains throughout the entire fcc matrix (it is noted that this structure is the same as that of the Twin City meteorite and identical to clear taenite II in the retained taenite regions of the octahedrites); that SC USNM 3043 has a more complicated microstructure due to corrosion; and that the low Ni phase of the cloudy zone was selectively corroded in some areas and formed the dark regions, indicating that the SC meteorite corrosion process was electrochemical in nature and may involve Cl-containing akaganeite.

Acquisition of a High Resolution Field Emission Scanning Electron Microscope for the Analysis of Returned Samples

NASA Technical Reports Server (NTRS)

Nittler, Larry R.

2003-01-01

This grant furnished funds to purchase a state-of-the-art scanning electron microscope (SEM) to support our analytical facilities for extraterrestrial samples. After evaluating several instruments, we purchased a JEOL 6500F thermal field emission SEM with the following analytical accessories: EDAX energy-dispersive x-ray analysis system with fully automated control of instrument and sample stage; EDAX LEXS wavelength-dispersive x-ray spectrometer for high sensitivity light-element analysis; EDAX/TSL electron backscatter diffraction (EBSD) system with software for phase identification and crystal orientation mapping; Robinson backscatter electron detector; and an in situ micro-manipulator (Kleindiek). The total price was $550,000 (with $150,000 of the purchase supported by Carnegie institution matching funds). The microscope was delivered in October 2002, and most of the analytical accessories were installed by January 2003. With the exception of the wavelength spectrometer (which has been undergoing design changes) everything is working well and the SEM is in routine use in our laboratory.

Phase separation of electrons strongly coupled with phonons in cuprates and manganites

NASA Astrophysics Data System (ADS)

Alexandrov, Sasha

2009-03-01

Recent advanced Monte Carlo simulations have not found superconductivity and phase separation in the Hubbard model with on-site repulsive electron-electron correlations. I argue that microscopic phase separations in cuprate superconductors and colossal magnetoresistance (CMR) manganites originate from a strong electron-phonon interaction (EPI) combined with unavoidable disorder. Attractive electron correlations, caused by an almost unretarded EPI, are sufficient to overcome the direct inter-site Coulomb repulsion in these charge-transfer Mott-Hubbard insulators, so that low energy physics is that of small polarons and small bipolarons. They form clusters localized by disorder below the mobility edge, but propagate as the Bloch states above the mobility edge. I identify the Froehlich EPI as the most essential for pairing and phase separation in superconducting layered cuprates. The pairing of oxygen holes into heavy bipolarons in the paramagnetic phase (current-carrier density collapse (CCDC)) explains also CMR and high and low-resistance phase coexistence near the ferromagnetic transition of doped manganites.

Description of the last instar larva and new contributions to the knowledge of the pupa of Dasyhelea mediomunda Minaya (Diptera, Culicomorpha, Ceratopogonidae).

PubMed

Díaz, Florentina; Anjos-Santos, Danielle; Funes, Amparo; Ronderos, María M

2016-01-01

The fourth instar larva of Dasyhelea mediomunda Minaya is described for the first time and a complete description of the pupa is provided, through use of phase-contrast microscope and scanning electron microscope. Studied specimens were collected in a pond connected to a small wetland "mallin" on the Patagonian steppe, Chubut province, Argentina.

Joint Services Electronics Program Annual Progress Report.

DTIC Science & Technology

1987-10-15

polarizability of free carriers in the semiconductor perturb the index of refraction which can be detected in a Nomarski -type optical interferometer. For...interferomters. However, the charge probe relies on a different physical effect and operates by interferometrically detecting the phase change induced in an... Nomarski microscope systems. These techniques will be applied, eventually, in our real-time V.. scanning optical microscope described below. Recently

Morphological and Microstructural Evolution of Phosphorous-Rich Layer in SnAgCu/Ni-P UBM Solder Joint

NASA Astrophysics Data System (ADS)

Lin, Yung-Chi; Shih, Toung-Yi; Tien, Shih-Kang; Duh, Jenq-Gong

2007-11-01

Interfacial morphologies and microstructure of Sn-3Ag-0.5Cu/Ni-P under bump metallization (UBM) with various phosphorous contents were investigated by transmission electron microscope (TEM) and field emission electron probe microanalyzer (FE-EPMA). It was revealed that as the Ni-Sn-P compound was formed between the solder matrix and Ni-P UBM, the conventionally so-called phosphorous-rich (P-rich) layer was transformed to a series of layer compounds, including Ni3P, Ni12P5 and Ni2P. The relationship between Ni-Sn-P formation and evolution of P-rich layers was probed by electron microscopic characterization with the aid of the phase diagram of Ni-P. On the basis of the TEM micrograph, the selected area diffraction (SAD) pattern, and the FE-EPMA results, the detailed phase evolution of P-rich layers in the SnAgCu/Ni-P joint was revealed and proposed.

Effect of Yttrium Addition on the Microstructure and Mechanical Properties of Cu-Rich Nano-phase Strengthened Ferritic Steel

NASA Astrophysics Data System (ADS)

Liu, Hongyu; He, Jibai; Luan, Guoqing; Ke, Mingpeng; Fang, Haoyan; Lu, Jianduo

2018-03-01

Due to the brittle problem of Cu-rich nano-phase strengthened ferritic steel (CNSFS) after air aging, the effect of Y addition in CNSFS was systemically investigated in the present work. The microstructure, tensile fracture morphology and oxide layer of the steels were surveyed by optical microscope and scanning electron microscope. Transmission electron microscope with the combination of energy-dispersive x-ray spectroscopy and selected area electron diffraction was used to analyze the morphology, size, number density, chemical compositions and crystal structure for nano-crystalline precipitates. Microstructural examinations of the nano-crystalline precipitates show that Cu-rich precipitates and Y compounds in the range of 2-10 and 50-100 nm, respectively, form in the Y-containing steel; meanwhile, the average size of nano-crystalline precipitates in Y-containing steel is larger, but the number density is lower, and the ferritic grains are refined. Furthermore, the tensile strength and ductility of Y-containing steel after air aging are improved, whereas the tensile strength is enhanced and the ductility decreased after vacuum aging. The drag effect of Y makes the oxide layer thinner and be compacted. Tensile properties of CNSFS after air aging are improved due to the refined grains, antioxidation and purification by the addition of Y.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buck, E.C.; Cunnane, J.C.; Brown, N.R.

A combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM) is being used to determine the nature of uranium in soils from the Fernald Environmental Management Project. The information gained from these studies is being used to develop and test remediation technologies. Investigations using SEM have shown that uranium is contained within particles that are typically 1 to 100 {mu}m in diameter. Further analysis with AEM has shown that these uranium-rich regions are made up of discrete uranium-bearing phases. The distribution of these uranium phases was found to be inhomogeneous at themore » microscopic level.« less

Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

PubMed

Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

2013-01-01

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

Large volume serial section tomography by Xe Plasma FIB dual beam microscopy.

PubMed

Burnett, T L; Kelley, R; Winiarski, B; Contreras, L; Daly, M; Gholinia, A; Burke, M G; Withers, P J

2016-02-01

Ga(+) Focused Ion Beam-Scanning Electron Microscopes (FIB-SEM) have revolutionised the level of microstructural information that can be recovered in 3D by block face serial section tomography (SST), as well as enabling the site-specific removal of smaller regions for subsequent transmission electron microscope (TEM) examination. However, Ga(+) FIB material removal rates limit the volumes and depths that can be probed to dimensions in the tens of microns range. Emerging Xe(+) Plasma Focused Ion Beam-Scanning Electron Microscope (PFIB-SEM) systems promise faster removal rates. Here we examine the potential of the method for large volume serial section tomography as applied to bainitic steel and WC-Co hard metals. Our studies demonstrate that with careful control of milling parameters precise automated serial sectioning can be achieved with low levels of milling artefacts at removal rates some 60× faster. Volumes that are hundreds of microns in dimension have been collected using fully automated SST routines in feasible timescales (<24h) showing good grain orientation contrast and capturing microstructural features at the tens of nanometres to the tens of microns scale. Accompanying electron back scattered diffraction (EBSD) maps show high indexing rates suggesting low levels of surface damage. Further, under high current Ga(+) FIB milling WC-Co is prone to amorphisation of WC surface layers and phase transformation of the Co phase, neither of which have been observed at PFIB currents as high as 60nA at 30kV. Xe(+) PFIB dual beam microscopes promise to radically extend our capability for 3D tomography, 3D EDX, 3D EBSD as well as correlative tomography. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Direct-write liquid phase transformations with a scanning transmission electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Direct-write liquid phase transformations with a scanning transmission electron microscope

DOE PAGES

Unocic, Raymond R.; Lupini, Andrew R.; Borisevich, Albina Y.; ...

2016-08-03

The highly energetic electron beam from a scanning transmission electron microscope (STEM) can induce local changes in the state of matter, ranging from local knock-out and atomic movement, to amorphization/crystallization, and chemical/electrochemical reactions occuring at localized liquid-solid and gas-solid interfaces. To date, fundamental studies of e-beam induced phenomena and practical applications have been limited by conventional e-beam rastering modes that allow only for uniform e-beam exposures. Here we develop an automated liquid phase nanolithography method that is capable of directly writing nanometer scaled features within silicon nitride encapsulated liquid cells. An external beam control system, connected to the scan coilsmore » of an aberration-corrected STEM, is used to precisely control the position, dwell time, and scan velocity of a sub-nanometer STEM probe. Site-specific locations in a sealed liquid cell containing an aqueous solution of H 2PdCl 4 are irradiated to controllably deposit palladium onto silicon nitride membranes. We determine the threshold electron dose required for the radiolytic deposition of metallic palladium, explore the influence of electron dose on the feature size and morphology of nanolithographically patterned nanostructures, and propose a feedback-controlled monitoring method for active control of the nanofabricated structures through STEM detector signal monitoring. As a result, this approach enables both fundamental studies of electron beam induced interactions with matter, as well as opens a pathway to fabricate nanostructures with tailored architectures and chemistries via shape-controlled nanolithographic patterning from liquid phase precursors.« less

Use of reciprocal lattice layer spacing in electron backscatter diffraction pattern analysis

PubMed

Michael; Eades

2000-03-01

In the scanning electron microscope using electron backscattered diffraction, it is possible to measure the spacing of the layers in the reciprocal lattice. These values are of great use in confirming the identification of phases. The technique derives the layer spacing from the higher-order Laue zone rings which appear in patterns from many materials. The method adapts results from convergent-beam electron diffraction in the transmission electron microscope. For many materials the measured layer spacing compares well with the calculated layer spacing. A noted exception is for higher atomic number materials. In these cases an extrapolation procedure is described that requires layer spacing measurements at a range of accelerating voltages. This procedure is shown to improve the accuracy of the technique significantly. The application of layer spacing measurements in EBSD is shown to be of use for the analysis of two polytypes of SiC.

In situ disordering of monoclinic titanium monoxide Ti5O5 studied by transmission electron microscope TEM.

PubMed

Rempel, А А; Van Renterghem, W; Valeeva, А А; Verwerft, M; Van den Berghe, S

2017-09-07

The superlattice and domain structures exhibited by ordered titanium monoxide Ti 5 O 5 are disrupted by low energy electron beam irradiation. The effect is attributed to the disordering of the oxygen and titanium sublattices. This disordering is caused by the displacement of both oxygen and titanium atoms by the incident electrons and results in a phase transformation of the monoclinic phase Ti 5 O 5 into cubic B1 titanium monoxide. In order to determine the energies required for the displacement of titanium or oxygen atoms, i.e. threshold displacement energies, a systematic study of the disappearance of superstructure reflections with increasing electron energy and electron bombardment dose has been performed in situ in a transmission electron microscope (TEM). An incident electron energy threshold between 120 and 140 keV has been observed. This threshold can be ascribed to the displacements of titanium atoms with 4 as well as with 5 oxygen atoms as nearest neighbors. The displacement threshold energy of titanium atoms in Ti 5 O 5 corresponding with the observed incident electron threshold energy lies between 6.0 and 7.5 eV. This surprisingly low value can be explained by the presence of either one or two vacant oxygen lattice sites in the nearest neighbors of all titanium atoms.

Morphological manifestations of freezing and thawing injury in bacteriophage T4Bo.

PubMed Central

Steele, P. R.

1976-01-01

Electron microscopic observation of negatively stained preparations of frozen and thawed suspensions of T4Bo phage clearly separated the morphological changes produced produced by low-temperature salt denaturation from those produced by eutectic phase changes. Salt denaturation caused contraction of tail sheaths. Eutectic phase changes appeared to cause two separate lesions. Firstly the tail sheath was disjointed 18-22 nm. below the collar and the tail core was disjointed at 40-60 nm. below the collar, giving rise to separated heads with a small tail remnant, and separated tails in which the sheath remarkably remained in its extended form. Secondly, tears were seen in the head membranes of particles with collapsed empty heads. In all the experiments the percentage of normal phage particles counted electron-microscopically was close to the percentage of viable phage as determined by plaque assay. Images Plate 1 PMID:1068189

Analytical electron microscope study of the omega phase transformation in a zirconium-niobium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaluzec, N. J.

1979-01-01

The study of the as-quenched omega phase morphology shows that the domain size of Zr-15% Nb is on the order of 30 A. No alignment of omega domains along <222>..beta.. directions was observed and samples having undergone thermal cycling in thin foil form, did not develop a long-period structure of alternating ..beta.. and ..omega.. phases below the omega transformation temperature. (FS)

Computer synthesis of high resolution electron micrographs

NASA Technical Reports Server (NTRS)

Nathan, R.

1976-01-01

Specimen damage, spherical aberration, low contrast and noisy sensors combine to prevent direct atomic viewing in a conventional electron microscope. The paper describes two methods for obtaining ultra-high resolution in biological specimens under the electron microscope. The first method assumes the physical limits of the electron objective lens and uses a series of dark field images of biological crystals to obtain direct information on the phases of the Fourier diffraction maxima; this information is used in an appropriate computer to synthesize a large aperture lens for a 1-A resolution. The second method assumes there is sufficient amplitude scatter from images recorded in focus which can be utilized with a sensitive densitometer and computer contrast stretching to yield fine structure image details. Cancer virus characterization is discussed as an illustrative example. Numerous photographs supplement the text.

Combined use of optical and electron microscopic techniques for the measurement of hygroscopic property, chemical composition, and morphology of individual aerosol particles.

PubMed

Ahn, Kang-Ho; Kim, Sun-Man; Jung, Hae-Jin; Lee, Mi-Jung; Eom, Hyo-Jin; Maskey, Shila; Ro, Chul-Un

2010-10-01

In this work, an analytical method for the characterization of the hygroscopic property, chemical composition, and morphology of individual aerosol particles is introduced. The method, which is based on the combined use of optical and electron microscopic techniques, is simple and easy to apply. An optical microscopic technique was used to perform the visual observation of the phase transformation and hygroscopic growth of aerosol particles on a single particle level. A quantitative energy-dispersive electron probe X-ray microanalysis, named low-Z particle EPMA, was used to perform a quantitative chemical speciation of the same individual particles after the measurement of the hygroscopic property. To validate the analytical methodology, the hygroscopic properties of artificially generated NaCl, KCl, (NH(4))(2)SO(4), and Na(2)SO(4) aerosol particles of micrometer size were investigated. The practical applicability of the analytical method for studying the hygroscopic property, chemical composition, and morphology of ambient aerosol particles is demonstrated.

3D Diffraction Microscope Provides a First Deep View

NASA Astrophysics Data System (ADS)

Miao, Jianwei

2005-03-01

When a coherent diffraction pattern is sampled at a spacing sufficiently finer than the Bragg peak frequency (i.e. the inverse of the sample size), the phase information is in principle encoded inside the diffraction pattern, and can be directly retrieved by using an iterative process. In combination of this oversampling phasing method with either coherent X-rays or electrons, a novel form of diffraction microscopy has recently been developed to image nanoscale materials and biological structures. In this talk, I will present the principle of the oversampling method, discuss the first experimental demonstration of this microscope, and illustrate some applications in nanoscience and biology.

Microscopic Electron Dynamics in Metal Nanoparticles for Photovoltaic Systems.

PubMed

Kluczyk, Katarzyna; Jacak, Lucjan; Jacak, Witold; David, Christin

2018-06-25

Nanoparticles—regularly patterned or randomly dispersed—are a key ingredient for emerging technologies in photonics. Of particular interest are scattering and field enhancement effects of metal nanoparticles for energy harvesting and converting systems. An often neglected aspect in the modeling of nanoparticles are light interaction effects at the ultimate nanoscale beyond classical electrodynamics. Those arise from microscopic electron dynamics in confined systems, the accelerated motion in the plasmon oscillation and the quantum nature of the free electron gas in metals, such as Coulomb repulsion and electron diffusion. We give a detailed account on free electron phenomena in metal nanoparticles and discuss analytic expressions stemming from microscopic (Random Phase Approximation—RPA) and semi-classical (hydrodynamic) theories. These can be incorporated into standard computational schemes to produce more reliable results on the optical properties of metal nanoparticles. We combine these solutions into a single framework and study systematically their joint impact on isolated Au, Ag, and Al nanoparticles as well as dimer structures. The spectral position of the plasmon resonance and its broadening as well as local field enhancement show an intriguing dependence on the particle size due to the relevance of additional damping channels.

The high squareness Sm-Co magnet having Hcb=10.6 kOe at 150°C

NASA Astrophysics Data System (ADS)

Machida, Hiroaki; Fujiwara, Teruhiko; Kamada, Risako; Morimoto, Yuji; Takezawa, Masaaki

2017-05-01

The relationship between magnetic properties and magnetic domain structures of Sm(Fe, Cu, Zr, Co)7.5 magnet was investigated. The developed Sm-Co magnet, which is conducted homogenization heat treatment at ingot state, high temperature short time sintering and long time solid solution heat treatment showed the maximum energy product, [BH]m of 34.0 MGOe and the coercivity, Hcb of 11.3 kOe at 20°C respectively. Moreover, Hcb of 10.6 kOe at 150°C was achieved. Heat treated ingot has clear 1-7 phase in mother phase from optical microscope observation. Kerr effect microscope with magnetic field applied was used to investigate magnetic domain structure. Reverse magnetic domains were generated evenly but generation of them from inside grain were not observed. Cell structure was observed by scanning transmission electron microscope and composition analysis was conducted by energy dispersive X-ray spectroscopy. Cell size was approximately 150 ˜ 300 nm, Fe and Cu were clearly separated and concentrated to 2-17 phase and 1-5 phase respectively. Moreover, Cu concentration went up to 40 at% in 1-5 phase. That means the gap of domain wall energy between 1-5 phase and 2-17 phase was increased due to microstructure control by conducting heat treatment for compositional homogeneity.

RAPID COMMUNICATION: Study of superstructure II in multiferroic BiMnO3

NASA Astrophysics Data System (ADS)

Ge, Bing-Hui; Li, Fang-Hua; Li, Xue-Ming; Wang, Yu-Mei; Chi, Zhen-Hua; Jin, Chang-Qing

2008-09-01

The crystal structure of the minor phase, named superstructure II, existing in multiferroic compound BiMnO3 has been studied by electron diffraction and high-resolution transmission electron microscopy. Domains of major and minor phases coexisting in BiMnO3 were observed in high-resolution electron microscope images. The unit cell of minor phase was determined to be triclinic with the size 4×4×4 times as large as the distorted perovskite subcell. The [111] and [10bar 1] projected structure maps of the minor phase have been derived from the corresponding images by means of the image processing. A possible rough three-dimensional (3D) structure model was proposed based on the 3D structural information extracted from the two projected structure maps. Since there is no inversion centre in the proposed model, the minor phase may contribute to the ferroelectric property of BiMnO3.

Understanding the Magnesiothermic Reduction Mechanism of TiO2 to Produce Ti

NASA Astrophysics Data System (ADS)

Choi, Kyunsuk; Choi, Hanshin; Sohn, Il

2017-04-01

Titanium dioxide (TiO2) powders in the mineral form of rutile were reduced to metallic and an intermediate phase via a magnesiothermic reaction in molten Mg at temperatures between 973 K and 1173 K (700 °C and 900 °C) under high-purity Ar atmosphere. The reaction behavior and pathway indicated intermediate phase formation during the magnesiothermic reduction of TiO2 using XRD (X-ray diffraction), SEM (scanning electron microscope), and TEM (transmission electron microscope). Mg/TiO2 = 2 resulted in various intermediate phases of oxygen containing titanium, including Ti6O, Ti3O, and Ti2O, with metallic Ti present. MgTi2O4 ternary intermediate phases could also be observed, but they were dependent on the excess Mg present in the sample. Nevertheless, even with excessive amounts of Mg at Mg/TiO2 = 10, complete reduction to metallic Ti could not be obtained and some Ti6O intermediate phases were present. Although thermodynamics do not predict the formation of the MgTi2O4 spinel phase, detailed phase identification through XRD, SEM, and TEM showed significant amounts of this intermediate ternary phase even at excess Mg additions. Considering the stepwise reduction of TiO2 by Mg and the pronounced amounts of MgTi2O4 phase observed, the rate-limiting reaction is likely the reduction of MgTi2O4 to the TitO phase. Thus, an additional reduction step beyond thermodynamic predictions was developed.

Development program on a cold cathode electron gun

NASA Technical Reports Server (NTRS)

Spindt, C. A.; Holland, C. E.

1985-01-01

During this phase of the cathode development program, SRI improved the multiple electron beam exposure system used to print hole patterns for the cathode arrays, studied anisotropic etch processes, conducted cathode investigations using an emission microscope, reviewed possible alternate materials for cathode fabrication, studied cathode storage techniques, conducted high power operation experiments, and demonstrated high-current-density operation with small arrays of tips.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buck, E.C.; Dietz, N.L.; Bates, J.K.

Uranium contaminated soils from the Fernald Operation Site, Ohio, have been examined by a combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM). A method is described for preparing of transmission electron microscopy (TEM) thin sections by ultramicrotomy. By using these thin sections, SEM and TEM images can be compared directly. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Little uranium was associated with clays. The distribution of uranium phases was found to be inhomogeneous at the microscopic level.

Experimental realization of the Ehrenberg-Siday thought experiment

NASA Astrophysics Data System (ADS)

Pozzi, Giulio; Boothroyd, Chris B.; Tavabi, Amir H.; Yücelen, Emrah; Dunin-Borkowski, Rafal E.; Frabboni, Stefano; Gazzadi, Gian Carlo

2016-02-01

In 1949, at the end of a paper dedicated to the concept of the refractive index in electron optics, Ehrenberg and Siday noted that wave-optical effects will arise from an isolated magnetic field even when the rays themselves travel in magnetic-field-free space. They proposed a two-slit experiment, in which a magnetic flux is enclosed between interfering electron beams. Now, through access to modern nanotechnology tools, we used a focused ion beam to open two nanosized slits in a gold-coated silicon nitride membrane and focused electron beam induced deposition to fabricate a thin magnetic bar between the two slits. We then performed Fraunhofer experiments in a transmission electron microscope equipped with a field emission gun and a Lorentz lens. By tilting the specimen in the objective lens field of the electron microscope, the magnetization of the bar could be reversed and the corresponding change in the phase of the electron wave observed directly in the form of a shift in the interference fringe pattern.

Enhanced thermal stability of a polymer solar cell blend induced by electron beam irradiation in the transmission electron microscope.

PubMed

Bäcke, Olof; Lindqvist, Camilla; de Zerio Mendaza, Amaia Diaz; Gustafsson, Stefan; Wang, Ergang; Andersson, Mats R; Müller, Christian; Kristiansen, Per Magnus; Olsson, Eva

2017-05-01

We show by in situ microscopy that the effects of electron beam irradiation during transmission electron microscopy can be used to lock microstructural features and enhance the structural thermal stability of a nanostructured polymer:fullerene blend. Polymer:fullerene bulk-heterojunction thin films show great promise for use as active layers in organic solar cells but their low thermal stability is a hindrance. Lack of thermal stability complicates manufacturing and influences the lifetime of devices. To investigate how electron irradiation affects the thermal stability of polymer:fullerene films, a model bulk-heterojunction film based on a thiophene-quinoxaline copolymer and a fullerene derivative was heat-treated in-situ in a transmission electron microscope. In areas of the film that exposed to the electron beam the nanostructure of the film remained stable, while the nanostructure in areas not exposed to the electron beam underwent large phase separation and nucleation of fullerene crystals. UV-vis spectroscopy shows that the polymer:fullerene films are stable for electron doses up to 2000kGy. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhanced thermal stability of a polymer solar cell blend induced by electron beam irradiation in the transmission electron microscope.

PubMed

Bäcke, Olof; Lindqvist, Camilla; de Zerio Mendaza, Amaia Diaz; Gustafsson, Stefan; Wang, Ergang; Andersson, Mats R; Müller, Christian; Kristiansen, Per Magnus; Olsson, Eva

2017-02-01

We show by in situ microscopy that the effects of electron beam irradiation during transmission electron microscopy can be used to lock microstructural features and enhance the structural thermal stability of a nanostructured polymer:fullerene blend. Polymer:fullerene bulk-heterojunction thin films show great promise for use as active layers in organic solar cells but their low thermal stability is a hindrance. Lack of thermal stability complicates manufacturing and influences the lifetime of devices. To investigate how electron irradiation affects the thermal stability of polymer:fullerene films, a model bulk-heterojunction film based on a thiophene-quinoxaline copolymer and a fullerene derivative was heat-treated in-situ in a transmission electron microscope. In areas of the film that exposed to the electron beam the nanostructure of the film remained stable, while the nanostructure in areas not exposed to the electron beam underwent large phase separation and nucleation of fullerene crystals. UV-vis spectroscopy shows that the polymer:fullerene films are stable for electron doses up to 2000kGy. Copyright © 2017 Elsevier B.V. All rights reserved.

New trend in electron holography

NASA Astrophysics Data System (ADS)

Tanigaki, Toshiaki; Harada, Ken; Murakami, Yasukazu; Niitsu, Kodai; Akashi, Tetsuya; Takahashi, Yoshio; Sugawara, Akira; Shindo, Daisuke

2016-06-01

Electron holography using a coherent electron wave is a promising technique for high-resolution visualization of electromagnetic fields in and around objects. The capability of electron holography has been enhanced by the development of new technologies and has thus become an even more powerful tool for exploring scientific frontiers. This review introduces these technologies including split-illumination electron holography and vector-field electron tomography. Split-illumination electron holography, which uses separated coherent waves, overcomes the limits imposed by the lateral coherence requirement for electron waves in electron holography. Areas that are difficult to observe using conventional electron holography are now observable. Exemplified applications include observing a singular magnetic domain wall in electrical steel sheets, local magnetizations at anti-phase boundaries, and electrostatic potentials in metal-oxide-semiconductor field-effect transistors. Vector-field electron tomography can be used to visualize magnetic vectors in three dimensions. Two components of the vectors are reconstructed using dual-axis tomography, and the remaining one is calculated using div B   =  0. A high-voltage electron microscope can be used to achieve precise magnetic reconstruction. For example, magnetic vortices have been visualized using a 1 MV holography electron microscope.

Sub-nanometre resolution imaging of polymer-fullerene photovoltaic blends using energy-filtered scanning electron microscopy.

PubMed

Masters, Robert C; Pearson, Andrew J; Glen, Tom S; Sasam, Fabian-Cyril; Li, Letian; Dapor, Maurizio; Donald, Athene M; Lidzey, David G; Rodenburg, Cornelia

2015-04-24

The resolution capability of the scanning electron microscope has increased immensely in recent years, and is now within the sub-nanometre range, at least for inorganic materials. An equivalent advance has not yet been achieved for imaging the morphologies of nanostructured organic materials, such as organic photovoltaic blends. Here we show that energy-selective secondary electron detection can be used to obtain high-contrast, material-specific images of an organic photovoltaic blend. We also find that we can differentiate mixed phases from pure material phases in our data. The lateral resolution demonstrated is twice that previously reported from secondary electron imaging. Our results suggest that our energy-filtered scanning electron microscopy approach will be able to make major inroads into the understanding of complex, nano-structured organic materials.

Nanoscale amorphization of GeTe nanowire with conductive atomic force microscope.

PubMed

Kim, JunHo

2014-10-01

We fabricated GeTe nanowires by using Au catalysis mediated vapor-liquid-solid method. The fabricated nanowires were confirmed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. For a nanowire with - 150 nm diameter, we performed amorphization experiment with conductive atomic force microscope. We examined the structural change of the nanowire with several bias voltages from 0 V to 10 V. Above bias voltage of 6-7 V, some points of the nanowire showed transition to amorphous phase. The consumed energy for the amorphization was estimated to be 4-5 nJ, which was close to the other result of nanowire tested with a four probe device.

Surface Modifications with Laser Synthesized Mo Modified Coating

NASA Astrophysics Data System (ADS)

Sun, Lu; Chen, Hao; Liu, Bo

2013-01-01

Mg-Cu-Al was first used to improve the surface performance of TA15 titanium alloys by means of laser cladding technique. The synthesis of hard composite coating on TA15 titanium alloy by laser cladding of Mg-Cu-Al-B4C/Mo pre-placed powders was investigated by means of scanning electron microscope, energy dispersive spectrometer and high resolution transmission electron microscope. Experimental results indicated that such composite coating mainly consisted of TiB2, TiB, TiC, Ti3Al and AlCuMg. Compared with TA15 alloy substrate, an improvement of wear resistance was observed for this composite coating due to the actions of fine grain, amorphous and hard phase strengthening.

Magnetic properties of Y3+ doped Bi4-xTi2FeO12 aurivillius phase ceramics

NASA Astrophysics Data System (ADS)

Tirupathi, Patri; Reddy, H. Satish Kumar; Babu, P. D.

2018-05-01

In the present paper reports a comprehensive investigation of structural, microstructural and magnetic phase transition in Y3+ doped BITF Aurivillius phase compounds. The study of surface morphology by scanning electron microscope reveals the growth of plate-like grains and further the grain size increase with increasing Y3+ composition. Low temperature magnetic studies reveals enhanced magnetic property with doping of Y3+ in BITF. It was explained by considering exchange interaction between the neighboring Fe+3 ions via electron trapped electrons at oxygen vacancies. Temperature dependent dc-magnetic studies exhibit a magnetic transitions TC = 750 K for x=0.0 TC ˜ 674 K for x=1.0 & TC ˜ 645 K for x=1.50 ceramics respectively in high temperature magnetization studies

Ginzburg-Landau Theory for Flux Phase and Superconductivity in t-J Model

NASA Astrophysics Data System (ADS)

Kuboki, Kazuhiro

2018-02-01

Ginzburg-Landau (GL) equations and GL free energy for flux phase and superconductivity are derived microscopically from the t-J model on a square lattice. Order parameter (OP) for the flux phase has direct coupling to a magnetic field, in contrast to the superconducting OP which has minimal coupling to a vector potential. Therefore, when the flux phase OP has unidirectional spatial variation, staggered currents would flow in a perpendicular direction. The derived GL theory can be used for various problems in high-Tc cuprate superconductors, e.g., states near a surface or impurities, and the effect of an external magnetic field. Since the GL theory derived microscopically directly reflects the electronic structure of the system, e.g., the shape of the Fermi surface that changes with doping, it can provide more useful information than that from phenomenological GL theories.

Microscopic and histochemical manifestations of hyaline cartilage dynamics.

PubMed

Malinin, G I; Malinin, T I

1999-01-01

Structure and function of hyaline cartilages has been the focus of many correlative studies for over a hundred years. Much of what is known regarding dynamics and function of cartilage constituents has been derived or inferred from biochemical and electron microscopic investigations. Here we show that in conjunction with ultrastructural, and high-magnification transmission light and polarization microscopy, the well-developed histochemical methods are indispensable for the analysis of cartilage dynamics. Microscopically demonstrable aspects of cartilage dynamics include, but are not limited to, formation of the intracellular liquid crystals, phase transitions of the extracellular matrix and tubular connections between chondrocytes. The role of the interchondrocytic liquid crystals is considered in terms of the tensegrity hypothesis and non-apoptotic cell death. Phase transitions of the extracellular matrix are discussed in terms of self-alignment of chondrons, matrix guidance pathways and cartilage growth in the absence of mitosis. The possible role of nonenzymatic glycation reactions in cartilage dynamics is also reviewed.

Microscopic 3D measurement of dynamic scene using optimized pulse-width-modulation binary fringe

NASA Astrophysics Data System (ADS)

Hu, Yan; Chen, Qian; Feng, Shijie; Tao, Tianyang; Li, Hui; Zuo, Chao

2017-10-01

Microscopic 3-D shape measurement can supply accurate metrology of the delicacy and complexity of MEMS components of the final devices to ensure their proper performance. Fringe projection profilometry (FPP) has the advantages of noncontactness and high accuracy, making it widely used in 3-D measurement. Recently, tremendous advance of electronics development promotes 3-D measurements to be more accurate and faster. However, research about real-time microscopic 3-D measurement is still rarely reported. In this work, we effectively combine optimized binary structured pattern with number-theoretical phase unwrapping algorithm to realize real-time 3-D shape measurement. A slight defocusing of our proposed binary patterns can considerably alleviate the measurement error based on phase-shifting FPP, making the binary patterns have the comparable performance with ideal sinusoidal patterns. Real-time 3-D measurement about 120 frames per second (FPS) is achieved, and experimental result of a vibrating earphone is presented.

Electronic Phase Separation in Iron Selenide (Li,Fe)OHFeSe Superconductor System

NASA Astrophysics Data System (ADS)

Mao, Yiyuan; Li, Jun; Huan, Yulong; Yuan, Jie; Li, Zi-an; Chai, Ke; Ma, Mingwei; Ni, Shunli; Tian, Jinpeng; Liu, Shaobo; Zhou, Huaxue; Zhou, Fang; Li, Jianqi; Zhang, Guangming; Jin, Kui; Dong, Xiaoli; Zhao, Zhongxian

2018-05-01

The phenomenon of phase separation into antiferromagnetic (AFM) and superconducting (SC) or normal-state regions has great implication for the origin of high-temperature (high-Tc) superconductivity. However, the occurrence of an intrinsic antiferromagnetism above the Tc of (Li, Fe)OHFeSe superconductor is questioned. Here we report a systematic study on a series of (Li, Fe)OHFeSe single crystal samples with Tc up to ~41 K. We observe an evident drop in the static magnetization at Tafm ~125 K, in some of the SC (Tc < ~38 K, cell parameter c < ~9.27 {\\AA}) and non-SC samples. We verify that this AFM signal is intrinsic to (Li, Fe)OHFeSe. Thus, our observations indicate mesoscopic-to-macroscopic coexistence of an AFM state with the normal (below Tafm) or SC (below Tc) state in (Li, Fe)OHFeSe. We explain such coexistence by electronic phase separation, similar to that in high-Tc cuprates and iron arsenides. However, such an AFM signal can be absent in some other samples of (Li, Fe)OHFeSe, particularly it is never observed in the SC samples of Tc > ~38 K, owing to a spatial scale of the phase separation too small for the macroscopic magnetic probe. For this case, we propose a microscopic electronic phase separation. It is suggested that the microscopic static phase separation reaches vanishing point in high-Tc (Li, Fe)OHFeSe, by the occurrence of two-dimensional AFM spin fluctuations below nearly the same temperature as Tafm reported previously for a (Li, Fe)OHFeSe (Tc ~42 K) single crystal. A complete phase diagram is thus established. Our study provides key information of the underlying physics for high-Tc superconductivity.

Scanning electron microscopy of a pink inclusion from the Allende meteorite

NASA Technical Reports Server (NTRS)

Grossman, L.; Fruland, R. M.; Mckay, D. S.

1975-01-01

A scanning electron microscope study of a fine-grained, pin, Ca-rich inclusion from the Allende meteorite has revealed strong evidence for direct condensation of its constituent minerals from a vapor. This observation extends to the alkali-bearing phases in addition to the Ca-, Al-silicates and suggests that the feldspathoids as well as the refractory silicates are solar nebular condensates.

Highlighting material structure with transmission electron diffraction correlation coefficient maps.

PubMed

Kiss, Ákos K; Rauch, Edgar F; Lábár, János L

2016-04-01

Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. Copyright © 2016 Elsevier B.V. All rights reserved.

Majorana Kramers pairs in Rashba double nanowires with interactions and disorder

NASA Astrophysics Data System (ADS)

Thakurathi, Manisha; Simon, Pascal; Mandal, Ipsita; Klinovaja, Jelena; Loss, Daniel

2018-01-01

We analyze the effects of electron-electron interactions and disorder on a Rashba double-nanowire setup coupled to an s -wave superconductor, which has been recently proposed as a versatile platform to generate Kramers pairs of Majorana bound states in the absence of magnetic fields. We identify the regime of parameters for which these Kramers pairs are stable against interaction and disorder effects. We use bosonization, perturbative renormalization group, and replica techniques to derive the flow equations for various parameters of the model and evaluate the corresponding phase diagram with topological and disorder-dominated phases. We confirm aforementioned results by considering a more microscopic approach, which starts from the tunneling Hamiltonian between the three-dimensional s -wave superconductor and the nanowires. We find again that the interaction drives the system into the topological phase and, as the strength of the source term coming from the tunneling Hamiltonian increases, strong electron-electron interactions are required to reach the topological phase.

The effect of aging treatment on the fracture toughness and impact strength of injection molded Ni-625 superalloy parts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Özgün, Özgür, E-mail: oozgun@bingol.edu.tr; Yılmaz, Ramazan; Özkan Gülsoy, H.

In this study, the effect of aging heat treatment on fracture toughness and impact strength of Ni-625 superalloy fabricated by using powder injection molding (PIM) method was examined. After a feedstock was prepared by mixing the prealloyed Ni-625 superalloy powder, which was fabricated by gas atomisation, with a polymeric binder system and then it was granulated, it was shaped through the use of injection. The molded specimens were sintered at 1300 °C for 3 h after a two-stage debinding process. Once the sintered specimens were treated in the solution at 1150 °C for 2 h, they were quenched. Aging treatmentmore » was performed by keeping specimens at 745 °C for 22 h. Fracture toughness and impact tests were performed on sintered and aged specimens. Microstructure examinations were performed by using optical microscope, scanning electron microscope, and transmission electron microscope. The results revealed that aging heat treatment led to the formation of some carbides and intermetallic phases in the microstructure. While the hardness of the aged specimens increased due to these phases, their fracture toughness and impact strength values decreased. - Highlights: • Ni-625 superalloy components were produced by means of powder injection molding. • The produced components were subjected to aging treatment. • Aging process provided approximately 50% increase in the hardness of components. • Intermetallic precipitates, carbides and TCP phases occurred within the aged parts. • Fracture toughness and impact strength values decreased due to the hard phases.« less

Laboratory Instruments Available to Support Space Station Researchers at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Panda, Binayak; Gorti, Sridhar

2013-01-01

A number of research instruments are available at NASA's Marshall Space Flight Center (MSFC) to support ISS researchers and their investigations. These modern analytical tools yield valuable and sometimes new informative resulting from sample characterization. Instruments include modern scanning electron microscopes equipped with field emission guns providing analytical capabilities that include angstron-level image resolution of dry, wet and biological samples. These microscopes are also equipped with silicon drift X-ray detectors (SDD) for fast yet precise analytical mapping of phases, as well as electron back-scattered diffraction (EBSD) units to map grain orientations in crystalline alloys. Sample chambers admit large samples, provide variable pressures for wet samples, and quantitative analysis software to determine phase relations. Advances in solid-state electronics have also facilitated improvements for surface chemical analysis that are successfully employed to analyze metallic materials and alloys, ceramics, slags, and organic polymers. Another analytical capability at MSFC is a mganetic sector Secondary Ion Mass Spectroscopy (SIMS) that quantitatively determines and maps light elements such as hydrogen, lithium, and boron along with their isotopes, identifies and quantifies very low level impurities even at parts per billion (ppb) levels. Still other methods available at MSFC include X-ray photo-electron spectroscopy (XPS) that can determine oxidation states of elements as well as identify polymers and measure film thicknesses on coated materials, Scanning Auger electron spectroscopy (SAM) which combines surface sensitivity, spatial lateral resolution (approximately 20 nm), and depth profiling capabilities to describe elemental compositions in near surface regions and even the chemical state of analyzed atoms. Conventional Transmission Electron Microscope (TEM) for observing internal microstructures at very high magnifications and the Electron Probe Micro-analyzer (EPMA) for very precise microanalysis are available as needed by the researcher. Space Station researchers are invited to work with MSFC in analyzing their samples using these techniques.

Reconstructing the microstructure of polyimide-silicalite mixed-matrix membranes and their particle connectivity using FIB-SEM tomography.

PubMed

Diblíková, P; Veselý, M; Sysel, P; Čapek, P

2018-03-01

Properties of a composite material made of a continuous matrix and particles often depend on microscopic details, such as contacts between particles. Focusing on processing raw focused-ion beam scanning electron microscope (FIB-SEM) tomography data, we reconstructed three mixed-matrix membrane samples made of 6FDA-ODA polyimide and silicalite-1 particles. In the first step of image processing, backscattered electron (BSE) and secondary electron (SE) signals were mixed in a ratio that was expected to obtain a segmented 3D image with a realistic volume fraction of silicalite-1. Second, after spatial alignment of the stacked FIB-SEM data, the 3D image was smoothed using adaptive median and anisotropic nonlinear diffusion filters. Third, the image was segmented using the power watershed method coupled with a seeding algorithm based on geodesic reconstruction from the markers. If the resulting volume fraction did not match the target value quantified by chemical analysis of the sample, the BSE and SE signals were mixed in another ratio and the procedure was repeated until the target volume fraction was achieved. Otherwise, the segmented 3D image (replica) was accepted and its microstructure was thoroughly characterized with special attention paid to connectivity of the silicalite phase. In terms of the phase connectivity, Monte Carlo simulations based on the pure-phase permeability values enabled us to calculate the effective permeability tensor, the main diagonal elements of which were compared with the experimental permeability. In line with the hypothesis proposed in our recent paper (Čapek, P. et al. (2014) Comput. Mater. Sci. 89, 142-156), the results confirmed that the existence of particle clusters was a key microstructural feature determining effective permeability. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Electron density distribution in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides studied by double nuclear magnetic resonance methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piskunov, Yu. V., E-mail: piskunov@imp.uran.ru; Ogloblichev, V. V.; Arapova, I. Yu.

2011-11-15

The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of {sup 17}O are measured systematically, and the contributions from {sup 17}O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detectedmore » in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of {sup 17}O-{sup 207}Pb and {sup 17}O-{sup 121}Sb are measured in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin {sup 17}O-{sup 207}Pb interaction are determined as functions of the local Knight shift {sub 207}Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of {sup 17}O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides.« less

Characterization of LiBC by phase-contrast scanning transmission electron microscopy.

PubMed

Krumeich, Frank; Wörle, Michael; Reibisch, Philipp; Nesper, Reinhard

2014-08-01

LiBC was used as a model compound for probing the applicability of phase-contrast (PC) imaging in an aberration-corrected scanning transmission electron microscope (STEM) to visualize lithium distributions. In the LiBC structure, boron and carbon are arranged to hetero graphite layers between which lithium is incorporated. The crystal structure is reflected in the PC-STEM images recorded perpendicular to the layers. The experimental images and their defocus dependence match with multi-slice simulations calculated utilizing the reciprocity principle. The observation that a part of the Li positions is not occupied is likely an effect of the intense electron beam triggering Li displacement. Copyright © 2013 Elsevier Ltd. All rights reserved.

High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy.

PubMed

Tate, Mark W; Purohit, Prafull; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

2016-02-01

We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.

Design of an electrostatic phase shifting device for biological transmission electron microscopy.

PubMed

Koeck, Philip J B

2018-04-01

I suggest an electrostatic phase plate designed to broaden the contrast transfer function of a transmission electron microscope operated close to Scherzer defocus primarily in the low resolution direction. At higher defocus the low frequency behavior is equal to that close to Scherzer defocus, but CTF-correction becomes necessary to extend image interpretation to higher resolution. One simple realization of the phase plate consists of two ring shaped electrodes symmetrically surrounding the central beam. Since no physical components come into contact with the central beam and charge on the electrodes is controlled by an external voltage supply, problems with uncontrolled charging are expected to be reduced. Copyright © 2018 Elsevier B.V. All rights reserved.

Microstructure characterization of Al matrix composite reinforced with Ti-6Al-4V meshes after compression by scanning electron microscope and transmission electron microscope.

PubMed

Guo, Q; Sun, D L; Han, X L; Cheng, S R; Chen, G Q; Jiang, L T; Wu, G H

2012-02-01

Compressive properties of Al matrix composite reinforced with Ti-6Al-4V meshes (TC4(m)/5A06 Al composite) under the strain rates of 10(-3)S(-1) and 1S(-1) at different temperature were measured and microstructure of composites after compression was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compressive strength decreased with the test temperature increased and the strain-rate sensitivity (R) of composite increased with the increasing temperature. SEM observations showed that grains of Al matrix were elongated severely along 45° direction (angle between axis direction and fracture surface) and TC4 fibres were sheared into several parts in composite compressed under the strain rate of 10(-3)S(-1) at 25°C and 250°C. Besides, amounts of cracks were produced at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al(6) phases. With the compressive temperature increasing to 400°C, there was no damage at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al(6) phases, while equiaxed recrystal grains with sizes about 10 μm at the original grain boundaries of Al matrix were observed. However, interface separation of TC4 fibres and Al matrix occurred in composite compressed under the strain rate of 1S(-1) at 250°C and 400°C. With the compressive temperature increasing from 25°C to 100°C under the strain rate of 10(-3) S(-1), TEM microstructure in Al matrix exhibited high density dislocations and slipping bands (25°C), polygonized dislocations and dynamic recovery (100°C), equiaxed recrystals with sizes below 500 μm (250°C) and growth of equiaxed recrystals (400°C), respectively. Copyright © 2011 Elsevier Ltd. All rights reserved.

Probing the limits of the rigid-intensity-shift model in differential-phase-contrast scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Clark, L.; Brown, H. G.; Paganin, D. M.; Morgan, M. J.; Matsumoto, T.; Shibata, N.; Petersen, T. C.; Findlay, S. D.

2018-04-01

The rigid-intensity-shift model of differential-phase-contrast imaging assumes that the phase gradient imposed on the transmitted probe by the sample causes the diffraction pattern intensity to shift rigidly by an amount proportional to that phase gradient. This behavior is seldom realized exactly in practice. Through a combination of experimental results, analytical modeling and numerical calculations, using as case studies electron microscope imaging of the built-in electric field in a p-n junction and nanoscale domains in a magnetic alloy, we explore the breakdown of rigid-intensity-shift behavior and how this depends on the magnitude of the phase gradient and the relative scale of features in the phase profile and the probe size. We present guidelines as to when the rigid-intensity-shift model can be applied for quantitative phase reconstruction using segmented detectors, and propose probe-shaping strategies to further improve the accuracy.

Sculpting Nanoscale Functional Channels in Complex Oxides Using Energetic Ions and Electrons

DOE PAGES

Sachan, Ritesh; Zarkadoula, Eva; Ou, Xin; ...

2018-04-26

The formation of metastable phases has attracted significant attention because of their unique properties and potential functionalities. In the present study, we demonstrate the phase conversion of energetic-ion-induced amorphous nanochannels/tracks into a metastable defect fluorite in A 2B 2O 7 structured complex oxides by electron irradiation. Through in situ electron irradiation experiments in a scanning transmission electron microscope, we observe electron-induced epitaxial crystallization of the amorphous nanochannels in Yb 2Ti 2O 7 into the defect fluorite. This energetic-electron-induced phase transformation is attributed to the coupled effect of ionization-induced electronic excitations and local heating, along with subthreshold elastic energy transfers. Wemore » also show the role of ionic radii of A-site cations (A = Yb, Gd, and Sm) and B-site cations (Ti and Zr) in facilitating the electron-beam-induced crystallization of the amorphous phase to the defect-fluorite structure. The formation of the defect-fluorite structure is eased by the decrease in the difference between ionic radii of A- and B-site cations in the lattice. Molecular dynamics simulations of thermal annealing of the amorphous phase nanochannels in A 2B 2O 7 draw parallels to the electron-irradiation-induced crystallization and confirm the role of ionic radii in lowering the barrier for crystallization. Furthermore, these results suggest that employing guided electron irradiation with atomic precision is a useful technique for selected area phase formation in nanoscale printed devices.« less

Sculpting Nanoscale Functional Channels in Complex Oxides Using Energetic Ions and Electrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sachan, Ritesh; Zarkadoula, Eva; Ou, Xin

The formation of metastable phases has attracted significant attention because of their unique properties and potential functionalities. In the present study, we demonstrate the phase conversion of energetic-ion-induced amorphous nanochannels/tracks into a metastable defect fluorite in A 2B 2O 7 structured complex oxides by electron irradiation. Through in situ electron irradiation experiments in a scanning transmission electron microscope, we observe electron-induced epitaxial crystallization of the amorphous nanochannels in Yb 2Ti 2O 7 into the defect fluorite. This energetic-electron-induced phase transformation is attributed to the coupled effect of ionization-induced electronic excitations and local heating, along with subthreshold elastic energy transfers. Wemore » also show the role of ionic radii of A-site cations (A = Yb, Gd, and Sm) and B-site cations (Ti and Zr) in facilitating the electron-beam-induced crystallization of the amorphous phase to the defect-fluorite structure. The formation of the defect-fluorite structure is eased by the decrease in the difference between ionic radii of A- and B-site cations in the lattice. Molecular dynamics simulations of thermal annealing of the amorphous phase nanochannels in A 2B 2O 7 draw parallels to the electron-irradiation-induced crystallization and confirm the role of ionic radii in lowering the barrier for crystallization. Furthermore, these results suggest that employing guided electron irradiation with atomic precision is a useful technique for selected area phase formation in nanoscale printed devices.« less

Immobilization and stretching of 5'-pyrene-terminated DNA on carbon film deposited on electron microscope grid.

PubMed

Loukanov, Alexandre; Filipov, Chavdar; Lecheva, Marta; Emin, Saim

2015-11-01

The immobilization and stretching of randomly coiled DNA molecules on hydrophobic carbon film is a challenging microscopic technique, which possess various applications, especially for genome sequencing. In this report the pyrenyl nucleus is used as an anchor moiety to acquire higher affinity of double stranded DNA to the graphite surface. DNA and pyrene are joined through a linker composed of four aliphatic methylene groups. For the preparation of pyrene-terminated DNA a multifunctional phosphoramidite monomer compound was designed. It contains pyrenylbutoxy group as an anchor moiety for π-stacking attachment to the carbon film, 2-cyanoethyloxy, and diisopropylamino as coupling groups for conjugation to activated oligonucleotide chain or DNA molecule. This monomer derivative was suitable for incorporation into automated solid-phase DNA synthesis and was attached to the 5' terminus of the DNA chain through a phosphodiester linkage. The successful immobilization and stretching of pyrene-terminated DNA was demonstrated by conventional 100 kV transmission electron microscope. The microscopic analysis confirmed the stretched shape of the negatively charged nucleic acid pieces on the hydrophobic carbon film. © 2015 Wiley Periodicals, Inc.

Physical and Microstructure Properties of MgAl2C2 Matrix Composite Coating on Titanium

NASA Astrophysics Data System (ADS)

Li, Peng

2014-12-01

This work is based on the dry sliding wear of the MgAl2C2-TiB2-FeSi composite coating deposited on a pure Ti using a laser cladding technique. Scanning electron microscope images indicate that the nanocrystals and amorphous phases are produced in such coating. X-ray diffraction result indicated that such coating mainly consists of MgAl2C2, Ti-B, Ti-Si, Fe-Al, Ti3SiC2, TiC and amorphous phases. The high resolution transmission electron microscope image indicated that the TiB nanorods were produced in the coating, which were surrounded by other fine precipitates, favoring the formation of a fine microstructure. With increase of the laser power from 0.85 kW to 1.00 kW, the micro-hardness decreased from 1350 1450 HV0.2 to 1200 1300 HV0.2. The wear volume loss of the laser clad coating was 1/7 of pure Ti.

Dopant concentration dependent growth of Fe:ZnO nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahai, Anshuman; Goswami, Navendu, E-mail: navendugoswami@gmail.com

2016-05-23

Systematic investigations of structural properties of 1-10% Fe doped ZnO nanostructure (Fe:ZnO NS) prepared via chemical precipitation method have been reported. Structural properties were probed thoroughly employing scanning electron microscope (SEM) and transmission electron microscope (TEM), energy dispersive X-ray (EDAX) analysis and X-ray diffraction (XRD). Morphological transformation of nanostructures (NS) with Fe incorporation is evident in SEM/TEM images. Nanoparticles (NP) obtained with 1% Fe, evolve to nanorods (NR) for 3% Fe; NR transform to nanocones (NC) (for 5% and 7% Fe) and finally NC transform to nanoflakes (NF) at 10% Fe. Morover, primary phase of Zn{sub 1-x}Fe{sub x}O along withmore » secondary phases of ZnFe{sub 2}O{sub 4} and Fe{sub 2}O{sub 3} were also revealed through XRD measurements. Based on collective XRD, SEM, TEM, and EDAX interpretations, a model for morphological evolution of NS was proposed and the pivotal role of Fe dopant was deciphered.« less

Spectral Interferometry with Electron Microscopes

PubMed Central

Talebi, Nahid

2016-01-01

Interference patterns are not only a defining characteristic of waves, but also have several applications; characterization of coherent processes and holography. Spatial holography with electron waves, has paved the way towards space-resolved characterization of magnetic domains and electrostatic potentials with angstrom spatial resolution. Another impetus in electron microscopy has been introduced by ultrafast electron microscopy which uses pulses of sub-picosecond durations for probing a laser induced excitation of the sample. However, attosecond temporal resolution has not yet been reported, merely due to the statistical distribution of arrival times of electrons at the sample, with respect to the laser time reference. This is however, the very time resolution which will be needed for performing time-frequency analysis. These difficulties are addressed here by proposing a new methodology to improve the synchronization between electron and optical excitations through introducing an efficient electron-driven photon source. We use focused transition radiation of the electron as a pump for the sample. Due to the nature of transition radiation, the process is coherent. This technique allows us to perform spectral interferometry with electron microscopes, with applications in retrieving the phase of electron-induced polarizations and reconstructing dynamics of the induced vector potential. PMID:27649932

Low-Density, Refractory Multi-Principal Element Alloys of the Cr-Nb-Ti-V-Zr System: Microstructure and Phase Analysis (Postprint)

DTIC Science & Technology

2012-12-19

remelted five times, being flipped for each melt, and was in a liquid state for about 5 min during each melting event. The pre- pared cigar -shaped...section surfaces using a 136 Vickers diamond pyramid under a 500 g load applied for 20 s. The micro- structure was analyzed by scanning electron ...microscopy (SEM) using a Quanta 600F scanning electron microscope (FEI, North America NanoPort, Hillsboro, OR) equipped with backscatter electron (BSE

Initial formation of calcite crystals in the thin prismatic layer with the periostracum of Pinctada fucata.

PubMed

Suzuki, Michio; Nakayama, Seiji; Nagasawa, Hiromichi; Kogure, Toshihiro

2013-02-01

Although the formation mechanism of calcite crystals in the prismatic layer has been studied well in many previous works, the initial state of calcite formation has not been observed in detail using electron microscopes. In this study, we report that the soft prismatic layer with transparent color (the thin prismatic layer) in the tip of the fresh shell of Pinctada fucata was picked up to observe the early calcification phase. A scanning electron microscope (SEM) image showed that the growth tip of the thin prismatic layer was covered by the periostracum, which was also where the initial formation of calcite crystals began. A cross-section containing the thin calcite crystals in the thin prismatic layer with the periostracum was made using a focused ion beam (FIB) system. In a transmission electron microscope (TEM) observation, the thin calcite crystal (thickness is about 1μm) on the periostracum was found to be a single crystal with the c-axis oriented perpendicular to the shell surface. On the other hand, many aggregated small particles consisting of bassanite crystals were observed in the periostracum suggesting the possibility that not only organic sulfate but also inorganic sulfates exist in the prismatic layer. These discoveries in the early calcification phase of the thin prismatic layer may help to clarify the mechanism of regulating the nucleation and orientation of the calcite crystal in the shell. Copyright © 2012 Elsevier Ltd. All rights reserved.

Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites

PubMed Central

Li, Feng; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

2018-01-01

Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca3(PO4)2, TixPy, and Ti3O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed. PMID:29659504

Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites.

PubMed

Li, Feng; Jiang, Xiaosong; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

2018-04-16

Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca₃(PO₄)₂, Ti x P y , and Ti₃O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

Sub-nanometre resolution imaging of polymer–fullerene photovoltaic blends using energy-filtered scanning electron microscopy

PubMed Central

Masters, Robert C.; Pearson, Andrew J.; Glen, Tom S.; Sasam, Fabian-Cyril; Li, Letian; Dapor, Maurizio; Donald, Athene M.; Lidzey, David G.; Rodenburg, Cornelia

2015-01-01

The resolution capability of the scanning electron microscope has increased immensely in recent years, and is now within the sub-nanometre range, at least for inorganic materials. An equivalent advance has not yet been achieved for imaging the morphologies of nanostructured organic materials, such as organic photovoltaic blends. Here we show that energy-selective secondary electron detection can be used to obtain high-contrast, material-specific images of an organic photovoltaic blend. We also find that we can differentiate mixed phases from pure material phases in our data. The lateral resolution demonstrated is twice that previously reported from secondary electron imaging. Our results suggest that our energy-filtered scanning electron microscopy approach will be able to make major inroads into the understanding of complex, nano-structured organic materials. PMID:25906738

Multiorbital kinetic effects on charge ordering of frustrated electrons on the triangular lattice

NASA Astrophysics Data System (ADS)

Février, C.; Fratini, S.; Ralko, A.

2015-06-01

The role of the multiorbital effects on the emergence of frustrated electronic orders on the triangular lattice at half filling is investigated through an extended spinless fermion Hubbard model. By using two complementary approaches, unrestricted Hartree-Fock and exact diagonalizations, we unravel a very rich phase diagram controlled by the strength of both local and off-site Coulomb interactions and by the interorbital hopping anisotropy ratio t'/t . Three robust unconventional electronic phases, a pinball liquid, an inverse pinball liquid, and a large-unit-cell √{12 }×√{12 } droplet phase, are found to be generic in the triangular geometry, being controlled by the band structure parameters. The latter are also stabilized in the isotropic limit of our microscopic model, which recovers the standard SU(2) spinful extended single-band Hubbard model.

Meretrix lusoria--a natural biocomposite material: in situ analysis of hierarchical fabrication and micro-hardness.

PubMed

Zhu, Zhihong; Tong, Hua; Ren, Yaoyao; Hu, Jiming

2006-01-01

The ultrastructure of clam (Meretrix lusoria) was investigated by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction analyzer (XRD) combining with in situ texture decalcified technique and the micro-hardness of clam was determined, in order to understand the spatial relationship between the mineral phase and organic matrix and further explain the correlation between the property and structure. The results showed that hierarchical fabrication is the major structure character of this mollusc shell. There is specific braided structure forming from domains composed of needle-like structure made up of the single crystal of aragonite. High magnification TEM image of clam indicates the intracrystal region of the aragonite single crystal is made up of subgrain phase and some amorphous substance. There are various crystal grain growth preferential orientations in the different growth direction of the shell. An amount of organic microtubule distribute evenly in the base of calcium carbonate as reinforcement phase. The mechanical property of this natural biological composite is better than other aragonite layer of mollusc shells and pearls according to the data of micro-hardness testing. The braided structure and organic microtubule reinforcement phase are responsible for its high mechanical performance. The stereo hierarchical fabrication of clam was elucidated for the first time.

[Study on thaspine in inducing apoptosis of A549 cell].

PubMed

Zhang, Yan-min; He, Lang-chong

2007-04-01

To investigate the effect of thaspine on the cellular proliferation, apoptosis and cell cycle in A549 cell line. A549 cell was cultured with different concentrations of thaspine. Cellular proliferation was detected with MTT, apoptosis and cell cycle were checked with Flow Cytometer, and change of microstructure was observed by transmission electron microscope. Thaspine could inhibit the proliferation and induce apoptosis of A549 cell in a time-dose dependent manner. Cell cycle was significantly stopped at the S phase by thaspine with FCM technology. Under electronic microscope, the morphology of A549 cell showed nuclear karyopycnosis, chromatin agglutination and typical apoptotic body when the cell was treated with thaspine. Thaspine has the effects of anti-tumor and inducing apoptosis.

Direct Observation Through In Situ Transmission Electron Microscope of Early States of Crystallization in Nanoscale Metallic Glasses

NASA Astrophysics Data System (ADS)

Xie, Y.; Sohn, S.; Schroers, J.; Cha, J. J.

2017-11-01

Crystallization is a complex process that involves multiscale physics such as diffusion of atomic species over multiple length scales, thermodynamic energy considerations, and multiple possible intermediate states. In situ crystallization experiments inside a transmission electron microscope (TEM) using nanostructured metallic glasses (MGs) provide a unique platform to study directly crystallization kinetics and pathways. Here, we study the embryonic state of eutectic growth using Pt-Ni-Cu-P MG nanorods under in situ TEM. We directly observe the nucleation and growth of a Ni-rich polymorphic phase, followed by the nucleation and slower growth of a Cu-rich phase. The suppressed growth kinetics of the Cu-rich phase is attributed to locally changing chemical compositions. In addition, we show that growth can be controlled by incorporation of an entire nucleus instead of individual atoms. Such a nucleus has to align with the crystallographic orientation of a larger grain before it can be incorporated into the crystal. By directly observing the crystallization processes, particularly the early stages of non-polymorphic growth, in situ TEM crystallization studies of MG nanostructures provide a wealth of information, some of which can be applied to typical bulk crystallization.

Morphology and kinetics of crystals growth in amorphous films of Cr2O3, deposited by laser ablation

NASA Astrophysics Data System (ADS)

Bagmut, Aleksandr

2018-06-01

An electron microscopic investigation was performed on the structure and kinetics of the crystallization of amorphous Cr2O3 films, deposited by pulsed laser sputtering of chromium target in an oxygen atmosphere. The crystallization was initiated by the action of an electron beam on an amorphous film in the column of a transmission electron microscope. The kinetic curves were plotted on the basis of a frame-by-frame analysis of the video recorded during the crystallization of the film. It was found that the amorphous phase - crystal phase transition in Cr2O3 films occurs as a layer polymorphic crystallization and is characterized by the values of the dimensionless relative length unit δ0 ≈ 2000-3100. The action of the electron beam initiates the formation of crystals of two basic morphological forms: disk-shaped and sickle-shaped. Growth of a disk-shaped crystals is characterized by a constant rate v and the quadratic dependence of the fraction of the crystalline phase x on the time t. Sickle-shaped crystal at an initial stage, as it grows, becomes as ring-shaped and disk-shaped crystal. The growth of a sickle-shaped crystal is characterized by normal and tangential velocity components, which depend on the time as ∼√t and as ∼1/√t respectively The end point of the arc at the interface between the amorphous and crystalline phases as the crystal grows describes a curve, which is similar to the Fermat helix. For sickle-shaped, as well as for disk-shaped crystals, the degree of crystallinity x ∼ t2.

High-resolution electron microscopy observation of a new crystalline approximant W' of Mg-Zn-Y icosahedral quasicrystal

PubMed

Luo; Hashimoto

2000-10-01

A new ordered structure W' with a lattice parameter (a = 2.05 nm) about three times as large as that of the fundamental face-centered cubic W phase (a = 0.6848 nm) has been found in the Mg-Zn-Y system by means of transmission electron microscopy. The W' and W phases have the cube-to-cube orientation relationship. Moreover, the strong electron diffraction spots of the W' phase showed pseudoicosahedral symmetry, implying that it is a crystalline approximant of the Mg-Zn-Y icosahedral quasicrystal. In the high-resolution electron microscopic images of the W' phase, Penrose tiles of pentagons and boats with an edge length of a(p) = 0.481 nm can be identified. A binary tile of crown subunit has also been deduced from such a tiling. Translation domains of the W' phase have also been observed and the translation vectors at the domain boundary are: a(p), tau x a(p) and (1 + tau) x a(p), respectively, where (1 + tau) x a(p) equals to the edge length a(r) of the big obtuse rhombus of the W' phase and tau = (1 + square root of 5)/2, is the golden ratio.

Effect of nano BiPb-2212 phase addition on BiPb-2223 phase properties

NASA Astrophysics Data System (ADS)

Mohammed, N. H.; Abou-Aly, A. I.; Barakat, M. Me.; Hassan, M. S.

2018-06-01

BiPb-2212 phase in nanoscale was added to BiPb-2223 phase with a general stoichiometry of (Bi1.7Pb0.4Sr2.1Ca1.1Cu2.1O8+δ)x/Bi1.8Pb0.4Sr2.0Ca2.0Cu3.2O10+δ, 0.0 ≤ x  ≤ 2.5 wt.%. All samples were prepared by the standard solid-state reaction method. The prepared nano BiPb-2212 phase was characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM). The prepared samples were characterized by XRD and the scanning electron microscope (SEM). XRD analysis indicated that the sample with x = 1.5 wt.% has the highest relative volume fraction for BiPb-2223 phase. Samples were examined by electrical resistivity and I-V measurements. There is no significant change in the superconducting transition temperature Tc for all samples. The highest critical current density Jc was recorded for the sample with x = 1.5 wt.%. The normalized excess conductivity (Δσ/σroom) was calculated according to Aslamazov-Larkin (AL) model. Four different fluctuating regions were recorded as the temperature decreased. The coherence length along the c-axis at 0 K ξc(0), interlayer coupling strength s, Fermi velocity vF of the carriers and Fermi energy EF were calculated for both samples with x = 0.0 wt.% and 1.5 wt.%.

Final Report, Fundamental Mechanisms of Transient States in Materials Quantified by DTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, G. H.; McKeown, J. T.

At the project’s inception, there was growing evidence that the time domain for in situ observations of material evolution held great promise for allowing measurements to be made in never previously contemplated regimes. Also, central to the development of the project was the knowledge that phase transformations are of central importance to the development of materials microstructure and hence properties. We addressed this opportunity by developing a transmission electron microscope that could be operated in the pulsed mode (DTEM), with exposure times down to 20 ns and interframe times down to 20 ns in the nine-frame movie mode, designed withmore » the intent of performing in situ experiments. This unprecedented capability allowed us to investigate structural phase transformations, intermetallic formation reactions, crystallization from the amorphous phase, rapid solidification of liquid metals, transformations in phase change materials, and catalyst nanoparticles. The ability of the electron microscope to create images with high spatial resolution allows for the accurate measurement of position. Common to all of the transformations mentioned above is the presence of a distinct interface between the old phase and the growing new phase. Measuring the position of the interface as a function of time, combined with the ability to count nucleation sites as a function of time, allowed for the exceptionally accurate measure of transformation kinetics. These measurements were used to guide and constrain the development of models and simulation methods for the classes of transformations studied.« less

Advantages of intermediate X-ray energies in Zernike phase contrast X-ray microscopy.

PubMed

Wang, Zhili; Gao, Kun; Chen, Jian; Hong, Youli; Ge, Xin; Wang, Dajiang; Pan, Zhiyun; Zhu, Peiping; Yun, Wenbing; Jacobsen, Chris; Wu, Ziyu

2013-01-01

Understanding the hierarchical organizations of molecules and organelles within the interior of large eukaryotic cells is a challenge of fundamental interest in cell biology. Light microscopy is a powerful tool for observations of the dynamics of live cells, its resolution attainable is limited and insufficient. While electron microscopy can produce images with astonishing resolution and clarity of ultra-thin (<1 μm thick) sections of biological specimens, many questions involve the three-dimensional organization of a cell or the interconnectivity of cells. X-ray microscopy offers superior imaging resolution compared to light microscopy, and unique capability of nondestructive three-dimensional imaging of hydrated unstained biological cells, complementary to existing light and electron microscopy. Until now, X-ray microscopes operating in the "water window" energy range between carbon and oxygen k-shell absorption edges have produced outstanding 3D images of cryo-preserved cells. The relatively low X-ray energy (<540 eV) of the water window imposes two important limitations: limited penetration (<10 μm) not suitable for imaging larger cells or tissues, and small depth of focus (DoF) for high resolution 3D imaging (e.g., ~1 μm DoF for 20 nm resolution). An X-ray microscope operating at intermediate energy around 2.5 keV using Zernike phase contrast can overcome the above limitations and reduces radiation dose to the specimen. Using a hydrated model cell with an average chemical composition reported in literature, we calculated the image contrast and the radiation dose for absorption and Zernike phase contrast, respectively. The results show that an X-ray microscope operating at ~2.5 keV using Zernike phase contrast offers substantial advantages in terms of specimen size, radiation dose and depth-of-focus. Copyright © 2012 Elsevier Inc. All rights reserved.

Chiral Majorana fermion modes regulated by a scanning tunneling microscope tip

NASA Astrophysics Data System (ADS)

Zhou, Yan-Feng; Hou, Zhe; Zhang, Ying-Tao; Sun, Qing-Feng

2018-03-01

The Majorana fermion can be described by a real wave function with only two phases (zero and π ) which provide a controllable degree of freedom. We propose a strategy to regulate the phase of the chiral Majorana state by coupling with a scanning tunneling microscope tip in a system consisting of a quantum anomalous Hall insulator coupled with a superconductor. With the change in the chemical potential, the chiral Majorana state can be tuned alternately between zero and π , in which the perfect normal tunneling and perfect crossed Andreev reflection appear, respectively. The perfect crossed Andreev reflection, by which a Cooper pair can be split into two electrons going into different terminals completely, leads to a pumping current and distinct quantized resistances. These findings may provide a signature of Majorana fermions and pave a feasible avenue to regulate the phase of the Majorana state.

Science 101: How Does an Electron Microscope Work?

ERIC Educational Resources Information Center

Robertson, Bill

2013-01-01

Contrary to popular opinion, electron microscopes are not used to look at electrons. They are used to look for structure in things that are too small to observe with an optical microscope, or to obtain images that are magnified much more than is obtainable with an optical microscope. To understand how electron microscopes work, it will help to go…

Dynamic nano-imaging of label-free living cells using electron beam excitation-assisted optical microscope

PubMed Central

Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu

2015-01-01

Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications. PMID:26525841

Dynamic nano-imaging of label-free living cells using electron beam excitation-assisted optical microscope.

PubMed

Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu

2015-11-03

Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications.

Dynamic nano-imaging of label-free living cells using electron beam excitation-assisted optical microscope

NASA Astrophysics Data System (ADS)

Fukuta, Masahiro; Kanamori, Satoshi; Furukawa, Taichi; Nawa, Yasunori; Inami, Wataru; Lin, Sheng; Kawata, Yoshimasa; Terakawa, Susumu

2015-11-01

Optical microscopes are effective tools for cellular function analysis because biological cells can be observed non-destructively and non-invasively in the living state in either water or atmosphere condition. Label-free optical imaging technique such as phase-contrast microscopy has been analysed many cellular functions, and it is essential technology for bioscience field. However, the diffraction limit of light makes it is difficult to image nano-structures in a label-free living cell, for example the endoplasmic reticulum, the Golgi body and the localization of proteins. Here we demonstrate the dynamic imaging of a label-free cell with high spatial resolution by using an electron beam excitation-assisted optical (EXA) microscope. We observed the dynamic movement of the nucleus and nano-scale granules in living cells with better than 100 nm spatial resolution and a signal-to-noise ratio (SNR) around 10. Our results contribute to the development of cellular function analysis and open up new bioscience applications.

Microstructural Study of 17-4PH Stainless Steel after Plasma-Transferred Arc Welding.

PubMed

Deng, Dewei; Chen, Rui; Sun, Qi; Li, Xiaona

2015-01-29

The improvement of the surface qualities and surface hardening of precipitation hardened martensitic stainless steel 17-4PH was achieved by the plasma-transferred arc welding (PTAW) process deposited with Co-based alloy. The microstructure of the heat affected zone (HAZ) and base metal were characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that there are obvious microstructural differences between the base metal and HAZ. For example, base material is transformed from lath martensite to austenite due to the heateffect of the welding process. On the other hand, the precipitate in the matrix (bar-like shape Cr₇C₃ phase with a width of about one hundred nanometres and a length of hundreds of nanometres) grows to a rectangular appearance with a width of about two hundred nanometres and a length of about one micron. Stacking fault could also be observed in the Cr₇C₃ after PTAW. The above means that welding can obviously improve the surface qualities.

Investigation of the {Fe}/{Si} interface and its phase transformations

NASA Astrophysics Data System (ADS)

Fanciulli, M.; Degroote, S.; Weyer, G.; Langouche, G.

1997-04-01

Thin 57Fe films (3-10 Å) have been grown by molecular beam epitaxy (MBE) on (7 × 7) reconstructed Si(111) and (2 × 1) reconstructed Si(001) surfaces and by e-gun evaporation on an H-terminated Si(111) surface. Conversion electron Mössbauer spectroscopy (CEMS) with high statistical accuracy and resolution allowed a detailed microscopic investigation of the silicide formation mechanism and of the structural phase transformations upon annealing.

Effect of Iron Oxide and Phase Separation on the Color of Blue Jun Ware Glaze.

PubMed

Wang, Fen; Yang, Changan; Zhu, Jianfeng; Lin, Ying

2015-09-01

Based on the traditional Jun ware glaze, the imitated Jun ware glazes were prepared by adding iron oxide and introducing phase separation agent apatite through four-angle-method. The effect of iron oxide contents, phase separation and the firing temperature on the color of Jun ware glazes were investigated by a neutral atmosphere experiment, optical microscope and scanning electronic microscope. The results showed that the colorant, mainly Fe2O3, contributed to the Jun ware glaze blue and cyan colors of Jun ware glaze. The light scatter caused by the small droplets in phase separation structure only influenced the shade of the glaze color, intensify or weaken the color, and thus made the glaze perfect and elegant opal visual effects, but was not the origin of general blue or cyan colors of Jun ware glaze. In addition, the firing temperature and the basic glaze composition affected the glaze colors to some extent.

Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ming, Fangfei; Mulugeta Amare, Daniel; Tu, Weisong

Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Itsmore » formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.« less

Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping

DOE PAGES

Ming, Fangfei; Mulugeta Amare, Daniel; Tu, Weisong; ...

2017-03-07

Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Itsmore » formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.« less

Invited Review Article: Methods for imaging weak-phase objects in electron microscopy

PubMed Central

Glaeser, Robert M.

2013-01-01

Contrast has traditionally been produced in electron-microscopy of weak phase objects by simply defocusing the objective lens. There now is renewed interest, however, in using devices that apply a uniform quarter-wave phase shift to the scattered electrons relative to the unscattered beam, or that generate in-focus image contrast in some other way. Renewed activity in making an electron-optical equivalent of the familiar “phase-contrast” light microscope is based in part on the improved possibilities that are now available for device microfabrication. There is also a better understanding that it is important to take full advantage of contrast that can be had at low spatial frequency when imaging large, macromolecular objects. In addition, a number of conceptually new phase-plate designs have been proposed, thus increasing the number of options that are available for development. The advantages, disadvantages, and current status of each of these options is now compared and contrasted. Experimental results that are, indeed, superior to what can be accomplished with defocus-based phase contrast have been obtained recently with two different designs of phase-contrast aperture. Nevertheless, extensive work also has shown that fabrication of such devices is inconsistent, and that their working lifetime is short. The main limitation, in fact, appears to be electrostatic charging of any device that is placed into the electron diffraction pattern. The challenge in fabricating phase plates that are practical to use for routine work in electron microscopy thus may be more in the area of materials science than in the area of electron optics. PMID:24289381

Microstructure characterization of LAE442 magnesium alloy processed by extrusion and ECAP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minárik, Peter; Král, Robert; Pešička, Josef

2016-02-15

The magnesium alloy LAE442 was processed by extrusion and equal channel angular pressing (ECAP) to achieve ultrafine grained microstructure. Detailed characterization of the microstructure was performed by scanning electron microscope, electron back scattered diffraction (EBSD) and transmission electron microscope. The initial, as-cast, microstructure consisted of large grains of ~ 1 mm. The grain refinement due to the processing by severe plastic deformation led to a decrease of the average grain size to ~ 1.7 μm after the final step of ECAP. A detailed characterization of secondary phases showed the precipitation of Al{sub 11}RE{sub 3}, Al{sub 2}Ca and Al{sub 10}RE{sub 2}Mn{submore » 7} intermetallic phases. X-ray diffraction measurements proved that Li is dissolved within the magnesium matrix in the as-cast condition. Newly formed Al{sub 3}Li phase was observed after ECAP. The texture formation due to the extrusion and ECAP was different from that in the other magnesium alloys due to the activation of non-basal slip systems as a result of the decrease of the c/a ratio. - Highlights: • Combined extrusion and equal channel angular pressing results in significant grain refinement by factor 1000 approximately. • Al{sub 11}RE{sub 3}, Al{sub 2}Ca and Al{sub 10}RE{sub 2}Mn{sub 7} secondary phases are present in the as-cast material while Li was dissolved in the Mg matrix. • Extrusion and ECAP have no effect on the composition of the secondary phases but they influence strongly their distribution. • Texture evolution is affected by decrease of c/a ratio due to the presence of Li and resulting activation of non-basal slip.« less

CYTOPLASMIC FILAMENTS OF AMOEBA PROTEUS

PubMed Central

Pollard, Thomas D.; Ito, Susumu

1970-01-01

The role of filaments in consistency changes and movement in a motile cytoplasmic extract of Amoeba proteus was investigated by correlating light and electron microscopic observations with viscosity measurements. The extract is prepared by the method of Thompson and Wolpert (1963). At 0°C, this extract is nonmotile and similar in structure to ameba cytoplasm, consisting of groundplasm, vesicles, mitochondria, and a few 160 A filaments. The extract undergoes striking ATP-stimulated streaming when warmed to 22°C. Two phases of movement are distinguished. During the first phase, the apparent viscosity usually increases and numerous 50–70 A filaments appear in samples of the extract prepared for electron microscopy, suggesting that the increase in viscosity in caused, at least in part, by the formation of these thin filaments. During this initial phase of ATP-stimulated movement, these thin filaments are not detectable by phase-contrast or polarization microscopy, but later, in the second phase of movement, 70 A filaments aggregate to form birefringent microscopic fibrils. A preparation of pure groundplasm with no 160 A filaments or membranous organelles exhibits little or no ATP-stimulated movement, but 50–70 A filaments form and aggregate into birefringent fibrils. This observation and the structural relationship of the 70 A and the 160 A filaments in the motile extract suggest that both types of filaments may be required for movement. These two types of filaments, 50–70 A and 160 A, are also present in the cytoplasm of intact amebas. Fixed cells could not be used to study the distribution of these filaments during natural ameboid movement because of difficulties in preserving the normal structure of the ameba during preparation for electron microscopy. PMID:4915451

Cytoplasmic filaments of Amoeba proteus. I. The role of filaments in consistency changes and movement.

PubMed

Pollard, T D; Ito, S

1970-08-01

The role of filaments in consistency changes and movement in a motile cytoplasmic extract of Amoeba proteus was investigated by correlating light and electron microscopic observations with viscosity measurements. The extract is prepared by the method of Thompson and Wolpert (1963). At 0 degrees C, this extract is nonmotile and similar in structure to ameba cytoplasm, consisting of groundplasm, vesicles, mitochondria, and a few 160 A filaments. The extract undergoes striking ATP-stimulated streaming when warmed to 22 degrees C. Two phases of movement are distinguished. During the first phase, the apparent viscosity usually increases and numerous 50-70 A filaments appear in samples of the extract prepared for electron microscopy, suggesting that the increase in viscosity in caused, at least in part, by the formation of these thin filaments. During this initial phase of ATP-stimulated movement, these thin filaments are not detectable by phase-contrast or polarization microscopy, but later, in the second phase of movement, 70 A filaments aggregate to form birefringent microscopic fibrils. A preparation of pure groundplasm with no 160 A filaments or membranous organelles exhibits little or no ATP-stimulated movement, but 50-70 A filaments form and aggregate into birefringent fibrils. This observation and the structural relationship of the 70 A and the 160 A filaments in the motile extract suggest that both types of filaments may be required for movement. These two types of filaments, 50-70 A and 160 A, are also present in the cytoplasm of intact amebas. Fixed cells could not be used to study the distribution of these filaments during natural ameboid movement because of difficulties in preserving the normal structure of the ameba during preparation for electron microscopy.

Site preference of alloying elements in DO22-Ni3V phase: Phase-field and first-principles study

NASA Astrophysics Data System (ADS)

Zhang, Ding-Ni; Shangguan, Qian-Qian; Liu, Fu; Zhang, Ming-Yi

2015-07-01

Site preference of alloying elements in DO22-Ni3V phase was investigated using phase-field and first-principles method. The concentrations of alloying elements on sublattices of DO22-Ni3V phase were quantitatively studied using phase-field model based on microscopic diffusion equations. The phase-field computation results demonstrate that the concentration differences of alloying elements on the NiI and NiII site are attributed to the coordination environment difference. Host atoms Ni and substitutional ternary additions Al prefer to occupy NiI site. Antisite atoms V show site preference on the NiII site. Further reason of site preference of alloying elements on the two different Ni sites were studied using first-principles method to calculate the electronic structure of DO22-Ni3V phase. Calculation of density of states, orbitals population and charge population of the optimized Ni3V structure found that the electronic structures of NiI and NiII sites are different. Electronic structure difference, which is caused by coordination environment difference, is the essential reason for site selectivity behaviors of alloying elements on NiI and NiII sites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, J.; Sun, K.; Yin, W. -G.

The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here, we provide direct observations of the evolution of the superstructure in La 1/3Ca 2/3MnO 3 in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystalmore » (ELC) phases. Furthermore, our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations.« less

Stable room-temperature ferromagnetic phase at the FeRh(100) surface

DOE PAGES

Pressacco, Federico; Uhlir, Vojtech; Gatti, Matteo; ...

2016-03-03

Interfaces and low dimensionality are sources of strong modifications of electronic, structural, and magnetic properties of materials. FeRh alloys are an excellent example because of the first-order phase transition taking place at ~400 K from an antiferromagnetic phase at room temperature to a high temperature ferromagnetic one. It is accompanied by a resistance change and volume expansion of about 1%. We have investigated the electronic and magnetic properties of FeRh(100) epitaxially grown on MgO by combining spectroscopies characterized by different probing depths, namely X-ray magnetic circular dichroism and photoelectron spectroscopy. Furthermore, we find that the symmetry breaking induced at themore » Rh-terminated surface stabilizes a surface ferromagnetic layer involving five planes of Fe and Rh atoms in the nominally antiferromagnetic phase at room temperature. First-principles calculations provide a microscopic description of the structural relaxation and the electron spin-density distribution that support the experimental findings.« less

Ultrafast structural and electronic dynamics of the metallic phase in a layered manganite

PubMed Central

Piazza, L.; Ma, C.; Yang, H. X.; Mann, A.; Zhu, Y.; Li, J. Q.; Carbone, F.

2013-01-01

The transition between different states in manganites can be driven by various external stimuli. Controlling these transitions with light opens the possibility to investigate the microscopic path through which they evolve. We performed femtosecond (fs) transmission electron microscopy on a bi-layered manganite to study its response to ultrafast photoexcitation. We show that a photoinduced temperature jump launches a pressure wave that provokes coherent oscillations of the lattice parameters, detected via ultrafast electron diffraction. Their impact on the electronic structure are monitored via ultrafast electron energy loss spectroscopy, revealing the dynamics of the different orbitals in response to specific structural distortions. PMID:26913564

Bio-inspired sustainable and green synthesis of plasmonic Ag/AgCl nanoparticles for enhanced degradation of organic compound from aqueous phase.

PubMed

Devi, Th Babita; Ahmaruzzaman, M

2016-09-01

In the current study, we report the utilization of the biogenic potential of Benincasa hispida (ash gourd) peel extract for the synthesis of Ag embedded AgCl nanoparticles nanoparticles (Ag/AgCl NPs) without the use of any external organic solvents. The appearance of dark brown color from the pale yellow color confirmed the formation of Ag/AgCl nanoparticles which was further validated by absorbance peak using UV-visible spectroscopy. The phytochemicals (flavones) present in the B. hispida peel extract acts as a reducing/stabilizing agents. The morphology and size of the synthesized NPs were characterized by transmission electron microscope (TEM), selected area electron microscope (SAED) and high resolution transmission electron microscope (HR-TEM). FT-IR spectra of the B. hispida peel extract and after the development of nanoparticles are determined to identify the functional groups responsible for the conversion of metal ions to metal nanoparticles. The synthesized nanoparticles showed an excellent photocatalytic property in the degradation of toxic dye like malachite green oxalate under sunlight irradiation. For the first time, malachite green oxalate dye was degraded by Ag/AgCl nanoparticles under sunlight irradiation.

Microscopic theory of longitudinal sound velocity in charge ordered manganites.

PubMed

Rout, G C; Panda, S

2009-10-14

A microscopic theory of longitudinal sound velocity in a manganite system is reported here. The manganite system is described by a model Hamiltonian consisting of charge density wave (CDW) interaction in the e(g) band, an exchange interaction between spins of the itinerant e(g) band electrons and the core t(2g) electrons, and the Heisenberg interaction of the core level spins. The magnetization and the CDW order parameters are considered within mean-field approximations. The phonon Green's function was calculated by Zubarev's technique and hence the longitudinal velocity of sound was finally calculated for the manganite system. The results show that the elastic spring involved in the velocity of sound exhibits strong stiffening in the CDW phase with a decrease in temperature as observed in experiments.

Electron and Cooper-pair transport across a single magnetic molecule explored with a scanning tunneling microscope

NASA Astrophysics Data System (ADS)

Brand, J.; Gozdzik, S.; Néel, N.; Lado, J. L.; Fernández-Rossier, J.; Kröger, J.

2018-05-01

A scanning tunneling microscope is used to explore the evolution of electron and Cooper-pair transport across single Mn-phthalocyanine molecules adsorbed on Pb(111) from tunneling to contact ranges. Normal-metal as well as superconducting tips give rise to a gradual transition of the Bardeen-Cooper-Schrieffer energy gap in the tunneling range into a zero-energy resonance close to and at contact. Supporting transport calculations show that in the normal-metal-superconductor junctions this resonance reflects the merging of in-gap Yu-Shiba-Rusinov states as well as the onset of Andreev reflection. For the superconductor-superconductor contacts, the zero-energy resonance is rationalized in terms of a finite Josephson current that is carried by phase-dependent Andreev and Yu-Shiba-Rusinov levels.

Microstructure and physical properties of laser Zn modified amorphous-nanocrystalline coating on a titanium alloy

NASA Astrophysics Data System (ADS)

Li, Jia-Ning; Gong, Shui-Li; Shi, Yi-Ning; Suo, Hong-Bo; Wang, Xi-Chang; Deng, Yun-Hua; Shan, Fei-Hu; Li, Jian-Quan

2014-02-01

A Zn modified amorphous-nanocrystalline coating was fabricated on a Ti-6Al-4V alloy by laser cladding of the Co-Ti-B4C-Zn-Y2O3 mixed powders. Such coating was researched by means of a scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM), etc. Experimental results indicated that the Co5Zn21 and TiB2 nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation, and TiB2 grew along (010), (111) and (024). The Co5Zn21 nanocrystals were produced attached to the ceramics, which mainly consisted of the Co nanoparticles embedded in a heterogeneous zinc, and had varied crystalline orientations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Migunov, V., E-mail: v.migunov@fz-juelich.de; Dunin-Borkowski, R. E.; London, A.

The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electricmore » field and electrostatic potential around the needle with ∼10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.« less

Photoluminescence investigation of type-II GaSb/GaAs quantum dots grown by liquid phase epitaxy

NASA Astrophysics Data System (ADS)

Wang, Yang; Hu, Shuhong; Xie, Hao; Lin, Hongyu; lu, Hongbo; Wang, Chao; Sun, Yan; Dai, Ning

2018-06-01

GaSb quantum dots (QDs) with an areal density of ∼1 × 1010 cm-2 are successfully grown by the modified (rapid slider) liquid phase epitaxy technique. The morphology of the QDs has been investigated by scanning electron microscope (SEM) and atom force microscope (AFM). The power-dependence and temperature-dependence photoluminescence (PL) spectra have been studied. The bright room-temperature PL suggests a good luminescence quality of GaSb QDs/GaAs matrix system. The type-II alignment of the GaSb QDs/GaAs matrix system is verified by the blue-shift of the QDs peak with the increase of excitation power. From the temperature-dependence PL spectra, the activation energy of QDs is determined to be 111 meV.

Martensitic transformation and phase diagram in ternary Co-V-Ga Heusler alloys

NASA Astrophysics Data System (ADS)

Xu, Xiao; Nagashima, Akihide; Nagasako, Makoto; Omori, Toshihiro; Kanomata, Takeshi; Kainuma, Ryosuke

2017-03-01

We report the martensitic transformation behavior in Co-V-Ga Heusler alloys. Thermoanalysis and thermomagnetization measurements were conducted to observe the martensitic transformation. By using a transmission electron microscope and an in situ X-ray diffractometer, martensitic transformation was found to occur from the L21 Heusler parent phase to the D022 martensite phase. Phase diagrams were determined for two pseudo-binary sections where martensitic transformation was detected. Magnetic properties, including the Curie temperatures and spontaneous magnetization of the parent phase, were also investigated. The magnetic properties showing behaviors different from those of NiMn-based alloys were found.

Mechanically controlling the reversible phase transformation from zinc blende to wurtzite in AlN

DOE PAGES

Li, Zhen; Yadav, Satyesh; Chen, Youxing; ...

2017-04-10

III–V and other binary octet semiconductors often take two phase forms—wurtzite (wz) and zinc blende (zb) crystal structures—with distinct functional performance at room temperature. Here, we investigate how to control the synthesized phase structure to either wz or zb phase by tuning the interfacial strain by taking AlN as a representative III–V compound. Furthermore, by applying in situ mechanical tests at atomic scale in a transmission electron microscope, we observed the reversible phase transformation from zb to wz, and characterized the transition path—the collective glide of Shockley partials on every two {111} planes of the zb AlN.

Microencapsulated Phase-Change Materials For Storage Of Heat

NASA Technical Reports Server (NTRS)

Colvin, David P.

1989-01-01

Report describes research on engineering issues related to storage and transport of heat in slurries containing phase-change materials in microscopic capsules. Specific goal of project to develop lightweight, compact, heat-management systems used safely in inhabited areas of spacecraft. Further development of obvious potential of technology expected to lead to commercialization and use in aircraft, electronic equipment, machinery, industrial processes, and other sytems in which requirements for management of heat compete with severe restrictions on weight or volume.

Carbide and nitride precipitation during laser cladding of Inconel 718 alloy coatings

NASA Astrophysics Data System (ADS)

Zhang, Yaocheng; Li, Zhuguo; Nie, Pulin; Wu, Yixiong

2013-11-01

The microstructure of the laser clad Inconel 718 alloy coating was observed by scanning electron microscope (SEM). The chemical composition of precipitation phases was investigated by energy dispersive spectrometer (EDS) and solid phase microextraction (SPME). The crystal structure and lattice constants of precipitation are determined by transmission electron microscope (TEM). Vickers hardness of the coatings and the nanohardness of the interstitial phases were measured. The insular carbide (MC) and the tetragonal nitride (MN) with face-centered cubic (FCC) structure are rich in Ti and Nb but depleted in Ni, Fe and Cr due to the interdiffusion and redistribution of alloying elements between MC and MN and supersaturated matrix. MC and MN were precipitated in the forms of (Nb0.12Ti0.88)C1.5 and (Nb0.88Ti0.12)N1.5, and the Gibbs free energies of formation can be expressed as Δ G [ (Nb0.12Ti0.88)C1.5 ] 0 = - 122.654 - 3.1332 T (kJ /mol) and Δ G [ (Nb0.88Ti0.12)N1.5 ] 0 = - 157.814 - 3.0251 T (kJ /mol). The nanohardness and Young's modulus of the MC and MN were much higher than the matrix, and the plastic deformation energy of interstitial phases was lower than the matrix. The precipitation of MC and MN is beneficial to the mechanical properties of coating.

Thermodynamic analysis and purifying an amorphous phase of frozen crystallization centers

NASA Astrophysics Data System (ADS)

Lysov, V. I.; Tsaregradskaya, T. L.; Turkov, O. V.; Saenko, G. V.

2017-12-01

The possibility of dissolving frozen crystallization centers in amorphous alloys of the Fe-B system is considered by means of thermodynamic calculations. This can in turn improve the thermal stability of an amorphous alloy. The effect isothermal annealing has on the thermal stability of multicomponent amorphous alloys based on iron is investigated via the highly sensitive dilatometric technique, measurements of microsolidity, and electron microscopic investigations. The annealing temperature is determined empirically on the basis of the theses of the thermodynamic theory of the high temperature stability of multicomponent amorphous alloys, according to which there exists a range of temperatures that is characterized by a negative difference between the chemical potentials of phases in a heterogeneous amorphous matrix-frozen crystallization centers system. The thermodynamic condition of the possible dissolution of frozen crystallization centers is thus met. It is shown that introducing regimes of thermal processing allows us to expand the ranges of the thermal stability of iron-based amorphous alloys by 20-40 K through purifying an amorphous matrix of frozen crystallization centers. This conclusion is proved via electron microscopic investigations.

Microstructure & properties of SiC-AlN multiphase ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Y.B.; Tan, S.H.; Jiang, D.L.

It is that AlN and SiC mixture could form solid solution at the temperature from 1800{degrees}C to 2100{degrees}C, its result will be conducive to important benefits for the improving to study and develop on the silicon carbide ceramics. The effect of AlN as a mainly additive phase on silicon carbide ceramic were investigated in this paper. For the optimum hot press(HP) process, SiC and AlN mixture formed solid solution at the 1950{degrees}C--2050{degrees}C in Ar environment. The properties of SiC-AlN composition were that bending strength more than 600 MPa and fracture toughness more than 7 MPa.m{sup 1/2} at the room temperature(R.T)more » could be received, at the same time the strength hold ascertain value from R.T. to 1400{degrees}C in air. The dense samples were examined by metallograph, X-ray diffraction (XRD), scanning electron microscope (SEM) & transmission electron microscope (TEM) to determine the fracture structure, interface phase, crack spread etc.« less

Comparative study of image contrast in scanning electron microscope and helium ion microscope.

PubMed

O'Connell, R; Chen, Y; Zhang, H; Zhou, Y; Fox, D; Maguire, P; Wang, J J; Rodenburg, C

2017-12-01

Images of Ga + -implanted amorphous silicon layers in a 110 n-type silicon substrate have been collected by a range of detectors in a scanning electron microscope and a helium ion microscope. The effects of the implantation dose and imaging parameters (beam energy, dwell time, etc.) on the image contrast were investigated. We demonstrate a similar relationship for both the helium ion microscope Everhart-Thornley and scanning electron microscope Inlens detectors between the contrast of the images and the Ga + density and imaging parameters. These results also show that dynamic charging effects have a significant impact on the quantification of the helium ion microscope and scanning electron microscope contrast. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

In situ study of single-walled carbon nanotube growth in an environmental scanning electron microscope.

PubMed

Mehedi, H-A; Ravaux, J; Tahir, S; Podor, R; Jourdain, V

2016-12-16

Monitoring individual single-walled carbon nanotubes (SWCNTs) during their growth is a highly sought-after goal in view of understanding the processes involved in the nucleation, elongation and termination which ultimately control the diameter and chiral selectivity. Here, we report on the first truly in situ observations of SWCNT growth in an environmental scanning electron microscope (ESEM). The CNT growth from lithographically patterned catalysts was investigated as a function of the catalyst type (Fe, Co or Ni), temperature, type of precursor (ethanol or acetylene), gas phase composition and pressure, and pretreatment conditions, and we report on the most appropriate conditions for SWCNT growth in ESEM conditions. We show that this approach allows the observation at the submicron scale of the different steps of the nanotube synthesis including the catalyst reduction, the growth and percolation of the nanotube network, and the deposition of individual nanotubes grown in the gas phase on the substrate. Despite these obvious advantages, we identified a few limitations which will need to be tackled for fully taking advantage of the approach, for instance for monitoring the growth of individual SWCNTs by ESEM, including the short lifetime of the catalyst nanoparticles, the preference for kite growth (by opposition to surface growth) and the influence of the electron beam on the nanotube growth.

Mechanical Alloying of W-Mo-V-Cr-Ta High Entropy Alloys

NASA Astrophysics Data System (ADS)

Das, Sujit; Robi, P. S.

2018-04-01

Recent years have seen the emergence of high-entropy alloys (HEAs) consisting of five or more elements in equi-atomic or near equi-atomic ratios. These alloys in single phase solid solution exhibit exceptional mechanical properties viz., high strength at room and elevated temperatures, reasonable ductility and stable microstructure over a wide range of temperatures making it suitable for high temperature structural materials. In spite of the attractive properties, processing of these materials remains a challenge. Reports regarding fabrication and characterisation of a few refractory HEA systems are available. The processing of these alloys have been carried out by arc melting of small button sized materials. The present paper discusses the development of a novel refractory W-Mo-V-Cr-Ta HEA powder based on a new alloy design concept. The powder mixture was milled for time periods up to 64 hours. Single phase alloy powder having body centred cubic structure was processed by mechanical alloying. The milling characteristics and extent of alloying during the ball milling were characterized using X-ray diffractiometre (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). A single phase solid solution alloy powder having body-centred cubic (BCC) structure with a lattice parameter of 3.15486 Å was obtained after milling for 32 hours.

Nickel/Platinum Dual Silicide Axial Nanowire Heterostructures with Excellent Photosensor Applications.

PubMed

Wu, Yen-Ting; Huang, Chun-Wei; Chiu, Chung-Hua; Chang, Chia-Fu; Chen, Jui-Yuan; Lin, Ting-Yi; Huang, Yu-Ting; Lu, Kuo-Chang; Yeh, Ping-Hung; Wu, Wen-Wei

2016-02-10

Transition metal silicide nanowires (NWs) have attracted increasing attention as they possess advantages of both silicon NWs and transition metals. Over the past years, there have been reported with efforts on one silicide in a single silicon NW. However, the research on multicomponent silicides in a single silicon NW is still rare, leading to limited functionalities. In this work, we successfully fabricated β-Pt2Si/Si/θ-Ni2Si, β-Pt2Si/θ-Ni2Si, and Pt, Ni, and Si ternary phase axial NW heterostructures through solid state reactions at 650 °C. Using in situ transmission electron microscope (in situ TEM), the growth mechanism of silicide NW heterostructures and the diffusion behaviors of transition metals were systematically studied. Spherical aberration corrected scanning transmission electron microscope (Cs-corrected STEM) equipped with energy dispersive spectroscopy (EDS) was used to analyze the phase structure and composition of silicide NW heterostructures. Moreover, electrical and photon sensing properties for the silicide nanowire heterostructures demonstrated promising applications in nano-optoeletronic devices. We found that Ni, Pt, and Si ternary phase nanowire heterostructures have an excellent infrared light sensing property which is absent in bulk Ni2Si or Pt2Si. The above results would benefit the further understanding of heterostructured nano materials.

Preparation and effect of thermal treatment on Gd2O3:SiO2 nanocomposite

NASA Astrophysics Data System (ADS)

Ahlawat, Rachna

2015-04-01

Rare earth oxides have been extensively investigated due to their fascinating properties such as enhanced luminescence efficiency, lower lasing threshold, high-performance luminescent devices, drug-carrying vehicle, contrast agent in magnetic resonance imaging (MRI), up-conversion materials, catalysts and time-resolved fluorescence (TRF) labels for biological detection etc. Nanocomposites of silica gadolinium oxide have been successfully synthesized by sol-gel process using hydrochloric acid as a catalyst. Gd(NO3)3ṡ6H2O and tetraethyl orthosilicate (TEOS) were used as precursors to obtain powdered form of gadolinum oxide:silica (Gd2O3:SiO2) composite. The powdered samples having 2.8 mol% Gd2O3 were annealed at 500°C and 900°C temperature for 6 h and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The effect of annealing on the phase evolution of the composite system has been discussed in detail. It was found that the sintering of gadolinium precursor plays a pivotal role to obtain crystalline phase of Gd2O3. Cubic phase of gadolinium oxide was developed for annealed sample at 900°C (6 h) with an average grain size 12 nm.

Mott-to-Goodenough insulator-insulator transition in LiVO2

NASA Astrophysics Data System (ADS)

Subedi, Alaska

2017-06-01

I critically examine Goodenough's explanation for the experimentally observed phase transition in LiVO2 using microscopic calculations based on density functional and dynamical mean field theories. The high-temperature rhombohedral phase exhibits both magnetic and dynamical instabilities. Allowing a magnetic solution for the rhombohedral structure does not open an insulating gap, and an explicit treatment of the on-site Coulomb U interaction is needed to stabilize an insulating rhombohedral phase. The non-spin-polarized phonon dispersions of the rhombohedral phase show two unstable phonon modes at the wave vector (1/3 ,-1/3 ,0 ) that corresponds to the experimentally observed trimer forming instability. A full relaxation of the supercell corresponding to this instability yields a nonmagnetic state containing V3 trimers. These results are consistent with Goodenough's suggestion that the high-temperature phase is in the localized-electron regime and the transition to the low-temperature phase in the itinerant-electron regime is driven by V-V covalency.

Large area fabrication of plasmonic nanoparticle grating structure by conventional scanning electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudheer,, E-mail: sudheer@rrcat.gov.in; Tiwari, P.; Rai, V. N.

Plasmonic nanoparticle grating (PNG) structure of different periods has been fabricated by electron beam lithography using silver halide based transmission electron microscope film as a substrate. Conventional scanning electron microscope is used as a fabrication tool for electron beam lithography. Optical microscope and energy dispersive spectroscopy (EDS) have been used for its morphological and elemental characterization. Optical characterization is performed by UV-Vis absorption spectroscopic technique.

Mean-field theory for multipole ordering in f-electron systems on the basis of a j-j coupling scheme

NASA Astrophysics Data System (ADS)

Yamamura, Ryosuke; Hotta, Takashi

2018-05-01

We develop a microscopic theory for multipole ordering, applicable to the system with plural numbers of f electrons per ion, from an itinerant picture on the basis of a j-j coupling scheme. For the purpose, by introducing the Γ8 Hubbard Hamiltonian as the minimum model to discuss the multipole ordering in f-electron systems, we describe the mean-field approximation in terms of the multipole operators. For the case of n = 2 , where n denotes the average f-electron number per ion, we analyze the model on a simple cubic lattice to obtain the multipole phase diagram. In particular, we find the order of non-Kramers Γ3 quadrupoles, O20 and O22 , with different ordering vectors. We attempt to explain the phase diagram from the discussion on the interaction energy.

Generation of a spin-polarized electron beam by multipole magnetic fields.

PubMed

Karimi, Ebrahim; Grillo, Vincenzo; Boyd, Robert W; Santamato, Enrico

2014-03-01

The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin-magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of this analysis could prove useful in the design of an improved electron microscope. Copyright © 2013 Elsevier B.V. All rights reserved.

Controlled electron doping into metallic atomic wires: Si(111)4×1-In

NASA Astrophysics Data System (ADS)

Morikawa, Harumo; Hwang, C. C.; Yeom, Han Woong

2010-02-01

We demonstrate the controllable electron doping into metallic atomic wires, indium wires self-assembled on the Si(111) surface, which feature one-dimensional (1D) band structure and temperature-driven metal-insulator transition. The electron filling of 1D metallic bands is systematically increased by alkali-metal adsorption, which, in turn, tunes the macroscopic property, that is, suppresses the metal-insulator transition. On the other hand, the dopant atoms induce a local lattice distortion without a band-gap opening, leading to a microscopic phase separation on the surface. The distinct bifunctional, electronic and structural, roles of dopants in different length scales are thus disclosed.

Dynamic evolutions of electron properties: A theoretical study for condensed-phase β-HMX under shock loading

NASA Astrophysics Data System (ADS)

He, Zheng-Hua; Chen, Jun; Wu, Qiang; Ji, Guang-Fu

2017-11-01

We present the density functional theory (DFT) calculations for microscopic electron properties of β-HMX under shock loading. The metallization pressure is determined to be within 30-55 GPa. The frontier molecular orbitals mainly localize on N-NO2 groups initially and disperse with pressure increase, while HOMO and LUMO orbitals trend to aggregate with each other. The deformation of N-NO2 groups and enhanced hydrogen-bonding interactions cause the electron delocalization and lower the band gap, inducing the reaction initiation finally. Our results show that using the electron properties can reliably predict the initial decomposition of energetic materials under shock loading.

Morphological and quantitative changes in mitochondria, plastids, and peroxisomes during the log-to-stationary transition of the growth phase in cultured tobacco BY-2 cells.

PubMed

Toyooka, Kiminori; Sato, Mayuko; Wakazaki, Mayumi; Matsuoka, Ken

2016-01-01

We developed a wide-range and high-resolution transmission electron microscope acquisition system and obtained giga-pixel images of tobacco BY-2 cells during the log and stationary phases of cell growth. We demonstrated that the distribution and ultrastructure of compartments involved in membrane traffic (i.e., Golgi apparatus, multivesicular body, and vesicle cluster) change during the log-to-stationary transition. Mitochondria, peroxisomes, and plastids were also enumerated. Electron densities of mitochondria and peroxisomes were altered during the growth-phase shift, while their numbers were reduced by nearly half. Plastid structure dramatically changed from atypical to spherical with starch granules. Nearly the same number of plastids was observed in both log and stationary phases. These results indicate that mechanisms regulating organelle populations differ from organelle to organelle.

Combined reflection and transmission microscope for telemedicine applications in field settings.

PubMed

Biener, Gabriel; Greenbaum, Alon; Isikman, Serhan O; Lee, Kelvin; Tseng, Derek; Ozcan, Aydogan

2011-08-21

We demonstrate a field-portable upright and inverted microscope that can image specimens in both reflection and transmission modes. This compact and cost-effective dual-mode microscope weighs only ∼135 grams (<4.8 ounces) and utilizes a simple light emitting diode (LED) to illuminate the sample of interest using a beam-splitter cube that is positioned above the object plane. This LED illumination is then partially reflected from the sample to be collected by two lenses, creating a reflection image of the specimen onto an opto-electronic sensor-array that is positioned above the beam-splitter cube. In addition to this, the illumination beam is also partially transmitted through the same specimen, which then casts lensfree in-line holograms of the same objects onto a second opto-electronic sensor-array that is positioned underneath the beam-splitter cube. By rapid digital reconstruction of the acquired lensfree holograms, transmission images (both phase and amplitude) of the same specimen are also created. We tested the performance of this field-portable microscope by imaging various micro-particles, blood smears as well as a histopathology slide corresponding to skin tissue. Being compact, light-weight and cost-effective, this combined reflection and transmission microscope might especially be useful for telemedicine applications in resource limited settings. This journal is © The Royal Society of Chemistry 2011

The qualitative f-ratio method applied to electron channelling-induced x-ray imaging with an annular silicon drift detector in a scanning electron microscope in the transmission mode.

PubMed

Brodusch, Nicolas; Gauvin, Raynald

2017-09-01

Electron channelling is known to affect the x-ray production when an accelerated electron beam is applied to a crystalline material and is highly dependent on the local crystal orientation. This effect, unless very long counting time are used, is barely noticeable on x-ray energy spectra recorded with conventional silicon drift detectors (SDD) located at a small elevation angle. However, the very high count rates provided by the new commercially available annular SDDs permit now to observe this effect routinely and may, in some circumstances, hide the true elemental x-ray variations due to the local true specimen composition. To circumvent this issue, the recently developed f-ratio method was applied to display qualitatively the true net intensity x-ray variations in a thin specimen of a Ti-6Al-4V alloy in a scanning electron microscope in transmission mode. The diffraction contrast observed in the x-ray images was successfully cancelled through the use of f-ratios and the true composition variations at the grain boundaries could be observed in relation to the dislocation alignment prior to the β-phase nucleation. The qualitative effectiveness in removing channelling effects demonstrated in this work makes the f-ratio, in its quantitative form, a possible alternative to the ZAF method in channelling conditions. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Densely packed beta-structure at the protein-lipid interface of porin is revealed by high-resolution cryo-electron microscopy.

PubMed

Sass, H J; Büldt, G; Beckmann, E; Zemlin, F; van Heel, M; Zeitler, E; Rosenbusch, J P; Dorset, D L; Massalski, A

1989-09-05

Porin is an integral membrane protein that forms channels across the outer membrane of Escherichia coli. Electron microscopic studies of negatively stained two-dimensional porin crystals have shown three stain accumulations per porin trimer, revealing the locations of pores spanning the membrane. In this study, reconstituted porin lattices embedded in glucose were investigated using the low-dose technique on a cryo-electron microscope equipped with a helium-cooled superconducting objective lens. The specimen temperature was maintained at 5 K to yield an improved microscopic and specimen stability. Under these conditions, we obtained for the first time electron diffraction patterns from porin lattices to a resolution of 3.2 A and images showing optical diffraction up to a resolution of 4.9 A. Applying correlation averaging techniques to the digitized micrographs, we were able to reconstruct projected images of the porin trimer to a resolution of up to 3.5 A. In the final projection maps, amplitudes from electron diffraction and phases from these images were combined. The predominant feature is a high-density narrow band (about 6 A in thickness) that delineates the outer perimeter of the trimer. Since the molecule consists of almost exclusively beta-sheet structure, as revealed by spectroscopic data, we conclude that this band is a cylindrical beta-pleated sheet crossing the membrane nearly perpendicularly to its plane. Another intriguing finding is a low-density area (about 70 A2) situated in the centre of the trimer.

Electric field controlled spin interference in a system with Rashba spin-orbit coupling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciftja, Orion, E-mail: ogciftja@pvamu.edu

There have been intense research efforts over the last years focused on understanding the Rashba spin-orbit coupling effect from the perspective of possible spintronics applications. An important component of this line of research is aimed at control and manipulation of electron’s spin degrees of freedom in semiconductor quantum dot devices. A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction in a two-dimensional electron system embedded in a host semiconducting material that lacks inversion-symmetry. This way, the Rashba spin-orbit coupling effect may potentially lead to fabrication of amore » new generation of spintronic devices where control of spin, thus magnetic properties, is achieved via an electric field and not a magnetic field. In this work we investigate theoretically the electron’s spin interference and accumulation process in a Rashba spin-orbit coupled system consisting of a pair of two-dimensional semiconductor quantum dots connected to each other via two conducting semi-circular channels. The strength of the confinement energy on the quantum dots is tuned by gate potentials that allow “leakage” of electrons from one dot to another. While going through the conducting channels, the electrons are spin-orbit coupled to a microscopically generated electric field applied perpendicular to the two-dimensional system. We show that interference of spin wave functions of electrons travelling through the two channels gives rise to interference/conductance patterns that lead to the observation of the geometric Berry’s phase. Achieving a predictable and measurable observation of Berry’s phase allows one to control the spin dynamics of the electrons. It is demonstrated that this system allows use of a microscopically generated electric field to control Berry’s phase, thus, enables one to tune the spin-dependent interference pattern and spintronic properties with no need for injection of spin-polarized electrons.« less

Interdiffusion behavior of U3Si2 with FeCrAl via diffusion couple studies

NASA Astrophysics Data System (ADS)

Hoggan, Rita E.; He, Lingfeng; Harp, Jason M.

2018-04-01

Uranium silicide (U3Si2) is a candidate to replace uranium oxide (UO2) as light water reactor (LWR) fuel because of its higher thermal conductivity and higher fissile density relative to the current standard, UO2. A class of Fe, Cr, Al alloys collectively known as FeCrAl alloys that have superior mechanical and oxidation resistance are being considered as an alternative to the standard Zirconium based LWR cladding. The interdiffusion behavior between FeCrAl and U3Si2 is investigated in this study. Commercially available FeCrAl, along with U3Si2 pellets were placed in diffusion couples. Individual tests were ran at temperatures ranging from 500 °C to 1000 °C for 30 h and 100 h. The interdiffusion was analyzed with an optical microscope, scanning electron microscope, and transmission electron microscope. Uniform and planar interdiffusion layers along the material interface were illustrated with backscatter electron micrographs and energy-dispersive X-ray spectroscopy. Electron diffraction was used to validate phases present in the system, including distinct U2Fe3Si/UFe2 and UFeSi layers at the material interface. U and Fe diffused far into the FeCrAl and U3Si2 matrix, respectively, in the higher temperature tests. No interaction was observed at 500 °C for 30 h.

About the contrast of δ' precipitates in bulk Al-Cu-Li alloys in reflection mode with a field-emission scanning electron microscope at low accelerating voltage.

PubMed

Brodusch, Nicolas; Voisard, Frédéric; Gauvin, Raynald

2017-11-01

Characterising the impact of lithium additions in the precipitation sequence in Al-Li-Cu alloys is important to control the strengthening of the final material. Since now, transmission electron microscopy (TEM) at high beam voltage has been the technique of choice to monitor the size and spatial distribution of δ' precipitates (Al 3 Li). Here we report on the imaging of the δ' phase in such alloys using backscattered electrons (BSE) and low accelerating voltage in a high-resolution field-emission scanning electron microscope. By applying low-energy Ar + ion milling to the surface after mechanical polishing (MP), the MP-induced corroded layers were efficiently removed and permitted the δ's to be visible with a limited impact on the observed microstructure. The resulting BSE contrast between the δ's and the Al matrix was compared with that obtained using Monte Carlo modelling. The artefacts possibly resulting from the sample preparation procedure were reviewed and discussed and permitted to confirm that these precipitates were effectively the metastable δ's. The method described in this report necessitates less intensive sample preparation than that required for TEM and provides a much larger field of view and an easily interpretable contrast compared to the transmission techniques. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

The Scanning Optical Microscope: An Overview

NASA Astrophysics Data System (ADS)

Kino, G. S.; Corte, T. R.; Xiao, G. Q.

1988-07-01

In the last few years there has been a resurgence in research on optical microscopes. One reason stems from the invention of the acoustic microscope by Quate and Lemons,1 and the realization that some of the same principles could be applied to the optical microscope. The acoustic microscope has better transverse definition for the same wavelength than the standard optical microscope and at the same time has far better range definition. Consequently, Kompfner, who was involved with the work on the early acoustic microscope, decided to try out similar scanning microscope principles with optics, and started a group with Wilson and Sheppard to carry out such research at Oxford.2 Sometime earlier, Petran et a13 had invented the tandem scanning microscope which used many of the same principles. Now, in our laboratory at Stanford, these ideas on the tandem scanning microscope and the scanning optical microscope are converging. Another aspect of this work, which stems from the earlier experience with the acoustic microscope, involves measurement of both phase and amplitude of the optical beam. It is also possible to use scanned optical microscopy for other purposes. For instance, an optical beam can be used to excite electrons and holes in semiconductors, and the generated current can be measured. By scanning the optical beam over the semiconductor, an image can be obtained of the regions where there is strong or weak electron hole generation. This type of microscope is called OBIC (Optical Beam Induced Current). A second application involves fluorescent imaging of biological materials. Here we have the excellent range definition of a scanning optical microscope which eliminates unwanted glare from regions of the material where the beam is unfocused.3 A third application is focused on the heating effect of the light beam. With such a system, images can be obtained which are associated with changes in the thermal properties of a material, changes in recombination rates in semiconductors, and differences in material properties associated with either acoustic or thermal effects.4,5 Thus, the range of scanning optical microscopy applications is very large. In the main, the most important applications have been to semiconductors and to biology.

Phase measurement error in summation of electron holography series.

PubMed

McLeod, Robert A; Bergen, Michael; Malac, Marek

2014-06-01

Off-axis electron holography is a method for the transmission electron microscope (TEM) that measures the electric and magnetic properties of a specimen. The electrostatic and magnetic potentials modulate the electron wavefront phase. The error in measurement of the phase therefore determines the smallest observable changes in electric and magnetic properties. Here we explore the summation of a hologram series to reduce the phase error and thereby improve the sensitivity of electron holography. Summation of hologram series requires independent registration and correction of image drift and phase wavefront drift, the consequences of which are discussed. Optimization of the electro-optical configuration of the TEM for the double biprism configuration is examined. An analytical model of image and phase drift, composed of a combination of linear drift and Brownian random-walk, is derived and experimentally verified. The accuracy of image registration via cross-correlation and phase registration is characterized by simulated hologram series. The model of series summation errors allows the optimization of phase error as a function of exposure time and fringe carrier frequency for a target spatial resolution. An experimental example of hologram series summation is provided on WS2 fullerenes. A metric is provided to measure the object phase error from experimental results and compared to analytical predictions. The ultimate experimental object root-mean-square phase error is 0.006 rad (2π/1050) at a spatial resolution less than 0.615 nm and a total exposure time of 900 s. The ultimate phase error in vacuum adjacent to the specimen is 0.0037 rad (2π/1700). The analytical prediction of phase error differs with the experimental metrics by +7% inside the object and -5% in the vacuum, indicating that the model can provide reliable quantitative predictions. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooke, Gary A.; Pestovich, John A.; Huber, Heinz J.

This report presents the results for solid phase characterization (SPC) of solid samples removed from tank 241-C-108 (C-108) on August 12-13,2012, using the off-riser sampler. Samples were received at the 222-S Laboratory on August 13 and were described and photographed. The SPC analyses that were performed include scanning electron microscopy (SEM) using the ASPEX(R)l scanning electron microscope, X-ray diffraction (XRD) using the Rigaku(R) 2 MiniFlex X-ray diffractometer, and polarized light microscopy (PLM) using the Nikon(R) 3 Eclipse Pol optical microscope. The SEM is equipped with an energy dispersive X-ray spectrometer (EDS) to provide chemical information. Gary A. Cooke conducted themore » SEM analysis, John A. Pestovich performed the XRD analysis, and Dr. Heinz J. Huber performed the PLM examination. The results of these analyses are presented here.« less

A New Technique to Produce Clean and Thin Silicon Films In Situ in a UHV Electron Microscope for TEM-TED Studies of Surfaces

NASA Astrophysics Data System (ADS)

Ozawa, Soh-ichiro; Yamanaka, Akira; Kobayashi, Kunio; Tanishiro, Yasumasa; Yagi, Katsumichi

1990-04-01

A new technique of in situ oxygen gas reaction thinning of Si films at around 750-800°C in an ultrahigh-vacuum electron microscope was developed. The technique produced films as thin as 10 to 20 nm. Such a thin film allows us to observe surface atomic steps, out-of-phase boundaries and {1/7 0}, {1/7 1/7} and {2/7 0} spots from the Si(111)7× 7 surface. These spots were not observed in previous studies, having been masked by strong inelastic scattering. The technique is useful not only for detecting clear diffraction spots of kinematical intensity for surface structure analysis but also for observation of high-resolution plan-view structure images of clean and adsorbed surfaces.

Transmission electron microscope CCD camera

DOEpatents

Downing, Kenneth H.

1999-01-01

In order to improve the performance of a CCD camera on a high voltage electron microscope, an electron decelerator is inserted between the microscope column and the CCD. This arrangement optimizes the interaction of the electron beam with the scintillator of the CCD camera while retaining optimization of the microscope optics and of the interaction of the beam with the specimen. Changing the electron beam energy between the specimen and camera allows both to be optimized.

The grape cluster, metal particle 63344,1. [in lunar coarse fines

NASA Technical Reports Server (NTRS)

Goldstein, J. I.; Axon, H. J.; Agrell, S. O.

1975-01-01

The grape cluster metal particle 63344,1 found in lunar coarse fines is examined using the scanning electron microscope (SEM), electron microprobe, and an optical microscope. This metal particle is approximately 0.5 cm in its largest dimension and consists of hundreds of metallic globules welded together to form a structure somewhat like a bunch of grapes. Electron microprobe analysis for Fe, Ni, Co, P, and S in the metal was carried out using wavelength dispersive detectors. No primary solidification structure is observed in the globules, and the particle is slow cooled from the solidification temperature (nearly 1300 C) taking days to probably months to reach 600 C. Two mechanisms for the formation of globules are proposed. One mechanism involves the primary impact of an iron meteorite which produces a metallic liquid and vapor phase. The second mechanism involves the formation of a liquid pool of metal after impact of an iron meteorite projectile followed by a secondary impact in the liquid metal pool.

Improper magnetic ferroelectricity of nearly pure electronic nature in helicoidal spiral CaMn7O12

NASA Astrophysics Data System (ADS)

Lim, Jin Soo; Saldana-Greco, Diomedes; Rappe, Andrew M.

2018-01-01

Helicoidal magnetic order breaks inversion symmetry in quadruple perovskite CaMn7O12 , generating one of the largest spin-induced ferroelectric polarizations measured to date. Here, the microscopic origin of the polarization, including exchange interactions, coupling to the spin helicity, and charge density redistribution, is explored via first-principles calculations. The B -site Mn4 + (Mn3) spin adopts a noncentrosymmetric configuration, stabilized not only by spin-orbit coupling (SOC), but also by the fully anisotropic Hubbard J parameter in the absence of SOC, to break inversion symmetry and generate polarization. Berry phase computed polarization (Pelec=2169 μ C /m2 ) exhibits nearly pure electronic behavior, with negligible Mn displacements (≈0.7 m Å ). Orbital-resolved density of states shows that p -d orbital mixing is microscopically driven by nonrelativistic exchange striction within the commensurate ionic structure. Persistent electronic polarization induced by helical spin order in the nearly inversion-symmetric ionic crystal lattice suggests opportunities for ultrafast magnetoelectric response.

Effect of micromorphology at the fatigue crack tip on the crack growth in electron beam welded Ti-6Al-4V joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Junhui; Hu, Shubing, E-mail: 187352581@qq.com

In this paper, we describe experiments on welded joints of Ti-6Al-4V alloy specimens exhibiting fatigue characteristics in the base metal (BM), hot affected zone (HAZ) and fuse zone (FZ). The effect of micromorphology on crack propagation at the tip of the fatigue crack in joints formed by electron beam welding was investigated using an optical microscope, transmission electron microscope and other methodologies. The results demonstrated that the fatigue crack originated in and propagated along α/β boundaries in the BM. In the HAZ, the fatigue crack occurred at the boundary between martensite laths, and propagated through most irregular-equiaxed α phases andmore » a few martensite laths. In the FZ, the fatigue crack originated at the boundaries between the fine crushing phases among martensite laths, and propagated along a majority of α/β boundaries and several narrow martensite laths. The electron beam welded joint of Ti-6Al-4V alloy showed instances of zigzag fatigue cracks that increased in degree from lowest in the HAZ, moderate in the FZ to greatest in the BM. Conversely, fatigue crack growth rate (FCGR) was greatest in the HAZ, less in the FZ and slowest in the BM. - Highlights: •Ti-6Al-4V welded joint exhibits different fatigue characteristics. •The fatigue crack propagates along α/β boundaries in the BM. •The fatigue crack propagates through α phases and martensite laths in the HAZ. •The fatigue crack propagates along α/β boundaries and martensite laths in the FZ. •Fatigue crack growth rate is fastest in the HAZ, less in the FZ, slowest in the BM.« less

Three-dimensional study of the vector potential of magnetic structures.

PubMed

Phatak, Charudatta; Petford-Long, Amanda K; De Graef, Marc

2010-06-25

The vector potential is central to a number of areas of condensed matter physics, such as superconductivity and magnetism. We have used a combination of electron wave phase reconstruction and electron tomographic reconstruction to experimentally measure and visualize the three-dimensional vector potential in and around a magnetic Permalloy structure. The method can probe the vector potential of the patterned structures with a resolution of about 13 nm. A transmission electron microscope operated in the Lorentz mode is used to record four tomographic tilt series. Measurements for a square Permalloy structure with an internal closure domain configuration are presented.

Imaging domain walls between nematic quantum Hall phases on the surface of bismuth

NASA Astrophysics Data System (ADS)

Ding, Hao; Randeria, Mallika T.; Feldman, Benjamin E.; Ji, Huiwen; Cava, Robert J.; Yazdani, Ali

The sensitivity of nematic electronic phases to disorder results in short range ordering and the formation of domains. Local probes are required to investigate the character of these domains and the boundaries between them, which remain hidden in global measurements that average over microscopic configurations. In this talk, I will describe measurements performed with a scanning tunneling microscope to study local nematic order on the surface of bismuth at high magnetic field. By imaging individual anisotropic cyclotron orbit wavefunctions that are pinned to atomic-scale surface defects, we directly resolve local nematic behavior and study the evolution of nematic states across a domain wall. Through spectroscopic mapping, we explore how the broken-symmetry Landau levels disperse across the domain wall, the influence of exchange interactions at such a boundary, and the formation of one-dimensional edge states.

Tropical sea snail shells: Possible exotic sources for ceramic biomaterial synthesis

NASA Astrophysics Data System (ADS)

Oktar, F. N.; Kiyici, I. A.; Gökçe, H.; Aǧaogulları, D.; Kayali, E. S.

2013-12-01

In this study, chemical and structural properties of sea snail shell based bioceramic materials (i.e. hydroxyapatite, whitlockite and other phases) are produced by using mechano-chemical (ultrasonic) conversion method. For this purpose, differential thermal and gravimetric analysis (DTA/TG), X-ray diffraction, infra-red (IR) and scanning electron microscope (SEM) studies are performed.

76 FR 65696 - Battelle Energy Alliance, et al.;

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... of Texas at Austin, Austin, TX 78712. Instrument: Electron Microscope. Manufacturer: FEI Company, the... research or scientific educational uses requiring an electron microscope. We know of no electron microscope...

Effect of growth phase on harvesting characteristics, autoflocculation and lipid content of Ettlia texensis for microalgal biodiesel production.

PubMed

Salim, S; Shi, Z; Vermuë, M H; Wijffels, R H

2013-06-01

The effect of growth phase on the recovery of the autoflocculating microalgae Ettlia texensis was studied. In the stationary phase, 90% recovery was achieved after 3h settling. Scanning electron microscopic pictures revealed that extracellular polymeric substances (EPS) on the cell surface were involved in autoflocculation. During the stationary phase an increase of the protein fraction in the EPS was observed while the total fatty acids content increased. The autoflocculating properties of E. texensis combined with favourite fatty acid content and composition make this microalgae an excellent candidate for biodiesel production if harvested at the end of the stationary phase. Copyright © 2013 Elsevier Ltd. All rights reserved.

Determination of the structural phase and octahedral rotation angle in halide perovskites

NASA Astrophysics Data System (ADS)

dos Reis, Roberto; Yang, Hao; Ophus, Colin; Ercius, Peter; Bizarri, Gregory; Perrodin, Didier; Shalapska, Tetiana; Bourret, Edith; Ciston, Jim; Dahmen, Ulrich

2018-02-01

A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurement of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and comparison with simulations yield an octahedral rotation angle of 6.5°(±1.5°). The approach demonstrated here opens up opportunities for understanding the atomic scale structural phenomena applying advanced characterization tools on a wide range of radiation sensitive halide-based all-inorganic and hybrid organic-inorganic perovskites.

Microscopic observations of self-healing products in calcareous fly ash mortars.

PubMed

Jóźwiak-Niedźwiedzka, Daria

2015-01-01

The results of microstructural characterization of mortars containing fly ash class C (High Calcium Fly Ash) from combustion of lignite are presented. The evaluation of the microstructure was performed using scanning electron microscope, optical, and confocal microscope. The tested beams were bent till the crack and microcracks opening, which were healed during the different curing time. The results showed that the replacement of cement with fly ash class C influenced the process of crack healing. The addition of HCFA, at both 30% and 60%, speeds up the self-healing process in cracks and particularly in micro-cracks. In the research, the completely filling up of the cracks by new phases has not been observed, only the beginning of such process has been noticed. © 2014 Wiley Periodicals, Inc.

In Situ Observation of Kinetic Processes of Lath Bainite Nucleation and Growth by Laser Scanning Confocal Microscope in Reheated Weld Metals

NASA Astrophysics Data System (ADS)

Mao, Gaojun; Cao, Rui; Guo, Xili; Jiang, Yong; Chen, Jianhong

2017-12-01

The kinetic processes of nucleation and growth of bainite laths in reheated weld metals are observed and analyzed by a combination of a laser confocal scanning microscope and an electron backscattering diffraction with a field emission scanning electron microscope. The results indicate that the surface relief induced by phase transformation is able to reveal the real microstructural morphologies of bainite laths when viewed from various angles. Five nucleation modes and six types of growth behaviors of bainite laths are revealed. The bainite lath growth rates are measured to vary over a wide range, from 2 μm/s to higher than 2000 μm/s. The orientations of the bainite laths within a prior austenite grain are examined and denoted as different variants. On the basis of variant identification, the reason is analyzed for various growth rates which are demonstrated to be affected by (1) the density of the high-angle misorientation in it, (2) the included angle between habit planes of different variants, and (3) the direction of lath growth with respect to the free (polished) surface.

Microstructural Study of 17-4PH Stainless Steel after Plasma-Transferred Arc Welding

PubMed Central

Deng, Dewei; Chen, Rui; Sun, Qi; Li, Xiaona

2015-01-01

The improvement of the surface qualities and surface hardening of precipitation hardened martensitic stainless steel 17-4PH was achieved by the plasma-transferred arc welding (PTAW) process deposited with Co-based alloy. The microstructure of the heat affected zone (HAZ) and base metal were characterized by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that there are obvious microstructural differences between the base metal and HAZ. For example, base material is transformed from lath martensite to austenite due to the heateffect of the welding process. On the other hand, the precipitate in the matrix (bar-like shape Cr7C3 phase with a width of about one hundred nanometres and a length of hundreds of nanometres) grows to a rectangular appearance with a width of about two hundred nanometres and a length of about one micron. Stacking fault could also be observed in the Cr7C3 after PTAW. The above means that welding can obviously improve the surface qualities. PMID:28787947

Effect of Cooling Rate on Microstructure of Two Kinds of High Nb Containing Tial Alloys

NASA Astrophysics Data System (ADS)

Chai, L. H.; Feng, Z. Y.; Xiang, Z. L.; Cui, Y. S.; Zhou, F.; Chen, Z. Y.

2017-09-01

In this paper, high Nb-TiAl alloys with Cr and W additions were prepared by Vacuum induction melting method, and then were heat treated under three different cooling rates of slow cooling, furnace cooling and air cooling. The phase composition of the alloy was analyzed by X ray diffraction, and the microstructure of the alloy was observed by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive analyzer. The results show that the microstructure of Ti45Al8Nb0.2Cr and Ti45Al8Nb0.2W are fully lamellar structure with the main phase composition of α+γ after 3 different heat treatment conditions. The grain size of the two alloys decreases with decreasing of cooling rate, and the grain size of the alloyed with Cr alloy is smaller than that of the alloyed with W alloy. Most of the original massive β phase at grain boundaries and lamellar interfaces dissolved after heat treatment, and the transformation of β phase is easier for Ti45Al8Nb0.2Cr.

[Biomimetic nanohydroxyapatite/gelatin composite material preparation and in vitro study].

PubMed

Li, Siriguleng; Hu, Xiaowen

2014-09-01

To prepare nHA/gelatin porous scaffold and to evaluate its physical and chemical properties and biocompatibility. We used nano-powders of HA and gelatin to prepare 3D porous composite scaffold by freeze-drying technique, and used scanning electron microscope, fourier transform infrared spectroscopy and universal testing machine to characterize the composite material. Osteoblasts were primarily cultured, and the third-passage osteoblasts were co-cultured with the composite material. The cell adhesion and morphology were examined under scanning electron microscope. The cell viability analysis was performed by MTT assay, and the alkaline phosphatase activity was measured with alkaline phosphatase kit. Scanning electron microscope showed that the scaffold possessed a 3-dimensional interconnected homogenous porous structure with pore sizes ranging from 150 to 400 μm. Fourier transform infrared spectroscopy showed that the composite material had a strong chemical bond between the inorganic phase and organic phase. The scaffold presented the compressive strength of (3.28 ± 0.51) MPa and porosities of (80.6 ± 4.1)%. Composite materials showed features of had good biocompatibility. Mouse osteoblasts were well adhered and spread on the materials. The grade of the cell toxicity ranged from I to II. On the 5th and 7th day the proliferative rate of osteoblasts on scaffolds in the composite materials was significantly higher than that in the control group. The activity of alkaline phosphatase was obviously higher than that in the control group on Day 1 and 3. Nano-hydroxyapatite and gelatin in certain proportions and under certain conditions can be prepared into a composite biomimetic porous scaffolds with high porosity and three-dimensional structure using freeze-drying method. The scaffold shows good biocompatibility with mouse osteoblasts and may be a novel scaffolds for bone tissue engineering.

Detection of magnetic circular dichroism in amorphous materials utilizing a single-crystalline overlayer

DOE PAGES

Lin, J.; Zhong, X. Y.; Song, C.; ...

2017-12-27

Physicists are fascinated with topological defects in solid-state materials, because by breaking the translational symmetry they offer emerging properties that are not present in their parental phases. For example, edge dislocations—the 2π phase-winding topological defects—in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. Herein, we study how these defects could give rise to exotic topological orders when they interact with a high energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, wemore » found the amplitude patterns of the <020> Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. This approach provides a new perspective for boosting the collection efficiency of magnetic circular dichroism spectra with high spatial resolution and understanding the relationship between symmetry breaking and exotic property of individual topological defect at atomic level.« less

Detection of magnetic circular dichroism in amorphous materials utilizing a single-crystalline overlayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, J.; Zhong, X. Y.; Song, C.

Physicists are fascinated with topological defects in solid-state materials, because by breaking the translational symmetry they offer emerging properties that are not present in their parental phases. For example, edge dislocations—the 2π phase-winding topological defects—in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. Herein, we study how these defects could give rise to exotic topological orders when they interact with a high energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, wemore » found the amplitude patterns of the <020> Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. This approach provides a new perspective for boosting the collection efficiency of magnetic circular dichroism spectra with high spatial resolution and understanding the relationship between symmetry breaking and exotic property of individual topological defect at atomic level.« less

Distinction between amorphous and healed planar deformation features in shocked quartz using composite color scanning electron microscope cathodoluminescence (SEM-CL) imaging

NASA Astrophysics Data System (ADS)

Hamers, Maartje F.; Pennock, Gill M.; Herwegh, Marco; Drury, Martyn R.

2016-10-01

Planar deformation features (PDFs) in quartz are one of the most reliable and most widely used forms of evidence for hypervelocity impact. PDFs can be identified in scanning electron microscope cathodoluminescence (SEM-CL) images, but not all PDFs show the same CL behavior: there are nonluminescent and red luminescent PDFs. This study aims to explain the origin of the different CL emissions in PDFs. Focused ion beam (FIB) thin foils were prepared of specific sample locations selected in composite color SEM-CL images and were analyzed in a transmission electron microscope (TEM). The FIB preparation technique allowed a direct, often one-to-one correlation between the CL images and the defect structure observed in TEM. This correlation shows that composite color SEM-CL imaging allows distinction between amorphous PDFs on one hand and healed PDFs and basal Brazil twins on the other: nonluminescent PDFs are amorphous, while healed PDFs and basal Brazil twins are red luminescent, with a dominant emission peak at 650 nm. We suggest that the red luminescence is the result of preferential beam damage along dislocations, fluid inclusions, and twin boundaries. Furthermore, a high-pressure phase (possibly stishovite) in PDFs can be detected in color SEM-CL images by its blue luminescence.

Geometry of phase-separated domains in phospholipid bilayers by diffraction-contrast electron microscopy.

PubMed Central

Hui, S W

1981-01-01

The sizes and shapes of solidus (gel) phase domains in the hydrated molecular bilayers of dilauroylphosphatidylcholine/dipalmitoylphasphatidylcholine (DLPC/DPPC) (1:1) and phosphatidylserine (PS)/DPPC (1:2) are visualized directly by low dose diffraction-contrast electron microscopy. The temperature and humidity of the bilayers are controlled by an environmental chamber set in an electron microscope. The contrast between crystalline domains is enhanced by electron optical filtering of the diffraction patterns of the bilayers. The domains are seen as a patchwork in the plane of the bilayer, with an average width of 0.2-0.5 micrometer. The percentage of solidus area measured from diffraction-contrast micrographs at various temperatures agrees in general with those depicted by known phase diagrams. The shape and size of the domains resemble those seen by freeze-fracture in multilamellar vesicles. Temperature-related changes in domain size and in phase boundary per unit area are more pronounced in the less miscible DLPC/DPPC mixture. No significant change in these geometric parameters with temperature is found in the PS/DPPC mixture. Mapping domains by their molecular diffraction signals not only verifies the existance of areas of different molecular packing during phase separation but also provides a quantitative measurement of structural boundaries and defects in lipid bilayers. Images FIGURE 1 FIGURE 3 FIGURE 6 PMID:6894707

Energy spectra of quantum rings.

PubMed

Fuhrer, A; Lüscher, S; Ihn, T; Heinzel, T; Ensslin, K; Wegscheider, W; Bichler, M

2001-10-25

Quantum mechanical experiments in ring geometries have long fascinated physicists. Open rings connected to leads, for example, allow the observation of the Aharonov-Bohm effect, one of the best examples of quantum mechanical phase coherence. The phase coherence of electrons travelling through a quantum dot embedded in one arm of an open ring has also been demonstrated. The energy spectra of closed rings have only recently been studied by optical spectroscopy. The prediction that they allow persistent current has been explored in various experiments. Here we report magnetotransport experiments on closed rings in the Coulomb blockade regime. Our experiments show that a microscopic understanding of energy levels, so far limited to few-electron quantum dots, can be extended to a many-electron system. A semiclassical interpretation of our results indicates that electron motion in the rings is governed by regular rather than chaotic motion, an unexplored regime in many-electron quantum dots. This opens a way to experiments where even more complex structures can be investigated at a quantum mechanical level.

Four-Dimensional Ultrafast Electron Microscopy: Insights into an Emerging Technique.

PubMed

Adhikari, Aniruddha; Eliason, Jeffrey K; Sun, Jingya; Bose, Riya; Flannigan, David J; Mohammed, Omar F

2017-01-11

Four-dimensional ultrafast electron microscopy (4D-UEM) is a novel analytical technique that aims to fulfill the long-held dream of researchers to investigate materials at extremely short spatial and temporal resolutions by integrating the excellent spatial resolution of electron microscopes with the temporal resolution of ultrafast femtosecond laser-based spectroscopy. The ingenious use of pulsed photoelectrons to probe surfaces and volumes of materials enables time-resolved snapshots of the dynamics to be captured in a way hitherto impossible by other conventional techniques. The flexibility of 4D-UEM lies in the fact that it can be used in both the scanning (S-UEM) and transmission (UEM) modes depending upon the type of electron microscope involved. While UEM can be employed to monitor elementary structural changes and phase transitions in samples using real-space mapping, diffraction, electron energy-loss spectroscopy, and tomography, S-UEM is well suited to map ultrafast dynamical events on materials surfaces in space and time. This review provides an overview of the unique features that distinguish these techniques and also illustrates the applications of both S-UEM and UEM to a multitude of problems relevant to materials science and chemistry.

Nanoscale ferromagnetism in phase-separated manganites

NASA Astrophysics Data System (ADS)

Mori, S.; Horibe, Y.; Asaka, T.; Matsui, Y.; Chen, C. H.; Cheong, S. W.

2007-03-01

Magnetic domain structures in phase-separated manganites were investigated by low-temperature Lorentz electron microscopy, in order to understand some unusual physical properties such as a colossal magnetoresistance (CMR) effect and a metal-to-insulator transition. In particular, we examined a spatial distribution of the charge/orbital-ordered (CO/OO) insulator state and the ferromagnetic (FM) metallic one in phase-separated manganites; Cr-doped Nd0.5Ca0.5MnO3 and ( La1-xPrx)CaMnO3 with x=0.375, by obtaining both the dark-field images and Lorentz electron microscopic ones. It is found that an unusual coexistence of the CO/OO and FM metallic states below a FM transition temperature in the two compounds. The present experimental results clearly demonstrated the coexisting state of the two distinct ground states in manganites.

Anomalous nanoclusters, anisotropy, and electronic nematicity in the doped manganite L a 1 / 3 C a 2 / 3 Mn O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, J.; Sun, K.; Tranquada, J. M.

In doped manganites, a superlattice (SL) modulation associated with charge/orbital ordering is accepted as a key component in understanding many intriguing properties. It has been reported that the SL modulation always appears on the a axis of the crystals. Here in this study, by using multiple transmission electron microscopic techniques, we observe a type of anomalous nanocluster in which the SL modulation appears on the c axis of La 1/3Ca 2/3MnO 3. By correlating the thermal evolution of the anomalous nanoclusters to other property measurements, we suggest that strain is responsible for the formation of the anomalous nanoclusters. The phasemore » separation and phase transition scenario in La 1/3Ca 2/3MnO 3 are also described using electronic-liquid-crystal (ELC) phases. Lastly, an ELC phase diagram in La 1/3Ca 2/3MnO 3 is constructed as a function of temperature based on our observations.« less

Image contrast enhancement of Ni/YSZ anode during the slice-and-view process in FIB-SEM.

PubMed

Liu, Shu-Sheng; Takayama, Akiko; Matsumura, Syo; Koyama, Michihisa

2016-03-01

Focused ion beam-scanning electron microscopy (FIB-SEM) is a widely used and easily operational equipment for three-dimensional reconstruction with flexible analysis volume. It has been using successfully and increasingly in the field of solid oxide fuel cell. However, the phase contrast of the SEM images is indistinct in many cases, which will bring difficulties to the image processing. Herein, the phase contrast of a conventional Ni/yttria stabilized zirconia anode is tuned in an FIB-SEM with In-Lens secondary electron (SE) and backscattered electron detectors. Two accessories, tungsten probe and carbon nozzle, are inserted during the observation. The former has no influence on the contrast. When the carbon nozzle is inserted, best and distinct contrast can be obtained by In-Lens SE detector. This method is novel for contrast enhancement. Phase segmentation of the image can be automatically performed. The related mechanism for different images is discussed. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Anomalous nanoclusters, anisotropy, and electronic nematicity in the doped manganite L a 1 / 3 C a 2 / 3 Mn O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, J.; Sun, K.; Tranquada, J. M.

2017-06-07

In doped manganites, a superlattice (SL) modulation associated with charge/orbital ordering is accepted as a key component in understanding many intriguing properties. It has been reported that the SL modulation always appears on the a axis of the crystals. Here in this study, by using multiple transmission electron microscopic techniques, we observe a type of anomalous nanocluster in which the SL modulation appears on the c axis of La 1/3Ca 2/3MnO 3. By correlating the thermal evolution of the anomalous nanoclusters to other property measurements, we suggest that strain is responsible for the formation of the anomalous nanoclusters. The phasemore » separation and phase transition scenario in La 1/3Ca 2/3MnO 3 are also described using electronic-liquid-crystal (ELC) phases. Lastly, an ELC phase diagram in La 1/3Ca 2/3MnO 3 is constructed as a function of temperature based on our observations.« less

Correlated Electrons in Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Odintsov, Arkadi A.; Yoshioka, Hideo

Single-wall carbon nanotubes are almost ideal systems for the investigation of exotic many-body effects due to non-Fermi liquid behavior of interacting electrons in one dimension. Recent theoretical and experimental results are reviewed with a focus on electron correlations. Starting from a microscopic lattice model we derive an effective phase Hamiltonian for conducting single-wall nanotubes with arbitrary chirality. The parameters of the Hamiltonian show very weak dependence on the chiral angle, which makes the low-energy physics of conducting nanotubes universal. The temperature-dependent resistivity and frequency-dependent optical conductivity of nanotubes with impurities are evaluated within the Luttinger-like model. Localization effects are studied. In particular, we found that intra-valley and inter-valley electron scattering can not coexist at low energies. Low-energy properties of clean nanotubes are studied beyond the Luttinger liquid approximation. The strongest Mott-like electron instability occurs at half filling. In the Mott insulating phase electrons at different atomic sublattices form characteristic bound states. The energy gaps occur in all modes of elementary excitations and estimate at 0.01-0.1 eV. We finally discuss observability of the Mott insulating phase in transport experiments. The accent is made on the charge transfer from external electrodes which results in a deviation of the electron density from half-filling.

Investigation of C3 S hydration mechanism by transmission electron microscope (TEM) with integrated Super-XTM EDS system.

PubMed

Sakalli, Y; Trettin, R

2017-07-01

Tricalciumsilicate (C 3 S, Alite) is the major component of the Portland cement clinker. Hydration of Alite is decisive in influencing the properties of the resulting material. This is due to its high content in cement. The mechanism of the hydration of C 3 S is very complicated and not yet fully understood. There are different models describing the hydration of C 3 S in various ways. In this work for a better understanding of hydration mechanism, the hydrated C 3 S was investigated by using the transmission electron microscope (TEM) and for the first time, the samples for the investigations were prepared by using of focused ion beam from sintered pellets of C 3 S. Also, an FEI Talos F200x with an integrated Super-X EDS system was used for the investigations. FEI Talos F200X combines outstanding high-resolution S/TEM and TEM imaging with energy dispersive X-ray spectroscopy signal detection, and 3D chemical characterization with compositional mapping. TEM is a very powerful tool for material science. A high energy beam of electrons passes through a very thin sample, and the interactions between the electrons and the atoms can be used to observe the structure of the material and other features in the structure. TEM can be used to study the growth of layers and their composition. TEM produces high-resolution, two-dimensional images and will be used for a wide range of educational, science and industry applications. Chemical analysis can also be performed. The purpose of these investigations was to get the information about the composition of the C-S-H phases and some details of the nanostructure of the C-S-H phases. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Correlative tomography at the cathode/electrolyte interfaces of solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Wankmüller, Florian; Szász, Julian; Joos, Jochen; Wilde, Virginia; Störmer, Heike; Gerthsen, Dagmar; Ivers-Tiffée, Ellen

2017-08-01

This paper introduces a correlative tomography technique. It visualizes the spatial organization of primary and secondary phases at the interface of La0.58Sr0.4Co0.2Fe0.8O3-δ cathode/10 mol% Gadolinia doped Ceria/8 mol% Yttria stabilized Zirconia electrolyte. It uses focused ion beam/scanning electron microscope tomography (FIB/SEM), and combines data sets from Everhart-Thornley and Inlens detector differentiating four primary and two secondary material phases. In addition, grayscale information is correlated to elemental distribution gained by energy dispersive X-ray spectroscopy in a scanning transmission electron microscope. Interdiffusion of GDC into YSZ and SrZrO3 as secondary phases depend (in both amount and spatial organization) on the varied co-sintering temperature of the GDC/YSZ electrolyte. The ion-blocking SrZrO3 forms a continuous layer on top of the temperature-dependent GDC/YSZ interdiffusion zone (ID) at and below a co-sintering temperature of 1200 °C; above it becomes intermittent. 2D FIB/SEM images of primary and secondary phases at 1100, 1200, 1300 and 1400 °C were combined with a 3D FIB/SEM reconstruction (1300 °C). This reveals that ;preferred; oxygen ion transport pathways from the LSCF cathode through GDC and the ID into the YSZ electrolyte only exist in samples sintered above 1200 °C. The applied correlative technique expands our understanding of this multiphase cathode/electrolyte interface region.

Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

PubMed Central

Shen, Haoting; Bendersky, Leonid A.; Young, Kwo; Nei, Jean

2015-01-01

The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr7Ni10, was confirmed by SEM/X-ray energy dispersive spectroscopy compositional mapping and TEM electron diffraction. Distribution of the phases and their morphology can be linked to a multi-phase structure formed by a sequence of reactions: (1) L → Zr2Ni7 + L’; (2) peritectic Zr2Ni7 + L’ → Zr2Ni7 + Zr8Ni21 + L”; (3) eutectic L” → Zr8Ni21 + Zr7Ni10. The effect of annealing at 960 °C, which was intended to convert a cast structure into a single-phase Zr8Ni21 structure, was only moderate and the resulting alloy was still multi-phased. TEM and crystallographic analysis of the Zr2Ni7 phase show a high density of planar (001) defects that were explained as low-energy boundaries between rotational variants and stacking faults. The crystallographic features arise from the pseudo-hexagonal structure of Zr2Ni7. This highly defective Zr2Ni7 phase was identified as the source of the broad X-ray diffraction peaks at around 38.4° and 44.6° when a Cu-K was used as the radiation source. PMID:28793460

Photoreduction of CO{sub 2} by TiO{sub 2} nanocomposites synthesized through reactive direct current magnetron sputter deposition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, L.; Graham, M. E.; Li, G.

The photoreduction of CO{sub 2} into methane provides a carbon-neutral energy alternative to fossil fuels, but its feasibility requires improvements in the photo-efficiency of materials tailored to this reaction. We hypothesize that mixed phase TiO{sub 2} nano-materials with high interfacial densities are extremely active photocatalysts well suited to solar fuel production by reducing CO{sub 2} to methane and shifting to visible light response. Mixed phase TiO{sub 2} films were synthesized by direct current (DC) magnetron sputtering and characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). Bundles of anatase-rutile nano-columns havingmore » high densities of two kinds of interfaces (those among the bundles and those between the columns) are fabricated. Films sputtered at a low deposition angle showed the highest methane yield, compared to TiO{sub 2} fabricated under other sputtering conditions and commercial standard Degussa P25 under UV irradiation. The yield of methane could be significantly increased ({approx} 12% CO{sub 2} conversion) by increasing the CO{sub 2} to water ratio and temperature (< 100 C) as a combined effect. These films also displayed a light response strongly shifted into the visible range. This is explained by the creation of non-stoichiometric titania films having unique features that we can potentially tailor to the solar energy applications.« less

Focal adhesion interactions with topographical structures: a novel method for immuno-SEM labelling of focal adhesions in S-phase cells.

PubMed

Biggs, M J P; Richards, R G; Wilkinson, C D W; Dalby, M J

2008-07-01

Current understanding of the mechanisms involved in osseointegration following implantation of a biomaterial has led to adhesion quantification being implemented as an assay of cytocompatibility. Such measurement can be hindered by intra-sample variation owing to morphological changes associated with the cell cycle. Here we report on a new scanning electron microscopical method for the simultaneous immunogold labelling of cellular focal adhesions and S-phase nuclei identified by BrdU incorporation. Prior to labelling, cellular membranes are removed by tritonization and antigens of non-interest blocked by serum incubation. Adhesion plaque-associated vinculin and S-phase nuclei were both separately labelled with a 1.4 nm gold colloid and visualized by subsequent colloid enhancement via silver deposition. This study is specifically concerned with the effects microgroove topographies have on adhesion formation in S-phase osteoblasts. By combining backscattered electron (BSE) imaging with secondary electron (SE) imaging it was possible to visualize S-phase nuclei and the immunogold-labelled adhesion sites in one energy 'plane' and the underlying nanotopography in another. Osteoblast adhesion to these nanotopographies was ascertained by quantification of adhesion complex formation.

Nature and evolution of incommensurate charge order in manganites visualized with cryogenic scanning transmission electron microscopy

PubMed Central

Savitzky, Benjamin H.; Admasu, Alemayehu S.; Kim, Jaewook; Cheong, Sang-Wook; Hovden, Robert; Kourkoutis, Lena F.

2018-01-01

Incommensurate charge order in hole-doped oxides is intertwined with exotic phenomena such as colossal magnetoresistance, high-temperature superconductivity, and electronic nematicity. Here, we map, at atomic resolution, the nature of incommensurate charge–lattice order in a manganite using scanning transmission electron microscopy at room temperature and cryogenic temperature (∼93 K). In diffraction, the ordering wave vector changes upon cooling, a behavior typically associated with incommensurate order. However, using real space measurements, we discover that the ordered state forms lattice-locked regions over a few wavelengths interspersed with phase defects and changing periodicity. The cations undergo picometer-scale (∼6 pm to 11 pm) transverse displacements, suggesting that charge–lattice coupling is strong. We further unearth phase inhomogeneity in the periodic lattice displacements at room temperature, and emergent phase coherence at 93 K. Such local phase variations govern the long-range correlations of the charge-ordered state and locally change the periodicity of the modulations, resulting in wave vector shifts in reciprocal space. These atomically resolved observations underscore the importance of lattice coupling and phase inhomogeneity, and provide a microscopic explanation for putative “incommensurate” order in hole-doped oxides. PMID:29382750

Tunable Electron-Electron Interactions in LaAlO 3 / SrTiO 3 Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Guanglei; Tomczyk, Michelle; Tacla, Alexandre B.

The interface between the two complex oxides LaAlO 3 and SrTiO 3 has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of “sketched” quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state) tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the d xz andmore » d yz bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.« less

Tunable Electron-Electron Interactions in LaAlO 3 / SrTiO 3 Nanostructures

DOE PAGES

Cheng, Guanglei; Tomczyk, Michelle; Tacla, Alexandre B.; ...

2016-12-01

The interface between the two complex oxides LaAlO 3 and SrTiO 3 has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of “sketched” quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state) tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the d xz andmore » d yz bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.« less

Development of a scanning time of flight microscope and its application to the study of charge transport in phase separated structured organic semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, Sanjoy; Ellman, Brett, E-mail: bellman@kent.edu; Singh, Gautam

We describe a tool for studying the two-dimensional spatial variation in electronic properties of organic semiconductors: the scanning time-of-flight microscope (STOFm). The STOFm simultaneously measures the transmittance of polarized light and time-of-flight current transients with a pixel size <30 μm, making it especially valuable for studies of the correlations of structure with charge generation and transport in liquid crystalline organic semiconductors (LC OSCs). Adapting a previously developed photopolymerization technique, we characterize the instrument using patterned samples of a LC OSC bounded by a non-semiconducting polymer matrix.

Surface phenomena of hydroxyapatite film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants.

PubMed

Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol

2013-03-01

In this study, surface phenomena of hydroxyapatite (HA) film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants have been investigated by electron beam physical vapor deposition (EB-PVD), field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), potentiostat and contact angle. The microstructure of Ti-29Nb-xZr alloys exhibited equiaxed structure and alpha" phase decreased, whereas beta phase increased as Zr content increased. The increment of Zr contents in HA coated nanotubular Ti-29Nb-xZr alloys showed good corrosion potential in 0.9% NaCI solution. The wettability of HA coated nanotubular surface was higher than that of non-coated samples.

Thermodynamic understanding of Sn whisker growth on the Cu surface in Cu(top)-Sn(bottom) bilayer system upon room temperature aging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Lin; Jian, Wei; Lin, Bing

2015-06-07

Sn whiskers are observed by scanning electron microscope on the Cu surface in Cu(top)-Sn(bottom) bilayer system upon room temperature aging. Only Cu{sub 6}Sn{sub 5} phase appears in the X-ray diffraction patterns and no Sn element is detected in the Cu sublayer by scanning transmission electron microscopy. Based on the interfacial thermodynamics, the intermetallic Cu{sub 6}Sn{sub 5} compound phase may form directly at the Sn grain boundary. Driven by the stress gradient during the formation of Cu{sub 6}Sn{sub 5} compound at Sn grain boundaries, Sn atoms segregate onto the Cu surface and accumulate to form Sn whisker.

Electron Localization in Molecular Fragmentation of H{sub 2} by Carrier-Envelope Phase Stabilized Laser Pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kremer, Manuel; Fischer, Bettina; Feuerstein, Bernold

2009-11-20

Fully differential data for H{sub 2} dissociation in ultrashort (6 fs, 760 nm), linearly polarized, intense (0.44 PW/cm{sup 2}) laser pulses with a stabilized carrier-envelope phase (CEP) were recorded with a reaction microscope. Depending on the CEP, the molecular orientation, and the kinetic energy release (KER), we find asymmetric proton emission at low KERs (0-3 eV), basically predicted by Roudnev and Esry, and much stronger than reported by Kling et al. Wave packet propagation calculations reproduce the salient features and discard, together with the observed KER-independent electron asymmetry, the first ionization step to be the reason for the asymmetric protonmore » emission.« less

Optimization of mechanical properties, biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy by heat treatment.

PubMed

Bao, Mianmian; Liu, Ying; Wang, Xiaoyan; Yang, Lei; Li, Shengyi; Ren, Jing; Qin, Gaowu; Zhang, Erlin

2018-03-01

Previous study has shown that Ti-3Cu alloy shows good antibacterial properties (>90% antibacterial rate), but the mechanical properties still need to be improved. In this paper, a series of heat-treatment processes were selected to adjust the microstructure in order to optimize the properties of Ti-3Cu alloy. Microstructure, mechanical properties, biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy at different conditions was systematically investigated by X-ray diffraction, optical microscope, scanning electron microscope, transmission electron microscopy, electrochemical measurements, tensile test, fatigue test and antibacterial test. Heat treatment could significantly improve the mechanical properties, corrosion resistance and antibacterial rate due to the redistribution of copper elements and precipitation of Ti 2 Cu phase. Solid solution treatment increased the yield strength from 400 to 740 MPa and improved the antibacterial rate from 33% to 65.2% while aging treatment enhanced the yield strength to 800-850 MPa and antibacterial rate (>91.32%). It was demonstrated that homogeneous distribution and fine Ti 2 Cu phase plays a very important role in mechanical properties, corrosion resistance and antibacterial properties.

The effect of immersion time to low carbon steel hardness and microstructure with hot dip galvanizing coating method

NASA Astrophysics Data System (ADS)

Hakim, A. A.; Rajagukguk, T. O.; Sumardi, S.

2018-01-01

Along with developing necessities of metal materials, these rise demands of quality improvements and material protections especially the mechanical properties of the material. This research used hot dip galvanizing coating method. The objectives of this research were to find out Rockwell hardness (HRb), layer thickness, micro structure and observation with Scanning Electron Microscope (SEM) from result of coating by using Hot Dip Galvanizing coating method with immersion time of 3, 6, 9, and 12 minutes at 460°C. The result shows that Highest Rockwell hardness test (HRb) was at 3 minutes immersion time with 76.012 HRb. Highest thickness result was 217.3 μm at 12 minutes immersion. Microstructure test result showed that coating was formed at eta, zeta, delta and gamma phases, while Scanning Electron Microscope (SEM) showed Fe, Zn, Mn, Si and S elements at the specimens after coating.

On universality of scaling law describing roughness of triple line.

PubMed

Bormashenko, Edward; Musin, Albina; Whyman, Gene; Barkay, Zahava; Zinigrad, Michael

2015-01-01

The fine structure of the three-phase (triple) line was studied for different liquids, various topographies of micro-rough substrates and various wetting regimes. Wetting of porous and pillar-based micro-scaled polymer surfaces was investigated. The triple line was visualized with the environmental scanning electron microscope and scanning electron microscope for the "frozen" triple lines. The value of the roughness exponent ζ for water (ice)/rough polymer systems was located within 0.55-0.63. For epoxy glue/rough polymer systems somewhat lower values of the exponent, 0.42 < ζ < 0.54, were established. The obtained values of ζ were close for the Cassie and Wenzel wetting regimes, different liquids, and different substrates' topographies. Thus, the above values of the exponent are to a great extent universal. The switch of the exponent, when the roughness size approaches to the correlation length of the defects, is also universal.

Automated thin-film analyses of hydrated interplanetary dust particles in the analytical electron microscope

NASA Technical Reports Server (NTRS)

Germani, M. S.; Bradley, J. P.; Brownlee, D. E.

1990-01-01

A 200 keV electron microscope was used to obtain elemental analyses from over 4000 points on thin sections of eight 'layer silicate' class interplanetary dust particles (IDPs). Major and minor element abundances from a volume approaching that of a cylinder 50 nm in diameter were observed. Mineral phases and their relative abundances in the thin sections were identified and petrographic characteristics were determined. Three of the particles contained smectite (1.0-1.2 nm basal spacing) and two contained serpentine (0.7 nm basal spacing). The point count analyses and Mg-Si-Fe ternary diagrams show that one of the serpentine-containing IDPs is similar to CI and CM chondritic meteorites. The IDPs exhibit evidence of aqueous processing, but they have typically experienced only short range, submicrometer scale alteration. The IDPs may provide a broad sampling of the asteroid belt.

In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles

PubMed Central

Li, Yingxuan; Zang, Ling; Jacobs, Daniel L.; Zhao, Jie; Yue, Xiu; Wang, Chuanyi

2017-01-01

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBi2Ta2O9 under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction–relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes. PMID:28194017

Synthesis and characterization of nano-hydroxyapatite in maltodextrin matrix

NASA Astrophysics Data System (ADS)

Phan, Bich T. N.; Nguyen, Hanh T.; Đao, Huong Q.; Pham, Lam V.; Quan, Trang T. T.; Nguyen, Duong B.; Nguyen, Huong T. L.; Vu, Thuan T.

2017-02-01

In this study, we report the direct precipitation of nano-HA in the present of maltodextrins with the different dextrose equivalent (DE) values in the range of 10-30. Characterization of the obtained samples, using X-ray diffraction and Fourier transform infrared spectrophotometry, indicated that the presence of maltodextrins, with the different DE values, does not affect the phase composition and structure of the obtained composites. Morphology studies of the samples, using field emission scanning electron microscope and transmission electron microscope, revealed that maltodextrin has obvious effect on the size, shape, and morphology of hydroxyapatite nanoparticles. In particular, in studied DE range, maltodextrin DE 28-30 with dominant structure of debranched chain is the most preferable choice to obtain the composite with highly dispersed nanoparticles. In vitro assay on pre-osteoblast MC3T3-E1 cells demonstrated the ability of the composites to stimulate alkaline phosphatase activity and mineralization during differentiation of the cells.

Structural and magnetic properties of chromium doped zinc ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sebastian, Rintu Mary; Thankachan, Smitha; Xavier, Sheena

2014-01-28

Zinc chromium ferrites with chemical formula ZnCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125more » nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)« less

Construction and Application of a Terahertz Scanning Near-Field Microscope for Study of Correlated Electron Materials at Cryogenic Temperatures and Nanometer Length Scales

NASA Astrophysics Data System (ADS)

Stinson, Harry Theodore, III

This dissertation describes the design and construction of the world's first cryogenic apertureless near-field microscope designed for terahertz sources and detectors. I first provide motivation for the creation of this instrument in the context of spectroscopy of correlated electron materials, and background information on the two techniques that the instrument combines, scanning near-field optical microscopy and terahertz time-domain spectroscopy. I then detail key components of the instrument design, including proof-of-principle results obtained at room and cryogenic temperatures. Following this, I discuss an imaging experiment performed with this instrument on vanadium dioxide, an insulator-metal transition material, which sheds new light on the nature of the phase transition and provides support for a new model Hamiltonian for the system. Finally, I discuss a theoretical proposal for the study of cuprate superconductors using this instrument.

In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles

NASA Astrophysics Data System (ADS)

Li, Yingxuan; Zang, Ling; Jacobs, Daniel L.; Zhao, Jie; Yue, Xiu; Wang, Chuanyi

2017-02-01

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBi2Ta2O9 under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction-relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.

In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles.

PubMed

Li, Yingxuan; Zang, Ling; Jacobs, Daniel L; Zhao, Jie; Yue, Xiu; Wang, Chuanyi

2017-02-13

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBi 2 Ta 2 O 9 under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction-relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.

L-Phenylalanine functionalized silver nanoparticles: Photocatalytic and nonlinear optical applications

NASA Astrophysics Data System (ADS)

Nidya, M.; Umadevi, M.; Sankar, Pranitha; Philip, Reji; Rajkumar, Beulah J. M.

2015-04-01

An extensive study on the behavior of L-Phenylalanine capped silver nanoparticles (Phe-Ag NPs) in the aqueous phase and in a sol-gel thin film showed different UV/Vis, Transmission Electron Microscope (TEM), Dynamic Light Scattering and Zeta potential profiles. Scanning Electron Microscope (SEM) images of the samples in the sol gel film showed Ag embedded in the SiO2 matrix. Surface Enhanced Raman Spectra (SERS) confirmed that both in the aqueous media and in the sol gel film, the attachment of Phe to the Ag NP surface was through the benzene ring, with the sol-gel film showing a better enhancement. Photocatalytic degradation of crystal violet was measured spectrophotometrically using Phe-Ag NPs as a nanocatalyst under visible light illumination. Intensity-dependent nonlinear optical absorption of Phe-Ag measured using the open aperture Z-scan technique revealed that the material is an efficient optical limiter with potential applications.

Synthesis and characterization of silver-copper core-shell nanoparticles using polyol method for antimicrobial agent

NASA Astrophysics Data System (ADS)

Hikmah, N.; Idrus, N. F.; Jai, J.; Hadi, A.

2016-06-01

Silver and copper nanoparticles are well-known as the good antimicrobial agent. The nano-size of particles influences in enhancing the antimicrobial activity. This paper discusses the effect of molarity on the microstructure and morphology of silver-copper core-shell nanoparticles prepared by a polyol method. In this study, silver-copper nanoparticles are synthesized through the green approach of polyol method using ethylene glycol (EG) as green solvent and reductant, and polyoxyethylene-(80)-sorbitan monooleate (Tween 80) as a nontoxic stabilizer. The phase and morphology of silver-copper nanoparticles are characterized by X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM) and Transmission electron microscope (TEM). The results XRD confirm the pure crystalline of silver and copper nanoparticles with face-centered cubic (FCC) structure. FESEM and TEM analysis confirm the existence of Ag and Cu nanoparticles in core-shell shape.

SQCRAMscope imaging of transport in an iron-pnictide superconductor

NASA Astrophysics Data System (ADS)

Yang, Fan; Kollar, Alicia; Taylor, Stephen; Palmstrom, Johanna; Chu, Jiun-Haw; Fisher, Ian; Lev, Benjamin

2017-04-01

Microscopic imaging of local magnetic fields provides a window into the organizing principles of complex and technologically relevant condensed matter materials. However, a wide variety of intriguing strongly correlated and topologically nontrivial materials exhibit poorly understood phenomena outside the detection capability of state-of-the-art high-sensitivity, high-resolution scanning probe magnetometers. We have recently introduced a quantum-noise-limited scanning probe magnetometer that can operate from room-to-cryogenic temperatures with unprecedented DC-field sensitivity and micron-scale resolution. The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) employs a magnetically levitated atomic Bose-Einstein condensate (BEC), thereby providing immunity to conductive and blackbody radiative heating. We will report on the first use of the SQCRAMscope for imaging a strongly correlated material. Specifically, we will present measurements of electron transport in iron-pnictide superconductors across the electron nematic phase transition at T = 135 K.

Microcinematographic and electron microscopic analysis of target cell lysis induced by cytotoxic T lymphocytes.

PubMed Central

Matter, A

1979-01-01

A study was carried out to determine the sequence of events of T-cell mediated target cell lysis in microcinematography and electron microscopy. Highly efficient cytotoxic T lymphocytes (CTL) were generated in vivo and in vitro using preimmunized spleen cells and purification procedures. Such CTL were highly specific. This specificity correlated well with the number of adhesions formed between CTL and targets and this criterion was used to study killer-target cell interaction. Microcinematography showed that target cell lysis at the single cell level, despite time variations, could be clearly separated into three phases: (a) a recognition phase, visible by random crawling of CTL over the target cell surface until firm contact was established; (b) a post-recognition phase, during which firm contact between CTL and target was maintained without gross modification of either cell; (c) a phase of target cell disintegration, mainly characterized by vigorous blebbing of the cell membrane resulting in a motionless carcass of the target cell but not in its total dissolution. Only later this carcass decayed and formed a necrotic ghost. Electron microscopic observations were put into sequence according to microcinematography. Post-recognition phase was characterized by a tight apposition of the membranes of CTL and target cell. No gap junctions could be observed. During target cell disintegration, profound cytoplasmic and nuclear changes occurred simultaneous with surface blebbing. Most noticeable were extensive internal vacuolization, mitochondrial swelling, nuclear pycnosis and dissolution of the nucleolus. These observations suggested that target cell lysis does not start with a surface phenomenon similar to complement lysis, but a process involving practically the whole cell simultaneously. It is conceivable, therefore, that the signal from the CTL is transmitted across the target cell, and that the switch to sudden cell death is manipulated deep inside the cell. Images Figure 3 Figures 4-7 Figures 8-11 Figure 12 Figures 13-14 Figure 15 PMID:312256

Local electric field direct writing – Electron-beam lithography and mechanism

DOE PAGES

Jiang, Nan; Su, Dong; Spence, John C. H.

2017-08-24

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Local electric field direct writing – Electron-beam lithography and mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Nan; Su, Dong; Spence, John C. H.

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Bioactivity of calcium phosphate bioceramic coating fabricated by laser cladding

NASA Astrophysics Data System (ADS)

Zhu, Yizhi; Liu, Qibin; Xu, Peng; Li, Long; Jiang, Haibing; Bai, Yang

2016-05-01

There were always strong expectations for suitable biomaterials used for bone regeneration. In this study, to improve the biocompatiblity of titanium alloy, calcium phosphate bioceramic coating was obtained by laser cladding technology. The microstructure, phases, bioactivity, cell differentiation, morphology and resorption lacunae were investigated by optical microscope (OM), x-ray diffraction (XRD), methyl thiazolyl tetrazolium (MTT) assay, tartrate-resistant acid phosphatase (TRAP) staining and scanning electronic microscope (SEM), respectively. The results show that bioceramic coating consists of three layers, which are a substrate, an alloyed layer and a ceramic layer. Bioactive phases of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) were found in ceramic coating. Osteoclast precursors have excellent proliferation on the bioceramic surface. The bioceramics coating could be digested by osteoclasts, which led to the resorption lacunae formed on its surface. It revealed that the gradient bioceramic coating has an excellent bioactivity.

Effects of laser polishing on surface microstructure and corrosion resistance of additive manufactured CoCr alloys

NASA Astrophysics Data System (ADS)

Wang, W. J.; Yung, K. C.; Choy, H. S.; Xiao, T. Y.; Cai, Z. X.

2018-06-01

Laser polishing of 3D printed metal components has drawn great interest in view of its potential applications in the dental implant industries. In this study, corrosion resistance, surface composition and crystalline structure of CoCr alloys were investigated. The corrosion resistance, micromorphology, composition, phase transformations and crystalline structures of samples were characterized using an electrochemical analyzer, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The results indicate that high laser powers and low object distances within a certain range can facilitate the formation of complex oxide films, which exhibits high corrosion resistance. Further, object distances have a significant influence on cooling rates during the solidification of the melt pool in laser polishing, and fast cooling generates vast amounts of vacancies and defects, which result in the crystalline phase transformation from γ to ε. Consequently, the formed oxides play an important role in corrosion resistance on the outer layer, and inner layer with γ phase also helps keep the CoCr alloys in a stable structure with high resistant to corrosion. The two process parameters in laser polishing, laser power and object distances, are demonstrated as being important for controlling the surface microstructures and corrosion resistance of the additive manufactured CoCr alloy components.

Effects of various Mg/Si ratios on microstructure and performance property of Al-Mg-Si alloy cables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xuexuan

2016-09-15

High quality AA6101 aluminum cables are critical to electrical industry to meet the energy consumption requests. In the present work, the influence of Mg/Si ratios on the electrical conductivity and mechanical properties of AA6101 aluminum alloy was investigated. Wheatstone Bridge method and tensile test were employed to characterize the mechanical properties. X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) were used to understand the morphology of the precipitation and the mechanism of age hardening. It is found that excessive Si benefits high strength and high conductivity while excessive Mg plays a negative role in the strengthmore » and the conductivity of AA6101 cables. Excessive Si elements promote both the precipitating rate and quantity of β″ phase therefore increase the tensile strength. Excessive Si elements also help with decreasing the lattice distortion, which contributes to the enhancement of the conductivity. Excessive Mg elements lead to more dissolved Mg after aging treatment, therefore increase lattice distortion of the matrix and promote the deposit of coarse Mg-enriched secondary phase. - Highlights: •A new available method to improve the mechanical and electrical properties of Al-Mg-Si alloy •Investigation on the role of various Mg/Si ratios in the changes of comprehensive performances •Discussions on the morphology of the precipitation phases and the mechanism of hardening.« less

Detection of geometric phases in superconducting nanocircuits

PubMed

Falci; Fazio; Palma; Siewert; Vedral

2000-09-21

When a quantum-mechanical system undergoes an adiabatic cyclic evolution, it acquires a geometrical phase factor' in addition to the dynamical one; this effect has been demonstrated in a variety of microscopic systems. Advances in nanotechnology should enable the laws of quantum dynamics to be tested at the macroscopic level, by providing controllable artificial two-level systems (for example, in quantum dots and superconducting devices). Here we propose an experimental method to detect geometric phases in a superconducting device. The setup is a Josephson junction nanocircuit consisting of a superconducting electron box. We discuss how interferometry based on geometrical phases may be realized, and show how the effect may be applied to the design of gates for quantum computation.

Understanding Imaging and Metrology with the Helium Ion Microscope

NASA Astrophysics Data System (ADS)

Postek, Michael T.; Vladár, András E.; Ming, Bin

2009-09-01

One barrier to innovation confronting all phases of nanotechnology is the lack of accurate metrology for the characterization of nanomaterials. Ultra-high resolution microscopy is a key technology needed to achieve this goal. But, current microscope technology is being pushed to its limits. The scanning and transmission electron microscopes have incrementally improved in performance and other scanned probe technologies such as atomic force microscopy, scanning tunneling microscopy and focused ion beam microscopes have all been applied to nanotechnology with various levels of success. A relatively new tool for nanotechnology is the scanning helium ion microscope (HIM). The HIM is a new complementary imaging and metrology technology for nanotechnology which may be able to push the current resolution barrier lower. But, successful imaging and metrology with this instrument entails new ion beam/specimen interaction physics which must be fully understood. As a new methodology, HIM is beginning to show promise and the abundance of potentially advantageous applications for nanotechnology have yet to be fully exploited. This presentation will discuss some of the progress made at NIST in understanding the science behind this new technique.

Effect of preparation conditions on the nanostructure of hydroxyapatite and brushite phases

NASA Astrophysics Data System (ADS)

Mansour, S. F.; El-dek, S. I.; Ahmed, M. A.; Abd-Elwahab, S. M.; Ahmed, M. K.

2016-10-01

Hydroxyapatite (HAP) and dicalcium phosphate dihydrate (brushite) nanoparticles were prepared by co-precipitation method. The obtained products were characterized by X-ray powder diffraction (XRD), Fourier transformation infra-red spectroscopy (FTIR) and thermo-gravimetric analysis (TGA). Scanning electron microscopy (SEM) and transmission electron microscope (TEM) were used to investigate the morphology of the powdered samples as well as their microstructure, respectively. Brushite samples were obtained in a spherical shape, while hydroxyapatite was formed in a needle and rice shape depending on the pH value.

Scanning ultrafast electron microscopy.

PubMed

Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

2010-08-24

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

Low temperature phase of the trigonal RbIn(MoO4)2 crystal

NASA Astrophysics Data System (ADS)

Zapart, W.; Zapart, M. B.; Schranz, W.; Reinecker, M.

2013-02-01

The present article is devoted to a new low-temperature phase transition found at about T pt = 84 K in the layered RbIn(MoO4)2 crystal. This phase transition is well proved by dynamical mechanical analysis through anomalies in the temperature behaviour of both real and imaginary parts of the Young's modulus. From the polarizing microscope observations it was found that below T pt the ferroelastic phase disappears. This transition has also been seen through strong changes in the shape of the electron paramagnetic resonance lines. EPR studies, performed in the liquid nitrogen temperature, yield evidence of strong rebuilding of the crystal unit cell in comparison with that of the high temperature paraelastic phase.

Scanning-tunneling microscope imaging of single-electron solitons in a material with incommensurate charge-density waves.

PubMed

Brazovskii, Serguei; Brun, Christophe; Wang, Zhao-Zhong; Monceau, Pierre

2012-03-02

We report on scanning-tunneling microscopy experiments in a charge-density wave (CDW) system allowing visually capturing and studying in detail the individual solitons corresponding to the self-trapping of just one electron. This "Amplitude Soliton" is marked by vanishing of the CDW amplitude and by the π shift of its phase. It might be the realization of the spinon--the long-sought particle (along with the holon) in the study of science of strongly correlated electronic systems. As a distinct feature we also observe one-dimensional Friedel oscillations superimposed on the CDW which develop independently of solitons.

Simultaneous phase and morphology controllable synthesis of copper selenide films by microwave-assisted nonaqueous approach

NASA Astrophysics Data System (ADS)

Li, Jing; Fa, Wenjun; Li, Yasi; Zhao, Hongxiao; Gao, Yuanhao; Zheng, Zhi

2013-02-01

Copper selenide films with different phase and morphology were synthesized on copper substrate through controlling reaction solvent by microwave-assisted nonaqueous approach. The films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The result showed that the pure films could be obtained using cyclohexyl alcohol or benzyl alcohol as solvent. The cubic Cu2-xSe dendrites were synthesized in cyclohexyl alcohol reaction system and hexagonal CuSe flaky crystals were obtained with benzyl alcohol as solvent.

Charge ordered ferromagnetic phase in La_0.5Ca_0.5MnO_3

NASA Astrophysics Data System (ADS)

Mathur, Neil

2003-03-01

Charge order and ferromagnetism should be mutually exclusive in the manganites, because ferromagnetism in these materials is normally promoted by delocalised electrons. Surprisingly, a phase that is both strongly charge ordered and fully ferromagnetic is observed [1] at 90 K in La_0.5Ca_0.5MnO_3, using Fresnel imaging, dark-field TEM and electron holography. This new phase coexists with the two low temperature phases that were already known to coexist in La_0.5Ca_0.5MnO_3. (One of these expected phases is ferromagnetic but not charge-ordered, the other is charge-ordered but not ferromagnetic.) Strain fields could be responsible for the novel microscopic texture presented here - perhaps creating conditions in which nearest neighbour hopping is sufficient to promote ferromagnetism. Similarly, strain fields are believed to cause sub-micron phase separation in the manganites. It therefore seems that the manganites can adapt to their environments over a wide range of length scales [2]. [1] http://xxx.lanl.gov/abs/cond-mat/0209436 [2] Neil Mathur and Peter Littlewood, Physics Today, early 2003.

Phase Boundary Propagation in Li-Alloying Battery Electrodes Revealed by Liquid-Cell Transmission Electron Microscopy

DOE PAGES

Leenheer, Andrew J.; Jungjohann, Katherine L.; Zavadil, Kevin R.; ...

2016-05-31

Battery cycle life is directly influenced by the microstructural changes occurring in the electrodes during charge and discharge cycles. In this study, we image in situ the nanoscale phase evolution in negative electrode materials for Li-ion batteries using a fully enclosed liquid cell in a transmission electron microscope (TEM) to reveal early degradation that is not evident in the charge–discharge curves. To compare the electrochemical phase transformation behavior between three model materials, thin films of amorphous Si, crystalline Al, and crystalline Au were lithiated and delithiated at controlled rates while immersed in a commercial liquid electrolyte. This method allowed formore » the direct observation of lithiation mechanisms in nanoscale negative electrodes, revealing that a simplistic model of a surface-to-interior lithiation front is insufficient. For the crystalline films, a lithiation front spread laterally from a few initial nucleation points, with continued grain nucleation along the growing interface. The intermediate lithiated phases were identified using electron diffraction, and high-resolution postmortem imaging revealed the details of the final microstructure. Lastly, our results show that electrochemically induced solid–solid phase transformations can lead to highly concentrated stresses at the laterally propagating phase boundary which should be considered for future designs of nanostructured electrodes for Li-ion batteries.« less

High-resolution, high-throughput imaging with a multibeam scanning electron microscope.

PubMed

Eberle, A L; Mikula, S; Schalek, R; Lichtman, J; Knothe Tate, M L; Zeidler, D

2015-08-01

Electron-electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

HRTEM low dose: the unfold of the morphed graphene, from amorphous carbon to morphed graphenes.

PubMed

Calderon, H A; Okonkwo, A; Estrada-Guel, I; Hadjiev, V G; Alvarez-Ramírez, F; Robles Hernández, F C

We present experimental evidence under low-dose conditions transmission electron microscopy for the unfolding of the evolving changes in carbon soot during mechanical milling. The milled soot shows evolving changes as a function of the milling severity or time. Those changes are responsible for the transformation from amorphous carbon to graphenes, graphitic carbon, and highly ordered structures such as morphed graphenes, namely Rh6 and Rh6-II. The morphed graphenes are corrugated layers of carbon with cross-linked covalently nature and sp 2 - or sp 3 -type allotropes. Electron microscopy and numerical simulations are excellent complementary tools to identify those phases. Furthermore, the TEAM 05 microscope is an outstanding tool to resolve the microstructure and prevent any damage to the sample. Other characterization techniques such as XRD, Raman, and XPS fade to convey a true identification of those phases because the samples are usually blends or mixes of the mentioned phases.

Effect of the microstructure on the thermoelectric properties of polycrystalline lanthanum chalcogenides

NASA Technical Reports Server (NTRS)

Lockwood, A.; Wood, C.; Vandersande, J.; Zoltan, A.; Parker, J.; Danielson, L.; Alexander, M.; Whittenberger, D.

1987-01-01

Small amounts of second phase materials can have important effects on the thermoelectric properties of polycrystalline gamma-La(3-x)X4 (X-S, Te; X in the range of 0 to 1/3). Microscopic examination by SEM of hot pressed La(3-x)Te4 samples has revealed from 1-5 vol. pct of La2O2Te, an amount which is not detected by X-ray powder diffraction measurements. This amount of La2O2Te resulting from oxygen contamination can reduce the concentration of electrons by as much as 10 to 75 percent below the electron concentration calculated for single phase La(3-x)Te4 in the composition range of greatest interest. Small amounts of second phase materials can also lower the lattice thermal conductivity by scattering low frequency phonons. These results indicate that microstructural effects should be considered when electrical and thermal properties of polycrystalline materials are analyzed.

Effect of prior deformation on microstructural development and Laves phase precipitation in high-chromium stainless steel.

PubMed

Hsiao, Z-W; Chen, D; Kuo, J-C; Lin, D-Y

2017-04-01

This study investigated the influence of deformation on precipitation behaviour and microstructure change during annealing. Here, the prior deformation of high-chromium stainless steel was tensile deformation of 3%, 6% and 10%, and the specimens were then annealed at 700˚C for 10 h. The specimens were subsequently analyzed using backscattered electron image and electron backscattering diffraction measurements with SEM. Compared with the deformation microstructure, the grains revealed no preferred orientation. The precipitates of TiN and NbC were formed homogenously in the grain interior and at grain boundaries after annealing. Fine Laves phase precipitates were observed in grains and along subgrain boundaries as the deformation increased. Furthermore, the volume fraction of Laves phase increased, but the average particle diameter of precipitate was reduced as the deformation increased. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Quantitative description of the T1 morphology and strengthening mechanisms in an age-hardenable Al-Li-Cu alloy

NASA Astrophysics Data System (ADS)

Dorin, Thomas; Deschamps, Alexis; De Geuser, Frédéric; Weyland, Matthew

In the Al-Cu-Li system, the main strengthening precipitate is the T1 phase (Al2CuLi). In order to understand the strengthening related to the formation of this phase, we first present an investigation of the morphology of the T1 phase in an AA2198 alloy using Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) in relation with the evolution of micro-hardness. In parallel, we present an investigation of the interaction between T1 precipitates and dislocations using High Angle Annular Dark Field (HAADF) imaging in an atomic resolution Scanning Transmission Electron Microscope (STEM). The atomic scale imaging of precipitates makes it possible to quantify the density of shearing events, which turns out to be insufficient to account for the imposed plastic strain. We discuss the implications of this result in terms of precipitate-dislocation interactions.

Surface crystalline phases and nanoindentation hardness of explanted zirconia femoral heads.

PubMed

Catledge, Shane A; Cook, Monique; Vohra, Yogesh K; Santos, Erick M; McClenny, Michelle D; David Moore, K

2003-10-01

One new and nine explanted zirconia femoral heads were studied using glancing angle X-ray diffraction, scanning electron microscopy, and nanoindentation hardness techniques. All starting zirconia implants consisted only of tetragonal zirconia polycrystals (TZP). For comparison, one explanted alumina femoral head was also studied. Evidence for a surface tetragonal-to-monoclinic zirconia phase transformation was observed in some implants, the extent of which was varied for different in-service conditions. A strong correlation was found between increasing transformation to the monoclinic phase and decreasing surface hardness. Microscopic investigations of some of the explanted femoral heads revealed ultra high molecular weight polyethylene and metallic transfer wear debris.

Designs for a quantum electron microscope.

PubMed

Kruit, P; Hobbs, R G; Kim, C-S; Yang, Y; Manfrinato, V R; Hammer, J; Thomas, S; Weber, P; Klopfer, B; Kohstall, C; Juffmann, T; Kasevich, M A; Hommelhoff, P; Berggren, K K

2016-05-01

One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This 'quantum weirdness' could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or "quantum electron microscope". A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Facile synthesis of Co3O4 hexagonal plates by flux method

NASA Astrophysics Data System (ADS)

Han, Ji-Long; Meng, Qing-Fen; Gao, Sheng-Li

2018-01-01

Using a novel flux method, a hexagonal plate of Co3O4 was directly synthesized. In this method, CoCl2·6H2O, NaOH, and the cosolvent H3BO3 were heated to 750 °C for 2 h in a corundum crucible. The products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscope (HRTEM). Furthermore, XRD studies indicated that the product consisted of a cubic phase of Co3O4, and the phase existed in a completely crystalline form. Then, SEM results indicated that these hexagonal plates tiered up and they had diameters in the range of 2-10 μm. According to the results of SAED and HRTEM analyses, the interlayer spacing was about 0.24 nm, which corresponds to the interlayer distance of (3 1 1) crystal plane of cubic Co3O4.

Formation of metastable phases during heat treatment of multilayers in the Al-Pt system

NASA Astrophysics Data System (ADS)

Lábár, János L.; Kovács, András; Barna, Péter B.; Gas, Patrick

2001-12-01

This communication reports that several metastable phases form subsequently during heat treatment (up to 500 °C) of Al-rich Al-Pt multilayers. Besides the known a(amorphous)-Al2Pt, formation of two metastable phases with a composition close to Al5Pt was also observed in a transmission electron microscope. One of them corresponds to a phase given by space group P4 in Pearson's collection of intermetallic compounds. The other, a hexagonal phase (a=12.4 Å and c=26.2 Å) is the one that was observed in rapidly solidified Al-Pt alloys [L. Ma, R. Wang, and K. H. Kuo, J. Less-Common Met. 163, 37 (1990)]. Formation of these phases under different conditions is reported here.

Determination of the structural phase and octahedral rotation angle in halide perovskites

DOE PAGES

dos Reis, Roberto; Yang, Hao; Ophus, Colin; ...

2018-02-12

A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr 3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr 3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurementmore » of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and comparison with simulations yield an octahedral rotation angle of 6.5°(±1.5°). Finally, the approach demonstrated here opens up opportunities for understanding the atomic scale structural phenomena applying advanced characterization tools on a wide range of radiation sensitive halide-based all-inorganic and hybrid organic-inorganic perovskites.« less

Fast Crystallization of the Phase Change Compound GeTe by Large-Scale Molecular Dynamics Simulations.

PubMed

Sosso, Gabriele C; Miceli, Giacomo; Caravati, Sebastiano; Giberti, Federico; Behler, Jörg; Bernasconi, Marco

2013-12-19

Phase change materials are of great interest as active layers in rewritable optical disks and novel electronic nonvolatile memories. These applications rest on a fast and reversible transformation between the amorphous and crystalline phases upon heating, taking place on the nanosecond time scale. In this work, we investigate the microscopic origin of the fast crystallization process by means of large-scale molecular dynamics simulations of the phase change compound GeTe. To this end, we use an interatomic potential generated from a Neural Network fitting of a large database of ab initio energies. We demonstrate that in the temperature range of the programming protocols of the electronic memories (500-700 K), nucleation of the crystal in the supercooled liquid is not rate-limiting. In this temperature range, the growth of supercritical nuclei is very fast because of a large atomic mobility, which is, in turn, the consequence of the high fragility of the supercooled liquid and the associated breakdown of the Stokes-Einstein relation between viscosity and diffusivity.

Facile synthesis and photocatalytic activity of ZnO/zinc titanate core-shell nanorod arrays

NASA Astrophysics Data System (ADS)

He, Ding-Chao; Fu, Qiu-Ming; Ma, Zhi-Bin; Zhao, Hong-Yang; Tu, Ya-Fang; Tian, Yu; Zhou, Di; Zheng, Guang; Lu, Hong-Bing

2018-02-01

ZnO/zinc titanate core-shell nanorod arrays (CSNRs) were successfully prepared via a simple synthesis process by combining hydrothermal synthesis and liquid phase deposition (LPD). The surface morphologies, crystalline characteristics, optical properties and surface electronic states of the ZnO/zinc titanate CSNRs were characterized by scanning electron microscope, transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy, PL and ultraviolet (UV)-visible absorption spectra. By controlling the reaction time of LPD, the shell thickness could vary with the reaction time. Furthermore, the impacts of the reaction time and post-annealing temperature on the crystalline structure and chemical composition of the CSNRs were also investigated. The studies of photocatalytic activity under UV light irradiation revealed that the ZnO/zinc titanate CSNRs annealed at 700 °C with 30 min deposition exhibited the best photocatalytic activity and good stability for degradation of methylene blue. It had been found that the effective separation of photogenerated electron-hole pairs in the CSNRs led to the enhanced photocatalytic activity. Moreover, the ZnO/zinc titanate CSNRs grown on quartz glass substrate could be easily recycled for reuse with almost unchanged photocatalytic activity.

2013 R&D 100 Award: Movie-mode electron microscope captures nanoscale

ScienceCinema

Lagrange, Thomas; Reed, Bryan

2018-01-26

A new instrument developed by LLNL scientists and engineers, the Movie Mode Dynamic Transmission Electron Microscope (MM-DTEM), captures billionth-of-a-meter-scale images with frame rates more than 100,000 times faster than those of conventional techniques. The work was done in collaboration with a Pleasanton-based company, Integrated Dynamic Electron Solutions (IDES) Inc. Using this revolutionary imaging technique, a range of fundamental and technologically important material and biological processes can be captured in action, in complete billionth-of-a-meter detail, for the first time. The primary application of MM-DTEM is the direct observation of fast processes, including microstructural changes, phase transformations and chemical reactions, that shape real-world performance of nanostructured materials and potentially biological entities. The instrument could prove especially valuable in the direct observation of macromolecular interactions, such as protein-protein binding and host-pathogen interactions. While an earlier version of the technology, Single Shot-DTEM, could capture a single snapshot of a rapid process, MM-DTEM captures a multiframe movie that reveals complex sequences of events in detail. It is the only existing technology that can capture multiple electron microscopy images in the span of a single microsecond.

The correlation between acoustic and magnetic properties in the long working metal boiler drum with the parameters of the electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ababkov, Nikolai, E-mail: n.ababkov@rambler.ru; Smirnov, Alexander, E-mail: galvas.kem@gmail.com

The present paper presents comparative analysis of measurement results of acoustic and magnetic properties in long working metal of boiler drums and the results obtained by methods of electronic microscopy. The structure of the metal sample from the fracture zone to the base metal (metal working sample long) and the center of the base metal before welding (weld metal sample) was investigated by electron microscopy. Studies performed by spectral acoustic, magnetic noise and electron microscopic methods were conducted on the same plots and the same samples of long working and weld metal of high-pressure boiler drums. The analysis of researchmore » results showed high sensitivity of spectral-acoustic and magnetic-noise methods to definition changes of microstructure parameters. Practical application of spectral-acoustic and magnetic noise NDT method is possible for the detection of irregularities and changes in structural and phase state of the long working and weld metal of boiler drums, made of a special molybdenum steel (such as 20M). The above technique can be used to evaluate the structure and physical-mechanical properties of the long working metal of boiler drums in the energy sector.« less

2013 R&D 100 Award: Movie-mode electron microscope captures nanoscale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lagrange, Thomas; Reed, Bryan

2014-04-03

A new instrument developed by LLNL scientists and engineers, the Movie Mode Dynamic Transmission Electron Microscope (MM-DTEM), captures billionth-of-a-meter-scale images with frame rates more than 100,000 times faster than those of conventional techniques. The work was done in collaboration with a Pleasanton-based company, Integrated Dynamic Electron Solutions (IDES) Inc. Using this revolutionary imaging technique, a range of fundamental and technologically important material and biological processes can be captured in action, in complete billionth-of-a-meter detail, for the first time. The primary application of MM-DTEM is the direct observation of fast processes, including microstructural changes, phase transformations and chemical reactions, that shapemore » real-world performance of nanostructured materials and potentially biological entities. The instrument could prove especially valuable in the direct observation of macromolecular interactions, such as protein-protein binding and host-pathogen interactions. While an earlier version of the technology, Single Shot-DTEM, could capture a single snapshot of a rapid process, MM-DTEM captures a multiframe movie that reveals complex sequences of events in detail. It is the only existing technology that can capture multiple electron microscopy images in the span of a single microsecond.« less

Phase-shifting interference microscope with extendable field of measurement

NASA Astrophysics Data System (ADS)

Lin, Shyh-Tsong; Hsu, Wei-Feng; Wang, Ming-Shiang

2018-04-01

An innovative phase-shifting interference microscope aimed at extending the field of measurement is proposed in this paper. The microscope comprises a light source module, a phase modulation module, and an interferometric module, which reconstructs the micro-structure contours of samples using the five-step phase-shifting algorithm. This paper discusses the measurement theory and outlines the configuration, experimental setup, and experimental results obtained using the proposed interference microscope. The results confirm the efficacy of the microscope, achieving a standard deviation of 2.4 nm from a step height of 86.2 nm in multiple examinations.

Heterodyne Interferometry with a Scanning Optical Microscope.

NASA Astrophysics Data System (ADS)

Hobbs, Philip Charles Danby

The design and implementation of a confocal optical microscope which functions as an electronically scanned heterodyne interferometer are described. Theoretical models based on Fourier optics for general samples and on exact series solution of the scalar Helmholtz equation for a class of trench structures are developed and compared with experimental data. Good agreement is obtained. The associated data acquisition system, also described, enables the system to measure both the amplitude (to 12 bits) and the phase (to 0.1^circ) of a returned optical beam, at a continuous rate of 30,000 points per second. The microscope system uses a wide-band tellurium dioxide acousto-optic cell for electronic scanning, frequency shifting, and beam splitting/combining. It uses a stationary reference beam on the sample for vibration cancellation, which results in a system of great vibration immunity. It can measure relief ranging from a few tenths of a micron down to a few Angstroms, and line widths down to well below 0.4 micron, using light of 0.5 micron wavelength. Angstrom resolution can be achieved in a single full-speed scan, without special vibration isolation equipment, providing that folding mirrors are avoided. A signal processing algorithm based on Fourier deconvolution is presented; it takes advantage of the extra bandwidth of a confocal system and the availability of both amplitude and phase, to improve the lateral resolution by approximately a factor of two. Experimental results are shown, which demonstrate phase edge resolution (10%-90%) of 0.45 lambda (raw data), and 0.18 lambda (after filtering), in excellent agreement with the Fourier optics prediction. The exact scalar theory calculates the response of the microscope as it scans over an infinitely long rectangular trench in a plane boundary on which Dirichlet boundary conditions apply. An expansion in cavity modes inside the trench is used to match the field and its derivatives across the mouth of the trench to get the self-consistent solution. A listing is appended of a program for an HP personal computer which performs the simulation in 1 to 5 minutes' running time for most cases. The trench theory is compared with the Fourier theory and with experimental results for actual metal trenches, with good results.

Sb,123121 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb2: Emergence of electronic Griffith phase, magnetism, and metallic behavior

NASA Astrophysics Data System (ADS)

Gippius, A. A.; Zhurenko, S. V.; Hu, R.; Petrovic, C.; Baenitz, M.

2018-02-01

Sb,123121 nuclear quadrupole resonance (NQR) was applied to Fe(Sb1-xTex)2 in the low doping regime (x =0 , 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3 d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1 /T1(T ) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb2 with a clear signature of the charge and spin gap formation in 1 /T1(T ) T [˜exp/(Δ kBT ) ] , the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1 /T1(T ) T ˜T-n˜T-0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ =(Cel/T ) showing a power-law divergence γ (T ) ˜T-m˜(1/T1T ) 1 /2˜T-n /2˜Cel/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1 /T1(T ) T ˜T-0.72 . According to the specific heat divergence a power law with n =2 m =0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1 /T1(T ) T ˜T-3 /4 behavior. Furthermore Te-doped FeSb2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the Sb,123121 NQR spectrum for the 5% sample. This has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.

Sb 121 , 123 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb 2 : Emergence of electronic Griffith phase, magnetism, and metallic behavior

DOE PAGES

Gippius, A. A.; Zhurenko, S. V.; Hu, R.; ...

2018-02-12

121,123Sb nuclear quadrupole resonance (NQR) was applied to Fe(Sb 1-xTe x) 2 in the low doping regime (x = 0 , 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1/T 1 (T) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb 2 with a clear signaturemore » of the charge and spin gap formation in 1/T 1(T)T[~exp/(Δk BT)] , the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1/T 1(T)T ~ T -n ~ T -0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ = (C el/T) showing a power-law divergence γ (T) ~ T -m ~ (1/T 1T) 1/2 ~ T -n/2 ~ C el/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1/T 1(T)T ~ T -0.72 . According to the specific heat divergence a power law with n = 2 m = 0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1/T 1(T)T ~ T -3/4 behavior. Furthermore Te-doped FeSb 2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the 121,123Sb NQR spectrum for the 5% sample. Lastly, this has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.« less

Sb 121 , 123 nuclear quadrupole resonance as a microscopic probe in the Te-doped correlated semimetal FeSb 2 : Emergence of electronic Griffith phase, magnetism, and metallic behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gippius, A. A.; Zhurenko, S. V.; Hu, R.

121,123Sb nuclear quadrupole resonance (NQR) was applied to Fe(Sb 1-xTe x) 2 in the low doping regime (x = 0 , 0.01, and 0.05) as a microscopic zero field probe to study the evolution of 3d magnetism and the emergence of metallic behavior. Whereas the NQR spectra itself reflects the degree of local disorder via the width of the individual NQR lines, the spin lattice relaxation rate (SLRR) 1/T 1 (T) probes the fluctuations at the Sb site. The fluctuations originate either from conduction electrons or from magnetic moments. In contrast to the semimetal FeSb 2 with a clear signaturemore » of the charge and spin gap formation in 1/T 1(T)T[~exp/(Δk BT)] , the 1% Te-doped system exhibits almost metallic conductivity and the SLRR nicely confirms that the gap is almost filled. A weak divergence of the SLRR coefficient 1/T 1(T)T ~ T -n ~ T -0.2 points towards the presence of electronic correlations towards low temperatures. This is supported by the electronic specific heat coefficient γ = (C el/T) showing a power-law divergence γ (T) ~ T -m ~ (1/T 1T) 1/2 ~ T -n/2 ~ C el/T which is expected in the renormalized Landau Fermi liquid theory for correlated electrons. In contrast to that the 5% Te-doped sample exhibits a much larger divergence in the SLRR coefficient showing 1/T 1(T)T ~ T -0.72 . According to the specific heat divergence a power law with n = 2 m = 0.56 is expected for the SLRR. This dissimilarity originates from admixed critical magnetic fluctuations in the vicinity of antiferromagnetic long range order with 1/T 1(T)T ~ T -3/4 behavior. Furthermore Te-doped FeSb 2 as a disordered paramagnetic metal might be a platform for the electronic Griffith phase scenario. NQR evidences a substantial asymmetric broadening of the 121,123Sb NQR spectrum for the 5% sample. Lastly, this has a predominant electronic origin in agreement with the electronic Griffith phase and stems probably from an enhanced Sb-Te bond polarization and electronic density shift towards the Te atom inside Sb-Te dumbbell.« less

75 FR 13486 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-22

... University, One Waterfront Place, PO Box 6024, Morgantown, WV 26506. Instrument: Electron Microscope.... Justification for Duty-Free Entry: There are no domestic manufacturers of this type of electron microscope.... Lawrence University, 23 Romoda Drive, Canton, NY 13617. Instrument: Electron Microscope. Manufacturer: FEI...

Pulsed Electrodeposition of Amorphous and Composite Alloys.

DTIC Science & Technology

1983-09-01

lamellar- eutectic composites. A new phenomenon was dis- covered that deposits consisting of alternate layers of the same phase and essentially the...phenomenon will be discussed in connection with the Cu-Zn alloys. The recrystallization kinetics of the Ni-Mo alloys were investigated in order to find...transmission-electron-microscopic examination. The percent of the area which had recrystallized was determined on photographs using a planimeter. From a

Investigation of phase transition properties of ZrO2 thin films

NASA Astrophysics Data System (ADS)

Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

2018-05-01

This paper presents the synthesis of transparent thin films of zirconium oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Synthesized films were characterized for different annealing time and withdrawal speed. Change in crystallographic properties of thin films was investigated by using X-ray diffraction. Surface morphology of transparent thin films was estimated by using scanning electron microscope.

Structure-phase state and mechanical properties of surface layers in titanium nikelide single crystals after shock mechanical treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surikova, N., E-mail: surikova@ispms.tsc.ru; Panin, V., E-mail: paninve@ispms.tsc.ru; Vlasov, I.

2015-10-27

The influence of ultrasonic shock surface treatment (USST) on refine structure and mechanical characteristics of surface layers and deformation behaviour of volume samples of TiNi(Fe, Mo) shape memory effect alloy single crystals is studied using optical and transmission electron microscope, X-ray diffraction, nanoindentation, mechanical attrition testing and experiments on uniaxial tension.

Structure-phase state and mechanical properties of surface layers in titanium nikelide single crystals after shock mechanical treatment

NASA Astrophysics Data System (ADS)

Surikova, N.; Panin, V.; Vlasov, I.; Narkevich, N.; Surikov, N.; Tolmachev, A.

2015-10-01

The influence of ultrasonic shock surface treatment (USST) on refine structure and mechanical characteristics of surface layers and deformation behaviour of volume samples of TiNi(Fe, Mo) shape memory effect alloy single crystals is studied using optical and transmission electron microscope, X-ray diffraction, nanoindentation, mechanical attrition testing and experiments on uniaxial tension.

Electron microscopic study of developmental stages of Rickettsiella phytoseiuli in Phytoseiulus persimilis Athias-Henriot (Gamasoidea:Phytoseiidae) mites.

PubMed

Sutáková, G

1988-01-01

Rickettsiella phytoseiuli was found in great amounts in all tissues except of the nervous system of adult Phytoseiulus persimilis mites. Six morphologically different stages (dense, intermediate, bacterial, giant, crystal-forming and small dark particles) of R. phytoseiuli were detected. No rickettsiae were seen in the larvae and in phase 1 and 2 nymphae of these mites.

Probing microstructure and phase evolution of α-MoO 3 nanobelts for sodium-ion batteries by in situ transmission electron microscopy

DOE PAGES

Xia, Weiwei; Xu, Feng; Zhu, Chongyang; ...

2016-07-15

The fundamental electrochemical reaction mechanisms and the phase transformation pathways of layer-structured α-MoO 3 nanobelt during the sodiation/desodiation process to date remain largely unknown. In this study, to observe the real-time sodiation/desodiaton behaviors of α-MoO 3 during electrochemical cycling, we construct a MoO 3 anode sodium-ion battery inside a transmission electron microscope (TEM). Utilizing in situ TEM and electron diffraction pattern (EDP) observation, α-MoO 3 nanobelts are found to undergo a unique multi-step phase transformation. Upon the first sodiation, α-MoO 3 nanobelts initially form amorphous Na xMoO3 phase and are subsequently sodiated into intermediate phase of crystalline NaMoO 2, finallymore » resulting in the crystallized Mo nanograins embedded within the Na 2O matrix. During the first desodiation process, Mo nanograins are firstly re-oxidized into intermediate phase NaMoO 2 that is further transformed into amorphous Na 2MoO 3, resulting in an irreversible phase transformation. Upon subsequent sodiation/desodiation cycles, however, a stable and reversible phase transformation between crystalline Mo and amorphous Na2MoO 3 phases has been revealed. In conclusion, our work provides an in-deepth understanding of the phase transformation pathways of α-MoO 3 nanobelts upon electrochemical sodiation/desodiation processes, with the hope of assistance in designing sodium-ion batteries with enhanced performance.« less

Ligand exchange synthesis of organometallic Rh nanoparticles and application in explosive sensing

NASA Astrophysics Data System (ADS)

Srivastav, Amit K.; Agrawal, Bhavesh; Swami, Bhavya; Agrawal, Yadvendra K.; Maity, Prasenjit

2017-06-01

Alkyne {phenyl acetylene (PA) and 9-ethynylphenanthrene (EPT)}-ligated Rh nanoparticles ( 1 and 2, respectively) with mean diameter of 1.5 ± 0.2 nm were synthesized via a facile and high-yield biphasic ligand exchange protocol using similar sized ethylene glycol (EG)-stabilized Rh nanoparticles as precursors (EG:Rh). The synthesized organometallic Rh nanoparticles were convincingly characterized using several spectroscopic and microscopic techniques, e.g., Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), optical absorption spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscope (TEM). We propose that the syntheses mechanism relies on catalytic acetylenic (≡C-H, carbon-hydrogen) bond breaking by EG:Rh followed by strong metal-carbon bond formation with a vinyldiene (>C═C═M) motif. The obtained 1 and 2 showed luminescence property, which arises from ligand structure through intraparticle conjugation. Electron-rich phenanthrene-ligated Rh nanoparticles ( 2) showed good sensing performance for detection of electron deficient nitro-aromatic explosive molecules (NA) in solution phase through luminescence quenching method.

ZnO/TiO2 nanocomposite rods synthesized by microwave-assisted method for humidity sensor application

NASA Astrophysics Data System (ADS)

Ashok, CH.; Venkateswara Rao, K.

2014-12-01

The nanocomposite rods shows well known properties compared with nano structured materials for various applications like light-emitting diodes, electron field emitters, solar cells, optoelectronics, sensors, transparent conductors and fabrication of nano devices. Present paper investigates the properties of ZnO/TiO2 nanocomposite rods. The bi component of ZnO/TiO2 nanocomposite rods was synthesized by microwave-assisted method which is very simple, rapid and uniform in heating. The frequency of microwaves 2.45 GHz was used and temperature maintained 180 °C. Zinc acetate and titanium isopropoxide precursors were used in the preparation. The obtained ZnO/TiO2 nanocomposite rods were annealed at 500 °C and 600 °C. ZnO/TiO2 nanocomposite rods have been characterized by X-ray Diffraction (XRD) for average crystallite size and phase of the composite material, Particle Size Analyser (PSA) for average particle size, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) for morphology study, Energy Dispersive X-ray Spectrometry (EDX) for elemental analysis, and Thermal Gravimetric and Differential Thermal Analysis (TG-DTA) for thermal property.

Skeletal growth phases of the cold-water coral Lophelia pertusa shown by scanning electron microscope and electron backscatter diffraction

NASA Astrophysics Data System (ADS)

Mouchi, Vincent; Vonlanthen, Pierre; Verrecchia, Eric P.; Crowley, Quentin G.

2016-04-01

Lophelia pertusa is a cold-water coral, which may form reefs by the association of multiple coralites within which a polyp lives. Each individual polyp builds an aragonite skeleton by an initial phase of early mineralization (traditionally referred to as centres of calcification) from which aragonite fibres grow in thickening deposits. The skeleton wall features successive optically opaque and translucent bands previously attributed to different regimes of growth as either uniform in crystal orientation (translucent bands) or with a chaotic organization (opaque bands). The processes involved in any organizational changes are still unknown. Microlayers in the coral wall, which represent separate periods of skeletal growth, have been recently identified and described. These growth patterns are readily visible under scanning electron microscope (SEM) after etching in dilute formic acid, but they do not necessarily form continuously visible structures. Here we present high quality SEM images and electron backscatter diffraction (EBSD) maps to study aragonite fibre orientation across the wall of L. pertusa. Both microlayers and opaque and translucent bands are compared to the crystallographic orientation of the aragonite fibres. EBSD maps and SEM images indicate that aragonite fibres do not exhibit a chaotic orientation, even in opaque bands. The absence of continuity of microlayers is partially explained by an association of multiple crystallographic preferred orientations of aragonite fibres. In the case of L. pertusa, careful textural characterisation is necessary prior to elemental or isotope analysis in order to select a skeletal transect representing a linear and continuous time period.

Newly recognized hosts for uranium in the Hanford Site vadose zone

USGS Publications Warehouse

Stubbs, J.E.; Veblen, L.A.; Elbert, D.C.; Zachara, J.M.; Davis, J.A.; Veblen, D.R.

2009-01-01

Uranium contaminated sediments from the U.S. Department of Energy's Hanford Site have been investigated using electron microscopy. Six classes of solid hosts for uranium were identified. Preliminary sediment characterization was carried out using optical petrography, and electron microprobe analysis (EMPA) was used to locate materials that host uranium. All of the hosts are fine-grained and intergrown with other materials at spatial scales smaller than the analytical volume of the electron microprobe. A focused ion beam (FIB) was used to prepare electron-transparent specimens of each host for the transmission electron microscope (TEM). The hosts were identified as: (1) metatorbernite [Cu(UO2)2(PO4)2??8H2O]; (2) coatings on sediment clasts comprised mainly of phyllosilicates; (3) an amorphous zirconium (oxyhydr)oxide found in clast coatings; (4) amorphous and poorly crystalline materials that line voids within basalt lithic fragments; (5) amorphous palagonite surrounding fragments of basaltic glass; and (6) Fe- and Mn-oxides. These findings demonstrate the effectiveness of combining EMPA, FIB, and TEM to identify solid-phase contaminant hosts. Furthermore, they highlight the complexity of U geochemistry in the Hanford vadose zone, and illustrate the importance of microscopic transport in controlling the fate of contaminant metals in the environment. ?? 2008 Elsevier Ltd.

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... decision consolidated pursuant to Section 6(c) of the Educational, Scientific, and Cultural Materials... 07470. Instrument: Electron Microscope. Manufacturer: Hitachi High Technologies America, Inc., Japan... educational uses requiring an electron microscope. We know of no electron microscope, or any other instrument...

The Design and Construction of a Simple Transmission Electron Microscope for Educational Purposes.

ERIC Educational Resources Information Center

Hearsey, Paul K.

This document presents a model for a simple transmission electron microscope for educational purposes. This microscope could demonstrate thermonic emission, particle acceleration, electron deflection, and flourescence. It is designed to be used in high school science courses, particularly physics, taking into account the size, weight, complexity…

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Secondary electron imaging of monolayer materials inside a transmission electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cretu, Ovidiu, E-mail: cretu.ovidiu@nims.go.jp; Lin, Yung-Chang; Suenaga, Kazutomo

2015-08-10

A scanning transmission electron microscope equipped with a backscattered and secondary electron detector is shown capable to image graphene and hexagonal boron nitride monolayers. Secondary electron contrasts of the two lightest monolayer materials are clearly distinguished from the vacuum level. A signal difference between these two materials is attributed to electronic structure differences, which will influence the escape probabilities of the secondary electrons. Our results show that the secondary electron signal can be used to distinguish between the electronic structures of materials with atomic layer sensitivity, enhancing its applicability as a complementary signal in the analytical microscope.

Lattice relations and solidification of the complex regular eutectic (Cr,Fe)-(Cr,Fe)23C6

NASA Astrophysics Data System (ADS)

Lai, Hsuan-Han; Hsieh, Chih-Chun; Lin, Chi-Ming; Wu, Weite

2017-05-01

The eutectic (Cr,Fe)-(Cr,Fe)23C6 showed a triaxial fishbone structure and could be categorized as a "complex regular structure". In this study, the lattice relations of the fishbone (Cr,Fe)23C6 were examined and the solidification process was observed using a transmission electron microscope and a confocal laser scanning microscope. For one of the three fish bones in a eutectic cell, parallel (Cr,Fe)23C6 lamellas at one side of the spine had the same lattice direction, as did those in the (Cr,Fe) phase. The lattices of neighboring (Cr,Fe)23C6 and (Cr,Fe) phases were not coherent. Lamellar (Cr,Fe)23C6 on opposite sides of a spine had different lattice directions, and their lattice boundary was in the spine. By using the confocal laser scanning microscope, the solidification of lamellar eutectic structure could be observed. At the low cooling rate of 5 o C·min-1, parallel lamellas would grow thick blocks instead of thin plates. To obtain a thin lamellar eutectic structure, the cooling rate should be higher, like the rate in welding.

DOE Office of Scientific and Technical Information (OSTI.GOV)

dos Reis, Roberto; Yang, Hao; Ophus, Colin

A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr 3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr 3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurementmore » of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and comparison with simulations yield an octahedral rotation angle of 6.5°(±1.5°). Finally, the approach demonstrated here opens up opportunities for understanding the atomic scale structural phenomena applying advanced characterization tools on a wide range of radiation sensitive halide-based all-inorganic and hybrid organic-inorganic perovskites.« less

Integration of a high-NA light microscope in a scanning electron microscope.

PubMed

Zonnevylle, A C; Van Tol, R F C; Liv, N; Narvaez, A C; Effting, A P J; Kruit, P; Hoogenboom, J P

2013-10-01

We present an integrated light-electron microscope in which an inverted high-NA objective lens is positioned inside a scanning electron microscope (SEM). The SEM objective lens and the light objective lens have a common axis and focal plane, allowing high-resolution optical microscopy and scanning electron microscopy on the same area of a sample simultaneously. Components for light illumination and detection can be mounted outside the vacuum, enabling flexibility in the construction of the light microscope. The light objective lens can be positioned underneath the SEM objective lens during operation for sub-10 μm alignment of the fields of view of the light and electron microscopes. We demonstrate in situ epifluorescence microscopy in the SEM with a numerical aperture of 1.4 using vacuum-compatible immersion oil. For a 40-nm-diameter fluorescent polymer nanoparticle, an intensity profile with a FWHM of 380 nm is measured whereas the SEM performance is uncompromised. The integrated instrument may offer new possibilities for correlative light and electron microscopy in the life sciences as well as in physics and chemistry. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heo, Yooun; Lee, Jin Hong; Xie, Lin

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

Corrosion resistance evaluation of Pd-free Ag-Au-Pt-Cu dental alloys.

PubMed

Fujita, Takeshi; Shiraishi, Takanobu; Takuma, Yasuko; Hisatsune, Kunihiro

2011-01-01

The corrosion resistance of nine experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.9% NaCl solution was investigated using cyclic voltammetry (CV), optical microscopy, and scanning electron microscopy (SEM). CV measurements revealed that the breakdown potential (E(bd)) and zero current potential (E(zc)) increased with increasing Au/(Au+Ag) atomic ratio. Thus, the Au/(Au+Ag) atomic ratio, but not the Cu content, influenced the corrosion resistance of Ag-Au-Pt-Cu alloys. After the forward scan of CV, both optical and scanning electron microscope images showed that in all the experimental alloys, the matrix phase was corroded but not the second phase. From corrosion resistance viewpoint, the Ag-Au-Pt-Cu alloys seemed to be suitable for clinical application.

Time-resolved imaging of gas phase nanoparticle synthesis by laser ablation

NASA Astrophysics Data System (ADS)

Geohegan, David B.; Puretzky, Alex A.; Duscher, Gerd; Pennycook, Stephen J.

1998-06-01

The dynamics of nanoparticle formation, transport, and deposition by pulsed laser ablation of c-Si into 1-10 Torr He and Ar gases are revealed by imaging laser-induced photoluminescence and Rayleigh-scattered light from gas-suspended 1-10 nm SiOx particles. Two sets of dynamic phenomena are presented for times up to 15 s after KrF-laser ablation. Ablation of Si into heavier Ar results in a uniform, stationary plume of nanoparticles, while Si ablation into lighter He results in a turbulent ring of particles which propagates forward at 10 m/s. Nanoparticles unambiguously formed in the gas phase were collected on transmission electron microscope grids for Z-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle formation, photoluminescence, and collection are described.

Atmospheric scanning electron microscope observes cells and tissues in open medium through silicon nitride film.

PubMed

Nishiyama, Hidetoshi; Suga, Mitsuo; Ogura, Toshihiko; Maruyama, Yuusuke; Koizumi, Mitsuru; Mio, Kazuhiro; Kitamura, Shinichi; Sato, Chikara

2010-03-01

Direct observation of subcellular structures and their characterization is essential for understanding their physiological functions. To observe them in open environment, we have developed an inverted scanning electron microscope with a detachable, open-culture dish, capable of 8 nm resolution, and combined with a fluorescence microscope quasi-simultaneously observing the same area from the top. For scanning electron microscopy from the bottom, a silicon nitride film window in the base of the dish maintains a vacuum between electron gun and open sample dish while allowing electrons to pass through. Electrons are backscattered from the sample and captured by a detector under the dish. Cells cultured on the open dish can be externally manipulated under optical microscopy, fixed, and observed using scanning electron microscopy. Once fine structures have been revealed by scanning electron microscopy, their component proteins may be identified by comparison with separately prepared fluorescence-labeled optical microscopic images of the candidate proteins, with their heavy-metal-labeled or stained ASEM images. Furthermore, cell nuclei in a tissue block stained with platinum-blue were successfully observed without thin-sectioning, which suggests the applicability of this inverted scanning electron microscope to cancer diagnosis. This microscope visualizes mesoscopic-scale structures, and is also applicable to non-bioscience fields including polymer chemistry. (c) 2010 Elsevier Inc. All rights reserved.

Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity

PubMed Central

Davis, J. C. Séamus; Lee, Dung-Hai

2013-01-01

Unconventional superconductivity (SC) is said to occur when Cooper pair formation is dominated by repulsive electron–electron interactions, so that the symmetry of the pair wave function is other than an isotropic s-wave. The strong, on-site, repulsive electron–electron interactions that are the proximate cause of such SC are more typically drivers of commensurate magnetism. Indeed, it is the suppression of commensurate antiferromagnetism (AF) that usually allows this type of unconventional superconductivity to emerge. Importantly, however, intervening between these AF and SC phases, intertwined electronic ordered phases (IP) of an unexpected nature are frequently discovered. For this reason, it has been extremely difficult to distinguish the microscopic essence of the correlated superconductivity from the often spectacular phenomenology of the IPs. Here we introduce a model conceptual framework within which to understand the relationship between AF electron–electron interactions, IPs, and correlated SC. We demonstrate its effectiveness in simultaneously explaining the consequences of AF interactions for the copper-based, iron-based, and heavy-fermion superconductors, as well as for their quite distinct IPs. PMID:24114268

Effect of Cooling Rates on γ → α Transformation and Metastable States in Fe-Cu Alloys with Addition of Ni

NASA Astrophysics Data System (ADS)

Crozet, C.; Verdier, M.; Lay, S.; Antoni-Zdziobek, A.

2018-07-01

α/γ phase transformations occurring in Fe-10Cu-xNi alloys (0 ≤ x ≤ 15 in mass%) were studied using X-ray diffraction, scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy and chemical analysis, combining X-ray microanalysis with energy dispersive spectrometry in the scanning electron microscope and electron microprobe analysis with wavelength dispersive spectrometry. The influence of cooling rate on the microstructure was investigated using ice-brine quenching and 2 °C/min slow cooling rate performed with dilatometry. Ni addition induces metastable transformations on cooling: massive and bainitic ferrite are formed depending on the alloy composition and cooling rate. Moreover, most of the Cu phase precipitates on cooling giving rise to a fine distribution of Cu particles in the ferrite grains. For both cooling conditions, the hardness increases with increasing Ni content and a higher hardness is obtained in the quenched alloy for each composition. The change in hardness is correlated to the effect of Ni solid solution, transformation structure and size of Cu particles.

Azimuthal phase retardation microscope for visualizing actin filaments of biological cells

NASA Astrophysics Data System (ADS)

Shin, In Hee; Shin, Sang-Mo

2011-09-01

We developed a new theory-based azimuthal phase retardation microscope to visualize distributions of actin filaments in biological cells without having them with exogenous dyes, fluorescence labels, or stains. The azimuthal phase retardation microscope visualizes distributions of actin filaments by measuring the intensity variations of each pixel of a charge coupled device camera while rotating a single linear polarizer. Azimuthal phase retardation δ between two fixed principal axes was obtained by calculating the rotation angles of the polarizer at the intensity minima from the acquired intensity data. We have acquired azimuthal phase retardation distributions of human breast cancer cell, MDA MB 231 by our microscope and compared the azimuthal phase retardation distributions with the fluorescence image of actin filaments by the commercial fluorescence microscope. Also, we have observed movement of human umbilical cord blood derived mesenchymal stem cells by measuring azimuthal phase retardation distributions.

Proximity coupling in superconductor-graphene heterostructures.

PubMed

Lee, Gil-Ho; Lee, Hu-Jong

2018-05-01

This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

Synthesis of TiO2 Nanoparticle and its phase Transition

NASA Astrophysics Data System (ADS)

Mangrola, M. H.; Joshi, V. G.; Parmar, B. H.

2011-12-01

Here we report the synthesis of titanium dioxide (TiO2) nanoparticles and study of its phase transition from anataze to rutile. Titanium dioxide (TiO2) nanoparticles have been prepared by hydrolysis of Titanium isopropoxide an aqueous solution with constant value of pH 2 and peptizing the resultant suspension gel(white-Blue) and calcinate gel at different temperature. Structures of synthetic samples of TiO2 have been examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). The anatase-rutile transition has been a popular topic due to its interest to scientific and engineering fields. . Here we have seen that the 100 °C calcinate powder consist of anatase fine crystalline phase with a particle size 14 to 15 nm. The prepared TiO2 nanoparticles have uniform size and morphology, and the phase transformation kinetics of obtained material was studied by interpretation of the X-ray diffraction patterns peaks. The phase transform occurred from anatase to rutile at calcinate temperature up to 600 °C. A very fine network texture made from uniform nanoparticles was revealed by scanning electron microscopy (SEM) analyses.

Proximity coupling in superconductor-graphene heterostructures

NASA Astrophysics Data System (ADS)

Lee, Gil-Ho; Lee, Hu-Jong

2018-05-01

This review discusses the electronic properties and the prospective research directions of superconductor-graphene heterostructures. The basic electronic properties of graphene are introduced to highlight the unique possibility of combining two seemingly unrelated physics, superconductivity and relativity. We then focus on graphene-based Josephson junctions, one of the most versatile superconducting quantum devices. The various theoretical methods that have been developed to describe graphene Josephson junctions are examined, together with their advantages and limitations, followed by a discussion on the advances in device fabrication and the relevant length scales. The phase-sensitive properties and phase-particle dynamics of graphene Josephson junctions are examined to provide an understanding of the underlying mechanisms of Josephson coupling via graphene. Thereafter, microscopic transport of correlated quasiparticles produced by Andreev reflections at superconducting interfaces and their phase-coherent behaviors are discussed. Quantum phase transitions studied with graphene as an electrostatically tunable 2D platform are reviewed. The interplay between proximity-induced superconductivity and the quantum-Hall phase is discussed as a possible route to study topological superconductivity and non-Abelian physics. Finally, a brief summary on the prospective future research directions is given.

Characterization of Microstructure and Mechanical Properties of Mg-8Li-3Al-1Y Alloy Subjected to Different Rolling Processes

NASA Astrophysics Data System (ADS)

Zhou, Xiao; Liu, Qiang; Liu, Ruirui; Zhou, Haitao

2018-06-01

The mechanical properties and microstructure evolution of Mg-8Li-3Al-1Y alloy undergoing different rolling processes were systematically investigated. X-ray diffraction, optical microscope, scanning electron microscopy, transmission electron microscopy as well as electron backscattered diffraction were used for tracking the microstructure evolution. Tensile testing was employed to characterize the mechanical properties. After hot rolling, the MgLi2Al precipitated in β-Li matrix due to the transformation reaction: β-Li → β-Li + MgLi2Al + α-Mg. As for the alloy subjected to annealed hot rolling, β-Li phase was clearly recrystallized while recrystallization rarely occurred in α-Mg phase. With regard to the microstructure undergoing cold rolling, plenty of dislocations and dislocation walls were easily observed. In addition, the microstructure of alloys subjected to annealed cold rolling revealed the formation of new fresh α-Mg grains in β-Li phase due to the precipitation reaction. The mechanical properties and fracture modes of Mg-8Li-3Al-1Y alloys can be effectively tuned by different rolling processes.

Enhanced conductivity at orthorhombic–rhombohedral phase boundaries in BiFeO 3 thin films

DOE PAGES

Heo, Yooun; Lee, Jin Hong; Xie, Lin; ...

2016-08-26

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

Nature and evolution of incommensurate charge order in manganites visualized with cryogenic scanning transmission electron microscopy.

PubMed

El Baggari, Ismail; Savitzky, Benjamin H; Admasu, Alemayehu S; Kim, Jaewook; Cheong, Sang-Wook; Hovden, Robert; Kourkoutis, Lena F

2018-02-13

Incommensurate charge order in hole-doped oxides is intertwined with exotic phenomena such as colossal magnetoresistance, high-temperature superconductivity, and electronic nematicity. Here, we map, at atomic resolution, the nature of incommensurate charge-lattice order in a manganite using scanning transmission electron microscopy at room temperature and cryogenic temperature ([Formula: see text]93 K). In diffraction, the ordering wave vector changes upon cooling, a behavior typically associated with incommensurate order. However, using real space measurements, we discover that the ordered state forms lattice-locked regions over a few wavelengths interspersed with phase defects and changing periodicity. The cations undergo picometer-scale ([Formula: see text]6 pm to 11 pm) transverse displacements, suggesting that charge-lattice coupling is strong. We further unearth phase inhomogeneity in the periodic lattice displacements at room temperature, and emergent phase coherence at 93 K. Such local phase variations govern the long-range correlations of the charge-ordered state and locally change the periodicity of the modulations, resulting in wave vector shifts in reciprocal space. These atomically resolved observations underscore the importance of lattice coupling and phase inhomogeneity, and provide a microscopic explanation for putative "incommensurate" order in hole-doped oxides. Copyright © 2018 the Author(s). Published by PNAS.

Correction of image drift and distortion in a scanning electron microscopy.

PubMed

Jin, P; Li, X

2015-12-01

Continuous research on small-scale mechanical structures and systems has attracted strong demand for ultrafine deformation and strain measurements. Conventional optical microscope cannot meet such requirements owing to its lower spatial resolution. Therefore, high-resolution scanning electron microscope has become the preferred system for high spatial resolution imaging and measurements. However, scanning electron microscope usually is contaminated by distortion and drift aberrations which cause serious errors to precise imaging and measurements of tiny structures. This paper develops a new method to correct drift and distortion aberrations of scanning electron microscope images, and evaluates the effect of correction by comparing corrected images with scanning electron microscope image of a standard sample. The drift correction is based on the interpolation scheme, where a series of images are captured at one location of the sample and perform image correlation between the first image and the consequent images to interpolate the drift-time relationship of scanning electron microscope images. The distortion correction employs the axial symmetry model of charged particle imaging theory to two images sharing with the same location of one object under different imaging fields of view. The difference apart from rigid displacement between the mentioned two images will give distortion parameters. Three-order precision is considered in the model and experiment shows that one pixel maximum correction is obtained for the employed high-resolution electron microscopic system. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

[Thirty years of the electron microscope investigation in zoology and parasitology in the Zoological Institute of the Russian Academy of Sciences].

PubMed

Shatrov, A B

2003-01-01

The history of the electron microscope investigations in zoology and parasitology in the Zoological Institute of the Russian Academy of Sciences and progress in scanning and transmission electron microscope investigations in this field of biology to the moment are briefly accounted.

75 FR 52928 - Emory University, et al., Notice of Consolidated Decision on Applications for Duty-Free Entry of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-30

... Consolidated Decision on Applications for Duty-Free Entry of Electron Microscopes This is a decision... 30322. Instrument: Electron Microscope. Manufacturer: JEOL, Ltd., Japan. Intended Use: See notice at 75... Department of Health, Menands, NY 12204-2719. Instrument: Electron Microscope. Manufacturer: JEOL Ltd., Japan...

Imaging of Norway spruce early somatic embryos with the ESEM, Cryo-SEM and laser scanning microscope.

PubMed

Neděla, Vilém; Hřib, Jiří; Havel, Ladislav; Hudec, Jiří; Runštuk, Jiří

2016-05-01

This article describes the surface structure of Norway spruce early somatic embryos (ESEs) as a typical culture with asynchronous development. The microstructure of extracellular matrix covering ESEs were observed using the environmental scanning electron microscope as a primary tool and using the scanning electron microscope with cryo attachment and laser electron microscope as a complementary tool allowing our results to be proven independently. The fresh samples were observed in conditions of the air environment of the environmental scanning electron microscope (ESEM) with the pressure from 550Pa to 690Pa and the low temperature of the sample from -18°C to -22°C. The samples were studied using two different types of detector to allow studying either the thin surface structure or material composition. The scanning electron microscope with cryo attachment was used for imaging frozen extracellular matrix microstructure with higher resolution. The combination of both electron microscopy methods was suitable for observation of "native" plant samples, allowing correct evaluation of our results, free of error and artifacts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Grayscale inhomogeneity correction method for multiple mosaicked electron microscope images

NASA Astrophysics Data System (ADS)

Zhou, Fangxu; Chen, Xi; Sun, Rong; Han, Hua

2018-04-01

Electron microscope image stitching is highly desired to acquire microscopic resolution images of large target scenes in neuroscience. However, the result of multiple Mosaicked electron microscope images may exist severe gray scale inhomogeneity due to the instability of the electron microscope system and registration errors, which degrade the visual effect of the mosaicked EM images and aggravate the difficulty of follow-up treatment, such as automatic object recognition. Consequently, the grayscale correction method for multiple mosaicked electron microscope images is indispensable in these areas. Different from most previous grayscale correction methods, this paper designs a grayscale correction process for multiple EM images which tackles the difficulty of the multiple images monochrome correction and achieves the consistency of grayscale in the overlap regions. We adjust overall grayscale of the mosaicked images with the location and grayscale information of manual selected seed images, and then fuse local overlap regions between adjacent images using Poisson image editing. Experimental result demonstrates the effectiveness of our proposed method.

Enhanced damage resistance and novel defect structure of CrFeCoNi under in situ electron irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Mo -Rigen; Wang, Shuai; Jin, Ke

Defect production and growth in CrFeCoNi, a single-phase concentrated solid solution alloy, is characterized using in situ electron irradiation inside a transmission electron microscope operated at 400–1250 kV and 400 °C. All observed defects are interstitial-type, either elliptical Frank loops or polygonal (mostly rhombus) perfect loops. Both forms of loops in CrFeCoNi exhibit a sublinear power law of growth that is > 40 times slower than the linear defect growth in pure Ni. Lastly, this result shows how compositional complexity impacts the production of Frenkel pairs and the agglomeration of interstitials into loops, and, thus, enhances the radiation tolerance.

Enhanced damage resistance and novel defect structure of CrFeCoNi under in situ electron irradiation

DOE PAGES

He, Mo -Rigen; Wang, Shuai; Jin, Ke; ...

2016-07-25

Defect production and growth in CrFeCoNi, a single-phase concentrated solid solution alloy, is characterized using in situ electron irradiation inside a transmission electron microscope operated at 400–1250 kV and 400 °C. All observed defects are interstitial-type, either elliptical Frank loops or polygonal (mostly rhombus) perfect loops. Both forms of loops in CrFeCoNi exhibit a sublinear power law of growth that is > 40 times slower than the linear defect growth in pure Ni. Lastly, this result shows how compositional complexity impacts the production of Frenkel pairs and the agglomeration of interstitials into loops, and, thus, enhances the radiation tolerance.

High-resolution, high-throughput imaging with a multibeam scanning electron microscope

PubMed Central

EBERLE, AL; MIKULA, S; SCHALEK, R; LICHTMAN, J; TATE, ML KNOTHE; ZEIDLER, D

2015-01-01

Electron–electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. Lay Description The composition of our world and our bodies on the very small scale has always fascinated people, making them search for ways to make this visible to the human eye. Where light microscopes reach their resolution limit at a certain magnification, electron microscopes can go beyond. But their capability of visualizing extremely small features comes at the cost of a very small field of view. Some of the questions researchers seek to answer today deal with the ultrafine structure of brains, bones or computer chips. Capturing these objects with electron microscopes takes a lot of time – maybe even exceeding the time span of a human being – or new tools that do the job much faster. A new type of scanning electron microscope scans with 61 electron beams in parallel, acquiring 61 adjacent images of the sample at the same time a conventional scanning electron microscope captures one of these images. In principle, the multibeam scanning electron microscope’s field of view is 61 times larger and therefore coverage of the sample surface can be accomplished in less time. This enables researchers to think about large-scale projects, for example in the rather new field of connectomics. A very good introduction to imaging a brain at nanometre resolution can be found within course material from Harvard University on http://www.mcb80x.org/# as featured media entitled ‘connectomics’. PMID:25627873

Investigation of the Microstructure and Mechanical Properties of Copper-Graphite Composites Reinforced with Single-Crystal α-Al₂O₃ Fibres by Hot Isostatic Pressing.

PubMed

Zhang, Guihang; Jiang, Xiaosong; Qiao, ChangJun; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao; Valcarcel, Victor

2018-06-11

Single-crystal α-Al₂O₃ fibres can be utilized as a novel reinforcement in high-temperature composites owing to their high elastic modulus, chemical and thermal stability. Unlike non-oxide fibres and polycrystalline alumina fibres, high-temperature oxidation and polycrystalline particles boundary growth will not occur for single-crystal α-Al₂O₃ fibres. In this work, single-crystal α-Al₂O₃ whiskers and Al₂O₃ particles synergistic reinforced copper-graphite composites were fabricated by mechanical alloying and hot isostatic pressing techniques. The phase compositions, microstructures, and fracture morphologies of the composites were investigated using X-ray diffraction, a scanning electron microscope equipped with an X-ray energy-dispersive spectrometer (EDS), an electron probe microscopic analysis equipped with wavelength-dispersive spectrometer, and a transmission electron microscope equipped with EDS. The mechanical properties have been measured by a micro-hardness tester and electronic universal testing machine. The results show that the reinforcements were unevenly distributed in the matrix with the increase of their content and there were some micro-cracks located at the interface between the reinforcement and the matrix. With the increase of the Al₂O₃ whisker content, the compressive strength of the composites first increased and then decreased, while the hardness decreased. The fracture and strengthening mechanisms of the composite materials were explored on the basis of the structure and composition of the composites through the formation and function of the interface. The main strengthening mechanism in the composites was fine grain strengthening and solid solution strengthening. The fracture type of the composites was brittle fracture.

Investigation on microstructure and mechanical properties on pulsed current gas tungsten arc welded super alloy 617

NASA Astrophysics Data System (ADS)

Mageshkumar, K.; Kuppan, P.; Arivazhagan, N.

2017-11-01

The present research work investigates the metallurgical and mechanical properties of weld joint fabricated by alloy 617 by pulsed current gas tungsten arc welding (PCGTAW) technique. Welding was done by ERNiCrCoMo-1 filler wire. Optical and Scanning Electron Microscope (SEM) revealed the fine equiaxed dendritic in the fusion zone. Electron Dispersive Spectroscopy (EDS) demonstrates the presence of Mo-rich secondary phases in the grain boundary regions. Tensile test shows improved mechanical properties compared to the continuous current mode. Bend test didn’t indicate the presence of defects in the weldments.

Analysis of improvement in performance and design parameters for enhancing resolution in an atmospheric scanning electron microscope.

PubMed

Yoon, Yeo Hun; Kim, Seung Jae; Kim, Dong Hwan

2015-12-01

The scanning electron microscope is used in various fields to go beyond diffraction limits of the optical microscope. However, the electron pathway should be conducted in a vacuum so as not to scatter electrons. The pretreatment of the sample is needed for use in the vacuum. To directly observe large and fully hydrophilic samples without pretreatment, the atmospheric scanning electron microscope (ASEM) is needed. We developed an electron filter unit and an electron detector unit for implementation of the ASEM. The key of the electron filter unit is that electrons are transmitted while air molecules remain untransmitted through the unit. The electron detector unit collected the backscattered electrons. We conducted experiments using the selected materials with Havar foil, carbon film and SiN film. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Infrared nanoscopy down to liquid helium temperatures

NASA Astrophysics Data System (ADS)

Lang, Denny; Döring, Jonathan; Nörenberg, Tobias; Butykai, Ádám; Kézsmárki, István; Schneider, Harald; Winnerl, Stephan; Helm, Manfred; Kehr, Susanne C.; Eng, Lukas M.

2018-03-01

We introduce a scattering-type scanning near-field infrared microscope (s-SNIM) for the local scale near-field sample analysis and spectroscopy from room temperature down to liquid helium (LHe) temperature. The extension of s-SNIM down to T = 5 K is in particular crucial for low-temperature phase transitions, e.g., for the examination of superconductors, as well as low energy excitations. The low temperature (LT) s-SNIM performance is tested with CO2-IR excitation at T = 7 K using a bare Au reference and a structured Si/SiO2-sample. Furthermore, we quantify the impact of local laser heating under the s-SNIM tip apex by monitoring the light-induced ferroelectric-to-paraelectric phase transition of the skyrmion-hosting multiferroic material GaV4S8 at Tc = 42 K. We apply LT s-SNIM to study the spectral response of GaV4S8 and its lateral domain structure in the ferroelectric phase by the mid-IR to THz free-electron laser-light source FELBE at the Helmholtz-Zentrum Dresden-Rossendorf, Germany. Notably, our s-SNIM is based on a non-contact atomic force microscope (AFM) and thus can be complemented in situ by various other AFM techniques, such as topography profiling, piezo-response force microscopy (PFM), and/or Kelvin-probe force microscopy (KPFM). The combination of these methods supports the comprehensive study of the mutual interplay in the topographic, electronic, and optical properties of surfaces from room temperature down to 5 K.

Dimensionality tuning of the electronic structure in Fe3Ga4 magnetic materials

NASA Astrophysics Data System (ADS)

Moura, K. O.; de Oliveira, L. A. S.; Rosa, P. F. S.; Jesus, C. B. R.; Saleta, M. E.; Granado, E.; Béron, F.; Pagliuso, P. G.; Pirota, K. R.

2016-06-01

This work reports on the dimensionality effects on the magnetic behavior of Fe3Ga4 compounds by means of magnetic susceptibility, electrical resistivity, and specific heat measurements. Our results show that reducing the Fe3Ga4 dimensionality, via nanowire shape, intriguingly modifies its electronic structure. In particular, the bulk system exhibits two transitions, a ferromagnetic (FM) transition temperature at T1 = 50 K and an antiferromagnetic (AFM) one at T2 = 390 K. On the other hand, nanowires shift these transition temperatures, towards higher and lower temperature for T1 and T2, respectively. Moreover, the dimensionality reduction seems to also modify the microscopic nature of the T1 transition. Instead of a FM to AFM transition, as observed in the 3D system, a transition from FM to ferrimagnetic (FERRI) or to coexistence of FM and AFM phases is found for the nanowires. Our results allowed us to propose the magnetic field-temperature phase diagram for Fe3Ga4 in both bulk and nanostructured forms. The interesting microscopic tuning of the magnetic interactions induced by dimensionality in Fe3Ga4 opens a new route to optimize the use of such materials in nanostructured devices.

Driving the photoluminescent and structural properties of X2-Y2SiO5 by varying the dopant Dy3+ concentration towards cool WLED applications

NASA Astrophysics Data System (ADS)

Ramakrishna, G.; Nagabhushana, H.; Hareesh, K.; Sunitha, D. V.

2017-07-01

Dy3+ doped Y2SiO5 nanophosphors were synthesized by solution combustion technique using Calotropis gigantean milk latex and NaCl as fuel and flux respectively. Powder X-ray diffraction (PXRD) confirmed the formation of monoclinic X2-phase Y2SiO5 belonging to the phase group C2/c. Fourier transform infrared spectroscopy (FTIR) shows characteristic metal-oxygen (Y-O) vibration band at 721 cm-1. Transmission electron microscopic (TEM) and Scanning electron microscopic (SEM) morphological feature exhibits non-uniform almost spherical shaped nanosized particles. The photoluminescence (PL) emission peaks, recorded at 388 nm, showed radiative emissions at 483, 575 and 636 nm respectively. Judd-Ofelt (JO) analysis was carried out to estimate the radiative (AR) properties, radiative life time (τR), branching ratio (βR) and stimulated emission crossection (σλp). The CIE and CCT was estimated using McCamy empirical formula. In the beginning, the CIE co-ordinate values were lying in the light blue region. However, with increase in Dy3+ concentration the values shifted towards white region. CCT value was found to be ∼6984 K. Therefore, Y2SiO5:Dy3+ (9 mol%) can be used for cool day light and WLED applications.

Dimensionality tuning of the electronic structure in Fe3Ga4 magnetic materials

PubMed Central

Moura, K. O.; de Oliveira, L. A. S.; Rosa, P. F. S.; Jesus, C. B. R.; Saleta, M. E.; Granado, E.; Béron, F.; Pagliuso, P. G.; Pirota, K. R.

2016-01-01

This work reports on the dimensionality effects on the magnetic behavior of Fe3Ga4 compounds by means of magnetic susceptibility, electrical resistivity, and specific heat measurements. Our results show that reducing the Fe3Ga4 dimensionality, via nanowire shape, intriguingly modifies its electronic structure. In particular, the bulk system exhibits two transitions, a ferromagnetic (FM) transition temperature at T1 = 50 K and an antiferromagnetic (AFM) one at T2 = 390 K. On the other hand, nanowires shift these transition temperatures, towards higher and lower temperature for T1 and T2, respectively. Moreover, the dimensionality reduction seems to also modify the microscopic nature of the T1 transition. Instead of a FM to AFM transition, as observed in the 3D system, a transition from FM to ferrimagnetic (FERRI) or to coexistence of FM and AFM phases is found for the nanowires. Our results allowed us to propose the magnetic field-temperature phase diagram for Fe3Ga4 in both bulk and nanostructured forms. The interesting microscopic tuning of the magnetic interactions induced by dimensionality in Fe3Ga4 opens a new route to optimize the use of such materials in nanostructured devices. PMID:27329581

Scanning and transmission electron microscope of suspended lead-rich particles in the air of San Luis Potosi, Mexico

NASA Astrophysics Data System (ADS)

Piña, A. Aragón; Villaseñor, G. Torres; Jacinto, P. Santiago; Fernández, M. Monroy

In the city of San Luis Potosi exists an important metallurgical plant and is known that in the adjacent urban zone, there is a high concentration of lead in the air, it is also supposed that most of the particles with lead have an anthropogenic origin because these particles show morphological characteristics and chemical composition very different in comparison with common lead minerals. In this work it was proved that most of the airborne particles with lead present in this urban zone, effectively came from the copper smelter. The airborne particles with lead were compared with particles with lead obtained starting from samples of slag and lead calcine of the copper smelter. To perform the comparative study, these particles were studied with energy dispersive X-ray microanalysis (EDS) in conjunction with scanning electron microscope to obtain chemical composition and associated morphological characteristics. Results suggest that these particles, composed of only one phase, are chemically distinct from any crustal lead mineral. Because of the complexity of the chemical composition of these particles (Pb, S, Cu, As, Fe, Zn, Cd, Sb, O), some of the airborne particles were analyzed by transmission microscopy in order to associate crystalline structure with any particular chemical phase.

Theoretical determination of hydrodynamic window in monolayer and bilayer graphene from scattering rates

NASA Astrophysics Data System (ADS)

Ho, Derek Y. H.; Yudhistira, Indra; Chakraborty, Nilotpal; Adam, Shaffique

2018-03-01

Electrons behave like a classical fluid with a momentum distribution function that varies slowly in space and time when the quantum-mechanical carrier-carrier scattering dominates over all other scattering processes. Recent experiments in monolayer and bilayer graphene have reported signatures of such hydrodynamic electron behavior in ultraclean devices. In this theoretical work, starting from a microscopic treatment of electron-electron, electron-phonon, and electron-impurity interactions within the random phase approximation, we demonstrate that monolayer and bilayer graphene both host two different hydrodynamic regimes. We predict that the hydrodynamic window in bilayer graphene is stronger than in monolayer graphene, and has a characteristic "v shape" as opposed to a "lung shape." Finally, we collapse experimental data onto a universal disorder-limited theory, demonstrating that the observed violation of the Wiedemann-Franz law in monolayers occurs in a regime dominated by impurity-induced electron-hole puddles.

Controlling electron beam-induced structure modifications and cation exchange in cadmium sulfide-copper sulfide heterostructured nanorods.

PubMed

Zheng, Haimei; Sadtler, Bryce; Habenicht, Carsten; Freitag, Bert; Alivisatos, A Paul; Kisielowski, Christian

2013-11-01

The atomic structure and interfaces of CdS/Cu2S heterostructured nanorods are investigated with the aberration-corrected TEAM 0.5 electron microscope operated at 80 kV and 300 kV applying in-line holography and complementary techniques. Cu2S exhibits a low-chalcocite structure in pristine CdS/Cu2S nanorods. Under electron beam irradiation the Cu2S phase transforms into a high-chalcocite phase while the CdS phase maintains its wurtzite structure. Time-resolved experiments reveal that Cu(+)-Cd(2+) cation exchange at the CdS/Cu2S interfaces is stimulated by the electron beam and proceeds within an undisturbed and coherent sulfur sub-lattice. A variation of the electron beam current provides an efficient way to control and exploit such irreversible solid-state chemical processes that provide unique information about system dynamics at the atomic scale. Specifically, we show that the electron beam-induced copper-cadmium exchange is site specific and anisotropic. A resulting displacement of the CdS/Cu2S interfaces caused by beam-induced cation interdiffusion equals within a factor of 3-10 previously reported Cu diffusion length measurements in heterostructured CdS/Cu2S thin film solar cells with an activation energy of 0.96 eV. © 2013 Elsevier B.V. All rights reserved.

Size determination of Acipenser ruthenus spermatozoa in different types of electron microscopy.

PubMed

Psenicka, Martin; Tesarová, Martina; Tesitel, Jakub; Nebesárová, Jana

2010-07-01

In this study three types of scanning electron microscopes were used for the size determination of spermatozoa of sterlet Acipenser ruthenus - high vacuum scanning electron microscope (SEM, JEOL 6300), environmental scanning electron microscope (ESEM, Quanta 200 FEG), field emission scanning electron microscope (FESEM, JEOL 7401F) with cryoattachment Alto 2500 (Gatan) and transmission electron microscope (TEM, JEOL 1010). The use of particular microscopes was tied with different specimen preparation techniques. The aim of this study was to evaluate to what degree the type of used electron microscope can influence the size of different parts of spermatozoa. For high vacuum SEM the specimen was prepared using two slightly different procedures. After chemical fixation with 2.5% glutaraldehyde in 0.1M phosphate buffer and post-fixation by 1% osmium tetroxide, the specimen was dehydrated by acetone series and dried either by critical point method or by means of t-butylalcohol. For ESEM fresh, unfixed material was used, which was dropped on microscopic copper grids. In FESEM working in cryo-mode the specimen was observed in a frozen state. Ultrathin sections from chemically fixed and Epon embedded specimens were prepared for TEM observation. Distinct parts of sterlet spermatozoa were measured in each microscope and the data obtained was statistically processed. Results confirmed that the classical chemical procedure of specimen preparation for SEM including critical point drying method led to a significant contraction of all measured values, which could deviate up to 30% in comparison with values measured on the fresh chemically untreated specimen in ESEM. Surprisingly sperm dimensions determinated on ultrathin sections by TEM are comparable with values obtained in ESEM or FESEM. Copyright 2010 Elsevier Ltd. All rights reserved.

Crystalline phase transformation of colloidal cadmium sulfide nanocrystals

NASA Astrophysics Data System (ADS)

Ghali, M.; Eissa, A. M.; Mosaad, M. M.

2017-03-01

In this paper, we give a microscopic view concerning influence of the growth conditions on the physical properties of nanocrystals (NCs) thin films made of CdS, prepared using chemical bath deposition CBD technique. We show a crystalline phase transformation of CdS NCs from hexagonal wurtzite (W) structure to cubic zincblende (ZB) when the growth conditions change, particularly the solution pH values. This effect was confirmed using X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) measurements. The optical absorption spectra allow calculation of the bandgap value, Eg, where significant increase ˜200 meV in the CdS bandgap when transforming from Hexagonal to Cubic phase was found.

Nanoscale Characterization of Elemental Partitioning Between Gamma and Gamma Prime Phases in Rene 88DT Nickel Base Superalloy (Preprint)

DTIC Science & Technology

2008-02-01

penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN...analysis "as condu,ted on a FEI Tecnai F20 field emission gun transmission electron microscope operaling at 200 KV. Imagcs were obtained using lhe Cr M...line marked AI3 in (a). The neck region exhibil’ an inlensity lying in t>etween lhal of lhe yand y’phases. (c) Inlensily prot1le aemS > lhe line CD in (a

A scanning electron microscope study of olivine crystal surfaces

NASA Technical Reports Server (NTRS)

Olsen, E. J.; Grossman, L.

1974-01-01

SEM photographs were taken of euhedral olivine grains from the Murchison C2 chondrite and several terrestrial and lunar occurrences. In general, the crystal faces of the meteorite grains are rough and uneven, with irregular growth patterns. They are very similar to crystal faces on terrestrial olivine grains that formed by sublimation from a vapor phase. They are very different from the relatively smooth and featureless surfaces of magmatic olivine crystals that precipitated from igneous melts. Qualitatively, the surface morphology of the crystal supports the contention that many euhedral crystals of olivine in C2 meteorites condensed from a gas phase.

Microscopic study of thermoelectric In-doped SnTe

NASA Astrophysics Data System (ADS)

Nan, Pengfei; Liu, Ruibin; Chang, Yunjie; Wu, Hongbo; Wang, Yumei; Yu, Richeng; Shen, Jun; Guo, Wei; Ge, Binghui

2018-06-01

SnTe is a p-type thermoelectric material that is isostructural with PbTe, for which it is a potential environmentally friendly replacement. By doping the SnTe lattice with In, the thermal conductivity of SnTe can be significantly reduced and the thermoelectric conversion efficiency improved. A large number of precipitates were present in the In-doped SnTe samples; based on atomic-resolution high-angle annular dark-field images and electron energy loss spectra, these precipitates were identified as the zinc-blende phase of In2Te3. Through geometry phase analysis, a new phonon scattering mechanism is discussed.

Binary pseudo-random patterned structures for modulation transfer function calibration and resolution characterization of a full-field transmission soft x-ray microscope

DOE PAGES

Yashchuk, V. V.; Fischer, P. J.; Chan, E. R.; ...

2015-12-09

We present a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) one-dimensional sequences and two-dimensional arrays as an effective method for spectral characterization in the spatial frequency domain of a broad variety of metrology instrumentation, including interferometric microscopes, scatterometers, phase shifting Fizeau interferometers, scanning and transmission electron microscopes, and at this time, x-ray microscopes. The inherent power spectral density of BPR gratings and arrays, which has a deterministic white-noise-like character, allows a direct determination of the MTF with a uniform sensitivity over the entire spatial frequency range and field of view of an instrument. We demonstrate themore » MTF calibration and resolution characterization over the full field of a transmission soft x-ray microscope using a BPR multilayer (ML) test sample with 2.8 nm fundamental layer thickness. We show that beyond providing a direct measurement of the microscope's MTF, tests with the BPRML sample can be used to fine tune the instrument's focal distance. Finally, our results confirm the universality of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.« less

The Effect of Boron and Zirconium on the Structure and Tensile Properties of the Cast Nickel-Based Superalloy ATI 718Plus

NASA Astrophysics Data System (ADS)

Hosseini, Seyed Ali; Abbasi, Seyed Mehdi; Madar, Karim Zangeneh

2018-04-01

The effects of boron and zirconium on cast structure, hardness, and tensile properties of the nickel-based superalloy 718Plus were investigated. For this purpose, five alloys with different contents of boron and zirconium were cast via vacuum induction melting and then purified via vacuum arc remelting. Microstructural analysis by light-optical microscope and scanning electron microscope equipped with energy-dispersive x-ray spectroscopy and phase studies by x-ray diffraction analysis were performed. The results showed that boron and zirconium tend to significantly reduce dendritic arm spacing and increase the amount of Laves, Laves/gamma eutectic, and carbide phases. It was also found that boron led to the formation of B4C and (Cr, Fe, Mo, Ni, Ti)3B2 phases and zirconium led to the formation of intermetallic phases and ZrC carbide. In the presence of boron and zirconium, the hardness and its difference between dendritic branches and inter-dendritic spaces increased by concentrating such phases as Laves in the inter-dendritic spaces. These elements had a negative effect on tensile properties of the alloy, including ductility and strength, mainly because of the increase in the Laves phase. It should be noted that the largest degradation of the tensile properties occurred in the alloys containing the maximum amount of zirconium.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yashchuk, V. V.; Fischer, P. J.; Chan, E. R.

We present a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) one-dimensional sequences and two-dimensional arrays as an effective method for spectral characterization in the spatial frequency domain of a broad variety of metrology instrumentation, including interferometric microscopes, scatterometers, phase shifting Fizeau interferometers, scanning and transmission electron microscopes, and at this time, x-ray microscopes. The inherent power spectral density of BPR gratings and arrays, which has a deterministic white-noise-like character, allows a direct determination of the MTF with a uniform sensitivity over the entire spatial frequency range and field of view of an instrument. We demonstrate themore » MTF calibration and resolution characterization over the full field of a transmission soft x-ray microscope using a BPR multilayer (ML) test sample with 2.8 nm fundamental layer thickness. We show that beyond providing a direct measurement of the microscope's MTF, tests with the BPRML sample can be used to fine tune the instrument's focal distance. Finally, our results confirm the universality of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.« less

Reprint of: Atmospheric scanning electron microscope observes cells and tissues in open medium through silicon nitride film.

PubMed

Nishiyama, Hidetoshi; Suga, Mitsuo; Ogura, Toshihiko; Maruyama, Yuusuke; Koizumi, Mitsuru; Mio, Kazuhiro; Kitamura, Shinichi; Sato, Chikara

2010-11-01

Direct observation of subcellular structures and their characterization is essential for understanding their physiological functions. To observe them in open environment, we have developed an inverted scanning electron microscope with a detachable, open-culture dish, capable of 8 nm resolution, and combined with a fluorescence microscope quasi-simultaneously observing the same area from the top. For scanning electron microscopy from the bottom, a silicon nitride film window in the base of the dish maintains a vacuum between electron gun and open sample dish while allowing electrons to pass through. Electrons are backscattered from the sample and captured by a detector under the dish. Cells cultured on the open dish can be externally manipulated under optical microscopy, fixed, and observed using scanning electron microscopy. Once fine structures have been revealed by scanning electron microscopy, their component proteins may be identified by comparison with separately prepared fluorescence-labeled optical microscopic images of the candidate proteins, with their heavy-metal-labeled or stained ASEM images. Furthermore, cell nuclei in a tissue block stained with platinum-blue were successfully observed without thin-sectioning, which suggests the applicability of this inverted scanning electron microscope to cancer diagnosis. This microscope visualizes mesoscopic-scale structures, and is also applicable to non-bioscience fields including polymer chemistry. Copyright © 2010 Elsevier Inc. All rights reserved.

An electron microscope for the aberration-corrected era.

PubMed

Krivanek, O L; Corbin, G J; Dellby, N; Elston, B F; Keyse, R J; Murfitt, M F; Own, C S; Szilagyi, Z S; Woodruff, J W

2008-02-01

Improved resolution made possible by aberration correction has greatly increased the demands on the performance of all parts of high-end electron microscopes. In order to meet these demands, we have designed and built an entirely new scanning transmission electron microscope (STEM). The microscope includes a flexible illumination system that allows the properties of its probe to be changed on-the-fly, a third-generation aberration corrector which corrects all geometric aberrations up to fifth order, an ultra-responsive yet stable five-axis sample stage, and a flexible configuration of optimized detectors. The microscope features many innovations, such as a modular column assembled from building blocks that can be stacked in almost any order, in situ storage and cleaning facilities for up to five samples, computer-controlled loading of samples into the column, and self-diagnosing electronics. The microscope construction is described, and examples of its capabilities are shown.

Modern Material Analysis Instruments Add a New Dimension to Materials Characterization and Failure Analysis

NASA Technical Reports Server (NTRS)

Panda, Binayak

2009-01-01

Modern analytical tools can yield invaluable results during materials characterization and failure analysis. Scanning electron microscopes (SEMs) provide significant analytical capabilities, including angstrom-level resolution. These systems can be equipped with a silicon drift detector (SDD) for very fast yet precise analytical mapping of phases, as well as electron back-scattered diffraction (EBSD) units to map grain orientations, chambers that admit large samples, variable pressure for wet samples, and quantitative analysis software to examine phases. Advanced solid-state electronics have also improved surface and bulk analysis instruments: Secondary ion mass spectroscopy (SIMS) can quantitatively determine and map light elements such as hydrogen, lithium, and boron - with their isotopes. Its high sensitivity detects impurities at parts per billion (ppb) levels. X-ray photo-electron spectroscopy (XPS) can determine oxidation states of elements, as well as identifying polymers and measuring film thicknesses on coated composites. This technique is also known as electron spectroscopy for chemical analysis (ESCA). Scanning Auger electron spectroscopy (SAM) combines surface sensitivity, spatial lateral resolution (10 nm), and depth profiling capabilities to describe elemental compositions of near and below surface regions down to the chemical state of an atom.

Hartmann characterization of the PEEM-3 aberration-corrected X-ray photoemission electron microscope.

PubMed

Scholl, A; Marcus, M A; Doran, A; Nasiatka, J R; Young, A T; MacDowell, A A; Streubel, R; Kent, N; Feng, J; Wan, W; Padmore, H A

2018-05-01

Aberration correction by an electron mirror dramatically improves the spatial resolution and transmission of photoemission electron microscopes. We will review the performance of the recently installed aberration corrector of the X-ray Photoemission Electron Microscope PEEM-3 and show a large improvement in the efficiency of the electron optics. Hartmann testing is introduced as a quantitative method to measure the geometrical aberrations of a cathode lens electron microscope. We find that aberration correction leads to an order of magnitude reduction of the spherical aberrations, suggesting that a spatial resolution of below 100 nm is possible at 100% transmission of the optics when using x-rays. We demonstrate this improved performance by imaging test patterns employing element and magnetic contrast. Published by Elsevier B.V.

A new apparatus for electron tomography in the scanning electron microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morandi, V., E-mail: morandi@bo.imm.cnr.it; Maccagnani, P.; Masini, L.

2015-06-23

The three-dimensional reconstruction of a microscopic specimen has been obtained by applying the tomographic algorithm to a set of images acquired in a Scanning Electron Microscope. This result was achieved starting from a series of projections obtained by stepwise rotating the sample under the beam raster. The Scanning Electron Microscope was operated in the scanning-transmission imaging mode, where the intensity of the transmitted electron beam is a monotonic function of the local mass-density and thickness of the specimen. The detection strategy has been implemented and tailored in order to maintain the projection requirement over the large tilt range, as requiredmore » by the tomographic workflow. A Si-based electron detector and an eucentric-rotation specimen holder have been specifically developed for the purpose.« less

ultraLM and miniLM: Locator tools for smart tracking of fluorescent cells in correlative light and electron microscopy.

PubMed

Brama, Elisabeth; Peddie, Christopher J; Wilkes, Gary; Gu, Yan; Collinson, Lucy M; Jones, Martin L

2016-12-13

In-resin fluorescence (IRF) protocols preserve fluorescent proteins in resin-embedded cells and tissues for correlative light and electron microscopy, aiding interpretation of macromolecular function within the complex cellular landscape. Dual-contrast IRF samples can be imaged in separate fluorescence and electron microscopes, or in dual-modality integrated microscopes for high resolution correlation of fluorophore to organelle. IRF samples also offer a unique opportunity to automate correlative imaging workflows. Here we present two new locator tools for finding and following fluorescent cells in IRF blocks, enabling future automation of correlative imaging. The ultraLM is a fluorescence microscope that integrates with an ultramicrotome, which enables 'smart collection' of ultrathin sections containing fluorescent cells or tissues for subsequent transmission electron microscopy or array tomography. The miniLM is a fluorescence microscope that integrates with serial block face scanning electron microscopes, which enables 'smart tracking' of fluorescent structures during automated serial electron image acquisition from large cell and tissue volumes.

Spherical aberration correction in a scanning transmission electron microscope using a sculpted thin film.

PubMed

Shiloh, Roy; Remez, Roei; Lu, Peng-Han; Jin, Lei; Lereah, Yossi; Tavabi, Amir H; Dunin-Borkowski, Rafal E; Arie, Ady

2018-06-01

Nearly eighty years ago, Scherzer showed that rotationally symmetric, charge-free, static electron lenses are limited by an unavoidable, positive spherical aberration. Following a long struggle, a major breakthrough in the spatial resolution of electron microscopes was reached two decades ago by abandoning the first of these conditions, with the successful development of multipole aberration correctors. Here, we use a refractive silicon nitride thin film to tackle the second of Scherzer's constraints and demonstrate an alternative method for correcting spherical aberration in a scanning transmission electron microscope. We reveal features in Si and Cu samples that cannot be resolved in an uncorrected microscope. Our thin film corrector can be implemented as an immediate low cost upgrade to existing electron microscopes without re-engineering of the electron column or complicated operation protocols and can be extended to the correction of additional aberrations. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Scanning ultrafast electron microscopy

PubMed Central

Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

2010-01-01

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

Smartphone based hand-held quantitative phase microscope using the transport of intensity equation method.

PubMed

Meng, Xin; Huang, Huachuan; Yan, Keding; Tian, Xiaolin; Yu, Wei; Cui, Haoyang; Kong, Yan; Xue, Liang; Liu, Cheng; Wang, Shouyu

2016-12-20

In order to realize high contrast imaging with portable devices for potential mobile healthcare, we demonstrate a hand-held smartphone based quantitative phase microscope using the transport of intensity equation method. With a cost-effective illumination source and compact microscope system, multi-focal images of samples can be captured by the smartphone's camera via manual focusing. Phase retrieval is performed using a self-developed Android application, which calculates sample phases from multi-plane intensities via solving the Poisson equation. We test the portable microscope using a random phase plate with known phases, and to further demonstrate its performance, a red blood cell smear, a Pap smear and monocot root and broad bean epidermis sections are also successfully imaged. Considering its advantages as an accurate, high-contrast, cost-effective and field-portable device, the smartphone based hand-held quantitative phase microscope is a promising tool which can be adopted in the future in remote healthcare and medical diagnosis.

Mineralogy, textures and mode of formation of a hibonite-bearing Allende inclusion

NASA Technical Reports Server (NTRS)

Allen, J. M.; Grossman, L.; Davis, A. M.; Hutcheon, I. D.

1978-01-01

The origin of a Type A, hibonite-rich, coarse-grained inclusion is investigated with the electron microprobe and petrographic and scanning electron microscopes. The primary phases are hibonite, rhonite, Ti-Al-pyroxene, spinel, perovskite and melilite. Evidence for the crystallization of the bulk of the primary phases, hibonite and melilite, from a melt is lacking, suggesting that they may have condensed directly from a solar nebular gas instead. Primary phases were intensely altered during a later condensation event which deposited grossular, anorthite, nepheline and wollastonite in veins and cavities. Four or five condensate rims were deposited as successive layers on the outside of the inclusion. From inside to outside, they consist of perovskite + spinel, nepheline + anorthite, Ti-Al-pyroxene + diopside, hedenbergite + or - wollastonite + or - andradite and, finally, prisms of diopside and hedenbergite with wollastonite and andradite. Reverse zoning in melilite; alteration phases and rim phases, which are not stable condensates from a gas of solar composition; and details of the sequence of rim condensates all suggest that the entire condensation history of this inclusion was interrupted by changes in pressure and/or temperature and/or gas phase composition.

Study on stabilities, thermophysical properties and natural convective heat transfer characteristics of TiO2-water nanofluids

NASA Astrophysics Data System (ADS)

Qi, Cong; Wan, Yong Liang; Wang, Gui Qing; Han, Dong Tai

2018-04-01

TiO2-water nanofluids with different mass fractions ( ω = 0.1 wt%, ω = 0.3 wt% and ω = 0.5 wt%) are prepared respectively, and the stabilities are studied by scanning electron microscope, transmission electron microscope, dynamic analysis method and settlement observation method. Additionally, thermophysical properties of nanofluids are discussed, and models of thermophysical properties are deduced. Then, an experimental installation and a two-phase lattice Boltzmann model for natural convection heat transfer are established in this paper and the effects of cavity ratio, heating power and nanoparticle mass fraction on heat transfer are discussed respectively. It can be obtained that the thermal conductivities of TiO2-water nanofluids can be improved by 5.23% to the utmost extent. However, the heat transfer can be enhanced by 34.2% in the maximum with the increase of nanoparticle mass fraction at the lowest heating power and the largest cavity ratio.

Flocking from a quantum analogy: spin-orbit coupling in an active fluid

NASA Astrophysics Data System (ADS)

Loewe, Benjamin; Souslov, Anton; Goldbart, Paul M.

2018-01-01

Systems composed of strongly interacting self-propelled particles can form a spontaneously flowing polar active fluid. The study of the connection between the microscopic dynamics of a single such particle and the macroscopic dynamics of the fluid can yield insights into experimentally realizable active flows, but this connection is well understood in only a few select cases. We introduce a model of self-propelled particles based on an analogy with the motion of electrons that have strong spin-orbit coupling. We find that, within our model, self-propelled particles are subject to an analog of the Heisenberg uncertainty principle that relates translational and rotational noise. Furthermore, by coarse-graining this microscopic model, we establish expressions for the coefficients of the Toner-Tu equations—the hydrodynamic equations that describe an active fluid composed of these ‘active spins.’ The connection between stochastic self-propelled particles and quantum particles with spin may help realize exotic phases of matter using active fluids via analogies with systems composed of strongly correlated electrons.

Photocatalytic degradation of methyl orange and bromophenol blue dyes in water using sol-gel synthesized TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Dhanalakshmi, J.; Pathinettam Padiyan, D.

2017-09-01

TiO2 nanoparticles were prepared by a sol-gel method using titanium tetra isopropoxide as a precursor. The structural, optical, morphological and electrical properties were studied by x-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), a high resolution scanning electron microscope (HR-SEM), a transmission electron microscope (TEM), Raman analysis, Photoluminescence (PL) and impedance spectroscopy. The XRD and Raman spectra revealed that the synthesized samples are in pure anatase phase with an average crystallite size of 18 nm. Photocatalytic activity of the TiO2 nanoparticles was investigated for the degradation of 10 ppm methyl orange (MO) and bromophenol blue (BPB) dye using 10 mg of catalyst. Anatase TiO2 exhibited the removal of 67.12% and 85.51% of MO and BPB, respectively, within 240 min. The photocatalytic degradation process is explained using pseudo second order kinetics and fits well with the higher correlation coefficient.

Manipulation of a Nuclear Spin by a Magnetic Domain Wall in a Quantum Hall Ferromagnet.

PubMed

Korkusinski, M; Hawrylak, P; Liu, H W; Hirayama, Y

2017-03-06

The manipulation of a nuclear spin by an electron spin requires the energy to flip the electron spin to be vanishingly small. This can be realized in a many electron system with degenerate ground states of opposite spin polarization in different Landau levels. We present here a microscopic theory of a domain wall between spin unpolarized and spin polarized quantum Hall ferromagnet states at filling factor two with the Zeeman energy comparable to the cyclotron energy. We determine the energies and many-body wave functions of the electronic quantum Hall droplet with up to N = 80 electrons as a function of the total spin, angular momentum, cyclotron and Zeeman energies from the spin singlet ν = 2 phase, through an intermediate polarization state exhibiting a domain wall to the fully spin-polarized phase involving the lowest and the second Landau levels. We demonstrate that the energy needed to flip one electron spin in a domain wall becomes comparable to the energy needed to flip the nuclear spin. The orthogonality of orbital electronic states is overcome by the many-electron character of the domain - the movement of the domain wall relative to the position of the nuclear spin enables the manipulation of the nuclear spin by electrical means.

Manipulation of a Nuclear Spin by a Magnetic Domain Wall in a Quantum Hall Ferromagnet

PubMed Central

Korkusinski, M.; Hawrylak, P.; Liu, H. W.; Hirayama, Y.

2017-01-01

The manipulation of a nuclear spin by an electron spin requires the energy to flip the electron spin to be vanishingly small. This can be realized in a many electron system with degenerate ground states of opposite spin polarization in different Landau levels. We present here a microscopic theory of a domain wall between spin unpolarized and spin polarized quantum Hall ferromagnet states at filling factor two with the Zeeman energy comparable to the cyclotron energy. We determine the energies and many-body wave functions of the electronic quantum Hall droplet with up to N = 80 electrons as a function of the total spin, angular momentum, cyclotron and Zeeman energies from the spin singlet ν = 2 phase, through an intermediate polarization state exhibiting a domain wall to the fully spin-polarized phase involving the lowest and the second Landau levels. We demonstrate that the energy needed to flip one electron spin in a domain wall becomes comparable to the energy needed to flip the nuclear spin. The orthogonality of orbital electronic states is overcome by the many-electron character of the domain - the movement of the domain wall relative to the position of the nuclear spin enables the manipulation of the nuclear spin by electrical means. PMID:28262758

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varlamov, A. A.; Galda, A.; Glatz, A.

Superconducting (SC) fluctuations, discovered in the late 1960s, have constituted an important research area in superconductivity as they are manifest in a variety of phenomena. Indeed, the underlying physics of SC fluctuations makes it possible to elucidate the fundamental properties of the superconducting state. The interest in SC fluctuation phenomena was further enhanced with the discovery of cuprate high-temperature superconductors (HTSs). In these materials, superconducting fluctuations appear over a wide range of temperatures due to the superconductors extremely short coherence lengths and low effective dimensionality of the electron systems. These strong fluctuations lead to anomalous properties of the normal statemore » in some HTS materials. Within the framework of the phenomenological Ginzburg-Landau theory, and more extensively in the diagrammatic microscopic approach based on BCS theory, SC fluctuations as well as other quantum contributions (weak localization, etc.) enabled a new way to investigate and characterize disordered electron systems, granular metals, Josephson structures, artificial superlattices, and others. The characteristic feature of SC fluctuations is its strong dependence on temperature and magnetic field in the vicinity of the superconducting phase transition. This dependence allows the separation of fluctuation effects from other contributions and provides information about the microscopic parameters of a material, in particular, the critical temperature and the zero-temperature critical magnetic field. As such, SC fluctuations are very sensitive to the relaxation processes that break phase coherence and can be used as a versatile characterization instrument for SCs: Fluctuation spectroscopy has emerged as a powerful tool for studying the properties of superconducting systems on a quantitative level. Here the physics of SC fluctuations is reviewed, commencing from a qualitative description of thermodynamic fluctuations close to the critical temperature and quantum fluctuations at zero temperature in the vicinity of the second critical field. The analysis of the latter allows us to present fluctuation formation as a fragmentation of the Abrikosov lattice. Finally, this review highlights a series of experimental findings followed by microscopic description and numerical analysis of the effects of fluctuations on numerous properties of superconductors in the entire phase diagram and beyond the superconducting phase.« less

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

DOE PAGES

Varlamov, A. A.; Galda, A.; Glatz, A.

2018-03-27

Superconducting (SC) fluctuations, discovered in the late 1960s, have constituted an important research area in superconductivity as they are manifest in a variety of phenomena. Indeed, the underlying physics of SC fluctuations makes it possible to elucidate the fundamental properties of the superconducting state. The interest in SC fluctuation phenomena was further enhanced with the discovery of cuprate high-temperature superconductors (HTSs). In these materials, superconducting fluctuations appear over a wide range of temperatures due to the superconductors extremely short coherence lengths and low effective dimensionality of the electron systems. These strong fluctuations lead to anomalous properties of the normal statemore » in some HTS materials. Within the framework of the phenomenological Ginzburg-Landau theory, and more extensively in the diagrammatic microscopic approach based on BCS theory, SC fluctuations as well as other quantum contributions (weak localization, etc.) enabled a new way to investigate and characterize disordered electron systems, granular metals, Josephson structures, artificial superlattices, and others. The characteristic feature of SC fluctuations is its strong dependence on temperature and magnetic field in the vicinity of the superconducting phase transition. This dependence allows the separation of fluctuation effects from other contributions and provides information about the microscopic parameters of a material, in particular, the critical temperature and the zero-temperature critical magnetic field. As such, SC fluctuations are very sensitive to the relaxation processes that break phase coherence and can be used as a versatile characterization instrument for SCs: Fluctuation spectroscopy has emerged as a powerful tool for studying the properties of superconducting systems on a quantitative level. Here the physics of SC fluctuations is reviewed, commencing from a qualitative description of thermodynamic fluctuations close to the critical temperature and quantum fluctuations at zero temperature in the vicinity of the second critical field. The analysis of the latter allows us to present fluctuation formation as a fragmentation of the Abrikosov lattice. Finally, this review highlights a series of experimental findings followed by microscopic description and numerical analysis of the effects of fluctuations on numerous properties of superconductors in the entire phase diagram and beyond the superconducting phase.« less

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

NASA Astrophysics Data System (ADS)

Varlamov, A. A.; Galda, A.; Glatz, A.

2018-01-01

Superconducting (SC) fluctuations, discovered in the late 1960s, have constituted an important research area in superconductivity as they are manifest in a variety of phenomena. Indeed, the underlying physics of SC fluctuations makes it possible to elucidate the fundamental properties of the superconducting state. The interest in SC fluctuation phenomena was further enhanced with the discovery of cuprate high-temperature superconductors (HTSs). In these materials, superconducting fluctuations appear over a wide range of temperatures due to the superconductors extremely short coherence lengths and low effective dimensionality of the electron systems. These strong fluctuations lead to anomalous properties of the normal state in some HTS materials. Within the framework of the phenomenological Ginzburg-Landau theory, and more extensively in the diagrammatic microscopic approach based on BCS theory, SC fluctuations as well as other quantum contributions (weak localization, etc.) enabled a new way to investigate and characterize disordered electron systems, granular metals, Josephson structures, artificial superlattices, and others. The characteristic feature of SC fluctuations is its strong dependence on temperature and magnetic field in the vicinity of the superconducting phase transition. This dependence allows the separation of fluctuation effects from other contributions and provides information about the microscopic parameters of a material, in particular, the critical temperature and the zero-temperature critical magnetic field. As such, SC fluctuations are very sensitive to the relaxation processes that break phase coherence and can be used as a versatile characterization instrument for SCs: Fluctuation spectroscopy has emerged as a powerful tool for studying the properties of superconducting systems on a quantitative level. Here the physics of SC fluctuations is reviewed, commencing from a qualitative description of thermodynamic fluctuations close to the critical temperature and quantum fluctuations at zero temperature in the vicinity of the second critical field. The analysis of the latter allows us to present fluctuation formation as a fragmentation of the Abrikosov lattice. This review highlights a series of experimental findings followed by microscopic description and numerical analysis of the effects of fluctuations on numerous properties of superconductors in the entire phase diagram and beyond the superconducting phase.

Re-evaluation of differential phase contrast (DPC) in a scanning laser microscope using a split detector as an alternative to differential interference contrast (DIC) optics.

PubMed

Amos, W B; Reichelt, S; Cattermole, D M; Laufer, J

2003-05-01

In this paper, differential phase imaging (DPC) with transmitted light is implemented by adding a suitable detection system to a standard commercially available scanning confocal microscope. DPC, a long-established method in scanning optical microscopy, depends on detecting the intensity difference between opposite halves or quadrants of a split photodiode detector placed in an aperture plane. Here, DPC is compared with scanned differential interference contrast (DIC) using a variety of biological specimens and objective lenses of high numerical aperture. While DPC and DIC images are generally similar, DPC seems to have a greater depth of field. DPC has several advantages over DIC. These include low cost (no polarizing or strain-free optics are required), absence of a double scanning spot, electronically variable direction of shading and the ability to image specimens in plastic dishes where birefringence prevents the use of DIC. DPC is also here found to need 20 times less laser power at the specimen than DIC.

Advanced electron microscopy methods for the analysis of MgB2 superconductor

NASA Astrophysics Data System (ADS)

Birajdar, B.; Peranio, N.; Eibl, O.

2008-02-01

Advanced electron microscopy methods used for the analysis of superconducting MgB2 wires and tapes are described. The wires and tapes were prepared by the powder in tube method using different processing technologies and thoroughly characterised for their superconducting properties within the HIPERMAG project. Microstructure analysis on μm to nm length scales is necessary to understand the superconducting properties of MgB2. For the MgB2 phase analysis on μm scale an analytical SEM, and for the analysis on nm scale a energy-filtered STEM is used. Both the microscopes were equipped with EDX detector and field emission gun. Electron microscopy and spectroscopy of MgB2 is challenging because of the boron analysis, carbon and oxygen contamination, and the presence of large number of secondary phases. Advanced electron microscopy involves, combined SEM, EPMA and TEM analysis with artefact free sample preparation, elemental mapping and chemical quantification of point spectra. Details of the acquisition conditions and achieved accuracy are presented. Ex-situ wires show oxygen-free MgB2 colonies (a colony is a dense arrangement of several MgB2 grains) embedded in a porous and oxygen-rich matrix, introducing structural granularity. In comparison, in-situ wires are generally more dense, but show inhibited MgB2 phase formation with significantly higher fraction of B-rich secondary phases. SiC additives in the in-situ wires forms Mg2Si secondary phases. The advanced electron microscopy has been used to extract the microstructure parameters like colony size, B-rich secondary phase fraction, O mole fraction and MgB2 grain size, and establish a microstructure-critical current density model [1]. In summary, conventional secondary electron imaging in SEM and diffraction contrast imaging in the TEM are by far not sufficient and advanced electron microscopy methods are essential for the analysis of superconducting MgB2 wires and tapes.

Back-scattered electron imaging of skeletal tissues.

PubMed

Boyde, A; Jones, S J

The use of solid-state back-scattered electron (BSE) detectors in the scanning electron microscopic study of skeletal tissues has been investigated. To minimize the topographic element in the image, flat samples and a ring detector configuration with the sample at normal incidence to the beam and the detector are used. Very flat samples are prepared by diamond micromilling or diamond polishing plastic-embedded tissue. Density discrimination in the image is so good that different density phases within mineralized bone can be imaged. For unembedded spongy bone, cut surfaces can be discriminated from natural surfaces by a topographic contrast mechanism. BSE imaging also presents advantages for unembedded samples with rough topography, such as anorganic preparations of the mineralization zone in cartilage, which give rise to severe charging problems with conventional secondary electron imaging.

Probing Dirac fermion dynamics in topological insulator Bi2Se3 films with a scanning tunneling microscope.

PubMed

Song, Can-Li; Wang, Lili; He, Ke; Ji, Shuai-Hua; Chen, Xi; Ma, Xu-Cun; Xue, Qi-Kun

2015-05-01

Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi2Se3 ultrathin films. At the two-dimensional limit, bulk electrons become quantized and the quantization can be controlled by the film thickness at a single quintuple layer level. By studying the spatial decay of standing waves (quasiparticle interference patterns) off steps, we measure directly the energy and film thickness dependence of the phase relaxation length lϕ and inelastic scattering lifetime τ of topological surface-state electrons. We find that τ exhibits a remarkable (E - EF)(-2) energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.

Scanning electron microscope observation of dislocations in semiconductor and metal materials.

PubMed

Kuwano, Noriyuki; Itakura, Masaru; Nagatomo, Yoshiyuki; Tachibana, Shigeaki

2010-08-01

Scanning electron microscope (SEM) image contrasts have been investigated for dislocations in semiconductor and metal materials. It is revealed that single dislocations can be observed in a high contrast in SEM images formed by backscattered electrons (BSE) under the condition of a normal configuration of SEM. The BSE images of dislocations were compared with those of the transmission electron microscope and scanning transmission electron microscope (STEM) and the dependence of BSE image contrast on the tilting of specimen was examined to discuss the origin of image contrast. From the experimental results, it is concluded that the BSE images of single dislocations are attributed to the diffraction effect and related with high-angle dark-field images of STEM.

Flexible high-voltage supply for experimental electron microscope

NASA Technical Reports Server (NTRS)

Chapman, G. L.; Jung, E. A.; Lewis, R. N.; Van Loon, L. S.; Welter, L. M.

1969-01-01

Scanning microscope uses a field-emission tip for the electron source, an electron gun that simultaneously accelerates and focuses electrons from the source, and one auxiliary lens to produce a final probe size at the specimen on the order of angstroms.

Ion microprobe, electron microprobe and cathodoluminescence data for Allende inclusions with emphasis on plagioclase chemistry

NASA Technical Reports Server (NTRS)

Hutcheon, I. D.; Steele, I. M.; Smith, J. V.; Clayton, R. N.

1978-01-01

Three Type B inclusions from the Allende meteorite have been analyzed. A grain-to-grain characterization of mineral chemistry and isotopic content was made possible by the use of a range of techniques, including luminescence and scanning electron microscopy and electron and ion microprobe analysis. Cathodoluminescence was used in fine-grained, optically opaque regions to distinguish between sub-micrometer phases, such as garnet and Si-rich material, subsequently identified by electron probe and scanning electron microscope analyses. Four types of luminescence patterns, due to twinning, primary sector zoning, alteration of boundaries and fractures, and shock effects, were identified in Allende plagioclase. Luminescence color exhibited a strong correlation with Mg content and provided a guide for an electron probe quantitative map of Mg and Na distributions. Ion microprobe studies of individual grains revealed large excesses of Mg-26.

Spectro-microscopic Characterization of Physical Properties and Phase Separations in Individual Atmospheric Particles

NASA Astrophysics Data System (ADS)

OBrien, R. E.; Wang, B.; Neu, A.; Kelly, S. T.; Lundt, N.; Epstein, S. A.; MacMillan, A.; You, Y.; Laskin, A.; Nizkorodov, S.; Bertram, A. K.; Moffet, R.; Gilles, M.

2013-12-01

The phase state and liquid-liquid phase separations of ambient and laboratory generated aerosol particles were investigated using (1) scanning transmission x-ray microscopy/near-edge x-ray absorption fine structure spectroscopy (STXM/NEXAFS) coupled to a relative humidity (RH) controlled in-situ chamber and (2) environmental scanning electron microscopy (ESEM). The phase states of the particles were determined from measurements of their size and optical density. A comparison is made between the observed phase states of ambient samples and of laboratory generated aerosols to determine how well laboratory samples represent the phase of ambient samples. In addition, liquid-liquid phase separations in laboratory generated particles were investigated. Preliminary results showing that liquid-liquid phase separations occur at RH's between the deliquescence and efflorescence points and that the organic phase surrounds the inorganic phase will be presented. The STXM/NEXAFS technique provides insight into the degree of mixing at the deliquescence point and the degree of phase separation for particles of atmospherically relevant sizes.

Scanning and transmission electron microscopic analysis of ampullary segment of oviduct during estrous cycle in caprines.

PubMed

Sharma, R K; Singh, R; Bhardwaj, J K

2015-01-01

The ampullary segment of the mammalian oviduct provides suitable milieu for fertilization and development of zygote before implantation into uterus. It is, therefore, in the present study, the cyclic changes in the morphology of ampullary segment of goat oviduct were studied during follicular and luteal phases using scanning and transmission electron microscopy techniques. Topographical analysis revealed the presence of uniformly ciliated ampullary epithelia, concealing apical processes of non-ciliated cells along with bulbous secretory cells during follicular phase. The luteal phase was marked with decline in number of ciliated cells with increased occurrence of secretory cells. The ultrastructure analysis has demonstrated the presence of indented nuclear membrane, supranuclear cytoplasm, secretory granules, rough endoplasmic reticulum, large lipid droplets, apically located glycogen masses, oval shaped mitochondria in the secretory cells. The ciliated cells were characterized by the presence of elongated nuclei, abundant smooth endoplasmic reticulum, oval or spherical shaped mitochondria with crecentric cristae during follicular phase. However, in the luteal phase, secretory cells were possessing highly indented nucleus with diffused electron dense chromatin, hyaline nucleosol, increased number of lipid droplets. The ciliated cells had numerous fibrous granules and basal bodies. The parallel use of scanning and transmission electron microscopy techniques has enabled us to examine the cyclic and hormone dependent changes occurring in the topography and fine structure of epithelium of ampullary segment and its cells during different reproductive phases that will be great help in understanding major bottle neck that limits success rate in vitro fertilization and embryo transfer technology. © Wiley Periodicals, Inc.

Solid-phase diffusion mechanism for GaAs nanowire growth.

PubMed

Persson, Ann I; Larsson, Magnus W; Stenström, Stig; Ohlsson, B Jonas; Samuelson, Lars; Wallenberg, L Reine

2004-10-01

Controllable production of nanometre-sized structures is an important field of research, and synthesis of one-dimensional objects, such as nanowires, is a rapidly expanding area with numerous applications, for example, in electronics, photonics, biology and medicine. Nanoscale electronic devices created inside nanowires, such as p-n junctions, were reported ten years ago. More recently, hetero-structure devices with clear quantum-mechanical behaviour have been reported, for example the double-barrier resonant tunnelling diode and the single-electron transistor. The generally accepted theory of semiconductor nanowire growth is the vapour-liquid-solid (VLS) growth mechanism, based on growth from a liquid metal seed particle. In this letter we suggest the existence of a growth regime quite different from VLS. We show that this new growth regime is based on a solid-phase diffusion mechanism of a single component through a gold seed particle, as shown by in situ heating experiments of GaAs nanowires in a transmission electron microscope, and supported by highly resolved chemical analysis and finite element calculations of the mass transport and composition profiles.

Holography and coherent diffraction with low-energy electrons: A route towards structural biology at the single molecule level.

PubMed

Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

2015-12-01

The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2Å has been achieved revealing the 660.000 unit cells of the graphene sheet from a single data set. Once applied to individual biomolecules the method shall ultimately allow for non-destructive imaging and imports the potential to distinguish between different conformations of proteins with atomic resolution. Copyright © 2015. Published by Elsevier B.V.

Phase-dependent noise in Josephson junctions

NASA Astrophysics Data System (ADS)

Sheldon, Forrest; Peotta, Sebastiano; Di Ventra, Massimiliano

2018-03-01

In addition to the usual superconducting current, Josephson junctions (JJs) support a phase-dependent conductance related to the retardation effect of tunneling quasi-particles. This introduces a dissipative current with a memory-resistive (memristive) character that should also affect the current noise. By means of the microscopic theory of tunnel junctions we compute the complete current autocorrelation function of a Josephson tunnel junction and show that this memristive component gives rise to both a previously noted phase-dependent thermal noise, and an undescribed non-stationary, phase-dependent dynamic noise. As experiments are approaching ranges in which these effects may be observed, we examine the form and magnitude of these processes. Their phase dependence can be realized experimentally as a hysteresis effect and may be used to probe defects present in JJ based qubits and in other superconducting electronics applications.

Rapid synthesis of tin oxide nanostructures by microwave-assisted thermal oxidation for sensor applications

NASA Astrophysics Data System (ADS)

Phadungdhitidhada, S.; Ruankham, P.; Gardchareon, A.; Wongratanaphisan, D.; Choopun, S.

2017-09-01

In the present work nanostructures of tin oxides were synthesized by a microwave-assisted thermal oxidation. Tin precursor powder was loaded into a cylindrical quartz tube and further radiated in a microwave oven. The as-synthesized products were characterized by scanning electron microscope, transmission electron microscope, and x-ray diffractometer. The results showed that two different morphologies of SnO2 microwires (MWs) and nanoparticles (NPs) were obtained in one minute of microwave radiation under atmospheric ambient. A few tens of the SnO2 MWs with the length of 10-50 µm were found. Some parts of the MWs were decorated with the SnO2 NPs. However, most of the products were SnO2 NPs with the diameter ranging from 30-200 nm. Preparation under loosely closed system lead to mixed phase SnO-SnO2 NPs with diameter of 30-200 nm. The single-phase of SnO2 could be obtained by mixing the Sn precursor powders with CuO2. The products were mostly found to be SnO2 nanowires (NWs) and MWs. The diameter of SnO2 NWs was less than 50 nm. The SnO2 NPs, MWs, and NWs were in the cassiterite rutile structure phase. The SnO NPs was in the tetragonal structure phase. The growth direction of the SnO2 NWs was observed in (1 1 0) and (2 2 1) direction. The ethanol sensor performance of these tin oxide nanostructures showed that the SnO-SnO2 NPs exhibited extremely high sensitivity. Invited talk at 5th Thailand International Nanotechnology Conference (Nano Thailand-2016), 27-29 November 2016, Nakhon Ratchasima, Thailand.

Advanced Microstructural Study of Suspension Plasma Sprayed Hydroxyapatite Coatings

NASA Astrophysics Data System (ADS)

Podlesak, Harry; Pawlowski, Lech; D'Haese, Romain; Laureyns, Jacky; Lampke, Thomas; Bellayer, Severine

2010-03-01

Fine, home-synthesized, hydroxyapatite powder was formulated with water and alcohol to obtain a suspension used to plasma spray coatings onto a titanium substrate. The deposition process was optimized using statistical design of 2 n experiments with two variables: spray distance and electric power input to plasma. X-ray diffraction (XRD) was used to determine quantitatively the phase composition of obtained deposits. Raman microscopy and electron probe microanalysis (EPMA) enabled localization of the phases in different positions of the coating cross sections. Transmission electron microscopic (TEM) study associated with energy-dispersive x-ray spectroscopy (EDS) enabled visualization and analysis of a two-zone microstructure. One zone contained crystals of hydroxyapatite, tetracalcium phosphate, and a phase rich in calcium oxide. This zone included lamellas, usually observed in thermally sprayed coatings. The other zone contained fine hydroxyapatite grains that correspond to nanometric and submicrometric solids from the suspension that were agglomerated and sintered in the cold regions of plasma jet and on the substrate.

Scanning-electron-microscope used in real-time study of friction and wear

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Buckley, D. H.

1975-01-01

Small friction and wear apparatus built directly into scanning-electron-microscope provides both dynamic observation and microscopic view of wear process. Friction and wear tests conducted using this system have indicated that considerable information can readily be gained.

Preparation and Characterization of Carbon Filaments

DTIC Science & Technology

1991-04-01

Kawasumi, "Whiskerization of Carbon Beads by Vapor Phase Growth of Carbon Fibers to Obtain Sea Urchin -Type Particles", Carbon 21, 89 (1983). 5) R.T.K...multiple fiber microstructure are possible on what appears to be a single fiber along the length of the fiber. However, without SEM micrographs, it is...180 minutes. Scanning Electron Microscopic ( SEM ) observations were cared out using P Philips series 505 SEM system, typically operating at an

STUDY OF MICROPLASTIC PROPERTIES AND DIMENSIONAL STABILITY OF MATERIALS

DTIC Science & Technology

Microyield stresses of 39-40 ksi for Ni-Span-C, 69-70 ksi for 440 C stainless steel, and 7.5 ksi for A 356 cast aluminum have been determined ...hours. Electron microscope studies indicated that microplastic flow in Ni-Span-C is the result of dislocation generation at second phase particles in...Experiments are being conducted to determine , and eventually minimize, the residual stresses introduced by machining in all of the materials being

Failure analysis on optical fiber on swarm flight payload

NASA Astrophysics Data System (ADS)

Bourcier, Frédéric; Fratter, Isabelle; Teyssandier, Florent; Barenes, Magali; Dhenin, Jérémie; Peyriguer, Marie; Petre-Bordenave, Romain

2017-11-01

Failure analysis on optical components is usually carried-out, on standard testing devices such as optical/electronic microscopes and spectrometers, on isolated but representative samples. Such analyses are not contactless and not totally non-invasive, so they cannot be used easily on flight models. Furthermore, for late payload or satellite integration/validation phases with tight schedule issues, it could be necessary to carry out a failure analysis directly on the flight hardware, in cleanroom.

Switching adhesion forces by crossing the metal–insulator transition in Magnéli-type vanadium oxide crystals

PubMed Central

Klemm, Matthias; Horn, Siegfried; Woydt, Mathias

2011-01-01

Summary Magnéli-type vanadium oxides form the homologous series VnO2 n -1 and exhibit a temperature-induced, reversible metal–insulator first order phase transition (MIT). We studied the change of the adhesion force across the transition temperature between the cleavage planes of various vanadium oxide Magnéli phases (n = 3 … 7) and spherical titanium atomic force microscope (AFM) tips by systematic force–distance measurements with a variable-temperature AFM under ultrahigh vacuum conditions (UHV). The results show, for all investigated samples, that crossing the transition temperatures leads to a distinct change of the adhesion force. Low adhesion corresponds consistently to the metallic state. Accordingly, the ability to modify the electronic structure of the vanadium Magnéli phases while maintaining composition, stoichiometry and crystallographic integrity, allows for relating frictional and electronic material properties at the nano scale. This behavior makes the vanadium Magnéli phases interesting candidates for technology, e.g., as intelligent devices or coatings where switching of adhesion or friction is desired. PMID:21977416

Microstructure of RERTR DU-alloys irradiated with krypton ions up to 100 dpa

NASA Astrophysics Data System (ADS)

Gan, J.; Keiser, D. D., Jr.; Miller, B. D.; Wachs, D. M.; Allen, T. R.; Kirk, M.; Rest, J.

2011-04-01

The radiation stability of the interaction product formed at the fuel-matrix interface of research reactor dispersion fuels, under fission-product bombardment, has a strong impact on fuel performance. Three depleted uranium alloys were cast that consisted of the following five phases to be investigated: U(Si, Al) 3, (U, Mo)(Si, Al) 3, UMo 2Al 20, U 6Mo 4Al 43, and UAl 4. Irradiation of transmission electron microscopy (TEM) disc samples with 500-keV Kr ions at 200 °C to doses up to ˜100 displacements per atom (dpa) were conducted using a 300-keV electron microscope equipped with an ion accelerator. TEM results show that the U(Si, Al) 3 and UAl 4 phases remain crystalline at 100 dpa without forming voids. The (U, Mo)(Si, Al) 3 and UMo 2Al 20 phases become amorphous at 1 and ˜2 dpa, respectively, and show no evidence of voids at 100 dpa. The U 6Mo 4Al 43 phase goes to amorphous at less than 1 dpa and reveals high density voids at 100 dpa.

Facile synthesis of high-temperature (1000 °C) phase-stable rice-like anatase TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Lv, Lizhen; Chen, Qirong; Liu, Xiuyun; Wang, Miaomiao; Meng, Xiangfu

2015-05-01

High-temperature phase-stable rice-like anatase TiO2 nanocrystals were synthesized by one-pot solvothermal method using soluble titania xerogel and isopropyl alcohol (IPA) as the precursor and the solvent, respectively. Sample characterization was carried out by powder X-ray diffraction, high-resolution transmission electron microscopy, field emission scanning electron microscope, X-ray photoelectron spectroscopy, and N2 adsorption-desorption isotherms. The results showed that TiO2 nanocrystals had rice-like shapes with an average size of 5 nm in width and 35 nm in length. The BET surface area was 153 m2/g. Unexpectedly, the rice-like TiO2 nanocrystals exhibited high-temperature phase stability, which could remain as pure anatase phase after calcinations at 1000 °C. Growth mechanism investigation revealed that the IPA solvent played a key role in nucleation and growth of rice-like anatase TiO2 nanocrystals. The photodegradation of rhodamine B demonstrated that rice-like anatase TiO2 nanocrystals exhibited enhanced photocatalytic activity under visible light irradiation.

Thermal-Wave Microscope

NASA Technical Reports Server (NTRS)

Jones, Robert E.; Kramarchuk, Ihor; Williams, Wallace D.; Pouch, John J.; Gilbert, Percy

1989-01-01

Computer-controlled thermal-wave microscope developed to investigate III-V compound semiconductor devices and materials. Is nondestructive technique providing information on subsurface thermal features of solid samples. Furthermore, because this is subsurface technique, three-dimensional imaging also possible. Microscope uses intensity-modulated electron beam of modified scanning electron microscope to generate thermal waves in sample. Acoustic waves generated by thermal waves received by transducer and processed in computer to form images displayed on video display of microscope or recorded on magnetic disk.

Interference Confocal Microscope Integrated with Spatial Phase Shifter.

PubMed

Wang, Weibo; Gu, Kang; You, Xiaoyu; Tan, Jiubin; Liu, Jian

2016-08-24

We present an interference confocal microscope (ICM) with a new single-body four-step simultaneous phase-shifter device designed to obtain high immunity to vibration. The proposed ICM combines the respective advantages of simultaneous phase shifting interferometry and bipolar differential confocal microscopy to obtain high axis resolution, large dynamic range, and reduce the sensitivity to vibration and reflectance disturbance seamlessly. A compact single body spatial phase shifter is added to capture four phase-shifted interference signals simultaneously without time delay and construct a stable and space-saving simplified interference confocal microscope system. The test result can be obtained by combining the interference phase response and the bipolar property of differential confocal microscopy without phase unwrapping. Experiments prove that the proposed microscope is capable of providing stable measurements with 1 nm of axial depth resolution for either low- or high-numerical aperture objective lenses.

Iridates and RuCl3 - from Heisenberg antiferromagnets to potential Kitaev spin-liquids

NASA Astrophysics Data System (ADS)

van den Brink, Jeroen

The observed richness of topological states on the single-electron level prompts the question what kind of topological phases can develop in more strongly correlated, many-body electron systems. Correlation effects, in particular intra- and inter-orbital electron-electron interactions, are very substantial in 3 d transition-metal compounds such as the copper oxides, but the spin-orbit coupling (SOC) is weak. In 5 d transition-metal compounds such as iridates, the interesting situation arises that the SOC and Coulomb interactions meet on the same energy scale. The electronic structure of iridates thus depends on a strong competition between the electronic hopping amplitudes, local energy-level splittings, electron-electron interaction strengths, and the SOC of the Ir 5d electrons. The interplay of these ingredients offers the potential to stabilise relatively well-understood states such as a 2D Heisenberg-like antiferromagnet in Sr2IrO4, but in principle also far more exotic ones, such a topological Kitaev quantum spin liquid, in (hyper)honeycomb iridates. I will discuss the microscopic electronic structures of these iridates, their proximity to idealized Heisenberg and Kitaev models and our contributions to establishing the physical factors that appear to have preempted the realization of quantum spin liquid phases so far and include a discussion on the 4d transition metal chloride RuCl3. Supported by SFB 1143 of the Deutsche Forschungsgemeinschaft.

Pseudotachylyte in the Tananao Metamorphic Complex, Taiwan: Occurrence and dynamic phase changes of fossil earthquakes

NASA Astrophysics Data System (ADS)

Chu, Hao-Tsu; Hwang, Shyh-Lung; Shen, Pouyan; Yui, Tzen-Fu

2012-12-01

Pseudotachylyte veins and cataclasites were studied in the mylonitized granitic gneiss of the Tananao Metamorphic Complex at Hoping, Eastern Taiwan. The aphanitic pseudotachylyte veins vary in thickness, ranging from millimeters to about 1 cm. Field and optical microscopic observations show that such pseudotachylyte veins cut across cataclasites, which, in turn, transect the mylonitized granitic gneiss. Scanning electron microscopic images also show that both the pseudotachylyte veins and the cataclasites have been metasomatized by a K-rich fluid, resulting in the replacement of Na-plagioclase by K-feldspar (veins). Analytical electron microscopic observations reveal further details of physical and chemical changes (mainly fragmentation, dislocations, cleaving-healing with inclusions and relic voids, and retention of high-temperature albite) of quartz and feldspar in crushed grains. Pseudotachylytes occur as dark veins having a higher content of chlorite-biotite, clinozoisite-epidote and titanite fragments than cataclasites. These veins, coupled with hematite/jarosite-Fe-rich amorphous shell/carbonaceous material, indicate that crushing, healing/sintering, and inhomogeneous melt/fluid infiltration involving incipient and intermediate/high temperature melt patches, before and/or contemporaneous with the metasomatic K-rich fluid, prevailed in a coupled or sequential manner in the faulting event to form nonequilibrium phase assemblage. The chlorite-biotite, carbonaceous material and other nanoscale minerals could be vulnerable in future earthquakes under the influence of water. The timing of the formation of these pseudotachylyte veins should be later than the area's age of mylonitization of granitic gneiss of approximately 4.1-3.0 Ma (Wang et al., 1998). The formation of pseudotachylytes registers the fossil earthquakes during early stages in the exhumation history of the uplifting Taiwan Mountain belt since the Plio-Pleistocene Arc-Continent collision.

Microscopic evolution of dielectric nanoparticles at different calcination temperatures synthesized via sol-gel auto-combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adil, Muhammad, E-mail: muhammadadil86@hotmail.com; Zaid, Hasnah Mohd, E-mail: hasnamz@petronas.com.my; Chuan, Lee Kean, E-mail: lee.kc@petronas.com.my

2015-07-22

Dielectric nano powder synthesis is carried by a simple and fast sol-gel auto-combustion method. The transformation of crystalline phases of as-synthesized nano powders is investigated through the detailed transmission electron microscopy (TEM), revealed the crystallographic alterations and morphological information even at lattice scale. From specific area electron diffraction (SAED) pattern, has specified the d-spacing and corresponding planes supported by the observed lattice fringes. The morphological characterization of nanoparticles is performed through field-emission scanning electron microscopy (FESEM), exhibiting the increment in particle size due to agglomeration with the increase in annealing temperature. Furthermore, EDX pattern has been used to verify themore » formation of nanoparticles by revealing the presence of required elements.« less

Microstructure and magnetic properties of alnico permanent magnetic alloys with Zr-B additives

NASA Astrophysics Data System (ADS)

Rehman, Sajjad Ur; Jiang, Qingzheng; Ge, Qing; Lei, Weikai; Zhang, Lili; Zeng, Qingwen; ul Haq, A.; Liu, Renhui; Zhong, Zhenchen

2018-04-01

Alnico alloys are prepared with nominal composition of 31.4-xFe-7.0Al-36.0Co-4.0Cu-1.0Nb-14.0Ni-6.0Ti-0.6Zr-xB (x = 0.02, 0.04, 0.06, 0.08, in wt%) by arc melting and casting techniques and subsequent heat treatment. The alloys are characterized by X-ray diffraction method, optical microscope, scanning electron microscope and pulse field magnetometer by plotting magnetic hysteresis demagnetization curve. The results of HRSEM show at least two new phases at α-grain boundaries and triple junctions. These phases, when retained at low concentration, help in enhancing magnetic properties of alnico alloys by purifying spinodal phases and reducing the adverse effects of impurity elements. Two different heat treatment cycles are employed. In the first phase, the alloys are processed by using heat treatment cycles without magnetic field; and Hc of 1.35 kOe, Br of 4.87 kGs and (BH)max of 1.96 MGOe are obtained by furnace cooling below TC and subsequent tempering at 680 °C and 550 °C. In the second phase, the alloy with best magnetic properties is treated thermo-magnetically; and Hc of 1.68 kOe, Br of 7.1 kG and (BH)max of 4.45 MGOe are obtained.

2D strain mapping using scanning transmission electron microscopy Moiré interferometry and geometrical phase analysis.

PubMed

Pofelski, A; Woo, S Y; Le, B H; Liu, X; Zhao, S; Mi, Z; Löffler, S; Botton, G A

2018-04-01

A strain characterization technique based on Moiré interferometry in a scanning transmission electron microscope (STEM) and geometrical phase analysis (GPA) method is demonstrated. The deformation field is first captured in a single STEM Moiré hologram composed of multiple sets of periodic fringes (Moiré patterns) generated from the interference between the periodic scanning grating, fixing the positions of the electron probe on the sample, and the crystal structure. Applying basic principles from sampling theory, the Moiré patterns arrangement is then simulated using a STEM electron micrograph reference to convert the experimental STEM Moiré hologram into information related to the crystal lattice periodicities. The GPA method is finally applied to extract the 2D relative strain and rotation fields. The STEM Moiré interferometry enables the local information to be de-magnified to a large length scale, comparable to what can be achieved in dark-field electron holography. The STEM Moiré GPA method thus extends the conventional high-resolution STEM GPA capabilities by providing comparable quantitative 2D strain mapping with a larger field of view (up to a few microns). Copyright © 2017 Elsevier B.V. All rights reserved.

Micro-structural study and Rietveld analysis of fast reactor fuels: U-Mo fuels

NASA Astrophysics Data System (ADS)

Chakraborty, S.; Choudhuri, G.; Banerjee, J.; Agarwal, Renu; Khan, K. B.; Kumar, Arun

2015-12-01

U-Mo alloys are the candidate fuels for both research reactors and fast breeder reactors. In-reactor performance of the fuel depends on the microstructural stability and thermal properties of the fuel. To improve the fuel performance, alloying elements viz. Zr, Mo, Nb, Ti and fissium are added in the fuel. The first reactor fuels are normally prepared by injection casting. The objective of this work is to compare microstructure, phase-fields and hardness of as-cast four different U-Mo alloy (2, 5, 10 and 33 at.% Mo) fuels with the equilibrium microstructure of the alloys. Scanning electron microscope with energy dispersive spectrometer and optical microscope have been used to characterize the morphology of the as-cast and annealed alloys. The monoclinic α'' phase in as-cast U-10 at.% Mo alloy has been characterized through Rietveld analysis. A comparison of metallographic and Rietveld analysis of as-cast (dendritic microstructure) and annealed U-33 at.% Mo alloy, corresponding to intermetallic compound, has been reported here for the first time. This study will provide in depth understanding of microstructural and phase evolution of U-Mo alloys as fast reactor fuel.

Femtosecond laser-induced phase transformations in amorphous Cu77Ni6Sn10P7 alloy

NASA Astrophysics Data System (ADS)

Zhang, Y.; Liu, L.; Zou, G.; Chen, N.; Wu, A.; Bai, H.; Zhou, Y.

2015-01-01

In this study, the femtosecond laser-induced crystallization of CuNiSnP amorphous ribbons was investigated by utilizing an amplified Ti:sapphire laser system. X-ray diffraction and scanning electronic microscope were applied to examine the phase and morphology changes of the amorphous ribbons. Micromachining without crystallization, surface patterning, and selective crystallization were successfully achieved by changing laser parameters. Obvious crystallization occurred under the condition that the laser fluence was smaller than the ablation threshold, indicating that the structural evolution of the material depends strongly on the laser parameters. Back cooling method was used to inhibit heat accumulation; a reversible transformation between the disordered amorphous and crystalline phases can be achieved by using this method.

Cooper Pairs in Insulators?!

ScienceCinema

James Valles

2017-12-09

Nearly 50 years elapsed between the discovery of superconductivity and the emergence of the microscopic theory describing this zero resistance state. The explanation required a novel phase of matter in which conduction electrons joined in weakly bound pairs and condensed with other pairs into a single quantum state. Surprisingly, this Cooper pair formation has also been invoked to account for recently uncovered high-resistance or insulating phases of matter. To address this possibility, we have used nanotechnology to create an insulating system that we can probe directly for Cooper pairs. I will present the evidence that Cooper pairs exist and dominate the electrical transport in these insulators and I will discuss how these findings provide new insight into superconductor to insulator quantum phase transitions. 

Kinetics of microbial reduction of Solid phase U(VI).

PubMed

Liu, Chongxuan; Jeon, Byong-Hun; Zachara, John M; Wang, Zheming; Dohnalkova, Alice; Fredrickson, James K

2006-10-15

Sodium boltwoodite (NaUO2SiO3OH x 1.5 H2O) was used to assess the kinetics of microbial reduction of solid-phase U(VI) by a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1. The bioreduction kinetics was studied with Na-boltwoodite in suspension or within alginate beads in a nongrowth medium with lactate as electron donor at pH 6.8 buffered with PIPES. Concentrations of U(VI)tot and cell number were varied to evaluate the coupling of U(VI) dissolution, diffusion, and microbial activity. Microscopic and spectroscopic analyses with transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and laser-induced fluorescence spectroscopy (LIFS) collectively indicated that solid-phase U(VI) was first dissolved and diffused out of grain interiors before it was reduced on bacterial surfaces and/or within the periplasm. The kinetics of solid-phase U(VI) bioreduction was well described by a coupled model of bicarbonate-promoted dissolution of Na-boltwoodite, intragrain uranyl diffusion, and Monod type bioreduction kinetics with respect to dissolved U(VI) concentration. The results demonstrated that microbial reduction of solid-phase U(VI) is controlled by coupled biological, chemical, and physical processes.

Synthesis and characterization of nanocrystalline graphite from coconut shell with heating process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wachid, Frischa M., E-mail: frischamw@yahoo.com, E-mail: adhiyudhaperkasa@yahoo.com, E-mail: afandisar@yahoo.com, E-mail: nurulrosyidah92@gmail.com, E-mail: darminto@physics.its.ac.id; Perkasa, Adhi Y., E-mail: frischamw@yahoo.com, E-mail: adhiyudhaperkasa@yahoo.com, E-mail: afandisar@yahoo.com, E-mail: nurulrosyidah92@gmail.com, E-mail: darminto@physics.its.ac.id; Prasetya, Fandi A., E-mail: frischamw@yahoo.com, E-mail: adhiyudhaperkasa@yahoo.com, E-mail: afandisar@yahoo.com, E-mail: nurulrosyidah92@gmail.com, E-mail: darminto@physics.its.ac.id

Graphite were synthesized and characterized by heating process of coconut shell with varying temperature (400, 800 and 1000°C) and holding time (3 and 5 hours). After heating process, the samples were characterized by X-ray diffraction (XRD) and analyzed by X'pert HighScore Plus Software, Scanning Electron Microcope-Energy Dispersive X-Ray (SEM-EDX) and Transmission Electron Microscope-Energy Dispersive X-Ray (TEM-EDX). Graphite and londsdaelite phase were analyzed by XRD. According to EDX analysis, the sample was heated in 1000°C got the highest content of carbon. The amorphous carbon and nanocrystalline graphite were observed by SEM-EDX and TEM-EDX.

Tunnelling spectroscopy of Andreev states in graphene

NASA Astrophysics Data System (ADS)

Bretheau, Landry; Wang, Joel I.-Jan; Pisoni, Riccardo; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo

2017-08-01

A normal conductor placed in good contact with a superconductor can inherit its remarkable electronic properties. This proximity effect microscopically originates from the formation in the conductor of entangled electron-hole states, called Andreev states. Spectroscopic studies of Andreev states have been performed in just a handful of systems. The unique geometry, electronic structure and high mobility of graphene make it a novel platform for studying Andreev physics in two dimensions. Here we use a full van der Waals heterostructure to perform tunnelling spectroscopy measurements of the proximity effect in superconductor-graphene-superconductor junctions. The measured energy spectra, which depend on the phase difference between the superconductors, reveal the presence of a continuum of Andreev bound states. Moreover, our device heterostructure geometry and materials enable us to measure the Andreev spectrum as a function of the graphene Fermi energy, showing a transition between different mesoscopic regimes. Furthermore, by experimentally introducing a novel concept, the supercurrent spectral density, we determine the supercurrent-phase relation in a tunnelling experiment, thus establishing the connection between Andreev physics at finite energy and the Josephson effect. This work opens up new avenues for probing exotic topological phases of matter in hybrid superconducting Dirac materials.

Analytical and numerical analysis of imaging mechanism of dynamic scanning electron microscopy.

PubMed

Schröter, M-A; Holschneider, M; Sturm, H

2012-11-02

The direct observation of small oscillating structures with the help of a scanning electron beam is a new approach to study the vibrational dynamics of cantilevers and microelectromechanical systems. In the scanning electron microscope, the conventional signal of secondary electrons (SE, dc part) is separated from the signal response of the SE detector, which is correlated to the respective excitation frequency for vibration by means of a lock-in amplifier. The dynamic response is separated either into images of amplitude and phase shift or into real and imaginary parts. Spatial resolution is limited to the diameter of the electron beam. The sensitivity limit to vibrational motion is estimated to be sub-nanometer for high integration times. Due to complex imaging mechanisms, a theoretical model was developed for the interpretation of the obtained measurements, relating cantilever shapes to interaction processes consisting of incident electron beam, electron-lever interaction, emitted electrons and detector response. Conclusions drawn from this new model are compared with numerical results based on the Euler-Bernoulli equation.

Identification of Fragile Microscopic Structures during Mineral Transformations in Wet Supercritical CO2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arey, Bruce W.; Kovarik, Libor; Qafoku, Odeta

2013-04-01

In this study we examine the nature of highly fragile reaction products that form in low water content super critical carbon dioxide (scCO2) using a combination of scanning electron microscopy/focus ion beam (SEM/FIB), confocal Raman spectroscopy, helium ion microscopy (HeIM), and transmission electron microscopy (TEM). HeIM images show these precipitates to be fragile rosettes that can readily decompose even under slight heating from an electron beam. Using the TEM revealed details on the interfacial structure between the newly formed surface precipitates and the underlying initial solid phases. The detailed microscopic analysis revealed that the growth of the precipitates either followedmore » a tip growth mechanism with precipitates forming directly on the forsterite surface if the initial solid was non-porous (natural forsterite) or growth from the surface of the precipitates where fluid was conducted through the porous (nanoforsterite) agglomerates to the growth center. The mechanism of formation of the hydrated/hydroxylated magnesium carbonate compound (HHMC) phases offers insight into the possible mechanisms of carbonate mineral formation from scCO2 solutions which has recently received a great deal of attention as the result of the potential for CO2 to act as an atmospheric greenhouse gas and impact overall global warming. The techniques used here to examine these fragile structures an also be used to examine a wide range of fragile material surfaces. SEM and FIB technologies have now been brought together in a single instrument, which represents a powerful combination for the studies in biological, geological and materials science.« less

Synthesis and characterization of pure strontium apatite particles and nanoporous scaffold prepared by dextrose-templated method

NASA Astrophysics Data System (ADS)

Ma, Xiaoyu; Liu, Yongjia; Zhu, Bangshang

2018-02-01

Strontium shows an increasing interest on bone formation and bone resorption prevention. Here, pure apatite strontium (Ap-SrOH) [Sr5(PO4)3(OH), strontium hydroxyapatite] particles were prepared by the precipitation method using Sr(NO3)2 · 6H2O and (NH4)2HPO4 as reagents. Scanning electron microscope, transmission electron microscope combined with electron diffraction, X-ray diffraction, Fourier transform infrared spectra (FTIR), variable temperature FTIR and thermo gravimetric analysis were employed to evaluate the crystalline structure, chemical composition, and thermal stability of the Ap-SrOH particles. The results show that phase pure Ap-SrOH particles were prepared by wet precipitation. The obtained Ap-SrOH particles are single crystal in phase structure, they have hexagonal fusiform shape, and their size is about 30-180 nm in diameter, and 0.4-2.5 μm in length. The cell MTT assay evaluations indicate that Ap-SrOH particles have very low cytotoxicity. Furthermore, nanoporous Ap-SrOH scaffolds were synthesized by anhydrous dextrose template method. After mixed 5-10 wt% of anhydrous dextrose with Ap-SrOH particles, pressed into discs, and sintered in microwave muffle furnace at 600 °C, the scaffolds with both nanoporous and nanotopography were formed. Cell culture of MC3T3-E1 osteoblasts in vitro show cells grow well on nanoporous Ap-SrOH scaffold. Therefore, Ap-SrOH particles and their nanoporous scaffolds are promising biomaterials for bone repairing and bone disease (e.g. osteoporosis) healing.

Scanning electron microscope fine tuning using four-bar piezoelectric actuated mechanism

NASA Astrophysics Data System (ADS)

Hatamleh, Khaled S.; Khasawneh, Qais A.; Al-Ghasem, Adnan; Jaradat, Mohammad A.; Sawaqed, Laith; Al-Shabi, Mohammad

2018-01-01

Scanning Electron Microscopes are extensively used for accurate micro/nano images exploring. Several strategies have been proposed to fine tune those microscopes in the past few years. This work presents a new fine tuning strategy of a scanning electron microscope sample table using four bar piezoelectric actuated mechanisms. The introduced paper presents an algorithm to find all possible inverse kinematics solutions of the proposed mechanism. In addition, another algorithm is presented to search for the optimal inverse kinematic solution. Both algorithms are used simultaneously by means of a simulation study to fine tune a scanning electron microscope sample table through a pre-specified circular or linear path of motion. Results of the study shows that, proposed algorithms were able to minimize the power required to drive the piezoelectric actuated mechanism by a ratio of 97.5% for all simulated paths of motion when compared to general non-optimized solution.

Carbon-Rich Phases in Cap-Prudhomme Micrometeorites

NASA Astrophysics Data System (ADS)

Perreau, M.; Maurette, M.; Kurat, G.; Engrand, C.

1992-07-01

Two methods were used to search for C-rich phases in micrometeorites collected at Cap-Prudhomme, Antarctica: (i) In the first method ~200-micrometer-sized grains were fragmented into three pieces. The largest one was polished and analyzed with classical techniques of mineralogy for micrometeorite classification. The second one was crushed into micrometer-sized grains onto a gold electron microscope grid held between two glass plates; they were observed at ONERA with a 400-kV Jeol 4000-FX transmission analytical electron microscope equipped with both a Kevex EDX system with a thin boron window, and a Gata electron energy loss spectrometer (EELS). It was shown four years ago (Maurette et al, 1989) that this procedure greatly reduces residual C contamination on the grains and allows measurements of their C/O ratios on a scale of ~1000 angstroms; (ii) In the second method polished sections of 50-100-micrometer-sized micrometeorites were run in Vienna with a Jeol 6400 SEM equipped with an EDX system similar to that of the 400-kV microscope. The first method was applied to ~200-micrometer-sized micrometeorites that had been heated more upon atmospheric entry than the 50-100-micrometer-sized grains analyzed with the second method. Our preliminary results are: (i) Comparisons with carbonaceous chondrites indicate that ~50% of the fine grained micrometeorites contain higher C/O ratios than Murchinson (CI chondrites should be run soon) (ii) Carbon appears as C-rich "hot" spots, where the C/O ratios occasionally reach unity (never observed yet in meteorites) that are superimposed on a rather homogeneous low-C matrix; (iii) On a scale of 10^-4 micrometer^3 comparisons between EDX and EELS spectra already show a variety of C-rich mineral phases, the dominant one being associated with some Mg-rich silicate; (iv) Some of the most C-rich micrometeorites belong to a family of light-colored particles that was overlooked in our previous studies, and that includes several new varieties of extraterrestrial "rocks." These "light" micrometeorites represent about 20% of the Cap-Prudhomme micrometeorite collection that is still dominated by "dark" particles. The second method (SEM+EDX) is only useful to spot the most C-rich and nonporous phases, which should be subsequently picked up for HVEM analyses. There appears to be present an odd "COPS" phase in about 20% of the ~50 fine-grained micrometeorites in which it was specifically searched for. This phase is typically partially filling up cavities and/or voids in a given particle. It is quite enriched in O, C, S, P, Si, and Fe and also contains measurable but variable amounts of minor elements including Ni, Cl, Ca, Cr, Na, and Zn. Scoria type vesicular micrometeorites, that have been partially melted, frequently contain this phase. If the COPS phase has indeed an extraterrestrial origin, it might have contributed to the formation of the characteristic vesicular texture of the scoria type particles, thus delineating a subset of "COPS"-rich micrometeoroids in the interplanetary medium. Carbon-rich micrometeorites might have individually functioned as microscopic "chondritic chemical reactor" for the synthesis of prebiotic molecules on the early Earth through the catalyzed hydrolysis of their C-rich components (Maurette et al., 1991). The COPS phase just reported in this paper might have contributed to the making of complex molecules. Acknowledgements. We thank A. Brack for helpful comments. REFERENCES Maurette M., Jouret C., Bonny Ph., Bradley J.P., and Germany M.S. (1989) Lunar Planet. Sci. (abstract) 20, 638-639. Maurette M., Bonny Ph., Brack A., Jouret C., Pourchet M., and Siry P. (1991) Lectures Notes in Physics 390, 124-132.

Synthesis and photocatalytic performance of g-C{sub 3}N{sub 4} nanosheets via liquid phase stripping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Jilin; Xu, Guangqing; Key Laboratory of Advanced Functional Materials and Devices of Anhui Province, Hefei University of Technology, Hefei 230009

Well dispersed g-C{sub 3}N{sub 4} nanosheets were prepared by exfoliating the bulk g-C{sub 3}N{sub 4} in concentrated sulfuric acid. Phase structures, morphologies and elemental compositions were characterized by X-ray diffractometer, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectrometer, respectively. Optical absorption and photoluminescence were also used to explain the optical performances of samples. NaI, BQ and IPA were used as the sacrificial agents for studying the surface reactions in the photocatalytic process. By the precipitation of g-C{sub 3}N{sub 4} nanosheets in ethanol with different ratios between concentrated sulfuric acid and ethyl alcohol, well dispersed g-C{sub 3}N{sub 4} nanosheetsmore » with high specific surface area can be obtained. The optimized g-C{sub 3}N{sub 4} (1:10) nanosheets achieve the highest photocatalytic activities under UV light illumination, which can degrade 10 mg/L RhB about 98% in 60 min, which is 6 times that of bulk g-C{sub 3}N{sub 4} under UV light. - Graphical Abstract: The schematic diagram of photocatalysis and excellent photocatalytic performance of g-C{sub 3}N{sub 4} nanosheets. - Highlights: • Well dispersed g-C{sub 3}N{sub 4} were prepared via Liquid Phase Stripping. • The g-C{sub 3}N{sub 4} is in a sheet like structure after being exfoliated. • The g-C{sub 3}N{sub 4} nanosheets possess high photocatalytic performances.« less

Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

PubMed

Wang, Ai-juan; Yuan, Zhi-long; Zhang, Jiao; Liu, Lin-tao; Li, Jun-ming; Liu, Zheng

2013-12-01

The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH2PO4 ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH2PO4 weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH2PO4 ratio might be explained by the existence of the weak phase KH2PO4. However, the low value of compressive strength with the higher MgO-to-KH2PO4 ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH2PO4 ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH2PO4 ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics. © 2013.

Self-amplified photo-induced gap quenching in a correlated electron material

PubMed Central

Mathias, S.; Eich, S.; Urbancic, J.; Michael, S.; Carr, A. V.; Emmerich, S.; Stange, A.; Popmintchev, T.; Rohwer, T.; Wiesenmayer, M.; Ruffing, A.; Jakobs, S.; Hellmann, S.; Matyba, P.; Chen, C.; Kipp, L.; Bauer, M.; Kapteyn, H. C.; Schneider, H. C.; Rossnagel, K.; Murnane, M. M.; Aeschlimann, M.

2016-01-01

Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. We show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically depends on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe2, our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains—on a microscopic level—the extremely fast response of this material to ultrafast optical excitation. PMID:27698341

Route to Coherent Electronics

NASA Astrophysics Data System (ADS)

Goulielmakis, Eleftherios

2017-04-01

Laser-driven generation of coherent radiation in bulk solids extending up to the extreme ultraviolet part of the spectrum has recently open up completely new possibilities for study of electronic phenomena which lie beyond the scope of standard condensed phase physics spectroscopies. I will present how previous and new tools of attosecond metrology can now allow us to gain detailed insight into the fundamental microscopic processes responsible for the EUV emission in solids. We will show that this emission is in reality a macroscopic probe of nanoscale intraband coherent electric currents the frequency of which is extending into multiPetahertz range. On the basis of these findings, I will try to persuade you that we are now entering the realm of coherent electronics. A regime in which electronic circuitry can be conceived on the atomic level and where electronic properties of materials can be accessed and controlled on attosecond time scales.

Transverse electron-scale instability in relativistic shear flows.

PubMed

Alves, E P; Grismayer, T; Fonseca, R A; Silva, L O

2015-08-01

Electron-scale surface waves are shown to be unstable in the transverse plane of a sheared flow in an initially unmagnetized collisionless plasma, not captured by (magneto)hydrodynamics. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroomlike electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. This transverse electron-scale instability may play an important role in relativistic and supersonic sheared flow scenarios, which are stable at the (magneto)hydrodynamic level. Macroscopic (≫c/ωpe) fields are shown to be generated by this microscopic shear instability, which are relevant for particle acceleration, radiation emission, and to seed magnetohydrodynamic processes at long time scales.

Electron backscatter diffraction studies of focused ion beam induced phase transformation in cobalt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, H.G., E-mail: helen.jones@npl.co.uk

A focused ion beam microscope was used to induce cubic to hexagonal phase transformation in a cobalt alloy, of similar composition to that of the binder phase in a hardmetal, in a controlled manner at 0°, 45° and 80° ion incident angles. The cobalt had an average grain size of ~ 20 μm, allowing multiple orientations to be studied, exposed to a range of doses between 6 × 10{sup 7} and 2 × 10{sup 10} ions/μm{sup 2}. Electron backscatter diffraction (EBSD) was used to determine the original and induced phase orientations, and area fractions, before and after the ion beammore » exposure. On average, less phase transformation was observed at higher incident angles and after lower ion doses. However there was an orientation effect where grains with an orientation close to (111) planes were most susceptible to phase transformation, and (101) the least, where grains partially and fully transformed at varying ion doses. - Highlights: •Ion-induced phase change in FCC cobalt was observed at multiple incidence angles. •EBSD was used to study the relationship between grain orientation and transformation. •Custom software analysed ion dose and phase change with respect to grain orientation. •A predictive capability of ion-induced phase change in cobalt was enabled.« less

Towards native-state imaging in biological context in the electron microscope

PubMed Central

Weston, Anne E.; Armer, Hannah E. J.

2009-01-01

Modern cell biology is reliant on light and fluorescence microscopy for analysis of cells, tissues and protein localisation. However, these powerful techniques are ultimately limited in resolution by the wavelength of light. Electron microscopes offer much greater resolution due to the shorter effective wavelength of electrons, allowing direct imaging of sub-cellular architecture. The harsh environment of the electron microscope chamber and the properties of the electron beam have led to complex chemical and mechanical preparation techniques, which distance biological samples from their native state and complicate data interpretation. Here we describe recent advances in sample preparation and instrumentation, which push the boundaries of high-resolution imaging. Cryopreparation, cryoelectron microscopy and environmental scanning electron microscopy strive to image samples in near native state. Advances in correlative microscopy and markers enable high-resolution localisation of proteins. Innovation in microscope design has pushed the boundaries of resolution to atomic scale, whilst automatic acquisition of high-resolution electron microscopy data through large volumes is finally able to place ultrastructure in biological context. PMID:19916039

Effect of heat treatment procedure on magnetic and magnetocaloric properties of Ni43Mn46In11 melt spun ribbons

NASA Astrophysics Data System (ADS)

Kaya, M.; Elerman, Y.; Dincer, I.

2018-07-01

The effect of heat treatment on the structural, magnetic and magnetocaloric properties of Ni43Mn46In11 melt-spun ribbons was systematically investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), magnetic force microscope (MFM) and magnetic measurements. From the XRD studies, tetragonal and cubic phases were detected at room temperature for as-spun, quenched and slow-cooled ribbons. Furthermore, it was observed, upon annealing martensite transition temperatures increased when compared to the as-spun ribbon. To avoid magnetic hysteresis losses in the vicinity of the structural transition region, the magnetic entropy changes-ΔS m of the investigated ribbons were evaluated from temperature-dependent magnetisation-M(T) curves on cooling for different applied magnetic fields. The maximum ΔS m value was found to be 6.79 J kg-1 K-1 for the quenched ribbon in the vicinity of structural transition region for a magnetic field change of 50 kOe.

Purchase of a Transmission Electron Microscope for Xavier University of Louisiana

DTIC Science & Technology

2015-05-15

imaging facility on the second floor of the Pharmacy Addition at Xavier University that already includes two scanning electron microscopes. The new TEM...is now in use. Xavier University has formally pledged to provide funds for the 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY...for Public Release; Distribution Unlimited Final Report: Purchase of a Transmission Electron Microscope for Xavier University of Louisiana The views

PSU/WES Interlaboratory Comparative Methodology Study of an Experimental Cementitious Repository Seal Material. Report 2. Final Results.

DTIC Science & Technology

1982-03-01

meter 25 11.0 Microstructure by SEM 11.1 Introduction In order to correlate observed physical and mechanical properties in cured grout samples, a...studied at the two laboratories has proper physical properties , phase composi- tions, and microstructures for the materials used and ages covered...Scanning Electron Microscope Resolution Test Specimen ( Al -W) D. B. Ballard Research Material 100 SEM Resolution Test Specimen (AI-W)., is an alloy of

Approach to Cultural Asset Preservation "Enzyme Filter Media Has Bactericidal Effect and Bacteriostasis Effect in Air Phase"

NASA Astrophysics Data System (ADS)

Isomae, Kazuro

Enzyme air-filter media according to the bactericidal effect as an environmental green technology acquired the high appraisal and the result in the domestic and foreign clean room and the air conditioning field. The mechanism of this enzyme technology, safety, and the bactericidal effect in the real environment are discussed by using the electron microscopic picture etc. And it proposes to apply these technologies to the cultural asset preservation.

Stripe order from the perspective of the Hubbard model

DOE PAGES

Huang, Edwin W.; Mendl, Christian B.; Jiang, Hong-Chen; ...

2018-04-20

A microscopic understanding of the strongly correlated physics of the cuprates must account for the translational and rotational symmetry breaking that is present across all cuprate families, commonly in the form of stripes. Here we investigate emergence of stripes in the Hubbard model, a minimal model believed to be relevant to the cuprate superconductors, using determinant quantum Monte Carlo (DQMC) simulations at finite temperatures and density matrix renormalization group (DMRG) ground state calculations. By varying temperature, doping, and model parameters, we characterize the extent of stripes throughout the phase diagram of the Hubbard model. Our results show that including themore » often neglected next-nearest-neighbor hopping leads to the absence of spin incommensurability upon electron-doping and nearly half-filled stripes upon hole-doping. The similarities of these findings to experimental results on both electron and hole-doped cuprate families support a unified description across a large portion of the cuprate phase diagram.« less

The human uterotubal junction: a scanning electron microscope study during different phases of the menstrual cycle.

PubMed

Fadel, H E; Berns, D; Zaneveld, L J; Wilbanks, G D; Brueschke, E E

1976-10-01

Uterotubal junctions from surgically extirpated human uteri were examined. The specimens were obtained during different phases of the menstrual cycle. The interstitial portions of the tubes together with the cornual areas were dissected, excised, and their luminal surfaces exposed. The specimens were then processed for scanning electron microscopy. The surface epithelium of both the cornual endometrium and interstitial endosalpins. Ciliated cells were more numerous in the endosalpinx. Cyclic changes in ciliated cells were minimal, while cyclic secretory activity was demonstrated, especially in the endometrium. The transitional area between the endometrium and the endosalpinx was characterized by a marked increase in the number of ciliated cells, and a tendency of the secretory cells to assume a flattened, polygonal shape. These morphologic features suggest a possible role in the transport and/or maintenance of spermatozoa and/or ova.

Red shifts of the Eg(1) Raman mode of nanocrystalline TiO2:Er monoliths grown by sol-gel process

NASA Astrophysics Data System (ADS)

Palomino-Merino, R.; Trejo-Garcia, P.; Portillo-Moreno, O.; Jiménez-Sandoval, S.; Tomás, S. A.; Zelaya-Angel, O.; Lozada-Morales, R.; Castaño, V. M.

2015-08-01

Nanocrystalline monoliths of Er doped TiO2 were prepared by the sol-gel technique, by controlling the Er-doping levels into the TiO2 precursor solution. As-prepared and annealed in air samples showed the anatase TiO2 phase. The average diameter of the nanoparticles ranged from 19 to 2.6 nm as the nominal concentration of Er varies from 0% to 7%, as revealed by EDS analysis in an electron microscope. Photo Acoustic Spectroscopy (PAS) allowed calculate the forbidden band gap, evidencing an absorption edge at around 300 nm, attributed to TiO2 and evidence of electronic transitions or Er3+. The Raman spectra, corresponding to the anatase phase, show the main phonon mode Eg(1) band position at 144 cm-1 with a red shift for the annealing samples.

Stripe order from the perspective of the Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Edwin W.; Mendl, Christian B.; Jiang, Hong-Chen

A microscopic understanding of the strongly correlated physics of the cuprates must account for the translational and rotational symmetry breaking that is present across all cuprate families, commonly in the form of stripes. Here we investigate emergence of stripes in the Hubbard model, a minimal model believed to be relevant to the cuprate superconductors, using determinant quantum Monte Carlo (DQMC) simulations at finite temperatures and density matrix renormalization group (DMRG) ground state calculations. By varying temperature, doping, and model parameters, we characterize the extent of stripes throughout the phase diagram of the Hubbard model. Our results show that including themore » often neglected next-nearest-neighbor hopping leads to the absence of spin incommensurability upon electron-doping and nearly half-filled stripes upon hole-doping. The similarities of these findings to experimental results on both electron and hole-doped cuprate families support a unified description across a large portion of the cuprate phase diagram.« less

Electron microscopy study of Ni induced crystallization in amorphous Si thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radnóczi, G. Z.; Battistig, G.; Pécz, B., E-mail: pecz.bela@ttk.mta.hu

2015-02-17

The crystallization of amorphous silicon is studied by transmission electron microscopy. The effect of Ni on the crystallization is studied in a wide temperature range heating thinned samples in-situ inside the microscope. Two cases of limited Ni source and unlimited Ni source are studied and compared. NiSi{sub 2} phase started to form at a temperature as low as 250°C in the limited Ni source case. In-situ observation gives a clear view on the crystallization of silicon through small NiSi{sub 2} grain formation. The same phase is observed at the crystallization front in the unlimited Ni source case, where a secondmore » region is also observed with large grains of Ni{sub 3}Si{sub 2}. Low temperature experiments show, that long annealing of amorphous silicon at 410 °C already results in large crystallized Si regions due to the Ni induced crystallization.« less

Estimation of dc transport dynamics in strongly correlated (La,Pr,Ca)MnO{sub 3} film using an insulator-metal composite model for terahertz conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, T. V. A.; Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531; Hattori, A. N.

2014-07-14

Temperature-dependent conductivities at dc and terahertz (THz) frequency region (σ{sub THz}(ω,T)) were obtained for a strongly correlated (La{sub 0.275}Pr{sub 0.35}Ca{sub 0.375})MnO{sub 3} (LPCMO) film using THz time domain spectroscopy. A composite model that describes σ{sub THz}(ω,T) for LPCMO through the insulator-metal transition (IMT) was established by incorporating Austin-Mott model characterizing the hopping of localized electrons and Drude model explaining the behavior of free electrons. This model enables us to reliably investigate the dc transport dynamics from THz conductivity measurement, i.e., simultaneously evaluate the dc conductivity and the competing composition of metal and insulator phases through the IMT, reflecting the changesmore » in microscopic conductivity of these phases.« less

Characterization of coarse bainite transformation in low carbon steel during simulated welding thermal cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, Liangyun, E-mail: lanly@me.neu.edu.cn; State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819; Kong, Xiangwei

2015-07-15

Coarse austenite to bainite transformation in low carbon steel under simulated welding thermal cycles was morphologically and crystallographically characterized by means of optical microscope, transmission electron microscope and electron backscattered diffraction technology. The results showed that the main microstructure changes from a mixture of lath martensite and bainitic ferrite to granular bainite with the increase in cooling time. The width of bainitic laths also increases gradually with the cooling time. For a welding thermal cycle with relatively short cooling time (e.g. t{sub 8/5} is 30 s), the main mode of variant grouping at the scale of individual prior austenite grainsmore » changes from Bain grouping to close-packed plane grouping with the progress of phase transformation, which results in inhomogeneous distribution of high angle boundaries. As the cooling time is increased, the Bain grouping of variants becomes predominant mode, which enlarges the effective grain size of product phase. - Highlights: • Main microstructure changes and the width of lath structure increases with cooling time. • Variant grouping changes from Bain zone to close-packed plane grouping with the transformation. • The change of variant grouping results in uneven distribution of high angle grain boundary. • Bain grouping is main mode for large heat input, which lowers the density of high angle boundary.« less

Influence of Capping Ligand and Synthesis Method on Structure and Morphology of Aqueous Phase Synthesized CuInSe2 Nanoparticles

NASA Astrophysics Data System (ADS)

Ram Kumar, J.; Ananthakumar, S.; Moorthy Babu, S.

2017-01-01

A facile route to synthesize copper indium diselenide (CuInSe2) nanoparticles in aqueous medium was developed using mercaptoacetic acid (MAA) as capping agent. Two different mole ratios (5 and 10) of MAA were used to synthesize CuInSe2 nanoparticles at room temperature, as well as hydrothermal (high temperature) method. Powder x-ray diffraction analysis reveals that the nanoparticles exhibit chalcopyrite phase and the crystallinity increases with increasing the capping ratio. Raman analysis shows a strong band at 233 cm-1 due to the combination of B2 (E) modes. Broad absorption spectra were observed for the synthesized CuInSe2 nanoparticles. The effective surface capping by MAA on the nanoparticles surface was confirmed through attenuated total reflection-Fourier transform infrared spectral analysis. The thermal stability of the synthesized samples was analyzed through thermogravimetric analysis-differential scanning calorimetry. The change in morphology of the synthesized samples was analyzed through scanning electron microscope and it shows that the samples prepared at room temperature are spherical in shape, whereas hydrothermally synthesized samples were found to have nanorod- and nanoflake-like structures. Transmission electron microscope analysis further indicates larger grains for the hydrothermally prepared samples with 10 mol ratio of MAA. Comparative analyses were made for synthesizing CuInSe2 nanoparticles by two different methods to explore the role of ligand and influence of temperature.

Widespread hydrothermal alteration minerals in the fine-grained matrices of the Tieschitz unequilibrated ordinary chondrite

NASA Astrophysics Data System (ADS)

Dobricǎ, E.; Brearley, A. J.

2014-08-01

Mineralogic, textural, and compositional studies of black and white matrices in the unequilibrated ordinary chondrite Tieschitz (H/L, 3.6) show, for the first time in an ordinary chondrite, the presence of widespread, randomly distributed geode-like voids and veins. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies show that these voids and veins are partially or completely filled by sodic-calcic amphiboles (winchite and barroisite). The occurrence of amphiboles provides unequivocal evidence of the involvement of fluids in the metamorphic evolution of the parent body of Tieschitz. The presence of amphiboles as the main hydrous phases, rather than phyllosilicates, indicates that aqueous fluids were present at or close to the peak of thermal metamorphism, rather than during the waning stages of the cooling history of the parent body. In addition, ferrous olivine crystals, in association with the amphibole, also establish an important link between thermal metamorphism and hydrous phases formed at high temperatures. Mineralogic and textural evidence suggests that the white matrix and amphibole formed contemporaneously from the same hydrous fluid, prior to the formation of ferrous olivine crystals. Additionally, a dark inclusion identified in the host chondrite has mineralogic, petrologic, and bulk chemical characteristics that are similar to the black matrix of host Tieschitz, suggesting that this dark inclusion was emplaced before or during parent body metamorphism.

Quantum Hall Valley Nematics: From Field Theories to Microscopic Models

NASA Astrophysics Data System (ADS)

Parameswaran, Siddharth

The interplay between quantum Hall ordering and spontaneously broken ``internal'' symmetries in two-dimensional electron systems with spin or pseudospin degrees of freedom gives rise to a variety of interesting phenomena, including novel phases, phase transitions, and topological excitations. I will discuss a theory of broken-symmetry quantum Hall states, applicable to a class of multivalley systems, where the symmetry at issue is a point-group element that combines a spatial rotation with a permutation of valley indices. I will explore its ramifications for the phase diagram of a variety of experimental systems, such as AlAs and Si quantum wells and the surface states of bismuth. I will also discuss unconventional transport phenomena in these phases in the presence of quenched randomness, and the possible mechanisms of selection between degenerate broken-symmetry phases in clean systems. I acknowledge support from NSF DMR-1455366.

High temperature Ir segregation in Ir-B ceramics: Effect of oxygen presence on stability of IrB 2 and other Ir-B phases

DOE PAGES

Xie, Zhilin; Terracciano, Anthony C.; Cullen, David A.; ...

2015-05-13

The formation of IrB 2, IrB 1.35, IrB 1.1 and IrB monoboride phases in the Ir–B ceramic nanopowder was confirmed during mechanochemical reaction between metallic Ir and elemental B powders. The Ir–B phases were analysed after 90 h of high energy ball milling and after annealing of the powder for 72 h at 1050°C in vacuo. The iridium monoboride (IrB) orthorhombic phase was synthesised experimentally for the first time and identified by powder X-ray diffraction. Additionally, the ReB 2 type IrB 2 hexagonal phase was also produced for the first time and identified by high resolution transmission electron microscope. Irmore » segregation along disordered domains of the boron lattice was found to occur during high temperature annealing. Furthermore, these nanodomains may have useful catalytic properties.« less

Use of an Annular Silicon Drift Detector (SDD) Versus a Conventional SDD Makes Phase Mapping a Practical Solution for Rare Earth Mineral Characterization.

PubMed

Teng, Chaoyi; Demers, Hendrix; Brodusch, Nicolas; Waters, Kristian; Gauvin, Raynald

2018-06-04

A number of techniques for the characterization of rare earth minerals (REM) have been developed and are widely applied in the mining industry. However, most of them are limited to a global analysis due to their low spatial resolution. In this work, phase map analyses were performed on REM with an annular silicon drift detector (aSDD) attached to a field emission scanning electron microscope. The optimal conditions for the aSDD were explored, and the high-resolution phase maps generated at a low accelerating voltage identify phases at the micron scale. In comparisons between an annular and a conventional SDD, the aSDD performed at optimized conditions, making the phase map a practical solution for choosing an appropriate grinding size, judging the efficiency of different separation processes, and optimizing a REM beneficiation flowsheet.

Materials considerations for forming the topological insulator phase in InAs/GaSb heterostructures

NASA Astrophysics Data System (ADS)

Shojaei, B.; McFadden, A. P.; Pendharkar, M.; Lee, J. S.; Flatté, M. E.; Palmstrøm, C. J.

2018-06-01

In an ideal InAs/GaSb bilayer of appropriate dimension, in-plane electron and hole bands overlap and hybridize, and a topologically nontrivial, or quantum spin Hall (QSH) insulator, phase is predicted to exist. The in-plane dispersion's potential landscape, however, is subject to microscopic perturbations originating from material imperfections. In this work, the effect of disorder on the electronic structure of InAs/GaSb (001) bilayers was studied by observing the temperature and magnetic-field dependence of the resistance of a dual-gated heterostructure gate-tuned through the inverted to normal gap regimes. Conduction with the electronic structure tuned to the inverted (predicted topological) regime and the Fermi level in the hybridization gap was qualitatively similar to behavior in a disordered two-dimensional system. The impact of charged impurities and interface roughness on the formation of topologically protected edge states and an insulating bulk was estimated. The experimental evidence and estimates of disorder in the potential landscape indicated that the potential fluctuations in state-of-the-art films are sufficiently strong such that conduction with the electronic structure tuned to the predicted topological insulator (TI) regime and the Fermi level in the hybridization gap was dominated by a symplectic metal phase rather than a TI phase. The implications are that future efforts must address disorder in this system, and focus must be placed on the reduction of defects and disorder in these heterostructures if a TI regime is to be achieved.

A reflection TIE system for 3D inspection of wafer structures

NASA Astrophysics Data System (ADS)

Yan, Yizhen; Qu, Weijuan; Yan, Lei; Wang, Zhaomin; Zhao, Hongying

2017-10-01

A reflection TIE system consisting of a reflecting microscope and a 4f relay system is presented in this paper, with which the transport of intensity equation (TIE) is applied to reconstruct the three-dimensional (3D) profile of opaque micro objects like wafer structures for 3D inspection. As the shape of an object can affect the phases of waves, the 3D information of the object can be easily acquired with the multiple phases at different refocusing planes. By electronically controlled refocusing, multi-focal images can be captured and used in solving TIE to obtain the phase and depth of the object. In order to validate the accuracy and efficiency of the proposed system, the phase and depth values of several samples are calculated, and the experimental results is presented to demonstrate the performance of the system.

The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

NASA Astrophysics Data System (ADS)

Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

2016-01-01

The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

Stripe order in the underdoped region of the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Zheng, Bo-Xiao; Chung, Chia-Min; Corboz, Philippe; Ehlers, Georg; Qin, Ming-Pu; Noack, Reinhard M.; Shi, Hao; White, Steven R.; Zhang, Shiwei; Chan, Garnet Kin-Lic

2017-12-01

Competing inhomogeneous orders are a central feature of correlated electron materials, including the high-temperature superconductors. The two-dimensional Hubbard model serves as the canonical microscopic physical model for such systems. Multiple orders have been proposed in the underdoped part of the phase diagram, which corresponds to a regime of maximum numerical difficulty. By combining the latest numerical methods in exhaustive simulations, we uncover the ordering in the underdoped ground state. We find a stripe order that has a highly compressible wavelength on an energy scale of a few kelvin, with wavelength fluctuations coupled to pairing order. The favored filled stripe order is different from that seen in real materials. Our results demonstrate the power of modern numerical methods to solve microscopic models, even in challenging settings.

Scanning electron microscopy of hepatic ultrastructure: secondary, backscattered, and transmitted electron imaging.

PubMed

Miyai, K; Abraham, J L; Linthicum, D S; Wagner, R M

1976-10-01

Several methods of tissue preparation and different modes of operation of the scanning electron microscope were used to study the ultrastructure of rat liver. Rat livers were perfusion fixed with buffered 2 per cent paraformaldehyde or a mixture of 1.5 per cent paraformaldehyde and 1 per cent glutaraldehyde and processed as follows. Tissue blocks were postfixed in buffered 2 per cent osmium tetroxide followed sequentially by the ligand-mediated osmium binding technique, dehydration and cryofracture in ethanol, and critical point drying. They were then examined without metal coating in the scanning electron microscope operating in the secondary electron and backscattered electron modes. Fifty-micrometer sections were cut with a tissue sectioner, stained with lead citrate, postfixed with osmium, dehydrated, critical point dried, and examined in the secondary electron and back-scattered electron modes. Frozen sections (0.25 to 0.75 mum. thick) were cut by the method of Tokuyasu (Toluyasu KT: J Cell Biol 57:551, 1973) and their scanning transmission electron microscope images were examined either with a scanning transmission electron microscope detector or with a conversion stub using the secondary electron detector. Secondary electron images of the liver prepared by ligand-mediated osmium binding and subsequent cryofracture revealed such intracellular structures as cisternae of the endoplasmic reticulum, lysosomes, mitochondria, lipid droplets, nucleolus and nuclear chromatin, as well as the usual surface morphology, Lipocytes in the perisinusoidal space were readily identified. Backscattered electron images. Unembedded frozen sections had little drying artifact and were virtually free of freezing damage. The scanning transmission electron microscope image revealed those organelles visualized by the secondary electron mode in the ligand-mediated osmium binding-treated tissue.

Wide-range high-resolution transmission electron microscopy reveals morphological and distributional changes of endomembrane compartments during log to stationary transition of growth phase in tobacco BY-2 cells.

PubMed

Toyooka, Kiminori; Sato, Mayuko; Kutsuna, Natsumaro; Higaki, Takumi; Sawaki, Fumie; Wakazaki, Mayumi; Goto, Yumi; Hasezawa, Seiichiro; Nagata, Noriko; Matsuoka, Ken

2014-09-01

Rapid growth of plant cells by cell division and expansion requires an endomembrane trafficking system. The endomembrane compartments, such as the Golgi stacks, endosome and vesicles, are important in the synthesis and trafficking of cell wall materials during cell elongation. However, changes in the morphology, distribution and number of these compartments during the different stages of cell proliferation and differentiation have not yet been clarified. In this study, we examined these changes at the ultrastructural level in tobacco Bright yellow 2 (BY-2) cells during the log and stationary phases of growth. We analyzed images of the BY-2 cells prepared by the high-pressure freezing/freeze substitution technique with the aid of an auto-acquisition transmission electron microscope system. We quantified the distribution of secretory and endosomal compartments in longitudinal sections of whole cells by using wide-range gigapixel-class images obtained by merging thousands of transmission electron micrographs. During the log phase, all Golgi stacks were composed of several thick cisternae. Approximately 20 vesicle clusters (VCs), including the trans-Golgi network and secretory vesicle cluster, were observed throughout the cell. In the stationary-phase cells, Golgi stacks were thin with small cisternae, and only a few VCs were observed. Nearly the same number of multivesicular body and small high-density vesicles were observed in both the stationary and log phases. Results from electron microscopy and live fluorescence imaging indicate that the morphology and distribution of secretory-related compartments dramatically change when cells transition from log to stationary phases of growth. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Effect of heat treatment on the microstructure of Co-Cr-W alloy fabricated by laser additive manufacturing

NASA Astrophysics Data System (ADS)

Ren, Bo; Chen, Changjun; Zhang, Min

2018-04-01

Stellite 6 cobalt-based alloy powder was used to produce Co-Cr-W alloy using laser additive manufacturing technology, and then different heat treatment strategies were carried out on the deposited sample. The characteristics of microstructure under different heat treatment conditions were investigated using scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscope, and x-ray diffraction. The results show that the as-deposited sample has few cracks or pores, and the microstructure is typical dendritic structure, and lamellar eutectic carbides are rich in Cr in interdendritic. The matrix mainly consists of γ phases and a few ɛ phases. Some γ phases transform into ɛ phases after 900°C/6 h aging treatment and lamellar eutectic carbides transform into blocky carbides presenting as a network, most of the carbides are rich in Cr and a few are rich in W. When heat treated at 1200°C/1 h followed by water cooling and then treated at 900°C/6 h followed by furnace cooling, it can be found that some γ phases transform into ɛ phases. The carbides transform into elliptical M23C6 carbides that are rich in Cr with the size of 1 to 3 μm and a part of W-rich carbides.

Transmission electron microscope analyses of alteration phases in martian meteorite MIL 090032

NASA Astrophysics Data System (ADS)

Hallis, L. J.; Ishii, H. A.; Bradley, J. P.; Taylor, G. J.

2014-06-01

The nakhlite group of martian meteorites found in the Antarctic contain varying abundances of both martian and terrestrial secondary alteration phases. The aim of this study was to use transmission electron microscopy (TEM) to compare martian and terrestrial alteration embodied within a single nakhlite martian meteorite find - MIL 090032. Martian alteration veins in MIL 090032 are composed of poorly ordered Fe-smectite phyllosilicate. This poorly-ordered smectite appears to be equivalent to the nanocrystalline phyllosilicate/hydrated amorphous gel phase previously described in the martian alteration veins of other nakhlites. Chemical differences in this nanocrystalline phyllosilicate between different nakhlites imply localised alteration, which occurred close to the martian surface in MIL 090032. Both structurally and compositionally the nakhlite nanocrystalline phyllosilicate shows similarities to the amorphous/poorly ordered phase recently discovered in martian soil by the Mars Curiosity Rover at Rocknest, Gale Crater. Terrestrially derived alteration phases in MIL 090032 include jarosite and gypsum, amorphous silicates, and Fe-oxides and hydroxides. Similarities between the mineralogy and chemistry of the MIL 090032 terrestrial and martian alteration phases suggest the alteration conditions on Mars were similar to those in the Antarctic. At both sites a small amount of fluid at low temperatures infiltrated the rock and became acidic as a result of the conversion of Fe2+ to Fe3+ under oxidising conditions.

Electron Microscope Center Opens at Berkeley.

ERIC Educational Resources Information Center

Robinson, Arthur L.

1981-01-01

A 1.5-MeV High Voltage Electron Microscope has been installed at the Lawrence Berkeley Laboratory which will help materials scientists and biologists study samples in more true-to-life situations. A 1-MeV Atomic Resolution Microscope will be installed at the same location in two years which will allow scientists to distinguish atoms. (DS)

Specimen Holder for Analytical Electron Microscopes

NASA Technical Reports Server (NTRS)

Clanton, U. S.; Isaacs, A. M.; Mackinnon, I.

1985-01-01

Reduces spectral contamination by spurious X-ray. Specimen holder made of compressed carbon, securely retains standard electron microscope grid (disk) 3 mm in diameter and absorbs backscattered electrons that otherwise generate spurious X-rays. Since holder inexpensive, dedicated to single specimen when numerous samples examined.

Improved phase sensitivity in spectral domain phase microscopy using line-field illumination and self phase-referencing

PubMed Central

Yaqoob, Zahid; Choi, Wonshik; Oh, Seungeun; Lue, Niyom; Park, Yongkeun; Fang-Yen, Christopher; Dasari, Ramachandra R.; Badizadegan, Kamran; Feld, Michael S.

2010-01-01

We report a quantitative phase microscope based on spectral domain optical coherence tomography and line-field illumination. The line illumination allows self phase-referencing method to reject common-mode phase noise. The quantitative phase microscope also features a separate reference arm, permitting the use of high numerical aperture (NA > 1) microscope objectives for high resolution phase measurement at multiple points along the line of illumination. We demonstrate that the path-length sensitivity of the instrument can be as good as 41 pm/Hz, which makes it suitable for nanometer scale study of cell motility. We present the detection of natural motions of cell surface and two-dimensional surface profiling of a HeLa cell. PMID:19550464

Measurement of flow speed in the channels of novel threadlike structures on the surfaces of mammalian organs

NASA Astrophysics Data System (ADS)

Sung, Baeckkyoung; Kim, Min Su; Lee, Byung-Cheon; Yoo, Jung Sun; Lee, Sang-Hee; Kim, Youn-Joong; Kim, Ki-Woo; Soh, Kwang-Sup

2008-02-01

There have been several reports on novel threadlike structures (NTSs) on the surfaces of the internal organs of rats and rabbits since their first observation by Bonghan Kim in 1963. To confirm this novel circulatory function, it is necessary to observe the flow of liquid through the NTS as well as the structurally corroborating channels in the NTS. In this article, we report on the measurement of the flow speed of Alcian blue solution in the NTSs on the organ surfaces of rabbits, and we present electron microscopic images depicting the cribrous cross-section with channels. The speed was measured as 0.3 ± 0.1 mm/s, and the flow distance was up to 12 cm. The flow was unidirectional, and the phase contrast microscopic images showed that the NTSs were strongly stained with Alcian blue. The ultrastructure of the NTSs revealed by cryo-scanning electron microscopy and high-voltage electron microscopy showed that (1) there were cell-like bodies and globular clumps of matter inside the sinus of the channel with thin strands of segregated zones which is a microscopic evidence of the liquid flow, (2) the sinuses have wall structures surrounded with extracellular matrices of collagenous fibers, and (3) there exists a cribriform structure of sinuses. To understand the mechanism for the circulation, a quantitative analysis of the flow speed has been undertaken applying a simplified windkessel model. In this analysis, it was shown that the liquid flow through the NTSs could be due to peristaltic motion of the NTS itself.

Simultaneous specimen and stage cleaning device for analytical electron microscope

DOEpatents

Zaluzec, Nestor J.

1996-01-01

An improved method and apparatus are provided for cleaning both a specimen stage, a specimen and an interior of an analytical electron microscope (AEM). The apparatus for cleaning a specimen stage and specimen comprising a plasma chamber for containing a gas plasma and an air lock coupled to the plasma chamber for permitting passage of the specimen stage and specimen into the plasma chamber and maintaining an airtight chamber. The specimen stage and specimen are subjected to a reactive plasma gas that is either DC or RF excited. The apparatus can be mounted on the analytical electron microscope (AEM) for cleaning the interior of the microscope.

Development of a SEM-based low-energy in-line electron holography microscope for individual particle imaging.

PubMed

Adaniya, Hidehito; Cheung, Martin; Cassidy, Cathal; Yamashita, Masao; Shintake, Tsumoru

2018-05-01

A new SEM-based in-line electron holography microscope has been under development. The microscope utilizes conventional SEM and BF-STEM functionality to allow for rapid searching of the specimen of interest, seamless interchange between SEM, BF-STEM and holographic imaging modes, and makes use of coherent low-energy in-line electron holography to obtain low-dose, high-contrast images of light element materials. We report here an overview of the instrumentation and first experimental results on gold nano-particles and carbon nano-fibers for system performance tests. Reconstructed images obtained from the holographic imaging mode of the new microscope show substantial image contrast and resolution compared to those acquired by SEM and BF-STEM modes, demonstrating the feasibility of high-contrast imaging via low-energy in-line electron holography. The prospect of utilizing the new microscope to image purified biological specimens at the individual particle level is discussed and electron optical issues and challenges to further improve resolution and contrast are considered. Copyright © 2018 Elsevier B.V. All rights reserved.

Phase Equilibria and Magnetic Phases in the Ce-Fe-Co-B System

PubMed Central

Wang, Tian; Kevorkov, Dmytro; Medraj, Mamoun

2016-01-01

Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS), and Magnetic Force Microscope (MFM) is used in this research to understand the phase equilibria and to explore promising magnetic phases in this system. Three magnetic phases were detected and their homogeneity ranges were determined at 900 °C, which were presented by the formulae: Ce2Fe14−xCoxB (0 ≤ x ≤ 4.76), CeCo4−xFexB (0 ≤ x ≤ 3.18), and Ce3Co11−x FexB4 (0 ≤ x ≤ 6.66). The phase relations among the magnetic phases in this system have been studied. Ce2(Fe, Co)14B appears to have stronger magnetization than Ce(Co, Fe)4B and Ce3(Co, Fe)11B4 from MFM analysis when comparing the magnetic interactions of selected key alloys. Also, a non-magnetic CeCo12−xFexB6 (0 ≤ x ≤ 8.74) phase was detected in this system. A boron-rich solid solution with Ce13FexCoyB45 (32 ≤ x ≤ 39, 3 ≤ y ≤ 10) chemical composition was also observed. However, the crystal structure of this phase could not be found in the literature. Moreover, ternary solid solutions ε1 (Ce2Fe17−xCox (0 ≤ x ≤ 12.35)) and ε2 (Ce2Co17−xFex (0 ≤ x ≤ 3.57)) were found to form between Ce2Fe17 and Ce2Co17 in the Ce-Fe-Co ternary system at 900 °C. PMID:28772374

Improved specimen reconstruction by Hilbert phase contrast tomography.

PubMed

Barton, Bastian; Joos, Friederike; Schröder, Rasmus R

2008-11-01

The low signal-to-noise ratio (SNR) in images of unstained specimens recorded with conventional defocus phase contrast makes it difficult to interpret 3D volumes obtained by electron tomography (ET). The high defocus applied for conventional tilt series generates some phase contrast but leads to an incomplete transfer of object information. For tomography of biological weak-phase objects, optimal image contrast and subsequently an optimized SNR are essential for the reconstruction of details such as macromolecular assemblies at molecular resolution. The problem of low contrast can be partially solved by applying a Hilbert phase plate positioned in the back focal plane (BFP) of the objective lens while recording images in Gaussian focus. Images recorded with the Hilbert phase plate provide optimized positive phase contrast at low spatial frequencies, and the contrast transfer in principle extends to the information limit of the microscope. The antisymmetric Hilbert phase contrast (HPC) can be numerically converted into isotropic contrast, which is equivalent to the contrast obtained by a Zernike phase plate. Thus, in-focus HPC provides optimal structure factor information without limiting effects of the transfer function. In this article, we present the first electron tomograms of biological specimens reconstructed from Hilbert phase plate image series. We outline the technical implementation of the phase plate and demonstrate that the technique is routinely applicable for tomography. A comparison between conventional defocus tomograms and in-focus HPC volumes shows an enhanced SNR and an improved specimen visibility for in-focus Hilbert tomography.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yashchuk, V. V., E-mail: VVYashchuk@lbl.gov; Chan, E. R.; Lacey, I.

We present a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) one-dimensional sequences and two-dimensional arrays as an effective method for spectral characterization in the spatial frequency domain of a broad variety of metrology instrumentation, including interferometric microscopes, scatterometers, phase shifting Fizeau interferometers, scanning and transmission electron microscopes, and at this time, x-ray microscopes. The inherent power spectral density of BPR gratings and arrays, which has a deterministic white-noise-like character, allows a direct determination of the MTF with a uniform sensitivity over the entire spatial frequency range and field of view of an instrument. We demonstrate themore » MTF calibration and resolution characterization over the full field of a transmission soft x-ray microscope using a BPR multilayer (ML) test sample with 2.8 nm fundamental layer thickness. We show that beyond providing a direct measurement of the microscope’s MTF, tests with the BPRML sample can be used to fine tune the instrument’s focal distance. Our results confirm the universality of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.« less

Electron tomography simulator with realistic 3D phantom for evaluation of acquisition, alignment and reconstruction methods.

PubMed

Wan, Xiaohua; Katchalski, Tsvi; Churas, Christopher; Ghosh, Sreya; Phan, Sebastien; Lawrence, Albert; Hao, Yu; Zhou, Ziying; Chen, Ruijuan; Chen, Yu; Zhang, Fa; Ellisman, Mark H

2017-05-01

Because of the significance of electron microscope tomography in the investigation of biological structure at nanometer scales, ongoing improvement efforts have been continuous over recent years. This is particularly true in the case of software developments. Nevertheless, verification of improvements delivered by new algorithms and software remains difficult. Current analysis tools do not provide adaptable and consistent methods for quality assessment. This is particularly true with images of biological samples, due to image complexity, variability, low contrast and noise. We report an electron tomography (ET) simulator with accurate ray optics modeling of image formation that includes curvilinear trajectories through the sample, warping of the sample and noise. As a demonstration of the utility of our approach, we have concentrated on providing verification of the class of reconstruction methods applicable to wide field images of stained plastic-embedded samples. Accordingly, we have also constructed digital phantoms derived from serial block face scanning electron microscope images. These phantoms are also easily modified to include alignment features to test alignment algorithms. The combination of more realistic phantoms with more faithful simulations facilitates objective comparison of acquisition parameters, alignment and reconstruction algorithms and their range of applicability. With proper phantoms, this approach can also be modified to include more complex optical models, including distance-dependent blurring and phase contrast functions, such as may occur in cryotomography. Copyright © 2017 Elsevier Inc. All rights reserved.

75 FR 43918 - National Center for Toxicological Research, et al.; Notice of Consolidated Decision on...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-27

... Research, et al.; Notice of Consolidated Decision on Applications for Duty-Free Entry of Electron...: National Center for Toxicological Research, (USFDA), Jefferson, AK 72079. Instrument: Electron Microscope.... Applicant: University of Virginia, Charlottesville, VA 22903. Instrument: Electron Microscope. Manufacturer...

Asymmetric Marcus-Hush theory for voltammetry.

PubMed

Laborda, Eduardo; Henstridge, Martin C; Batchelor-McAuley, Christopher; Compton, Richard G

2013-06-21

The current state-of-the-art in modeling the rate of electron transfer between an electroactive species and an electrode is reviewed. Experimental studies show that neither the ubiquitous Butler-Volmer model nor the more modern symmetric Marcus-Hush model are able to satisfactorily reproduce the experimental voltammetry for both solution-phase and surface-bound redox couples. These experimental deviations indicate the need for revision of the simplifying approximations used in the above models. Within this context, models encompassing asymmetry are considered which include different vibrational and solvation force constants for the electroactive species. The assumption of non-adiabatic electron transfer is also examined. These refinements have provided more satisfactory models of the electron transfer process and they enable us to gain more information about the microscopic characteristics of the system by means of simple electrochemical measurements.

The Proposed Doppler Electron Velocimeter and the Need for Nanoscale Dynamics

DOE PAGES

Reu, Phillip L.

2007-05-01

As engineering challenges grow in the ever-shrinking world of nano-design, methods of making dynamic measurements of nano-materials and systems become more important. The Doppler electron velocimeter (DEV) is a new measurement concept motivated by the increasing importance of nano-dynamics. Nano-dynamics is defined in this context as any phenomenon that causes a dynamically changing phase in an electron beam, and includes traditional mechanical motion, as well as additional phenomena including changing magnetic and electric fields. The DEV is only a theoretical device at this point. Lastly, this article highlights the importance of pursuing nano-dynamics and presents a case that the electronmore » microscope and its associated optics are a viable test bed to develop this new measurement tool.« less

In-situ synthesis of Co3O4/graphite nanocomposite for high-performance supercapacitor electrode applications

NASA Astrophysics Data System (ADS)

Gopalakrishnan, M.; Srikesh, G.; Mohan, A.; Arivazhagan, V.

2017-05-01

In this work, a low cost and pollution free in-situ synthesis of phase pure Co3O4 nanoparticles and Co3O4/graphite nanocomposite have been successfully developed via co-precipitation method followed by the thermal treatment process. The prepared samples were characterized by powder X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, Fourier Transform Infrared Spectroscopy and electrochemical measurements. Electrochemical measurements such as cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy were carried out in 6 M KOH aqueous electrolytic solution. The results show the excellent maximum specific capacitive behavior of 239.5 F g-1 for pure and 395.04 F g-1 for Co3O4/graphite nanocomposite at a current density of 0.5 A g-1. This composite exhibits a good cyclic stability, with a small loss of 2.68% of maximum capacitance over a consecutive 1000 cycles. The investigation indicates that the prepared electrode material could be a potential and promising candidate for electrochemical supercapacitors.

The microscopic structure of charge density waves in underdoped YBa 2Cu 3O 6.54 revealed by x-ray diffraction

DOE PAGES

E. M. Forgan; Huecker, M.; Blackburn, E.; ...

2015-12-09

Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa 2Cu 3O 6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO 2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO 2 planes, and are out of phase with each other. The planar oxygen atomsmore » have the largest displacements, perpendicular to the CuO 2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For example, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.« less

Charge collection microscopy of in-situ switchable PRAM line cells in a scanning electron microscope: Technique development and unique observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oosthoek, J. L. M.; Schuitema, R. W.; Brink, G. H. ten

2015-03-15

An imaging method has been developed based on charge collection in a scanning electron microscope (SEM) that allows discrimination between the amorphous and crystalline states of Phase-change Random Access Memory (PRAM) line cells. During imaging, the cells are electrically connected and can be switched between the states and the resistance can be measured. This allows for electrical characterization of the line cells in-situ in the SEM. Details on sample and measurement system requirements are provided which turned out to be crucial for the successful development of this method. Results show that the amorphous or crystalline state of the line cellsmore » can be readily discerned, but the spatial resolution is relatively poor. Nevertheless, it is still possible to estimate the length of the amorphous mark, and also for the first time, we could directly observe the shift of the amorphous mark from one side of the line cell to the other side when the polarity of the applied (50 ns) RESET pulse was reversed.« less

Microstructural and thermal study of Al-Si-Mg/melon shell ash particulate composite

NASA Astrophysics Data System (ADS)

Abdulwahab, M.; Umaru, O. B.; Bawa, M. A.; Jibo, H. A.

The microstructural study via scanning electron microscope (SEM) and thermal study via differential scanning calorimetric (DSC) study of Al-7%Si-0.3Mg/melon shell ash particulate composite has been carried out. The melon shell ash was used in the production of MMC ranging from 5% to 20% at interval of 5% addition using stir casting method. The melon shell ash was characterized using X-ray fluorescent (XRF) that reveal the presence of CaO, SiO2, Al2O3, MgO, and TiO2 as major compounds. The composite was machined and subjected to heat treatment. Microstructural analyses of the composite produced were done using scanning electron microscope (SEM). The microstructure obtained reveals a dark ceramic (reinforcer) and white metallic phase. Equally, the 5 wt% DSC result gives better thermal conductivity than other proportions (10 wt%, 15 wt%, and 20 wt%). These results showed that an improved property of Al-Si-Mg alloy was achieved using melon shell ash particles as reinforcement up to a maximum of 20 wt% for microstructural and 5% wt DSC respectively.

Taspine isolated from Radix et Rhizoma Leonticis inhibits growth of human umbilical vein endothelial cell (HUVEC) by inducing its apoptosis.

PubMed

Zhang, Yanmin; He, Langchong; Zhou, Yali

2008-01-01

The present study was to evaluate the effects of taspine isolated from Radix et Rhizoma Leonticsi on the growth and apoptosis of human umbilical vein endothelial cell (HUVEC) line by MTT and flow cytometer, respectively. At the same time, a series of changes were observed in HUVEC treated by taspine, including microstructure, protein expression of bax, bcl-2 and VEGF. The change of microstructure was observed by transmission electron microscope (TEM). The protein expression of bax and bcl-2 was detected by immunohistochemistry (IHC), and VEGF protein secreted was determined by enzyme-linked immunosorbent assay (ELISA). The results showed taspine could inhibit growth and induce apoptosis of HUVEC in a dose-dependent manner. Cell cycle was significantly stopped at the S phase. Under electronic microscope, the morphology of HUVEC treated with taspine showed nuclear karyopycnosis, chromatin agglutination and typical apoptotic body. Bcl-2 and VEGF expressions were decreased and bax expression was increased. All these results demonstrate that taspine has an inhibitory effect on growth of HUVEC and can induce its apoptosis.

The microscopic structure of charge density waves in underdoped YBa2Cu3O6.54 revealed by X-ray diffraction

NASA Astrophysics Data System (ADS)

Forgan, E. M.; Blackburn, E.; Holmes, A. T.; Briffa, A. K. R.; Chang, J.; Bouchenoire, L.; Brown, S. D.; Liang, Ruixing; Bonn, D.; Hardy, W. N.; Christensen, N. B.; Zimmermann, M. V.; Hücker, M.; Hayden, S. M.

2015-12-01

Charge density wave (CDW) order appears throughout the underdoped high-temperature cuprate superconductors, but the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDWs in an archetypical cuprate YBa2Cu3O6.54 at its superconducting transition temperature ~60 K. We find that the CDWs in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in the CDWs have two components, which are perpendicular and parallel to the CuO2 planes, and are out of phase with each other. The planar oxygen atoms have the largest displacements, perpendicular to the CuO2 planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For instance, the CDWs will lead to local variations in the electronic structure, giving an explicit explanation of density-wave states with broken symmetry observed in scanning tunnelling microscopy and soft X-ray measurements.

Tomographic imaging of transparent biological samples using the pyramid phase microscope

PubMed Central

Iglesias, Ignacio

2016-01-01

We show how a pyramid phase microscope can be used to obtain tomographic information of the spatial variation of refractive index in biological samples using the Radon transform. A method that uses the information provided by the phase microscope for axial and lateral repositioning of the sample when it rotates is also described. Its application to the reconstruction of mouse embryos in the blastocyst stage is demonstrated. PMID:27570696

Scanning Electron Microscope Observations of Marine Microorganisms on Surfaces Coated with Antifouling Paints.

DTIC Science & Technology

1981-06-01

sessile marine inverte- brates in Monterey harbor. Veliger 17 (supplement): 1-35. 1977. The nature of primary organic films in the marine environment and...I A10A4h 605 NAVAL POSTGRADUATE SCHOOL MONTEREY CA F/S 11/3 SCANING ELECTRON MICROSCOPE OBSERVATIONS OF MARINE MICROORANI-E-C(U) UNLSSIFIED N*2...Scanning Electron Microscope Observations Master’s thesis; of Marine Microorganisms on Surfaces June 1981 Coated with Ant ifouling Paints 6.PERFORMING

Electron microscope aperture system

NASA Technical Reports Server (NTRS)

Heinemann, K. (Inventor)

1976-01-01

An electron microscope including an electron source, a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen, and an objective lens having an annular objective aperture, for focusing electrons passing through the specimen onto an image plane are described. The invention also entails a method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques.

Interfacial Microstructure and Mechanical Properties of Friction Stir Welded Joints of Commercially Pure Aluminum and 304 Stainless Steel

NASA Astrophysics Data System (ADS)

Murugan, Balamagendiravarman; Thirunavukarasu, Gopinath; Kundu, Sukumar; Kailas, Satish V.; Chatterjee, Subrata

2018-05-01

In the present investigation, friction stir welding of commercially pure aluminum and 304 stainless steel was carried out at varying tool rotational speeds from 200 to 1000 rpm in steps of 200 rpm using 60 mm/min traverse speed at 2 (degree) tool tilt angle. Microstructural characterization of the interfacial zone was carried out using optical microscope and scanning electron microscope. Energy-dispersive spectroscopy indicated the presence of FeAl3 intermetallic phase. Thickness of the intermetallic layer increased with the increase in tool rotational speed. X-ray diffraction studies indicated the formation of intermetallic phases like FeAl2, Fe4Al13, Fe2Al5, and FeAl3. A maximum tensile strength of 90% that of aluminum along with 4.5% elongation was achieved with the welded sample at tool rotational speed of 400 rpm. The stir zone showed higher hardness as compared to base metals, heat affected zone, and thermo-mechanically affected zone due to the presence of intermetallics. The maximum hardness value at the stir zone was achieved at 1000 rpm tool rotational speed.

Automated SEM Modal Analysis Applied to the Diogenites

NASA Technical Reports Server (NTRS)

Bowman, L. E.; Spilde, M. N.; Papike, James J.

1996-01-01

Analysis of volume proportions of minerals, or modal analysis, is routinely accomplished by point counting on an optical microscope, but the process, particularly on brecciated samples such as the diogenite meteorites, is tedious and prone to error by misidentification of very small fragments, which may make up a significant volume of the sample. Precise volume percentage data can be gathered on a scanning electron microscope (SEM) utilizing digital imaging and an energy dispersive spectrometer (EDS). This form of automated phase analysis reduces error, and at the same time provides more information than could be gathered using simple point counting alone, such as particle morphology statistics and chemical analyses. We have previously studied major, minor, and trace-element chemistry of orthopyroxene from a suite of diogenites. This abstract describes the method applied to determine the modes on this same suite of meteorites and the results of that research. The modal abundances thus determined add additional information on the petrogenesis of the diogenites. In addition, low-abundance phases such as spinels were located for further analysis by this method.

Magnetostructural Properties of Colossal Magnetoresistance Manganites Under External Magnetic Fields and Uniaxial Pressure

NASA Astrophysics Data System (ADS)

Kaplan, Michael; Zimmerman, George

2002-03-01

In the colossal magnetoresistance manganites the transport and magnetostructural properties are tightly connected [1,2]. Many magnetic field induced structural phase transitions and anomalous magnetoacoustical properties continue to be discovered in various manganite derivatives. Nevertheless the mechanism of structural transitions and microscopic theory of corresponding anomalous properties are still to be completely understood. Here we present a microscopic model of magnetic field and uniaxial pressure induced structural phase transitions in lightly doped manganites. The model is based on the cooperative Jahn-Teller effect which takes into account the Mn3+-ground doublet and excited triplet electronic states. Numerous calculations for different orientation magnetic field suggest the explanations of the origin of the structural transitions and of the measured magnetostriction data. The calculations for the two-sublattice antiferrodistortive crystals under uniaxial pressure support the idea of metaelasticity - a property typical for Jahn-Teller antiferroelastics. 1.Y. Tokura, ed. Colossal Magnetoresistance Oxides. Gordon & Breach, London, 2000. 2.M. Kaplan, G. Zimmerman, eds. Vibronic Interactions: Jahn-Teller Effect in Crystal and Molecules. NATO Science Series, Dordrecht/Boston/London, 2001

Choice and maintenance of equipment for electron crystallography.

PubMed

Mills, Deryck J; Vonck, Janet

2013-01-01

The choice of equipment for an electron crystallography laboratory will ultimately be determined by the available budget; nevertheless, the ideal lab will have two electron microscopes: a dedicated 300 kV cryo-EM with a field emission gun and a smaller LaB(6) machine for screening. The high-end machine should be equipped with photographic film or a very large CCD or CMOS camera for 2D crystal data collection; the screening microscope needs a mid-size CCD for rapid evaluation of crystal samples. The microscope room installations should provide adequate space and a special environment that puts no restrictions on the collection of high-resolution data. Equipment for specimen preparation includes a carbon coater, glow discharge unit, light microscope, plunge freezer, and liquid nitrogen containers and storage dewars. When photographic film is to be used, additional requirements are a film desiccator, dark room, optical diffractometer, and a film scanner. Having the electron microscopes and ancillary equipment well maintained and always in optimum condition facilitates the production of high-quality data.

Vibrational spectroscopy in the electron microscope.

PubMed

Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Aoki, Toshihiro; Carpenter, R W; Rez, Peter; Soignard, Emmanuel; Zhu, Jiangtao; Batson, Philip E; Lagos, Maureen J; Egerton, Ray F; Crozier, Peter A

2014-10-09

Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.

Ultrastructural Study of Some Pollen Grains of Prairie Flowers

ERIC Educational Resources Information Center

Kozar, Frank

1973-01-01

Discusses the importance of the electron microscope, and in particular the scanning electron microscope, in studying the surface topography, sectional substructures, and patterns of development of pollen grains. The production, dispersal methods, and structure of pollen grains are described and illustrated with numerous electron micrographs. (JR)

PVP capped CdS nanoparticles for UV-LED applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivaram, H.; Selvakumar, D.; Jayavel, R., E-mail: rjvel@annauniv.edu

Polyvinlypyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles are synthesized by wet chemical method. The powder X-ray diffraction (XRD) result indicates that the nanoparticles are crystallized in cubic phase. The optical properties are characterized by UV-Vis absorption. The morphology of CdS nanoparticles are studied using Scanning electron microscope (SEM). The thermal behavior of the as prepared nanoparticles has been examined by Thermo gravimetric analysis (TGA). The optical absorption study of pvp capped CdS reveal a red shift confirms the UV-LED applications.

Studies of Brazilian meteorites. XIV - Mineralogy, petrology, and chemistry of the Conquista, Minas Gerais, chondrite

NASA Technical Reports Server (NTRS)

Keil, K.; Kirchner, E.; Gomes, C. B.; Jarosewich, E.; Murta, R. L. L.

1978-01-01

The Conquista chondrite is described and classified as an H4. The mineral composition is reported. H-group classification is based on described microscopic, electron microprobe, and bulk chemical studies. The evidence for petrologic type 4 classification includes the pronounced well-developed chondritic texture; the slight compositional variations in constituent phases; the high Ca contents of pyroxene and the presence of pigeonite; glassy to microcrystalline interstitial material rich in alkalis and SiO2; and twinned low-Ca clinopyroxene.

In situ straining investigation of slip transfer across α2 lamellae at room temperature in a lamellar TiAl alloy

NASA Astrophysics Data System (ADS)

Singh, J. B.; Molénat, G.; Sundararaman, M.; Banerjee, S.; Saada, G.; Veyssière, P.; Couret, A.

2006-01-01

Processes by which deformation spreads throughout a lamellar TiAl alloy have been investigated by in situ tensile experiments performed at room temperature in a transmission electron microscope. Several situations are found and analysed in which dislocations cross the ?/a2 interfaces and the a2 lamellae - the hard phase of the structure. Conditions by which strain transfer can be elastically mediated across sufficiently thin a2 lamellae are discussed.

Vestibular receptor cells and signal detection: bioaccelerometers and the hexagonal sampling of two-dimensional signals

NASA Technical Reports Server (NTRS)

Mugler, D. H.; Ross, M. D.

1990-01-01

The inner ear contains sensory organs which signal changes in head movement. The vestibular sacs, in particular, are sensitive to linear accelerations. Electron microscopic images have revealed the structure of tiny sensory hair bundles, whose mechanical deformation results in the initiation of neuronal activity and the transmission of electrical signals to the brain. The structure of the hair bundles is shown in this paper to be that of the most efficient two-dimensional phased-array signal processors.

Effect of Continuous and Pulsed Current Gas Tungsten Arc Welding on Dissimilar Weldments Between Hastelloy C-276/AISI 321 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Sharma, Sumitra; Taiwade, Ravindra V.; Vashishtha, Himanshu

2017-03-01

In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.

Thickness-dependent multiferroic behavior of BiFe0.75Cr0.25O3 films over Pt(111)/Ti/SiO2/Si substrate

NASA Astrophysics Data System (ADS)

William, R. V.; Sivaprakash, P.; Marikani, A.; Reddy, V. Raghavendra; Arumugam, S.

2018-02-01

We present here the experimental results of BiFe0.75Cr0.25O3 (BFCO) thin film deposited by sol-gel spin coating technique directly on Pt(111)/Ti/SiO2/Si substrate at different thicknesses. The crystal structure of BFCO has been investigated using X-ray diffraction which acts as a double perovskite structure with high crystallinity obtained at 400 °C. Further microscopic studies such as scanning electron microscope (SEM) with EDAX, transmission electron microscope (TEM) were also used in identifying the grain size and particle distribution over Pt (111) substrate. Atomic force microscopy (AFM) on the films at a different thickness (- 80 to - 250 nm) reveals that the surface roughness and other amplitude parameters increases with the increase in thickness signifying an increase of grain size with thickness. Increase in grain size and substrate clamping effect between the BFCO film and the substrate induces change in ferroelectric polarization and dielectric properties in relation to thickness effect. Similarly, decrease in magnetization from 9.241 emu/cm3 (- 80 nm) to 5.7791 emu/cm3 (- 250 nm) is attributed to the formation of anti-sites and anti-phase boundaries in the films. In addition, temperature dependence of magnetization reveals ferromagnetic super-exchange interaction of BFCO which is unlike the spin structure of antiferromagnetic BiFeO3.

Synthesis Properties and Electron Spin Resonance Properties of Titanic Materials (abstract)

NASA Astrophysics Data System (ADS)

Cho, Jung Min; Lee, Jun; Kim, Tak Hee; Sun, Min Ho; Jang, Young Bae; Cho, Sung June

2009-04-01

Titanic materials were synthesized by hydrothermal method of TiO2 anatase in 10M LiOH, 10M NaOH, and 14M KOH at 130° C for 30 hours. Alkaline media were removed from the synthesized products using 0.1N HCl aqueous solution. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, Brunauer-Emmett-Teller isotherm, and electron spin resonance. Different shapes of synthesized products were observed through the typical electron microscope and indicated that the formation of the different morphologies depends on the treatment conditions of highly alkaline media. Many micropores were observed in the cubic or octahedral type of TiO2 samples through the typical electron microscope and Langmuir adsorption-desorption isotherm of liquid nitrogen at 77° K. Electron spin resonance studies have also been carried out to verify the existence of paramagnetic sites such as oxygen vacancies on the titania samples. The effect of alkali metal ions on the morphologies and physicochemical properties of nanoscale titania are discussed.

Microstructure and Mechanical Properties of Stainless Steel/Brass Joints Brazed by Sn-Electroplated Ag Brazing Filler Metals

NASA Astrophysics Data System (ADS)

Wang, Xingxing; Peng, Jin; Cui, Datian

2018-05-01

To develop a high-Sn-content AgCuZnSn brazing filler metal, the BAg50CuZn was used as the base filler metal and a Sn layer was electroplated upon it. Then, the 304 stainless steel and the H62 brass were induction-brazed with the Sn-plated brazing filler metals. The microstructures of the joints were examined with an optical microscope, a scanning electron microscope and an x-ray diffractometer. The corresponding mechanical properties were obtained with a universal tensile testing machine. The results indicated that the induction brazed joints consisted of the Ag phase, the Cu phase and the CuZn phase. When the content of Sn in the Sn-plated Ag brazing filler metal was 6.0 or 7.2 wt.%, the Cu5Zn8, the Cu41Sn11 and the Ag3Sn phases appeared in the brazed joint. The tensile strength of the joints brazed with the Sn-plated filler metal was higher compared to the joints with the base filler metal. When the content of Sn was 6.0 wt.%, the highest tensile strength of the joint reached to 395 MPa. The joint fractures presented a brittle mode, mixed with a low amount of ductile fracture, when the content of Sn exceeded 6.0 wt.%.

Design and performance of a beetle-type double-tip scanning tunneling microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaschinsky, Philipp; Coenen, Peter; Pirug, Gerhard

2006-09-15

A combination of a double-tip scanning tunneling microscope with a scanning electron microscope in ultrahigh vacuum environment is presented. The compact beetle-type design made it possible to integrate two independently driven scanning tunneling microscopes in a small space. Moreover, an additional level for coarse movement allows the decoupling of the translation and approach of the tunneling tip. The position of the two tips can be controlled from the millimeter scale down to 50 nm with the help of an add-on electron microscope. The instrument is capable of atomic resolution imaging with each tip.

Development of Scanning Ultrafast Electron Microscope Capability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, Kimberlee Chiyoko; Talin, Albert Alec; Chandler, David W.

Modern semiconductor devices rely on the transport of minority charge carriers. Direct examination of minority carrier lifetimes in real devices with nanometer-scale features requires a measurement method with simultaneously high spatial and temporal resolutions. Achieving nanometer spatial resolutions at sub-nanosecond temporal resolution is possible with pump-probe methods that utilize electrons as probes. Recently, a stroboscopic scanning electron microscope was developed at Caltech, and used to study carrier transport across a Si p-n junction [ 1 , 2 , 3 ] . In this report, we detail our development of a prototype scanning ultrafast electron microscope system at Sandia National Laboratoriesmore » based on the original Caltech design. This effort represents Sandia's first exploration into ultrafast electron microscopy.« less

Ultrastructure of cholinergic neurons in the laterodorsal tegmental nucleus of the rat: interaction with catecholamine fibers.

PubMed

Kubota, Y; Leung, E; Vincent, S R

1992-01-01

The ultrastructure of choline acetyltransferase (ChAT)-immunoreactive neurons in the laterodorsal tegmental nucleus (TLD) of the rat was investigated by immunohistochemical techniques. The immunoreactive neurons were medium to large in size, with a few elongated dendrites, contained well-developed cytoplasm, and a nucleus with deep infoldings. They received many nonimmunoreactive, mostly asymmetric synaptic inputs on their soma and dendrites. ChAT-immunoreactive, usually myelinated, axons were occasionally seen in TLD. Only one immunoreactive axon terminal was observed within TLD, and it made synaptic contact with a nonimmunoreactive neuronal perikaryon. The synaptic interactions between ChAT-immunoreactive neurons and tyrosine hydroxylase (TH)-immunoreactive fibers in the TLD were investigated with a double immunohistochemical staining method. ChAT-immunoreactivity detected with a beta-galactosidase method was light blue-green in the light microscope and formed dot-like electron dense particles at the electron microscopic level. TH-immunoreactivity, visualized with a nickel-enhanced immunoperoxidase method, was dark blue-black in the light microscope and diffusely opaque in the electron microscope. Therefore, the difference between these two kinds of immunoreactivity could be quite easily distinguished at both light and electron microscopic levels. In the light microscope, TH-positive fibers were often closely apposed to ChAT-immunoreactive cell bodies and dendrites in TLD. In the electron microscope, the cell soma and proximal dendrites of ChAT-immunoreactive neurons received synaptic contacts from TH-immunoreactive axon terminals. These results provide a morphological basis for catecholaminergic regulation of the cholinergic reticular system.

Role of structurally and magnetically modified nanoclusters in colossal magnetoresistance

PubMed Central

Tao, Jing; Niebieskikwiat, Dario; Jie, Qing; Schofield, Marvin A.; Wu, Lijun; Li, Qiang; Zhu, Yimei

2011-01-01

It is generally accepted that electronic and magnetic phase separation is the origin of many of exotic properties of strongly correlated electron materials, such as colossal magnetoresistance (CMR), an unusually large variation in the electrical resistivity under applied magnetic field. In the simplest picture, the two competing phases are those associated with the material state on either side of the phase transition. Those phases would be paramagnetic insulator and ferromagnetic metal for the CMR effect in doped manganites. It has been speculated that a critical component of the CMR phenomenon is nanoclusters with quite different properties than either of the terminal phases during the transition. However, the role of these nanoclusters in the CMR effect remains elusive because the physical properties of the nanoclusters are hard to measure when embedded in bulk materials. Here we show the unexpected behavior of the nanoclusters in the CMR compound La1-xCaxMnO3 (0.4 ≤ x < 0.5) by directly correlating transmission electron microscopy observations with bulk measurements. The structurally modified nanoclusters at the CMR temperature were found to be ferromagnetic and exhibit much higher electrical conductivity than previously proposed. Only at temperatures much below the CMR transition, the nanoclusters are antiferromagnetic and insulating. These findings substantially alter the current understanding of these nanoclusters on the material’s functionality and would shed light on the microscopic study on the competing spin-lattice-charge orders in strongly correlated systems. PMID:22160678

Off-axis electron holography of bacterial cells and magnetic nanoparticles in liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prozorov, Tanya; Almeida, Trevor P.; Kovacs, Andras

Here, the mapping of electrostatic potentials and magnetic fields in liquids using electron holography has been considered to be unrealistic. Here, we show that hydrated cells of Magnetospirillum magneticum strain AMB-1 and assemblies of magnetic nanoparticles can be studied using off-axis electron holography in a fluid cell specimen holder within the transmission electron microscope. Considering that the holographic object and reference wave both pass through liquid, the recorded electron holograms show sufficient interference fringe contrast to permit reconstruction of the phase shift of the electron wave and mapping of the magnetic induction from bacterial magnetite nanocrystals. We assess the challengesmore » of performing in situ magnetization reversal experiments using a fluid cell specimen holder, discuss approaches for improving spatial resolution and specimen stability, and outline future perspectives for studying scientific phenomena, ranging from interparticle interactions in liquids and electrical double layers at solid–liquid interfaces to biomineralization and the mapping of electrostatic potentials associated with protein aggregation and folding.« less

The origin of incipient ferroelectricity in lead telluride

DOE PAGES

Jiang, M. P.; Trigo, M.; Savić, I.; ...

2016-07-22

The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV–VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. The prototypical example is PbTe whose incipient ferroelectric behaviour has been recently associated with large phonon anharmonicity and thermoelectricity. Here we show that it is primarily electron-phonon coupling involving electron states near the band edges that leads to the ferroelectric instability in PbTe. Using a combination of nonequilibrium lattice dynamics measurements and first principles calculations, we find that photoexcitation reduces the Peierls-like electronic instabilitymore » and reinforces the paraelectric state. This weakens the long-range forces along the cubic direction tied to resonant bonding and low lattice thermal conductivity. Lastly, our results demonstrate how free-electron-laser-based ultrafast X-ray scattering can be utilized to shed light on the microscopic mechanisms that determine materials properties.« less

Off-axis electron holography of bacterial cells and magnetic nanoparticles in liquid

DOE PAGES

Prozorov, Tanya; Almeida, Trevor P.; Kovacs, Andras; ...

2017-10-02

Here, the mapping of electrostatic potentials and magnetic fields in liquids using electron holography has been considered to be unrealistic. Here, we show that hydrated cells of Magnetospirillum magneticum strain AMB-1 and assemblies of magnetic nanoparticles can be studied using off-axis electron holography in a fluid cell specimen holder within the transmission electron microscope. Considering that the holographic object and reference wave both pass through liquid, the recorded electron holograms show sufficient interference fringe contrast to permit reconstruction of the phase shift of the electron wave and mapping of the magnetic induction from bacterial magnetite nanocrystals. We assess the challengesmore » of performing in situ magnetization reversal experiments using a fluid cell specimen holder, discuss approaches for improving spatial resolution and specimen stability, and outline future perspectives for studying scientific phenomena, ranging from interparticle interactions in liquids and electrical double layers at solid–liquid interfaces to biomineralization and the mapping of electrostatic potentials associated with protein aggregation and folding.« less

Spatially-correlated Site Occupancy in the Nonstoichiometric Meta-stable ε -Al 60Sm 11 Phase during Devitrification of Al-10.2 at.% Sm Glasses

DOE PAGES

Yang, Lin; Zhang, Feng; Meng, Fan -Qiang; ...

2018-05-12

A metastable ε-Al 60Sm 11 phase appears during the initial devitrification of as-quenched Al-10.2 at.% Sm glasses. The ε phase is nonstoichiometric in nature since Al occupation is observed on the 16 f Sm lattice sites. Scanning transmission electron microscopic images reveal profound spatial correlation of Sm content on these sites, which cannot be explained by the “average crystal” description from Rietveld analysis of diffraction data. Thermodynamically favorable configurations, established by Monte Carlo (MC) simulations based on a cluster-expansion model, also give qualitatively different correlation functions from experimental observations. On the other hand, molecular dynamics simulations of the growth ofmore » ε-Al 60Sm 11 in undercooled liquid show that when the diffusion range of Sm is limited to ~4 Å, the correlation function of the as-grown crystal structure agrees well with that of the scanning transmission electronic microscopy (STEM) images. Furthermore, our results show that kinetic effects, especially the limited diffusivity of Sm atoms plays the fundamental role in determining the nonstoichiometric site occupancies of the ε-Al 60Sm 11 phase during the crystallization process.« less

Spatially-correlated Site Occupancy in the Nonstoichiometric Meta-stable ε -Al 60Sm 11 Phase during Devitrification of Al-10.2 at.% Sm Glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Lin; Zhang, Feng; Meng, Fan -Qiang

A metastable ε-Al 60Sm 11 phase appears during the initial devitrification of as-quenched Al-10.2 at.% Sm glasses. The ε phase is nonstoichiometric in nature since Al occupation is observed on the 16 f Sm lattice sites. Scanning transmission electron microscopic images reveal profound spatial correlation of Sm content on these sites, which cannot be explained by the “average crystal” description from Rietveld analysis of diffraction data. Thermodynamically favorable configurations, established by Monte Carlo (MC) simulations based on a cluster-expansion model, also give qualitatively different correlation functions from experimental observations. On the other hand, molecular dynamics simulations of the growth ofmore » ε-Al 60Sm 11 in undercooled liquid show that when the diffusion range of Sm is limited to ~4 Å, the correlation function of the as-grown crystal structure agrees well with that of the scanning transmission electronic microscopy (STEM) images. Furthermore, our results show that kinetic effects, especially the limited diffusivity of Sm atoms plays the fundamental role in determining the nonstoichiometric site occupancies of the ε-Al 60Sm 11 phase during the crystallization process.« less

Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro

2016-01-28

Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke’s tabulated data.

Textural Evolution During Micro Direct Metal Deposition of NiTi Alloy

NASA Astrophysics Data System (ADS)

Khademzadeh, Saeed; Bariani, Paolo F.; Bruschi, Stefania

2018-03-01

In this research, a micro direct metal deposition process, newly developed as a potential method for micro additive manufacturing was used to fabricate NiTi builds. The effect of scanning strategy on grain growth and textural evolution was investigated using scanning electron microscope equipped with electron backscattered diffraction detector. Investigations showed that, the angle between the successive single tracks has an important role in grain size distribution and textural evolution of NiTi phase. Unidirectional laser beam scanning pattern developed a fiber texture; conversely, a backward and forward scanning pattern developed a strong < {100} > ‖‖ RD texture on the surface of NiTi cubic samples produced by micro direct metal deposition.

Textural Evolution During Micro Direct Metal Deposition of NiTi Alloy

NASA Astrophysics Data System (ADS)

Khademzadeh, Saeed; Bariani, Paolo F.; Bruschi, Stefania

2018-07-01

In this research, a micro direct metal deposition process, newly developed as a potential method for micro additive manufacturing was used to fabricate NiTi builds. The effect of scanning strategy on grain growth and textural evolution was investigated using scanning electron microscope equipped with electron backscattered diffraction detector. Investigations showed that, the angle between the successive single tracks has an important role in grain size distribution and textural evolution of NiTi phase. Unidirectional laser beam scanning pattern developed a fiber texture; conversely, a backward and forward scanning pattern developed a strong < {100} > ‖‖ RD texture on the surface of NiTi cubic samples produced by micro direct metal deposition.

HA/Bioglass composite films deposited by pulsed laser with different substrate temperature

NASA Astrophysics Data System (ADS)

Wang, D. G.; Chen, C. Z.; Jin, Q. P.; Li, H. C.; Pan, Y. K.

2014-03-01

In this experiment, the HA/Bioglass composite films on Ti-6Al-4V were deposited by a pulsed laser at Ar atmosphere, and the influence of substrate temperature on the morphology, phase constitutions, bonding configurations and adhesive strength of the films was studied. The obtained films were characterized by an electron probe microanalyzer (EPMA), scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), scratch apparatus, and so on. The results show that the amount of the droplets, the crystallinity, and the critical load of the deposited films all increase with the increase of the substrate temperature; however, the substrate temperature has little influence on the functional groups of the films.

Effect of iron doping on structural and microstructural properties of nanocrystalline ZnSnO3 thin films prepared by spray pyrolysis techniques

NASA Astrophysics Data System (ADS)

Pathan, Idris G.; Suryawanshi, Dinesh N.; Bari, Anil R.; Patil, Lalchand A.

2018-05-01

This work presents the effect of iron doping having different volume ratios (1 ml, 2.5 ml and 5 ml) on the structural, microstructural and electrical properties of zinc stannate thin films, prepared by spray pyrolysis method. These properties were characterized with X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). In our study, XRD pattern indicates that ZnSnO3 has a perovskite phase with face exposed hexahedron structure. The electron diffraction fringes observed are in consistent with the peak observed in XRD patterns. Moreover the sensor reported in our study is cost-effective, user friendly and easy to fabricate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takai, Yoshizo; Kawasaki, Tadahiro; Kimura, Yoshihide

A single-atom-sized gold wire was successfully observed in real time by a newly developed defocus-image modulation processing electron microscope. Because of phase retrieval processing with spherical aberration correction, the single-atom strand wire was observed with high contrast and without contrast blurring. By carefully looking at the atomic distance, the contrast, and the dynamic behavior of the wire, we recognized that there are two stages of the wire. In the first stage the wire maintained the atomic distance in the bulk crystal, but in the second stage the wire showed the atomic distance of the nearest-neighbor atoms with weaker contrast. Themore » gold wire was rather stable for a few seconds under strong electron beam illumination.« less

High-resolution imaging of living mammalian cells bound by nanobeads-connected antibodies in a medium using scanning electron-assisted dielectric microscopy

NASA Astrophysics Data System (ADS)

Okada, Tomoko; Ogura, Toshihiko

2017-02-01

Nanometre-scale-resolution imaging technologies for liquid-phase specimens are indispensable tools in various scientific fields. In biology, observing untreated living cells in a medium is essential for analysing cellular functions. However, nanoparticles that bind living cells in a medium are hard to detect directly using traditional optical or electron microscopy. Therefore, we previously developed a novel scanning electron-assisted dielectric microscope (SE-ADM) capable of nanoscale observations. This method enables observation of intact cells in aqueous conditions. Here, we use this SE-ADM system to clearly observe antibody-binding nanobeads in liquid-phase. We also report the successful direct detection of streptavidin-conjugated nanobeads binding to untreated cells in a medium via a biotin-conjugated anti-CD44 antibody. Our system is capable of obtaining clear images of cellular organelles and beads on the cells at the same time. The direct observation of living cells with nanoparticles in a medium allowed by our system may contribute the development of carriers for drug delivery systems (DDS).

Cellular control over spicule formation in sea urchin embryos: A structural approach.

PubMed

Beniash, E; Addadi, L; Weiner, S

1999-03-01

The spicules of the sea urchin embryo form in intracellular membrane-delineated compartments. Each spicule is composed of a single crystal of calcite and amorphous calcium carbonate. The latter transforms with time into calcite by overgrowth of the preexisting crystal. Relationships between the membrane surrounding the spiculogenic compartment and the spicule mineral phase were studied in the transmission electron microscope (TEM) using freeze-fracture. In all the replicas observed the spicules were tightly surrounded by the membrane. Furthermore, a variety of structures that are related to the material exchange process across the membrane were observed. The spiculogenic cells were separated from other cell types of the embryo, frozen, and freeze-dried on the TEM grids. The contents of electron-dense granules in the spiculogenic cells were shown by electron diffraction to be composed of amorphous calcium carbonate. These observations are consistent with the notion that the amorphous calcium carbonate-containing granules contain the precursor mineral phase for spicule formation and that the membrane surrounding the forming spicule is involved both in transport of material and in controlling spicule mineralization. Copyright 1999 Academic Press.

Evolution of the properties of helium nanobubbles during in situ annealing probed by spectrum imaging in the transmission electron microscope

NASA Astrophysics Data System (ADS)

Alix, K.; David, M.-L.; Dérès, J.; Hébert, C.; Pizzagalli, L.

2018-03-01

The evolution of nanometric helium bubbles in silicon has been investigated using spatially resolved electron energy-loss spectroscopy during in situ annealing in the transmission electron microscope. This approach allows the simultaneous determination of both the morphology and the helium density in the bubbles at each step of the annealing. Structural modification and helium emission from bubbles of various diameters in the range 7.5 to 20 nm and various aspect ratios of 1.1 to 1.9 have been studied. We clearly show that helium emission takes place at temperatures where bubble migration had hardly started. At higher temperatures, the migration (and coalescence) of voids is clearly revealed. For helium density lower than 150 He nm-3 , the Cerofolini's model taking into account the thermodynamical properties of an ultradense fluid reproduces well the helium emission from the bubbles, leading to an activation energy of 1.8 eV. When bubbles exhibit a higher initial helium density, the Cerofolini's model fails to reproduce the helium emission kinetics. We ascribe this to the fact that helium may be in the solid phase and we propose a tentative model to take into account the properties of the solid.

Formation and morphology of Zn(2)Ti(3)O(8) powders using hydrothermal process without dispersant agent or mineralizer.

PubMed

Wang, Cheng-Li; Hwang, Weng-Sing; Chang, Kuo-Ming; Ko, Horng-Huey; Hsi, Chi-Shiung; Huang, Hong-Hsin; Wang, Moo-Chin

2011-01-28

Synthesis of Zn(2)Ti(3)O(8) powders for attenuating UVA using TiCl(4), Zn(NO(3))(2)·6H(2)O and NH(4)OH as precursor materials by hydrothermal process has been investigated. The X-ray diffractometry (XRD) results show the phases of ZnO, anatase TiO(2) and Zn(2)Ti(3)O(8) coexisted when the zinc titanate powders were calcined at 600 °C for 1 h. When calcined at 900 °C for 1 h, the XRD results reveal the existence of ZnO, Zn(2)TiO(4), rutile TiO(2) and ZnTiO(3). Scanning electron microscope (SEM) observations show extensive large agglomeration in the samples. Transmission electron microscope (TEM) and electron diffraction (ED) examination results indicate that ZnTiO(3) crystallites formed with a size of about 5 nm on the matrix of plate-like ZnO when calcined at 700 °C for 1 h. The calcination samples have acceptable absorbance at a wavelength of 400 nm, indicating that the zinc titanate precursor powders calcined at 700 °C for 1 h can be used as an UVA-attenuating agent.

Formation and Morphology of Zn2Ti3O8 Powders Using Hydrothermal Process without Dispersant Agent or Mineralizer

PubMed Central

Wang, Cheng-Li; Hwang, Weng-Sing; Chang, Kuo-Ming; Ko, Horng-Huey; Hsi, Chi-Shiung; Huang, Hong-Hsin; Wang, Moo-Chin

2011-01-01

Synthesis of Zn2Ti3O8 powders for attenuating UVA using TiCl4, Zn(NO3)2·6H2O and NH4OH as precursor materials by hydrothermal process has been investigated. The X-ray diffractometry (XRD) results show the phases of ZnO, anatase TiO2 and Zn2Ti3O8 coexisted when the zinc titanate powders were calcined at 600 °C for 1 h. When calcined at 900 °C for 1 h, the XRD results reveal the existence of ZnO, Zn2TiO4, rutile TiO2 and ZnTiO3. Scanning electron microscope (SEM) observations show extensive large agglomeration in the samples. Transmission electron microscope (TEM) and electron diffraction (ED) examination results indicate that ZnTiO3 crystallites formed with a size of about 5 nm on the matrix of plate-like ZnO when calcined at 700 °C for 1 h. The calcination samples have acceptable absorbance at a wavelength of 400 nm, indicating that the zinc titanate precursor powders calcined at 700 °C for 1 h can be used as an UVA-attenuating agent. PMID:21541035

Effect of substrates on microstructure and mechanical properties of nano-eutectic 1080 steel produced by aluminothermic reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

La, Peiqing, E-mail: pqla@lut.cn; Li, Zhengning; Li, Cuiling

2014-06-01

Nano-eutectic bulk 1080 carbon steel was prepared on glass and copper substrates by an aluminothermic reaction casting. The microstructure of the steel was analyzed by an optical microscope, transmission electron microscopy, an electron probe micro-analyzer, a scanning electron microscope and X-ray diffraction. Results show that the microstructure of the steel consisted of a little cementite and lamellar eutectic pearlite. Average lamellar spacing of the pearlite prepared on copper and glass substrates was about 230 nm and 219 nm, respectively. Volume fraction of the pearlite of the two steels was about 95%. Hardness of the steel was about 229 and 270more » HV. Tensile strength was about 610 and 641 MPa and tensile elongation was about 15% and 8%. Compressive strength was about 1043 and 1144 MPa. Compared with the steel prepared on copper substrate, the steel prepared on glass substrate had smaller lamellar spacing of the pearlite phase and higher strength, and low ductility due to the smaller spacing. - Highlights: • 1080-carbon steels were successfully prepared by an aluminothermic reaction casting. • Lamellar spacing of the nanoeutetic pearlite is less than 250 nm. • The compressive strength of the steel is about 1144 MPa. • The tensile ductility of the steel is about 15%.« less

Femtosecond Electron Wave Packet Propagation and Diffraction: Towards Making the ``Molecular Movie"

NASA Astrophysics Data System (ADS)

Miller, R. J. Dwayne

2003-03-01

Time-resolved electron diffraction harbors great promise for achieving atomic resolution of the fastest chemical processes. The generation of sufficiently short electron pulses to achieve this real time view of a chemical reaction has been limited by problems in maintaining short electron pulses with realistic electron densities to the sample. The propagation dynamics of femtosecond electron packets in the drift region of a photoelectron gun are investigated with an N-body numerical simulation and mean-field model. This analyis shows that the redistribution of electrons inside the packet, arising from space-charge and dispersion contributions, changes the pulse envelope and leads to the development of a spatially linear axial velocity distribution. These results have been used in the design of femtosecond photoelectron guns with higher time resolution and novel electron-optical methods of pulse characterization that are approaching 100 fs timescales. Time-resolved diffraction studies with electron pulses of approximately 500 femtoseconds have focused on solid-liquid phase transitions under far from equilibrium conditions. This work gives a microscopic description of the melting process and illustrates the promise of atomically resolving transition state processes.

77 FR 71776 - Ohio University, et al.; Notice of Consolidated Decision on Applications for Duty-Free Entry of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-04

... Consolidated Decision on Applications for Duty-Free Entry of Electron Microscope This is a decision... Stocker Center, Athens, OH 45701. Instrument: Electron Microscope. Manufacturer: JEOL Ltd., Japan... North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403-5915. Instrument: Electron...

Influence of mechanical noise inside a scanning electron microscope.

PubMed

de Faria, Marcelo Gaudenzi; Haddab, Yassine; Le Gorrec, Yann; Lutz, Philippe

2015-04-01

The scanning electron microscope is becoming a popular tool to perform tasks that require positioning, manipulation, characterization, and assembly of micro-components. However, some of these applications require a higher level of performance with respect to dynamics and precision of positioning. One limiting factor is the presence of unidentified noises and disturbances. This work aims to study the influence of mechanical disturbances generated by the environment and by the microscope, identifying how these can affect elements in the vacuum chamber. To achieve this objective, a dedicated setup, including a high-resolution vibrometer, was built inside the microscope. This work led to the identification and quantification of main disturbances and noise sources acting on a scanning electron microscope. Furthermore, the effects of external acoustic excitations were analysed. Potential applications of these results include noise compensation and real-time control for high accuracy tasks.

Phase state of a Bi-43 wt % Sn superplastic alloy and its changes under the effect of external mechanical stresses and aging

NASA Astrophysics Data System (ADS)

Korshak, V. F.; Chushkina, R. A.; Shapovalov, Yu. A.; Mateichenko, P. V.

2011-07-01

Samples of a Bi-43 wt % Sn superplastic alloy have been studied by X-ray diffraction in the ascast state, after compression of as-cast samples to ˜70% on a hydraulic press, after aging in the as-cast and preliminarily compressed state, and using samples deformed under superplastic conditions. The X-ray diffraction studies have been carried out using a DRON-2.0 diffractometer in Cu Kα radiation. The samples aged and deformed under superplasticity conditions have been studied using electron-microprobe analysis in a JSM-820 scanning electron microscope equipped with a LINK AN/85S EDX system. It has been found that the initial structural-phase state of the alloy was amorphous-crystalline. Causes that lead to a change in this state upon deformation and aging are discussed. A conclusion is made that the superplasticity effect manifests itself against the background of processes that are stipulated by the tendency of the initially metastable alloy to phase equilibrium similarly to what is observed in the Sn-38 wt % Pb eutectic alloy studied earlier.

Nanoscale structural and electronic characterization of α-RuCl3 layered compound

NASA Astrophysics Data System (ADS)

Ziatdinov, Maxim; Maksov, Artem; Banerjee, Arnab; Zhou, Wu; Berlijn, Tom; Yan, Jiaqiang; Nagler, Stephen; Mandrus, David; Baddorf, Arthur; Kalinin, Sergei

The exceptional interplay of spin-orbit effects, Coulomb interaction, and electron-lattice coupling is expected to produce an elaborate phase space of α-RuCl3 layered compound, which to date remains largely unexplored. Here we employ a combination of scanning transmission electron microscopy (STEM) and scanning tunneling microscopy (STM) for detailed evaluation of the system's microscopic structural and electronic orders with a sub-nanometer precision. The STM and STEM measurements are further supported by neutron scattering, X-Ray diffraction, density functional theory (DFT), and multivariate statistical analysis. Our results show a trigonal distortion of Cl octahedral ligand cage along the C3 symmetry axes in each RuCl3 layer. The lattice distortion is limited mainly to the Cl subsystem leaving the Ru honeycomb lattice nearly intact. The STM topographic and spectroscopic characterization reveals an intra unit cell electronic symmetry breaking in a spin-orbit coupled Mott insulating phase on the Cl-terminated surface of α-RuCl3. The associated long-range charge order (CO) pattern is linked to a surface component of Cl cage distortion. We finally discuss a fine structure of CO and its potential relation to variations of average unit cell geometries found in multivariate analysis of STEM data. The research was sponsored by the U.S. Department of Energy.

Microcircuit testing and fabrication, using scanning electron microscopes

NASA Technical Reports Server (NTRS)

Nicolas, D. P.

1975-01-01

Scanning electron microscopes are used to determine both user-induced damages and manufacturing defects subtle enough to be missed by conventional light microscopy. Method offers greater depth of field and increased working distances.

Structural phase analysis and photoluminescence properties of Mg-doped TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ali, T.; Ashraf, M. Anas; Ali, S. Asad; Ahmed, Ateeq; Tripathi, P.

2018-05-01

In this paper, we report the synthesis, characterization and photoluminescence properties of Mg-doped TiO2 nanoparticles (NPs). The samples were synthesized by sol-gel method and characterized using the standard analytical techniques such as X-ray diffraction (XRD), Transmission electron microscope (TEM), Energy dispersive X-ray spectroscopy (EDX), UV-visible and photoluminescence spectroscopy. The powder XRD spectra revealed that the synthesized samples are pure and crystalline in nature and showing tetragonal anatase phase of TiO2 NPs. UV-visible spectrum illustrates that an absorption edge shifts toward the visible region. This study may provide a new insight for making the nanomaterials which can be used in photocatalytic applications.

Transformation of multiwall carbon nanotubes to onions with layers cross-linked by sp3 bonds under high pressure and shear deformation

NASA Astrophysics Data System (ADS)

Pankov, A. M.; Bredikhina, A. S.; Kulnitskiy, B. A.; Perezhogin, I. A.; Skryleva, E. A.; Parkhomenko, Yu. N.; Popov, M. Yu.; Blank, V. D.

2017-08-01

A pressure-induced phase transition of multiwall carbon nanotubes (MWNT) to a new structure at room temperature is studied using a shear diamond anvil cell, X-ray photoelectron spectra (XPS), transmission electron microscope (TEM) and Raman procedures. We observe a cardinal pressure-induced change in the nanoparticles shape from multi-shell tubes to multi-shell spheres. MWNT transforms to onions with layers cross-linked by sp3 bonds under the 45-65 GPa compressive stress combined with shear deformation at room temperature. TEM and XPS results show that about 40% of the carbon atoms in the new phase are sp3-bounded.

UHV-TEM-REM Studies of Si(111) Surfaces

NASA Astrophysics Data System (ADS)

Yagi, K.; Yamanaka, A.; Sato, H.; Shima, M.; Ohse, H.; Ozawa, S.; Tanishiro, Y.

Recent progresses of ultra-high vacuum transmission and reflection electron microscope studies of clean Si(111) surfaces are described. Anisotropy of surface atomic steps such as step energy, bunching of steps, are studied. Out of phase boundaries are observed in transmission mode and its energy relative to the step energy is studied. The phase transition between the 1 × 1 and the 7 × 7 structures around 830°C, studied previously is re-examined under various conditions. Contraction strains of the 7 × 7 structure and adatom density on terraces play important role during the transition. Diffuse scattering observed by LEED and RHEED above the transition temperature is not observed in teh TED pattern from a thin film.

Identification of malaria infected red blood samples by digital holographic quantitative phase microscope

NASA Astrophysics Data System (ADS)

Patel, Nimit R.; Chhaniwal, Vani K.; Javidi, Bahram; Anand, Arun

2015-07-01

Development of devices for automatic identification of diseases is desired especially in developing countries. In the case of malaria, even today the gold standard is the inspection of chemically treated blood smears through a microscope. This requires a trained technician/microscopist to identify the cells in the field of view, with which the labeling chemicals gets attached. Bright field microscopes provide only low contrast 2D images of red blood cells and cell thickness distribution cannot be obtained. Quantitative phase contrast microscopes can provide both intensity and phase profiles of the cells under study. The phase information can be used to determine thickness profile of the cell. Since cell morphology is available, many parameters pertaining to the 3D shape of the cell can be computed. These parameters in turn could be used to decide about the state of health of the cell leading to disease diagnosis. Here the investigations done on digital holographic microscope, which provides quantitative phase images, for comparison of parameters obtained from the 3D shape profile of objects leading to identification of diseased samples is described.

Directed polymers on a disordered tree with a defect subtree

NASA Astrophysics Data System (ADS)

Madras, Neal; Yıldırım, Gökhan

2018-04-01

We study the question of how the competition between bulk disorder and a localized microscopic defect affects the macroscopic behavior of a system in the directed polymer context at the free energy level. We consider the directed polymer model on a disordered d-ary tree and represent the localized microscopic defect by modifying the disorder distribution at each vertex in a single path (branch), or in a subtree, of the tree. The polymer must choose between following the microscopic defect and finding the best branches through the bulk disorder. We describe three possible phases, called the fully pinned, partially pinned and depinned phases. When the microscopic defect is associated only with a single branch, we compute the free energy and the critical curve of the model, and show that the partially pinned phase does not occur. When the localized microscopic defect is associated with a non-disordered regular subtree of the disordered tree, the picture is more complicated. We prove that all three phases are non-empty below a critical temperature, and that the partially pinned phase disappears above the critical temperature.

Method of forming aperture plate for electron microscope

NASA Technical Reports Server (NTRS)

Heinemann, K. (Inventor)

1974-01-01

An electron microscope is described with an electron source a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen. It also has objective lens with an annular objective aperture, for focusing electrons passing through the specimen onto an image plane. A method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques is included.

Development of scanning electron and x-ray microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsumura, Tomokazu, E-mail: tomokzau.matsumura@etd.hpk.co.jp; Hirano, Tomohiko, E-mail: tomohiko.hirano@etd.hpk.co.jp; Suyama, Motohiro, E-mail: suyama@etd.hpk.co.jp

We have developed a new type of microscope possessing a unique feature of observing both scanning electron and X-ray images under one unit. Unlike former X-ray microscopes using SEM [1, 2], this scanning electron and X-ray (SELX) microscope has a sample in vacuum, thus it enables one to observe a surface structure of a sample by SEM mode, to search the region of interest, and to observe an X-ray image which transmits the region. For the X-ray observation, we have been focusing on the soft X-ray region from 280 eV to 3 keV to observe some bio samples and softmore » materials. The resolutions of SEM and X-ray modes are 50 nm and 100 nm, respectively, at the electron energy of 7 keV.« less

Optoacoustic Microscopy for Investigation of Material Nanostructures-Embracing the Ultrasmall, Ultrafast, and the Invisible

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurmikko, Arto; Humphrey, Maris

2014-07-10

The goal of this grant was the development of a new type of scanning acoustic microscope for nanometer resolution ultrasound imaging, based on ultrafast optoacoustics (>GHz). In the microscope, subpicosecond laser pulses was used to generate and detect very high frequency ultrasound with nanometer wavelengths. We report here on the outcome of the 3-year DOE/BES grant which involved the design, multifaceted construction, and proof-of-concept demonstration of an instrument that can be used for quantitative imaging of nanoscale material features – including features that may be buried so as to be inaccessible to conventional lightwave or electron microscopies. The research programmore » has produced a prototype scanning optoacoustic microscope which, in combination with advanced computational modeling, is a system-level new technology (two patents issues) which offer novel means for precision metrology of material nanostructures, particularly those that are of contemporary interest to the frontline micro- and optoelectronics device industry. For accomplishing the ambitious technical goals, the research roadmap was designed and implemented in two phases. In Phase I, we constructed a “non-focusing” optoacoustic microscope instrument (“POAM”), with nanometer vertical (z-) resolution, while limited to approximately 10 micrometer scale lateral recolution. The Phase I version of the instrument which was guided by extensive acoustic and optical numerical modeling of the basic underlying acoustic and optical physics, featured nanometer scale close loop positioning between the optoacoustic transducer element and a nanostructured material sample under investigation. In phase II, we implemented and demonstrated a scanning version of the instrument (“SOAM”) where incident acoustic energy is focused, and scanned on lateral (x-y) spatial scale in the 100 nm range as per the goals of the project. In so doing we developed advanced numerical simulations to provide computational models of the focusing of multi-GHz acoustic waves to the nanometer scale and innovated a series fabrication approaches for a new type of broadband high-frequency acoustic focusing microscope objective by applying methods on nanoimprinting and focused-ion beam techniques. In the following, the Phase I and Phase II instrument development is reported as Section II. The first segment of this section describes the POAM instrument and its development, while including much of the underlying ultrafast acoustic physics which is common to all of our work for this grant. Then, the science and engineering of the SOAM instrument is described, including the methods of fabricating new types of acoustic microlenses. The results section is followed by reports on publications (Section III), Participants (Section IV), and statement of full use of the allocated grant funds (Section V).« less

Examination of Surveyor 3 parts with the scanning electron microscope and electron microprobe

NASA Technical Reports Server (NTRS)

Chodos, A. A.; Devaney, J. R.; Evens, K. C.

1972-01-01

Two screws and two washers, several small chips of tubing, and a fiber removed from a third screw were examined with the scanning electron microscope and the electron microprobe. The purpose of the examination was to determine the nature of the material on the surface of these samples and to search for the presence of meteoritic material.

Structural phase transitions in niobium oxide nanocrystals

NASA Astrophysics Data System (ADS)

Yuvakkumar, R.; Hong, Sun Ig

2015-09-01

Niobium oxide nanocrystals were successfully synthesized employing the green synthesis method. Phase formation, microstructure and compositional properties of 1, 4 and 7 days incubation treated samples after calcinations at 450 °C were examined using X-ray diffraction, Raman, photoluminescence (PL), infrared, X-ray photoelectron spectra and transmission electron microscopic characterizations. It was observed that phase formation of Nb2O5 nanocrystals was dependent upon the incubation period required to form stable metal oxides. The characteristic results clearly revealed that with increasing incubation and aging, the transformation of cubic, orthorhombic and monoclinic phases were observed. The uniform heating at room temperature (32 °C) and the ligation of niobium atoms due to higher phenolic constituents of utilized rambutan during aging processing plays a vital role in structural phase transitions in niobium oxide nanocrystals. The defects over a period of incubation and the intensities of the PL spectra changing over a period of aging were related to the amount of the defects induced by the phase transition.

Effect of Aging on Precipitation Behavior and Pitting Corrosion Resistance of SAF2906 Super Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Li, Jianchun; Li, Guoping; Liang, Wei; Han, Peide; Wang, Hongxia

2017-09-01

The effect of aging temperature and holding time on the precipitation of secondary phases and pitting corrosion resistance of SAF2906 super duplex stainless steel was examined. Chromium nitride and σ phase were observed to preferentially precipitate at the ferrite/austenite interface. An amount of nitrides was also observed within the ferrite grain. The precipitation of chromium nitride occurred before the σ phase. The increase in aging temperature and holding time did not affect the concentration of the nitrides but increased the area fraction of the σ phase at a faster rate. The Cr2N precipitation in SAF2906 is more evident than that of the other duplex stainless steels. The variation tendency of the precipitation concentrations is primarily consistent with the prediction results of Thermo-Calc software. The electrochemical results showed that Cr2N and σ phase significantly reduced the pitting potential. Scanning electron microscope observations revealed that pits appear mainly in regions adjacent to sigma phase and Cr2N.

Pulsed Laser Deposited Ferromagnetic Chromium Dioxide thin Films for Applications in Spintronics

NASA Astrophysics Data System (ADS)

Dwivedi, S.; Jadhav, J.; Sharma, H.; Biswas, S.

Stable rutile type tetragonal chromium dioxide (CrO2) thin films have been deposited on lattice-matched layers of TiO2 by KrF excimer laser based pulsed laser deposition (PLD) technique using Cr2O3 target. The TiO2 seed layer was deposited on oxidized Si substrates by the same PLD process followed by annealing at 1100 °C for 4 h. The lattice-matched interfacial layer is required for the stabilization of Cr (IV) phase in CrO2, since CrO2 behaves as a metastable compound under ambient conditions and readily converts into its stable phase of Cr (III) oxide, Cr2O3. Analyses with X-ray diffraction (XRD), Glancing-angle XRD (GIXRD), Raman spectroscopy and grazing-angle Fourier transform infra-red (FTIR) spectroscopy confirm the presence of tetragonal CrO2 phase in the as-deposited films. Microstructure and surface morphology in the films were studied with field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). Electrical and magnetic characterizations of the films were performed at room temperature. Such type of stable half-metallic CrO2 thin films with low field magnetoresistive switching behaviour are in demand for applications as diverse as spin-FETs, magnetic sensors, and magneto-optical devices.

Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides

NASA Astrophysics Data System (ADS)

Yu, Rong; Si, Qimiao

2017-09-01

There is increasing recognition that the multiorbital nature of the 3 d electrons is important to the proper description of the electronic states in the normal state of the iron-based superconductors. Earlier studies of the pertinent multiorbital Hubbard models identified an orbital-selective Mott phase, which anchors the orbital-selective behavior seen in the overall phase diagram. An important characteristics of the models is that the orbitals are kinetically coupled, i.e., hybridized, to each other, which makes the orbital-selective Mott phase especially nontrivial. A U (1 ) slave-spin method was used to analyze the model with nonzero orbital-level splittings. Here we develop a Landau free-energy functional to shed further light on this issue. We put the microscopic analysis from the U (1 ) slave-spin approach in this perspective, and show that the intersite spin correlations are crucial to the renormalization of the bare hybridization amplitude towards zero and the concomitant realization of the orbital-selective Mott transition. Based on this insight, we discuss additional ways to study the orbital-selective Mott physics from a dynamical competition between the interorbital hybridization and collective spin correlations. Our results demonstrate the robustness of the orbital-selective Mott phase in the multiorbital models appropriate for the iron-based superconductors.

Kinetics of Microbial Reduction of Solid Phase U(VI)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chongxuan; Jeon, Byong Hun; Zachara, John M.

2006-10-01

Sodium boltwoodite (NaUO2SiO3OH ?1.5H2O) was used to assess the kinetics of microbial reduction of solid phase U(VI) by a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1. The bioreduction kinetics was studied with Na-boltwoodite in suspension or within alginate beads. Concentrations of U(VI)tot and cell number were varied to evaluate the coupling of U(VI) dissolution, diffusion, and microbial activity. Batch experiments were performed in a non-growth medium with lactate as electron donor at pH 6.8 buffered with PIPES. Microscopic and spectroscopic analyses with transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and laser-induced fluorescence spectroscopy (LIFS) collectively indicated that solidmore » phase U(VI) was first dissolved and diffused out of grain interiors before it was reduced on bacterial surfaces and/or within the periplasm. The kinetics of solid phase U(VI) bioreduction was well described by a coupled model of bicarbonate-promoted dissolution of Na-boltwoodite, intraparticle uranyl diffusion, and Monod type bioreduction kinetics with respect to dissolved U(VI) concentration. The results demonstrated the intimate coupling of biological, chemical, and physical processes in microbial reduction of solid phase U(VI).« less