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Sample records for ceramic channel electron

  1. Creep in electronic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Routbort, J. L.; Goretta, K. C.; Arellano-Lopez, A. R.

    2000-04-27

    High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.

  2. Surface texturing inside ceramic macro/micro channels

    NARCIS (Netherlands)

    Salamon, David; Lammertink, Rob G.H.; Wessling, Matthias

    2010-01-01

    Surface textures (roughness) inside of macro/micro channels have a number of potential uses in advanced ceramic applications, including areas such as bioceramic, cooling, microreactors or friction control. The presented microtemplating method is dealing with templating of structured fibres, which

  3. Microwave-assisted brazing of alumina ceramics for electron tube ...

    Indian Academy of Sciences (India)

    Microwave-assisted brazing of alumina ceramics for electron tube applications. MAYUR SHUKLA1,2, SUMANA GHOSH2,∗, NANDADULAL DANDAPAT2, ASHIS K MANDAL2 and VAMSI K BALLA2. 1Academy of Scientific and Innovative Research (AcSIR), CSIR—-Central Glass and Ceramic Research Institute,.

  4. Electron microscopy study of refractory ceramic fibers.

    Science.gov (United States)

    MacKinnon, P A; Lentz, T J; Rice, C H; Lockey, J E; Lemasters, G K; Gartside, P S

    2001-10-01

    In epidemiological studies designed to identify potential health risks of exposures to synthetic vitreous fibers, the characterization of airborne fiber dimensions may be essential for assessing mechanisms of fiber toxicity. Toward this end, air sampling was conducted as part of an industry-wide study of workers potentially exposed to airborne fibrous dusts during the manufacture of refractory ceramic fibers (RCF) and RCF products. Analyses of a subset of samples obtained on the sample filter as well as on the conductive sampling cowl were performed using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to characterize dimensions of airborne fibers. Comparison was made of bivariate fiber size distributions (length and diameter) from air samples analyzed by SEM and by TEM techniques. Results of the analyses indicate that RCF size distributions include fibers small enough in diameter (fibers (> 60 microm) may go undetected by TEM, as evidenced by the proportion of fibers in this category for TEM and SEM analyses (1% and 5%, respectively). Limitations of the microscopic techniques and differences in fiber-sizing rules for each method are believed to have contributed to the variation among fiber-sizing results. It was concluded from these data that further attempts to characterize RCF exposure in manufacturing and related operations should include analysis by TEM and SEM, since the smallest diameter fibers are not resolved with SEM and the fibers of longer length are not sized by TEM.

  5. Electronic Commerce and Retail Channel Substitution

    NARCIS (Netherlands)

    M.C.W. Janssen (Maarten); R. van der Noll

    2002-01-01

    textabstractWe analyze a market where firms compete in a conventional and an electronic retail channel. Consumers easily compare prices online, but some incur purchase uncertainties on the online channel. We investigate the market shares of the two retail channels and the prices that are charged. We

  6. Ceramic Translations. Volume 41. Grain Boundaries and Interfacial Phenomena in Electronic Ceramics

    Science.gov (United States)

    1994-01-01

    10. J.P. Coutures, P. Odier and C. Proust , "Barium Titanate Formation by Organic Resins Formed with Mixed Citrate", J. Mater. Sci., 27 [7] 1849-56...Technology," Chapter 8 in Electronic Ceramics. Editor L M. Levinson, Marcel Dekker, New York, 1988. Hodgkins, C. E., "Delaminations in Multilayer Ceramic...Processing and Applications) 2nd Edition, Editor: R. C. Buchanan, Marcel and Dekker, New York, 1990. Table 1. PSID of the buoifrn nowders tsed In make the

  7. Metal particles in a ceramic matrix--scanning electron microscopy and transmission electron microscopy characterization.

    Science.gov (United States)

    Konopka, K

    2006-09-01

    This paper is concerned with ceramic matrix (Al(2)O(3)) composites with introduced metal particles (Ni, Fe). The composites were obtained via sintering of powders under very high pressure (2.5 GPa). Scanning electron microscopy and transmission electron microscopy were chosen as the tools for the identification and description of the shape, size and distribution of the metal particles. The Al(2)O(3)-Ni composite contained agglomerates of the Ni particles surrounded by ceramic grains and nanometre-size Ni particles located inside the ceramic grains and at the ceramic grain boundaries. In the Al(2)O(3)-Fe composite, the Fe particles were mostly surrounded by ceramic grains. Moreover, holes left by the Fe particles were found. The high pressure used in the fabrication of the composites changed the shape of the metal and ceramic powder grains via plastic deformation.

  8. Electron momentum distribution and electronic response of ceramic borides

    Energy Technology Data Exchange (ETDEWEB)

    Heda, N.L. [Department of Pure and Applied Physics, University of Kota, Kota 324005 (India); Meena, B.S.; Mund, H.S. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India); Sahariya, Jagrati [Department of Physics, Manipal University, Jaipur 303007 (India); Kumar, Kishor [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India)

    2017-03-15

    Isotropic Compton profiles of transition metal based ceramics TaB and VB have been measured using {sup 137}Cs (661.65 keV) γ-ray Compton spectrometer. The experimental momentum densities are compared with those deduced using linear combination of atomic orbitals (LCAO) with Hartree-Fock (HF), density functional theory (DFT) with Wu-Cohen generalized gradient approximation (WCGGA) and also the hybridization of HF and DFT (namely B3PW and PBE0) schemes. It is found that LCAO-DFT-WCGGA scheme based profiles give an overall better agreement with the experimental data, for both the borides. In addition, we have computed the Mulliken's population (MP) charge transfer data, energy bands, density of states and Fermi surface topology of both the borides using full potential-linearized augmented plane wave (FP-LAPW) and LCAO methods with DFT-WCGGA scheme. Cross-overs of Fermi level by the energy bands corresponding to B-2p and valence d-states of transition metals lead to metallic character in both the compounds. Equal-valence-electron-density profiles and MP analysis suggest more ionic character of VB than that of TaB.

  9. Electronic Conductivity of Vanadium-Tellurite Glass-Ceramics

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Yue, Yuanzheng; Bragatto, Caio B.

    2013-01-01

    In this paper, we investigate the electronic conductivity of 2TeO2-V2O5 glass-ceramics with crystallinity ranging from 0 to 100 wt.%, i.e., from entirely amorphous to completely crystalline. The glass is prepared by the melt quenching technique, and the crystal is prepared by subsequent heat...... treatment thereof. Glass-ceramics are prepared by mixing glass and crystal powder, followed by a sintering procedure. Activation energies for electronic conduction in the glass and in the crystal are determined by fitting the Mott-Austin equation to the electronic conductivity data obtained by impedance...... spectroscopy. We find similar activation energies for both glass and crystal, implying that they have similar conduction mechanisms, i.e., thermally activated hopping. The electronic conductivity of 2TeO2-V2O5 glass is about one order of magnitude higher than that of the corresponding crystal...

  10. Emission of an intense electron beam from a ceramic honeycomb

    Science.gov (United States)

    Friedman, M.; Myers, M.; Hegeler, F.; Swanekamp, S. B.; Sethian, J. D.; Ludeking, L.

    2003-01-01

    Inserting a slab of honeycomb ceramic in front of the emitting surface of a large-area cathode improves the electron beam emission uniformity, decreases the beam current rise and fall times, and maintains a more constant diode impedance. Moreover, changing the cathode material from velvet to carbon fiber achieved a more robust cathode that starts to emit at a higher electric field without a degradation in beam uniformity. In addition, an 80% reduction in the postshot diode pressure was also observed when gamma alumina was deposited on the ceramic. A possible explanation is that reabsorption and recycling of adsorbed gases takes place.

  11. Mixed oxygen ion/electron-conducting ceramics for oxygen separation

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, J.W.; Armstrong, T.R.; Armstrong, B.L. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-08-01

    Mixed oxygen ion and electron-conducting ceramics are unique materials that can passively separate high purity oxygen from air. Oxygen ions move through a fully dense ceramic in response to an oxygen concentration gradient, charge-compensated by an electron flux in the opposite direction. Compositions in the system La{sub 1{minus}x}M{sub x}Co{sub 1{minus}y{minus}z}Fe{sub y}N{sub z}O{sub 3{minus}{delta}}, perovskites where M=Sr, Ca, and Ba, and N=Mn, Ni, Cu, Ti, and Al, have been prepared and their electrical, oxygen permeation, oxygen vacancy equilibria, and catalytic properties evaluated. Tubular forms, disks, and asymmetric membrane structures, a thin dense layer on a porous support of the same composition, have been fabricated for testing purposes. In an oxygen partial gradient, the passive oxygen flux through fully dense structures was highly dependent on composition. An increase in oxygen permeation with increased temperature is attributed to both enhanced oxygen vacancy mobility and higher vacancy populations. Highly acceptor-doped compositions resulted in oxygen ion mobilities more than an order of magnitude higher than yttria-stabilized zirconia. The mixed conducting ceramics have been utilized in a membrane reactor configuration to upgrade methane to ethane and ethylene. Conditions were established to balance selectivity and throughput in a catalytic membrane reactor constructed from mixed conducting ceramics.

  12. Simplifying Electron Beam Channeling in Scanning Transmission Electron Microscopy (STEM).

    Science.gov (United States)

    Wu, Ryan J; Mittal, Anudha; Odlyzko, Michael L; Mkhoyan, K Andre

    2017-08-01

    Sub-angstrom scanning transmission electron microscopy (STEM) allows quantitative column-by-column analysis of crystalline specimens via annular dark-field images. The intensity of electrons scattered from a particular location in an atomic column depends on the intensity of the electron probe at that location. Electron beam channeling causes oscillations in the STEM probe intensity during specimen propagation, which leads to differences in the beam intensity incident at different depths. Understanding the parameters that control this complex behavior is critical for interpreting experimental STEM results. In this work, theoretical analysis of the STEM probe intensity reveals that intensity oscillations during specimen propagation are regulated by changes in the beam's angular distribution. Three distinct regimes of channeling behavior are observed: the high-atomic-number (Z) regime, in which atomic scattering leads to significant angular redistribution of the beam; the low-Z regime, in which the probe's initial angular distribution controls intensity oscillations; and the intermediate-Z regime, in which the behavior is mixed. These contrasting regimes are shown to exist for a wide range of probe parameters. These results provide a new understanding of the occurrence and consequences of channeling phenomena and conditions under which their influence is strengthened or weakened by characteristics of the electron probe and sample.

  13. Use of high-thermal conductive aluminum nitride based ceramics in vacuum UHF electronic devices

    Directory of Open Access Journals (Sweden)

    Chasnyk V. I.

    2013-06-01

    Full Text Available Analysis of properties and characteristics of the alumina, beryllium oxide and aluminum nitride based ceramic materials used in UHF electronic devices has been made. It was shown that the complex of parameters including structural and functional characteristics of the high-thermal conductive aluminum nitride ceramics prevail over all types of alumina ceramics and is not lower than the same characteristics of the beryllium oxide ceramics especially at the temperatures higher than 450 °C. The examples of the prevailing use of the aluminum nitride ceramics inside vacuum UHF-region devices: TWT’s and klystrons.

  14. Optimisation of the cooling channel design of carbon-ceramic brakes

    Energy Technology Data Exchange (ETDEWEB)

    Guether, H.M.; Wuellner, A. [SGL Brakes GmbH, Meitingen (Germany)

    2005-07-01

    Carbon-Ceramic Brake Discs are more and more applied in upper class limousines or high performance vehicles. Normally, a larger brake disc diameter is necessary because of a lower specific heat of carbon ceramic materials as far as the mass is concerned, compared to the specific heat of grey cast iron. A thermal and for production suitable design may represent a remedy for this extension of the brake disc. A suitable optimisation of the cooling channel design represents the most efficient possibility of thermal optimisation. Therefore an improvement of the convective heat transfer in the cooling channels by the help of optimised geometry is realised. Within the scope of a development project at SGL Brakes, several calculation and simulation models have been developed, which make the construction of optimised, highly complex cooling channel geometry possible. The model calculations were checked at the dynamometer by the help of prototype parts. The result is an optimised cooling channel design, which can be realised by the help of the 'lost cores' technology. The validation of the results for optimising the cooling channel design took part within the Bugatti Veyron project. (orig.)

  15. Dictionary Indexing of Electron Channeling Patterns.

    Science.gov (United States)

    Singh, Saransh; De Graef, Marc

    2017-02-01

    The dictionary-based approach to the indexing of diffraction patterns is applied to electron channeling patterns (ECPs). The main ingredients of the dictionary method are introduced, including the generalized forward projector (GFP), the relevant detector model, and a scheme to uniformly sample orientation space using the "cubochoric" representation. The GFP is used to compute an ECP "master" pattern. Derivative free optimization algorithms, including the Nelder-Mead simplex and the bound optimization by quadratic approximation are used to determine the correct detector parameters and to refine the orientation obtained from the dictionary approach. The indexing method is applied to poly-silicon and shows excellent agreement with the calibrated values. Finally, it is shown that the method results in a mean disorientation error of 1.0° with 0.5° SD for a range of detector parameters.

  16. Raman scattering of photons by the channeling electrons

    Science.gov (United States)

    Badreeva, D. R.; Kalashnikov, N. P.

    2017-07-01

    The motion of channeling particles in the accompanying coordinate system can be considered as a two-dimensional atom in the case of axial channeling. The transversal motion of the channeling particles is characterized by discrete spectrum. The occupation probability of the transversal motion levels depends on the entrance angle of the charged particles relative to the crystallographic axis. In the scattering of a photon by the ;quasi-bound; electron moving in the axial channeling regime would appear the frequencies ω which are a combination of the incident photon frequency ω0 and the frequency ωNM (ωNM is the transition frequency in transverse quantized motion of the channeling electron: ω =ω0 ±ωMN , where ℏωMN = 2γ2 ΔE⊥NM for the relativistic electron, γ2 = E / (mc2) is the Lorentz factor of the channeling electron). In the article are discussed the criteria for choosing an adequate continuous potential of the crystallographic axis and the quantum characteristics of a transversal motion of the channeling electron. The peculiarities of the Raman scattering spectrum of photons by electrons in the axial channeling regime are analyzed and the differential cross section of this process is found.

  17. Electron-beam guiding by a reduced-density channel

    Science.gov (United States)

    Welch, D. R.; Bieniosek, F. M.; Godfrey, B. B.

    1990-12-01

    A new regime of density-channel guiding of a relativistic electron beam in air has been found using a three-dimensional charged-particle simulation code, and confirmed in a double-pulse electron-beam experiment. The guiding results from the temperature dependence of the electron-neutral momentum-transfer frequency nu(m). The mechanism does not require a deep channel to obtain a significant guiding force. For the 13-kA MEDEA II (and beams of similar parameters), guiding persists 10 nsec into the beam pulse, with the force per channel displacement as high as 4 G/cm.

  18. Electronic government: Rethinking channel management strategies

    NARCIS (Netherlands)

    Ebbers, Wolfgang E.; Pieterson, Willem Jan; Noordman, H.N.

    2008-01-01

    This article explores how an alternative multichannel management strategy can improve the way governments and citizens interact. Improvement is necessary because, based on empirical data from various sources, the conclusion can be drawn that there is a gap between the communication channels

  19. POES MEPED differential flux retrievals and electron channel contamination correction

    Science.gov (United States)

    Peck, E. D.; Randall, C. E.; Green, J. C.; Rodriguez, J. V.; Rodger, C. J.

    2015-06-01

    A correction method to remove proton contamination from the electron channels of the Polar-orbiting Operational Environmental Satellites Medium Energy Proton/Electron Detector (MEPED) is described. Proton contamination estimates are based on measurements in five of the MEPED proton spectral channels. A constrained inversion of the MEPED proton channel response function matrix is used to calculate proton differential flux spectra. In this inversion, the proton energy distribution is described by a weighted combination of exponential, power law, and Maxwellian distributions. Proton contamination in the MEPED electron spectral channels is derived by applying the electron channel proton sensitivities to the proton fluxes from the best fit proton spectra. Once the electron channel measurements are corrected for proton contamination, an inversion of the electron channel response function matrix is used to calculate electron differential flux spectra. A side benefit of the method is that it yields an estimate for the integrated electron flux in the energy range from 300 keV to 2.5 MeV with a center energy at ~800 keV. The final product is a differential spectrum of electron flux covering the energy range from about 10 keV to 2.5 MeV that is devoid of proton contamination except during large solar proton events. Comparisons of corrected MEPED differential fluxes to the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions Instrument for Detecting Particles show that MEPED fluxes are greater than what is expected from altitude-induced particle population changes; this is attributed at least partially to measurement differences in pitch angle range.

  20. Effect of ceramic membrane channel diameter on limiting retentate protein concentration during skim milk microfiltration.

    Science.gov (United States)

    Adams, Michael C; Barbano, David M

    2016-01-01

    Our objective was to determine the effect of retentate flow channel diameter (4 or 6mm) of nongraded permeability 100-nm pore size ceramic membranes operated in nonuniform transmembrane pressure mode on the limiting retentate protein concentration (LRPC) while microfiltering (MF) skim milk at a temperature of 50°C, a flux of 55 kg · m(-2) · h(-1), and an average cross-flow velocity of 7 m · s(-1). At the above conditions, the retentate true protein concentration was incrementally increased from 7 to 11.5%. When temperature, flux, and average cross-flow velocity were controlled, ceramic membrane retentate flow channel diameter did not affect the LRPC. This indicates that LRPC is not a function of the Reynolds number. Computational fluid dynamics data, which indicated that both membranes had similar radial velocity profiles within their retentate flow channels, supported this finding. Membranes with 6-mm flow channels can be operated at a lower pressure decrease from membrane inlet to membrane outlet (ΔP) or at a higher cross-flow velocity, depending on which is controlled, than membranes with 4-mm flow channels. This implies that 6-mm membranes could achieve a higher LRPC than 4-mm membranes at the same ΔP due to an increase in cross-flow velocity. In theory, the higher LRPC of the 6-mm membranes could facilitate 95% serum protein removal in 2 MF stages with diafiltration between stages if no serum protein were rejected by the membrane. At the same flux, retentate protein concentration, and average cross-flow velocity, 4-mm membranes require 21% more energy to remove a given amount of permeate than 6-mm membranes, despite the lower surface area of the 6-mm membranes. Equations to predict skim milk MF retentate viscosity as a function of protein concentration and temperature are provided. Retentate viscosity, retentate recirculation pump frequency required to maintain a given cross-flow velocity at a given retentate viscosity, and retentate protein

  1. On the electron density localization in elemental cubic ceramic and FCC transition metals by means of a localized electrons detector.

    Science.gov (United States)

    Aray, Yosslen; Paredes, Ricardo; Álvarez, Luis Javier; Martiz, Alejandro

    2017-06-14

    The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges. On the contrary, for the transition metals, there are low-valued localized electrons detector isocontours defining a zone of highly delocalized electrons that extends throughout the material. We have found that the best conductors are those in which the electron density at this low-value zone is the lowest.

  2. Induced resonance evolution of the channeling electron beam

    Science.gov (United States)

    Ambartsumov, Vazgen V.; Kalashnikov, Nikolay P.

    2017-07-01

    The motion of channeling particles in the accompanying coordinate system can be considered as one-dimensional oscillator (in the case of planar channeling) or as a two-dimensional atom (in the case of axial channeling) (Lindhard, 1965; Baryshevskii, 1982; Vorobiev, 1984; Kalashnikov, 1988; Ryabov, 1994). The transversal motion of the channeling particles is characterized by discrete spectrum. The occupation probability of the transversal motion levels depends on the entrance angle of charged particle relative to the crystallographic axis. Passing through the single crystal the charged channeling particle undergoes periodic impact of the lattice atoms (Kalashnikov, 1988; Foot, 2005; Ter-Mikaelyan, 1972; Okorokov et al., 1973) with the main frequency ω = 2 πv/d γ , where d is the lattice constant, v and γ = E/mc2 are the speed and the Lorentz-factor of the channeling particles (Kalashnikov, 1988). If an external periodic action frequency coincides with the transition frequency of the channeling particles from one quantized state of transversal motion in another, then the resonant excitation of channeling particles is possible. This effect is analogous with the excitation of the atomic electrons by the periodic field of monochromatic electromagnetic waves (Ter-Mikaelyan, 1972; Okorokov et al., 1973; Ohtsuki, 1983). The resonance conditions are discussed and the dependence of the occupation probability of the transversal motion levels of the channeling particles (electrons) upon the single crystal thickness is analyzed.

  3. Cherenkov wakefield excitation by relativistic electron beams in plasma channels

    Science.gov (United States)

    Wang, Tianhong; Khudik, Vladimir; Shvets, Gennday

    2017-10-01

    We report on our theoretical investigations of Cherenkov radiation excited by relativistic electron bunches propagating in plasma channels and in polaritonic channels. Two surface plasmons (SPs) modes of the radiation are analyzed: the longitudinal (accelerating) and the transverse (deflecting) ones. Both form Cherenkov cones that are different in the magnitude of the cone angle and the central frequency. We show that the Cherenkov field profile change dramatically depending on the driver velocity and the channel size, and the longitudinal mode forms a reversed Cherenkov radiation cone due to the negative group velocity for sufficiently small air gaps. In addition, we find that when the channel surface is corrugated, a strong deflecting wake is excited by a relativistic electron bunch. A trailing electron bunch experiencing this wake is forced to undergo betatron oscillations and thus to emit radiation. Numerical simulation showed that intense x-ray radiation can be generated.

  4. Bent crystal channeling of 255 MeV electrons

    Science.gov (United States)

    Takabayashi, Y.; Pivovarov, Yu. L.; Tukhfatullin, T. A.

    2018-01-01

    Charged particles channeled in a bent crystal plane are known to be deflected along the bent plane. Such studies have mainly been performed for high-energy positively-charged particles such as protons, and recently for electrons with energies from 855 MeV to 20.35 GeV. In this work, we present experimental results on the bent crystal channeling of electrons for a lower energy region (255 MeV), where the multiple scattering effect in a crystal is expected to be more dominant. Angular distributions of electrons transmitted through a bent Si crystal have been measured, which are in good agreement with the simulation results.

  5. Process development for electron beam joining of ceramic and glass components

    Energy Technology Data Exchange (ETDEWEB)

    Turman, B.N.; Glass, S.J.; Yang, P.; Gerstle, F.P.; Halbleib, J.A.; Voth, T.E.; McKenzie, B. [Sandia National Labs., Albuquerque, NM (United States); Clifford, J.R.; Habiger, K. [Titan Advanced Technologies Group, Albuquerque, NM (United States)

    1997-11-01

    The purpose of this project is to develop and extend the electron beam joining process to applications related to Mo/Al{sub 2}O{sub 3} cermets for neutron tube fabrication, glass seals for flat panel displays, and ceramics for structural applications. The key issue is the identification of the allowable operating ranges that produce thermal conditions favorable to robust joining and sealing. High strength, hermetic braze joints between ceramic components have been produced using high energy electron beams. With a penetration depth into a typical ceramic of {approximately} 1 cm for a 10 MeV electron beam, this method provides the capability for rapid, transient brazing operations where temperature control of heat sensitive components is essential. The method deposits energy directly into a buried joint, allowing otherwise inaccessible interfaces to be brazed. The combination of transient heating, with higher thermal conductivity, lower heat capacity, and lower melting temperature of braze metals relative to the ceramic materials, enables a pulsed high power beam to melt a braze metal without producing excessive ceramic temperatures. The authors have demonstrated the feasibility of this process related to ceramic coupons a well as ceramic and glass tubes and cylindrical shapes. The transient thermal response was predicted, using as input the energy absorption predicted from the coupled electron-photon and thermal transport analysis. The joining experiments were conducted with an RF linear accelerator at 10--13 MV. Joining experiments have provided high strength joints between alumina and alumina and between alumina and cermet joints in cylindrical geometry. These joints provided good hermetic seals.

  6. Electron cryo-microscopy structure of the mechanotransduction channel NOMPC.

    Science.gov (United States)

    Jin, Peng; Bulkley, David; Guo, Yanmeng; Zhang, Wei; Guo, Zhenhao; Huynh, Walter; Wu, Shenping; Meltzer, Shan; Cheng, Tong; Jan, Lily Yeh; Jan, Yuh-Nung; Cheng, Yifan

    2017-07-06

    Mechanosensory transduction for senses such as proprioception, touch, balance, acceleration, hearing and pain relies on mechanotransduction channels, which convert mechanical stimuli into electrical signals in specialized sensory cells. How force gates mechanotransduction channels is a central question in the field, for which there are two major models. One is the membrane-tension model: force applied to the membrane generates a change in membrane tension that is sufficient to gate the channel, as in the bacterial MscL channel and certain eukaryotic potassium channels. The other is the tether model: force is transmitted via a tether to gate the channel. The transient receptor potential (TRP) channel NOMPC is important for mechanosensation-related behaviours such as locomotion, touch and sound sensation across different species including Caenorhabditis elegans, Drosophila and zebrafish. NOMPC is the founding member of the TRPN subfamily, and is thought to be gated by tethering of its ankyrin repeat domain to microtubules of the cytoskeleton. Thus, a goal of studying NOMPC is to reveal the underlying mechanism of force-induced gating, which could serve as a paradigm of the tether model. NOMPC fulfils all the criteria that apply to mechanotransduction channels and has 29 ankyrin repeats, the largest number among TRP channels. A key question is how the long ankyrin repeat domain is organized as a tether that can trigger channel gating. Here we present a de novo atomic structure of Drosophila NOMPC determined by single-particle electron cryo-microscopy. Structural analysis suggests that the ankyrin repeat domain of NOMPC resembles a helical spring, suggesting its role of linking mechanical displacement of the cytoskeleton to the opening of the channel. The NOMPC architecture underscores the basis of translating mechanical force into an electrical signal within a cell.

  7. Laser electron collider within a micro-channel

    Science.gov (United States)

    Ji, Liangliang

    2017-10-01

    We propose a laser-electron collider based on a laser-driven micro-channel-plate target. In this unique geometry, electrons accelerated within the channel can collide head-on with the laser reflected from a foil attached onto the rear target surface. The simple scheme allows for efficient generation of gamma-photons and most importantly, the observing of radiation-reaction effect for the first time. It resolves the aligning and time synchronization challenges for laser-electron colliding scenarios involving two light/electron beams. We predict that a single 5PW laser is sufficient to make radiation-reaction effect measurable. A principle-of-proof experiment was conducted at a currently available 200TW laser system. The superior acceleration of electrons with the novel micro-channel structure was confirmed, showing enhanced electron cut-off energies and slope temperatures compared to ordinary flat interfaces. The results set forth the basis for radiation-reaction measurement from laser-electron colliding in upcoming multi-petawatt laser systems.

  8. Electronic ceramic structure within the Voronoi cells model and microstructure fractals contacts surfaces new frontier applications

    Directory of Open Access Journals (Sweden)

    Mitić V.V.

    2013-01-01

    Full Text Available In this study, in order to establish grain shapes of sintered ceramics, new approach on correlation between microstructure and doped BaTiO3 -ceramics properties based, on Voronoi model and mathematical statistics calculations on fractal geometry, has been developed. BaTiO3-ceramics doped with Yb2O3 (from 0.1 to 1.0wt% of Yb were prepared by using conventional solid state procedure and were sintered from 1320°C to 1380°C for four hours. The microstructure of sintered specimens was investigated by Scanning electron microscope JEOL-SEM-5300. For better and deeper characterization and understanding of the ceramics material microstructure, the methods which include the fractal nature structure, and also Voronoi model and mathematical statistics calculations, are applied. In our research the Voronoi is one specific interface between fractal structure nature and different stochastically contact surfaces, defined by statistical mathematical methods. Also, the Voronoi model practically provided possibility to control the ceramics microstructure fractal nature. Mathematical statistic methods enabled establishing the real model for the prognosis based on correlation: synthesis-structures-properties. [Projekat Ministarstva nauke Republike Srbije, br. 172057 i br. III44006

  9. ELECTRON BEAM SENSITIVITY AND STRUCTURE OF THE GLASSY PHASE OF CERAMICS

    Energy Technology Data Exchange (ETDEWEB)

    Laval, J.Y.; Westmacott, K.H.

    1980-01-01

    The electron beam sensitivity of glassy ceramics was reviewed. It was shown that the glassy phase resulting from the segregation of additives such as CaO or MgO at the grain boundaries was highly sensitive to the electron beam. We have reported elsewhere that the electron damage kinetics corresponds to an ionization process (Laval, Westmacott, 1979). This ionization process was discussed in terms of chemical bondings and ionic states, and by referring to the soda-glass structure. From these considerations new insights into the structure of the glassy phase were obtained. From the nature of the ionization effects it is possible to postulate which ion will lead to the damage and therefore to know the structure and the composition of the glassy phase on a nanometric scale. Thus the electron beam sensitivity of glassy ceramic enables a very thin intergranular glassy phase to be characterized and is of great value in determining the structure of the grain boundaries and of metal-oxide or glass-ceramic interfaces.

  10. Characterization of encapsulated quantum dots via electron channeling contrast imaging

    Science.gov (United States)

    Deitz, Julia I.; Carnevale, Santino D.; De Graef, Marc; McComb, David W.; Grassman, Tyler J.

    2016-08-01

    A method for characterization of encapsulated epitaxial quantum dots (QD) in plan-view geometry using electron channeling contrast imaging (ECCI) is presented. The efficacy of the method, which requires minimal sample preparation, is demonstrated with proof-of-concept data from encapsulated (sub-surface) epitaxial InAs QDs within a GaAs matrix. Imaging of the QDs under multiple diffraction conditions is presented, establishing that ECCI can provide effectively identical visualization capabilities as conventional two-beam transmission electron microscopy. This method facilitates rapid, non-destructive characterization of sub-surface QDs giving immediate access to valuable nanostructural information.

  11. Characterization of encapsulated quantum dots via electron channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Deitz, Julia I.; McComb, David W. [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Carnevale, Santino D. [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Grassman, Tyler J., E-mail: grassman.5@osu.edu [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2016-08-08

    A method for characterization of encapsulated epitaxial quantum dots (QD) in plan-view geometry using electron channeling contrast imaging (ECCI) is presented. The efficacy of the method, which requires minimal sample preparation, is demonstrated with proof-of-concept data from encapsulated (sub-surface) epitaxial InAs QDs within a GaAs matrix. Imaging of the QDs under multiple diffraction conditions is presented, establishing that ECCI can provide effectively identical visualization capabilities as conventional two-beam transmission electron microscopy. This method facilitates rapid, non-destructive characterization of sub-surface QDs giving immediate access to valuable nanostructural information.

  12. Microwave-assisted brazing of alumina ceramics for electron tube ...

    Indian Academy of Sciences (India)

    The brazed joints were characterizedby X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Vickers microhardness evaluation, brazing strength measurement and helium leak test. X-ray diffraction analysis confirmed the formationof Ti-based compounds at the substrate-filler alloy interfaces of ...

  13. Thermally-induced electronic relaxation in structurally-modified Cu{sub 0.1}Ni{sub 0.8}Co{sub 0.2}Mn{sub 1.9}O{sub 4} spinel ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O., E-mail: shpotyuk@novas.lviv.ua [Institute of Materials, Scientific Research Company “Carat”, 202, Stryjska Street, Lviv 79031 (Ukraine); Institute of Physics, Jan Dlugosz University, 13/15, al. Armii Krajowej, Czestochowa 42200 Poland (Poland); Balitska, V. [Institute of Materials, Scientific Research Company “Carat”, 202, Stryjska Street, Lviv 79031 (Ukraine); Lviv State University of Vital Activity Safety, 35, Kleparivska Street, Lviv 79007 (Ukraine); Brunner, M. [Fachhochschule Köln/University of Applied Sciences, 2, Betzdorfer Strasse, Köln 50679 (Germany); Hadzaman, I. [Institute of Materials, Scientific Research Company “Carat”, 202, Stryjska Street, Lviv 79031 (Ukraine); Drohobych Ivan Franko State Pedagogical University, 24, I. Franko Street, Drohobych 82100 (Ukraine); Klym, H. [Institute of Materials, Scientific Research Company “Carat”, 202, Stryjska Street, Lviv 79031 (Ukraine); Lviv Polytechnic National University, 12, Bandera Street, Lviv 79013 (Ukraine)

    2015-02-15

    Thermally-induced electronic relaxation in structurally-modified Cu{sub 0.1}Ni{sub 0.8}Co{sub 0.2}Mn{sub 1.9}O{sub 4} spinel ceramics is shown to be adequately described by stretched exponential function on time. This kinetics is defined by microsctructure perfectness of the relaxing media, showing obvious onset to stretched exponential behaviour with non-exponentionality index attaining close to 0.43 values for high-monolith ceramics and smaller ones in fine-grained ceramics. Percolation threshold in relaxation-degradation kinetics is detected for ceramics with 10% of NiO extractions, showing the smallest but most prolonged single-path degradation effect. This finding is treated in terms of Phillips’ axiomatic diffusion-to-trap model, where only one of two relaxation channels (caused by operative short-range forces) occurs to be effective, while additional non-operative channels contribute to electronic relaxation in fine-grained ceramics.

  14. Structure of TRPV1 channel revealed by electron cryomicroscopy.

    Science.gov (United States)

    Moiseenkova-Bell, Vera Y; Stanciu, Lia A; Serysheva, Irina I; Tobe, Ben J; Wensel, Theodore G

    2008-05-27

    The transient receptor potential (TRP) family of ion channels participate in many signaling pathways. TRPV1 functions as a molecular integrator of noxious stimuli, including heat, low pH, and chemical ligands. Here, we report the 3D structure of full-length rat TRPV1 channel expressed in the yeast Saccharomyces cerevisiae and purified by immunoaffinity chromatography. We demonstrate that the recombinant purified TRPV1 channel retains its structural and functional integrity and is suitable for structural analysis. The 19-A structure of TRPV1 determined by using single-particle electron cryomicroscopy exhibits fourfold symmetry and comprises two distinct regions: a large open basket-like domain, likely corresponding to the cytoplasmic N- and C-terminal portions, and a more compact domain, corresponding to the transmembrane portion. The assignment of transmembrane and cytoplasmic regions was supported by fitting crystal structures of the structurally homologous Kv1.2 channel and isolated TRPV1 ankyrin repeats into the TRPV1 structure.

  15. Laser-electron Compton interaction in plasma channels

    Energy Technology Data Exchange (ETDEWEB)

    Pogorelsky, I.V.; Ben-Zvi, I. [Brookhaven National Lab., Upton, NY (United States); Hirose, T. [Tokyo Metropolitan Univ. (Japan). Physics Dept.

    1998-10-01

    A concept of high intensity femtosecond laser synchrotron source (LSS) is based on Compton backscattering of focused electron and laser beams. The short Rayleigh length of the focused laser beam limits the length of interaction to a few picoseconds. However, the technology of the high repetition rate high-average power picosecond lasers required for high put through LSS applications is not developed yet. Another problem associated with the picosecond laser pulses is undesirable nonlinear effects occurring when the laser photons are concentrated in a short time interval. To avoid the nonlinear Compton scattering, the laser beam has to be split, and the required hard radiation flux is accumulated over a number of consecutive interactions that complicates the LSS design. In order to relieve the technological constraints and achieve a practically feasible high-power laser synchrotron source, the authors propose to confine the laser-electron interaction region in the extended plasma channel. This approach permits to use nanosecond laser pulses instead of the picosecond pulses. That helps to avoid the nonlinear Compton scattering regime and allows to utilize already existing technology of the high-repetition rate TEA CO{sub 2} lasers operating at the atmospheric pressure. They demonstrate the advantages of the channeled LSS approach by the example of the prospective polarized positron source for Japan Linear Collider.

  16. High resolution electron microscopy investigations of interface and other structure defects in some ceramics.

    Science.gov (United States)

    Wen, S; Liu, Q

    1998-02-01

    Interface, grain boundary, and other structure defects are the most important structural factors to affect the properties of ceramics materials. The present paper shows the relationship between the properties and those structure features such as grain boundaries, phase boundaries, interfaces, twins, intergrowths, dislocations, point defect aggregates, order-disorder, and other structure defects in different kinds of ceramics materials. At present this research covers: C60, sialon-based ceramics (alpha-sialon/SiC(w) composite, Y-alpha-sialon/beta-sialon composite), high Tc superconductors (YBa2Cu3O7, YBa2Cu4O8, Bi2Sr2CaCu2O8, Bi2Sr2Ca2Cu3O10), and bioceramics (hydroxyapatite, chlorapatite) and so on. The structure features mentioned above were characterized by high-resolution electron microscopy; so the structure details are at an atomic level and the related physical, chemical, engineering, even biological phenomena can be understood at an atomic and molecular level.

  17. Transmission Electron Microscopy Specimen Preparation Method for Multiphase Porous Functional Ceramics

    DEFF Research Database (Denmark)

    Zhang, Wei; Kuhn, Luise Theil; Jørgensen, Peter Stanley

    2013-01-01

    by successful preparation of TEM specimens that maintain the structural integrity of the entire lamella. Feasibility of the TEM alignment procedure is demonstrated, and ideal TEM analyses are illustrated on solid oxide fuel cell and solid oxide electrolysis cell materials. Some potential drawbacks of the TEM......An optimum method is proposed to prepare thin foil transmission electron microscopy (TEM) lamellae of multiphase porous functional ceramics: prefilling the pore space of these materials with an epoxy resin prior to focused ion beam milling. Several advantages of epoxy impregnation are demonstrated...

  18. Depth oscillations of electronuclear reaction yield initiated by relativistic planar channeled electrons: quantum versus classical calculations

    Science.gov (United States)

    Eikhorn, Yu. L.; Korotchenko, K. B.; Pivovarov, Yu. L.; Tukhfatullin, T. A.

    2017-07-01

    The first experiment on electronuclear reaction initated by axially channeled 700 MeV electrons in a Si crystal [1] revealed remarkable depth oscillations of reaction yield. The effect was satisfactory explained [2] by computer simulations using binary collisions model. In this work the oscillations effect is investigated for planar channeled electrons in a Si crystal using the new computer code BCM-1.0 which allows both classical and quantum calculations of channeled electrons flux density.

  19. Ionic fragmentation channels in electron collisions of small molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Jens

    2009-01-28

    Dissociative Recombination (DR) is one of the most important loss processes of molecular ions in the interstellar medium (IM). Ion storage rings allow to investigate these processes under realistic conditions. At the Heidelberg test storage ring TSR a new detector system was installed within the present work in order to study the DR sub-process of ion pair formation (IPF). The new detector expands the existing electron target setup by the possibility to measure strongly deflected negative ionic fragments. At the TSR such measurements can be performed with a uniquely high energy resolution by independently merging two electron beams with the ion beam. In this work IPF of HD{sup +}, H{sub 3}{sup +} and HF{sup +} has been studied. In the case of HD{sup +} the result of the high resolution experiment shows quantum interferences. Analysis of the quantum oscillations leads to a new understanding of the reaction dynamics. For H{sub 3}{sup +} it was for the first time possible to distinguish different IPF channels and to detect quantum interferences in the data. Finally the IPF of HF{sup +} was investigated in an energy range, where in previous experiments no conclusive results could be obtained. (orig.)

  20. Theoretical Studies on the Electronic Structures and Properties of Complex Ceramic Crystals and Novel Materials

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Wai-Yim

    2012-01-14

    This project is a continuation of a long program supported by the Office of Basic Energy Science in the Office of Science of DOE for many years. The final three-year continuation started on November 1, 2005 with additional 1 year extension to October 30, 2009. The project was then granted a two-year No Cost Extension which officially ended on October 30, 2011. This report covers the activities within this six year period with emphasis on the work completed within the last 3 years. A total of 44 papers with acknowledgement to this grant were published or submitted. The overall objectives of this project are as follows. These objectives have been evolved over the six year period: (1) To use the state-of-the-art computational methods to investigate the electronic structures of complex ceramics and other novel crystals. (2) To further investigate the defects, surfaces/interfaces and microstructures in complex materials using large scale modeling. (3) To extend the study on ceramic materials to more complex bioceramic crystals. (4) To initiate the study on soft condensed matters including water and biomolecules. (5) To focus on the spectroscopic studies of different materials especially on the ELNES and XANES spectral calculations and their applications related to experimental techniques. (6) To develop and refine computational methods to be effectively executed on DOE supercomputers. (7) To evaluate mechanical properties of different crystals and those containing defects and relate them to the fundamental electronic structures. (8) To promote and publicize the first-principles OLCAO method developed by the PI (under DOE support for many years) for applications to large complex material systems. (9) To train a new generation of graduate students and postdoctoral fellows in modern computational materials science and condensed matter physics. (10) To establish effective international and domestic collaborations with both experimentalists and theorists in materials

  1. Large-angle channeling radiation from relativistic electrons in optically transparent crystals

    Science.gov (United States)

    Korotchenko, K. B.; Pivovarov, Yu. L.

    2018-02-01

    In the work within the frame of quantum electrodynamics are obtained new formulae describing the large-angle photon emission from channeled electrons with taking into account of the dispersion of refractive index. Calculations based on these formulae show that the spectral and angular distributions of large-angle optical and ultraviolet radiation from planar channeled sub-GeV electrons in optically transparent crystal reflect the band structure of transverse energy levels of channeled electrons. Comparison with ordinary Cherenkov radiation spectrum reveals that channeling (depending on the beam energy) leads to sufficient change of the large-angle emission spectrum.

  2. Measurement and modelling of the defect chemistry and transport properties of ceramic oxide mixed ionic and electronic conductors

    DEFF Research Database (Denmark)

    Dalslet, Bjarke Thomas

    2008-01-01

    The subject of this thesis is ceramic mixed ionic and electronic conductors (MIECs). MIECs have potential uses, such as solid oxygen permeation membranes, as catalysts, and as components in fuel cells. The MIECs examined in this thesis are all oxide ion conducting materials. This thesis describes...

  3. Relativistic laser hosing instability suppression and electron acceleration in a preformed plasma channel

    Science.gov (United States)

    Huang, T. W.; Zhou, C. T.; Zhang, H.; Wu, S. Z.; Qiao, B.; He, X. T.; Ruan, S. C.

    2017-04-01

    The hosing processes of a relativistic laser pulse, electron acceleration, and betatron radiation in a parabolic plasma channel are investigated in the direct laser acceleration regime. It is shown that the laser hosing instability would result in the generation of a randomly directed off-axis electron beam and radiation source with a large divergence angle. While employing a preformed parabolic plasma channel, the restoring force provided by the plasma channel would correct the perturbed laser wave front and thus suppress the hosing instability. As a result, the accelerated electron beam and the emitted photons are well guided and concentrated along the channel axis. The employment of a proper plasma density channel can stably guide the relativistically intense laser pulse and greatly improve the properties of the electron beam and radiation source. This scheme is of great interest for the generation of high quality electron beams and radiation sources.

  4. Charge compensation by in-situ heating for insulating ceramics in scanning electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Li [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Ji, Yuan, E-mail: jiyuan@bjut.edu.cn [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Wei, Bin; Zhang, Yinqi; Fu, Jingyong; Xu, Xuedong; Han, Xiaodong [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)

    2009-10-15

    With a steady temperature increase under high vacuum (HV) in an environmental scanning electronic microscope, we observed charge-free characterization and fine secondary electron (SE) images in focus for insulating ceramics (alumina (Al{sub 2}O{sub 3}), aluminum nitride (AlN), pure magnesium silicate (Mg{sub 2}SiO{sub 4})). The sample current I{sub sc} increased from -8.18x10{sup -13} to 2.76x10{sup -7} A for Al{sub 2}O{sub 3} and -9.28x10{sup -12} to 2.77x10{sup -6} A for AlN with the temperature increased from 298 to 633 K. The surface conductance {sigma} increased from 5.6x10{sup -13} to 5.0x10{sup -11}/{Omega} for Al{sub 2}O{sub 3} and 1.1x10{sup -12} to 1.0x10{sup -7}/{Omega} for AlN with the temperature increased from 363 to 593 K. The SE image contrast obtained via heating approach in high vacuum with an Everhart-Thornley SE-detector was better than that via conventional approach of electron-ion neutralization in low vacuum (LV) with a gaseous SE-detector. The differences of compensation temperatures for charge effects indicate dielectric and thermal properties, and band structures of insulators. The charge compensation mechanisms of heating approach mainly relate to accelerated release of trapped electrons on insulating surface and to increase of electron emission yield by heating.

  5. Comparative analysis of electrophysical properties of ceramic tantalum pentoxide coatings, deposited by electron beam evaporation and magnetron sputtering methods

    Science.gov (United States)

    Donkov, N.; Mateev, E.; Safonov, V.; Zykova, A.; Yakovin, S.; Kolesnikov, D.; Sudzhanskaya, I.; Goncharov, I.; Georgieva, V.

    2014-12-01

    Ta2O5 ceramic coatings have been deposited on glass substrates by e-beam evaporation and magnetron sputtering methods. For the magnetron sputtering process Ta target was used. X-ray diffraction measurements show that these coatings are amorphous. XPS survey spectra of the ceramic Ta2O5 coatings were obtained. All spectra consist of well-defined XPS lines of Ta 4f, 4d, 4p and 4s; O 1s; C 1s. Ta 4f doublets are typical for Ta2O5 coatings with two main peaks. Scanning electron microscopy and atomic force microscopy images of the e-beam evaporated and magnetron sputtered Ta2O5 ceramic coatings have revealed a relatively flat surface with no cracks. The dielectric properties of the tantalum pentoxide coatings have been investigated in the frequency range of 100 Hz to 1 MHz. The electrical behaviour of e-beam evaporated and magnetron sputtered Ta2O5 ceramic coatings have also been compared. The deposition process conditions principally effect the structure parameters and electrical properties of Ta2O5 ceramic coatings. The coatings deposited by different methods demonstrate the range of dielectric parameters due to the structural and stoichiometric composition changes

  6. Electronic identification of cattle: interference in the reading of ceramic bolus transponders in the presence of ruminal magnets

    Directory of Open Access Journals (Sweden)

    N. Ferri

    2004-01-01

    Full Text Available The authors assess the reading performances of electronic transponders encased in ceramic boluses, utilised as identification (ID instruments for production ruminants, and the possible influence of the magnet, which is located in the fore-stomach of ruminants. Research has been conducted in free-range Friesian dairy herds in the Teramo Province. The use of the electronic bolus to identify cattle appears to provide better guarantees than the traditional methods used and meets the requirements of identifying individual animals at the farm level. Results demonstrate how the presence of both the magnet and the ceramic bolus, equipped with a transponder, makes it difficult, and sometimes impossible, to read the code. However, the electronic ID system is the best instrument currently available. The authors confirm the validity of this method and highlight some problems that still need to be solved.

  7. Direct cooled power electronics substrate

    Science.gov (United States)

    Wiles, Randy H [Powell, TN; Wereszczak, Andrew A [Oak Ridge, TN; Ayers, Curtis W [Kingston, TN; Lowe, Kirk T [Knoxville, TN

    2010-09-14

    The disclosure describes directly cooling a three-dimensional, direct metallization (DM) layer in a power electronics device. To enable sufficient cooling, coolant flow channels are formed within the ceramic substrate. The direct metallization layer (typically copper) may be bonded to the ceramic substrate, and semiconductor chips (such as IGBT and diodes) may be soldered or sintered onto the direct metallization layer to form a power electronics module. Multiple modules may be attached to cooling headers that provide in-flow and out-flow of coolant through the channels in the ceramic substrate. The modules and cooling header assembly are preferably sized to fit inside the core of a toroidal shaped capacitor.

  8. Partial ceramic crowns. Influence of preparation design and luting material on margin integrity--a scanning electron microscopic study.

    Science.gov (United States)

    Federlin, Marianne; Sipos, C; Hiller, K-A; Thonemann, B; Schmalz, G

    2005-03-01

    This in vitro study examines the effects of three preparation designs and different luting agents on the marginal integrity of partial ceramic crowns. One hundred forty-four extracted human molars were prepared according to the following preparation designs: A. Coverage of functional cusps, B. Horizontal reduction of functional cusps and C. Complete reduction of functional cusps. Partial ceramic crowns (Vita Mark II, Cerec 3 System) were bonded to the cavities with: Variolink II/Excite (Vivadent), Panavia F/ED primer (Kuraray), Dyract/Prime and Bond NT (Detrey/Dentsply), and Fuji Plus/GC cavity conditioner (GC). The specimens were exposed to thermocycling and mechanical loading. Marginal adaptation was assessed on replicas using quantitative margin analysis in the scanning electron microscope (SEM). Significant differences were observed between the preparation designs in general. Coverage of functional cusps with preparation of butt joints and use of Variolink as luting material showed a tendency toward the lowest values for compromised adhesion, especially within the dentin. Significant differences could be determined between luting systems: resin-modified glass ionomer cement (RMGIC) caused fracture of the restorations and revealed higher values than all other luting materials for compromised adhesion at ceramic-luting agent and tooth-luting agent interfaces. The dentin-luting material interface, in general, showed higher percentages of compromised adhesion (38-100%) than enamel- and ceramic-luting material interfaces (0-30%). In conclusion, the SEM data indicate that, with adhesively bonded partial ceramic crowns, retentive preparation is not contraindicated and the choice of luting material is more relevant than the preparation design. Margins below the cemento-enamel junction reveal significant loss of adhesion in spite of adhesive luting techniques. The RMGIC cannot be recommended as a luting material for feldspathic partial ceramic crowns.

  9. Quantum ballistic transport by interacting two-electron states in quasi-one-dimensional channels

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Danhong [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117 (United States); Center for High Technology Materials, University of New Mexico, 1313 Goddard St SE, Albuquerque, New Mexico 87106 (United States); Gumbs, Godfrey [Center for High Technology Materials, University of New Mexico, 1313 Goddard St SE, Albuquerque, New Mexico 87106 (United States); Abranyos, Yonatan [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States); Pepper, Michael; Kumar, Sanjeev [Department of Electronic and Electrical Engineering, University College London, London, WC1E 7JE (United Kingdom); London Centre for Nanotechnology, 17-19 Gordon Street, London, WC1H 0AH (United Kingdom)

    2015-11-15

    For quantum ballistic transport of electrons through a short conduction channel, the role of Coulomb interaction may significantly modify the energy levels of two-electron states at low temperatures as the channel becomes wide. In this regime, the Coulomb effect on the two-electron states is calculated and found to lead to four split energy levels, including two anticrossing-level and two crossing-level states. Moreover, due to the interplay of anticrossing and crossing effects, our calculations reveal that the ground two-electron state will switch from one anticrossing state (strong confinement) to a crossing state (intermediate confinement) as the channel width gradually increases and then back to the original anticrossing state (weak confinement) as the channel width becomes larger than a threshold value. This switching behavior leaves a footprint in the ballistic conductance as well as in the diffusion thermoelectric power of electrons. Such a switching is related to the triple spin degeneracy as well as to the Coulomb repulsion in the central region of the channel, which separates two electrons away and pushes them to different channel edges. The conductance reoccurrence region expands from the weak to the intermediate confinement regime with increasing electron density.

  10. Electron paramagnetic resonance and photoluminescence investigation of europium local structure in oxyfluoride glass ceramics containing SrF2 nanocrystals

    Science.gov (United States)

    Antuzevics, A.; Kemere, M.; Krieke, G.; Ignatans, R.

    2017-10-01

    Different compositions of europium doped aluminosilicate oxyfluoride glass ceramics prepared in air atmosphere have been studied by electron paramagnetic resonance (EPR) and optical spectroscopy methods. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show presence of homogenously distributed SrF2 nanocrystals after the heat treatment of the precursor glass. Efficient Eu3+ incorporation in the high symmetry environment of glass ceramics is observed from the photoluminescence spectra. EPR spectra indicate Eu3+ → Eu2+ reduction upon precipitation of crystalline phases in the glass matrix. For composition abundant with Eu2+ in the glassy state such behaviour is not detected. Local structure around europium ions is discussed based on differences in chemical compositions.

  11. Identifying threading dislocations in GaN films and substrates by electron channelling.

    Science.gov (United States)

    Kamaladasa, Ranga J; Liu, Fang; Porter, Lisa M; Davis, Robert F; Koleske, Daniel D; Mulholland, Greg; Jones, Kenneth A; Picard, Yoosuf N

    2011-12-01

    Electron channelling contrast imaging of threading dislocations in GaN (0002) substrates and epitaxial films has been demonstrated using a conventional polepiece-mounted backscatter detector in a commercial scanning electron microscope. The influence of accelerating voltage and diffraction vector on contrast features denoting specific threading dislocation types has been studied. As confirmed by coordinated transmission electron microscopy analysis, electron channelling contrast imaging contrast features for edge-type threading dislocations are spatially smaller than mixed-type threading dislocations in GaN. This ability to delineate GaN edge threading dislocations from mixed type was also confirmed by defect-selective etch processing using molten MgO/KOH. This study validates electron channelling contrast imaging as a nondestructive and widely accessible method for spatially mapping and identifying dislocations in GaN with wider applicability for other single-crystal materials. © 2011 The Authors Journal of Microscopy © 2011 Royal Microscopical Society.

  12. Measuring Fracture Times Of Ceramics

    Science.gov (United States)

    Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

    1989-01-01

    Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

  13. Reliable Direct Bond Copper Ceramic Packages for High Temperature Power Electronics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed program will develop highly reliable, hermetic, Si3N4 ceramic multichip modules to integrate commercially available SiC power devices to build power...

  14. Composition and microstructure of maiolica from the museum of ceramics in Ascoli Piceno (Italy): evidences by electron microscopy and microanalysis

    Science.gov (United States)

    Gulmini, M.; Scognamiglio, F.; Roselli, G.; Vaggelli, G.

    2015-09-01

    The present work focuses on majolica objects from the collection of the museum of ceramic in Ascoli Piceno (Italy). The scientific investigation was performed on fragments detached from seven maiolicas attributed to the Castelli production (Abruzzi region) and one majolica from the Ascoli Piceno production (Marche region). The Castelli artifacts (late sixteenth-early eighteenth century) belong to the decorated style known as " compendiario." The piece from Ascoli Piceno recalls the decoration style of the other considered objects and is attributable to the "Paci" manufacture (first half of the nineteenth century). The selected objects were investigated by fiber optics reflectance spectroscopy, micro-X-ray fluorescence spectroscopy and scanning electron microscopy coupled with electron-dispersive X-ray spectrometry. The ceramic bodies of all objects are calcareous, whereas the glazes are lead-alkali type opacified by tin dioxide. Blue and purplish-red decorations were obtained by cobalt and manganese compounds dissolved in the glaze, respectively. Yellow and orange decorations were obtained by particles of lead antimonate and hematite. Finally, black decorations were obtained using compounds rich in manganese and iron. The study contributes to knowledge on the production of Castelli ceramics and presents first archaeometric data on the maiolica production from Ascoli Piceno. The scientific examination highlights continuity with the Renaissance production, and the joint contribution of the three analytical techniques suggests distinctive features among different productions, thus integrating and refining the information obtained by the art-historical study.

  15. Electronic Literacies and TESOL Graduate Students from Korea: New Channels for Navigating Cultures of Learning.

    Science.gov (United States)

    Skilton-Sylvester, Ellen

    2001-01-01

    Drawing on the ethnography of communication, addresses the role of electronic channels for meaning making among Korean students in graduate TESOL classes in the United States. Looks at the ways that these electronic literacies provide opportunities for navigating Korean and U.S. cultures of learning. (Author/VWL)

  16. Electron-deficient fullerenes in triple-channel photosystems.

    Science.gov (United States)

    López-Andarias, Javier; Bolag, Altan; Nançoz, Christoph; Vauthey, Eric; Atienza, Carmen; Sakai, Naomi; Martín, Nazario; Matile, Stefan

    2015-05-01

    Fullerenes of increasing electron deficiency are designed, synthesized and evaluated in multicomponent surface architectures to ultimately build gradients in LUMO levels with nine components over 350 meV down to -4.22 eV.

  17. Coulomb blockade in a Si channel gated by an Al single-electron transistor

    OpenAIRE

    Sun, L.; Brown, K. R.; Kane, B. E.

    2007-01-01

    We incorporate an Al-AlO_x-Al single-electron transistor as the gate of a narrow (~100 nm) metal-oxide-semiconductor field-effect transistor (MOSFET). Near the MOSFET channel conductance threshold, we observe oscillations in the conductance associated with Coulomb blockade in the channel, revealing the formation of a Si single-electron transistor. Abrupt steps present in sweeps of the Al transistor conductance versus gate voltage are correlated with single-electron charging events in the Si t...

  18. Enhanced acceleration of injected electrons in a laser-beat-wave-induced plasma channel.

    Science.gov (United States)

    Tochitsky, S Ya; Narang, R; Filip, C V; Musumeci, P; Clayton, C E; Yoder, R B; Marsh, K A; Rosenzweig, J B; Pellegrini, C; Joshi, C

    2004-03-05

    Enhanced energy gain of externally injected electrons by a approximately 3 cm long, high-gradient relativistic plasma wave (RPW) is demonstrated. Using a CO2 laser beat wave of duration longer than the ion motion time across the laser spot size, a laser self-guiding process is initiated in a plasma channel. Guiding compensates for ionization-induced defocusing (IID) creating a longer plasma, which extends the interaction length between electrons and the RPW. In contrast to a maximum energy gain of 10 MeV when IID is dominant, the electrons gain up to 38 MeV energy in a laser-beat-wave-induced plasma channel.

  19. P -wave coupled channel effects in electron-positron annihilation

    Science.gov (United States)

    Du, Meng-Lin; Meißner, Ulf-G.; Wang, Qian

    2016-11-01

    P -wave coupled channel effects arising from the D D ¯, D D¯ *+c .c . , and D*D¯* thresholds in e+e- annihilations are systematically studied. We provide an exploratory study by solving the Lippmann-Schwinger equation with short-ranged contact potentials obtained in the heavy quark limit. These contact potentials can be extracted from the P -wave interactions in the e+e- annihilations, and then be employed to investigate possible isosinglet P -wave hadronic molecules. In particular, such an investigation may provide information about exotic candidates with quantum numbers JPC=1-+ . In the mass region of the D D ¯, D D¯ *+c .c . , and D*D¯* thresholds, there are two quark model bare states, i.e. the ψ (3770 ) and ψ (4040 ), which are assigned as (13D1) and (31S1) states, respectively. By an overall fit of the cross sections of e+e-→D D ¯, D D¯ *+c .c . , D*D¯*, we determine the physical coupling constants to each channel and extract the pole positions of the ψ (3770 ) and ψ (4040 ). The deviation of the ratios from that in the heavy quark spin symmetry (HQSS) limit reflects the HQSS breaking effect due to the mass splitting between the D and the D*. Besides the two poles, we also find a pole a few MeV above the D D¯ *+c .c . threshold which can be related to the so-called G (3900 ) observed earlier by BABAR and Belle. This scenario can be further scrutinized by measuring the angular distribution in the D*D¯* channel with high luminosity experiments.

  20. Fundamental and experimental aspects of diffraction for characterizing dislocations by electron channeling contrast imaging in scanning electron microscope

    OpenAIRE

    Kriaa, H.; Guitton, A.; Maloufi, N.

    2017-01-01

    Nowadays Field Emission Gun-Scanning Electron Microscopes provide detailed crystallographic information with high spatial and angular resolutions, and allow direct observation of crystalline defects, such as dislocations, through an attractive technique called Electron Channeling Contrast Imaging (ECCI). Dislocations play a crucial role in the properties of materials and ECCI has naturally emerged as an adapted tool for characterizing defects in bulk specimen. Nevertheless, fine control of th...

  1. Extremely intense laser-based electron acceleration in a plasma channel

    Science.gov (United States)

    Vranic, Marija; Fonseca, Ricardo A.; Silva, Luis O.

    2018-03-01

    Laser pulses of extreme intensities (I> {10}22 {{W}} {{cm}}-2) are about to become available in the laboratory. The prepulse of such a laser can induce a plasma expansion that generates a low-density channel in near-critical gas jets. We present a study of channel formation and subsequent direct laser acceleration of electrons within the pre-formed channel. Radiation reaction affects the acceleration in several ways. It first interferes with the motion of the return current on the channel walls. In addition, it reduces the radial expelling efficiency of the transverse ponderomotive force, leading to the radiative trapping of particles near the channel axis. These particles then interact with the peak laser intensity and can attain multi-GeV energies.

  2. RADIATIVE ELECTRON CAPTURE BY FAST HIGHLY STRIPPED HEAVY IONS CHANNELED IN A THIN CRYSTAL

    OpenAIRE

    Andriamonje, S; Chevallier, M; Cohen, C; Dural, J.; Gaillard, M; Genre, R.; Hage-ali, M.; Kirsch, R; L'hoir, A.; Mazuy, B.; Mory, J.; Moulin, J; Poizat, J.-C.; Remillieux, J; Schmaus, Didier

    1989-01-01

    Interaction of moving ions with single crystals is known to be very sensitive to the orientation of the incident beam with respect to the crystalline directions of the target. We have shown that channeling conditions strongly modify the slowing down and the charge exchange processes of high energy heavy ions. The reason is that channeled particles are prevented from approaching the target atoms, and then can interact only with loosely bound target electrons. This results not only in drastical...

  3. Design of a channel board used in an electronic warfare target simulator

    OpenAIRE

    Andersson, Peter

    2006-01-01

    A channel board was designed for a DRFM circuit. The DRFM is implemented in a Virtex-4 FPGA from Xilinx. In the future a similar channel board is intended to be used for target echo generation in ELSI which is an electronic warfare simulator at Saab Bofors Dynamics in Linköping. Besides the DRFM circuit the channel board consists of analog-to-digital converters, digital-to-analog converters, Ethernet plug-in board with a microcontroller, voltage regulators, FPGA configuration memory, voltage ...

  4. Electronic stopping power of slow-light channeling ions in ZnTe from first principles

    Science.gov (United States)

    Li, Chang-kai; Mao, Fei; Wang, Feng; Fu, Yan-long; Ouyang, Xiao-ping; Zhang, Feng-Shou

    2017-05-01

    Nonadiabatic dynamics simulations are performed to investigate the electronic stopping power of a helium ion moving through ZnTe crystalline thin films under channeling conditions. Using ab initio time-dependent density-functional theory, we found by direct simulation that electronic stopping power versus projectile velocity deviates from velocity proportionality and displays a transition between two velocity regimes for helium ions channeling along middle crystalline axes in and channels and also in a channel with low-impact parameters. This transition causes a change in the slope of the energy loss versus ion velocity curve at a characteristic velocity related to the impact parameter and the lattice plane spacing. It may be an indication of extra energy loss channel beyond the electron-hole excitation. To analyze it, we checked the charge transfer between the moving projectiles and host atoms. It is found that the soft transition between two velocity regimes can be attributed to the resonant coherent excitation stimulated by the time-periodic potential experienced by the channeling ion and also the charge exchange in close encounters between Helium ion and host atoms.

  5. Laser-wakefield acceleration of electron beams in a low density plasma channel

    Directory of Open Access Journals (Sweden)

    T. P. A. Ibbotson

    2010-03-01

    Full Text Available The generation of quasimonoenergetic electron beams, with energies greater than 500 MeV, in a laser-plasma accelerator driven by 2.5 J, 80 fs laser pulses guided in a low density plasma channel, is investigated. The laser energy required to achieve electron injection is found to depend strongly on the quality of the input laser focal spot. Simulations show that, although the matched spot size of the plasma channel is greater than the self-focused spot size, the channel assists relativistic self-focusing and enables electron injection to occur at lower plasma densities and laser powers than would be possible without a waveguide.

  6. Positrons vs electrons channeling in silicon crystal: energy levels, wave functions and quantum chaos manifestations

    Science.gov (United States)

    Shul'ga, N. F.; Syshchenko, V. V.; Tarnovsky, A. I.; Solovyev, I. I.; Isupov, A. Yu.

    2018-01-01

    The motion of fast electrons through the crystal during axial channeling could be regular and chaotic. The dynamical chaos in quantum systems manifests itself in both statistical properties of energy spectra and morphology of wave functions of the individual stationary states. In this report, we investigate the axial channeling of high and low energy electrons and positrons near [100] direction of a silicon crystal. This case is particularly interesting because of the fact that the chaotic motion domain occupies only a small part of the phase space for the channeling electrons whereas the motion of the channeling positrons is substantially chaotic for the almost all initial conditions. The energy levels of transverse motion, as well as the wave functions of the stationary states, have been computed numerically. The group theory methods had been used for classification of the computed eigenfunctions and identification of the non-degenerate and doubly degenerate energy levels. The channeling radiation spectrum for the low energy electrons has been also computed.

  7. Cyanated diazatetracene diimides with ultrahigh electron affinity for n-channel field effect transistors

    KAUST Repository

    Ye, Qun

    2013-03-15

    Several diazatetracene diimides with high electron affinity (up to 4.66 eV!) were prepared and well characterized. The LUMO energy level of these electron-deficient molecules was found to be closely related to their material stability. Compound 7 with ultrahigh electron affinity suffered from reduction and hydrolysis in the presence of silica gel or water. The stable compounds 3 and 6 showed n-channel FET behavior with an average electron mobility of 0.002 and 0.005 cm2 V-1 s-1, respectively, using a solution processing method. © 2013 American Chemical Society.

  8. Analysis of FIB-induced damage by electron channelling contrast imaging in the SEM.

    Science.gov (United States)

    Gutierrez-Urrutia, Ivan

    2017-01-01

    We have investigated the Ga+ ion-damage effect induced by focused ion beam (FIB) milling in a [001] single crystal of a 316 L stainless steel by the electron channelling contrast imaging (ECCI) technique. The influence of FIB milling on the characteristic electron channelling contrast of surface dislocations was analysed. The ECCI approach provides sound estimation of the damage depth produced by FIB milling. For comparison purposes, we have also studied the same milled surface by a conventional electron backscatter diffraction (EBSD) approach. We observe that the ECCI approach provides further insight into the Ga+ ion-damage phenomenon than the EBSD technique by direct imaging of FIB artefacts in the scanning electron microscope. We envisage that the ECCI technique may be a convenient tool to optimize the FIB milling settings in applications where the surface crystal defect content is relevant. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  9. Enhancing oxygen transport through Mixed-Ionic-and-Electronic-Conducting ceramic membranes

    Science.gov (United States)

    Yu, Anthony S.

    Ceramic membranes based on Mixed-Ionic-and-Electronic-Conducting (MIEC) oxides are capable of separating oxygen from air in the presence of an oxygen partial-pressure gradient. These MIEC membranes show great promise for oxygen consuming industrial processes, such as the production of syngas from steam reforming of natural gas (SRM), as well as for electricity generation in Solid Oxide Fuel Cells (SOFC). For both applications, the overall performance is dictated by the rate of oxygen transport across the membrane. Oxygen transport across MIEC membranes is composed of a bulk oxygen-ion diffusion process and surface processes, such as surface reactions and adsorption/desorption of gaseous reactants/products. The main goal of this thesis was to determine which process is rate-limiting in order to significantly enhance the overall rate of oxygen transport in MIEC membrane systems. The rate-limiting step was determined by evaluating the total resistance to oxygen transfer, Rtot. Rtot is the sum of a bulk diffusion resistance in the membrane itself, Rb, and interfacial loss components, Rs. Rb is a function of the membrane's ionic conductivity and thickness, while Rs arises primarily from slow surface-exchange kinetics that cause the P(O2) at the surfaces of the membrane to differ from the P(O 2) in the adjacent gas phases. Rtot can be calculated from the Nernst potential across the membrane and the measured oxygen flux. The rate-limiting process can be determined by evaluating the relative contributions of the various losses, Rs and Rb, to Rtot. Using this method, this thesis demonstrates that for most membrane systems, Rs is the dominating factor. In the development of membrane systems with high oxygen transport rates, thin membranes with high ionic conductivities are required to achieve fast bulk oxygen-ion diffusion. However, as membrane thickness is decreased, surface reaction kinetics become more important in determining the overall transport rate. The two

  10. Characterization of early-age hydration processes in lime-ceramic binders using isothermal calorimetry, X-ray diffraction and scanning electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jerman, Miloš; Tydlitát, Vratislav; Keppert, Martin; Čáchová, Monika; Černý, Robert, E-mail: cernyr@fsv.cvut.cz

    2016-06-10

    Highlights: • Early age hydration processes in lime-ceramic binders are analyzed within a wide range of component ratios. • The applied waste ceramic dust exhibits partial hydraulic properties, ettringite and calcite are formed. • Transition from tobermorite- to jennite-like structures is identified by SEM within the first 48 h. • The highest specific hydration heat after 300 h, 63 J/g, is measured for the binder containing 70% ceramic. • Substantial effect of the heat of wetting is observed, ranging from 10 J/g for lime to 3.9 J/g for ceramic. - Abstract: Early-age hydration processes in a lime-ceramic-water system are analyzed within the whole range of possible lime/ceramic ratios. The isothermal calorimetry shows a substantial effect of the heat of wetting on the total heat evolved, ranging from 10 J/g for lime to 3.9 J/g for ceramic. The highest specific hydration heat of 63 J/g during the analyzed 300-h hydration period exhibits the blended binder containing 70% ceramic and 30% lime which correlates well with the highest compressive and bending strengths of the paste prepared using this blend. Portlandite, ettringite and calcite are the main phases identified by the X-ray diffraction analysis after the hydration of ceramic-rich blends. According to the results of scanning electron microscopy, the initial course of pozzolanic reaction is for this type of binders characterized by the transition from tobermorite-like calcium-silicate-hydrate structures into jennite-like structures within the first 48 h. Blends with the ceramic content lower than 70% show a high portion of portlandite, calcite is present in low amount, and the jennite-like structures are observed after 48 h, following the initial formation of components with a very high Ca content. The favorable properties of the ceramic-rich blended binders can be explained by the partial hydraulic character of the ceramic. With the specific hydration heat of 29 J/g after 300 h and compressive strength

  11. Channeling radiation from relativistic electrons - Study of stacking faults and dislocations

    CERN Document Server

    Pathak, A P; Prakash-Goteti, L N S

    2002-01-01

    The discrete nature of the energy associated with channeled particles and consequent emission of channeling radiation has opened new applications in accelerator and atomic physics. The spontaneous transitions among various energy levels in the transverse space lead to what is known as channeling radiation. One-dimensional hydrogen atom model for continuum planar potential due to single plane is used for the case of planar channeled electrons to estimate the corresponding bound states in the potential well. The effects of extended defects like stacking faults (SFs) and dislocations on transitions among the various levels are studied by calculating the transition probabilities at the faulted region, i.e. at the SF boundary for the case of SF and distorted region of the dislocation. The obstruction and distortion effects of these extended defects are incorporated suitably to obtain initial and final populations of the eigenstates.

  12. Quasi-phase-matched acceleration of electrons in a corrugated plasma channel

    Directory of Open Access Journals (Sweden)

    S. J. Yoon

    2012-08-01

    Full Text Available A laser pulse propagating in a corrugated plasma channel is composed of spatial harmonics whose phase velocities can be subluminal. The phase velocity of a spatial harmonic can be matched to the speed of a relativistic electron resulting in direct acceleration by the guided laser field in a plasma waveguide and linear energy gain over the interaction length. Here we examine the fully self-consistent interaction of the laser pulse and electron beam using particle-in-cell (PIC simulations. For low electron beam densities, we find that the ponderomotive force of the laser pulse pushes plasma channel electrons towards the propagation axis, which deflects the beam electrons. When the beam density is high, the space charge force of the beam drives the channel electrons off axis, providing collimation of the beam. In addition, we consider a ramped density profile for lowering the threshold energy for trapping in a subluminal spatial harmonic. By using a density ramp, the trapping energy for a normalized vector potential of a_{0}=0.1 is reduced from a relativistic factor γ_{0}=170 to γ_{0}=20.

  13. Lattice Location of Radioactive Probes in Semiconductors and Metals by Electron and Positron Channelling

    CERN Multimedia

    2002-01-01

    The channelling effect of decay-electrons and positrons is used for the localization of radioactive impurities implanted into single crystals. Because of the low implantation doses and the variety of different isotopes available at ISOLDE, this technique is especially suited for applications in semiconducting materials. \\\\ \\\\ Channelling measurements in Si, GaAs and GaP implanted with In-, Cd- and Xe-isotopes have demonstrated that impurity lattice sites can be studied directly after implantation without any annealing. The electron-channelling technique can be ideally combined with hyperfine interaction techniques like Moessbauer s This was shown for the formation of In-vacancy complexes in ion-implanted Ni. \\\\ \\\\ We intend to continue the lattice location measurements in semiconductors implanted with various radioactive impurities of Cd, In, Sn, Sb and Te.

  14. Field-reversed bubble in deep plasma channels for high quality electron acceleration

    CERN Document Server

    Pukhov, A; Tueckmantel, T; Thomas, J; Yu, I; Kostyukov, Yu

    2014-01-01

    We study hollow plasma channels with smooth boundaries for laser-driven electron acceleration in the bubble regime. Contrary to the uniform plasma case, the laser forms no optical shock and no etching at the front. This increases the effective bubble phase velocity and energy gain. The longitudinal field has a plateau that allows for mono-energetic acceleration. We observe as low as 10−3 r.m.s. relative witness beam energy uncertainty in each cross-section and 0.3% total energy spread. By varying plasma density profile inside a deep channel, the bubble fields can be adjusted to balance the laser depletion and dephasing lengths. Bubble scaling laws for the deep channel are derived. Ultra-short pancake-like laser pulses lead to the highest energies of accelerated electrons per Joule of laser pulse energy.

  15. Fundamental and experimental aspects of diffraction for characterizing dislocations by electron channeling contrast imaging in scanning electron microscope.

    Science.gov (United States)

    Kriaa, H; Guitton, A; Maloufi, N

    2017-08-29

    Nowadays Field Emission Gun-Scanning Electron Microscopes provide detailed crystallographic information with high spatial and angular resolutions, and allow direct observation of crystalline defects, such as dislocations, through an attractive technique called Electron Channeling Contrast Imaging (ECCI). Dislocations play a crucial role in the properties of materials and ECCI has naturally emerged as an adapted tool for characterizing defects in bulk specimen. Nevertheless, fine control of the channeling conditions is absolutely required to get strong dislocation contrast for achieving comprehensive analysis. In this work, experiment-assisted fundamental aspects of the origin of dislocation contrast are studied. Experimentally, the potential of ECCI is explored in several dislocation configurations in Interstitial-Free steel (Fe - 1% Si) used as a model material. Full interpretations of dislocation contrast in (g, -g) and its evolution along the Kikuchi band are shown. Furthermore, a dislocation dipole is observed and fully characterized for the first time in an SEM.

  16. Temperature and energy effects on secondary electron emission from SiC ceramics induced by Xe17+ions.

    Science.gov (United States)

    Zeng, Lixia; Zhou, Xianming; Cheng, Rui; Wang, Xing; Ren, Jieru; Lei, Yu; Ma, Lidong; Zhao, Yongtao; Zhang, Xiaoan; Xu, Zhongfeng

    2017-07-25

    Secondary electron emission yield from the surface of SiC ceramics induced by Xe 17+ ions has been measured as a function of target temperature and incident energy. In the temperature range of 463-659 K, the total yield gradually decreases with increasing target temperature. The decrease is about 57% for 3.2 MeV Xe 17+ impact, and about 62% for 4.0 MeV Xe 17+ impact, which is much larger than the decrease observed previously for ion impact at low charged states. The yield dependence on the temperature is discussed in terms of work function, because both kinetic electron emission and potential electron emission are influenced by work function. In addition, our experimental data show that the total electron yield gradually increases with the kinetic energy of projectile, when the target is at a constant temperature higher than room temperature. This result can be explained by electronic stopping power which plays an important role in kinetic electron emission.

  17. Scanning electron microscopical observation of an osteoblast/osteoclast co-culture on micropatterned orthopaedic ceramics

    Directory of Open Access Journals (Sweden)

    Mansur Halai

    2014-09-01

    Full Text Available In biomaterial engineering, the surface of an implant can influence cell differentiation, adhesion and affinity towards the implant. On contact with an implant, bone marrow–derived mesenchymal stromal cells demonstrate differentiation towards bone forming osteoblasts, which can improve osteointegration. The process of micropatterning has been shown to improve osteointegration in polymers, but there are few reports surrounding ceramics. The purpose of this study was to establish a co-culture of bone marrow–derived mesenchymal stromal cells with osteoclast progenitor cells and to observe the response to micropatterned zirconia toughened alumina ceramics with 30 µm diameter pits. The aim was to establish whether the pits were specifically bioactive towards osteogenesis or were generally bioactive and would also stimulate osteoclastogenesis that could potentially lead to osteolysis. We demonstrate specific bioactivity of micropatterns towards osteogenesis, with more nodule formation and less osteoclastogenesis compared to planar controls. In addition, we found that that macrophage and osteoclast-like cells did not interact with the pits and formed fewer full-size osteoclast-like cells on the pitted surfaces. This may have a role when designing ceramic orthopaedic implants.

  18. The complementary use of electron backscatter diffraction and ion channelling imaging for the characterization of nanotwins

    DEFF Research Database (Denmark)

    Alimadadi, Hossein; da Silva Fanta, Alice Bastos; Pantleon, Karen

    2013-01-01

    On the example of electrodeposited nickel films, it is shown that unique information on twins with dimensions on the nanoscale can be obtained by suitable combination of ion channelling imaging and electron backscatter diffraction analysis, whereas both (routine) single techniques cannot meet...... the requirements for analysis of these films. High‐resolution electron backscatter diffraction is inadequate for full characterization of nanotwins, but image quality maps obtained from electron backscatter diffraction at least yield a qualitative estimation of the location and number of nanotwins. Complementing...... this information with ion channelling imaging provides more representative insights into the microstructure, because it supplements the quantitative investigation of the number and width of twin lamellae with additional crystallographic orientation analysis provided by EBSD. To this end, two methods for adjusting...

  19. Simulation of cooling efficiency via miniaturised channels in multilayer LTCC for power electronics

    Science.gov (United States)

    Pietrikova, Alena; Girasek, Tomas; Lukacs, Peter; Welker, Tilo; Müller, Jens

    2017-03-01

    The aim of this paper is detailed investigation of thermal resistance, flow analysis and distribution of coolant as well as thermal distribution inside multilayer LTCC substrates with embedded channels for power electronic devices by simulation software. For this reason four various structures of internal channels in the multilayer LTCC substrates were designed and simulated. The impact of the volume flow, structures of channels, and power loss of chip was simulated, calculated and analyzed by using the simulation software Mentor Graphics FloEFDTM. The structure, size and location of channels have the significant impact on thermal resistance, pressure of coolant as well as the effectivity of cooling power components (chips) that can be placed on the top of LTCC substrate. The main contribution of this paper is thermal analyze, optimization and impact of 4 various cooling channels embedded in LTCC multilayer structure. Paper investigate, the effect of volume flow in cooling channels for achieving the least thermal resistance of LTCC substrate that is loaded by power thermal chips. Paper shows on the impact of the first chips thermal load on the second chip as well as. This possible new technology could ensure in the case of practical realization effective cooling and increasing reliability of high power modules.

  20. Determination of gas temperature in the plasmatron channel according to the known distribution of electronic temperature

    Directory of Open Access Journals (Sweden)

    Gerasimov Alexander V.

    2013-01-01

    Full Text Available An analytical method to calculate the temperature distribution of heavy particles in the channel of the plasma torch on the known distribution of the electronic temperature has been proposed. The results can be useful for a number of model calculations in determining the most effective conditions of gas blowing through the plasma torch with the purpose of heating the heavy component. This approach allows us to understand full details about the heating of cold gas, inpouring the plasma, and to estimate correctly the distribution of the gas temperature inside the channel.

  1. Analyses of electron runaway in front of the negative streamer channel

    DEFF Research Database (Denmark)

    Babich, L. P.; Bochkov, E. I.; Kutsyk, I. M.

    2017-01-01

    , which allows the electric field to reach magnitudes, required for a generation of significant RE fluxes and associated bremsstrahlung, when the ionization wave propagates in a narrow, ionized channel created by a previous streamer. Under such conditions we compute the production rate of REs per unit......-emitting ionization wave independent of the initial electron concentration. Thus, the streamer coronas of the leaders are probable sources of REs producing the observed high-energy radiation. To prove these predictions, new simulations are planned, which would show explicitly that the pre-ionization in front...... of the channel via REs will lead to the ionization wave propagation self-consistent with REs generation....

  2. Scanning electron microscope comparative surface evaluation of glazed-lithium disilicate ceramics under different irradiation settings of Nd:YAG and Er:YAG lasers.

    Science.gov (United States)

    Viskic, Josko; Jokic, Drazen; Jakovljevic, Suzana; Bergman, Lana; Ortolan, Sladana Milardovic; Mestrovic, Senka; Mehulic, Ketij

    2018-01-01

    To evaluate the surface of glazed lithium disilicate dental ceramics after irradiation under different irradiation settings of Nd:YAG and Er:YAG lasers using a scanning electron microscope (SEM). Three glazed-press lithium disilicate ceramic discs were treated with HF, Er:YAG, and Nd:YAG, respectively. The laser-setting variables tested were laser mode, repetition rate (Hz), power (W), time of exposure (seconds), and laser energy (mJ). Sixteen different variable settings were tested for each laser type, and all the samples were analyzed by SEM at 500× and 1000× magnification. Surface analysis of the HF-treated sample showed a typical surface texture with a homogenously rough pattern and exposed ceramic crystals. Er:YAG showed no effect on the surface under any irradiation setting. The surface of Nd:YAG-irradiated samples showed cracking, melting, and resolidifying of the ceramic glaze. These changes became more pronounced as the power increased. At the highest power setting (2.25 W), craters on the surface with large areas of melted or resolidified glaze surrounded by globules were visible. However, there was little to no exposure of ceramic crystals or visible regular surface roughening. Neither Er:YAG nor Nd:YAG dental lasers exhibited adequate surface modification for bonding of orthodontic brackets on glazed lithium disilicate ceramics compared with the control treated with 9.5% HF.

  3. Calculating the electron temperature in the lightning channel by continuous spectrum

    Science.gov (United States)

    Xiangcheng, DONG; Jianhong, CHEN; Xiufang, WEI; Ping, YUAN

    2017-12-01

    Based on the theory of plasma continuous radiation, the relationship between the emission intensity of bremsstrahlung and recombination radiation and the plasma electron temperature is obtained. During the development process of a return stroke of ground flash, the intensity of continuous radiation spectrum is separated on the basis of the spectrums with obviously different luminous intensity at two moments. The electron temperature of the lightning discharge channel is obtained through the curve fitting of the continuous spectrum intensity. It is found that electron temperature increases with the increase of wavelength and begins to reduce after the peak. The peak temperature of the two spectra is close to 25 000 K. To be compared with the result of discrete spectrum, the electron temperature is fitted by the O I line and N II line of the spectrum respectively. The comparison shows that the high temperature value is in good agreement with the temperature of the lightning core current channel obtained from the ion line information, and the low temperature at the high band closes to the calculation result of the atomic line, at a low band is lower than the calculation of the atomic line, which reflects the temperature of the luminous channel of the outer corona.

  4. Computer simulation of electron-positron pair production by channeling radiation in amorphous converter

    Science.gov (United States)

    Abdrashitov, S. V.; Bogdanov, O. V.; Dabagov, S. B.; Pivovarov, Yu L.; Tukhfatullin, T. A.

    2016-07-01

    We consider the radiator-converter approach at 200 MeV channeled electrons (the SPARC_LAB LNF facility energies) for the case of using W crystalline radiator and W amorphous converter. A comparison of the positron production by the axial channeling radiation and the bremsstrahlung is performed. The positron stopping in the convertor is studied by means of computer simulations. It is shown that for the maximum yield of positrons the thickness of the W amorphous converter should be taken 0.35 cm in the case of using the axial channeling radiation resulting to total yield of positrons 5 10-3 e+/e- and 0.71 cm in the case of using the bremsstrahlung resulting to total yield of positrons 3.3 10-3 e+/e-.

  5. The Low Pressure Gas Effects On The Potency Of An Electron Beam On Ceramic Fabric Materials For Space Welding

    Science.gov (United States)

    Nunes, Arthur C., Jr.; Fragomeni, James M.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    This investigation was undertaken to evaluate if molten metal or electron beam impingement could damage or burn through the fabric of the astronauts Extravehicular Mobility Unit (EMU) during electron beam welding exercises performed in space. An 8 kilovolt electron beam with a current in the neighborhood of 100 milliamps from the Ukrainian space welding "Universal Hand Tool" burned holes in Nextel AF-62 ceramic cloth designed to withstand temperatures up to 1427 C. The burnthrough time was on the order of 8 seconds at standoff distances between UHT and cloth ranging from 6 to 24 inches. At both closer (2") and farther (48") standoff distances the potency of the beam against the cloth declined and the burnthrough time went up significantly. Prior to the test it had been expected that the beam would lay down a static charge on the cloth and be deflected without damaging the cloth. The burnthrough is thought to be an effect of partial transmission of beam power by a stream of positive ions generated by the high voltage electron beam from contaminant gas in the "vacuum" chamber. A rough quantitative theoretical computation appears to substantiate this possibility.

  6. Effect of sintering parameters using the central composite design method, electronic structure and physical properties of yttria-partially stabilized ZrO2 commercial ceramics

    Directory of Open Access Journals (Sweden)

    Mendes A.M.

    2017-02-01

    Full Text Available In this work, the effect of sintering parameters on electronic structure and physical properties of yttria-partially stabilized ZrO2 (YPSZ commercial ceramics has been studied using the central composite design (CCD method. The CCD method allows using empirical modelling with better fitting, by considering the interaction between both factors. Different temperature ranges and sintering times for processing of YPSZ ceramics have been used in order to evaluate the grain growth, hardness and volumetric shrinkage by the CCD method. X-ray diffraction patterns and Rietveld refinement data indicate that non-sintered YPSZ ceramics exhibits two phases related to tetragonal and monoclinic structures, while the sintered YPSZ ceramics exhibits a single phase related to a tetragonal structure. Moreover, the monoclinic structure presents zirconium (Zr atoms coordinated to seven oxygen (O atoms, while in the tetragonal structure Zr atoms are coordinated to eight O atoms. Field emission scanning electron microscopy images were employed to monitor the sintering and growth process. In addition, the response surfaces obtained from calculations presented the effect of thermal and kinetic variables on the physical properties such as average grain size, volumetric shrinkage and hardness of YPSZ ceramics.

  7. Modeling of high composition AlGaN channel high electron mobility transistors with large threshold voltage

    Energy Technology Data Exchange (ETDEWEB)

    Bajaj, Sanyam, E-mail: bajaj.10@osu.edu; Hung, Ting-Hsiang; Akyol, Fatih; Nath, Digbijoy; Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2014-12-29

    We report on the potential of high electron mobility transistors (HEMTs) consisting of high composition AlGaN channel and barrier layers for power switching applications. Detailed two-dimensional (2D) simulations show that threshold voltages in excess of 3 V can be achieved through the use of AlGaN channel layers. We also calculate the 2D electron gas mobility in AlGaN channel HEMTs and evaluate their power figures of merit as a function of device operating temperature and Al mole fraction in the channel. Our models show that power switching transistors with AlGaN channels would have comparable on-resistance to GaN-channel based transistors for the same operation voltage. The modeling in this paper shows the potential of high composition AlGaN as a channel material for future high threshold enhancement mode transistors.

  8. Position-sensitive Si pad detectors for electron emission channeling experiments

    CERN Document Server

    Wahl, Ulrich; Czermak, Adam; Jahn, S G; Jalocha, Pawel; Marques, J G; Rudge, Alan; Schopper, Florian; Carvalho-Soares, João; Vantomme, A; Weilhammer, Peter

    2004-01-01

    Position-sensitive detector systems, initially developed for the detection of X-rays, have been adapted for their use in electron emission channeling experiments. Each detection system consists of a 30.8x30.8 mm$^{2}$ 22x22 -pad Si detector, either of 0.3 mm, 0.5 mm or 1 mm thickness, four 128$-$channel preamplifier chips, a backplane trigger circuit, a sampling analog to digital converter, a digital signal processor, and a personal computer for data display and storage. The operational principle of these detection systems is described, and characteristic features such as energy and position resolution and maximum count rate, which have been determined from tests with conversion electrons and $\\beta^-\\!$ -particles in the energy range 40--600 keV, are presented.

  9. Gating machinery of InsP3R channels revealed by electron cryomicroscopy.

    Science.gov (United States)

    Fan, Guizhen; Baker, Matthew L; Wang, Zhao; Baker, Mariah R; Sinyagovskiy, Pavel A; Chiu, Wah; Ludtke, Steven J; Serysheva, Irina I

    2015-11-19

    Inositol-1,4,5-trisphosphate receptors (InsP3Rs) are ubiquitous ion channels responsible for cytosolic Ca(2+) signalling and essential for a broad array of cellular processes ranging from contraction to secretion, and from proliferation to cell death. Despite decades of research on InsP3Rs, a mechanistic understanding of their structure-function relationship is lacking. Here we present the first, to our knowledge, near-atomic (4.7 Å) resolution electron cryomicroscopy structure of the tetrameric mammalian type 1 InsP3R channel in its apo-state. At this resolution, we are able to trace unambiguously ∼85% of the protein backbone, allowing us to identify the structural elements involved in gating and modulation of this 1.3-megadalton channel. Although the central Ca(2+)-conduction pathway is similar to other ion channels, including the closely related ryanodine receptor, the cytosolic carboxy termini are uniquely arranged in a left-handed α-helical bundle, directly interacting with the amino-terminal domains of adjacent subunits. This configuration suggests a molecular mechanism for allosteric regulation of channel gating by intracellular signals.

  10. Structure of the BK potassium channel in a lipid membrane from electron cryomicroscopy.

    Science.gov (United States)

    Wang, Liguo; Sigworth, Fred J

    2009-09-10

    A long-sought goal in structural biology has been the imaging of membrane proteins in their membrane environments. This goal has been achieved with electron crystallography in those special cases where a protein forms highly ordered arrays in lipid bilayers. It has also been achieved by NMR methods in proteins up to 50 kilodaltons (kDa) in size, although milligram quantities of protein and isotopic labelling are required. For structural analysis of large soluble proteins in microgram quantities, an increasingly powerful method that does not require crystallization is single-particle reconstruction from electron microscopy of cryogenically cooled samples (electron cryomicroscopy (cryo-EM)). Here we report the first single-particle cryo-EM study of a membrane protein, the human large-conductance calcium- and voltage-activated potassium channel (BK), in a lipid environment. The new method is called random spherically constrained (RSC) single-particle reconstruction. BK channels, members of the six-transmembrane-segment (6TM) ion channel family, were reconstituted at low density into lipid vesicles (liposomes), and their function was verified by a potassium flux assay. Vesicles were also frozen in vitreous ice and imaged in an electron microscope. From images of 8,400 individual protein particles, a three-dimensional (3D) reconstruction of the BK channel and its membrane environment was obtained at a resolution of 1.7-2.0 nm. Not requiring the formation of crystals, the RSC approach promises to be useful in the structural study of many other membrane proteins as well.

  11. Structure of the channeling electrons wave functions under dynamical chaos conditions

    Energy Technology Data Exchange (ETDEWEB)

    Shul’ga, N.F. [National Science Center “Kharkov Institute of Physics and Technology”, 1, Akademicheskaya St., Kharkov 61108 (Ukraine); V.N. Karazin National University, 4, Svodody Sq., Kharkov 61022 (Ukraine); Syshchenko, V.V., E-mail: syshch@yandex.ru [Belgorod National Research University, 85, Pobedy St., Belgorod 308015 (Russian Federation); Tarnovsky, A.I. [Belgorod National Research University, 85, Pobedy St., Belgorod 308015 (Russian Federation); Isupov, A.Yu. [Laboratory of High Energy Physics, Joint Institute for Nuclear Research, 141980 Dubna, Moscow region (Russian Federation)

    2016-03-01

    The stationary wave functions of fast electrons axially channeling in the silicon crystal near [1 1 0] direction have been found numerically for integrable and non-integrable cases, for which the classical motion is regular and chaotic, respectively. The nodal structure of the wave functions in the quasi-classical region, where the energy levels density is high, is agreed with quantum chaos theory predictions.

  12. Ceramic Seal.

    Energy Technology Data Exchange (ETDEWEB)

    Smartt, Heidi A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Romero, Juan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Custer, Joyce Olsen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hymel, Ross W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Krementz, Dan [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Gobin, Derek [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Harpring, Larry [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Martinez-Rodriguez, Michael [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Varble, Don [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); DiMaio, Jeff [Tetramer Technologies, Pendleton, SC (United States); Hudson, Stephen [Tetramer Technologies, Pendleton, SC (United States)

    2016-11-01

    Containment/Surveillance (C/S) measures are critical to any verification regime in order to maintain Continuity of Knowledge (CoK). The Ceramic Seal project is research into the next generation technologies to advance C/S, in particular improving security and efficiency. The Ceramic Seal is a small form factor loop seal with improved tamper-indication including a frangible seal body, tamper planes, external coatings, and electronic monitoring of the seal body integrity. It improves efficiency through a self-securing wire and in-situ verification with a handheld reader. Sandia National Laboratories (SNL) and Savannah River National Laboratory (SRNL), under sponsorship from the U.S. National Nuclear Security Administration (NNSA) Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D), have previously designed and have now fabricated and tested Ceramic Seals. Tests have occurred at both SNL and SRNL, with different types of tests occurring at each facility. This interim report will describe the Ceramic Seal prototype, the design and development of a handheld standalone reader and an interface to a data acquisition system, fabrication of the seals, and results of initial testing.

  13. The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

    Science.gov (United States)

    Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

    2015-01-01

    Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.

  14. The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

    Directory of Open Access Journals (Sweden)

    Ling-Feng Mao

    Full Text Available Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.

  15. Micromechanisms of brittle fracture: STM, TEM and electron channeling analysis. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Gerberich, W.W.

    1997-01-01

    The original thrust of this grant was to apply newly developed techniques in scanning tunneling and transmission electron microscopy to elucidate the mechanism of brittle fracture. This grant spun-off several new directions in that some of the findings on bulk structural materials could be utilized on thin films or intermetallic single crystals. Modeling and material evaluation efforts in this grant are represented in a figure. Out of this grant evolved the field the author has designated as Contact Fracture Mechanics. By appropriate modeling of stress and strain distribution fields around normal indentations or scratch tracks, various measures of thin film fracture or decohesion and brittle fracture of low ductility intermetallics is possible. These measures of fracture resistance in small volumes are still evolving and as such no standard technique or analysis has been uniformly accepted. For brittle ceramics and ceramic films, there are a number of acceptable analyses such as those published by Lawn, Evans and Hutchinson. For more dissipative systems involving metallic or polymeric films and/or substrates, there is still much to be accomplished as can be surmised from some of the findings in the present grant. In Section 2 the author reviews the funding history and accomplishments associated mostly with bulk brittle fracture. This is followed by Section 3 which covers more recent work on using novel techniques to evaluate fracture in low ductility single crystals or thin films using micromechanical probes. Basically Section 3 outlines how the recent work fits in with the goals of defining contact fracture mechanics and gives an overview of how the several examples in Section 4 (the Appendices) fit into this framework.

  16. Electronic Properties of Alkali Metals Loaded into Channel-Type Zeolite L

    Science.gov (United States)

    Thi, P. T.; Nakano, T.; Sakamoto, Y.; Nozue, Y.

    2017-05-01

    Rb metal was loaded into dehydrated Rb-form zeolite L. The loading density of Rb atoms per unit cell, n, was changed up to 7.1. A resonant optical absorption-reflection band is observed at ≈1.0 eV in all samples. A new reflection band appears at ≈1.7 eV for n > 5. The 1.0 and 1.7 eV bands are assigned to the respective excitations from 1s to 1p and from 1p to 1d quantum states of s-electrons one-dimensionally confined in main-channels with an inside diameter of ≈1 nm. A temperature-dependent semiconducting resistivity is observed at n > 2, and is assigned to the inter-channel polaron hopping between metallic 1s and 1p states. Besides, a nearly metallic resistivity with the low thermal activation energy is observed at n > 5. The metallic conductivity is assigned to three-dimensional s-electrons in the 1d state. The metallic property in Rb-loaded zeolite L is more remarkable than those in K-loaded zeolite L. The difference is explained by the smaller ionization energy of Rb atom, which leads to a shallower one-dimensional confinement potential of main-channel and a smaller polaron effect.

  17. Channeling, Volume Reection and Gamma Emission Using 14GeV Electrons in Bent Silicon Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Benson, Brandon [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-14

    High energy electrons can be deflected with very tight bending radius using a bent silicon crystal. This produces gamma radiation. As these crystals can be thin, a series of bent silicon crystals with alternating direction has the potential to produce coherent gamma radiation with reasonable energy of the driving electron beam. Such an electron crystal undulator offers the prospect for higher energy radiation at lower cost than current methods. Permanent magnetic undulators like LCLS at SLAC National Accelerator Laboratory are expensive and very large (about 100 m in case of the LCLS undulator). Silicon crystals are inexpensive and compact when compared to the large magnetic undulators. Additionally, such a high energy coherent light source could be used for probing through materials currently impenetrable by x-rays. In this work we present the experimental data and analysis of experiment T523 conducted at SLAC National Accelerator Laboratory. We collected the spectrum of gamma ray emission from 14 GeV electrons on a bent silicon crystal counting single photons. We also investigated the dynamics of electron motion in the crystal i.e. processes of channeling and volume reflection at 14 GeV, extending and building off previous work. Our single photon spectrum for the amorphous crystal orientation is consistent with bremsstrahlung radiation and the volume reflection crystal orientation shows a trend consistent with synchrotron radiation at a critical energy of 740 MeV. We observe that in these two cases the data are consistent, but we make no further claims because of statistical limitations. We also extended the known energy range of electron crystal dechanneling length and channeling efficiency to 14 GeV.

  18. A multi-channel opto-electronic sensor to accurately monitor heart rate against motion artefact during exercise

    National Research Council Canada - National Science Library

    Alzahrani, Abdullah; Hu, Sijung; Azorin-Peris, Vicente; Barrett, Laura; Esliger, Dale; Hayes, Matthew; Akbare, Shafique; Achart, Jérôme; Kuoch, Sylvain

    2015-01-01

    This study presents the use of a multi-channel opto-electronic sensor (OEPS) to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare...

  19. Characterization of sediment from the dredging of storm water channels in the city of Salvador-BA, Brazil aiming to use in structural ceramics; Caracterizacao de sedimento proveniente de dragagem de canais pluviais do municipio de Salvador-BA visando sua utilizacao em ceramica estrutural

    Energy Technology Data Exchange (ETDEWEB)

    Santos, O.C.; Breitenbach, S.B.; Coelho, R.E., E-mail: engcruz@ig.com.br, E-mail: silviabb@ifba.edu.br, E-mail: rodrigoecoelho@gmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia da Bahia (IFBA), Salvador (Brazil); Andrade, J.C.S.; Sales Junior, J.C.C., E-mail: jean.engmateriais@gmail.com, E-mail: jccalado@gmail.com [Universidade Federal do Amazonas (UFAM), Manaus (Brazil). Dept. de Engenharia de Materiais; Paskocimas, C.A.; Martinelli, A.E.; Nascimento, R.M., E-mail: paskocimas@uol.com.br, E-mail: aemart@uol.com.br, E-mail: rubensmaribondo@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais

    2017-01-15

    The aim of this study was to characterize sediment from the dredging of storm water channels (Scp) in the city of Salvador, Bahia, aiming its maximum replacement by clay in structural ceramics, since this binary mixture is part of the pilot project of the standard mass, in the research of interlocked block ceramic formulation. Initially, the sediment was submitted to the following tests: plasticity index; chemical analysis by X-ray fluorescence; mineralogical analysis by X-ray diffraction; thermal and particle size analyses. The morphology of the material was analyzed by scanning electron microscopy, coupled with energy dispersive spectroscopy. Then, sediment (Scp) was added to clay from the municipality of Candelas, Bahia, in the proportions of 10, 20, 30 and 40 wt%. Specimens were prepared by uniaxial pressing in dimensions of 60 mm x 20 mm, with compacting pressure of 25 MPa, and the material was humidified with 8% of water. Firing was conducted in resistive furnace at temperatures of 850, 950 and 1050 deg C, with 5 deg C / min heating rate. The properties evaluated were: linear shrinkage; water absorption and modulus of rupture. The results indicated the possibility of using SCP in structural ceramics by the prerequisites required in standards, in the manufacture of tiles, sealing blocks and bricks. (author)

  20. Crystallisation behavior and electronic conductivity of vanadium tellurite glass-ceramics

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Yue, Yuanzheng; Rodrigues, A.C.M.

    2012-01-01

    The electrodes of secondary batteries degrade during consecutive intercalation cycles, thus reducing the units’ capacity. The amorphous nature of an electrode could theoretically lower the degree of such degradation. Since a vanadium tellurite system exhibit high electronic conductivity and the a......The electrodes of secondary batteries degrade during consecutive intercalation cycles, thus reducing the units’ capacity. The amorphous nature of an electrode could theoretically lower the degree of such degradation. Since a vanadium tellurite system exhibit high electronic conductivity...... and the ability to intercalate lithium-ions, it is a candidate for usage as cathode material. In the present work, we optimize the electronic conductivity of the congruent 2TeO2-V2O5 composition by tuning both the redox state of the vanadium and the overall degree of crystallinity. Amorphous 2TeO2-V2O5...... temperature of synthesis, and it is measured by electron paramagnetic resonance spectroscopy. The electronic conductivity is measured by impedance spectroscopy in the temperature range from 298 to 523 K. The results indicate that the electronic conductivity is independent of the degree of crystallinity...

  1. Development of 32-channel silicon drift detectors and digital electronics for X-ray spectroscopy.

    Science.gov (United States)

    Gauthier, C; Goujon, G; Goulon, J; Moguiline, E; Dressler, P; Henck, R; Lampert, M O

    1998-05-01

    The performance of silicon-drift-detector (SDD) arrays and digital electronics designed for X-ray absorption spectroscopy in the fluorescence excitation mode is reported. Different detectors have been manufactured and tested: two single-channel SDDs with different active areas (10 mm(2) and 1 cm(2)) and a monolithic 2 cm(2) SDD with eight readout anodes. The energy resolution varies between 160 and 170 eV FWHM. A new digital multichannel shaping amplifier has been produced. Its performance is presented in comparison with that of a standard commercial shaper.

  2. Characteristics of four-channel Cherenkov-type detector for measurements of runaway electrons in the ISTTOK tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Plyusnin, V. V.; Duarte, P.; Fernandes, H.; Silva, C. [Instituto de Plasmas e FuSao Nuclear - Laboratorio Associado, Association Euratom/IST, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Jakubowski, L.; Zebrowski, J.; Malinowski, K.; Rabinski, M.; Sadowski, M. J. [The Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland)

    2010-10-15

    A diagnostics capable of characterizing the runaway and superthermal electrons has been developing on the ISTTOK tokamak. In previous paper, a use of single-channel Cherenkov-type detector with titanium filter for runaway electron studies in ISTTOK was reported. To measure fast electron populations with different energies, a prototype of a four-channel detector with molybdenum filters was designed. Test-stand studies of filters with different thicknesses (1, 3, 7, 10, 20, 50, and 100 {mu}m) have shown that they should allow the detection of electrons with energies higher than 69, 75, 87, 95, 120, 181, and 260 keV, respectively. First results of measurements with the four-channel detector revealed the possibility to measure reliably different fast electrons populations simultaneously.

  3. Measurement of the Electronic Thermal Conductance Channels and Heat Capacity of Graphene at Low Temperature

    Directory of Open Access Journals (Sweden)

    Kin Chung Fong

    2013-10-01

    Full Text Available The ability to transport energy is a fundamental property of the two-dimensional Dirac fermions in graphene. Electronic thermal transport in this system is relatively unexplored and is expected to show unique fundamental properties and to play an important role in future applications of graphene, including optoelectronics, plasmonics, and ultrasensitive bolometry. Here, we present measurements of bipolar thermal conductances due to electron diffusion and electron-phonon coupling and infer the electronic specific heat, with a minimum value of 10k_{B} (10^{-22}  J/K per square micron. We test the validity of the Wiedemann-Franz law and find that the Lorenz number equals 1.32×(π^{2}/3(k_{B}/e^{2}. The electron-phonon thermal conductance has a temperature power law T^{2} at high doping levels, and the coupling parameter is consistent with recent theory, indicating its enhancement by impurity scattering. We demonstrate control of the thermal conductance by electrical gating and by suppressing the diffusion channel using NbTiN superconducting electrodes, which sets the stage for future graphene-based single-microwave photon detection.

  4. EBSD and electron channeling study of anomalous slip in oligocrystals of high chromium ferritic stainless steel.

    Science.gov (United States)

    Hsiao, Zheng-Wen; Wu, Ting-Yi; Chen, Delphic; Kuo, Jui-Chao; Lin, Dong-Yih

    2017-03-01

    In the present study, electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) techniques were applied to investigate the deformation pattern of coarse ferrite grains after being subjected to 3%, 6%, and 10% tensile deformation. Oligocrystals of Crofer® 22H ferritic steel were obtained as experimental material at 1075°C for 22min annealing. Using kernel average misorientation (KAM) mapping obtained from EBSD, possible slip planes are (110), (101), (12-1) and (32-1) in grain A; (0-11), (-101), (-112), (1-21) in grain B; and (0-11), (1-21) and (11-2) in grain C. Combining ECCI and EBSD techniques enables us to identify two a0[11¯1]/2 edge dislocations that occur on the (110)[1-11] and (32-1)[1-11] slip systems for grain A, thereby breaking down Schmid's law. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Threading dislocation density characterization in III-V photovoltaic materials by electron channeling contrast imaging

    Science.gov (United States)

    Yaung, Kevin Nay; Kirnstoetter, Stefan; Faucher, Joseph; Gerger, Andy; Lochtefeld, Anthony; Barnett, Allen; Lee, Minjoo Larry

    2016-11-01

    Accurate and rapid threading dislocation density (TDD) characterization of III-V photovoltaic materials using electron channeling contrast imaging (ECCI) is demonstrated. TDDs measured using ECCI showed close agreement with those from electron beam-induced current mapping (EBIC) and defect selective etching (DSE). ECCI is shown to be well-suited for measuring TDD values over a range of 5×106-5×108 cm-2. ECCI can distinguish individual dislocations in clusters closer than 0.2 μm, highlighting its excellent spatial resolution compared to DSE and EBIC. Taken together, ECCI is shown to be a versatile and complementary method to rapidly quantify TDD in III-V solar cells.

  6. Monolithic Chip System with a Microfluidic Channel for In Situ Electron Microscopy of Liquids

    DEFF Research Database (Denmark)

    Jensen, Eric; Burrows, Andrew; Mølhave, Kristian

    2014-01-01

    sandwiched microchips with thin membranes. We report on a new microfabricated chip system based on a monolithic design that enables membrane geometry on the scale of a few micrometers. The design is intended to reduce membrane deflection when the system is under pressure, a micro fluidic channel for improved...... flow geometry, and a better space angle for auxiliary detectors such as energy-dispersive X-ray spectroscopy. We explain the system design and fabrication and show the first successful TEM images of liquid samples in the chips.......Electron microscopy of enclosed liquid samples requires the thinnest possible membranes as enclosing windows as well as nanoscale liquid sample thickness to achieve the best possible resolution. Today liquid sample systems for transmission electron microscopy (TEM) are typically made from two...

  7. Search For The Higgs Boson Decaying Into $\\tau$-Leptons In The Di-Electron Channel

    CERN Document Server

    Salfeld-Nebgen, Jakob; Schleper, Peter

    The first dedicated search for Higgs bosons decaying into tau pairs with two electrons and 4 neutrinos in the final state is presented. The search is performed with the CMS detector at the LHC based on an integrated luminosity of 4.9 fb$^{-1}$ and 19.7 fb$^{-1}$ at 7 TeV and 8 TeV, respectively. Events with two reconstructed electrons are selected before extensive multivariate analysis techniques are utilized to achieve an optimal background rejection. The $ee$-channel alone excludes $3.2\\times(\\sigma^H_{SM}\\times BR(H\\rightarrow \\tau\\tau))$ for $m_H = 120$ $GeV/c^2$ and $3.7\\times(\\sigma^H_{SM}\\times BR(H\\rightarrow \\tau\\tau))$ for $m_H = 125$ $GeV/c^2$ at 95\\% confidence level. The $ee$-channel is combined into the official CMS $H\\rightarrow \\tau\\tau$ analysis, to find, for the first time, direct evidence for couplings of the new Higgs-like boson to down-type fermions with 3.2$\\sigma$.

  8. Electronic Communication Channel Use and Health Information Source Preferences Among Latinos in Northern Manhattan.

    Science.gov (United States)

    Hillyer, Grace Clarke; Schmitt, Karen M; Lizardo, Maria; Reyes, Andria; Bazan, Mercedes; Alvarez, Maria C; Sandoval, Rossy; Abdul, Kazeem; Orjuela, Manuela A

    2017-04-01

    Understanding key health concepts is crucial to participation in Precision Medicine initiatives. In order to assess methods to develop and disseminate a curriculum to educate community members in Northern Manhattan about Precision Medicine, clients from a local community-based organization were interviewed during 2014-2015. Health literacy, acculturation, use of Internet, email, and text messaging, and health information sources were assessed. Associations between age and outcomes were evaluated; multivariable analysis used to examine the relationship between participant characteristics and sources of health information. Of 497 interviewed, 29.4 % had inadequate health literacy and 53.6 % had access to the Internet, 43.9 % to email, and 45.3 % to text messaging. Having adequate health literacy was associated with seeking information from a healthcare professional (OR 2.59, 95 % CI 1.54-4.35) and from the Internet (OR 3.15, 95 % CI 1.97-5.04); having ≤ grade school education (OR 2.61, 95 % CI 1.32-5.17) also preferred information from their provider; persons >45 years (OR 0.29, 95 % CI 0.18-0.47) were less likely to use the Internet for health information and preferred printed media (OR 1.64, 95 % CI 1.07-2.50). Overall, electronic communication channel use was low and varied significantly by age with those ≤45 years more likely to utilize electronic channels. Preferred sources of health information also varied by age as well as by health literacy and educational level. This study demonstrates that to effectively communicate key Precision Medicine concepts, curriculum development for Latino community members of Northern Manhattan will require attention to health literacy, language preference and acculturation and incorporate more traditional communication channels for older community members.

  9. Electron beam test of an iron/gas calorimeter based on ceramic parallel plate chambers

    Energy Technology Data Exchange (ETDEWEB)

    Arefiev, A.; Bencze, Gy.L.; Bizzeti, A.; Choumilov, E.; Civinini, C; Dalla Santa, F.; D' Alessandro, R.; Ferrando, A.; Fouz, M.C.; Herve, A.; Iglesias, A.; Ivochkin, V.; Josa, M.I.; Maggi, F.; Malinin, A.; Meschini, M.; Pojidaev, V.; Radermacher, E.; Salicio, J.M.

    1995-07-01

    The baseline option for the very forward calorimetry in the CMS experiment is an iron/gas calorimeter based on parallel plate chambers. A small prototype module of such a calorimeter, has been tested using electrons of 5 to 100 GeV/c momentum with various high voltages and two gases: CO2 (100%) and CF4/CO2 (80/20), at atmospheric pressure. The collected charge has been measured as a function of the high voltage and of the electron energy. The energy resolution has also been measured. Comparisons have been made with Monte-Carlo predictions. Agreement between data an simulation allows to make and estimation of the expected performance of a full size calorimeter. (Author) 23 refs.

  10. Cross-correlation based high resolution electron backscatter diffraction and electron channelling contrast imaging for strain mapping and dislocation distributions in InAlN thin films

    OpenAIRE

    Vilalta-Clemente, A.; Naresh-Kumar, G; Nouf-Allehiani, M.; Gamarra, P.; di Forte-Poisson, M. A.; Trager-Cowan, C.; Wilkinson, A.J.

    2017-01-01

    We describe the development of cross-correlation based high resolution electron backscatter diffraction (HR-EBSD) and electron channelling contrast imaging (ECCI), in the scanning electron microscope (SEM), to quantitatively map the strain variation and lattice rotation and determine the density and identify dislocations in nitride semiconductor thin films. These techniques can provide quantitative, rapid, non-destructive analysis of the structural properties of materials with a spatial resol...

  11. Chemical Selectivity and Sensitivity of a 16-Channel Electronic Nose for Trace Vapour Detection

    Directory of Open Access Journals (Sweden)

    Drago Strle

    2017-12-01

    Full Text Available Good chemical selectivity of sensors for detecting vapour traces of targeted molecules is vital to reliable detection systems for explosives and other harmful materials. We present the design, construction and measurements of the electronic response of a 16 channel electronic nose based on 16 differential microcapacitors, which were surface-functionalized by different silanes. The e-nose detects less than 1 molecule of TNT out of 10+12 N2 molecules in a carrier gas in 1 s. Differently silanized sensors give different responses to different molecules. Electronic responses are presented for TNT, RDX, DNT, H2S, HCN, FeS, NH3, propane, methanol, acetone, ethanol, methane, toluene and water. We consider the number density of these molecules and find that silane surfaces show extreme affinity for attracting molecules of TNT, DNT and RDX. The probability to bind these molecules and form a surface-adsorbate is typically 10+7 times larger than the probability to bind water molecules, for example. We present a matrix of responses of differently functionalized microcapacitors and we propose that chemical selectivity of multichannel e-nose could be enhanced by using artificial intelligence deep learning methods.

  12. WIMAGINE: an implantable electronic platform for wireless 64-channel ECoG recording

    Science.gov (United States)

    Foerster, M.; Porcherot, J.; Robinet, S.; D'Errico, R.; Josselin, V.; Sauter, F.; Mestais, C.; Charvet, G.

    2013-05-01

    The WIMAGINE platform was developed as a proof of concept and first functional prototype of an implantable device for recording ECoG signals on a large number of electrodes. The designed system provides the means of recording wirelessly up to 64 ECoG channels. Two ASIC CINESIC32 ensure the amplification and digitization of the neurosignals which are then transmitted to a PC using a ZL70102 transceiver in the MICS band. An MSP430 handles the communication protocol, configures the ASICs and gives access to various sensor information. The electronics are packaged hermetically in a biocompatible titanium housing encapsulated medical grade silicone. The whole device is powered remotely over an inductive link at 13.56MHz and complies with the regulations applicable to class III AIMD.

  13. Analytical, steady-state model of gain saturation in channel electron multipliers

    CERN Document Server

    Giudicotti, L

    2002-01-01

    By using the transmission line modeling (TLM) technique we derive a simple model describing the saturation of the gain in channel electron multipliers and show that it generalizes and extends a previous steady-state model due to Shikhaliev. Then by introducing a physically consistent rational approximation of the non-linear gain equation we derive an exact, steady-state, analytical solution in which, contrary to other empirical assumptions about the functional dependence of the internal voltage are not required. The model is then used to simulate a multianode microchannel plate (MCP) photomultiplier, showing that the computed gain in saturated conditions is qualitatively in agreement with published experimental data. Finally, we discuss the general validity of our model, we suggest possible measurements and comment existing data relevant for its validation.

  14. Characterization of crystallographic defects in SEM by electron channeling assisted by high resolution pseudo-Kikuchi patterns : application to IF-steel, UO2 and TiAl

    OpenAIRE

    Mansour, Haithem

    2016-01-01

    Electron Channeling Contrast Imaging (ECCI) is a Scanning Electron Microscope (SEM) technique used to observe and characterize crystallographic defects. ECCI requires the crystal to be oriented relative to the electron beam with high accuracy (0.1°) in order to control the electron channeling conditions. The SEM techniques used to determine the crystallographic orientation, such as conventional Electron BackScattered Diffraction (EBSD) or Rocking Beam, don’t satisfy the high accuracy required...

  15. Diagnosis and dynamics in a simple low energy medium current electron beam channel

    Science.gov (United States)

    Marghitu, S.; Marghitu, O.; Oproiu, C.; Marin, G.; Scarlat, Fl.

    2004-05-01

    We present a simple experimental setup and an associated method enabling both the non-destructive diagnosis and the calculation of the beam evolution in a low energy medium current electron beam channel, where the space-charge and emittance effects are comparable. The diagnosis makes use of an axially symmetric magnetic lens while a second lens is added to increase the flexibility in the beam processing. The paper emphasizes the three steps involved in the method: the evaluation of the lenses' magnetic field by numerical simulation, the beam diagnosis, and the computation of the beam envelope. The calculation of the magnetic field is based on the finite element method. Subsequently, the beam parameters at the electron source exit - emittance and cross-over radius and position - are found with the modified three gradient method. Finally, the beam dynamics are modeled with the K-V equation adapted for the particular case of axial symmetry. The results obtained in this paper can be used to optimize technological processes, such as welding, hardening, cladding, and surface alloying.

  16. An electronic channel switching-based aptasensor for ultrasensitive protein detection

    Energy Technology Data Exchange (ETDEWEB)

    Li Hongbo; Wang Cui [State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Wu Zaisheng, E-mail: wuzaisheng@163.com [State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Lu Limin; Qiu Liping; Zhou Hui; Shen Guoli [State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China); Yu Ruqin, E-mail: rqyu@hnu.edu.cn [State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082 (China)

    2013-01-03

    Highlights: Black-Right-Pointing-Pointer Target IgE is successfully designed to serve as a barrier to separate enzyme from its substrate. Black-Right-Pointing-Pointer This sensing platform of electronic channel switching-based aptasensor can be simply manipulated. Black-Right-Pointing-Pointer The stable hairpin structure of anti-IgE aptamer is utilized to detect target IgE. Black-Right-Pointing-Pointer The sensor is ultrasensitive sensitivity, excellent selectivity and small volume of sample. Black-Right-Pointing-Pointer It is a powerful platform to be further expanded to detect more kinds of proteins and even cells. - Abstract: Due to the ubiquity and essential of the proteins in all living organisms, the identification and quantification of disease-specific proteins are particularly important. Because the conformational change of aptamer upon its target or probe/target/probe sandwich often is the primary prerequisite for the design of an electrochemical aptameric assay system, it is extremely difficult to construct the electrochemical aptasensor for protein assay because the corresponding aptamers cannot often meet the requirement. To circumvent the obstacles mentioned, an electronic channel switching-based (ECS) aptasensor for ultrasensitive protein detection is developed. The essential achievement made is that an innovative sensing concept is proposed: the hairpin structure of aptamer is designed to pull electroactive species toward electrode surface and makes the surface-immobilized IgE serve as a barrier that separates enzyme from its substrate. It seemingly ensures that the ECS aptasensor exhibits most excellent assay features, such as, a detection limit of 4.44 Multiplication-Sign 10{sup -6} {mu}g mL{sup -1} (22.7 fM, 220 zmol in 10-{mu}L sample) (demonstrating a 5 orders of magnitude improvement in detection sensitivity compared with classical electronic aptasensors) and dynamic response range from 4.44 Multiplication-Sign 10{sup -6} to 4.44 Multiplication

  17. Porous ceramic membranes

    OpenAIRE

    Biesheuvel, P. M.; Biesheuvel, Pieter Maarten

    2000-01-01

    Synthetic membranes are increasingly used for energy-efficient separation of liquid and gaseous mixtures in household applications, environmental technology and the chemical and energy industry. Besides, membranes are used in component-specific sensors in gas and liquid streams, preferably combined with micro-electronic devices. Ceramic membranes have a large potential over their polymer counterparts for applications at high temperature, pressure and in aggressive environments. Ceramic membra...

  18. Net electron energy gain induced by superluminal phase velocity and subluminal group velocity of a laser in a plasma channel

    Science.gov (United States)

    Cheng, Li-Hong; Yao, Zheng-Wei; Zhang, Xiao-Bo; Xue, Ju-Kui

    2017-08-01

    We examine electron dynamics induced by laser-plasma interaction in a two-dimensional plasma channel, taking into action the laser phase velocity as well as the group velocity. The coupled effects of phase velocity, group velocity, and plasma channel on electron dynamics are discussed in detail. The superluminal phase velocity and the corresponding subluminal group velocity of the laser result in rich and complex electron dynamics, which are depicted in the plane of the phase velocity and plasma charge density. For weak superluminosity of the phase velocity, the effects of the phase velocity and the group velocity can be neglected. For moderate superluminosity of the phase velocity, a cross-over region can exist, where the highly energetic electron could be found and the net energy gain is several times greater than the energy gain in vacuum. For strong superluminosity of the phase velocity, the dephasing rate increases and thus limits the electron energy gain from the laser. However, the asymmetric laser pulse, attributed by the superluminal phase velocity and the subluminal group velocity, results in the electron getting adjustable net energy gain from the laser. The electron oscillations are no longer limited by the charge density threshold and the electron can always get net energy from the laser. These electron dynamics can also be modified by adjusting the polarization of the laser.

  19. Observation of Top Quark Pairs in the Dilepton Decay Channel using Electrons, Muons and Taus

    Energy Technology Data Exchange (ETDEWEB)

    Hohlmann, Marcus [Chicago U.

    1997-01-01

    This thesis presents a search for top quark pair production via the process p pbar -> t tbar + X -> W+W- b bbar + X -> (l+ nu_l)(l- nubar_l) b bbar + X, where l is either e, mu, or tau. Using a sample of 109+-7 pb of ppbar collisons at sqrt{s}=1.8 TeV collected by the CDF detector at the Fermilab Tevatron we find a clear signal for ttbar production in the ee, mumu, and emu dilepton channels. We observe 9 events where we expect 3.9+-0.7 ttbar events (based on the theoretical production cross section) and 2.1+-0.4 background events. The ttbar production cross section measured from this channel is sigma_{ttbar}=8.5^{+4.1}_{-3.3}(stat)^{+1.6}_{-0.8} (syst) pb. Using a method developed in this thesis to identify hadronically decaying tau leptons we also search for etau and mutau dilepton events from t tbar production and decay. We observe 4 events and expect 2.5+-0.4 background events. In 3 of the 4 events atleast one jet is tagged as due to a b quark decay. We expect 0.28+-0.02 tagged events from background processes. Based on the 4 tau dilepton events we calculate the ttbar production cross section to be sigma_{t tbar } = 10.2^{+16.3}_{-10.2}(stat)+-1.6(syst) pb. The kinematics and topology of the candidate events are generally consistent with the expectations, with two exceptions. Five of the 14 candidate events have unusually large missing transverse energy. One emu event contains an electron with very high Et (182 GeV) and an additional high--Et (23 GeV) isolated positron. In 109 pb we expect (2.4+-0.9)x10^{-6} such ``trilepton" events from t tbar production and decay. Enjoy,Marcus

  20. Ceramic matrix composite article and process of fabricating a ceramic matrix composite article

    Science.gov (United States)

    Cairo, Ronald Robert; DiMascio, Paul Stephen; Parolini, Jason Robert

    2016-01-12

    A ceramic matrix composite article and a process of fabricating a ceramic matrix composite are disclosed. The ceramic matrix composite article includes a matrix distribution pattern formed by a manifold and ceramic matrix composite plies laid up on the matrix distribution pattern, includes the manifold, or a combination thereof. The manifold includes one or more matrix distribution channels operably connected to a delivery interface, the delivery interface configured for providing matrix material to one or more of the ceramic matrix composite plies. The process includes providing the manifold, forming the matrix distribution pattern by transporting the matrix material through the manifold, and contacting the ceramic matrix composite plies with the matrix material.

  1. Transformational Electronics: Towards Flexible Low-Cost High Mobility Channel Materials

    KAUST Repository

    Nassar, Joanna M.

    2014-05-01

    For the last four decades, Si CMOS technology has been advancing with Moore’s law prediction, working itself down to the sub-20 nm regime. However, fundamental problems and limitations arise with the down-scaling of transistors and thus new innovations needed to be discovered in order to further improve device performance without compromising power consumption and size. Thus, a lot of studies have focused on the development of new CMOS compatible architectures as well as the discovery of new high mobility channel materials that will allow further miniaturization of CMOS transistors and improvement of device performance. Pushing the limits even further, flexible and foldable electronics seem to be the new attractive topic. By being able to make our devices flexible through a CMOS compatible process, one will be able to integrate hundreds of billions of more transistors in a small volumetric space, allowing to increase the performance and speed of our electronics all together with making things thinner, lighter, smaller and even interactive with the human skin. Thus, in this thesis, we introduce for the first time a cost-effective CMOS compatible approach to make high-k/metal gate devices on flexible Germanium (Ge) and Silicon-Germanium (SiGe) platforms. In the first part, we will look at the various approaches in the literature that has been developed to get flexible platforms, as well as we will give a brief overview about epitaxial growth of Si1-xGex films. We will also examine the electrical properties of the Si1-xGex alloys up to Ge (x=1) and discuss how strain affects the band structure diagram, and thus the mobility of the material. We will also review the material growth properties as well as the state-of-the-art results on high mobility metal-oxide semiconductor capacitors (MOSCAPs) using strained SiGe films. Then, we will introduce the flexible process that we have developed, based on a cost-effective “trench-protect-release-reuse” approach, utilizing

  2. An in vivo Study on Bacterial Colonization with Metal, Ceramic and Self-ligating Brackets: A Scanning Electron Microscopy Study

    Directory of Open Access Journals (Sweden)

    Aravind S Raju

    2013-01-01

    Conclusion: This study highlights that higher retention of plaque in ceramic brackets ligated with elastomeric ring followed with metal brackets ligated with steel ligatures and comparatively less plaque retention in self-ligating brackets. Excess composite around the bracket base is the critical site of plaque accumulation associated with fixed appliances due to its rough surface texture.

  3. Study of unexplained hard photon production by electrons channelled in a crystal

    CERN Multimedia

    2002-01-01

    Our preceding experiment (NA33) designed to study the pair creation process in the interaction of high energy $\\gamma$ with a crystal in alignment conditions had revealed the existence of an unexpected peak in the radiation of 150 GeV e$^{-}$ beam for E$_{\\gamma}$/E$_{e^{-}} \\simeq$ 0.85 incident along the axis of a 185 $\\mu$m. Ge crystal and the photon multiplicity for the peak events has been measured to be M $\\simeq$ 5.7.\\\\ In NA42, in a 76 $\\mu$m crystal of the same crystallographic quality, the peak nearly disappears, and the photon multiplicity at x = 0.85 is only M $\\simeq$ 2.0. \\\\ The thickness dependence of the effect shows that the extrapolated multiplicity in the peak in a very thin crystal tends to unity. The high energy radiation peak emitted by axially channeled electrons in a thick crystal is then interpreted by the radiation cooling mechanism. \\\\ The extrapolation to zero thickness of these results will allow us to extract from the data the single $\\gamma$ radiation spectrum. The comparison o...

  4. A low noise front end electronics for micro-channel plate detector with wedge and strip anode

    Science.gov (United States)

    Hu, K.; Li, F.; Liang, F.; Chen, L.; Jin, G.

    2016-03-01

    A low noise Front End Electronics (FEE) for two-dimensional position sensitive Micro-Channel Plate (MCP) detector has been developed. The MCP detector is based on Wedge and Strip Anode (WSA) with induction readout mode. The WSA has three electrodes, the wedge electrode, the strip electrode, and the zigzag electrode. Then, three readout channels are designed in the Printed Circuit Board (PCB). The FEE is calibrated by a pulse generator from Agilent. We also give an analysis of the charge loss from the CSA. The noise levels of the three channels are less than 1 fC RMS at the shaping time of 200 ns. The experimental result shows that the position resolution of the MCP detector coupled with the designed PCB can reach up to 110 μm.

  5. Enhancement-Mode AIGaN/GaN High Electron Mobility Transistors Using a Nano-Channel Arrayy Structure

    Institute of Scientific and Technical Information of China (English)

    LIU Sheng-Hou; Cheng P. Wen; QIN Hua; ZHANG Bao-Shun; CAI Yong; GONG Ru-Min; WANG Jin-Yan; ZENG Chun-Hong; SHI Wen-Hua; FENG Zhi-Hong; WANG Jing-Jing; YIN Jia-Yun

    2011-01-01

    A nano-channel array (NCA) structure is applied to realize enhancement-mode (E-mode) A1GaN/GaN high electron mobility transistors (HEMTs). The fabricated NCA-HEMT,consisting of 1000 channels connected in parallel with a channel width of 64 nm,shows a threshold voltage of 0.15 V and a subthreshold slope of 78mY/dec,compared to -3.92 V and 99mV/dec for a conventional HEMT (C-HEMT),respectively.Both the NCA-HEMT and C-HEMT show similar gate leakage current,indicating no significant degradation in gate leakage characteristics for the NCA-HEMT.The surrounding-field effect and relieved polarization contribute to the very large positive threshold voltage shift,while the work function difference makes it positive.

  6. Fabrication of high-power piezoelectric transformers using lead-free ceramics for application in electronic ballasts.

    Science.gov (United States)

    Yang, Song-Ling; Chen, Shih-Ming; Tsai, Cheng-Che; Hong, Cheng-Shong; Chu, Sheng-Yuan

    2013-02-01

    CuO is doped into (Na(0.5)K(0.5))NbO(3) (NKN) ceramics to improve the piezoelectric properties and thus obtain a piezoelectric transformer (PT) with high output power. In X-ray diffraction patterns, the diffraction angles of the CuO-doped NKN ceramics shift to lower values because of an expansion of the lattice volume, thus inducing oxygen vacancies and enhancing the mechanical quality factor. A homogeneous microstructure is obtained when NKN is subjected to CuO doping, leading to improved electrical properties. PTs with different electrode areas are fabricated using the CuO-doped NKN ceramics. Considering the efficiency, voltage gain, and temperature rise of PTs at a load resistance of 1 kΩ, PTs with an electrode with an inner diameter of 15 mm are combined with the circuit design for driving a 13-W T5 fluorescent lamp. A temperature rise of 6°C and a total efficiency of 82.4% (PT and circuit) are obtained using the present PTs.

  7. Multichannel marketing: an experiment on guiding citizens to the electronic channels

    NARCIS (Netherlands)

    Teerling, Marije L.; Pieterson, Willem Jan

    2010-01-01

    Governments have a variety of channels at their disposal to help them interact with their citizens. Having realized that citizens still prefer the traditional channels, governments are now focusing on ways to lead them to the web. Previously, we have shown that citizens prefer the use of soft

  8. Electron gas polarization effect induced by heavy H-like ions of moderate velocities channeled in a silicon crystal

    Energy Technology Data Exchange (ETDEWEB)

    Testa, E. [Institut de Physique Nucleaire de Lyon, CNRS-IN2P3, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne (France); Dauvergne, D. [Institut de Physique Nucleaire de Lyon, CNRS-IN2P3, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne (France)]. E-mail: d.dauvergne@ipnl.in2p3.fr; Braeuning-Demian, A. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany); Bosch, F. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany); Braeuning, H. [Institut fuer Kernphysik, Justus Liebig Universitaet, D-35392 Giessen (Germany); Chevallier, M. [Institut de Physique Nucleaire de Lyon, CNRS-IN2P3, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne (France); Cohen, C. [Institut des Nano-Sciences de Paris, CNRS-UMR75-88, Universites Paris VI et Paris VII, 75251 Paris cedex 05 (France); Gumberidze, A. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany); Hagmann, S. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany); L' Hoir, A. [Institut des Nano-Sciences de Paris, CNRS-UMR75-88, Universites Paris VI et Paris VII, 75251 Paris cedex 05 (France); Kirsch, R. [Institut de Physique Nucleaire de Lyon, CNRS-IN2P3, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne (France); Kozhuharov, C.; Liesen, D.; Mokler, P.H. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany); Poizat, J.-C.; Ray, C. [Institut de Physique Nucleaire de Lyon, CNRS-IN2P3, Universite Claude Bernard Lyon 1, F-69622 Villeurbanne (France); Rozet, J.-P. [Institut des Nano-Sciences de Paris, CNRS-UMR75-88, Universites Paris VI et Paris VII, 75251 Paris cedex 05 (France); Stoehlker, Th.; Toleikis, S. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany); Toulemonde, M. [Centre Interdisciplinaire de Recherche Ions-Lasers, UMR 11, CEA-CNRS, 14040 Caen cedex (France); Verma, P. [Gesellschaft fuer Schwerionen Forschung (GSI), D-64291 Darmstadt (Germany)

    2006-04-15

    We report on the observation of a strong perturbation of the electron gas induced by 20 MeV/u U{sup 91+} ions and 13 MeV/u Pb{sup 81+} ions channeled in silicon crystals. This collective response (wake effect) induces a shift of the continuum energy level by more than 100 eV, which is observed by means of radiative electron capture into the K- and L-shells of the projectiles. We also observe an increase of the REC probability by 20-50% relative to the probability in a non-perturbed electron gas. The energy shift is in agreement with calculations using the linear response theory, whereas the local electron density enhancement is much smaller than predicted by the same model. This shows that, for the small values of the adiabaticity parameter achieved in our experiments, the density fluctuations are not strongly localized in the vicinity of the heavy ions.

  9. Channel height and curvature effects on flow boiling from an electronic chip

    Science.gov (United States)

    Leland, J. E.; Chow, L. C.

    1995-04-01

    Forced convective boiling from a discrete heat source in a curved rectangular channel has been experimentally investigated. The flow area height and radius of curvature of the channel were varied to ascertain the effects of induced buoyancy and secondary flow. For comparison, results were also obtained for a similar heat source in a straight channel. Three configurations encompassing two radii of curvature, 28.6 and 56.4 mm, and three heights, 3.18, 5.56, and 6.35 mm, were studied. An additional channel height of 1.14 mm was investigated for the straight geometry only. Data were obtained for subcoolings of 5, 20, and 35 C and flow velocities of 1-7 m/s. For the straight geometry, critical heat flux (CHF) did not vary much for heights greater than 1.14 mm. The percent increase in curved channel CHF over straight channel CHF was highest for 5 C subcooling. This implies that buoyancy effects are most important when there is significant vapor generation. For a given subcooling and velocity, the radius of curvature had little effect. This implies that secondary flow has little effect under these conditions. A correlation is developed that describes the effects of buoyancy and secondary flow on CHF in the curved channel.

  10. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  11. Development of Ceramic Laser Element

    Science.gov (United States)

    2009-11-24

    macro level (OM) . . . P.7 6. Observation in micro level (SEM, EPMA ) . . . P.9 7. Observation in nano-level (HR-TEM...Transmitted polarized microscopy of the transparent ceramic samples. 10 6.2 By SEM and EPMA (electron probe micro analysis) In order to...Gd:YAG Y Al Nd1%Nd:YAG Fig.11 Electron probe micro analysis ( EPMA ) images of the fabricated transparent ceramic samples. 11 7

  12. Characterization of Amorphous Oxide Nano-Thick Layers on 316L Stainless Steel by Electron Channeling Contrast Imaging and Electron Backscatter Diffraction.

    Science.gov (United States)

    Dorri, Mahrokh; Turgeon, Stéphane; Brodusch, Nicolas; Cloutier, Maxime; Chevallier, Pascale; Gauvin, Raynald; Mantovani, Diego

    2016-10-01

    Characterization of the topmost surface of biomaterials is crucial to understanding their properties and interactions with the local environment. In this study, the oxide layer microstructure of plasma-modified 316L stainless steel (SS316L) samples was analyzed by a combination of electron backscatter diffraction and electron channeling contrast imaging using low-energy incident electrons. Both techniques allowed clear identification of a nano-thick amorphous oxide layer, on top of the polycrystalline substrate, for the plasma-modified samples. A methodology was developed using Monte Carlo simulations combined with the experimental results to estimate thickness of the amorphous layer for different surface conditions. X-ray photoelectron spectroscopy depth profiles were used to validate these estimations.

  13. Study of electron beams within ISTTOK tokamak by means of a multi-channel Cherenkov detector; their correlation with hard X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Jakubowski, L., E-mail: Lech.Jakubowski@ipj.gov.p [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Malinowski, K.; Sadowski, M.J.; Zebrowski, J. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Plyusnin, V.V. [Association Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Rabinski, M. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Fernandes, H.; Silva, C.; Duarte, P. [Association Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Jakubowski, M.J. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland)

    2010-11-11

    The paper describes experimental studies of electron beams emitted from a plasma torus within the ISTTOK tokamak, which were performed by means of a new four-channel detector of the Cherenkov type. A range of electron energy was estimated. There were also measured hard X-rays, and their correlation with the fast run-away electron beams was investigated experimentally.

  14. Photoionisation detection of single {sup 87}Rb-atoms using channel electron multipliers

    Energy Technology Data Exchange (ETDEWEB)

    Henkel, Florian Alexander

    2011-09-02

    Fast and efficient detection of single atoms is a universal requirement concerning modern experiments in atom physics, quantum optics, and precision spectroscopy. In particular for future quantum information and quantum communication technologies, the efficient readout of qubit states encoded in single atoms or ions is an elementary prerequisite. The rapid development in the field of quantum optics and atom optics in the recent years has enabled to prepare individual atoms as quantum memories or arrays of single atoms as qubit registers. With such systems, the implementation of quantum computation or quantum communication protocols seems feasible. This thesis describes a novel detection scheme which enables fast and efficient state analysis of single neutral atoms. The detection scheme is based on photoionisation and consists of two parts: the hyperfine-state selective photoionisation of single atoms and the registration of the generated photoion-electron pairs via two channel electron multipliers (CEMs). In this work, both parts were investigated in two separate experiments. For the first step, a photoionisation probability of p{sub ion}=0.991 within an ionisation time of t{sub ion}=386 ns is achieved for a single {sup 87}Rb-atom in an optical dipole trap. For the second part, a compact detection system for the ionisation fragments was developed consisting of two opposing CEM detectors. Measurements show that single neutral atoms can be detected via their ionisation fragments with a detection efficiency of {eta}{sub atom}=0.991 within a detection time of t{sub det}=415.5 ns. In a future combined setup, this will allow the state-selective readout of optically trapped, single neutral {sup 87}Rb-atoms via photoionisation detection with an estimated detection efficiency {eta}=0.982 and a detection time of t{sub tot} = 802 ns. Although initially developed for single {sup 87}Rb-atoms, the concept of photoionisation detection is in principle generally applicable to any

  15. Electron Channeling Contrast Imaging (ECCI) and Electron Backscatter Diffraction (EBSD) Study of Forsterite Olivine Deformed in the D-DIA Apparatus

    Science.gov (United States)

    Kaboli, S.; Burnley, P. C.

    2016-12-01

    Understanding the rheology of Earth's interior requires a detailed study of microstructure and crystallographic texture on a micro- and nanoscale. Quantitative microstructure characterization of geological materials is commonly performed on thin foils using a transmission electron microscope (TEM). The main drawbacks of TEM include time consuming and destructive thin foil preparation, limited field of view and statistically unreliable results in the case of heterogeneous microstructures which are common in geological materials. Electron channeling contrast imaging (ECCI) is a complementary technique to electron backscatter diffraction (EBSD) for quantitative microstructure characterization of bulk samples in a field emission scanning electron microscope (FE-SEM). The main application of ECCI is in characterization of deformed materials since it allows the warping of the lattice to be imaged based on the electron channeling contrast. In comparison to TEM, the main advantages of using ECCI in SEM include non-destructive bulk sample preparation and statistically reliable results from a large field of view. In this study, in-situ synchrotron x-ray diffraction deformation experiments were conducted on forsterite olivine at a variety of pressures (2-7 GPa) in the D-DIA apparatus. A suitable sample preparation procedure was established using vibratory polishing in conjunction with chemical etching prior to performing ECCI in SEM. ECCI was performed at 5 keV electron beam energy and 8 mm working distance in a JEOL JSM-6700 FE-SEM. The work hardening of forsterite olivine original grains, recrystallization and grain growth were classified based on electron channeling contrast observations in each sample. EBSD crystal orientation mapping was performed on regions of interest to quantify crystallographic texture and identify various microstructure substructures for each experiment. In addition, ECCI and EBSD were performed on the alumina piston in order to examine spatial

  16. [Ceramic posts].

    Science.gov (United States)

    Mainjot, Amélie; Legros, Caroline; Vanheusden, Alain

    2006-01-01

    As a result of ceramics and all-ceram technologies development esthetic inlay core and abutments flooded the market. Their tooth-colored appearance enhances restoration biomimetism principally on the marginal gingiva area. This article reviews indications and types of cores designed for natural teeth and implants.

  17. Analysis of dislocation configurations in a [0 0 1] fcc single crystal by electron channeling contrast imaging in the SEM.

    Science.gov (United States)

    Gutierrez-Urrutia, Ivan

    2017-04-01

    We have investigated the dislocation configurations in a [0 0 1] single crystal of a face-centered alloy (316L stainless steel) by the electron channeling contrast imaging (ECCI) technique in the scanning electron microscope under controlled diffraction conditions. Specific dislocations such as piled-up dislocations and Lomer-Cottrell dislocations were characterized by the analysis of dislocation contrast and dislocation line trace analysis. The ECCI technique also allows the sound estimation of the local resolved stress acting on gliding dislocations by the analysis of the radius of curvature following a transmission electron microscopy-based geometrical approach. © 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.

  18. Channeling, volume reflection, and volume capture study of electrons in a bent silicon crystal

    Directory of Open Access Journals (Sweden)

    T. N. Wistisen

    2016-07-01

    Full Text Available We present the experimental data and analysis of experiments conducted at SLAC National Accelerator Laboratory investigating the processes of channeling, volume-reflection and volume-capture along the (111 plane in a strongly bent quasimosaic silicon crystal. These phenomena were investigated at 5 energies: 3.35, 4.2, 6.3, 10.5, and 14.0 GeV with a crystal with bending radius of 0.15 m, corresponding to curvatures of 0.053, 0.066, 0.099, 0.16, and 0.22 times the critical curvature, respectively. Based on the parameters of fitting functions we have extracted important parameters describing the channeling process such as the dechanneling length, the angle of volume reflection, the surface transmission, and the widths of the distribution of channeled particles parallel and orthogonal to the plane.

  19. Channeling and coherent bremsstrahlung effects for relativistic positrons and electrons. [16 to 28 MeV, orientation

    Energy Technology Data Exchange (ETDEWEB)

    Walker, R. L.

    1976-03-22

    Channeling of positrons in single crystals of silicon was observed in transmission and scattering measurements for incident energies from 16 to 28 MeV. In addition, the spectral dependence upon crystal orientation of the forward coherent bremsstrahlung produced by beams of 28-MeV positrons and electrons incident upon a 5 ..mu..m thick single crystal of silicon was measured with a NaI photon spectrometer. Effects of channeling and perhaps of the nonvalidity of the first Born approximation were observed for beam directions near the (111) axis of the crystal, and coherent peaks near 0.5 MeV were observed for a compound interference direction, in agreement with first-order theoretical calculations. 32 fig.

  20. Intensity distributions of reflected surface channeling protons scattered on surfaces of electron-bombarded alkali halide crystals

    Science.gov (United States)

    Fukazawa, Y.; Kihara, K.; Iwamoto, K.; Susuki, Y.

    2013-11-01

    We have examined the surface-channeling of 550 keV protons on electron-bombarded KBr(0 0 1) surfaces at grazing incidence. On the surface, electron-stimulated desorption (ESD) resulting from the irradiation of 5 keV electrons changes the surface morphology. In order to investigate the change of the surface morphology, the luminous intensity distributions observed on a fluorescent screen (scattering patterns) of the reflected protons under the surface-channeling conditions are measured. Normalized specular intensity of the protons oscillates, and the results of computer simulations show that the period of the intensity oscillation agrees with the period of layer-by-layer desorption. The measured period of the oscillation is comparable to the simulated one, i.e., the period of the desorption, however, the measured amplitude of the oscillation is weak. This shows that the layer-by-layer desorption of the experimental surface is observed but is not as remarkable as that of the perfect surface introduced in the simulation.

  1. Intensity distributions of reflected surface channeling protons scattered on surfaces of electron-bombarded alkali halide crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fukazawa, Y., E-mail: yukofu@cc.osaka-kyoiku.ac.jp; Kihara, K.; Iwamoto, K.; Susuki, Y.

    2013-11-15

    We have examined the surface-channeling of 550 keV protons on electron-bombarded KBr(0 0 1) surfaces at grazing incidence. On the surface, electron-stimulated desorption (ESD) resulting from the irradiation of 5 keV electrons changes the surface morphology. In order to investigate the change of the surface morphology, the luminous intensity distributions observed on a fluorescent screen (scattering patterns) of the reflected protons under the surface-channeling conditions are measured. Normalized specular intensity of the protons oscillates, and the results of computer simulations show that the period of the intensity oscillation agrees with the period of layer-by-layer desorption. The measured period of the oscillation is comparable to the simulated one, i.e., the period of the desorption, however, the measured amplitude of the oscillation is weak. This shows that the layer-by-layer desorption of the experimental surface is observed but is not as remarkable as that of the perfect surface introduced in the simulation.

  2. Lack of a peroxiredoxin suppresses the lethality of cells devoid of electron donors by channelling electrons to oxidized ribonucleotide reductase.

    Science.gov (United States)

    Boronat, Susanna; Domènech, Alba; Carmona, Mercè; García-Santamarina, Sarela; Bañó, M Carmen; Ayté, José; Hidalgo, Elena

    2017-06-01

    The thioredoxin and glutaredoxin pathways are responsible of recycling several enzymes which undergo intramolecular disulfide bond formation as part of their catalytic cycles such as the peroxide scavengers peroxiredoxins or the enzyme ribonucleotide reductase (RNR). RNR, the rate-limiting enzyme of deoxyribonucleotide synthesis, is an essential enzyme relying on these electron flow cascades for recycling. RNR is tightly regulated in a cell cycle-dependent manner at different levels, but little is known about the participation of electron donors in such regulation. Here, we show that cytosolic thioredoxins Trx1 and Trx3 are the primary electron donors for RNR in fission yeast. Unexpectedly, trx1 transcript and Trx1 protein levels are up-regulated in a G1-to-S phase-dependent manner, indicating that the supply of electron donors is also cell cycle-regulated. Indeed, genetic depletion of thioredoxins triggers a DNA replication checkpoint ruled by Rad3 and Cds1, with the final goal of up-regulating transcription of S phase genes and constitutive RNR synthesis. Regarding the thioredoxin and glutaredoxin cascades, one combination of gene deletions is synthetic lethal in fission yeast: cells lacking both thioredoxin reductase and cytosolic dithiol glutaredoxin. We have isolated a suppressor of this lethal phenotype: a mutation at the Tpx1-coding gene, leading to a frame shift and a loss-of-function of Tpx1, the main client of electron donors. We propose that in a mutant strain compromised in reducing equivalents, the absence of an abundant and competitive substrate such as the peroxiredoxin Tpx1 has been selected as a lethality suppressor to favor RNR function at the expense of the non-essential peroxide scavenging function, to allow DNA synthesis and cell growth.

  3. Lack of a peroxiredoxin suppresses the lethality of cells devoid of electron donors by channelling electrons to oxidized ribonucleotide reductase.

    Directory of Open Access Journals (Sweden)

    Susanna Boronat

    2017-06-01

    Full Text Available The thioredoxin and glutaredoxin pathways are responsible of recycling several enzymes which undergo intramolecular disulfide bond formation as part of their catalytic cycles such as the peroxide scavengers peroxiredoxins or the enzyme ribonucleotide reductase (RNR. RNR, the rate-limiting enzyme of deoxyribonucleotide synthesis, is an essential enzyme relying on these electron flow cascades for recycling. RNR is tightly regulated in a cell cycle-dependent manner at different levels, but little is known about the participation of electron donors in such regulation. Here, we show that cytosolic thioredoxins Trx1 and Trx3 are the primary electron donors for RNR in fission yeast. Unexpectedly, trx1 transcript and Trx1 protein levels are up-regulated in a G1-to-S phase-dependent manner, indicating that the supply of electron donors is also cell cycle-regulated. Indeed, genetic depletion of thioredoxins triggers a DNA replication checkpoint ruled by Rad3 and Cds1, with the final goal of up-regulating transcription of S phase genes and constitutive RNR synthesis. Regarding the thioredoxin and glutaredoxin cascades, one combination of gene deletions is synthetic lethal in fission yeast: cells lacking both thioredoxin reductase and cytosolic dithiol glutaredoxin. We have isolated a suppressor of this lethal phenotype: a mutation at the Tpx1-coding gene, leading to a frame shift and a loss-of-function of Tpx1, the main client of electron donors. We propose that in a mutant strain compromised in reducing equivalents, the absence of an abundant and competitive substrate such as the peroxiredoxin Tpx1 has been selected as a lethality suppressor to favor RNR function at the expense of the non-essential peroxide scavenging function, to allow DNA synthesis and cell growth.

  4. Higher-order Z/sub 1/ effects and effects of screening by bound K electrons on the electronic stopping of channeled ions

    Energy Technology Data Exchange (ETDEWEB)

    Datz, S.; Gomez del Campo, J.; Dittner, P.F.; Miller, P.D.; Biggerstaff, J.A.

    1977-05-16

    The stopping power in )111) Au for channeling ions which have not changed charge has been measured for bare nuclei for Z = 1 - 5 at 3.5 MeV/amu, and for ions bearing 0, 1, and 2 bound electrons for Z/sub 1/ = 1 - 9 at 2 MeV/amu. An effective screening of approx.0.9e per electron is obtained. For the bare nculei, deviations from simple Z/sub 1/ /sup 2/ scaling are reported. At 2 MeV/amu an increase of 3.5% in S/Z/sub 1/ /sup 2/ is seen from H to He, 3% from He to Li; but no differences are seen from Z/sub 1/ = 5 - 9. However, at 3.5-MeV/amu deviations of as much as 20% per Z/sub 1/ are observed.

  5. Resonant absorption of electromagnetic radiation in a quantum channel due to the scattering of electrons by impurities

    Science.gov (United States)

    Karpunin, V. V.; Margulis, V. A.

    2017-06-01

    We have found an analytical expression for the absorption coefficient of electromagnetic radiation in a quantum channel with a parabolic confinement potential. The calculation has been performed using the second-order perturbation theory taking into account the scattering of a quasi-one-dimensional electron gas by ionized impurities. We have analyzed the dependences of the absorption coefficient on the frequency of the electromagnetic radiation and the magnetic field. The appearance of additional resonant peaks, which are caused by scattering by impurities, has been found.

  6. Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation

    Science.gov (United States)

    Ferré, A.; Boguslavskiy, A. E.; Dagan, M.; Blanchet, V.; Bruner, B. D.; Burgy, F.; Camper, A.; Descamps, D.; Fabre, B.; Fedorov, N.; Gaudin, J.; Geoffroy, G.; Mikosch, J.; Patchkovskii, S.; Petit, S.; Ruchon, T.; Soifer, H.; Staedter, D.; Wilkinson, I.; Stolow, A.; Dudovich, N.; Mairesse, Y.

    2015-01-01

    High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20–26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected. PMID:25608712

  7. Dynamics of the microstructure of current channels and the generation of high-energy electrons in nanosecond discharges in air

    Energy Technology Data Exchange (ETDEWEB)

    Karelin, V. I.; Trenkin, A. A., E-mail: trenkin@ntc.vniief.ru; Fedoseev, I. G. [Russian Federal Nuclear Center VNIIEF (Russian Federation)

    2015-12-15

    The results of the three-dimensional numerical simulation of the dynamics of the microstructure of high-voltage nanosecond discharges in air at atmospheric pressure are presented. It is established that the fast (at a time of ≈10 ns) broadening and significant decrease in the gas concentration in the microchannels occur as a result of the ohmic heating of microchannels with the diameter of 1–30 μm. It was shown that the broadening of microchannels in a nanosecond diffusive discharge provides an increase in the ratio of the electric field strength to the gas concentration in microchannels to values sufficient for the generation highenergy electron beams and X-ray bremsstrahlung in them. Features of the dynamics of the system of microchannels and its effect on the efficiency of the generation of high-energy electrons in discharges developing in the microstructuring regime of the current channels are considered.

  8. Channel-resolved subcycle interferences of electron wave packets emitted from H$_2$ in two-color laser fields

    CERN Document Server

    Xie, Xinhua; Kartashov, Daniil; Zhang, Li; Baltuška, Andrius; Kitzler, Markus

    2016-01-01

    We report on the observation of subcycle interferences of electron wave packets released during the strong field ionization of H$_2$ with cycle-shaped two-color laser fields. With a reaction microscope, channel-resolved photoelectron momentum distribution are obtained for different final products originating from single ionization of H$_2$. Our results show that the subcycle interference structures of electron wave packet are very sensitive to the cycle-shape of the two-color laser field. The reason is that the ionization time within an optical cycle is determined by the cycle-shape of the laser field. The subcycle interference structures can be further used to get the subcycle dynamics of molecules during strong field interaction.

  9. Boiling heat transfer in narrow channels with offset strip fins: Application to electronic chipsets cooling

    OpenAIRE

    Pulvirenti, B.; Matalone, A.; Barucca, U.

    2010-01-01

    Abstract An experimental study on saturated flow boiling heat transfer of HFE-7100 in vertical rectangular channels with offset strip fins is presented. The experiments have been carried out at atmospheric pressure, over a wide range of vapour quality and heat fluxes up to 1.8?105 W/m2. The local boiling heat transfer coefficient has been obtained from experiments and analysed by means of Chen superposition method. Some correlations for convective boiling and nucleate boiling heat ...

  10. Subnanometer-resolution electron cryomicroscopy-based domain models for the cytoplasmic region of skeletal muscle RyR channel.

    Science.gov (United States)

    Serysheva, Irina I; Ludtke, Steven J; Baker, Matthew L; Cong, Yao; Topf, Maya; Eramian, David; Sali, Andrej; Hamilton, Susan L; Chiu, Wah

    2008-07-15

    The skeletal muscle Ca(2+) release channel (RyR1), a homotetramer, regulates the release of Ca(2+) from the sarcoplasmic reticulum to initiate muscle contraction. In this work, we have delineated the RyR1 monomer boundaries in a subnanometer-resolution electron cryomicroscopy (cryo-EM) density map. In the cytoplasmic region of each RyR1 monomer, 36 alpha-helices and 7 beta-sheets can be resolved. A beta-sheet was also identified close to the membrane-spanning region that resembles the cytoplasmic pore structures of inward rectifier K(+) channels. Three structural folds, generated for amino acids 12-565 using comparative modeling and cryo-EM density fitting, localize close to regions implicated in communication with the voltage sensor in the transverse tubules. Eleven of the 15 disease-related residues for these domains are mapped to the surface of these models. Four disease-related residues are found in a basin at the interfaces of these regions, creating a pocket in which the immunophilin FKBP12 can fit. Taken together, these results provide a structural context for both channel gating and the consequences of certain malignant hyperthermia and central core disease-associated mutations in RyR1.

  11. Engineering ceramics

    CERN Document Server

    Bengisu, Murat

    2001-01-01

    This is a comprehensive book applying especially to junior and senior engineering students pursuing Materials Science/ Engineering, Ceramic Engineering and Mechanical Engineering degrees. It is also a reference book for other disciplines such as Chemical Engineering, Biomedical Engineering, Nuclear Engineering and Environmental Engineering. Important properties of most engineering ceramics are given in detailed tables. Many current and possible applications of engineering ceramics are described, which can be used as a guide for materials selection and for potential future research. While covering all relevant information regarding raw materials, processing properties, characterization and applications of engineering ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  12. Contributions to a first measurement of the W-boson mass in the electron channel with the ATLAS detector

    CERN Document Server

    AUTHOR|(SzGeCERN)736721

    In this document, I present my contributions to a first measurement of the W-mass in the LHC using 4.7 fb−1 of 7 TeV data, taken in 2011. I focus on the electron decay channel, W → eν. In the first part, I discuss a study regarding the performance of the electromagnetic calorimeter of the ATLAS detector, presenting a novel method to correct the lateral profiles of electron energy deposit, along with various studies of the different Geant4 physics lists versions. In the second part, I introduce the global methodology for the W-mass measurement used in ATLAS, and discuss my contributions in details. I show in a first step the assessment of uncertainties coming from the parton shower modeling in Pythia8, and the optimization of the lepton's transverse momentum fitting range in order to reduce the systematic uncertainty. In a second step, I present an elaborate data-driven method for the estimation of the multijet background in the W → eν channel, as well as the corresponding results in terms of event yie...

  13. Laser Micromachining of Ceramics

    OpenAIRE

    SCITI, Diletta; Bellosi, Alida

    2011-01-01

    Laser surface processing of ceramics is an area of considerable technological importance for several structural, tribological, optical and electronic applications. The laser beam behaves as a heat source that induces a temperature rise on the surface and within the bulk of the material. Depending on laser parameters and material characteristics, lasers can be used for fabricating microholes at designated locations, for cutting, scribing, for surface modifications In this work different types ...

  14. Electronic and surface properties of Ga-doped In{sub 2}O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Regoutz, A., E-mail: a.regoutz@imperial.ac.uk [Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Egdell, R.G. [Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR (United Kingdom); Morgan, D.J. [Cardiff Catalysis Institute (CCI), School of Chemistry, Cardiff University, Park Place, Cardiff, CF10 3AT (United Kingdom); Palgrave, R.G. [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Téllez, H.; Skinner, S.J.; Payne, D.J. [Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Watson, G.W. [School of Chemistry and CRANN, Trinity College Dublin, Dublin 2 (Ireland); Scanlon, D.O. [University College London, Kathleen Lonsdale Materials Chemistry, Department of Chemistry, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom)

    2015-09-15

    Graphical abstract: - Highlights: • The solubility limit of Ga in In{sub 2}O{sub 3} was established to be around 6%. • Ga doping causes a reduction in band gap although the band gap of Ga{sub 2}O{sub 3} is larger than that of In{sub 2}O{sub 3}. • The reduction in band gap is attributed to the role of lone pairs at surfaces and grain boundaries. • A pronounced surface segregation of Ga is observed. - Abstract: The limit of solubility of Ga{sub 2}O{sub 3} in the cubic bixbyite In{sub 2}O{sub 3} phase was established by X-ray diffraction and Raman spectroscopy to correspond to replacement of around 6% of In cations by Ga for samples prepared at 1250 °C. Density functional theory calculations suggest that Ga substitution should lead to widening of the bulk bandgap, as expected from the much larger gap of Ga{sub 2}O{sub 3} as compared to In{sub 2}O{sub 3}. However both diffuse reflectance spectroscopy and valence band X-ray photoemission reveal an apparent narrowing of the gap with Ga doping. It is tentatively concluded that this anomaly arises from introduction of Ga{sup +} surface lone pair states at the top of the valence band and structure at the top of the valence band in Ga-segregated samples is assigned to these lone pair states. In addition photoemission reveals a broadening of the valence band edge. Core X-ray photoemission spectra and low energy ion scattering spectroscopy both reveal pronounced segregation of Ga to the ceramic surface, which may be linked to both relief of strain in the bulk and the preferential occupation of surface sites by lone pair cations. Surprisingly Ga segregation is not accompanied by the development of chemically shifted structure in Ga 2p core XPS associated with Ga{sup +}. However experiments on ion bombarded Ga{sub 2}O{sub 3}, where a shoulder at the top edge of the valence band spectra provide a clear signature of Ga{sup +} at the surface, show that the chemical shift between Ga{sup +} and Ga{sup 3+} is too small to be

  15. Fast imaging readout and electronics--a novel high-speed imaging system for micro-channel plates

    CERN Document Server

    Lapington, J S

    2002-01-01

    The band-width of charge division readout anodes used with micro-channel plates (MCP) is usually limited by the speed of the acquisition electronics. We present a novel charge division anode that does not require analogue to digital conversion. The Fast Imaging Readout and Electronics is a new concept in high-speed imaging using an MCP detector. The imaging system described comprises an MCP intensifier coupled to a charge division image readout using high-speed, multichannel electronics. It has a projected spatial resolution of up to 128x128 pixels, though the image format is inherently flexible, and the potential for rates up to 100 million events per second with nanosecond timing resolution. The readout pattern has a planar electrode structure and the collected charge from each event is shared amongst all electrodes, grouped in pairs. The unique design of the readout obviates the need for charge measurement, usually the dominant process determining the event-processing deadtime. Instead, high-speed signal c...

  16. Electronic structure and bonding interactions in Ba1- x Sr x Zr0.1Ti0.9O3 ceramics

    Science.gov (United States)

    Mangaiyarkkarasi, Jegannathan; Sasikumar, Subramanian; Saravanan, Olai Vasu; Saravanan, Ramachandran

    2017-06-01

    An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1- x Sr x Zr0.1Ti0.9O3 (short for BSZT, x = 0, 0.05, 0.07 and 0.14) ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method (MEM). Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiO3 structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.

  17. Electron crystallography of PhoE porin, an outer membrane, channel- forming protein from E. coli

    Energy Technology Data Exchange (ETDEWEB)

    Walian, P.J.

    1989-11-01

    One approach to studying the structure of membrane proteins is the use of electron crystallography. Dr. Bing Jap has crystallized PhoE pore-forming protein (porin) from the outer membrane of escherichia coli (E. coli) into monolayer crystals. The findings of this research and those of Jap (1988, 1989) have determined these crystals to be highly ordered, yielding structural information to a resolution of better than 2.8 angstroms. The task of this thesis has been to collect and process the electron diffraction patterns necessary to generate a complete three-dimensional set of high resolution structure factor amplitudes of PhoE porin. Fourier processing of these amplitudes when combined with the corresponding phase data is expected to yield the three-dimensional structure of PhoE porin at better than 3.5 angstroms resolution. 92 refs., 33 figs., 3 tabs. (CBS)

  18. Drawing the geometry of 3d transition metal-boron pairs in silicon from electron emission channeling experiments

    CERN Document Server

    Silva, Daniel; Wahl, Ulrich; Martins Correia, Joao; Augustyns, Valerie; De Lemos Lima, Tiago Abel; Granadeiro Costa, Angelo Rafael; David Bosne, Eric; Castro Ribeiro Da Silva, Manuel; Esteves De Araujo, Araujo Joao Pedro; Da Costa Pereira, Lino Miguel

    2016-01-01

    Although the formation of transition metal-boron pairs is currently well established in silicon processing, the geometry of these complexes is still not completely understood. We investigated the lattice location of the transition metals manganese, iron, cobalt and nickel in n- and p+-type silicon by means of electron emission channeling. For manganese, iron and cobalt, we observed an increase of sites near the ideal tetrahedral interstitial position by changing the doping from n- to p+-type Si. Such increase was not observed for Ni. We ascribe this increase to the formation of pairs with boron, driven by Coulomb interactions, since the majority of iron, manganese and cobalt is positively charged in p+-type silicon while Ni is neutral. We propose that breathing mode relaxation around the boron ion within the pair causes the observed displacement from the ideal tetrahedral interstitial site. We discuss the application of the emission channeling technique in this system and, in particular, how it provides insi...

  19. Electron energy dissipation model of gate dielectric progressive breakdown in n- and p-channel field effect transistors

    Science.gov (United States)

    Lombardo, S.; Wu, E. Y.; Stathis, J. H.

    2017-08-01

    We report the data and a model showing that the energy loss experienced by the carriers flowing through breakdown spots is the primary cause of progressive breakdown spot growth. The experiments are performed in gate dielectrics of metal-oxide-semiconductor (MOS) devices subjected to accelerated high electric field constant voltage stress under inversion conditions. The model is analytical and contains few free parameters of clear physical meaning. This is compared to a large set of data on breakdown transients at various oxide thicknesses, stress voltages, and temperatures, both in cases of n-channel and p-channel transistors and polycrystalline Si/oxynitride/Si and metal gate/high k dielectric/Si gate stacks. The basic idea is that the breakdown transient is due to the growth of one or more filaments in the dielectric promoted by electromigration driven by the energy lost by the electrons traveling through the breakdown spots. Both cases of polycrystalline Si/oxynitride/Si and metal gate/high-k dielectric/Si MOS structures are investigated. The best fit values of the model to the data, reported and discussed in the paper, consistently describe a large set of data. The case of simultaneous growth of multiple progressive breakdown spots in the same device is also discussed in detail.

  20. Design and characterization of a 32-channel heterodyne radiometer for electron cyclotron emission measurements on experimental advanced superconducting tokamak.

    Science.gov (United States)

    Han, X; Liu, X; Liu, Y; Domier, C W; Luhmann, N C; Li, E Z; Hu, L Q; Gao, X

    2014-07-01

    A 32-channel heterodyne radiometer has been developed for the measurement of electron cyclotron emission (ECE) on the experimental advanced superconducting tokamak (EAST). This system collects X-mode ECE radiation spanning a frequency range of 104-168 GHz, where the frequency coverage corresponds to a full radial coverage for the case with a toroidal magnetic field of 2.3 T. The frequency range is equally spaced every 2 GHz from 105.1 to 167.1 GHz with an RF bandwidth of ~500 MHz and the video bandwidth can be switched among 50, 100, 200, and 400 kHz. Design objectives and characterization of the system are presented in this paper. Preliminary results for plasma operation are also presented.

  1. Recent progress in ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E.

    1998-09-01

    Both fundamental and practical aspects of ceramic joining are understood well enough for many, if not most, applications requiring moderate strengths at room temperature. This paper argues that the two greatest needs in ceramic joining are for techniques to join buried interfaces by selective heating, and methods for joining ceramics for use at temperatures of 800 to 1,200 C. Heating with microwave radiation or with high-energy electron beams has been used to join buried ceramic interfaces, for example SiC to SiC. Joints with varying levels of strength at temperatures of 600 to 1,000 C have been made using four techniques: (1) transient liquid phase bonding; (2) joining with refractory braze alloys; (3) joining with refractory glass compositions; and (4) joining using preceramic polymers. Joint strengths as high as 550 MPa at 1,000 C have been reported for silicon nitride-silicon nitride bonds tested in four-point flexure.

  2. Dense ceramic membranes for methane conversion

    NARCIS (Netherlands)

    Bouwmeester, Henricus J.M.

    2003-01-01

    Dense ceramic membranes made from mixed oxygen-ionic and electronic conducting perovskite-related oxides allow separation of oxygen from an air supply at elevated temperatures (>700 °C). By combining air separation and catalytic partial oxidation of methane to syngas into a ceramic membrane reactor,

  3. Effects, determination, and correction of count rate nonlinearity in multi-channel analog electron detectors

    Science.gov (United States)

    Reber, T. J.; Plumb, N. C.; Waugh, J. A.; Dessau, D. S.

    2014-04-01

    Detector counting rate nonlinearity, though a known problem, is commonly ignored in the analysis of angle resolved photoemission spectroscopy where modern multichannel electron detection schemes using analog intensity scales are used. We focus on a nearly ubiquitous "inverse saturation" nonlinearity that makes the spectra falsely sharp and beautiful. These artificially enhanced spectra limit accurate quantitative analysis of the data, leading to mistaken spectral weights, Fermi energies, and peak widths. We present a method to rapidly detect and correct for this nonlinearity. This algorithm could be applicable for a wide range of nonlinear systems, beyond photoemission spectroscopy.

  4. Electronic structure of ceramic CrSi2 and WSi2: Compton spectroscopy and ab-initio calculations

    Science.gov (United States)

    Bhamu, K. C.; Sahariya, Jagrati; Ahuja, B. L.

    2013-05-01

    We report electron momentum densities of stable phases of transition metal disilicides CrSi2 (C40 hexagonal) and WSi2 (C11b body centered tetragonal) using a high energy 137Cs Compton spectrometer. To support the experimental investigations, we have computed theoretical Compton profiles, energy bands and density of states of both the isoelectronic compounds using density functional theory within linear combination of atomic orbitals. Theoretical calculations for the energy bands and density of states are performed for both the hexagonal and tetragonal phases of these silicides. In the tetragonal phase, both the silicides show metallic behavior. The hexagonal CrSi2 shows an energy gap (0.28 eV) between the valence band maximum at the L point and the conduction band minimum at the M point of the Brillouin zone, whereas the hexagonal WSi2 shows a semimetallic character. We have also scaled the experimental and theoretical profiles of the stable phases (hexagonal for CrSi2 and tetragonal for WSi2) on equal-valence-electron-density, which show more covalent character of WSi2 than that of CrSi2. The nature of bonding is in accordance with a present Mulliken's population analysis.

  5. ceramic pigment

    Indian Academy of Sciences (India)

    In contrast, the relatively poor blue colour obtained by dispersing Co2SiO4 into ceramic glazes is mainly attributed to the evolution of Co2+ initially in octahedral coordination of olivine structure to tetrahedral coordination of glassy phase. On the other hand, regarding the growing concern on. Co costs and environmental ...

  6. Microstructure and Mechanical Properties of Ti Cold-Spray Splats Determined by Electron Channeling Contrast Imaging and Nanoindentation Mapping.

    Science.gov (United States)

    Goldbaum, Dina; Chromik, Richard R; Brodusch, Nicolas; Gauvin, Raynald

    2015-06-01

    Cold spray is a thermo-mechanical process where the velocity of the sprayed particles affects the deformation, bonding, and mechanical properties of the deposited material, in the form of splats or coatings. At high strain rates, the impact stresses are converted into heat, a phenomenon known as adiabatic shear, which leads to grain re-crystallization. Grain re-crystallization and growth are shown to have a direct impact on the mechanical properties of the cold-sprayed material. The present study ties the microstructural features within the cold-sprayed Ti splats and the substrate to the bonding mechanism and mechanical properties. High-resolution electron channeling contrast imaging, electron backscatter diffraction mapping, and nanoindentation were used to correlate the microstructure to the mechanical properties distribution within the titanium cold-spray splats. The formation of nanograins was observed at the titanium splat/substrate interface and contributed to metallurgical bonding. An increase in grain re-crystallization within the splat and substrate materials was observed with pre-heating of the substrate. In the substrate material, the predominant mechanism of deformation was twinning. A good relationship was found between the hardness and distribution of the twins within the substrate and the size distribution of the re-crystallized grains within the splats.

  7. Auto-thermal reforming using mixed ion-electronic conducting ceramic membranes for a small-scale H₂ production plant.

    Science.gov (United States)

    Spallina, Vincenzo; Melchiori, Tommaso; Gallucci, Fausto; van Sint Annaland, Martin

    2015-03-18

    The integration of mixed ionic electronic conducting (MIEC) membranes for air separation in a small-to-medium scale unit for H2 production (in the range of 650-850 Nm3/h) via auto-thermal reforming of methane has been investigated in the present study. Membranes based on mixed ionic electronic conducting oxides such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) give sufficiently high oxygen fluxes at temperatures above 800 °C with high purity (higher than 99%). Experimental results of membrane permeation tests are presented and used for the reactor design with a detailed reactor model. The assessment of the H2 plant has been carried out for different operating conditions and reactor geometry and an energy analysis has been carried out with the flowsheeting software Aspen Plus, including also the turbomachines required for a proper thermal integration. A micro-gas turbine is integrated in the system in order to supply part of the electricity required in the system. The analysis of the system shows that the reforming efficiency is in the range of 62%-70% in the case where the temperature at the auto-thermal reforming membrane reactor (ATR-MR) is equal to 900 °C. When the electric consumption and the thermal export are included the efficiency of the plant approaches 74%-78%. The design of the reactor has been carried out using a reactor model linked to the Aspen flowsheet and the results show that with a larger reactor volume the performance of the system can be improved, especially because of the reduced electric consumption. From this analysis it has been found that for a production of about 790 Nm3/h pure H2, a reactor with a diameter of 1 m and length of 1.8 m with about 1500 membranes of 2 cm diameter is required.

  8. Impact parameter dependent electron capture by decelerated U{sup 91+} ions at 20 MeV/u using crystal channeling conditions

    Energy Technology Data Exchange (ETDEWEB)

    Dauvergne, D. E-mail: d.dauvergne@ipnl.in2p3.fr; Braeuning-Demian, A.; Bosch, F.; Braeuning, H.; Chevallier, M.; Cohen, C.; Gumberidze, A.; L' Hoir, A.; Kirsch, R.; Kozhuharov, C.; Liesen, D.; Mokler, P.H.; Poizat, J.C.; Ray, C.; Stoehlker, Th.; Tarisien, M.; Testa, E.; Toleikis, S.; Toulemonde, M

    2003-05-01

    We present results of an experiment using decelerated U{sup 91+} ions, extracted from the GSI-ESR storage ring, and transmitted through a thin silicon crystal in channeling conditions. Charge state at emergence, secondary electron multiplicity and X-rays are measured simultaneously. These conditions allow to study the competition between mechanical electron capture (MEC) and radiative electron capture (REC) as a function of impact parameter. We observe that REC is the dominant charge exchange process for the best channeled ions, i.e. those travelling always far from the silicon target core electrons. For ions with high transverse energy, MEC into highly excited states is counterbalanced by enhanced ionization arising from a succession of close collisions along atomic rows.

  9. Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

    Energy Technology Data Exchange (ETDEWEB)

    Deen, David A., E-mail: david.deen@alumni.nd.edu; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J. [Naval Research Laboratory, Electronics Science and Technology Division, Washington, DC 20375 (United States)

    2016-08-08

    A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics f{sub t}/f{sub max} of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with f{sub t}/f{sub max} of 48/60 GHz.

  10. Electronic structure and chemical bonding in La1-x Sr x MnO3 perovskite ceramics

    Science.gov (United States)

    Thenmozhi, N.; Sasikumar, S.; Sonai, S.; Saravanan, R.

    2017-04-01

    This study reports on the synthesis of La1-x Sr x MnO3 (x  =  0.3, 0.4 and 0.5) manganites by high temperature solid state reaction method using lanthanum oxide, strontium carbonate and manganese oxide as starting materials. The synthesized samples were characterized by XRD, UV-vis, SEM/EDS and VSM. Structural characterization shows that all the prepared samples have the perovskite rhombohedral structure. Influence of Sr doping on electron density distributions in the lattice structure of LaMnO3 were analyzed through maximum entropy method (MEM). Cell parameters are found to be decreasing with the addition of Sr content. The qualitative and quantitative analysis by MEM reveals that, incorporation of Sr into LaMnO3 lattice enhances the ionic nature between La and O ions and decreases the covalent nature between Mn and O ions. Optical band gap values are determined from the UV-visible absorption spectra. Particles with polygonal form are observed from the SEM micrographs. The elemental compositions of the synthesized samples are confirmed by EDS. The magnetic properties studied from the M-H plot taken at room temperature indicated that, the prepared samples are exhibited ferromagnetic behavior.

  11. Computational study of structural, elastic and electronic properties of lithium disilicate (Li(2)Si(2)O(5)) glass-ceramic.

    Science.gov (United States)

    Biskri, Zine Elabidine; Rached, Habib; Bouchear, Merzoug; Rached, Djamel

    2014-04-01

    The objective of this study is to investigate theoretically the structural, elastic and electronic properties of Lithium Disilicate (LD) crystal (Li2Si2O5), using the pseudo potential method based on Density Functional Theory (DFT) with the Local Density Approximation (LDA) and the Generalized Gradient Approximation (GGA). The calculated structural properties namely the equilibrium lattice parameters and cell volume are in good agreement with the available experimental results. However, for the LD crystal elastic moduli: Shear modulus G, Young's modulus E and Poisson's ratio ν we have found a discrepancy between our theoretical values and experimental ones reported in polycrystalline sample containing LD crystals. The calculated elastic properties show that LD is more rigid compared with other components. We also investigated the mechanical stability of Li2Si2O5 compound and we have noticed that this compound is stable against elastic deformations. On the basis of shear to bulk modulus ratio analysis, we inferred that Li2Si2O5 compound is brittle in nature. In order to complete the fundamental characteristics of this compound we have measured the elastic anisotropy. Our results for the energy band structure and Density of States (DOS) show that Li2Si2O5 compound has an insulator characteristic. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. X-Ray diffraction and scanning electron microscopy-energy dispersive spectroscopic analysis of ceramõmetal interface at different firing temperatures

    Directory of Open Access Journals (Sweden)

    Monika Saini

    2010-01-01

    Full Text Available Objective: Porcelain chipping from porcelain fused to metal restoration has been Achilles heel till date. There has been advent of newer ceramics in past but but none of them has been a panacea for Porcelain fracture. An optimal firing is thus essential for the clinical success of the porcelain-fused to metal restoration. The aim of the present study was to evaluate ceramo-metal interface at different firing temperature using XRD and SEM-EDS analysis. Clinical implication of the study was to predict the optimal firing temperature at which porcelain should be fused with metal in order to possibly prevent the occasional failure of the porcelain fused to metal restorations. Materials and Methods: To meet the above-mentioned goal, porcelain was fused to metal at different firing temperatures (930-990°C in vacuum. The microstructural observations of interface between porcelain and metal were evaluated using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. Results: Based on the experimental investigation of the interaction zone of porcelain fused to metal samples, it was observed that as the firing temperature was increased, the pores became less in number as well as the size of the pores decreased at the porcelain/metal interface upto 975°C but increased in size at 990°C. The least number of pores with least diameter were found in samples fired at 975°C. Several oxides like Cr 2 O 3 , NiO, and Al 2 O 3 and intermetallic compounds (CrSi 2 , AlNi 3 were also formed in the interaction zone. Conclusions : It is suggested that the presence of pores may trigger the crack propagation along the interface, causing the failure of the porcelain fused to metal restoration during masticatory action.

  13. Search for electroweak top quark production in the electron + jets channel in the D0 experiment at the Tevatron

    Energy Technology Data Exchange (ETDEWEB)

    Busato, Emmanuel [Paris Univ. (France)

    2005-04-01

    The top quark, whose mass approaches the electroweak symmetry breaking scale, is by far the heaviest known elementary particle. New physics is therefore expected to have its most important effect in the top sector. The Tevatron is, currently, the only collider able to produce the top quark. Among all possible production processes in the standard model, the top-antitop pair production via strong interaction, first observed in 1995, is the one with the largest cross section. The production via electroweak interaction (known as single top production), more difficult to extract from the background because of a lower cross section and of a lower signal to background ratio, has never been observed. In this thesis, we have searched for these processes by studying proton-antiproton collisions at $\\sqrt{s}$ =1.96 TeV produced by the Tevatron and detected with the DØ detector. The experimental study of the top quark is very sensitive to the quality of the data taken by the calorimeter. This detector showed, at the beginning of the Run II, rather important noise problems. Having identified the origin of the noise, new treatments at the offline level were implemented and their effects studied. It has been shown that these treatments reduce very significantly the effect of the noise in the reconstruction of physical quantities without notable degradation of the signal. Within the standard model, the top quark decays into W b with a branching ratio close to 100%. Leptonic decays of the into electron + neutrino have been used to identify the from the top decay. The main backgrounds to the single top signal ( +jets and QCD) are made essentially of light quark jets in the final state. Two ..-tagging algorithms have therefore been applied in order to improve the signal to background ratio. No evidence for electroweak top quark production has been found. Upper limits at the 95 % confidence level on the observed (expected) cross sections have be computed. They are found to be 14

  14. Building Atomic Models of the Ion Channels Based on Low Resolution Electron Microscopy Maps and Homology Modeling.

    Science.gov (United States)

    Novoseletsky, Valery; Malak, Olfat A; Loussouarn, Gildas; Sokolova, Olga S

    2018-01-01

    Voltage-gated potassium channels play pivotal roles in excitable and non-excitable cells. For many decades, structural properties and molecular mechanisms of these channels were inferred from functional observations. At the turn of the twenty-first century, structural biology revealed major aspects in the structural basis of ion channel organization, permeation, and gating. Among the available tools, homology modeling associated with low resolution microscopy helps in delineating the different structural elements of voltage-gated channels. Here, we describe in detail the methodology of homology modeling, using the 3D structure of the Kv2.1ΔCTA ion channel as a reference.

  15. Quasi-molecular electron promotion beyond the 1s$\\sigma$ and 2p$\\pi$ channels in slow collisions of He$^{2+}$ and He

    CERN Document Server

    Schmidt, L Ph H; Goihl, C; Jahnke, T; Schmidt-Böcking, H; Dörner, R

    2015-01-01

    The electron emission pattern of transfer-ionization in collisions of He$^{2+}$ with He was investigated for impact velocities between 0.53 a.u. and 0.77 a.u. (7 keV/u - 15 keV/u) employing recoil-ion momentum spectroscopy. This process is known to be dominated by the promotion of the 2p$\\pi$ molecular orbital into the continuum which results in "banana" shaped areas of high electron momentum densities extending from the target to the projectile in velocity space in the collision plain. Asymmetries are explained by a coherent superposition of the 2p$\\pi$ channel of the quasi molecular promotion with the 1s$\\sigma$ channel. Here we report on an additional contribution of higher angular momentum molecular states for close collisions which emerge at smaller impact velocities. They show up as highly structured electron emission patterns in the plane perpendicular to the direction of impact.

  16. Channel electron multiplier operated on a sounding rocket without a cryogenic vacuum pump from 120 - 75 km altitude

    Science.gov (United States)

    Dickson, S.; Gausa, M. A.; Robertson, S. H.; Sternovsky, Z.

    2012-12-01

    We demonstrate that a channel electron multiplier (CEM) can be operated on a sounding rocket in the pulse-counting mode from 120 km to 75 km altitude without the cryogenic evacuation used in the past. Evacuation of the CEM is provided only by aerodynamic flow around the rocket. This demonstration is motivated by the need for additional flights of mass spectrometers to clarify the fate of metallic compounds and ions ablated from micrometeorites and their possible role in the nucleation of noctilucent clouds. The CEMs were flown as guest instruments on the two sounding rockets of the CHAMPS (CHarge And mass of Meteoritic smoke ParticleS) rocket campaign which were launched into the mesosphere in October 2011 from Andøya Rocket Range, Norway. Modeling of the aerodynamic flow around the payload with Direct Simulation Monte-Carlo (DSMC) code showed that the pressure is reduced below ambient in the void beneath an aft-facing surface. An enclosure containing the CEM was placed above an aft-facing deck and a valve was opened on the downleg to expose the CEM to the aerodynamically evacuated region below. The CEM operated successfully from apogee down to ~75 km. A Pirani gauge confirmed pressures reduced to as low as 20% of ambient with the extent of reduction dependent upon altitude and velocity. Additional DSMC simulations indicate that there are alternate payload designs with improved aerodynamic pumping for forward mounted instruments such as mass spectrometers.

  17. Channel electron multiplier operated on a sounding rocket without a cryogenic vacuum pump from 120 to 80 km altitude

    Science.gov (United States)

    Dickson, Shannon; Gausa, Michael; Robertson, Scott; Sternovsky, Zoltan

    2013-04-01

    We demonstrate that a channel electron multiplier (CEM) can be operated on a sounding rocket in the pulse-counting mode from 120 km to 80 km altitude without the cryogenic evacuation used in the past. Evacuation of the CEM is provided only by aerodynamic flow around the rocket. This demonstration is motivated by the need for additional flights of mass spectrometers to clarify the fate of metallic compounds and ions ablated from micrometeorites and their possible role in the nucleation of noctilucent clouds. The CEMs were flown as guest instruments on two sounding rockets to the mesosphere. Modeling of the aerodynamic flow around the payload with Direct Simulation Monte-Carlo (DSMC) code showed that the pressure is reduced below ambient in the void behind (relative to the direction of motion) an aft-facing surface. An enclosure containing the CEM was placed forward of an aft-facing deck and a valve was opened during flight to expose the CEM to the aerodynamically evacuated region behind it. The CEM operated successfully from apogee down to ∼80 km. A Pirani gauge confirmed pressures reduced to as low as 20% of ambient with the extent of reduction dependent upon altitude and velocity. Additional DSMC simulations indicate that there are alternate payload designs with improved aerodynamic pumping for forward mounted instruments such as mass spectrometers.

  18. A Multi-Channel Opto-Electronic Sensor to Accurately Monitor Heart Rate against Motion Artefact during Exercise

    Directory of Open Access Journals (Sweden)

    Abdullah Alzahrani

    2015-10-01

    Full Text Available This study presents the use of a multi-channel opto-electronic sensor (OEPS to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare. The aim of this work was to study how to capture the heart rate (HR efficiently through a well-constructed OEPS and a 3-axis accelerometer with wireless communication. A protocol was designed to incorporate sitting, standing, walking, running and cycling. The datasets collected from these activities were processed to elaborate sport physiological effects. t-test, Bland-Altman Agreement (BAA, and correlation to evaluate the performance of the OEPS were used against Polar and Mio-Alpha HR monitors. No differences in the HR were found between OEPS, and either Polar or Mio-Alpha (both p > 0.05; a strong correlation was found between Polar and OEPS (r: 0.96, p < 0.001; the bias of BAA 0.85 bpm, the standard deviation (SD 9.20 bpm, and the limits of agreement (LOA from −17.18 bpm to +18.88 bpm. For the Mio-Alpha and OEPS, a strong correlation was found (r: 0.96, p < 0.001; the bias of BAA 1.63 bpm, SD 8.62 bpm, LOA from −15.27 bpm to +18.58 bpm. These results demonstrate the OEPS to be capable of carrying out real time and remote monitoring of heart rate.

  19. Polarization-mediated Debye-screening of surface potential fluctuations in dual-channel AlN/GaN high electron mobility transistors

    Science.gov (United States)

    Deen, David A.; Miller, Ross A.; Osinsky, Andrei V.; Downey, Brian P.; Storm, David F.; Meyer, David J.; Scott Katzer, D.; Nepal, Neeraj

    2016-12-01

    A dual-channel AlN/GaN/AlN/GaN high electron mobility transistor (HEMT) architecture is proposed, simulated, and demonstrated that suppresses gate lag due to surface-originated trapped charge. Dual two-dimensional electron gas (2DEG) channels are utilized such that the top 2DEG serves as an equipotential that screens potential fluctuations resulting from surface trapped charge. The bottom channel serves as the transistor's modulated channel. Two device modeling approaches have been performed as a means to guide the device design and to elucidate the relationship between the design and performance metrics. The modeling efforts include a self-consistent Poisson-Schrodinger solution for electrostatic simulation as well as hydrodynamic three-dimensional device modeling for three-dimensional electrostatics, steady-state, and transient simulations. Experimental results validated the HEMT design whereby homo-epitaxial growth on free-standing GaN substrates and fabrication of the same-wafer dual-channel and recessed-gate AlN/GaN HEMTs have been demonstrated. Notable pulsed-gate performance has been achieved by the fabricated HEMTs through a gate lag ratio of 0.86 with minimal drain current collapse while maintaining high levels of dc and rf performance.

  20. Novel intramolecular photoinduced electron transfer-based probe for the Human Ether-a-go-go-Related Gene (hERG) potassium channel.

    Science.gov (United States)

    Liu, Zhenzhen; Zhou, Yubin; Du, Lupei; Li, Minyong

    2015-12-21

    Drug induced long QT syndrome is a high risk event in clinic, which mainly results from their high affinity to the Human Ether-a-go-go-Related Gene (hERG) potassium channel. Therefore, evaluation of the drug's inhibitory activity against the hERG potassium channel is a required step in drug discovery and development. In this study, we developed a series of novel conformation-mediated intramolecular photoinduced electron transfer fluorogenic probes for the hERG potassium channel. After careful evaluation, probes N4 and N6 showed good activity and may have a promising application in the cell-based hERG potassium channel inhibitory activity assay, as well as potential hERG-associated cardiotoxicity evaluation. Compared with other assay methods, such as patch clamp assay, radio-ligand competitive binding assay, fluorescence polarization and potential-sensitive fluorescent probes, this method is convenient and can also selectively measure the inhibitory activity in the native state of the hERG potassium channel. Meanwhile, these probes can also be used for hERG potassium channel imaging without complex washing steps.

  1. Monolithic ceramics

    Science.gov (United States)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

    A development history and current development status evaluation are presented for SiC and Si3N4 monolithic ceramics. In the absence of widely sought improvements in these materials' toughness, and associated reliability in structural applications, uses will remain restricted to components in noncritical, nonman-rated aerospace applications such as cruise missile and drone gas turbine engine components. In such high temperature engine-section components, projected costs lie below those associated with superalloy-based short-life/expendable engines. Advancements are required in processing technology for the sake of fewer and smaller microstructural flaws.

  2. Comparative analysis of hot-electron transport in AlGaN/GaN and AlGaN/AlN/GaN 2DEG channels

    Energy Technology Data Exchange (ETDEWEB)

    Ardaravicius, L.; Ramonas, M.; Kiprijanovic, O.; Liberis, J.; Matulionis, A. [Semiconductor Physics Institute, A. Gostauto 11, 01108 Vilnius (Lithuania); Eastman, L.F.; Shealy, J.R.; Chen, X.; Sun, Y.J. [Cornell University, 425 Philips Hall, Ithaca, NY 14853 (United States)

    2005-04-01

    Nanosecond-pulsed current-voltage measurements were used to study hot-electron transport in undoped AlGaN/GaN and AlGaN/AlN/GaN two-dimensional electron gas channels biased up to 200 kV/cm. Voltage pulses of 1 ns were applied in order to minimize channel heating. The current saturated at 100 kV/cm in the AlN-interbarrier-contained structures; the estimated saturated drift velocity was about 1.1 x 10{sup 7} cm/s. No saturation of the current was observed in AlGaN/GaN channels in the field range below 200 kV/cm. Monte Carlo simulation of hot-electron transport was carried out with electron gas degeneracy and hot phonons taken into account. A fairly good fit of the experimental results with the Monte Carlo simulation data was obtained in the electric field range up to 30 kV/cm. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. A fractographic study of clinically retrieved zirconia-ceramic and metal-ceramic fixed dental prostheses.

    Science.gov (United States)

    Pang, Zhen; Chughtai, Asima; Sailer, Irena; Zhang, Yu

    2015-10-01

    A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia-ceramic and metal-ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia-ceramic systems occurred more frequently than those in metal-ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis. Vinyl-polysiloxane impressions of 12 zirconia-ceramic and 6 metal-ceramic FDPs with veneer fractures were taken from the patients at the end of a mean observation of 40.3±2.8 months. Epoxy replicas were produced from these impressions [1]. All replicas were gold coated, and inspected under the optical microscope and scanning electron microscope (SEM) for descriptive fractography. Among the 12 zirconia-ceramic FDPs, 2 had small chippings, 9 had large chippings, and 1 exhibited delamination. Out of 6 metal-ceramic FDPs, 5 had small chippings and 1 had large chipping. Descriptive fractographic analysis based on SEM observations revealed that fracture initiated from the wear facet at the occlusal surface in all cases, irrespective of the type of restoration. Zirconia-ceramic and metal-ceramic FDPs all fractured from microcracks that emanated from occlusal wear facets. The relatively low fracture toughness and high residual tensile stress in porcelain veneer of zirconia restorations may contribute to the higher chipping rate and larger chip size in zirconia-ceramic FDPs relative to their metal-ceramic counterparts. The low veneer/core interfacial fracture energy of porcelain-veneered zirconia may result in the occurrence of delamination in zirconia-ceramic FDPs. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. A fractographic study of clinically retrieved zirconia–ceramic and metal–ceramic fixed dental prostheses

    Science.gov (United States)

    Pang, Zhen; Chughtai, Asima; Sailer, Irena; Zhang, Yu

    2015-01-01

    Objectives A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia–ceramic and metal–ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia–ceramic systems occurred more frequently than those in metal–ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis. Methods Vinyl-polysiloxane impressions of 12 zirconia–ceramic and 6 metal–ceramic FDPs with veneer fractures were taken from the patients at the end of a mean observation of 40.3 ± 2.8 months. Epoxy replicas were produced from these impressions [1]. All replicas were gold coated, and inspected under the optical microscope and scanning electron microscope (SEM) for descriptive fractography. Results Among the 12 zirconia–ceramic FDPs, 2 had small chippings, 9 had large chippings, and 1 exhibited delamination. Out of 6 metal–ceramic FDPs, 5 had small chippings and 1 had large chipping. Descriptive fractographic analysis based on SEM observations revealed that fracture initiated from the wear facet at the occlusal surface in all cases, irrespective of the type of restoration. Significance Zirconia–ceramic and metal–ceramic FDPs all fractured from microcracks that emanated from occlusal wear facets. The relatively low fracture toughness and high residual tensile stress in porcelain veneer of zirconia restorations may contribute to the higher chipping rate and larger chip size in zirconia–ceramic FDPs relative to their metal–ceramic counterparts. The low veneer/core interfacial fracture energy of porcelain-veneered zirconia may result in the occurrence of delamination in zirconia–ceramic FDPs. PMID:26233469

  5. Physicochemical characterization of ceramics from Sao Paulo II archaeological site; Caracterizacao fisico-quimica da ceramica do sitio arqueologico Sao Paulo II

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Rogerio Baria

    2013-08-01

    Archaeometry is a consolidated field with a wide application of nuclear analytical techniques for the characterization, protection, and restoration of archaeological pieces. This project aimed at studying the elementary chemical composition of 70 ceramic fragments samples from Sao Paulo II archaeological site, located along the Solimoes River channel, next to Coari city, in Brazilian Amazon. The characterization of samples was performed by neutron activation analysis (NAA). By the determination of 24 elements in the ceramic fragments ( Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Sb, Sm. Rb, Se, Ta, Tb, Th, U, Yb and Zn), it was possible to define groups of samples regarding the similarity/dissimilarity in elementary chemical composition. For such a task, the multivariate statistical methods employed were cluster analysis (C A), principal component analysis (PCA) and discriminant analysis (DA). Afterwards, seven ceramic fragments were selected based on the groups previously established, for the characterization of the site temporal horizon. Those ceramic fragments were analyzed by thermoluminescence (TL) and EPR for dating purposes. The firing temperatures were determined by electron paramagnetic resonance (EPR) technique, in order to infer about some aspects of the ceramic manufacture employed by the ancient peoples that lived in Sao Paulo 11. By the results obtained in this study, it was possible to identify the quantity of clay sources employed by the ceramists and the age of the ceramic pieces. Therefore, the results of this research may contribute to the study on the occupation dynamics in the pre-colonial Brazilian Amazon. (author)

  6. Development of multi-channel apparatus for electron-atom Compton scattering to study the momentum distribution of atoms in a molecule.

    Science.gov (United States)

    Yamazaki, Masakazu; Hosono, Masaki; Tang, Yaguo; Takahashi, Masahiko

    2017-06-01

    We have developed multi-channel apparatus for electron-atom Compton scattering to study the momentum distribution of atoms in a molecule. It combines the features of both a spherical electron energy analyzer and a large-area position sensitive detector, thereby having an ability to cover almost completely the azimuthal angle range available for quasi-elastic electron Rutherford backscattering at an angle of 135°. Details and performance of the apparatus are reported, together with experimental results measured for Xe and CH4 at an incident electron energy of 2 keV. In particular, it is shown that the instrumental sensitivity is remarkably high, which has increased the signal count rate by nearly three orders of magnitude compared to existing setups. This technical progress would be useful for advancing atomic momentum spectroscopy studies.

  7. Design and characterization of a 64 channels ASIC front-end electronics for high-flux particle beam detectors

    Science.gov (United States)

    Fausti, F.; Mazza, G.; Attili, A.; Mazinani, M. Fadavi; Giordanengo, S.; Lavagno, M.; Manganaro, L.; Marchetto, F.; Monaco, V.; Sacchi, R.; Vignati, A.; Cirio, R.

    2017-09-01

    A new wide-input range 64-channels current-to-frequency converter ASIC has been developed and characterized for applications in beam monitoring of therapeutic particle beams. This chip, named TERA09, has been designed to extend the input current range, compared to the previous versions of the chip, for dealing with high-flux pulsed beams. A particular care was devoted in achieving a good conversion linearity over a wide bipolar input current range. Using a charge quantum of 200 fC, a linearity within ±2% for an input current range between 3 nA and 12 μA is obtained for individual channels, with a gain spread among the channels of about 3%. By connecting all the 64 channels of the chip to a common input, the current range can be increased 64 times preserving a linearity within ±3% in the range between and 20 μA and 750 μA.

  8. Electrospun Ceramic Nanofiber Mats Today: Synthesis, Properties, and Applications

    Directory of Open Access Journals (Sweden)

    Hamid Esfahani

    2017-10-01

    Full Text Available Ceramic nanofibers (NFs have recently been developed for advanced applications due to their unique properties. In this article, we review developments in electrospun ceramic NFs with regard to their fabrication process, properties, and applications. We find that surface activity of electrospun ceramic NFs is improved by post pyrolysis, hydrothermal, and carbothermal processes. Also, when combined with another surface modification methods, electrospun ceramic NFs result in the advancement of properties and widening of the application domains. With the decrease in diameter and length of a fiber, many properties of fibrous materials are modified; characteristics of such ceramic NFs are different from their wide and long (bulk counterparts. In this article, electrospun ceramic NFs are reviewed with an emphasis on their applications as catalysts, membranes, sensors, biomaterials, fuel cells, batteries, supercapacitors, energy harvesting systems, electric and magnetic parts, conductive wires, and wearable electronic textiles. Furthermore, properties of ceramic nanofibers, which enable the above applications, and techniques to characterize them are briefly outlined.

  9. Microstructural characterization of nuclear-waste ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ryerson, F.J.; Clarke, D.R.

    1982-09-22

    Characterization of nuclear waste ceramics requires techniques possessing high spatial and x-ray resolution. XRD, SEM, electron microprobe, TEM and analytical EM techniques are applied to ceramic formulations designed to immobilize both commercial and defense-related reactor wastes. These materials are used to address the strengths and limitations of the techniques above. An iterative approach combining all these techniques is suggested. 16 figures, 2 tables.

  10. Concerning the width of spark channels with different polarities in submicrosecond sliding discharges in noble gases

    Science.gov (United States)

    Trusov, K. K.

    2010-02-01

    Previously, the parameters of submicrosecond (with a duration of ceramic surface in Ne, Ar, and Xe were studied only for the negative polarity of the applied voltage. The experimental data indicate that the channels expand in the transverse direction mainly due to electron drift from the channel surface layer under the action of the electric field perpendicular to the channel axis and subsequent gas ionization by these electrons. To investigate mechanisms for the channel development in a sliding discharge—in particular, to determine the contribution of electron drift—it is necessary to carry out experiments similar to those performed earlier for the opposite polarity of the applied voltage. Here, the results of measurements of the widths of the spark channels of negativeand positive-polarity sliding discharges excited in Ne, Ar, and Xe at pressures of 30 and 100 kPa are presented and discussed. It is shown that, depending on the pressure and sort of gas, the averaged optical width of positive-polarity channels is smaller by a factor of 1.27-1.60 than that of negative-polarity channels. The experimental data are analyzed using the theory of propagation of ionization waves with different polarities in gases. Analysis has shown that electron diffusion contributes insignificantly to channel expansion and that, for both polarities, the channel expansion rate exceeds the electron drift velocity in the transverse electric field near the channel. In the framework of the so-called approximation of nonlocalized initial conditions, the measured ratio between of the widths of negativeand positive-polarity channels and their relation to the electron mobility are explained by the channel expansion governed by both electron drift and primary free electrons produced by a short-term source in a narrow region ahead of the front of the expansion wave. Numerical simulations show that the width of this region is comparable with that of the wave front and is more than one order of

  11. 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.

    Science.gov (United States)

    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.

  12. Electrospinning as a tool for fabricating functional ceramics

    OpenAIRE

    Cadafalch Gazquez, G.

    2016-01-01

    Ceramic micro and nanomaterials have gained interest by the research community during last decade. They have contributed to improved performance in the fields of catalysis, biomedicine, energy and electronics. Amongst these ceramic materials, nanofibers have shown good potential; their large aspect ratio enhances several material properties. This PhD thesis focuses on the development of novel functional ceramic fibers and nanochannels. Different materials were fabricated, characterized and te...

  13. Characterization of ceramic powders used in the inCeram systems to fixed dental Prosthesis

    Directory of Open Access Journals (Sweden)

    Alexandra Almeida Diego

    2007-03-01

    Full Text Available InCeram (Vita Zahnfabrik- Germany is known as a high strength ceramic being used for core crowns and for fixed partial denture frameworks. InCeram system consists of slip-casting technique which is used for to build the framework, which is then pre-sintered obtaining an open-pore microstructure. The material gains its strength by infiltration of the lanthanum glass into the porous microstructure. In this work, commercial alumina (Al2O3, alumina-zirconia (Al2O3-ZrO2 and glasses lanthanum oxide-rich powders, used in InCeram system, were characterized, using x ray diffraction, dilatometry and scanning electron microscopy. The characteristics of these powders were related aiming to consider their substitution for new ceramic materials.

  14. Verification of ceramic structures

    NARCIS (Netherlands)

    Behar-Lafenetre, S.; Cornillon, L.; Rancurel, M.; Graaf, D. de; Hartmann, P.; Coe, G.; Laine, B.

    2012-01-01

    In the framework of the "Mechanical Design and Verification Methodologies for Ceramic Structures" contract [1] awarded by ESA, Thales Alenia Space has investigated literature and practices in affiliated industries to propose a methodological guideline for verification of ceramic spacecraft and

  15. Ceramic Laser Materials

    Directory of Open Access Journals (Sweden)

    Guillermo Villalobos

    2012-02-01

    Full Text Available Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements.

  16. Joining Ceramics By Brazing

    Science.gov (United States)

    Chiaramonte, Francis P.; Sudsina, Michael W.

    1992-01-01

    Certain ceramic materials tightly bond together by brazing with suitable alloys. Enables fabrication of parts of wide variety of shapes from smaller initial pieces of ceramics produced directly in only limited variety of shapes.

  17. Citizens and service channels: channel choice and channel management implications

    NARCIS (Netherlands)

    Pieterson, Willem Jan

    2010-01-01

    The arrival of electronic channels in the 1990s has had a huge impact on governmental service delivery. The new channels have led to many new opportunities to improve public service delivery, not only in terms of citizen satisfaction, but also in cost reduction for governmental agencies. However,

  18. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, G H; Belhage, B; Schousboe, A

    1992-01-01

    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect imm...... of THIP-treated cultures. This suggests that primarily low affinity GABAA-receptors are closely associated with Ca2+ channels and this may be important for the ability of these receptors to mediate an inhibitory action on transmitter release even under extreme depolarizing conditions....

  19. Tritium transport in lithium ceramics porous media

    Energy Technology Data Exchange (ETDEWEB)

    Tam, S.W.; Ambrose, V.

    1991-12-31

    A random network model has been utilized to analyze the problem of tritium percolation through porous Li ceramic breeders. Local transport in each pore channel is described by a set of convection-diffusion-reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the porous medium is accounted for via Monte Carlo methods. The model was then applied to an analysis of the relative contribution of diffusion and convective flow to tritium transport in porous lithium ceramics. 15 refs., 4 figs.

  20. Tritium transport in lithium ceramics porous media

    Energy Technology Data Exchange (ETDEWEB)

    Tam, S.W.; Ambrose, V.

    1991-01-01

    A random network model has been utilized to analyze the problem of tritium percolation through porous Li ceramic breeders. Local transport in each pore channel is described by a set of convection-diffusion-reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the porous medium is accounted for via Monte Carlo methods. The model was then applied to an analysis of the relative contribution of diffusion and convective flow to tritium transport in porous lithium ceramics. 15 refs., 4 figs.

  1. Single-top production t-channel cross section measurement in the electron+jets final state at ATLAS with 35 pb{sup -1}of data

    Energy Technology Data Exchange (ETDEWEB)

    Khoriauli, Gia

    2012-07-15

    The cross section of the Standard Model electroweak production of a single top quark in the t-channel has been measured using the LHC proton-proton collision data at {radical}(s)=7 TeV, 35 pb{sup -1} of integrated luminosity, recorded by the ATLAS detector during the year 2010. The measurement has been based on a selection of the collision events with an electron and one b-tagged hadronic jet in the central region of the detector and one extra jet in the forward region of the detector. These requirements are dictated by the topology of the final state particles in the t-channel process. They helped to optimize an expected fraction of the t-channel process, according to a study based on Monte-Carlo simulation, in the selected events and suppress the contribution of the background processes. The main background processes such as production of hadronic jets via the strong interaction and production of a single W boson with associated hadronic jets are measured by means of data driven methods developed in this work. The measured cross section of single top quark production in the t-channel process is 59{sup +44}{sub -39}(stat.){sup +63}{sub -39}(syst.) pb. The measured upper limit on the cross section is 226 pb at the 95% confidence level. The results are in agreement with the latest theoretical prediction of the t-channel cross section of the Standard Model production of a single top quark calculated at NNLO, 64.6{sup +3.3}{sub -2.6} pb, considering m {sub t-quark}=172.5 GeV.

  2. An electron paramagnetic resonance spectroscopy investigation of the retention mechanisms of Mn and Cu in the nanopore channels of three zeolite minerals

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Daniel R.; Schulthess, Cristian P.; Amonette, James E.; Walter, Eric D.

    2012-12-01

    The adsorption mechanisms of divalent cations in zeolite nanopore channels can vary as a function of their pore dimensions. The nanopore inner-sphere enhancement (NISE) theory predicts that ions may dehydrate inside small nanopore channels in order to adsorb more closely to the mineral surface if the nanopore channel is sufficiently small. The results of an electron paramagnetic resonance (EPR) spectroscopy study of Mn and Cu adsorption on the zeolite minerals zeolite Y (large nanopores), ZSM-5 (intermediate nanopores), and mordenite (small nanopores) are presented. The Cu and Mn cations both adsorbed via an outer-sphere mechanism on zeolite Y based on the similarity between the adsorbed spectra and the aqueous spectra. Conversely, Mn and Cu adsorbed via an inner-sphere mechanism on mordenite based on spectrum asymmetry and peak broadening of the adsorbed spectra. However, Mn adsorbed via an outer-sphere mechanism on ZSM-5, whereas Cu adsorbed on ZSM-5 shows a high degree of surface interaction that indicates that it is adsorbed closer to the mineral surface. Evidence of dehydration and immobility was more readily evident in the spectrum of mordenite than ZSM-5, indicating that Cu was not as close to the surface on ZSM-5 as it was when adsorbed on mordenite. Divalent Mn cations are strongly hydrated and are held strongly only in zeolites with small nanopore channels. Divalent Cu cations are also strongly hydrated, but can dehydrate more easily, presumably due to the Jahn-Teller effect, and are held strongly in zeolites with medium sized nanopore channels or smaller.

  3. Radiopaque strontium fluoroapatite glass-ceramics

    Directory of Open Access Journals (Sweden)

    Wolfram eHöland

    2015-10-01

    Full Text Available The controlled precipitation of strontium fluoroapatite crystals, was studied in four base glass compositions derived from the SiO2 – Al2O3 – Y2O3 – SrO – Na2O – K2O/Rb2O/Cs2O – P2O5 – F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: a Sr5(PO43F – leucite, KAlSi2O6 , b Sr5(PO43F – leucite, KAlSi2O6, and nano-sized NaSrPO4 c Sr5(PO43F – pollucite, CsAlSiO4 , and nano-sized NaSrPO4, d Sr5(PO43F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4.The proof of crystal phase formation was possible by X-ray diffraction (XRD. The microstructures, which were studied using scanning electron microscopy (SEM demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needlelike morphology. The study of the crystal growth of needlelike Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism.The formation of leucite, pollucite and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal

  4. Additive manufacturing of polymer-derived ceramics

    Science.gov (United States)

    Eckel, Zak C.; Zhou, Chaoyin; Martin, John H.; Jacobsen, Alan J.; Carter, William B.; Schaedler, Tobias A.

    2016-01-01

    The extremely high melting point of many ceramics adds challenges to additive manufacturing as compared with metals and polymers. Because ceramics cannot be cast or machined easily, three-dimensional (3D) printing enables a big leap in geometrical flexibility. We report preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture. These polymer structures can be pyrolyzed to a ceramic with uniform shrinkage and virtually no porosity. Silicon oxycarbide microlattice and honeycomb cellular materials fabricated with this approach exhibit higher strength than ceramic foams of similar density. Additive manufacturing of such materials is of interest for propulsion components, thermal protection systems, porous burners, microelectromechanical systems, and electronic device packaging.

  5. Preparation of biomorphic SiC ceramics

    Directory of Open Access Journals (Sweden)

    Egelja A.

    2008-01-01

    Full Text Available This paper deals with a new method for producing non-oxide ceramic using wood as a template. SiC with a woodlike microstructure has been prepared by carbothermal reduction reactions of Tilia wood/TEOS composite at 1873K. The porous carbon preform was infiltrated with TEOS (Si(OC2H54, as a source of silica, without pressure at 298K. The morphology of resulting porous SiC ceramics, as well as the conversion mechanism of wood to SiC ceramics, have been investigated by scanning electron microscopy (SEM/EDS and X-ray diffraction analysis (XRD. Obtained SiC ceramics consists of β-SiC with traces of α-SiC.

  6. Creep in ceramics

    CERN Document Server

    Pelleg, Joshua

    2017-01-01

    This textbook is one of its kind, since there are no other books on Creep in Ceramics. The book consist of two parts: A and B. In part A general knowledge of creep in ceramics is considered, while part B specifies creep in technologically important ceramics. Part B covers creep in oxide ceramics, carnides and nitrides. While covering all relevant information regarding raw materials and characterization of creep in ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  7. Thin film ceramic thermocouples

    Science.gov (United States)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  8. Ceramic gas turbine shroud

    Science.gov (United States)

    Shi, Jun; Green, Kevin E.

    2014-07-22

    An example gas turbine engine shroud includes a first annular ceramic wall having an inner side for resisting high temperature turbine engine gasses and an outer side with a plurality of radial slots. A second annular metallic wall is positioned radially outwardly of and enclosing the first annular ceramic wall and has a plurality of tabs in communication with the slot of the first annular ceramic wall. The tabs of the second annular metallic wall and slots of the first annular ceramic wall are in communication such that the first annular ceramic wall and second annular metallic wall are affixed.

  9. Electrospinning as a tool for fabricating functional ceramics

    NARCIS (Netherlands)

    Cadafalch Gazquez, G.

    2016-01-01

    Ceramic micro and nanomaterials have gained interest by the research community during last decade. They have contributed to improved performance in the fields of catalysis, biomedicine, energy and electronics. Amongst these ceramic materials, nanofibers have shown good potential; their large aspect

  10. Channeling of high-power radio waves under conditions of strong anomalous absorption in the presence of an averaged electron heating source

    Science.gov (United States)

    Vas'kov, V. V.; Ryabova, N. A.

    2010-02-01

    Strong anomalous absorption of a high-power radio wave by small-scale plasma inhomogeneities in the Earth’s ionosphere can lead to the formation of self-consistent channels (solitons) in which the wave propagates along the magnetic field, but has a soliton-like intensity distribution across the field. The structure of a cylindrical soliton as a function of the wave intensity at the soliton axis is analyzed. Averaged density perturbations leading to wave focusing were calculated using the model proposed earlier by Vas’kov and Gurevich (Geomagn. Aéron. 16, 1112 (1976)), in which an averaged electron heating source was used. It is shown that, under conditions of strong electron recombination, the radii of individual solitons do not exceed 650 m.

  11. Marginal discrepancy of monolithic and veneered all-ceramic crowns on titanium and zirconia implant abutments before and after adhesive cementation: a scanning electron microscopy analysis.

    Science.gov (United States)

    Martinez-Rus, Francisco; Ferreiroa, Alberto; Ozcan, Mutlu; Pradies, Guillermo

    2013-01-01

    To evaluate the marginal discrepancy of monolithic and veneered all-ceramic crown systems cemented on titanium (Ti) and zirconia implant abutments. Sixty customized implant abutments for a maxillary right central incisor were fabricated of Ti and zirconia (n = 30 of each) for an internal-connection implant system. All-ceramic crowns were fabricated using the following systems (n = 10 per group): monolithic with computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD), pressed lithium disilicate (PLD), or CAD yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP). The frameworks of the PLD and Y-TZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were cemented to their implant abutments, and the absolute marginal discrepancy of the gap was measured before and after cementation. Data were analyzed statistically. Marginal discrepancies were significantly influenced by the crown system and by cementation, but the material did not significantly affect the results. Interaction terms were not significant. Y-TZP crowns on both Ti and zirconia abutments presented the smallest mean marginal discrepancies before (52.1 ± 17 μm and 56.2 ± 11 μm, respectively) and after cementation (98.7 ± 17 μm and 101.8 ± 16 μm, respectively). Before cementation, MLD crowns showed significantly larger mean marginal openings than PLD crowns on both Ti and zirconia abutments (75.2 ± 12 and 77.5 ± 13 μm for MLD, 52.1 ± 17 μm and 69.7 ± 8 μm for PLD, respectively). After cementation, both Ti and zirconia abutments with MLD crowns (113.5 ± 12 μm and 118.3 ± 14 μm, respectively) showed significantly larger values than with PLD crowns (98.7 ± 17 μm and 109.4 ± 9 μm, respectively). Manually veneered Y-TZP crowns demonstrated more favorable marginal fit on both Ti and zirconia implant abutments before and after cementation compared to those of MLD and PLD.

  12. Single-top production t-channel cross section measurement in the electron+jets final state at ATLAS with $35 pb^{−1}$ of data

    CERN Document Server

    Khoriauli, Gia; Wermes, Norbert

    The cross section of the Standard Model electroweak production of a single top quark in the t-channel has been measured using the LHC proton-proton collision data at $sqrt{s} = 7$ TeV, $35 pb^{−1}$ of integrated luminosity, recorded by the ATLAS detector during the year 2010. The measurement has been based on a selection of the collision events with an electron and one b-tagged hadronic jet in the central region of the detector and one extra jet in the forward region of the detector. These requirements are dictated by the topology of the final state particles in the t-channel process. They helped to optimize an expected fraction of the t-channel process, according to a study based on Monte-Carlo simulation, in the selected events and suppress the contribution of the background processes. The main background processes such as production of hadronic jets via the strong interaction and production of a single W boson with associated hadronic jets are measured by means of data driven methods developed in this wo...

  13. The Electrospun Ceramic Hollow Nanofibers

    Directory of Open Access Journals (Sweden)

    Shahin Homaeigohar

    2017-11-01

    Full Text Available Hollow nanofibers are largely gaining interest from the scientific community for diverse applications in the fields of sensing, energy, health, and environment. The main reasons are: their extensive surface area that increases the possibilities of engineering, their larger accessible active area, their porosity, and their sensitivity. In particular, semiconductor ceramic hollow nanofibers show greater space charge modulation depth, higher electronic transport properties, and shorter ion or electron diffusion length (e.g., for an enhanced charging–discharging rate. In this review, we discuss and introduce the latest developments of ceramic hollow nanofiber materials in terms of synthesis approaches. Particularly, electrospinning derivatives will be highlighted. The electrospun ceramic hollow nanofibers will be reviewed with respect to their most widely studied components, i.e., metal oxides. These nanostructures have been mainly suggested for energy and environmental remediation. Despite the various advantages of such one dimensional (1D nanostructures, their fabrication strategies need to be improved to increase their practical use. The domain of nanofabrication is still advancing, and its predictable shortcomings and bottlenecks must be identified and addressed. Inconsistency of the hollow nanostructure with regard to their composition and dimensions could be one of such challenges. Moreover, their poor scalability hinders their wide applicability for commercialization and industrial use.

  14. Design of LTCC-based Ceramic Structure for Chemical Microreactor

    Directory of Open Access Journals (Sweden)

    D. Belavic

    2012-04-01

    Full Text Available The design of ceramic chemical microreactor for the production of hydrogen needed in portable polymer-electrolyte membrane (PEM fuel cells is presented. The microreactor was developed for the steam reforming of liquid fuels with water into hydrogen. The complex three-dimensional ceramic structure of the microreactor includes evaporator(s, mixer(s, reformer and combustor. Low-temperature co-fired ceramic (LTCC technology was used to fabricate the ceramic structures with buried cavities and channels, and thick-film technology was used to make electrical heaters, temperature sensors and pressure sensors. The final 3D ceramic structure consists of 45 LTCC tapes. The dimensions of the structure are 75 × 41 × 9 mm3 and the weight is about 73 g.

  15. Impact of strain on electronic and transport properties of 6 nm hydrogenated germanane nano-ribbon channel double gate field effect transistor

    Science.gov (United States)

    Meher Abhinav, E.; Sundararaj, Anuraj; Gopalakrishnan, Chandrasekaran; Kasmir Raja, S. V.; Chokhra, Saurabh

    2017-11-01

    In this work, chair like fully hydrogenated germanane (CGeH) nano-ribbon 6 nm short channel double gate field effect transistor (DG-FET) has been modeled and the impact of strain on the I–V characteristics of CGeH channel has been examined. The bond lengths, binding and formation energies of various hydrogenated geometries of buckled germanane channel were calculated using local density approximation (LDA) with Perdew–Zunger (PZ) and generalized gradient approximation (GGA) with Perdew Burke Ernzerhof (PBE) parameterization. From four various geometries, chair like structure is found to be more stable compared to boat like obtuse, stiruup structure and table like structure. The bandgap versus width, bandgap versus strain characteristics and I–V characteristics had been analyzed at room temperature using density functional theory (DFT). Using self consistent calculation it was observed that the electronic properties of nano-ribbon is independent of length and band structure, but dependent on edge type, strain [Uni-axial (ε xx ), bi-axial (ε xx   =  ε yy )] and width of the ribbon. The strain engineered hydrogenated germanane (GeH) showed wide direct bandgap (2.3 eV) which could help to build low noise electronic devices that operates at high frequencies. The observed bi-axial compression has high impact on the device transport characteristics with peak to valley ratio (PVR) of 2.14 and 380% increase in peak current compared to pristine CGeH device. The observed strain in CGeH DG-FET could facilitate in designing novel multiple-logic memory devices due to multiple negative differential resistance (NDR) regions.

  16. Investigation of planar channeling radiation on diamond and quartz crystals at electron energies between 14 and 34 MeV and probing the influence of ultrasonic waves on channeling radiation

    Energy Technology Data Exchange (ETDEWEB)

    Azadegan, B.

    2007-11-15

    Measurements of planar channeling radiation (CR) have been performed at the electron beam of ELBE within an energy range between 14 and 34 MeV and for thicknesses of the diamond crystals between 42.5 and 500 {mu}m. Absolute CR photon yields have for the first time been obtained for the above given ranges of electron energy and crystal thickness. The square-root dependence of the planar CR photon yield on the thickness of diamond crystals has been confirmed. A systematic quantitative investigation of the influence of the crystal thickness on the CR line shape has for the first time been performed. The mean-squared multiple-scattering angle effective for planar CR observed in forward direction has been found to be weaker as assumed from scattering in amorphous targets. Scaling laws deduced from the measured CR data are of advantage for the operation of a CR source. The second part of this thesis deals with the possibility of stimulation of CR emission by means of ultrasonic vibrations excited in a piezoelectric single crystal. Since the knowledge of the CR spectra generated on undisturbed quartz crystals is a necessary precondition for some investigation of the influence of US, planar CR has for the first time been measured at medium electron energies for a variety of planes in quartz. As a consequence of the hexagonal structure of this crystal, relative intense CR could be registered even out of planes with indices larger than one. On the base of the non-linear optics method, occupation functions and spectral distributions of planar CR have been calculated for channeling of 20 MeV electrons in the (01 anti 15) plane of a 20 {mu}m thick quartz crystal at resonant influence of ultrasound (US). The resonance frequencies have been deduced from the measurements of CR spectra performed on quartz. First experimental investigations of the influence of US on CR started at ELBE aimed at the study of the effect of non-resonant ultrasonic vibrations excited in a 500 {mu}m thick

  17. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

    Science and Technology of Ceramics. 2. Functional Ceramics. Sheela Ramasesha. In Part 11 we saw that ceramics could be broadly classified as traditional and advanced ceramics. Traditional ceramics are those made from naturally occurring materials like clays and minerals without requiring much refinement. In this part ...

  18. A multi-channel THz and infrared spectrometer for femtosecond electron bunch diagnostics by single-shot spectroscopy of coherent radiation

    Energy Technology Data Exchange (ETDEWEB)

    Wesch, Stephan; Schmidt, Bernhard; Behrens, Christopher; Delsim-Hashemi, Hossein; Schmueser, Peter

    2011-08-15

    The high peak current required in free-electron lasers (FELs) is realized by longitudinal compression of the electron bunches to sub-picosecond length. In this paper, a frequency-domain diagnostic method is described that is capable of resolving structures in the femtosecond regime. A novel in-vacuum spectrometer has been developed for spectroscopy of coherent radiation in the THz and infrared range. The spectrometer is equipped with five consecutive dispersion gratings and 120 parallel readout channels; it can be operated either in short wavelength mode (5-44 {mu}m) or in long wavelength mode (45-430 {mu}m). Fast parallel readout permits the spectroscopy of coherent radiation from single electron bunches. Test measurements at the soft X-ray free-electron laser FLASH, using coherent transition radiation, demonstrate excellent performance of the spectrometer. The high sensitivity down to a few micrometers allows study of short bunch features caused for example by microbunching e ects in magnetic chicanes. The device is planned for use as an online bunch profile monitor during regular FEL operation. (orig.)

  19. The impact of kaolin dehydroxylation on the porosity and mechanical integrity of kaolin based ceramics using different pore formers

    Directory of Open Access Journals (Sweden)

    David O. Obada

    Full Text Available Thermally induced lattice defects in kaolin play a key role in the mechanical integrity of kaolin based ceramics during heat treatment due to their phase transformations. The effects of three types of pore formers (sawdust, styrofoam and powdery high density polyethylene on the porosity and mechanical integrity of kaolin based ceramics have been studied based on their batch formulations. The porosity of the ceramic bodies was experimentally determined, while the structure and chemistry of the materials were elucidated via X-ray diffraction (XRD, scanning electron microscopy (SEM, FTIR, DSC/TG/DTA, and zeta potential. The kaolin-based porous samples sintered at 1150 °C exhibited mullite phase transformation attributed to recrystallization effects. Morphologically, open pores were distributed on the sample surfaces due to larger pathways and available channels of eviction of the pore formers. Compressive strength decreased linearly as apparent porosity increased signifying its correlation. The compressive strength showed to be much more sensitive to defects created by dehydroxylation as micro cracks were observed on the sample with HDPE as pore former which could be as a result of large volume change accompanying phase transformations and sensitivity to the dehydroxylation phase. It is noted that the new pore former (HDPE used in this study produced ceramic bodies with porosity as high as 67% and hence the least compressive strength. Keywords: Porosity, Kaolin clay, Mechanical property, Lattice defects, Calcination

  20. Expression of calcium channel CaV1.3 in cat spinal cord: light and electron microscopic immunohistochemical study

    DEFF Research Database (Denmark)

    Zhang, Mengliang; Møller, Morten; Broman, Jonas

    2008-01-01

    In spinal neurons, plateau potentials serve to amplify neuronal input signals. To a large extent, the underlying persistent inward current is mediated by a subtype of the L-type calcium channel (Ca(V)1.3). In the present investigation, we have studied its distribution and cellular localization...... enlargements and the phrenic nucleus in cervical, Clarke's nucleus in lower thoracic and upper lumbar, and Onuf's nucleus in upper sacral segments. At the ultrastructural level, Ca(V)1.3-immunoreactive products were found in neuronal somata and dendrites of different sizes. In the soma, they were predominantly...

  1. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    Energy Technology Data Exchange (ETDEWEB)

    Sliney, H.E.; Dellacorte, C. (NASA Lewis Research Center, Cleveland, OH (United States))

    1994-07-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel-based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  2. Proton conducting cerate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Coffey, G.W.; Pederson, L.R.; Armstrong, T.R.; Bates, J.L.; Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States)

    1995-08-01

    Cerate perovskites of the general formula AM{sub x}Ce{sub 1-x}O{sub 3-{delta}}, where A = Sr or Ba and where M = Gd, Nd, Y, Yb or other rare earth dopant, are known to conduct a protonic current. Such materials may be useful as the electrolyte in a solid oxide fuel cell operating at intermediate temperatures, as an electrochemical hydrogen separation membrane, or as a hydrogen sensor. Conduction mechanisms in these materials were evaluated using dc cyclic voltammetry and mass spectrometry, allowing currents and activation energies for proton, electron, and oxygen ion contributions to the total current to be determined. For SrYb{sub 0.05}Ce{sub 0.95}O{sub 3-{delta}}, one of the best and most environmentally stable compositions, proton conduction followed two different mechanisms: a low temperature process, characterized by an activation energy of 0.42{+-}0.04 eV, and a high temperature process, characterized by an activation energy of 1.38{+-}0.13 eV. It is believed that the low temperature process is dominated by grain boundary conduction while bulk conduction is responsible for the high temperature process. The activation energy for oxygen ion conduction (0.97{+-}0.10 eV) agrees well with other oxygen conductors, while that for electronic conduction, 0.90{+-}0.09 eV, is affected by a temperature-dependent electron carrier concentration. Evaluated by direct measurement of mass flux through a dense ceramic with an applied dc field, oxygen ions were determined to be the majority charge carrier except at the lowest temperatures, followed by electrons and then protons.

  3. NDE of ceramics and ceramic composites

    Science.gov (United States)

    Vary, Alex A.; Klima, Stanley J.

    Although nondestructive evaluation (NDE) techniques for ceramics are fairly well developed, they are difficult to apply in many cases for high probability detection of the minute flaws that can cause failure in monolithic ceramics. Conventional NDE techniques are available for monolithic and fiber reinforced ceramic matrix composites, but more exact quantitative techniques needed are still being investigated and developed. Needs range from flaw detection to below 100 micron levels in monolithic ceramics to global imaging of fiber architecture and matrix densification anomalies in ceramic composites. NDE techniques that will ultimately be applicable to production and quality control of ceramic structures are still emerging from the lab. Needs are different depending on the processing stage, fabrication method, and nature of the finished product. NDE techniques are being developed in concert with materials processing research where they can provide feedback information to processing development and quality improvement. NDE techniques also serve as research tools for materials characterization and for understanding failure processes, e.g., during thermomechanical testing.

  4. Antibacterial ceramic for sandbox. Sunabayo kokin ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, K. (Ishizuka Glass Co. Ltd. Nagoya (Japan))

    1993-10-01

    Sands in sandboxes in parks have been called into question of being contaminated by colon bacilli and spawns from ascarides. This paper introduces an antibacterial ceramic for sandbox developed as a new material effective to help reduce the contamination. The ceramic uses natural sand as the main raw material, which is added with borax and silver to contain silver ions that have bacteria and fungus resistance and deodorizing effect. The ceramic has an average grain size ranging from 0.5 mm to 0.7 mm, and is so devised as to match specific gravity, grain size and shape of the sand, hence no separation and segregation can occur. The result of weatherability and antibacterial strength tests on sand for a sandbox mixed with the ceramic at 1% suggests that its efficacy lasts for about three years. Its actual use is under observation. Its efficacy has been verified in a test that measures a survival factor of spawns from dog ascardides contacted with aqueous solution containing the ceramic at 1%. Safety and sanitation tests have proved the ceramic a highly safe product that conforms to the food sanitation law. 5 refs., 3 figs., 3 tabs.

  5. Ceramic laser materials

    Science.gov (United States)

    Ikesue, Akio; Aung, Yan Lin

    2008-12-01

    The word 'ceramics' is derived from the Greek keramos, meaning pottery and porcelain. The opaque and translucent cement and clay often used in tableware are not appropriate for optical applications because of the high content of optical scattering sources, that is, defects. Recently, scientists have shown that by eliminating the defects, a new, refined ceramic material - polycrystalline ceramic - can be produced. This advanced ceramic material offers practical laser generation and is anticipated to be a highly attractive alternative to conventional glass and single-crystal laser technologies in the future. Here we review the history of the development of ceramic lasers, the principle of laser generation based on this material, some typical results achieved with ceramic lasers so far, and discuss the potential future outlook for the field.

  6. Analyses of fine paste ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sabloff, J A [ed.

    1980-01-01

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

  7. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 2. Science and Technology of Ceramics - Advanced Ceramics: Structural Ceramics and Glasses. Sheela K Ramasesha. Series Article Volume 5 Issue 2 February 2000 pp 4-11 ...

  8. Continuous Fiber Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    None

    2002-09-01

    Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

  9. Space group analysis of Sr1-xCaxTiO3 ceramics with x = 0.20, 0.27 and 0.30 through electron diffraction

    Science.gov (United States)

    Anwar, Shahid; Lalla, N. P.

    2007-10-01

    The space groups of Sr1-xCaxTiO3 in the composition range 0.20xx-ray diffraction (XRD) and electron diffraction techniques. Electron diffraction has been used in selected area diffraction (SAD), convergent beam electron diffraction (CBED) and micro-diffraction modes to record zero-order Laue zone (ZOLZ) and higher-order Laue zone (HOLZ) patterns. For the 0.20xx<=0.30) two types of phase coexist at room temperature. These are the Pnma and P 21212 orthorhombic phases, coexisting with volume fractions of about 40% and 60% respectively.

  10. Modeling of Noise and Resistance of Semimetal Hg1-xCdxTe Quantum Well used as a Channel for THz Hot-Electron Bolometer.

    Science.gov (United States)

    Melezhik, E O; Gumenjuk-Sichevska, J V; Sizov, F F

    2016-12-01

    Noise characteristics and resistance of semimetal-type mercury-cadmium-telluride quantum wells (QWs) at the liquid nitrogen temperature are studied numerically, and their dependence on the QW parameters and on the electron concentration is established. The QW band structure calculations are based on the full 8-band k.p Hamiltonian. The electron mobility is simulated by the direct iterative solution of the Boltzmann transport equation, which allows us to include correctly all the principal scattering mechanisms, elastic as well as inelastic.We find that the generation-recombination noise is strongly suppressed due to the very fast recombination processes in semimetal QWs. Hence, the thermal noise should be considered as a main THz sensitivity-limiting mechanism in those structures. Optimization of a semimetal Hg1-xCdxTe QW to make it an efficient THz bolometer channel should include the increase of electron concentration in the well and tuning the molar composition x close to the gapless regime.

  11. Contact Resistance and Channel Conductance of Graphene Field-Effect Transistors under Low-Energy Electron Irradiation

    Directory of Open Access Journals (Sweden)

    Filippo Giubileo

    2016-11-01

    Full Text Available We studied the effects of low-energy electron beam irradiation up to 10 keV on graphene-based field effect transistors. We fabricated metallic bilayer electrodes to contact mono- and bi-layer graphene flakes on SiO2, obtaining specific contact resistivity ρ c ≈ 19 k Ω · µ m 2 and carrier mobility as high as 4000 cm2·V−1·s−1. By using a highly doped p-Si/SiO2 substrate as the back gate, we analyzed the transport properties of the device and the dependence on the pressure and on the electron bombardment. We demonstrate herein that low energy irradiation is detrimental to the transistor current capability, resulting in an increase in contact resistance and a reduction in carrier mobility, even at electron doses as low as 30 e−/nm2. We also show that irradiated devices recover their pristine state after few repeated electrical measurements.

  12. Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  13. On the nature of transport in near-critical dissipative-trapped-electron-mode turbulence: effect of a sudominant diffusive channel

    Energy Technology Data Exchange (ETDEWEB)

    Mier, Jose Angel [Universidad Carlos III, Madrid, Spain; Sanchez, Raul [ORNL; Garcia, Luis [Universidad Carlos III, Madrid, Spain; Newman, David E [University of Alaska; Carreras, Benjamin A [BACV Solutions, Inc., Oak Ridge

    2008-01-01

    The change in nature of radial transport in numerical simulations of near-critical dissipative-trapped-electron-mode turbulence is characterized as the relative strength of an additional diffusive transport channel (subdominant to turbulence) is increased from zero. In its absence, radial transport exhibits the lack of spatial and temporal scales characteristic of self-organized-critical systems. This dynamical regime survives up to diffusivity values which, for the system investigated here, greatly exceeds the expected neoclassical value. These results, obtained using a novel Lagrangian method, complete and extend previous works based instead on the use of techniques imported from the study of cellular automata [J. A. Mier et al., Phys. Plasmas 13, 102308 (2006)]. They also shed further light on why some features of self-organized criticality seem to be observed in magnetically confined plasmas in spite of the presence of mechanisms which apparently violate the conditions needed for its establishment.

  14. Zn-vapor diffused Er:Yb:LiNbO 3 channel waveguides fabricated by means of SiO 2 electron cyclotron resonance plasma deposition

    Science.gov (United States)

    Pernas, P. L.; Hernández, M. J.; Ruíz, E.; Cantelar, E.; Nevado, R.; Morant, C.; Lifante, G.; Cussó, F.

    2000-07-01

    We report here the fabrication method and operation of Zinc-vapor diffused channel waveguides on Erbium/Ytterbium (Er/Yb)-doped Lithium Niobate (LiNbO 3). electron cyclotron resonance (ECR) plasma deposition technique, UV photolithography and Reactive Ion Etching (RIE) are used to define an SiO 2 mask for pattern transfer. The whole process is performed at low temperatures eliminating typical LiO 2 out-diffusion problems and achieving low surface damage. The flexibility of the fabrication technology has been shown to be potentially applicable to integrated optics. EDAX measurements reveal good confinement and homogeneity of the diffused regions. Atomic Force Microscopy (AFM) surface characterization shows the swelling of the diffused areas, consistent with the topoepitaxial growth of a Zn xLi yNb zO w layer.

  15. Intergrown new zeolite beta polymorphs with interconnected 12-ring channels solved by combining electron crystallography and single-crystal X-ray diffraction

    KAUST Repository

    Yu, Zhengbao

    2012-10-09

    Two new polymorphs of zeolite beta, denoted as SU-78A and SU-78B, were synthesized by employing dicyclohexylammonium hydroxides as organic structure-directing agents. The structure was solved by combining transmission electron microscopy and single-crystal X-ray diffraction. SU-78 is an intergrowth of SU-78A and SU-78B and contains interconnected 12-ring channels in three directions. The two polymorphs are built from the same building layer, similar to that for the zeolite beta family. The layer stacking in SU-78, however, is different from those in zeolite beta polymorph A, B, and C, showing new zeolite framework topologies. SU-78 is thermally stable up to 600 °C. © 2012 American Chemical Society.

  16. Tensile strength of bilayered ceramics and corresponding glass veneers.

    Science.gov (United States)

    Anunmana, Chuchai; Champirat, Tharee; Jirajariyavej, Bundhit

    2014-06-01

    To investigate the microtensile bond strength between two all-ceramic systems; lithium disilicate glass ceramic and zirconia core ceramics bonded with their corresponding glass veneers. Blocks of core ceramics (IPS e.max® Press and Lava™ Frame) were fabricated and veneered with their corresponding glass veneers. The bilayered blocks were cut into microbars; 8 mm in length and 1 mm(2) in cross-sectional area (n = 30/group). Additionally, monolithic microbars of these two veneers (IPS e.max® Ceram and Lava™ Ceram; n = 30/group) were also prepared. The obtained microbars were tested in tension until fracture, and the fracture surfaces of the microbars were examined with fluorescent black light and scanning electron microscope (SEM) to identify the mode of failure. One-way ANOVA and the Dunnett's T3 test were performed to determine significant differences of the mean microtensile bond strength at a significance level of 0.05. The mean microtensile bond strength of IPS e.max® Press/IPS e.max® Ceram (43.40 ± 5.51 MPa) was significantly greater than that of Lava™ Frame/Lava™ Ceram (31.71 ± 7.03 MPa)(Pveneer layer. Furthermore, the bond strength of Lava™ Frame/Lava™ Ceram was comparable to the tensile strength of monolithic glass veneer of Lava™ Ceram, while the bond strength of bilayered IPS e.max® Press/IPS e.max® Ceram was significantly greater than tensile strength of monolithic IPS e.max® Ceram. Because fracture site occurred mostly in the glass veneer and most failures were away from the interfacial zone, microtensile bond test may not be a suitable test for bonding integrity. Fracture mechanics approach such as fracture toughness of the interface may be more appropriate to represent the bonding quality between two materials.

  17. Electron collisions with phenol: Total, integral, differential, and momentum transfer cross sections and the role of multichannel coupling effects on the elastic channel

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Romarly F. da [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580 Santo André, São Paulo (Brazil); Oliveira, Eliane M. de; Lima, Marco A. P. [Instituto de Física “Gleb Wataghin,” Universidade Estadual de Campinas, 13083-859 Campinas, São Paulo (Brazil); Bettega, Márcio H. F. [Departamento de Física, Universidade Federal do Paraná, CP 19044, 81531-990 Curitiba, Paraná (Brazil); Varella, Márcio T. do N. [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, São Paulo (Brazil); Jones, Darryl B. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Brunger, Michael J. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); Blanco, Francisco [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Ciudad Universitaria, 2840 Madrid (Spain); Colmenares, Rafael [Hospital Ramón y Cajal, 28034 Madrid (Spain); and others

    2015-03-14

    We report theoretical and experimental total cross sections for electron scattering by phenol (C{sub 6}H{sub 5}OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the N{sub open}-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the number of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)].

  18. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-02-01

    This is the fifth quarterly report on a new study to develop a ceramic membrane/metal joint. Results of wetting experiments on commercially available Nickel based brazing alloys on perovskite surfaces are described. Additionally, experimental and numerical investigations on the strength of concentric ceramic/metal joints are presented.

  19. Ceramic heat exchanger

    Science.gov (United States)

    LaHaye, P.G.; Rahman, F.H.; Lebeau, T.P.; Severin, B.K.

    1998-06-16

    A tube containment system is disclosed. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture. 6 figs.

  20. Brazing vacuum ceramic tubes for magnets applications

    Energy Technology Data Exchange (ETDEWEB)

    Bagnato, O.R.; Francisco, R.F. [Laboratorio Nacional de Luz Sincrotron (LNLS), SP (Brazil); Gobbi, A.L. [Laboratorio Nacional de Nanotecbologia (LNNano), SP (Brazil); Falvo, T. [Engecer Ltda, Sao Carlos, SP (Brazil)

    2014-07-01

    Full text: The Sirius Project is an initiative of the Brazilian Synchrotron Light Laboratory - LNLS (CNPEM - MCTI ), for the design, construction and operation of a new synchrotron radiation source 3rd generation, with high brightness and energy of the electrons of 3. 0 GeV. Among many other components, will be built 80 ceramic cameras embedded in specials magnets, whose function is to act to correct the orbit of the electron beam in the storage ring. The ceramic chamber is crucial for this application because this material is transparent to the magnetic field generated in the electro magnet and thus acts directly on the electron beam. The difficulty of these constructive components lies in the fact that, the ceramic components must be attached to metal components will join vacuum chambers that make up the ring, and then must present excellent mechanical and vacuum tight. The process of chemical bonding between the ceramic and metal components is performed by brazing in high vacuum. After brazing, is deposited a film of copper with 7 micrometers thickness. The objective of this paper is to describe the process of film deposition and brazing of copper and the excellent results obtained in the production, mechanical characterization, microstructural and tightness. The results obtained with the process indicate an homogeneous film with high adhesion and electrical resistance near the estimated values??. Tests are being carried out by XPS and SEM techniques for chemical and structural characterization. (author)

  1. Rapid imaging of misfit dislocations in SiGe/Si in cross-section and through oxide layers using electron channeling contrast

    Science.gov (United States)

    Mukherjee, Kunal; Wacaser, Brent A.; Bedell, Stephen W.; Sadana, Devendra K.

    2017-06-01

    Electron channeling contrast imaging (ECCI) is emerging as a technique for rapid and high-resolution characterization of individual crystalline defects in a scanning electron microscope. However, the application of ECCI to semiconductor materials has been limited to bare samples in plan-view geometry. In this paper, two modalities of this technique are demonstrated with relevance to semiconductor manufacturing and failure analysis: (1) The use of ECCI to reveal misfit dislocation defects along a cleaved cross-section of a SiGe compositionally graded buffer grown on Si and (2) plan-view imaging of misfit dislocations in metamorphic SiGe/Si layers covered by amorphous oxide layers, where the partial loss of contrast due to the oxide layers is quantified and the effect of the beam accelerating voltage is studied. These results demonstrate the power of ECCI in inspecting crystallographic defects non-destructively over large areas, which is highly desirable for substrate quality control in manufacturing of products based on crystalline materials.

  2. Dual-channel cathodic electrochemiluminescence of luminol induced by injection of hot electrons on a niobate semiconductor modified electrode.

    Science.gov (United States)

    Xu, Huifeng; Ye, Hongzhi; Zhu, Xi; Liang, Shijing; Guo, Longhua; Lin, Zhenyu; Liu, Xianxiang; Chen, Guonan

    2013-01-07

    In this paper, a new niobate semiconductor photocatalyst Sr(0.4)H(1.2)Nb(2)O(6)·H(2)O (HSN) nanoparticle was applied to investigate the cathodic electrochemiluminescent (ECL) behavior of luminol for the first time. The results presented here demonstrated that there were two ECL peaks of luminol at the cathodic potential attributed to immobilization of HSN on the electrode surface. It is implied that HSN can be electrically excited and injected electrons into aqueous electrolytes from this electrode under a quite low potential that only excites luminol. A mechanism for this luminol-ECL system on HSN/GCE has been proposed. Additionally, this HSN/GCE has lots of advantages, such as high stability, good anti-interference ability, simple instrumentation, rapid procedure and ultrasensitive ECL response. It is envisioned that this HSN/GCE has further applications in biosensors.

  3. Characterization of some bioglass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    ElBatal, H.A.; Azooz, M.A.; Khalil, E.M.A.; Soltan Monem, A.; Hamdy, Y.M

    2003-06-26

    Controlled crystallization were carried out to convert some selected bioglasses to their corresponding bioglass-ceramics. Nucleation and crystallization regimes were carried out by parameters obtained from diloatometric measurement and differential thermal analysis (DTA). The formed crystalline phases were identified using X-ray diffraction investigation. Complete surface analyses were performed utilizing scanning electron microscopy. Also, the infrared reflection spectroscopy of the bioglass-ceramics were measured before and after immersion for prolonged times in simulated body fluid and the results were compared with the same behavior for the parent bioglasses. Experimental results indicate the formation of two main crystalline phases of sodium calcium silicate beside three other crystalline phases formed according to the change in the bioglass composition, namely, calcium sodium borate, calcium phosphate and calcium silicate. The bioactivity rate determined by the infrared reflection spectroscopy revealed slight retardation with the bioglass-ceramics except in the bioglasses containing high SiO{sub 2} content.

  4. Anionic Conducting Oxide Ceramics

    National Research Council Canada - National Science Library

    Dunn, Bruce

    1998-01-01

    This program has emphasized the interrelationships among synthesis, microstructure and properties for oxygen ion conducting ceramics based on copper-substituted bismuth vanadate (Bi V Cu O ), known as BICUVOX...

  5. Making Ceramic Cameras

    Science.gov (United States)

    Squibb, Matt

    2009-01-01

    This article describes how to make a clay camera. This idea of creating functional cameras from clay allows students to experience ceramics, photography, and painting all in one unit. (Contains 1 resource and 3 online resources.)

  6. Ceramic fiber filter technology

    Energy Technology Data Exchange (ETDEWEB)

    Holmes, B.L.; Janney, M.A.

    1996-06-01

    Fibrous filters have been used for centuries to protect individuals from dust, disease, smoke, and other gases or particulates. In the 1970s and 1980s ceramic filters were developed for filtration of hot exhaust gases from diesel engines. Tubular, or candle, filters have been made to remove particles from gases in pressurized fluidized-bed combustion and gasification-combined-cycle power plants. Very efficient filtration is necessary in power plants to protect the turbine blades. The limited lifespan of ceramic candle filters has been a major obstacle in their development. The present work is focused on forming fibrous ceramic filters using a papermaking technique. These filters are highly porous and therefore very lightweight. The papermaking process consists of filtering a slurry of ceramic fibers through a steel screen to form paper. Papermaking and the selection of materials will be discussed, as well as preliminary results describing the geometry of papers and relative strengths.

  7. Light emitting ceramic device

    Science.gov (United States)

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  8. All ceramic structure for molten carbonate fuel cell

    Science.gov (United States)

    Smith, James L.; Kucera, Eugenia H.

    1992-01-01

    An all-ceramic molten carbonate fuel cell having a composition formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The structure includes an anode and cathode separated by an electronically conductive interconnect. The electrodes and interconnect are compositions ceramic materials. Various combinations of ceramic compositions for the anode, cathode and interconnect are disclosed. The fuel cell exhibits stability in the fuel gas and oxidizing environments. It presents reduced sealing and expansion problems in fabrication and has improved long-term corrosion resistance.

  9. Laser ceramics with rare-earth-doped anisotropic materials.

    Science.gov (United States)

    Akiyama, Jun; Sato, Yoichi; Taira, Takunori

    2010-11-01

    The fabrication of laser-grade anisotropic ceramics by a conventional sintering process is not possible owing to optical scattering at randomly oriented grain boundaries. In this Letter, we report the first (to our knowledge) realization of transparent anisotropic ceramics by using a new crystal orientation process based on large magnetic anisotropy induced by 4f electrons. By slip casting in a 1.4 T magnetic field and subsequent heat treatments, we could successfully fabricate laser-grade calcium fluorapatite ceramics with a loss coefficient of 1.5 cm(-1).

  10. Performance enhancement in p-channel charge-trapping flash memory devices with Si/Ge super-lattice channel and band-to-band tunneling induced hot-electron injection

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Li-Jung [Department of Engineering and System Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan, ROC (China); Chang-Liao, Kuei-Shu, E-mail: Lkschang@ess.nthu.edu.tw [Department of Engineering and System Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan, ROC (China); Jian, Yi-Chuen; Wang, Tien-Ko [Department of Engineering and System Science, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan, ROC (China); Tsai, Ming-Jinn [Electronics and Opto-electronics Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Rd., Chutung, Hsinchu 31040, Taiwan, ROC (China)

    2013-04-30

    P-channel charge-trapping flash memory devices with Si, SiGe, and Si/Ge super-lattice channel are investigated in this work. A Si/Ge super-lattice structure with extremely low roughness and good crystal structure is obtained by precisely controlling the epitaxy thickness of Ge layer. Both programming and erasing (P/E) speeds are significantly improved by employing this Si/Ge super-lattice channel. Moreover, satisfactory retention and excellent endurance characteristics up to 10{sup 6} P/E cycles with 3.8 V memory window show that the degradation on reliability properties is negligible when super-lattice channel is introduced. - Highlights: ► A super-lattice structure is proposed to introduce more Ge content into channel. ► Super-lattice structure possesses low roughness and good crystal structure. ► P-channel flash devices with Si, SiGe, and super-lattice channel are investigated. ► Programming/erasing speeds are significantly improved. ► Reliability properties can be kept for device with super-lattice channel.

  11. Auto-Thermal Reforming Using Mixed Ion-Electronic Conducting Ceramic Membranes for a Small-Scale H2 Production Plant

    Directory of Open Access Journals (Sweden)

    Vincenzo Spallina

    2015-03-01

    Full Text Available The integration of mixed ionic electronic conducting (MIEC membranes for air separation in a small-to-medium scale unit for H2 production (in the range of 650–850 Nm3/h via auto-thermal reforming of methane has been investigated in the present study. Membranes based on mixed ionic electronic conducting oxides such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF give sufficiently high oxygen fluxes at temperatures above 800 °C with high purity (higher than 99%. Experimental results of membrane permeation tests are presented and used for the reactor design with a detailed reactor model. The assessment of the H2 plant has been carried out for different operating conditions and reactor geometry and an energy analysis has been carried out with the flowsheeting software Aspen Plus, including also the turbomachines required for a proper thermal integration. A micro-gas turbine is integrated in the system in order to supply part of the electricity required in the system. The analysis of the system shows that the reforming efficiency is in the range of 62%–70% in the case where the temperature at the auto-thermal reforming membrane reactor (ATR-MR is equal to 900 °C. When the electric consumption and the thermal export are included the efficiency of the plant approaches 74%–78%. The design of the reactor has been carried out using a reactor model linked to the Aspen flowsheet and the results show that with a larger reactor volume the performance of the system can be improved, especially because of the reduced electric consumption. From this analysis it has been found that for a production of about 790 Nm3/h pure H2, a reactor with a diameter of 1 m and length of 1.8 m with about 1500 membranes of 2 cm diameter is required.

  12. The stoichiometry of the TMEM16A ion channel determined in intact plasma membranes of COS-7 cells using liquid-phase electron microscopy.

    Science.gov (United States)

    Peckys, Diana B; Stoerger, Christof; Latta, Lorenz; Wissenbach, Ulrich; Flockerzi, Veit; de Jonge, Niels

    2017-08-01

    TMEM16A is a membrane protein forming a calcium-activated chloride channel. A homodimeric stoichiometry of the TMEM16 family of proteins has been reported but an important question is whether the protein resides always in a dimeric configuration in the plasma membrane or whether monomers of the protein are also present in its native state within in the intact plasma membrane. We have determined the stoichiometry of the human (h)TMEM16A within whole COS-7 cells in liquid. For the purpose of detecting TMEM16A subunits, single proteins were tagged by the streptavidin-binding peptide within extracellular loops accessible by streptavidin coated quantum dot (QD) nanoparticles. The labeled proteins were then imaged using correlative light microscopy and environmental scanning electron microscopy (ESEM) using scanning transmission electron microscopy (STEM) detection. The locations of 19,583 individual proteins were determined of which a statistical analysis using the pair correlation function revealed the presence of a dimeric conformation of the protein. The amounts of detected label pairs and single labels were compared between experiments in which the TMEM16A SBP-tag position was varied, and experiments in which tagged and non-tagged TMEM16A proteins were present. It followed that hTMEM16A resides in the plasma membrane as dimer only and is not present as monomer. This strategy may help to elucidate the stoichiometry of other membrane protein species within the context of the intact plasma membrane in future. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Enhancement of absorption and resistance of motion utilizing a multi-channel opto-electronic sensor to effectively monitor physiological signs during sport exercise

    Science.gov (United States)

    Alzahrani, Abdullah; Hu, Sijung; Azorin-Peris, Vicente; Barrett, Laura; Esliger, Dale; Hayes, Matthew; Akbare, Shafique; Achart, Jérôme; Kuoch, Sylvain

    2015-03-01

    This study presents an effective engineering approach for human vital signs monitoring as increasingly demanded by personal healthcare. The aim of this work is to study how to capture critical physiological parameters efficiently through a well-constructed electronic system and a robust multi-channel opto-electronic patch sensor (OEPS), together with a wireless communication. A unique design comprising multi-wavelength illumination sources and a rapid response photo sensor with a 3-axis accelerometer enables to recover pulsatile features, compensate motion and increase signal-to-noise ratio. An approved protocol with designated tests was implemented at Loughborough University a UK leader in sport and exercise assessment. The results of sport physiological effects were extracted from the datasets of physical movements, i.e. sitting, standing, waking, running and cycling. t-test, Bland-Altman and correlation analysis were applied to evaluate the performance of the OEPS system against Acti-Graph and Mio-Alpha.There was no difference in heart rate measured using OEPS and both Acti-Graph and Mio-Alpha (both p<0.05). Strong correlations were observed between HR measured from the OEPS and both the Acti-graph and Mio-Alpha (r = 0.96, p<0.001). Bland-Altman analysis for the Acti-Graph and OEPS found the bias 0.85 bpm, the standard deviation 9.20 bpm, and the limits of agreement (LOA) -17.18 bpm to +18.88 bpm for lower and upper limits of agreement respectively, for the Mio-Alpha and OEPS the bias is 1.63 bpm, standard deviation SD8.62 bpm, lower and upper limits of agreement, - 15.27 bpm and +18.58 bpm respectively. The OEPS demonstrates a real time, robust and remote monitoring of cardiovascular function.

  14. Soft electronic structure modulation of surface (thin-film) and bulk (ceramics) morphologies of TiO{sub 2}-host by Pb-implantation: XPS-and-DFT characterization

    Energy Technology Data Exchange (ETDEWEB)

    Zatsepin, D.A. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990 Yekaterinburg (Russian Federation); Institute of Physics and Technology, Ural Federal University, 620002 Yekaterinburg (Russian Federation); Boukhvalov, D.W., E-mail: danil@hanyang.ac.kr [Department of Chemistry, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Theoretical Physics and Applied Mathematics Department, Ural Federal University, Mira Street 19, 620002 Yekaterinburg (Russian Federation); Gavrilov, N.V. [Institute of Electrophysics, Russian Academy of Sciences, Ural Branch, 620990 Yekaterinburg (Russian Federation); Zatsepin, A.F. [Institute of Physics and Technology, Ural Federal University, 620002 Yekaterinburg (Russian Federation); Shur, V.Ya.; Esin, A.A. [Institute of Natural Sciences, Ural Federal University, 51 Lenin Ave, 620000 Yekaterinburg (Russian Federation); Kim, S.S. [School of Materials Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of); Kurmaev, E.Z. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990 Yekaterinburg (Russian Federation); Institute of Physics and Technology, Ural Federal University, 620002 Yekaterinburg (Russian Federation)

    2017-04-01

    Highlights: • Experiment and theory demonstrate significant difference between patterns of Pb-ion implantation in TiO{sub 2}. • In bulk TiO{sub 2} Pb-impurities leads formation of PbO phase. • On the surface of TiO{sub 2}:Pb occur formation of PbxOy configurations. • In both bulk and surface TiO{sub 2}:Pb occur decreasing of the bandgap by shift of valence band about 1 eV up. - Abstract: The results of combined experimental and theoretical study of substitutional and clustering effects in the structure of Pb-doped TiO{sub 2}-hosts (bulk ceramics and thin-film morphologies) are presented. Pb-doping of the bulk and thin-film titanium dioxide was made with the help of pulsed ion-implantation without posterior tempering (Electronic Structure Modulation Mode). The X-ray photoelectron spectroscopy (XPS) qualification of core-levels and valence bands and Density-Functional Theory (DFT) calculations were employed in order to study the yielded electronic structure of Pb-ion modulated TiO{sub 2} host-matrices. The combined XPS-and-DFT analysis has agreed definitely with the scenario of the implantation stimulated appearance of PbO-like structures in the bulk morphology of TiO{sub 2}:Pb, whereas in thin-film morphology the PbO{sub 2}-like structure becomes dominating, essentially contributing weak O/Pb bonding (Pb{sub x}O{sub y} defect clusters). The crucial role of the oxygen hollow-type vacancies for the process of Pb-impurity “insertion” into the structure of bulk TiO{sub 2} was pointed out employing DFT-based theoretical background. Both experiment and theory established clearly the final electronic structure re-arrangement of the bulk and thin-film morphologies of TiO{sub 2} because of the Pb-modulated deformation and shift of the initial Valence Base-Band Width about 1 eV up.

  15. Radiopaque Strontium Fluoroapatite Glass-Ceramics.

    Science.gov (United States)

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2-Al2O3-Y2O3-SrO-Na2O-K2O/Rb2O/Cs2O-P2O5-F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F - leucite, KAlSi2O6, (b) Sr5(PO4)3F - leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F - pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F - Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite - pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These

  16. Radiopaque Strontium Fluoroapatite Glass-Ceramics

    Science.gov (United States)

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2–Al2O3–Y2O3–SrO–Na2O–K2O/Rb2O/Cs2O–P2O5–F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F – leucite, KAlSi2O6, (b) Sr5(PO4)3F – leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F – pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal

  17. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana

    2003-08-07

    In the present quarter, experiments are presented on ceramic/metal interactions of Zirconia/ Ni-B-Si system and with a thin Ti coating deposited on zirconia surface. Existing facilities were modified for evaluation of environmental assisted slow crack growth and creep in flexural mode. Processing of perovskites of LSC, LSF and LSCF composition were continued for evaluation of mechanical properties as a function of environment. These studies in parallel to those on the LSFCO composition is expect to yield important information on questions such as the role of cation segregation and the stability of the perovskite structure on crack initiation vs. crack growth. Studies have been continued on the La{sub 1-x}Sr{sub x}FeO{sub 3-d} composition using neutron diffraction and TGA studies. A transition from p-type to n-type of conductor was observed at relative low pO{sub 2}, at which the majority carriers changed from the holes to electrons because of the valence state decreases in Fe due to the further loss of oxygen. Investigation on the thermodynamic properties of the membrane materials are continued to develop a complete model for the membrane transport. Data obtained at 850 C show that the stoichiometry in La{sub 0.2}Sr{sub 0.8}Fe{sub 0.8}Cr{sub 0.2}O{sub 3-x} vary from {approx}2.85 to 2.6 over the pressure range studied. From the stoichiometry a lower limit of 2.6 corresponding to the reduction of all Fe{sup 4+} to Fe{sup 3+} and no reduction of Cr{sup 3+} is expected.

  18. Ceramic catalyst materials

    Energy Technology Data Exchange (ETDEWEB)

    Sault, A.G.; Gardner, T.J. [Sandia National Laboratories, Albuquerque, NM (United States); Hanprasopwattanna, A.; Reardon, J.; Datye, A.K. [Univ. of New Mexico, Albuquerque, NM (United States)

    1995-08-01

    Hydrous titanium oxide (HTO) ion-exchange materials show great potential as ceramic catalyst supports due to an inherently high ion-exchange capacity which allows facile loading of catalytically active transition metal ions, and an ability to be cast as thin films on virtually any substrate. By coating titania and HTO materials onto inexpensive, high surface area substrates such as silica and alumina, the economics of using these materials is greatly improved, particularly for the HTO materials, which are substantially more expensive in the bulk form than other oxide supports. In addition, the development of thin film forms of these materials allows the catalytic and mechanical properties of the final catalyst formulation to be separately engineered. In order to fully realize the potential of thin film forms of titania and HTO, improved methods for the deposition and characterization of titania and HTO films on high surface area substrates are being developed. By varying deposition procedures, titania film thickness and substrate coverage can be varied from the submonolayer range to multilayer thicknesses on both silica and alumina. HTO films can also be formed, but the quality and reproducibility of these films is not nearly as good as for pure titania films. The films are characterized using a combination of isopropanol dehydration rate measurements, point of zero charge (PZC) measurements, BET surface area, transmission electron microscopy (TEM), and elemental analysis. In order to assess the effects of changes in film morphology on catalytic activity, the films are being loaded with MoO{sub 3} using either incipient wetness impregnation or ion-exchange of heptamolybdate anions followed by calcining. The MoO{sub 3} is then sulfided to form MOS{sub 2}, and tested for catalytic activity using pyrene hydrogenation and dibenzothiophene (DBT) desulfurization, model reactions that simulate reactions occurring during coal liquefaction.

  19. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contracts

    Energy Technology Data Exchange (ETDEWEB)

    Sliney, H.E.; Dellacorte, C. [NASA Lewis Research Center, Cleveland, OH (United States)

    1994-07-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel-based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900{degrees}C (in a few cases to 1200{degrees}C) were measured for a hemispherically-tipped pin on a flat sliding contract geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal. 12 refs., 6 figs., 1 tab.

  20. Measurement of the production cross section for W + γ in the electron channel in √s = 1.8 TeV $\\bar{p}$p collisions

    Energy Technology Data Exchange (ETDEWEB)

    Benjamin, Douglas P. [Tufts Univ., Medford, MA (United States)

    1993-11-01

    The production cross section times decay branching ratio for W+ γ in the electron decay channel in √s = 1.8 TeV $\\bar{p}$-p collisions has been measured using W → eγ data sample obtained from the CDF 1988--1989 Tevatron collider run. For photons in the central region ($\\bar{η}$$\\bar{γ}$ < 1.1) of the CDF detector with transverse energies E$T\\atop{γ}$ 5.0 GeV and lepton-photon angular separation ΔRℓγ > 0.7, eight electron Wγ candidates were observed. From these events, the production cross section times decay branching ratio for the electron sample was measured to be a σ • B(Wγ)exp = 17.0$+13.6\\atop{-13.4}$(stat. + syst.)pb. The Wγ cross section is sensitive to the anomalous couplings of the W boson. Using the Wγ cross section measurement, the absence of an excess of large ET photons accompanying the production of a W boson enables one to obtain direct limits on anomalous WWγ couplings. The experimental limits on the anomalous couplings was measured to be -7.2 < Δκ < +7.7 (λ = 0) and -3.5 < λ < +3.4 (Δκ = 0) at 95% CL. These experimental limits impose contraints on possible internal structure of the W boson with compositeness scale sensitivity ΛW ≥ 1 TeV for saturation of unitarity, corresponding to probing a distance scale of order LW ≤ 2.0 x 10-4 fm. The experimental limits on anomalous WWγ couplings place bounds on the higher-order electromagnetic moments of the W boson -- the magnetic dipole and electric quadrupole moments and the W boson mean-squared charge radius. The experimental results presented in this thesis are in good agreement with Standard Model expectations.

  1. Three-year clinical evaluation of two ceramic crown systems: a preliminary study.

    Science.gov (United States)

    Etman, Maged K; Woolford, M J

    2010-02-01

    The clinical performance and failure mechanisms of recently introduced ceramic crown systems used to restore posterior teeth have not been adequately examined. The purpose of this prospective clinical study was to evaluate and compare the clinical performance of 2 new ceramic crown systems with that of metal ceramic crowns using modified United States Public Health Services (USPHS) criteria. Ninety posterior teeth requiring crown restorations in 48 patients were randomized into 3 equal groups (n=30) for which different crown systems were used: an experimental hot-pressed glass ceramic based on a modified lithium disilicate ceramic (IPS e.max Press), an alumina-coping-based ceramic (Procera AllCeram), and a metal ceramic (Simidur S 2 veneered with IPS Classic Porcelain). The crowns were assessed over 3 years using the modified USPHS criteria. Crowns that developed visible cracks were sectioned and removed, and the surfaces were analyzed using a scanning electron microscope (SEM). The data were analyzed using the Kruskal-Wallis nonparametric statistical test, followed by the Mann-Whitney test with Bonferroni correction (alpha=.05). USPHS evaluation showed that the IPS e.max Press and metal ceramic crowns experienced fewer clinical changes than Procera AllCeram. Visible roughness, wear, and deformity were noticed in occlusal contact areas of Procera AllCeram crowns. SEM images showed well defined wear facets in both ceramic crown systems. Kruskal-Wallis tests showed a significant difference (Pcrown systems. Mann-Whitney tests showed significant differences among groups. IPS e.max Press crowns demonstrated clinical behavior comparable to Procera AllCeram and metal ceramic crowns, but the wear resistance of this crown type was superior to the Procera AllCeram crowns, according to modified USPHS criteria.

  2. Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

    Science.gov (United States)

    Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

    2014-01-01

    The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

  3. Processing and Characterization of Multiphase Ceramic Composites

    Science.gov (United States)

    Men, Danju

    Multiphase ceramic composites structure design has advantages for many applications. It is not only an effective way of limiting grain growth which allows for fine-grain size superplasticity at elevated temperatures, but also a combination of various desirable properties can be obtained from different phases, which otherwise cannot be found in one single phase material. The goal of this research is to select, design and optimize multiphase ceramic systems for mainly two purposes: shape forming and inert matrix nuclear fuel. These ceramic composites feature the machinability of monazite (LaPO 4) due to weak interfacial bonding with other oxides, the superplasticity of 3 mol% tetragonal zirconia (3Y-TZP), and the high hardness and strength of Al2O3 and MgAl2O4. These materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical behavior at room temperature was characterized for the elastic modulus, hardness and fracture toughness. They were fabricated and demonstrated to have deformation rates in the superplastic range of at high temperatures and easy machinability at room temperature using conventional tools. An issue with conventional nuclear fuel, UO2, is its very low thermal conductivity that causes high central temperatures, which can lead to melting and cracking during reactor operation. The solution can be found in multiphase ceramic composites, by combining nuclear fuel particles in a heat conducting phase with high thermal conductivity and other phases that absorb fission byproducts while maintaining good radiation stability. In the current research, proposed multiphase ceramic composite materials were designed and radiation damage was characterized by scanning and transmission electron microscopy (TEM). Gold irradiation was used to represent the primary knock-on atoms damage caused by neutrons. Xenon irradiation was used to represent the fission product damage. Magnetoplumbite, was the most susceptible to

  4. Testing method for ceramic armour and bare ceramic tiles

    NARCIS (Netherlands)

    Carton, E.P.; Roebroeks, G.H.J.J.

    2016-01-01

    TNO developed an alternative, more configuration independent ceramic test method than the Depth-of-Penetration test method. In this alternative test ceramic tiles and ceramic based armour are evaluated as target without a semi-infinite backing layer. An energy approach is chosen to evaluate and rank

  5. Testing method for ceramic armor and bare ceramic tiles

    NARCIS (Netherlands)

    Carton, E.P.; Roebroeks, G.H.J.J.

    2014-01-01

    TNO has developed an alternative, more configuration independent ceramic test method than the standard Depth-of-Penetration test method. In this test ceramic tiles and ceramic based armor are evaluated as target without a semi-infinite backing layer. An energy approach is chosen to evaluate and rank

  6. Plasma Synthesis and Sintering of Advanced Ceramics

    Science.gov (United States)

    1990-09-15

    glow discharge, corona discharge, RF or microwave discharge, etc.) and the electron concentration in the plasma are important. The efficiency of... corona discharge, and the low pressure capacitively or inductively coupled RF discharge. It is probable that a low pressure microwave discharge would also...Rhodes, "Agglomerate and Particle Size Effects on Sintering Yttria- Stabilized Zirconia ", J. Am. Ceram. Soc., 64 [1] 19-22 (1981). 4. T. S. Yeh and M

  7. Cooled Ceramic Turbine Vane Project

    Data.gov (United States)

    National Aeronautics and Space Administration — N&R Engineering will investigate the feasibility of cooled ceramics, such as ceramic matrix composite (CMC) turbine blade concepts that can decrease specific...

  8. Mechanical properties of ceramics

    CERN Document Server

    Pelleg, Joshua

    2014-01-01

    This book discusses the mechanical properties of ceramics and aims to provide both a solid background for undergraduate students, as well as serving as a text to bring practicing engineers up to date with the latest developments in this topic so they can use and apply these to their actual engineering work.  Generally, ceramics are made by moistening a mixture of clays, casting it into desired shapes and then firing it to a high temperature, a process known as 'vitrification'. The relatively late development of metallurgy was contingent on the availability of ceramics and the know-how to mold them into the appropriate forms. Because of the characteristics of ceramics, they offer great advantages over metals in specific applications in which hardness, wear resistance and chemical stability at high temperatures are essential. Clearly, modern ceramics manufacturing has come a long way from the early clay-processing fabrication method, and the last two decades have seen the development of sophisticated technique...

  9. Diffusion in ceramics

    CERN Document Server

    Pelleg, Joshua

    2016-01-01

    This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...

  10. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  11. The radiolysis of lithium oxide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Tiliks, J.; Supe, A.; Kizane, G.; Tiliks, J. Jr. [Latvia Univ., Riga (Latvia). Dept. of Chemistry; Grishmanov, V.; Tanaka, S.

    1998-03-01

    The radiolysis of Li{sub 2}O ceramics exposed to accelerated electrons (5 MeV) at 380 K was studied in the range of high absorbed doses up to 250 MGy. The formation of radiation defects (RD) and radiolysis products (RP) was demonstrated to occur simultaneously in the regions of (1) the regular crystalline lattice and (2) an enhanced content of the intrinsic defects and impurities. The production of the electronic RD and RP is more efficient in the region of the defected lattice than that at the site of the regular crystalline lattice. However, the stability of RD and RP formed in the region of the intrinsic defects is far less than those produced at the crystalline lattice, since most of the first mentioned RD and RP disappears with irradiation dose due to the radiation stimulated recombination. By this means the enhanced quantity of RD and RP is localized in the Li{sub 2}O ceramics irradiated to absorbed dose of 40-50 MGy, and hence this can influence the tritium release parameters. As soon as the intrinsic defects have been consumed in the production of RD and RP and the recombination of unstable electronic RD and RP takes place (at dose of {approx}100 MGy), the radiolysis of Li{sub 2}O ceramics occurs only at the crystalline lattice. Furthermore, the concentration of RD and RP increases monotonically and tends to the steady-state level. (author)

  12. Novel, Ceramic Membrane System For Hydrogen Separation

    Energy Technology Data Exchange (ETDEWEB)

    Elangovan, S.

    2012-12-31

    Separation of hydrogen from coal gas represents one of the most promising ways to produce alternative sources of fuel. Ceramatec, teamed with CoorsTek and Sandia National Laboratories has developed materials technology for a pressure driven, high temperature proton-electron mixed conducting membrane system to remove hydrogen from the syngas. This system separates high purity hydrogen and isolates high pressure CO{sub 2} as the retentate, which is amenable to low cost capture and transport to storage sites. The team demonstrated a highly efficient, pressure-driven hydrogen separation membrane to generate high purity hydrogen from syngas using a novel ceramic-ceramic composite membrane. Recognizing the benefits and limitations of present membrane systems, the all-ceramic system has been developed to address the key technical challenges related to materials performance under actual operating conditions, while retaining the advantages of thermal and process compatibility offered by the ceramic membranes. The feasibility of the concept has already been demonstrated at Ceramatec. This project developed advanced materials composition for potential integration with water gas shift rectors to maximize the hydrogenproduction.

  13. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  14. Colloidal forming of metal/ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Herencia, A.J.; Gutierrez, C.A.; Millan, A.J.; Nieto, M.I.; Moreno, R. [Inst. de Ceramica y Vidrio, Madrid (Spain)

    2002-07-01

    Metal/Ceramic composites have very attractive properties as either structural or electronic materials. For certain applications, complex microstructures and shapes are required. Colloidal processing of ceramics has proved to provide better properties and allows to obtain near net complex shaped parts. However colloidal processing has not received a similar attention in powder metallurgy. This work deals with the colloidal approach to the forming of metallic and metal/ceramic composites in an aqueous medium. Rheological behavior of concentrated pure nickel, nickel/alumina and nickel/zirconia suspensions is studied and optimized for obtaining flat surfaces or near net shaped parts by tape casting and gel casting respectively. In each case the influence of the processing additives (acrylic binders for tape casting and carrageenans for gel casting) on the rheological behavior of the slurries is determined. Pure nickel and nickel/ceramic composites with different compositions have been prepared. Static and dynamic sintering studies were performed at different conditions in order to control the porosity and microstructure of the final bodies, which were characterized by optical microscopy. (orig.)

  15. High flow ceramic pot filters

    NARCIS (Netherlands)

    van Halem, D.; van der Laan, H.; Soppe, A. I.A.; Heijman, S.G.J.

    2017-01-01

    Ceramic pot filters are considered safe, robust and appropriate technologies, but there is a general consensus that water revenues are limited due to clogging of the ceramic element. The objective of this study was to investigate the potential of high flow ceramic pot filters to produce more

  16. A study on the geometry of dislocation patterns in the surrounding of nanoindents in a TWIP steel using electron channeling contrast imaging and discrete dislocation dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J.-I.; Zaefferer, S., E-mail: s.zaefferer@mpie.de; Raabe, D.

    2015-06-11

    Electron channeling contrast imaging under controlled diffraction conditions (cECCI) enables observation of crystal defects, especially dislocations, stacking faults and nano-twins, close to the surface of bulk samples. In this work cECCI has been employed to observe defects around nanoindents into the surface of {100}-, {110}-, {111}-oriented grains in a Fe–22Mn–0.65C (wt%) TWIP steel sample (fcc crystal structure, stacking fault energy ~20 mJ/m²) using a cone-spherical indenter. The dislocation patterns show four- and two-fold symmetries for the {100}- and {110}-orientation, and a three-fold symmetry for the {111}-orientation which is, however, difficult to observe. Discrete dislocation dynamics (DDD) simulations of the indentation were carried out to complement the static experimental investigations. The simulations were carried out with both, cross-slip disabled and enabled conditions, where the former were found to match to the experimental results better, as may be expected for an fcc material with low stacking fault energy. The 3-dimensional geometry of the dislocation patterns of the different indents was analysed and discussed with respect to pattern formation mechanisms. The force–displacement curves obtained during indentation showed a stronger strain hardening for the {111} oriented crystal than that for the other orientations. This is in contrast to the behaviour of, for example, copper and is interpreted to be due to planar slip. Irrespective of orientation and indentation depth the radius of the plastically deformed area was found to be approximately 4 times larger than that of the indenter contact area.

  17. Verification of Ceramic Structures

    Science.gov (United States)

    Behar-Lafenetre, Stephanie; Cornillon, Laurence; Rancurel, Michael; De Graaf, Dennis; Hartmann, Peter; Coe, Graham; Laine, Benoit

    2012-07-01

    In the framework of the “Mechanical Design and Verification Methodologies for Ceramic Structures” contract [1] awarded by ESA, Thales Alenia Space has investigated literature and practices in affiliated industries to propose a methodological guideline for verification of ceramic spacecraft and instrument structures. It has been written in order to be applicable to most types of ceramic or glass-ceramic materials - typically Cesic®, HBCesic®, Silicon Nitride, Silicon Carbide and ZERODUR®. The proposed guideline describes the activities to be performed at material level in order to cover all the specific aspects of ceramics (Weibull distribution, brittle behaviour, sub-critical crack growth). Elementary tests and their post-processing methods are described, and recommendations for optimization of the test plan are given in order to have a consistent database. The application of this method is shown on an example in a dedicated article [7]. Then the verification activities to be performed at system level are described. This includes classical verification activities based on relevant standard (ECSS Verification [4]), plus specific analytical, testing and inspection features. The analysis methodology takes into account the specific behaviour of ceramic materials, especially the statistical distribution of failures (Weibull) and the method to transfer it from elementary data to a full-scale structure. The demonstration of the efficiency of this method is described in a dedicated article [8]. The verification is completed by classical full-scale testing activities. Indications about proof testing, case of use and implementation are given and specific inspection and protection measures are described. These additional activities are necessary to ensure the required reliability. The aim of the guideline is to describe how to reach the same reliability level as for structures made of more classical materials (metals, composites).

  18. Investigation of Locally Made Ceramic Filter for Household Water Treatment

    Directory of Open Access Journals (Sweden)

    Awaluddin Nurmiyanto

    2012-06-01

    Full Text Available This research have objective to develop and evaluate the performance of ceramic filter in using locally available material at Yogyakarta. Ceramic filter are made by pressing a mixture of clay, discarded pottery (grog and combustible material (coconut fiber into the molder. Curving processes are then applied to form tubular shape before firing it using kiln (1005°C. Filtration test were performed gravitationally by flowing well water into ceramic filter. Filtered water quality was complying with Indonesia drinking water quality standard (E.Coli and turbidity although it has low filtration rate (0,461 L/Hr. The most optimum ceramic filter in turbidity and bacterial removal was composition number 10 {clay+coconut fiber 4,5%(w/w+grog 5%(w/w} that have average turbidity removal 88,2%, and average E. Coli removal 100%. N2 adsorption-desorption result on ceramic filter number 10 showed 0,04μm pore size, and 4,32m2/g pore surface area. The result from the XRD (X-ray diffractometer indicates crystal structure of calcite and quartz on ceramic filter surface. Energy Dispersive X-ray (EDX analysis showed Carbon compound as the most material constituent within the filter. Whereas micro’s photo using SEM (scanning electron microscopic and TEM (transmitted electron microscopic showed filter surface consists of stacked aggregates, separated by more randomly oriented particles.

  19. Supported microporous ceramic membranes

    Science.gov (United States)

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

    A method for permformation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms.

  20. Friction and Wear Behavior of Selected Dental Ceramics

    Science.gov (United States)

    Park, Jongee; Pekkan, Gurel; Ozturk, Abdullah

    The purpose of this study was to determine the friction coefficients and wear rates of six commercially available dental ceramics including IPS Empress 2 (E2), Cergo Pressable Ceramic (CPC), Cercon Ceram (CCS) and Super porcelain EX-3 (SPE). Bovine enamel (BE) was also tested as a reference material for comparison purposes. Samples of the dental ceramics were prepared according to the instructions described by the manufacturers in disk-shape with nominal dimensions of 12 mm × 2 mm. The wear tests were performed by means of a pin-on-disk type tribometer. The friction coefficients and specific wear rates of the materials were determined at a load of 10 N and rotating speed of 0.25 cm/s without lubrication. Surface morphology of the wear tracks was examined using a scanning electron microscope. Statistical analyses were made using one-way ANOVA and Turkey's HSD (P < 0.05).

  1. In-process EDM truing to generate complex contours on metal-bond, superabrasive grinding wheels for precision grinding structural ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Piscotty, M.A.; Davis, P.J.; Saito, T.T.; Blaedel, K.L.; Griffith, L.

    1997-08-01

    The demand and use of precision grinding of structural ceramics continue to increase as the worldwide advanced ceramic industry surpasses $20 billion is sales. Included in this industry are engineering structural ceramics, electronic ceramics, bioceramics and others. These materials are used in applications such as engine components, casting and extrusion dies, bearings, medical implants, nozzles, thermal insulators, and more. Along with the variety of ceramic applications comes a broad range of precision requirements, which in turn leads to various required processes to accommodate a spectrum of specifications. A process for grinding ceramic components to micrometer tolerances was employed and further developed at Lawrence Livermore National Laboratory for two separate grinding projects.

  2. Tick-proof ceramics. Bo dani ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Shimono, F. (Ishizuka Glass Co. Ltd., Nagoya (Japan))

    1993-07-01

    Ishizuka Glass has developed SiO2-B2O3-R2O(RO) based tick-proof ceramics (trade name; Segrocera) in cooperation with Yamato Chemical Industry, insecticide maker. This article is a report on effectiveness of this ceramics. Ticks living indoors are roughly divided into two kinds, namely ticks living in a house itself and ticks which enter the house by parasitizing on animals and plants, and Segrocera has been developed aiming at the former ticks which, irrespective of its kind, need the temperature of 20-30[degree]C and the moisture of 60% or more as its breeding conditions. The tick-proof effect of Segrocera is as excellent as 90-99% and even after keeping its specimen at 75RH for 12 months, it has shown the ratio of inhibiting ticks' breeding of 98-99%. In comparison with that the effect of other tick-proof agent, pyrethroids-based aerosol is limited up to 24 hours, it is the feature of Segrocera that its life is considerably longer. Safety of Segrocera is also very high. 2 refs., 1 fig., 7 tabs.

  3. Transformation Toughening of Ceramics

    Science.gov (United States)

    1992-03-01

    chanical twing of ualaneeting Ceramica at High Temperatures. ILondo, Patigue-crack growth in overaged and partially stabi- U.K., 198.""IS. Itoribe... Ceramica " Chapter 18 In Mechanical Prop- ŗR. M. !AcMeeding and A. 0. Evans, ’Mechanics of Transformation ertles of Engineering Ceramics. Edited by W.W

  4. Microporous alumina ceramic membranes

    Science.gov (United States)

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  5. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendfra Nagabhushana

    2001-07-01

    The mechanical properties of model systems were analyzed. A reasonably accurate finite element model was implemented and a rational metric to predict the strength of ceramic/metal concentrical joints was developed. The mode of failure of the ceramic/metal joints was determined and the importance of the mechanical properties of the braze material was assessed. Thermal cycling experiments were performed on the model systems and the results were discussed. Additionally, experiments using the concept of placing diffusion barriers on the ceramic surface to limit the extent of the reaction with the braze were performed. It was also observed that the nature and morphology of the reaction zone depends greatly on the nature of the perovskite structure being used. From the experiments, it is observed that the presence of Cr in the Fe-occupied sites decreases the tendency of Fe to segregate and to precipitate out of the lattice. In these new experiments, Ni was observed to play a major role in the decomposition of the ceramic substrate.

  6. Influence of surface treatment on bond strength of veneering ceramics fused to zirconia.

    Science.gov (United States)

    Tada, Kouki; Sato, Toru; Yoshinari, Masao

    2012-01-01

    In all-ceramic restorations involving a zirconia framework, surface treatment of the zirconia surface is required to enhance bonding strength with the veneering ceramics and thus prevent chipping. The purpose of the present study was to investigate the influence of surface roughness and heat treatment of the zirconia and use of liner porcelain on bond strength between veneering ceramics and a zirconia framework. Debonding/crack-initiation strength (τb) was determined according to ISO 9693. No significant difference was observed among conditions, except with use of a liner under heat treatment, which yielded a τb of 26.0±2.9-28.9±1.7 MPa. Electron probe microanalysis revealed that components of the veneering ceramics remained on the zirconia surface after debonding, suggesting that fractures occur in the veneering ceramics and that improving the strength of the veneering ceramics themselves might increase bond strength.

  7. Ceramic Laser Materials

    Energy Technology Data Exchange (ETDEWEB)

    Soules, T F; Clapsaddle, B J; Landingham, R L; Schaffers, K I

    2005-02-15

    Transparent ceramic materials have several major advantages over single crystals in laser applications, not the least of which is the ability to make large aperture parts in a robust manufacturing process. After more than a decade of working on making transparent YAG:Nd, Japanese workers have recently succeeded in demonstrating samples that performed as laser gain media as well as their single crystal counterparts. Since then several laser materials have been made and evaluated. For these reasons, developing ceramic laser materials is the most exciting and futuristic materials topic in today's major solid-state laser conferences. We have established a good working relationship with Konoshima Ltd., the Japanese producer of the best ceramic laser materials, and have procured and evaluated slabs designed by us for use in our high-powered SSHCL. Our measurements indicate that these materials will work in the SSHCL, and we have nearly completed retrofitting the SSHCL with four of the largest transparent ceramic YAG:Nd slabs in existence. We have also begun our own effort to make this material and have produced samples with various degrees of transparency/translucency. We are in the process of carrying out an extensive design-of-experiments to establish the significant process variables for making transparent YAG. Finally because transparent ceramics afford much greater flexibility in the design of lasers, we have been exploring the potential for much larger apertures, new materials, for example for the Mercury laser, other designs for SSHL, such as, edge pumping designs, slabs with built in ASE suppression, etc. This work has just beginning.

  8. Ceramic tubesheet design analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mallett, R.H.; Swindeman, R.W.

    1996-06-01

    A transport combustor is being commissioned at the Southern Services facility in Wilsonville, Alabama to provide a gaseous product for the assessment of hot-gas filtering systems. One of the barrier filters incorporates a ceramic tubesheet to support candle filters. The ceramic tubesheet, designed and manufactured by Industrial Filter and Pump Manufacturing Company (EF&PM), is unique and offers distinct advantages over metallic systems in terms of density, resistance to corrosion, and resistance to creep at operating temperatures above 815{degrees}C (1500{degrees}F). Nevertheless, the operational requirements of the ceramic tubesheet are severe. The tubesheet is almost 1.5 m in (55 in.) in diameter, has many penetrations, and must support the weight of the ceramic filters, coal ash accumulation, and a pressure drop (one atmosphere). Further, thermal stresses related to steady state and transient conditions will occur. To gain a better understanding of the structural performance limitations, a contract was placed with Mallett Technology, Inc. to perform a thermal and structural analysis of the tubesheet design. The design analysis specification and a preliminary design analysis were completed in the early part of 1995. The analyses indicated that modifications to the design were necessary to reduce thermal stress, and it was necessary to complete the redesign before the final thermal/mechanical analysis could be undertaken. The preliminary analysis identified the need to confirm that the physical and mechanical properties data used in the design were representative of the material in the tubesheet. Subsequently, few exploratory tests were performed at ORNL to evaluate the ceramic structural material.

  9. Synthesis of biomorphaus SiC-ceramics

    Directory of Open Access Journals (Sweden)

    Egelja Adela D.

    2007-01-01

    Full Text Available The carbothermal reduction processing of partially mineralized fir (Abies alba samples was used to obtain highly-porous SiC ceramics with cellular structure. The infiltration of TEOS (tetraetilortosilikat, Si(OC2H54 as a silica source, was conducted in order to carry out the mineralization process. Synthesis of the SiC was achieved with a C/SiO2 replica annealing at 1723 K in Ar atmosphere. The obtained samples were characterized using X-ray photoelectron spectroscopy (XPS, scanning electron microscopy (SEM and energy dispersive spectrometry (EDS. The experimental results revealed that the hierarchical bimorphous wood structure was preserved even after high-temperature treatment. Microstructural characterization of the ceramics revealed the presence of the P-SiC phase and traces of the a-SiC phase.

  10. Ceramic-on-ceramic total hip arthroplasty early dislocation rate.

    Science.gov (United States)

    Colwell, Clifford W; Hozack, William J; Mesko, J Wesley; D'Antonio, James A; Bierbaum, Benjamin E; Capello, William N; Jaffe, William L; Mai, Kenny T

    2007-12-01

    Wear debris from metal-on-polyethylene articulation in conventional total hip arthroplasty can limit the implant's longevity. Modern ceramic material with high wear resistance and low fracture risk has the potential to extend the lifetime of total hip arthroplasty, which makes the procedure potentially more suitable for young, active patients. Concerns with brittle ceramic material include fracture risk, the "squeak" phenomenon, and potentially a higher dislocation rate secondary to limited neck lengths and liner options. We therefore determined the early dislocation rate in modern ceramic-on-ceramic total hip arthroplasty. In 1635 total hip arthroplasties performed over the 9-year period (1996-2005), we observed three anterior and 15 posterior dislocations (1.1%). All were treated successfully, one with a revision and 17 with closed reduction under general anesthesia. Ceramic-on-ceramic total hip arthroplasty can be a good alternative bearing surface with a low dislocation rate.

  11. Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

    Science.gov (United States)

    Inokoshi, M; Yoshihara, K; Nagaoka, N; Nakanishi, M; De Munck, J; Minakuchi, S; Vanmeensel, K; Zhang, F; Yoshida, Y; Vleugels, J; Naert, I; Van Meerbeek, B

    2016-01-01

    The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical

  12. Luminescence properties of Eu3+-doped SiO2-LiYF4 glass-ceramic microrods

    Science.gov (United States)

    Secu, C. E.; Secu, M.

    2015-09-01

    Photoluminescence properties of the glass-ceramics microrods containing Eu3+-doped LiYF4 nanocrystals have been studied and characterized. Judd-Ofelt parameters and quantum efficiency has been computed from luminescence spectra and discussed by comparison to the glass ceramic bulk and pellet. The radiative decay rate Arad is higher in the glass ceramic rods (221 s-1) than in the glass ceramic bulk (130 s-1) but the quantum efficiency computed is very low (21%) compared to the glass-ceramic bulk (97%). There are effective non-radiative decay channels that might be related to an influence of the dimensional constraints imposed by the membrane pores during xerogel formation and subsequent glass ceramization.

  13. Grain boundaries in ceramics and ceramic-metal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, D.R.; Wolf, D.

    1986-01-01

    Three interfaces exist: the crystal-crystal grain boundary in very pure single-phase ceramics, the crystal-glass-crystal grain boundary in most single-phase and polyphase ceramics, and the ceramic-metal interface. It is needed to correlate their structure and adhesion/failure. Methods for studying the bonding, interfacial structure, and fracture and adhesion are discussed, and recommendations are given. 42 refs. (DLC)

  14. Ceramic/metal nanocomposites by lyophilization: Processing and HRTEM study

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez-Gonzalez, C.F. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo - UO - Principado de Asturias - PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain); Agouram, S. [Department of Applied Physics and Electromagnetism, Universitat de Valencia, 46100 Burjassot (Spain); Torrecillas, R. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo -UO - Principado de Asturias- PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain); Moya, J.S. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain); Lopez-Esteban, S., E-mail: s.lopez@cinn.es [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Consejo Superior de Investigaciones Cientificas - CSIC - Universidad de Oviedo - UO - Principado de Asturias - PA, Parque Tecnologico de Asturias, 33428 Llanera (Spain)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer A cryogenic route has been used to obtain ceramic/metal nanostructured powders. Black-Right-Pointing-Pointer The powders present good homogeneity and dispersion of metal. Black-Right-Pointing-Pointer The metal nanoparticle size distributions are centred in 17-35 nm. Black-Right-Pointing-Pointer Both phases, ceramic and metal, present a high degree of crystallinity. Black-Right-Pointing-Pointer Good metal/ceramic interfaces due to epitaxial growth, studied by HRTEM. -- Abstract: This work describes a wet-processing route based on spray-freezing and subsequent lyophilization designed to obtain nanostructured ceramic/metal powders. Starting from the ceramic powder and the corresponding metal salt, a water-based suspension is sprayed on liquid nitrogen. The frozen powders are subsequently freeze-dried, calcined and reduced. The material was analyzed using X-ray diffraction analysis at all stages. High resolution transmission electron microscopy studies showed a uniform distribution of metal nanoparticles on the ceramic grain surfaces, good interfaces and high crystallinity, with an average metal particle size in the nanometric range.

  15. Thermoluminescent analysis of archaeological ceramic from Teotenango, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez R, R. [Centro INAH Estado de Mexico, Morelos Ote. 502, Col. San Sebastian, 50090 Toluca, Estado de Mexico (Mexico); Mondragon, M. [Museo Roman Pina Chan, Teotenango 1024 (Mexico); Villa S, G.; Gonzalez M, P.R.; Mendoza A, D. [ININ, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2006-07-01

    Of all the kind of artifacts which may be found at archaeological sites, ceramics are surely among the most important. A ceramic material is highly durable, and virtually unchanged after hundred of years from its date of manufacture. Because of this, a ceramic will always be an important object for serious studies to determine which culture produced it, to date cultures, reconstruct economic patterns and social organization, and establish routes of trade or simply to classify the different types of ceramics. The aim of this paper was to perform a thermoluminescent analysis of archaeological ceramic samples belonging to Teotenango, Mexico. The analysis is complemented with a physicochemical characterization by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-Ray Diffraction (XRD). TL analysis shows some differences when the samples are exposed to ionizing radiation field, while SEM analysis shows a porous and granular structure in all samples, EDS analysis shows oxygen (O), aluminum (Al), silicon (Si), iron (Fe), sodium (Na), phosphorus (P), potassium (K) and calcium (Ca) in significant amounts. These results allow establishing differences among ceramic samples belonging to the same place. (Author)

  16. Ceramic hot-gas filter

    Science.gov (United States)

    Connolly, Elizabeth Sokolinski; Forsythe, George Daniel; Domanski, Daniel Matthew; Chambers, Jeffrey Allen; Rajendran, Govindasamy Paramasivam

    1999-01-01

    A ceramic hot-gas candle filter having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during backpulse cleaning and is resistant to chemical degradation at high temperatures.

  17. Phenomena and mechanisms of crack propagation in glass-ceramics.

    Science.gov (United States)

    Apel, E; Deubener, J; Bernard, A; Höland, M; Müller, R; Kappert, H; Rheinberger, V; Höland, W

    2008-10-01

    Lithium disilicate, leucite and apatite glass-ceramics have become state-of-the-art framework materials in the fabrication of all-ceramic dental restorative materials. The goal of this study was to examine the crack propagation behaviour of these three known glass-ceramic materials after they have been subjected to Vickers indentation and to characterize their crack opening profiles (delta(meas) vs. (a-r)). For this purpose, various methods of optical examination were employed. Optical microscopy investigations were performed to examine the crack phenomena at a macroscopic level, while high-resolution techniques, such as scanning electron microscopy (SEM) and atomic force microscopy (AFM), were employed to investigate the crack phenomena at a microscopic level. The crack patterns of the three glass-ceramics vary from fairly straightforward to more complex, depending on the amount of residual glass matrix present in the material. The high-strength lithium disilicate crystals feature a high degree of crosslinking, thereby preventing crack propagation. In this material, the crack propagates only through the residual glass phase, which constitutes 30%-40% by volume. Having a high glass content of more than 65% by volume, the leucite and apatite glass-ceramics show far more complex crack patterns. Cracks in the leucite glass-ceramic propagate through both the glass and crystal phase. The apatite glass-ceramic shows a similar crack behaviour as an inorganic-organic composite material containing nanoscale fillers, which are pulled out in the surroundings of the crack tip. The observed crack behaviour and the calculated K(tip) values of the three types of glass-ceramics were compared to the K(IC) values determined according to the SEVNB method.

  18. Seal between metal and ceramic conduits

    Energy Technology Data Exchange (ETDEWEB)

    Underwood, Richard Paul; Tentarelli, Stephen Clyde

    2015-02-03

    A seal between a ceramic conduit and a metal conduit of an ion transport membrane device consisting of a sealing surface of ceramic conduit, a sealing surface of ceramic conduit, a single gasket body, and a single compliant interlayer.

  19. Ceramic Composite Thin Films

    Science.gov (United States)

    Ruoff, Rodney S. (Inventor); Stankovich, Sasha (Inventor); Dikin, Dmitriy A. (Inventor); Nguyen, SonBinh T. (Inventor)

    2013-01-01

    A ceramic composite thin film or layer includes individual graphene oxide and/or electrically conductive graphene sheets dispersed in a ceramic (e.g. silica) matrix. The thin film or layer can be electrically conductive film or layer depending the amount of graphene sheets present. The composite films or layers are transparent, chemically inert and compatible with both glass and hydrophilic SiOx/silicon substrates. The composite film or layer can be produced by making a suspension of graphene oxide sheet fragments, introducing a silica-precursor or silica to the suspension to form a sol, depositing the sol on a substrate as thin film or layer, at least partially reducing the graphene oxide sheets to conductive graphene sheets, and thermally consolidating the thin film or layer to form a silica matrix in which the graphene oxide and/or graphene sheets are dispersed.

  20. Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

    Science.gov (United States)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

    Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

  1. A study of Channeling, Volume Reflection and Volume Capture of 3.35 - 14.0 GeV Electrons in a bent Silicon Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Wistisen, T. N. [Aarhus Univ. (Denmark); Uggerhoj, U. I. [Aarhus Univ. (Denmark); Wienands, U. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Markiewicz, T. W. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Noble, R. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Benson, B. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Smith, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Bagli, E. [Univ. of Ferrara (Italy); Bandiera, L. [Univ. of Ferrara (Italy); Germogli, G. [Univ. of Ferrara (Italy); Guidi, V. [Univ. of Ferrara (Italy); Mazzolari, A. [Univ. of Ferrara (Italy); Holtzapple, R. [California Polytechnic State Univ. (CalPoly), San Luis Obispo, CA (United States); Tucker, S. [California Polytechnic State Univ. (CalPoly), San Luis Obispo, CA (United States)

    2015-12-03

    We present the experimental data and analysis of experiments conducted at SLAC National Accelerator Laboratory investigating the processes of channeling, volume-reflection and volume-capture along the (111) plane in a strongly bent quasi-mosaic silicon crystal. Additionally, these phenomena were investigated at 5 energies: 3.35, 4.2, 6.3, 10.5 and 14.0 GeV with a crystal with bending radius of 0.15m, corresponding to curvatures of 0.070, 0.088, 0.13, 0.22 and 0.29 times the critical curvature respectively. We have extracted important parameters describing the channeling process such as the dechanneling length, the angle of volume reflection, the surface transmission and the widths of the distribution of channeled particles parallel and orthogonal to the plane.

  2. Development of Sesquioxide Ceramic for High Energy Lasers

    Science.gov (United States)

    2015-05-25

    Ceramic Matrix Composites , Ceramics ...important. 15. SUBJECT TERMS Laser Materials Processing, Ceramic Matrix Composites , Ceramics 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF... ceramic processing, optimizing the processing requires time and resources. Once the fabrication process is established, composition adjustment

  3. Tailored Ceramics for Laser Applications

    Energy Technology Data Exchange (ETDEWEB)

    Hollingsworth, Joel [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2007-12-10

    Transparent ceramics match or exceed the performance of single-crystal materials in laser applications, with a more-robust fabrication process. Controlling the distribution of optical dopants in transparent ceramics would allow qualitative improvements in amplifier slab design by allowing gain and loss to be varied within the material. My work aims to achieve a controlled pattern or gradient of dopant prior to sintering, in order to produce tailored ceramics.

  4. Radiation effects in nuclear materials: Role of nuclear and electronic energy losses and their synergy

    Energy Technology Data Exchange (ETDEWEB)

    Thomé, Lionel [Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, CNRS-IN2P3-Université Paris-Sud; Debelle, Aurelien [Universite Paris Sud, Orsay, France; Garrido, Frederico [Universite Paris Sud, Orsay, France; Mylonas, Stamatis [Universite Paris Sud, Orsay, France; Décamps, B. [Universite Paris Sud, Orsay, France; Bachelet, C. [Universite Paris Sud, Orsay, France; Sattonnay, G. [LEMHE/ICMMO, Université Paris-Sud, Bât. Orsay, France; Moll, Sandra [French Atomic Energy Commission (CEA), Centre de Saclay, Gif sur Yvette; Pellegrino, S. [French Atomic Energy Commission (CEA); Miro, S. [French Atomic Energy Commission (CEA); Trocellier, P. [French Atomic Energy Commission (CEA); Serruys, Y. [French Atomic Energy Commission (CEA); Velisa, G. [French Atomic Energy Commission (CEA); Grygiel, C. [CNRS, France; Monnet, I. [CIMAP, CEA-CNRS-Université de Caen, France; Toulemonde, Marcel [French Atomic Energy Commission (CEA), French National Centre for Scientific Research (CNRS)-ENSICAE; Simon, P. [CEMHTI, CNRS, France; Jagielski, Jacek [Institute for Electronic Materials Technology; Jozwik-Biala, Iwona [Institute for Electronic Materials Technology; Nowicki, Lech [Soltan Institute for Nuclear Studies, Swierk, Poland; Behar, M. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre,; Weber, William J [ORNL; Zhang, Yanwen [ORNL; Backman, Marie [University of Tennessee, Knoxville (UTK); Nordlund, Kai [University of Helsinki; Djurabekova, Flyura [University of Helsinki

    2013-01-01

    Ceramic oxides and carbides are promising matrices for the immobilization and/or transmutation of nuclear wastes, cladding materials for gas-cooled fission reactors and structural components for fusion reactors. For these applications there is a need of fundamental data concerning the behavior of nuclear ceramics upon irradiation. This article is focused on the presentation of a few remarkable examples regarding ion-beam modifications of nuclear ceramics with an emphasis on the mechanisms leading to damage creation and phase transformations. Results obtained by combining advanced techniques (Rutherford backscattering spectrometry and channeling, X-ray diffraction, transmission electron microscopy, Raman spectroscopy) concern irradiations in a broad energy range (from keV to GeV) with the aim of exploring both nuclear collision (Sn) and electronic excitation (Se) regimes. Finally, the daunting challenge of the demonstration of the existence of synergistic effects between Sn and Se is tackled by discussing the healing due to intense electronic energy deposition (SHIBIEC) and by reporting results recently obtained in dual-beam irradiation (DBI) experiments.

  5. Statistic><Ceramics

    DEFF Research Database (Denmark)

    Hansen, Flemming Tvede

    2008-01-01

    Co-organizer for and participant at the exhibition: Statistic><Ceramics The Röhsska Museum of Design and Decorative Arts; Gothenborg 5/2-16/3 2008 Museum fur Kunst und Gewerbe, Hamburg 3/4-27/4 2008......Co-organizer for and participant at the exhibition: Statistic>2-16/3 2008 Museum fur Kunst und Gewerbe, Hamburg 3/4-27/4 2008...

  6. A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor

    Science.gov (United States)

    Mao, Wei; She, Wei-Bo; Yang, Cui; Zhang, Chao; Zhang, Jin-Cheng; Ma, Xiao-Hua; Zhang, Jin-Feng; Liu, Hong-Xia; Yang, Lin-An; Zhang, Kai; Zhao, Sheng-Lei; Chen, Yong-He; Zheng, Xue-Feng; Hao, Yue

    2014-08-01

    In this paper, we present a two-dimensional (2D) fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor (FP-HEMT) on the basis of 2D Poisson's solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, AlGaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco—Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc.

  7. Ceramic stationary gas turbine

    Energy Technology Data Exchange (ETDEWEB)

    Roode, M. van [Solar Turbines Inc., San Diego, CA (United States)

    1995-10-01

    The performance of current industrial gas turbines is limited by the temperature and strength capabilities of the metallic structural materials in the engine hot section. Because of their superior high-temperature strength and durability, ceramics can be used as structural materials for hot section components (blades, nozzles, combustor liners) in innovative designs at increased turbine firing temperatures. The benefits include the ability to increase the turbine inlet temperature (TIT) to about 1200{degrees}C ({approx}2200{degrees}F) or more with uncooled ceramics. It has been projected that fully optimized stationary gas turbines would have a {approx}20 percent gain in thermal efficiency and {approx}40 percent gain in output power in simple cycle compared to all metal-engines with air-cooled components. Annual fuel savings in cogeneration in the U.S. would be on the order of 0.2 Quad by 2010. Emissions reductions to under 10 ppmv NO{sub x} are also forecast. This paper describes the progress on a three-phase, 6-year program sponsored by the U.S. Department of Energy, Office of Industrial Technologies, to achieve significant performance improvements and emissions reductions in stationary gas turbines by replacing metallic hot section components with ceramic parts. Progress is being reported for the period September 1, 1994, through September 30, 1995.

  8. Dental ceramics: a current review.

    Science.gov (United States)

    Lawson, Nathaniel C; Burgess, John O

    2014-03-01

    Ceramics are used for many dental applications and are characterized in various ways, including by their hardness, brittleness, thermal and electrical insulation, and biocompatibility. The ceramics most commonly used in dentistry are oxides, particularly silicon dioxide (SiO2), or silica; aluminum oxide (Al2O3), or alumina; and zirconium dioxide (ZrO2), or zirconia. This article reviews the microstructure of current dental ceramic materials and how it relates to their mechanical properties, clinical techniques, and optical properties. Typical ceramics currently in use are described, and their clinically relevant properties such as strength, fracture, polishability, and wear are compared. Cementation methods are also discussed.

  9. Microstructural properties of BaTiO{sub 3} ceramics and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fundora C, A.; Portelles, J.J.; Siqueiros, J.M. [Posgrado en Fisica de Materiales, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada. Apartado Postal 2861, 22800 Ensenada, Baja California (Mexico)

    2000-07-01

    A microstructural study of BaTiO{sub 3} ceramics obtained by the conventional ceramic method is presented. Targets were produced to grow BaTiO{sub 3} thin films by pulsed laser deposition on Pt/Ti/Si (100) substrates. X-ray diffraction, Auger Electron Spectroscopy, X-ray Photon Spectroscopy and Scanning Electron Microscopy were used to study the properties of the BaTiO{sub 3} ceramic samples and thin films, as deposited and after an annealing process. (Author)

  10. Fracture strength of three all-ceramic systems: Top-Ceram compared with IPS-Empress and In-Ceram.

    Science.gov (United States)

    Quran, Firas Al; Haj-Ali, Reem

    2012-03-01

    The purpose of this study was to investigate the fracture loads and mode of failure of all-ceramic crowns fabricated using Top-Ceram and compare it with all-ceramic crowns fabricated from well-established systems: IPS-Empress II, In-Ceram. Thirty all-ceramic crowns were fabricated; 10 IPS-Empress II, 10 In-Ceram alumina and 10 Top-Ceram. Instron testing machine was used to measure the loads required to introduce fracture of each crown. Mean fracture load for In-Ceram alumina [941.8 (± 221.66) N] was significantly (p > 0.05) higher than those of Top-Ceram and IPS-Empress II. There was no statistically significant difference between Top-Ceram and IPS-Empress II mean fracture loads; 696.20 (+222.20) and 534 (+110.84) N respectively. Core fracture pattern was highest seen in Top- Ceram specimens.

  11. Joining Dental Ceramic Layers With Glass

    Science.gov (United States)

    Saied, MA; Lloyd, IK; Haller, WK; Lawn, BR

    2011-01-01

    Objective Test the hypothesis that glass-bonding of free-form veneer and core ceramic layers can produce robust interfaces, chemically durable and aesthetic in appearance and, above all, resistant to delamination. Methods Layers of independently produced porcelains (NobelRondo™ Press porcelain, Nobel BioCare AB and Sagkura Interaction porcelain, Elephant Dental) and matching alumina or zirconia core ceramics (Procera alumina, Nobel BioCare AB, BioZyram yttria stabilized tetragonal zirconia polycrystal, Cyrtina Dental) were joined with designed glasses, tailored to match thermal expansion coefficients of the components and free of toxic elements. Scanning electron microprobe analysis was used to characterize the chemistry of the joined interfaces, specifically to confirm interdiffusion of ions. Vickers indentations were used to drive controlled corner cracks into the glass interlayers to evaluate the toughness of the interfaces. Results The glass-bonded interfaces were found to have robust integrity relative to interfaces fused without glass, or those fused with a resin-based adhesive. Significance The structural integrity of the interfaces between porcelain veneers and alumina or zirconia cores is a critical factor in the longevity of all-ceramic dental crowns and fixed dental prostheses. PMID:21802131

  12. Reduced wear of enamel with novel fine and nano-scale leucite glass-ceramics.

    Science.gov (United States)

    Theocharopoulos, Antonios; Chen, Xiaohui; Hill, Robert; Cattell, Michael J

    2013-06-01

    Leucite glass-ceramics used to produce all-ceramic restorations can suffer from brittle fracture and wear the opposing teeth. High strength and fine crystal sized leucite glass-ceramics have recently been reported. The objective of this study is to investigate whether fine and nano-scale leucite glass-ceramics with minimal matrix microcracking are associated with a reduction in in vitro tooth wear. Human molar cusps (n=12) were wear tested using a Bionix-858 testing machine (300,000 simulated masticatory cycles) against experimental fine crystal sized (FS), nano-scale crystal sized (NS) leucite glass-ceramics and a commercial leucite glass-ceramic (Ceramco-3, Dentsply, USA). Wear was imaged using Secondary Electron Imaging (SEI) and quantified using white-light profilometry. Both experimental groups were found to produce significantly (pceramic) loss than the FS group. Increased waviness and damage was observed on the wear surfaces of the Ceramco-3 glass-ceramic disc/tooth group in comparison to the experimental groups. This was also indicated by higher surface roughness values for the Ceramco-3 glass-ceramic disc/tooth group. Fine and nano-sized leucite glass-ceramics produced a reduction in in vitro tooth wear. The high strength low wear materials of this study may help address the many problems associated with tooth enamel wear and restoration failure. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Aspects of bonding between resin luting cements and glass ceramic materials.

    Science.gov (United States)

    Tian, Tian; Tsoi, James Kit-Hon; Matinlinna, Jukka P; Burrow, Michael F

    2014-07-01

    The bonding interface of glass ceramics and resin luting cements plays an important role in the long-term durability of ceramic restorations. The purpose of this systematic review is to discuss the various factors involved with the bond between glass ceramics and resin luting cements. An electronic Pubmed, Medline and Embase search was conducted to obtain laboratory studies on resin-ceramic bonding published in English and Chinese between 1972 and 2012. Eighty-three articles were included in this review. Various factors that have a possible impact on the bond between glass ceramics and resin cements were discussed, including ceramic type, ceramic crystal structure, resin luting cements, light curing, surface treatments, and laboratory test methodology. Resin-ceramic bonding has been improved substantially in the past few years. Hydrofluoric acid (HF) etching followed by silanizaiton has become the most widely accepted surface treatment for glass ceramics. However, further studies need to be undertaken to improve surface preparations without HF because of its toxicity. Laboratory test methods are also required to better simulate the actual oral environment for more clinically compatible testing. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  14. Modern electronic materials

    CERN Document Server

    Watkins, John B

    2013-01-01

    Modern Electronic Materials focuses on the development of electronic components. The book first discusses the history of electronic components, including early developments up to 1900, developments up to World War II, post-war developments, and a comparison of present microelectric techniques. The text takes a look at resistive materials. Topics include resistor requirements, basic properties, evaporated film resistors, thick film resistors, and special resistors. The text examines dielectric materials. Considerations include basic properties, evaporated dielectric materials, ceramic dielectri

  15. ACE Strategy with Virtual Channels

    Directory of Open Access Journals (Sweden)

    T. Tichy

    2008-12-01

    Full Text Available Cochlear implant is an electronic device, which can mediate hearing sensations to profoundly deaf people. Contemporary cochlear implants are sophisticated electronic devices; however, their performance could still be improved. This paper describes an experiment we made in that direction: additional 21 virtual channels were implemented by sequential stimulation of adjacent intracochlear electrodes, and the ACE strategy with virtual channels (ACEv, Advanced Combination Encoder strategy with virtual channels for the Nucleus® 24 Cochlear Implant System was created and verified in a clinical test with four patients.

  16. ION EXCHANGE IN GLASS-CERAMICS

    Directory of Open Access Journals (Sweden)

    George Halsey Beall

    2016-08-01

    Full Text Available In the past few years ion-exchange in glasses has found a renewed interest with a lot of new development and research in industrial and academic labs and the commercialization of materials with outstanding mechanical properties. These glasses are now widely used in many electronic devices including hand-held displays and tablets. The exchange is generally conducted in a bath of molten salt below the transition temperature of the glass. The exchange at the surface of an alkali ion by a bigger one brings compressive stress at the surface. The mechanical properties are dependent on the stress level at the surface and the depth of penetration of the bigger ion. As compared to glasses, glass-ceramics have the interest to display a wide range of aspects (transparent to opaque and different mechanical properties (especially higher modulus and toughness. There has been little research on ion-exchange in glass-ceramics. In these materials the mechanisms are much more complex than in glasses because of their polyphasic nature: ion-exchange generally takes place mostly in one phase (crystalline phase or residual glass. The mechanism can be similar to what is observed in glasses with the replacement of an ion by another in the structure. But in some cases this ion-exchange leads to microstructural modifications (for example amorphisation or phase change.This article reviews these ion-exchange mechanisms using several transparent and opaque alumino-silicate glass-ceramics as examples. The effect of the ion exchange in the various glass-ceramics will be described, with particular emphasis on flexural strength.

  17. Ion Exchange in Glass-Ceramics

    Science.gov (United States)

    Beall, George; Comte, Monique; Deneka, Matthew; Marques, Paulo; Pradeau, Philippe; Smith, Charlene

    2016-08-01

    In the past few years ion-exchange in glasses has found a renewed interest with a lot of new development and research in industrial and academic labs and the commercialization of materials with outstanding mechanical properties. These glasses are now widely used in many electronic devices including hand-held displays and tablets. The exchange is generally conducted in a bath of molten salt below the transition temperature of the glass. The exchange at the surface of an alkali ion by a bigger one brings compressive stress at the surface. The mechanical properties are dependent on the stress level at the surface and the depth of penetration of the bigger ion. As compared to glasses, glass-ceramics have the interest to display a wide range of aspects (transparent to opaque) and different mechanical properties (especially higher modulus and toughness). There has been little research on ion-exchange in glass-ceramics. In these materials the mechanisms are much more complex than in glasses because of their polyphasic nature: ion-exchange generally takes place mostly in one phase (crystalline phase or residual glass). The mechanism can be similar to what is observed in glasses with the replacement of an ion by another in the structure. But in some cases this ion-exchange leads to microstructural modifications (for example amorphisation or phase change). This article reviews these ion-exchange mechanisms using several transparent and opaque alumino-silicate glass-ceramics as examples. The effect of the ion exchange in the various glass-ceramics will be described, with particular emphasis on flexural strength.

  18. Hybrid Si/TMD 2D electronic double channels fabricated using solid CVD few-layer-MoS2 stacking for Vth matching and CMOS-compatible 3DFETs

    KAUST Repository

    Chen, Min Cheng

    2014-12-01

    Stackable 3DFETs such as FinFET using hybrid Si/MoS2 channels were developed using a fully CMOS-compatible process. Adding several molecular layers (3-16 layers) of the transition-metal dichalcogenide (TMD), MoS2 to Si fin and nanowire resulted in improved (+25%) Ion,n of the FinFET and nanowire FET (NWFET). The PFETs also operated effectively and the N/P device Vth are low and matched perfectly. The proposed heterogeneous Si/TMD 3DFETs can be useful in future electronics. © 2014 IEEE.

  19. Lightweight high performance ceramic material

    Science.gov (United States)

    Nunn, Stephen D [Knoxville, TN

    2008-09-02

    A sintered ceramic composition includes at least 50 wt. % boron carbide and at least 0.01 wt. % of at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy Ho, Er, Tm, Yb, and Lu, the sintered ceramic composition being characterized by a density of at least 90% of theoretical density.

  20. Ceramics in nuclear waste management

    Energy Technology Data Exchange (ETDEWEB)

    Chikalla, T D; Mendel, J E [eds.

    1979-05-01

    Seventy-three papers are included, arranged under the following section headings: national programs for the disposal of radioactive wastes, waste from stability and characterization, glass processing, ceramic processing, ceramic and glass processing, leaching of waste materials, properties of nuclear waste forms, and immobilization of special radioactive wastes. Separate abstracts were prepared for all the papers. (DLC)

  1. Micromolding for ceramic microneedle arrays

    NARCIS (Netherlands)

    van Nieuwkasteele-Bystrova, Svetlana Nikolajevna; Lüttge, Regina

    2011-01-01

    The fabrication process of ceramic microneedle arrays (MNAs) is presented. This includes the manufacturing of an SU-8/Si-master, its double replication resulting in a PDMS mold for production by micromolding and ceramic sintering. The robustness of the replicated structures was tested by means of

  2. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 8. Science and Technology of Ceramics - Traditional Ceramics. Sheela K Ramasesha. Series Article Volume 4 Issue 8 August 1999 pp 16-24. Fulltext. Click here to view fulltext PDF. Permanent link:

  3. Science and Technology of Ceramics

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 12. Science and Technology of Ceramics - Functional Ceramics. Sheela K Ramasesha. Series Article Volume 4 Issue 12 December 1999 pp 21-30. Fulltext. Click here to view fulltext PDF. Permanent link:

  4. New Hypothesis for SOFC Ceramic Oxygen Electrode Mechanisms

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Chatzichristodoulou, Christodoulos; Graves, Christopher R.

    2016-01-01

    -Popper structured electrode materials are sufficiently electron and oxygen ion conducting to provide reaction sites despite that the bulk phase of such an oxide layer is insulating. We claim that a few nanometer thin layer of mixed SrO-La2O3 that contains some dissolved transition metal and some impurities plus two......A new hypothesis for the electrochemical reaction mechanism in solid oxide cell ceramic oxygen electrodes is proposed based on literature including our own results. The hypothesis postulates that the observed thin layers of SrO-La2O3 on top of ceramic perovskite and other Ruddlesden...

  5. Characterization of a ceramic waste form encapsulating radioactive electrorefiner salt

    Energy Technology Data Exchange (ETDEWEB)

    Moschetti, T. L.; Sinkler, W.; DiSanto, T.; Noy, M.; Warren, A. R.; Cummings, D. G.; Johnson, S. G.; Goff, K. M.; Bateman, K. J.; Frank, S. M.

    1999-11-11

    Argonne National Laboratory has developed a ceramic waste form to immobilize radioactive waste salt produced during the electrometallurgical treatment of spent fuel. This study presents the first results from electron microscopy and durability testing of a ceramic waste form produced from that radioactive electrorefiner salt. The waste form consists of two primary phases: sodalite and glass. The sodalite phase appears to incorporate most of the alkali and alkaline earth fission products. Other fission products (rare earths and yttrium) tend to form a separate phase and are frequently associated with the actinides, which form mixed oxides. Seven-day leach test results are also presented.

  6. Ceramic thermal barrier coatings for commercial gas turbine engines

    Science.gov (United States)

    Meier, Susan Manning; Gupta, Dinesh K.; Sheffler, Keith D.

    1991-01-01

    The paper provides an overview of the short history, current status, and future prospects of ceramic thermal barrier coatings for gas turbine engines. Particular attention is given to plasma-sprayed and electron beam-physical vapor deposited yttria-stabilized (7 wt pct Y2O3) zirconia systems. Recent advances include improvements in the spallation life of thermal barrier coatings, improved bond coat composition and spraying techniques, and improved component design. The discussion also covers field experience, life prediction modeling, and future directions in ceramic coatings in relation to gas turbine engine design.

  7. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-12-28

    During Phase I, the following goals were achieved: (1) design and fabrication of a novel, nano-dimensional CNT field emitter assembly for high current density application, with high durability; (2) fabrication of a ceramic based micro channel plate (MCP) and characterization of its secondary electron emission; and (3) characterizing the CNT/MCP cathode for high field emission and durability. As a result of these achievements, a relatively high current density of ~ 1.2 A/cm2 from a CNT cathode and single channel MCP were measured. The emission current was also extremely stable with a peak-to-peak variation of only 1.8%. The emission current could be further enhanced to meet requirements for electron lens applications by increasing the number of MCP channels. A calculation for maximum possible current density with a 1200 channel/cm2 MCP, placed over a cathode with 1200 uniformly functioning CNTs, would be ~1.46 kA/cm2, neglecting space charge limitations. Clearly this level of emission is far greater than what is needed for the electron lens application, but it does offer a highly comforting margin to account for sub-standard emitters and/or to allow the lesser challenge of building a cathode with fewer channels/cm2. A satisfactory goal for the electron lens application would be a controllable emission of 2-4 mA per channel in an ensemble of 800-1200 uniformly-functioning channels/cm2, and a cathode with overall area of about 1 cm2.

  8. Behavior of micro-particles in monolith ceramic membrane filtration with pre-coagulation.

    Science.gov (United States)

    Yonekawa, H; Tomita, Y; Watanabe, Y

    2004-01-01

    This paper is intended to clarify the characteristics unique to monolith ceramic membranes with pre-coagulation by referring to the behavior of micro-particles. Flow analysis and experiments have proved that monolith ceramic membranes show a unique flow pattern in the channels within the element, causing extremely rapid flocculation in the channel during dead-end filtration. It was assumed that charge-neutralized micro-particles concentrated near the membrane surface grow in size due to flocculation, and as a result, coarse micro-particles were taken up by the shearing force to flow out. As the dead end points of flow in all the channels are located near the end of the channels with higher filterability, most of the flocculated coarse particles are formed to a columnar cake intensively at the dead end point. Therefore cake layer forming on the membrane other than around the dead end point is alleviated. This behavior of particle flocculation and cake formation at the dead end point within the channels are unique characteristics of monolith ceramic membranes. This is why all monolith ceramic membrane water purification systems operating in Japan do not have pretreatment equipment for flocculation and sedimentation.

  9. Low thermal expansion glass ceramics

    CERN Document Server

    1995-01-01

    This book is one of a series reporting on international research and development activities conducted by the Schott group of companies With the series, Schott aims to provide an overview of its activities for scientists, engineers, and managers from all branches of industry worldwide where glasses and glass ceramics are of interest Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated This volume describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization Thus glass ceramics with thermal c...

  10. Ceramic membrane development in NGK

    Science.gov (United States)

    Araki, Kiyoshi; Sakai, Hitoshi

    2011-05-01

    NGK Insulators, Ltd. was established in 1919 to manufacture the electric porcelain insulators for power transmission lines. Since then, our business has grown as one of the world-leading ceramics manufacturing companies and currently supply with the various environmentally-benign ceramic products to worldwide. In this paper, ceramic membrane development in NGK is described in detail. We have been selling ceramic microfiltration (MF) membranes and ultra-filtration (UF) membranes for many years to be used for solid/liquid separation in various fields such as pharmaceutical, chemical, food and semiconductor industries. In Corporate R&D, new ceramic membranes with sub-nanometer sized pores, which are fabricated on top of the membrane filters as support, are under development for gas and liquid/liquid separation processes.

  11. Method of forming a ceramic matrix composite and a ceramic matrix component

    Science.gov (United States)

    de Diego, Peter; Zhang, James

    2017-05-30

    A method of forming a ceramic matrix composite component includes providing a formed ceramic member having a cavity, filling at least a portion of the cavity with a ceramic foam. The ceramic foam is deposited on a barrier layer covering at least one internal passage of the cavity. The method includes processing the formed ceramic member and ceramic foam to obtain a ceramic matrix composite component. Also provided is a method of forming a ceramic matrix composite blade and a ceramic matrix composite component.

  12. The search for new physics in the diphoton decay channel and the upgrade of the Tile-Calorimeter electronics of the ATLAS detector.

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00508435

    The discovery of the Higgs boson at the Large Hadron Collider in Switzerland marks the beginning of a new era: Physics beyond the Standard Model (SM). A model is proposed to describe numerous Run I features observed with both the ATLAS and CMS experiments. The model introduces a heavy scalar estimated to be around 270 GeV and an intermediate scalar which can decay into both dark matter and SM particles. Three different final state searches, linked by the new hypothesis, are presented. These are the $hh\\rightarrow\\gamma\\gamma b\\overline{b}, \\gamma\\gamma + E^{miss}_{T}$ and high mass diphoton channels. No significant excesses were observed in any channel using the available datasets and limits were set on the relevant cross sections times branching ratios. The lack of statistics in the $\\gamma\\gamma b\\overline{b}$ analysis prevents any conclusive statement in regard to the excess observed with Run I data. Observing no excess in the $\\gamma\\gamma + E^{miss}_{T}$ channel with the current amount of data is also c...

  13. Nanoscale Vacuum Channel Transistor.

    Science.gov (United States)

    Han, Jin-Woo; Moon, Dong-Il; Meyyappan, M

    2017-04-12

    Vacuum tubes that sparked the electronics era had given way to semiconductor transistors. Despite their faster operation and better immunity to noise and radiation compared to the transistors, the vacuum device technology became extinct due to the high power consumption, integration difficulties, and short lifetime of the vacuum tubes. We combine the best of vacuum tubes and modern silicon nanofabrication technology here. The surround gate nanoscale vacuum channel transistor consists of sharp source and drain electrodes separated by sub-50 nm vacuum channel with a source to gate distance of 10 nm. This transistor performs at a low voltage (3 microamperes). The nanoscale vacuum channel transistor can be a possible alternative to semiconductor transistors beyond Moore's law.

  14. Proton-conducting cerate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Pederson, L.R.; Coffey, G.W.; Bates, J.L.; Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-08-01

    Single-cell solid oxide fuel cells were constructed using strontium cerate as the electrolyte and their performance tested. Like certain zirconates, hafnates, and tantalates, the cerate perovskites are among a class of solid electrolytes that conduct protons at elevated temperatures. Depending on the temperature and chemical environment, these ceramics also support electronic and oxygen ion currents. A maximum power output of {approx}100 mW per cm{sup 2} electrolyte surface area was obtained at 900{degrees}C using 4% hydrogen as the fuel and air as the oxidant. A series of rare earth/ceria/zirconia were prepared and their electrical properties characterized. Rare earth dopants included ytterbia, yttria, terbia, and europia. Ionic conductivities were highest for rare earth/ceria and rare earth zirconia compositions; a minimum in ionic conductivity for all series were found for equimolar mixtures of ceria and zirconia. Cerium oxysulfide is of interest in fossil energy applications because of its high chemical stability and refractory nature. An alternative synthesis route to preparing cerium oxysulfide powders has been developed using combustion techniques.

  15. Manufacture, characterisation and properties of novel fluorcanasite glass-ceramics.

    Science.gov (United States)

    Pollington, Sarah; van Noort, Richard

    2012-11-01

    The aim of this study was to investigate the manufacture and characterisation of different compositions of fluorcanasite glass-ceramics with reduced fluorine content and to assess their mechanical and physical properties. Three compositional variations (S80, S81 and S82) of a fluorcanasite glass were investigated. Differential thermal analysis (DTA) and X-ray diffraction (XRD) identified crystallisation temperatures and phases. X-ray fluorescence (XRF) determined the element composition in the glass-ceramics. Different heat treatments [2 h nucleation and either 2 or 4 h crystallisation] were used for the glasses. Scanning electron microscopy (SEM) examined the microstructure of the cerammed glass. The chemical solubility, biaxial flexural strength, fracture toughness, hardness and brittleness index of S81 and S82 fluorcanasite were investigated with lithium disilicate (e.max CAD, Ivoclar Vivadent) as a commercial comparison. Statistical analysis was performed using one-way ANOVA with Tukey's multiple comparison tests (Pglasses. XRD analysis confirmed fluorcanasite formation with the S81 and S82 compositions, with the S82 (2+2h) showing the most prominent crystal structure. The chemical solubility of the glass-ceramics was significantly different, varying from 2565 ± 507 μg/cm(2) for the S81 (2+2 h) to 722 ± 177 μg/cm(2) for the S82 (2+2 h) to 37.4 ± 25.2 μg/cm(2) for the lithium disilicate. BFS values were highest for the S82 (2+2 h) composition (250 ± 26 MPa) and lithium disilicate (266 ± 37 MPa) glass-ceramics. The fracture toughness was higher for the S82 compositions, with the S82 (2+2h) attaining the highest value of 4.2 ± 0.3 MPa m(1/2)(P=0.01). The S82 (2+2 h) fluorcanasite glass-ceramic had the lowest brittleness index. The S82 (2+2 h) fluorcanasite glass-ceramic has acceptable chemical solubility, high biaxial flexural strength, fracture toughness and hardness. A novel glass-ceramic has been developed with potential as a restorative material. The

  16. Characterization of CVI densification of ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Starr, T.L.; Stock, S.R.; Lee, S. [Georgia Institute of Technology, Atlanta, GA (United States)

    1995-05-01

    Ceramic matrix composites promise higher operating temperature and better thermodynamic efficiency in many enregy conversion systems. In particular, composites fabricated by the chemical vapor infiltration (CVI) process have excellent mechanical properties and, using the forced flow-thermal gradient variation, good processing economics in small scale demonstrations. Scale-up to larger, more complex shapes requires understanding of gas flow through the fiber preform and of the relationship between fiber architecture and densification behavior. This understanding is needed for design of preforms for optimum infiltration. The objective of this research is to observe the deposition of matrix material in the pores of a ceramic fiber preform at various stages of the CVI process. These observations allow us to relate local deposition rates in various regions of the composite to the connectivity of the surrounding network of porosity and to better model the relationship between gas transport and fiber architecture in CVI preforms. Our observation of the CVI process utilizes high resolution X-ray tomographic microscopy (XTM) in collaboration with Dr. John Kinney at Lawrence Livermore National Laboratory with repeated imaging of a small preform specimens after various processing times. We use these images to determine geometry and dimensions of channels between and through layers in cloth lay-up preform during CVI densification and relate these to a transport model.

  17. Thick ceramic coating technique. Atsuniku ceramic coating gijutsu

    Energy Technology Data Exchange (ETDEWEB)

    Sata, N. (Government Industrial Reserach Institute, Tohoku, Sendai (Japan))

    1987-10-15

    This paper describes a thick ceramic coating technique that uses a reactive bonding process. This process coats interior of a metallic cylinder or surface of a metal having optional curvature with thick (2 mm to 3 mm) ceramics composed mainly of alumina. The process features easiness in coating and simplicity of the equipment. Reactive heat generated from thermit reaction melts iron and alumina as the reaction products, and produces molten ceramics which is cooled on the metal surface to deposit and solidify as a ceramics layer, thus completing the synthesis and the coating in one process. Its application fields would include reaction tubes, abrasive fluid tubes, and high-temperature fluid tubes that can utilize the ceramics' resistance to abrasion, corrosion and heat as well as heat insulation. The ceramics layer has a hardness of about Hv 1500 and porosity from 2 to 3%. The bonding strength between the substrate metal and the ceramics layer can achieve 10 MPa to 20 MPa as a result of surface oxidation treatment and cooling treatment given initially to prevent the outer wall temperature from rising. 2 figs.

  18. Flexural strength and failure modes of layered ceramic structures

    Science.gov (United States)

    Borba, Márcia; de Araújo, Maico D.; de Lima, Erick; Yoshimura, Humberto N.; Cesar, Paulo F.; Griggs, Jason A.; Bona, Álvaro Della

    2011-01-01

    Objective to evaluate the effect of the specimen design on the flexural strength (σf) and failure mode of ceramic structures, testing the hypothesis that the ceramic material under tension controls the mechanical performance of the structure. Methods Three ceramics used as framework materials for fixed partial dentures (YZ - Vita In-Ceram YZ; IZ - Vita In-Ceram Zirconia; AL - Vita In-Ceram AL) and two veneering porcelains (VM7 and VM9) were studied. Bar-shaped specimens were produced in three different designs (n=10): monolithic, two layers (porcelain-framework) and three layers (TRI) (porcelain-framework-porcelain). Specimens were tested for three-point flexural strength at 1 MPa/s in 37°C artificial saliva. For bi-layered design, the specimens were tested in both conditions: with porcelain (PT) or framework ceramic (FT) layer under tension. Fracture surfaces were analyzed using stereomicroscope and scanning electron microscopy (SEM). Young’s modulus (E) and Poisson’s ratio (ν) were determined using ultrasonic pulse-echo method. Results were statistically analyzed by Kruskal-Wallis and Student-Newman-Keuls tests. Results Except for VM7 and VM9, significant differences were observed for E values among the materials. YZ showed the highest ν value followed by IZ and AL. YZ presented the highest σf. There was no statistical difference in the σf value between IZ and IZ-FT and between AL and AL-FT. σf values for YZ-PT, IZ-PT, IZ-TRI, AL-PT, AL-TRI were similar to the results obtained for VM7 and VM9. Two types of fracture mode were identified: total and partial failure. Significance The mechanical performance of the specimens was determined by the material under tension during testing, confirming the study hypothesis. PMID:21982199

  19. Ionic Channels in Thunderclouds

    Science.gov (United States)

    Losseva, T. V.; Fomenko, A. S.; Nemtchinov, I. V.

    2007-12-01

    We proceed to study the formation and propagation of ionic channels in thunderclouds in the framework of the model of the corona discharge wave propagation (Fomenko A.S., Losseva T.V., Nemtchinov I.V. The corona discharge waves in thunderclouds and formation of ionic channels // 2004 Fall Meeting. EOS Trans. AGU. 2004. V. 85. ¹ 47. Suppl. Abstract AE23A-0835.). In this model we proposed a hypothesis that the structure of a thundercloud becomes nonuniform due to corona discharge on the drops and ice particles and formation of ionic channels with higher conductivity than the surrounding air. When the onset strength of corona discharge becomes smaller than the electric field strength the corona discharge increases concentrations of ions in a small part of the cloud (a hot spot). An additional charge at opposite ends of the hot spot forms due to polarization process. The increased electric field initiates corona discharge in other parts of the cloud on ice particles and water drops with smaller sizes. The corona discharge front moves as a wave with the velocity of the order of ion drift and formes a highly conductive channel. We model this non-stationary problem with Poisson equation which is solved simultaneously with a simplified set of kinetic equations for ions, small charged particles and electrons (at high electric fields), including ionization due to electronic impact, attachment and formation of positive ions. By applying 3D numerical simulations we obtain the parameters of formed ionic channels with respect to onset electric fields both from large particles (in hot spot) and from small particles (surrounding hot spot), microscopic currents from particles with different sizes and the external electric field in the cloud. The interaction of ionic channels is also investigated. This work was supported by Russian Foundation of Basic Research (Project No 07-05-00998-à).

  20. Gamma radiation in ceramic capacitors: a study for space missions

    Science.gov (United States)

    dos Santos Ferreira, Eduardo; Sarango Souza, Juliana

    2017-10-01

    We studied the real time effects of the gamma radiation in ceramic capacitors, in order to evaluate the effects of cosmic radiation on these devices. Space missions have electronic circuits with various types of devices, many studies have been done on semiconductor devices exposed to gamma radiation, but almost no studies for passive components, in particular ceramic capacitors. Commercially sold ceramic capacitors were exposed to gamma radiation, and the capacitance was measured before and after exposure. The results clearly show that the capacitance decreases with exposure to gamma radiation. We confirmed this observation in a real time capacitance measurement, obtained using a data logging system developed by us using the open source Arduino platform.

  1. High-temperature corrosion resistance of ceramics and ceramic coatings

    Energy Technology Data Exchange (ETDEWEB)

    Tortorelli, P.F.

    1996-06-01

    Ceramics and ceramic composites offer the potential to operate fossil energy systems at the higher temperatures necessary for improved energy efficiency and better environmental control. However, because many fossil fuel-derived processes contain sulfur, chlorine, and carbon, as well as oxygen, degradation from high-temperature corrosion and environmental effects arising from reactions of solids with gases and condensable products is a common life-determining factor in operating systems. Ceramic-based products are not immune to such degradation; adequate corrosion resistance must be assured to exploit the technical and economic potential of such materials. This is normally accomplished by using stable, sound oxides that exist in their bulk form, that naturally grow as surface layers upon exposure to an oxidizing environment, or that are deposited as a coating on a susceptible material. It is therefore important to examine the critical issues with respect to more environmental stability of ceramics that have the potential to be corrosion resistant in particular fossil environments. Key aspects include not only chemical compatibility, but the influence of the environment on the mechanical behavior of the ceramic materials. In addition, for coatings, the mechanical reliability of the ceramic is a key issue in that an otherwise corrosion-resistant surface layer must remain sound and adherent in order to provide protection to the underlying substrate. The purpose of this work is to support the development of advanced ceramics and ceramic composites for applications in fossil environments by examining critical issues related to high-temperature corrosion resistance. More specifically, the overall objective of this task is to examine the chemical compatibility and reliability of potentially corrosion-resistant ceramics being developed as protective overcoats and/or structural materials as parts of other work elements funded by the AR&TD Program.

  2. Ceramic fiber reinforced filter

    Science.gov (United States)

    Stinton, David P.; McLaughlin, Jerry C.; Lowden, Richard A.

    1991-01-01

    A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

  3. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

    In the present quarter, the possibility of using a more complex interfacial engineering approach to the development of reliable and stable oxygen transport perovskite ceramic membranes/metal seals is discussed. Experiments are presented and ceramic/metal interactions are characterized. Crack growth and fracture toughness of the membrane in the reducing conditions are also discussed. Future work regarding this approach is proposed are evaluated for strength and fracture in oxygen gradient conditions. Oxygen gradients are created in tubular membranes by insulating the inner surface from the reducing environment by platinum foils. Fracture in these test conditions is observed to have a gradient in trans and inter-granular fracture as opposed to pure trans-granular fracture observed in homogeneous conditions. Fracture gradients are reasoned to be due to oxygen gradient set up in the membrane, variation in stoichiometry across the thickness and due to varying decomposition of the parent perovskite. The studies are useful in predicting fracture criterion in actual reactor conditions and in understanding the initial evolution of fracture processes.

  4. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire—KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

    Science.gov (United States)

    Zvorykin, V. D.; Ionin, Andrei A.; Levchenko, A. O.; Mesyats, Gennadii A.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, Igor V.; Sunchugasheva, E. S.; Ustinovskii, N. N.; Shutov, A. V.

    2013-04-01

    The problem of the production of extended (~1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2-0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration (~100 ns), maintains the electron density at a level ne = (3-5) × 1014 cm—3 by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy (~0.5 eV) and a long lifetime (~1 ms), which are produced upon cessation of the laser pulse.

  5. Rietveld refinement, electronic structure and ionic conductivity of Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}F{sub 2} and Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}O ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Boughzala, Khaled, E-mail: khaledboughzala@gmail.com [Higher Institute for Technological Studies, 5070 Ksar Hellal (Tunisia); Preparatory Institute for Engineering Studies, 5000 Monastir (Tunisia); Debbichi, Mourad [Laboratory of Condensed Matter and Nanosciences, Department of Physics, Faculty of Science of Monastir, Road of the Environment, 5019 Monastir (Tunisia); College of Sciences and Arts in Oqlatu’s Soqoor, Qassim University (Saudi Arabia); Njema, Hela; Bouzouita, Khaled [Preparatory Institute for Engineering Studies, 5000 Monastir (Tunisia)

    2016-07-15

    In this paper, we report the effect of the tunnel anions on the ionic conductivity of Strontium-Lanthanum silicate apatites. The Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}F{sub 2} and Sr{sub 4}La{sub 6}(SiO{sub 4}){sub 6}O ceramics were prepared by the solid state reaction method. X-ray diffraction, NMR spectroscopy and Raman measurements were performed to investigate the crystal structure and vibrational active modes. Moreover, the electronic structures of the crystals were evaluated by the first-principles quantum mechanical calculation based on the density functional theory. Finally, the ionic conductivity was studied according to the complex impedance method. - Graphical abstract: The relaxed primitive unit cell for Sr{sub 4}La{sub 6}Fap. Display Omitted.

  6. Electronic waste recycling techniques

    CERN Document Server

    Bernardes, Andréa

    2015-01-01

    This book presents an overview of the characterization of electronic waste. In addition, processing techniques for the recovery of metals, polymers and ceramics are described. This book serves as a source of information and as an educational technical reference for practicing scientists and engineers, as well as for students.

  7. Role of ceramic matrix and Au fraction on the morphology and optical properties of cosputtered Au-ceramic thin films

    Science.gov (United States)

    Hazra, S.; Gibaud, A.; Sella, C.

    2007-06-01

    Surface sensitive x-ray scattering studies were carried out to understand the morphology of cermet thin films prepared by cosputtering metallic gold and ceramic materials on float glass substrates. It has been observed that the morphology of Au clusters in cermet thin films depends strongly on the matrix during growth, even if, all other conditions are kept identical. In particular, nearly isotropic growth of Au clusters, to form nanoparticles, is found in silica and alumina matrices, while anisotropic columnar-like growth of Au clusters, to form a nanorod-like shape, is found in a titanium oxide matrix. Thickness of the films was also found very different, which is likely to be related to the different sputtering yields of the ceramic materials. The volume fraction of Au estimated from the electron density profile shows that the total volume or the amount of Au is different in films of different ceramic matrices. This suggests that even the sputtering yield of Au is very different in the presence of different ceramic atmosphere, which is likely to be responsible for having a different morphology of Au clusters in different matrices. Optical absorption spectra of the films, on the other hand, show linear dependence of the absorption peak position with the volume fraction of Au and independent of both the ceramic matrix and morphology of Au clusters.

  8. Current status and future aspects of R and D activities on electro- ceramic components in Japanese industry

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, Hiroshi, E-mail: takagihr@murata.co.jp [Material Development Group, Technology and Business Development Unit, Murata Mfg. Co., Ltd., Yasu-shi, Shiga 520-2393 (Japan)

    2011-05-15

    The oldest pottery in Japan was made 16,500 years ago in Jomon period. On the background of a long history of Japanese ceramics, Murata and other Japanese manufacturers have been developing electro-ceramic materials and manufacturing many kinds of electronic components using them. In 1937, TDK manufactured ferrite cores first in the world. Then, Japanese electro-ceramic industry has led the world on electro-ceramic materials and components until now, especially in the fields of BaTiO{sub 3}, PZT, PTC thermistor, ZnO varistor and insulating ceramics. From the analysis of the papers reported lately, R and D activities of Japanese manufacturers are understood to cover not only improving properties of electro-ceramics, but also appropriate technologies and basic technologies.

  9. Current status and future aspects of R&D activities on electro- ceramic components in Japanese industry

    Science.gov (United States)

    Takagi, Hiroshi

    2011-05-01

    The oldest pottery in Japan was made 16,500 years ago in Jomon period. On the background of a long history of Japanese ceramics, Murata and other Japanese manufacturers have been developing electro-ceramic materials and manufacturing many kinds of electronic components using them. In 1937, TDK manufactured ferrite cores first in the world. Then, Japanese electro-ceramic industry has led the world on electro-ceramic materials and components until now, especially in the fields of BaTiO3, PZT, PTC thermistor, ZnO varistor and insulating ceramics. From the analysis of the papers reported lately, R&D activities of Japanese manufacturers are understood to cover not only improving properties of electro-ceramics, but also appropriate technologies and basic technologies.

  10. Ceramics in geothermal power plant. Chinetsu hatsuden to ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sanada, N. (Government Industrial Research Institute, Tohoku, Sendai (Japan))

    1991-03-30

    This paper summarizes how ceramics are used in geothermal power plants. Although there are not many cases of using ceramics in geothermal power generation, they are used or discussed of their use where environmental temperature or flow velocity in geothermal fluid is high, or solids are anticipated to get mixed, with an expectation on their superior heat and erosion resistance. Applications may include use of alumina ceramics in nozzles in total flow generation turbines, magnesium oxide insulator cable to suspend a measuring instrument to inspect geothermal beds, titania spraying and covering of carbon steel mirror plates in a power plant separator, and SiC ceramics in bearings for downhole pump motors. The paper also describes several examples of problems in development which have been tackled with to date (including manufacture of metal-alumina pipes using a centrifugal thermit process). 8 refs., 6 figs., 1 tab.

  11. Autothermal hydrogen generation from methanol in a ceramic microchannel network

    Science.gov (United States)

    Moreno, Angela M.; Wilhite, Benjamin A.

    In this paper, the authors present the first demonstration of a new class of integrated ceramic microchannel reactors for all-in-one reforming of hydrocarbon fuels. The reactor concept employs precision-machined metal distributors capable of realizing complex flow distribution patterns with extruded ceramic microchannel networks for cost-effective thermal integration of multiple chemical processes. The presently reported reactor is comprised of five methanol steam reforming channels packed with CuO/γ-Al 2O 3, interspersed with four methanol combustion channels washcoated with Pt/γ-Al 2O 3, for autothermal hydrogen production (i.e., without external heating). Results demonstrate the capability of this new device for integrating combustion and steam reforming of methanol for autothermal production of hydrogen, owing to the axially self-insulating nature of distributor-packaged ceramic microchannels. In the absence of any external insulation, stable reforming of methanol to hydrogen at conversions >90% and hydrogen yields >70% was achieved at a maximum reactor temperature of 400 °C, while simultaneously maintaining a packaging temperature <50 °C.

  12. Theory of low-energy electron-molecule collision physics in the coupled-channel method and application to e-CO/sub 2/ scattering. [0. 01 to 10 eV, potentials, partial waves

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, M.A.

    1976-08-01

    A theory of electron-molecule scattering based on the fixed-nuclei approximation in a body-fixed reference frame is formulated and applied to e-CO/sub 2/ collisions in the energy range from 0.07 to 10.0 eV. The procedure used is a single-center coupled-channel method which incorporates a highly accurate static interaction potential, an approximate local exchange potential, and an induced polarization potential. Coupled equations are solved by a modification of the integral equations algorithm; several partial waves are required in the region of space near the nuclei, and a transformation procedure is developed to handle the consequent numerical problems. The potential energy is converged by separating electronic and nuclear contributions in a Legendre-polynomial expansion and including a large number of the latter. Formulas are derived for total elastic, differential, momentum transfer, and rotational excitation cross sections. The Born and asymptotic decoupling approximations are derived and discussed in the context of comparison with the coupled-channel cross sections. Both are found to be unsatisfactory in the energy range under consideration. An extensive discussion of the technical aspects of calculations for electron collisions with highly nonspherical targets is presented, including detailed convergence studies and a discussion of various numerical difficulties. The application to e-CO/sub 2/ scattering produces converged results in good agreement with observed cross sections. Various aspects of the physics of this collision are discussed, including the 3.8 eV shape resonance, which is found to possess both p and f character, and the anomalously large low-energy momentum transfer cross sections, which are found to be due to ..sigma../sub g/ symmetry. Comparison with static and static-exchange approximations are made.

  13. Effects of multiple firings on the mechanical properties and microstructure of veneering ceramics for zirconia frameworks.

    Science.gov (United States)

    Tang, Xuehua; Nakamura, Takashi; Usami, Hirofumi; Wakabayashi, Kazumichi; Yatani, Hirofumi

    2012-05-01

    The purpose of this study is to evaluate the effects of multiple firings on the mechanical properties and microstructure of veneering ceramics used with zirconia frameworks. Five different veneering ceramics for zirconia frameworks were used: Vintage ZR (ZR), Cerabien ZR (CZR), Vita VM9 (VM9), Cercon ceram KISS (KISS), IPS e.max ceram (e.max), and one veneering ceramic used for PFM frameworks: Vintage MP (MP). Twenty specimens were fabricated of each veneering ceramic. Ten specimens were fired twice and another ten specimens were fired ten times. Three-point flexural strength following the ISO 6872 and Vickers hardness were measured, and fracture toughness (K(IC)) was calculated. Density and porosity were determined. Specimens were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). For all materials, density increased and porosity decreased after 10 firings. Significant differences in density and porosity were observed between 2 and 10 firings, with the exception of VM9 (Pveneering ceramics for zirconia restorations. By 10 firings, the density and hardness of the veneering ceramics used with zirconia frameworks were raised, and porosity was reduced. However, no significant changes occurred in flexural strength, fracture toughness or microstructure. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Fit of all-ceramic posterior fixed partial denture frameworks in vitro.

    Science.gov (United States)

    Bindl, Andreas; Mörmann, Werner H

    2007-12-01

    The objective of this study was to evaluate, by scanning electron microscopy, the marginal and internal fit of all-ceramic three-unit fixed partial denture (FPD) frames fabricated by computer-assisted design/computer-aided machining (CAD/CAM) and CAM techniques using blocks of infiltration ceramic, high-strength yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia sinter ceramic, high-strength dense sintered Y-TZP zirconia ceramic, and glass ceramic. Slip-cast infiltration ceramic was used as a traditional control. The cementation interface widths of the FPD frame copings on butt (A) shoulders of Cerec In-Ceram zirconia (A1, 53 +/- 17 microm) were smaller than those of slip-cast In-Ceram zirconia (A6, 113 +/- 25 microm). Cerec Y-TZP zirconia (A2, 53 +/- 9 pm) and DCS Y-TZP zirconia (A4, 32 +/- 6 microm) interfaces were both significantly smaller than those of Cercon Y-TZP zirconia (A5, 120 +/- 6 microm). Internally, A2 (103 +/- 14) interfaces were smaller than A4 interfaces (144 +/- 15 microm). On chamfer shoulders (B), Cerec Y-TZP zirconia (B1, 71 +/- 5 microm) interfaces were smaller than Cercon interfaces (B2, 129 +/- 38 microm); internally, B1 (80 +/- 11 microm) interfaces were smaller than B2 interfaces (130 +/- 12 microm). CAD/CAM produced better marginal and internal accuracy of fit compared to slip casting and CAM techniques.

  15. Search for excited and exotic electrons in the egamma decay channel in pp collisions at sqrt[s] = 1.96 TeV.

    Science.gov (United States)

    Acosta, D; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arisawa, T; Arguin, J-F; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Bacchetta, N; Bachacou, H; Badgett, W; Barbaro-Galtieri, A; Barker, G J; Barnes, V E; Barnett, B A; Baroiant, S; Barone, M; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Ben-Haim, E; Benjamin, D; Beretvas, A; Bhatti, A; Binkley, M; Bisello, D; Bishai, M; Blair, R E; Blocker, C; Bloom, K; Blumenfeld, B; Bocci, A; Bodek, A; Bolla, G; Bolshov, A; Booth, P S L; Bortoletto, D; Boudreau, J; Bourov, S; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canepa, A; Casarsa, M; Carlsmith, D; Carron, S; Carosi, R; Cavalli-Sforza, M; Castro, A; Catastini, P; Cauz, D; Cerri, A; Cerri, C; Cerrito, L; Chapman, J; Chen, C; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chu, M L; Chuang, S; Chung, J Y; Chung, W-H; Chung, Y S; Ciobanu, C I; Ciocci, M A; Clark, A G; Clark, D; Coca, M; Connolly, A; Convery, M; Conway, J; Cooper, B; Cordelli, M; Cortiana, G; Cranshaw, J; Cuevas, J; Culbertson, R; Currat, C; Cyr, D; Dagenhart, D; Da Ronco, S; D'Auria, S; de Barbaro, P; De Cecco, S; De Lentdecker, G; Dell'Agnello, S; Dell'Orso, M; Demers, S; Demortier, L; Deninno, M; De Pedis, D; Derwent, P F; Dionisi, C; Dittmann, J R; Doksus, P; Dominguez, A; Donati, S; Donega, M; Donini, J; D'Onofrio, M; Dorigo, T; Drollinger, V; Ebina, K; Eddy, N; Ely, R; Erbacher, R; Erdmann, M; Errede, D; Errede, S; Eusebi, R; Fang, H-C; Farrington, S; Fedorko, I; Feild, R G; Feindt, M; Fernandez, J P; Ferretti, C; Field, R D; Fiori, I; Flanagan, G; Flaugher, B; Flores-Castillo, L R; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Frisch, H; Fujii, Y; Furic, I; Gajjar, A; Gallas, A; Galyardt, J; Gallinaro, M; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D W; Gerchtein, E; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Ginsburg, C; Giolo, K; Giordani, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, D; Goldstein, J; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Gresele, A; Griffiths, M; Grosso-Pilcher, C; Grundler, U; Guenther, M; da Costa, J Guimaraes; Haber, C; Hahn, K; Hahn, S R; Halkiadakis, E; Hamilton, A; Han, B-Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harr, R F; Harris, R M; Hartmann, F; Hatakeyama, K; Hauser, J; Hays, C; Hayward, H; Heider, E; Heinemann, B; Heinrich, J; Hennecke, M; Herndon, M; Hill, C; Hirschbuehl, D; Hocker, A; Hoffman, K D; Holloway, A; Hou, S; Houlden, M A; Huffman, B T; Huang, Y; Hughes, R E; Huston, J; Ikado, K; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Issever, C; Ivanov, A; Iwata, Y; Iyutin, B; James, E; Jang, D; Jarrell, J; Jeans, D; Jensen, H; Jeon, E J; Jones, M; Joo, K K; Jun, S; Junk, T; Kamon, T; Kang, J; Karagoz Unel, M; Karchin, P E; Kartal, S; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, M S; Kim, S B; Kim, S H; Kim, T H; Kim, Y K; King, B T; Kirby, M; Kirsch, L; Klimenko, S; Knuteson, B; Ko, B R; Kobayashi, H; Koehn, P; Kong, D J; Kondo, K; Konigsberg, J; Kordas, K; Korn, A; Korytov, A; Kotelnikov, K; Kotwal, A V; Kovalev, A; Kraus, J; Kravchenko, I; Kreymer, A; Kroll, J; Kruse, M; Krutelyov, V; Kuhlmann, S E; Kuznetsova, N; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, J; Lancaster, M; Lander, R; Lannon, K; Lath, A; Latino, G; Lauhakangas, R; Lazzizzera, I; Le, Y; Lecci, C; Lecompte, T; Lee, J; Lee, J; Lee, S W; Lefevre, R; Leonardo, N; Leone, S; Lewis, J D; Li, K; Lin, C; Lin, C S; Lindgren, M; Liss, T M; Litvintsev, D O; Liu, T; Liu, Y; Lockyer, N S; Loginov, A; Loreti, M; Loverre, P; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Macqueen, D; Madrak, R; Maeshima, K; Maksimovic, P; Malferrari, L; Manca, G; Marginean, R; Martin, M; Martin, A; Martin, V; Martínez, M; Maruyama, T; Matsunaga, H; Mattson, M; Mazzanti, P; McFarland, K S; McGivern, D; McIntyre, P M; McNamara, P; NcNulty, R; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; Miao, T; Miladinovic, N; Miller, L; Miller, R; Miller, J S; Miquel, R; Miscetti, S; Mitselmakher, G; Miyamoto, A; Miyazaki, Y; Moggi, N; Mohr, B; Moore, R; Morello, M; Mukherjee, A; Mulhearn, M; Muller, T; Mumford, R; Munar, A; Murat, P; Nachtman, J; Nahn, S; Nakamura, I; Nakano, I; Napier, A; Napora, R; Naumov, D; Necula, V; Niell, F; Nielsen, J; Nelson, C; Nelson, T; Neu, C; Neubauer, M S; Newman-Holmes, C; Nicollerat, A-S; Nigmanov, T; Nodulman, L; Norniella, O; Oesterberg, K; Ogawa, T; Oh, S H; Oh, Y D; Ohsugi, T; Okusawa, T; Oldeman, R; Orava, R; Orejudos, W; Pagliarone, C; Palencia, E; Palmonari, F; Paoletti, R; Papadimitriou, V; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Pauly, T; Paus, C; Pellett, D; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pitts, K T; Plager, C; Pompos, A; Pondrom, L; Pope, G; Poukhov, O; Prakoshyn, F; Pratt, T; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Rademacker, J; Rakitine, A; Rappoccio, S; Ratnikov, F; Ray, H; Reichold, A; Reisert, B; Rekovic, V; Renton, P; Rescigno, M; Rimondi, F; Rinnert, K; Ristori, L; Robertson, W J; Robson, A; Rodrigo, T; Rolli, S; Rosenson, L; Roser, R; Rossin, R; Rott, C; Russ, J; Ruiz, A; Ryan, D; Saarikko, H; Sabik, S; Safonov, A; St Denis, R; Sakumoto, W K; Salamanna, G; Saltzberg, D; Sanchez, C; Sansoni, A; Santi, L; Sarkar, S; Sato, K; Savard, P; Savoy-Navarro, A; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Scodellaro, L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semeria, F; Sexton-Kennedy, L; Sfiligoi, I; Shapiro, M D; Shears, T; Shepard, P F; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Siegrist, J; Siket, M; Sill, A; Sinervo, P; Sisakyan, A; Skiba, A; Slaughter, A J; Sliwa, K; Smirnov, D; Smith, J R; Snider, F D; Snihur, R; Somalwar, S V; Spalding, J; Spezziga, M; Spiegel, L; Spinella, F; Spiropulu, M; Squillacioti, P; Stadie, H; Stefanini, A; Stelzer, B; Stelzer-Chilton, O; Strologas, J; Stuart, D; Sukhanov, A; Sumorok, K; Sun, H; Suzuki, T; Taffard, A; Tafirout, R; Takach, S F; Takano, H; Takashima, R; Takeuchi, Y; Takikawa, K; Tanaka, M; Tanaka, R; Tanimoto, N; Tapprogge, S; Tecchio, M; Teng, P K; Terashi, K; Tesarek, R J; Tether, S; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tollefson, K; Tomura, T; Tonelli, D; Tönnesmann, M; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tseng, J; Tsuchiya, R; Tsuno, S; Tsybychev, D; Turini, N; Turner, M; Ukegawa, F; Unverhau, T; Uozumi, S; Usynin, D; Vacavant, L; Vaiciulis, A; Varganov, A; Vataga, E; Vejcik, S; Velev, G; Veszpremi, V; Veramendi, G; Vickey, T; Vidal, R; Vila, I; Vilar, R; Vollrath, I; Volobouev, I; von der Mey, M; Wagner, P; Wagner, R G; Wagner, R L; Wagner, W; Wallny, R; Walter, T; Yamashita, T; Yamamoto, K; Wan, Z; Wang, M J; Wang, S M; Warburton, A; Ward, B; Waschke, S; Waters, D; Watts, T; Weber, M; Wester, W C; Whitehouse, B; Wicklund, A B; Wicklund, E; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolter, M; Worcester, M; Worm, S; Wright, T; Wu, X; Würthwein, F; Wyatt, A; Yagil, A; Yang, U K; Yao, W; Yeh, G P; Yi, K; Yoh, J; Yoon, P; Yorita, K; Yoshida, T; Yu, I; Yu, S; Yu, Z; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zetti, F; Zhou, J; Zsenei, A; Zucchelli, S

    2005-03-18

    We present a search for excited and exotic electrons (e(*)) decaying to an electron and a photon, both with high transverse momentum. We use 202 pb(-1) of data collected in pp collisions at sqrt[s] = 1.96 TeV with the Collider Detector at Fermilab II detector. No signal above standard model expectation is seen for associated ee(*) production. We discuss the e(*) sensitivity in the parameter space of the excited electron mass M(e(*)) and the compositeness energy scale Lambda. In the contact interaction model, we exclude 132 GeV/c(2)

  16. MARKETING CHANNELS

    Directory of Open Access Journals (Sweden)

    Ljiljana Stošić Mihajlović

    2014-07-01

    Full Text Available Marketing channel is a set of entities and institutions, completion of distribution and marketing activities, attend the efficient and effective networking of producers and consumers. Marketing channels include the total flows of goods, money and information taking place between the institutions in the system of marketing, establishing a connection between them. The functions of the exchange, the physical supply and service activities, inherent in the system of marketing and trade. They represent paths which products and services are moving after the production, which will ultimately end up buying and eating by the user.

  17. Agglomeration of ceramic powders

    Science.gov (United States)

    Cawley, James D.; Larosa, Judith; Dirkse, Fredrick

    1989-01-01

    A research program directed at a critical comparison of numerical models for power agglomeration with experimental observations is currently underway. Central to this program is the quantitative characterization of the distribution of mass within an agglomerate as a function of time. Current experiments are designed to restrict agglomeration to a surface, which is oriented perpendicular to the force of gravity. These experiments are discussed with reference to: their significance to ceramic processing; artifacts which may be avoided in microgravity experiments; and the comparison of information available in real space (from optical microscopy) to that in reciprocal space (from light scattering). The principle machine requirement appears to be a need to obtain information at small scattering angles.

  18. [Cytocompatibility of two porous bioactive glass-ceramic in vitro].

    Science.gov (United States)

    Zhang, Yan; Jiang, Xinquan; Zhang, Xiuli; Wang, Deping; Zhen, Lei

    2013-06-01

    To compare the cytocompatibility of two kinds porous bioactive glass-ceramic made by same raw materials. Apatite/wollastonite bioactive glass-ceramic (4006) were prepared by sol-gel method, and bioactive glass (45S5) were prepared by melting method. Bone marrow stromal cells (BMSCs) were cultivated, differentiated and proliferated into osteoblasts, from a rabbit's marrow in the differentiatiofn culture medium with active function. The viability of BMSCs cultivated with extraction of these two kinds of biomaterial, which could represent the cytotoxicity effect of 4006 and 45S5 against BMSCs, was evaluated by the MTp assay. BMSCs were seeded and cocultivated with two kinds of biomaterial scaffolds respectively in vitro. The proliferation and biological properties of cells adhered to scaffolds were observed by inverted phase contrast microscope, scanning electron microscope (SEM), and environmental scanning electron microscope (ESEM), and a suitable cell amount for seeding on the scaffold was searched. There was no difference on the viability of BMSCs only cultured for one day by complete extract of 4006 and culture medium (P>0.05), but there was significant difference between them when the cells had been cultured for 3 days(Pglass-ceramic has good bioactivity and cytocompatibility. Therefore, it may have the potential to be a new cell vehicle for bone tissue engineering. And the suitable seeding cell amount of apatite/wollastonite bioactive glass-ceramic should be 2x10(7) cells.mL-1 or even more than that.

  19. Survival of resin infiltrated ceramics under influence of fatigue.

    Science.gov (United States)

    Aboushelib, Moustafa N; Elsafi, Mohamed H

    2016-04-01

    to evaluate influence of cyclic fatigue on two resin infiltrated ceramics and three all-ceramic crowns manufactured using CAD/CAM technology. CAD/CAM anatomically shaped crowns were manufactured using two resin infiltrated ceramics (Lava Ultimate and Vita Enamic), two reinforced glass ceramic milling blocks ((IPS)Empress CAD and (IPS)e.max CAD) and a veneered zirconia core ((IPS)Zir CAD). (IPS)e.max CAD and (IPS)Zir CAD were milled into 0.5mm thick anatomically shaped core structure which received standardized press-on veneer ceramic. The manufactured crowns were cemented on standardized resin dies using a resin adhesive (Panavia F2.0). Initial fracture strength of half of the specimens was calculated using one cycle load to failure in a universal testing machine. The remaining crowns were subjected to 3.7 million chewing cycles (load range 50-200N at 3s interval) in a custom made pneumatic fatigue tester. Survival statistics were calculated and Weibull modulus was measured from fitted load-cycle-failure diagrams. Scanning electron microscopy was performed to fractographically analyze fractured surfaces. Data were analyzed using two way analysis of variance and Bonferroni post hoc tests (α=0.05). Dynamic fatigue resulted in significant reduction (F=7.54, Presin infiltrated ceramics and (IPS)Empress demonstrated the highest percent of fracture incidences under the influence of fatigue (35-45% splitting). None of the tested veneered zirconia restorations were fractured during testing, however, chipping of the veneer ceramics was observed in 6 crowns. The lowest percent of failure was observed for (IPS)e.max crowns manifested as 3 cases of minor chipping in addition to two complete fracture incidences. SEM images demonstrated the internal structure of the tested materials and detected location and size of the critical crack. The internal structure of the tested materials significantly influenced their fatigue behavior. Resin infiltrated ceramics were least influenced

  20. Storing Waste in Ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Bourcier, W L; Sickafus, K

    2004-07-20

    Not all the nuclear waste destined for Yucca Mountain is in the form of spent fuel. Some of it will be radioactive waste generated from the production of nuclear weapons. This so-called defense waste exists mainly as corrosive liquids and sludge in underground tanks. An essential task of the U.S. high-level radioactive waste program is to process these defense wastes into a solid material--called a waste form. An ideal waste form would be extremely durable and unreactive with other repository materials. It would be simple to fabricate remotely so that it could be safely transported to a repository for permanent storage. What's more, the material should be able to tolerate exposure to intense radiation without degradation. And to minimize waste volume, the material must be able to contain high concentrations of radionuclides. The material most likely to be used for immobilization of radioactive waste is glass. Glasses are produced by rapid cooling of high-temperature liquids such that the liquid-like non-periodic structure is preserved at lower temperatures. This rapid cooling does not allow enough time for thermodynamically stable crystalline phases (mineral species) to form. In spite of their thermodynamic instability, glasses can persist for millions of years. An alternate to glass is a ceramic waste form--an assemblage of mineral-like crystalline solids that incorporate radionuclides into their structures. The crystalline phases are thermodynamically stable at the temperature of their synthesis; ceramics therefore tend to be more durable than glasses. Ceramic waste forms are fabricated at temperatures below their melting points and so avoid the danger of handling molten radioactive liquid--a danger that exists with incorporation of waste in glasses. The waste form provides a repository's first line of defense against release of radionuclides. It, along with the canister, is the barrier in the repository over which we have the most control. When a waste

  1. Inorganic glass ceramic slip rings

    Science.gov (United States)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  2. Low Thermal Expansion Glass Ceramics

    CERN Document Server

    Bach, Hans

    2005-01-01

    This book appears in the authoritative series reporting the international research and development activities conducted by the Schott group of companies. This series provides an overview of Schott's activities for scientists, engineers, and managers from all branches of industry worldwide in which glasses and glass ceramics are of interest. Each volume begins with a chapter providing a general idea of the current problems, results, and trends relating to the subjects treated. This new extended edition describes the fundamental principles, the manufacturing process, and applications of low thermal expansion glass ceramics. The composition, structure, and stability of polycrystalline materials having a low thermal expansion are described, and it is shown how low thermal expansion glass ceramics can be manufactured from appropriately chosen glass compositions. Examples illustrate the formation of this type of glass ceramic by utilizing normal production processes together with controlled crystallization. Thus g...

  3. ceramics by differential scanning calorimetry

    Indian Academy of Sciences (India)

    Administrator

    YbxGd2–xZr2O7 (x = 0, 1, 2) ceramics were pressureless-sintered using ceramic powders acquired by chemical-coprecipitation and calcination methods. Heat capacities of YbxGd2–xZr2O7 were measured with a heat flux-type differential scanning calorimetry in the temperature range of 298–1200 K. At 298 K, the heat.

  4. Nonlinear fracture of concrete and ceramics

    Science.gov (United States)

    Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

    1989-01-01

    The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

  5. The role of AlGaN buffers and channel thickness in the electronic transport properties of Al x In1- x N/AlN/GaN heterostructures

    Science.gov (United States)

    Amirabbasi, M.

    2016-01-01

    We try to theoretically analyze the reported experimental data of the Al x In1- x N/AlN/GaN heterostructures grown by MOCVD and quantitatively investigate the effects of AlGaN buffers and the GaNchannel thickness on the electrical transport properties of these systems. Also, we obtain the most important effective parameters of the temperature-dependent mobility in the range 35-300 K. Our results show that inserting a 1.1 μm thick Al0.04Ga0.96N buffer enhances electron mobility by decreasing the effect of phonons, the interface roughness, and dislocation and crystal defect scattering mechanisms. Also, as the channel thickness increases from 20 nm to 40 nm, the electron mobility increases from 2200 to 2540 cm2/(V s) and from 870 to 1000 cm2/(V s) at 35 and 300 K respectively, which is attributed to the reduction in the dislocation density and the strain-induced field. Finally, the reported experimental data show that inserting a 450 nm graded AlGaN layer before an Al0.04Ga0.96N buffer causes a decrease in the electron mobility, which is attributed to the enhancement of the lateral size of roughness, the dislocation density, and the strain-induced field in this sample.

  6. Structural, thermal, and optical properties of Er3+/Yb3+ co-doped oxyhalide tellurite glasses, glass-ceramics and ceramics

    Science.gov (United States)

    Joshi, C.; Rai, R. N.; Rai, S. B.

    2012-04-01

    Glass-ceramics and ceramics containing nano-crystals of different phases doped with Er3+/Yb3+ ions have been successfully prepared by heat treatment of the precursor oxyhalide glasses synthesized by the melt-quench method. X-ray diffraction patterns and transmission electron microscopy (TEM) images verify the precipitation of nano-crystals. Emission of Er3+ enhances several times when Yb3+ ion is added with the matrix. The Stark splitting and the intensity of different emission bands increase to a great extent when we approach to ceramics from glasses via glass-ceramics. The intensity of the blue and green emission bands increases much faster than the red and NIR emission bands. Intense upconversion emission observed by the naked eye has been quantified in terms of standard chromaticity diagram (CIE). Power dependence study shows that the upconversion of NIR radiation to visible radiation takes place mainly via photon avalanche (PA) process.

  7. A combined SEM, CV and EIS study of multi-layered porous ceramic reactors for flue gas purification

    DEFF Research Database (Denmark)

    He, Zeming; Andersen, Kjeld Bøhm; Nygaard, Frederik Berg

    2013-01-01

    The effect of sintering temperature of 12-layered porous ceramic reactors (comprising 5 cells) was studied using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The difference in microstructures of the reactors was evaluated by SEM...

  8. Wiggler Effects on the Growth Rate of a Raman Free-electron Laser with Axial Magnetic Field or Ion-Channel Guiding

    CERN Document Server

    Maraghechi, Behrouz

    2004-01-01

    A relativistic theory for Raman backscattering in the beam frame of electrons is presented and is used to find the growth rate of a free-electron laser (FEL), in the Raman regime. A one dimensional helical wiggler and an axial magnetic field are considered. The effects of static self-electric and self-magnetic fields, induced by the steady-state charge density and currents of the non-neutral electron beam, are taken into account to find the steady-state trajectories. The wiggler effects on the linear dispersion relations of the space-charge wave and radiation are included in the analysis. A numerical computation is conducted to compare the growth rate of the excited waves with nonrelativistic treatment. It was found that self-field effects increase the growth rate in the group II orbits and decrease it in the group I orbits. However, the wiggler effects on growth rate are stronger and increase the growth rate on both group I and group II orbits. The discontinuity, due to the cyclotron resonance with the radia...

  9. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key

  10. Measurement of the Top Quark Pair Production Cross Section in the Electron and Jets Channel at $\\sqrt{s}$ = 7 TeV with the CMS Detector at the LHC

    CERN Document Server

    Klein, Benjamin

    The top quark is the heaviest fundamental particle observed in nature. The high mass leads to its decay before a hadronisation takes place which allows the measurement of its properties from the decay products. Measurements of the properties of the top quark allow for precision tests of the Standard Model of particle physics. Furthermore, top quark production is a dominant background in many searches for physics beyond the Standard Model. The Large Hadron Collider (LHC) is a high-energy particle accelerator at the European Organisation for Nuclear Research (CERN) near Geneva, Switzerland. Proton-proton collisions are recorded and analysed with several large scale detectors, one of them is the Compact Muon Solenoid (CMS) detector. This thesis presents a precision measurement of the top quark pair production cross section in the semi-leptonic electron and jets decay channel with the CMS detector at the LHC. Detailed studies of lepton identification and trigger algorithm efficiencies are summarised as they are c...

  11. Chemical characterization of marajoara ceramics; Caracterizacao quimica da ceramica marajoara

    Energy Technology Data Exchange (ETDEWEB)

    Toyota, Rosimeiri Galbiati

    2009-07-01

    In this study the elemental concentration of Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn were determined by instrumental neutron activation analysis (INAA) in 204 fragments of Marajoara archaeological ceramics, of which 156 were provided by the Archaeology and Ethnology Museum of Sao Paulo University (MAE) and 48 were provided by Dr. Denise Pahl Schaan, Marajo Museum curator. Also, 9 contemporary ceramics produced and marketed at Marajo Island were analyzed. Electron paramagnetic resonance (EPR) analyses were performed in 8 archaeological samples and 1 contemporary sample in order to identify the burning temperature of the samples. X-ray diffraction (XRD) analyses were performed in 13 archaeological samples and 2 contemporary samples for the investigation of their mineralogical composition. Mahalanobis distance was used for the study of outlier while modified filter was used for the study of the temper added to the ceramic paste. Result interpretation was performed using cluster analysis, principal components analysis and discriminant analysis. Procrustes analysis was used for variable selection and it showed that the Ce, Fe, Eu, Hf, K and Th variables are adequate for the characterization of the analyzed samples. The comparative study among the archaeological and contemporary ceramics showed the arrangement of two well-defined and close groups for the archaeological samples and a third, distant group for the contemporary ones. This result indicates that the archaeological and contemporary ceramics differ in their composition. EPR and XRD analysis were inconclusive for the differentiation of archaeological and contemporary ceramics. (author)

  12. Nano-Ceramic Coated Plastics

    Science.gov (United States)

    Cho, Junghyun

    2013-01-01

    Plastic products, due to their durability, safety, and low manufacturing cost, are now rapidly replacing cookware items traditionally made of glass and ceramics. Despite this trend, some still prefer relatively expensive and more fragile ceramic/glassware because plastics can deteriorate over time after exposure to foods, which can generate odors, bad appearance, and/or color change. Nano-ceramic coatings can eliminate these drawbacks while still retaining the advantages of the plastic, since the coating only alters the surface of the plastic. The surface coating adds functionality to the plastics such as self-cleaning and disinfectant capabilities that result from a photocatalytic effect of certain ceramic systems. These ceramic coatings can also provide non-stick surfaces and higher temperature capabilities for the base plastics without resorting to ceramic or glass materials. Titanium dioxide (TiO2) and zinc oxide (ZnO) are the candidates for a nano-ceramic coating to deposit on the plastics or plastic films used in cookware and kitchenware. Both are wide-bandgap semiconductors (3.0 to 3.2 eV for TiO2 and 3.2 to 3.3 eV for ZnO), so they exhibit a photocatalytic property under ultraviolet (UV) light. This will lead to decomposition of organic compounds. Decomposed products can be easily washed off by water, so the use of detergents will be minimal. High-crystalline film with large surface area for the reaction is essential to guarantee good photocatalytic performance of these oxides. Low-temperature processing (plastics. One possible way of processing nanoceramic coatings at low temperatures (plastic materials (silicone, Teflon, PET, etc.) that can possess both photocatalytic oxide properties and flexible plastic properties. Processing cost is low and it does not require any expensive equipment investment. Processing can be scalable to current manufacturing infrastructure.

  13. Cracks in nano-ceramic thin layers produced by laser treatments

    NARCIS (Netherlands)

    De Hosson, JTM; Teeuw, DHJ; Beltz, GE; Selinger, RLB; Kim, KS; Marder, MP

    1999-01-01

    Sol-gel derived thin nano-ceramic layers of TiO2 and Al2O3 are studied using scanning electron microscopy to reveal the microstructure and morphologies of the layers. The low-voltage scanning electron microscope with a field emission gun is equipped with an especially designed lens, where the

  14. Ordered ceramic membranes

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, M.A.; Hill, C.G. Jr.; Zeltner, W.A.

    1991-10-01

    Ceramic membranes have been formed from colloidal sols coated on porous clay supports. These supported membranes have been characterized in terms of their permeabilities and permselectivities to various aqueous test solutions. The thermal stabilities and pore structures of these membranes have been characterized by preparing unsupported membranes of the correpsonding material and performing N{sub 2} adsorption-desorption and X-ray diffraction studies on these membranes. To date, membranes have been prepared from a variety of oxides, including TiO{sub 2}, SiO{sub 2}, ZrO{sub 2}, and Al{sub 2}O{sub 3}, as well as Zr-, Fe-, and Nb-doped TiO{sub 2}. In many of these membranes pore diameters are less than 2 nm, while in others the pore diameters are between 3 and 5 nm. Procedures for fabricating porous clay supports with reproducible permeabilities for pure water are also discussed. 30 refs., 59 figs., 22 tabs.

  15. Ceramic HEPA Filter Program

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, M A; Bergman, W; Haslam, J; Brown, E P; Sawyer, S; Beaulieu, R; Althouse, P; Meike, A

    2012-04-30

    Potential benefits of ceramic filters in nuclear facilities: (1) Short term benefit for DOE, NRC, and industry - (a) CalPoly HTTU provides unique testing capability to answer questions for DOE - High temperature testing of materials, components, filter, (b) Several DNFSB correspondences and presentations by DNFSB members have highlighted the need for HEPA filter R and D - DNFSB Recommendation 2009-2 highlighted a nuclear facility response to an evaluation basis earthquake followed by a fire (aka shake-n-bake) and CalPoly has capability for a shake-n-bake test; (2) Intermediate term benefit for DOE and industry - (a) Filtration for specialty applications, e.g., explosive applications at Nevada, (b) Spin-off technologies applicable to other commercial industries; and (3) Long term benefit for DOE, NRC, and industry - (a) Across industry, strong desire for better performance filter, (b) Engineering solution to safety problem will improve facility safety and decrease dependence on associated support systems, (c) Large potential life-cycle cost savings, and (d) Facilitates development and deployment of LLNL process innovations to allow continuous ventilation system operation during a fire.

  16. On Shor's Channel Extension and Constrained Channels

    Science.gov (United States)

    Holevo, A. S.; Shirokov, M. E.

    Several equivalent formulations of the additivity conjecture for constrained channels, which formally is substantially stronger than the unconstrained additivity, are given. To this end a characteristic property of the optimal ensemble for such a channel is derived, generalizing the maximal distance property. It is shown that the additivity conjecture for constrained channels holds true for certain nontrivial classes of channels. After giving an algebraic formulation for Shor's channel extension, its main asymptotic property is proved. It is then used to show that additivity for two constrained channels can be reduced to the same problem for unconstrained channels, and hence, ``global'' additivity for channels with arbitrary constraints is equivalent to additivity without constraints.

  17. III Advanced Ceramics and Applications Conference

    CERN Document Server

    Gadow, Rainer; Mitic, Vojislav; Obradovic, Nina

    2016-01-01

    This is the Proceedings of III Advanced Ceramics and Applications conference, held in Belgrade, Serbia in 2014. It contains 25 papers on various subjects regarding preparation, characterization and application of advanced ceramic materials.

  18. Reliability of ceramics for heat engine applications

    Science.gov (United States)

    1980-01-01

    The advantages and disadvantages associated with the use of monolithic ceramics in heat engines are discussed. The principle gaps in the state of understanding of ceramic material, failure origins, nondestructive tests as well as life prediction are included.

  19. Panel report on high temperature ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Nolet, T C [ed.

    1979-01-01

    Fundamental research is reported concerning high temperature ceramics for application in turbines, engines, batteries, gasifiers, MHD, fuel cells, heat exchangers, and hot wall combustors. Ceramics microstructure and behavior are included. (FS)

  20. Incorporation of Waste Ceramic Blocks in Structural Ceramics

    Science.gov (United States)

    de Oliveira, Orley Magalhães; das Graças da Silva-Valenzuela, Maria; Andrade, Christiano Gianesi Bastos; Junior, Antonio Hortêncio Munhoz; Valenzuela-Díaz, Francisco Rolando

    In Brazil, Ceramics Industries produce bricks and ceramic tiles in practically all the country. In the southwestern region of Bahia are located some of these industries. A considerable proportion of the material produced do not pass the quality control for not having a uniform visual appearance or have cracks. These burned pieces are generally discarded, resulting in a big quantity of waste. The objective of this work is the characterization of this industrial waste and thus consign them to other industrial applications. Our results demonstrate that the burned waste have potential to be used for incorporation in common clay for structural ceramics, thereby avoiding its disposal in nature and reducing this environmental liability. Experimental bodies were tested with different quantities of waste. The common clay and the burned waste were characterized by XRD, TG/DTA, and SEM. The burned specimens were tested for mechanical strength, water absorption, bulk density, and apparent porosity. An incorporation of 10% of waste furnished the best results.

  1. High flow ceramic pot filters.

    Science.gov (United States)

    van Halem, D; van der Laan, H; Soppe, A I A; Heijman, S G J

    2017-11-01

    Ceramic pot filters are considered safe, robust and appropriate technologies, but there is a general consensus that water revenues are limited due to clogging of the ceramic element. The objective of this study was to investigate the potential of high flow ceramic pot filters to produce more water without sacrificing their microbial removal efficacy. High flow pot filters, produced by increasing the rice husk content, had a higher initial flow rate (6-19 L h-1), but initial LRVs for E. coli of high flow filters was slightly lower than for regular ceramic pot filters. This disadvantage was, however, only temporarily as the clogging in high flow filters had a positive effect on the LRV for E. coli (from below 1 to 2-3 after clogging). Therefore, it can be carefully concluded that regular ceramic pot filters perform better initially, but after clogging, the high flow filters have a higher flow rate as well as a higher LRV for E. coli. To improve the initial performance of new high flow filters, it is recommended to further utilize residence time of the water in the receptacle, since additional E. coli inactivation was observed during overnight storage. Although a relationship was observed between flow rate and LRV of MS2 bacteriophages, both regular and high flow filters were unable to reach over 2 LRV. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. The effect of hydrofluoric acid surface treatment and bond strength of a zirconia veneering ceramic.

    Science.gov (United States)

    Chaiyabutr, Yada; McGowan, Steve; Phillips, Keith M; Kois, John C; Giordano, Russell A

    2008-09-01

    Clinicians are frequently faced with a challenge in selecting materials for adjacent restorations, particularly when one tooth requires a zirconia-based restoration and the next requires a veneer. While it may be desirable to use the same veneering ceramic on adjacent teeth, little information is available about the use of veneering ceramics over a zirconia-based material. The purpose of this study was threefold: (1) to study the influence of hydrofluoric acid-etched treatment on the surface topography of the zirconia veneering ceramic, (2) to test the bond strength of zirconia veneering ceramic to enamel, and (3) to evaluate the flexural strength and the elemental composition of ceramic veneers. Three zirconia veneering ceramics (Cerabien CZR (CZ), Lava Ceram (L), and Zirox (Z)) and 4 conventional veneering ceramics (Creation (C), IPS d.Sign (D), Noritake EX-3 (E), and Reflex (R)) were evaluated. Twenty ceramic bars of each material were fabricated and surface treated with hydrofluoric acid according to the manufacturer's recommendations. Ten specimens from each group of materials were examined with a profilometer, and a sample of this group was selected for quantitative evaluation using a scanning electron microscope (SEM). Another 10 acid-etched specimens from each group of materials were treated with silane prior to cementing with resin cement (Variolink II) on enamel surfaces. These luted specimens were loaded to failure in a universal testing machine in the shear mode with a crosshead speed of 0.05 mm/min. The data were analyzed with a 1-way ANOVA, followed by Tukey's HSD test (alpha=.05). An additional 10 ceramic bars from each material group were fabricated to evaluate flexural strength and elemental composition. The flexural strength (MPa) of each specimen was determined by using a 4-point-1/4-point flexure test. A Weibull statistic tested the reliability of the strength data; pairwise differences among the 7 groups were evaluated at confidence intervals

  3. Ceramic cutting tools materials, development and performance

    CERN Document Server

    Whitney, E Dow

    1994-01-01

    Interest in ceramics as a high speed cutting tool material is based primarily on favorable material properties. As a class of materials, ceramics possess high melting points, excellent hardness and good wear resistance. Unlike most metals, hardness levels in ceramics generally remain high at elevated temperatures which means that cutting tip integrity is relatively unaffected at high cutting speeds. Ceramics are also chemically inert against most workmetals.

  4. Emerging Ceramic-based Materials for Dentistry

    Science.gov (United States)

    Denry, I.; Kelly, J.R.

    2014-01-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  5. Crystallization of high-strength nano-scale leucite glass-ceramics.

    Science.gov (United States)

    Theocharopoulos, A; Chen, X; Wilson, R M; Hill, R; Cattell, M J

    2013-11-01

    Fine-grained, high strength, translucent leucite dental glass-ceramics are synthesized via controlled crystallization of finely milled glass powders. The objectives of this study were to utilize high speed planetary milling of an aluminosilicate glass for controlled surface crystallization of nano-scale leucite glass-ceramics and to test the biaxial flexural strength. An aluminosilicate glass was synthesized, attritor or planetary milled and heat-treated. Glasses and glass-ceramics were characterized using particle size analysis, X-ray diffraction and scanning electron microscopy. Experimental (fine and nanoscale) and commercial (Ceramco-3, IPS Empress Esthetic) leucite glass-ceramics were tested using the biaxial flexural strength (BFS) test. Gaussian and Weibull statistics were applied. Experimental planetary milled glass-ceramics showed an increased leucite crystal number and nano-scale median crystal sizes (0.048-0.055 μm(2)) as a result of glass particle size reduction and heat treatments. Experimental materials had significantly (p0.05) strength difference. All other groups' mean BFS and characteristic strengths were found to be significantly different (pglass-ceramics with high flexural strength. These materials may help to reduce problems associated with brittle fracture of all-ceramic restorations and give reduced enamel wear. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. Synthesis of nucleated glass-ceramics using oil shale fly ash.

    Science.gov (United States)

    Luan, Jingde; Li, Aimin; Su, Tong; Cui, Xiaobo

    2010-01-15

    Nucleated glass-ceramics materials were produced from oil shale fly ash obtained from Huadian thermal power plant in China with the addition of analytic reagent CaO. On basis of differential thermal analysis (DTA) results, the nucleation and crystallization temperature of two parent glass samples with different alkalinity (Ak=m(CaO)/m(SiO(2)) were identified as Tn(1)=810 degrees C, Tc(1)=956 degrees C and Tn(2)=824 degrees C, Tc(2)=966 degrees C, respectively. X-ray diffraction (XRD) analysis of the produced nucleated glass-ceramics materials revealed that there was a coexistence phenomenon of multi-crystalline phase and the main crystalline phase was anorthite ([Ca,Na][AI,Si](2)Si(2)O(8)). The microstructure of the glass-ceramics materials was examined by scanning electron microscope (SEM). SEM observation indicated that there was an increase in the quantity of sphere-shaped crystals when crystallization time increased. Furthermore, the increase of alkalinity caused more amorphous phase occurring in glass-ceramics materials. Through the tests of physical and mechanical properties, the glass-ceramics materials with more crystalline phase and fine microstructure had high density, fine performance of resisting compression (328.92 MPa) and negligible water absorption. Through chemical resistance tests, the glass-ceramics samples showed strong corrosion resistance. Overall results indicated that it was a feasible attempt to produce nucleated glass-ceramics materials for building and decorative materials from oil shale fly ash.

  7. Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns.

    Science.gov (United States)

    Choi, Jae-Won; Bae, Ik-Hyun; Noh, Tae-Hwan; Ju, Sung-Won; Lee, Tae-Kyoung; Ahn, Jin-Soo; Jeong, Tae-Sung; Huh, Jung-Bo

    2016-02-01

    This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear. There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey's test (PSteel groups (0.397±0.192 mm(3)). Mean volume losses in the Leucite and Lithium groups were significantly greater than in the Steel group (PSteel groups (P>.05). Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia.

  8. Wear of primary teeth caused by opposed all-ceramic or stainless steel crowns

    Science.gov (United States)

    Bae, Ik-Hyun; Noh, Tae-Hwan; Ju, Sung-Won; Lee, Tae-Kyoung; Ahn, Jin-Soo; Jeong, Tae-Sung

    2016-01-01

    PURPOSE This study was conducted to evaluate the effects of full-coverage all-ceramic zirconia, lithium disilicate glass-ceramic, leucite glass-ceramic, or stainless steel crowns on antagonistic primary tooth wear. MATERIALS AND METHODS There were four study groups: the stainless steel (Steel) group, the leucite glass-ceramic (Leucite) group, the lithium disilicate glass-ceramic (Lithium) group, and the monolithic zirconia (Zirconia) group. Ten flat crown specimens were prepared per group; opposing teeth were prepared using primary canines. A wear test was conducted over 100,000 chewing cycles using a dual-axis chewing simulator and a 50 N masticating force, and wear losses of antagonistic teeth and restorative materials were calculated using a three-dimensional profiling system and an electronic scale, respectively. Statistical significance was determined using One-way ANOVA and Tukey's test (P.05). CONCLUSION Leucite glass-ceramic and lithium disilicate glass-ceramic cause more primary tooth wear than stainless steel or zirconia. PMID:26949487

  9. Effects of ageing on surface textures of veneering ceramics for zirconia frameworks.

    Science.gov (United States)

    Tang, Xuehua; Tan, Zhenquan; Nakamura, Takashi; Yatani, Hirofumi

    2012-11-01

    To evaluate the effects of ageing on surface textures of veneering ceramics for zirconia frameworks. Five different veneering ceramics for zirconia frameworks, Vintage ZR (ZR), Cerabien ZR (CZR), VitaVM9 (VM9), Cercon ceram KISS (KISS), and IPS e.max ceram (e.max), and one veneering ceramic with metal frameworks, Vintage MP (MP), were evaluated. Twenty specimens were fabricated from each veneering ceramic. All specimens were divided into two groups, one of which was subjected to accelerated ageing. The other was used as the control. Accelerated ageing was performed on the distilled water for 5h at 200°C and 2 atm. Surface textures were examined using laser profilometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Compared to unaged specimens, surface roughness parameters (Ra, Rp, Rv) of all aged specimens except e.max were significantly greater (P=0.000). Compared to the unaged specimens, sodium and potassium on the surfaces of all the aged specimens significantly decreased (Pveneering ceramics were changed by the accelerated ageing test. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Interaction phenomena at reactive metal/ceramic interfaces.

    Energy Technology Data Exchange (ETDEWEB)

    McDeavitt, S. M.; Billings, G. W.; Indacochea, J. E.

    2000-11-03

    The objective of this study was to understand the interface chemical reactions between stable ceramics and reactive liquid metals, and developing microstructure. Experiments were conducted at elevated temperatures where small metal samples of Zr and Zr-alloy were placed on top of selected oxide and non-oxide ceramic substrates (Y{sub 2}O{sub 3}, ZrN, ZrC, and HfC). The sample stage was heated in high-purity argon to about 2000 C, held in most cases for five minutes at the peak temperature, and then cooled to room temperature at {approximately}20 c/min. An external video camera was used to monitor the in-situ wetting and interface reactions. Post-test examinations of the systems were conducted by scanning electron microscopy and energy dispersive spectroscopy. It was determined that the Zr and the Zr-alloy are very active in the wetting of stable ceramics at elevated temperatures. In addition, in some systems, such as Zr/ZrN, a reactive transition phase formed between the ceramic and the metal. In other systems, such as Zr/Y{sub 2}O{sub 3}, Zr/ZrC and Zr/HfC, no reaction products formed, but a continuous and strong joint developed under these circumstances also.

  11. Wear performance of monolithic dental ceramics with different surface treatments.

    Science.gov (United States)

    Preis, Verena; Weiser, Felix; Handel, Gerhard; Rosentritt, Martin

    2013-05-01

    To investigate the two-body wear performance of monolithic dental ceramics with different surface treatments. Standardized specimens (n = 8/ series) were fabricated from three monolithic dental ceramics (experimental translucent zirconia, experimental shaded zirconia, lithium disilicate). Four groups of each material were defined according to clinically relevant surface treatments: polished, polishedground, polished-ground-repolished, glazed. Two-body wear tests with steatite antagonists were performed in a chewing simulator. Surface roughness (R(a)) was controlled, and wear depths of specimens and antagonistic wear areas were calculated in relation to human enamel as reference. Statistical analysis of wear data was carried out using one-way ANOVA and Bonferroni multiple comparison test for post hoc analysis (α = .05). Scanning electron microscopy was applied for evaluating wear performance of ceramics and antagonists. Polished, ground, and repolished zirconia showed no wear, while glaze was abraded. Irrespective of the surface treatment, wear depth of lithium disilicate was significantly (P grinding and glazing. Steatite surfaces were smooth when opposed to polished/ground/repolished zirconia, and ploughed when opposed to glaze and lithium disilicate. Translucent and shaded experimental zirconia yielded superior wear behavior and lower antagonistic wear compared to lithium disilicate. A trend to higher ceramic and antagonistic wear was shown after grinding and glazing.

  12. Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.

    Science.gov (United States)

    Mesquita, A M M; Ozcan, M; Souza, R O A; Kojima, A N; Nishioka, R S; Kimpara, E T; Bottino, M A

    2010-01-01

    This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions. Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 ºC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05). Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic. Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.

  13. Ablation Resistant Zirconium and Hafnium Ceramics

    Science.gov (United States)

    Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

    1998-01-01

    High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

  14. Ceramic microfabrication by rapid prototyping process chains

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    fast and inexpensive supply for polymer master models and a ceramic shaping method that enables the replication of the RP model into multiple ceramic materials within a short time. (Knitter et al 1999). 2. Rapid prototyping process chains. The manufacturing of ceramic microparts presented here set out with the 3D-CAD ...

  15. Instructional Resources. The Significance of Form: Ceramics.

    Science.gov (United States)

    Zawatsky, Carole; And Others

    1989-01-01

    Presents four lesson plans designed to teach K-12 students about ceramics and the artists using the medium. Each lesson is centered around one ceramic piece: (1) "Wall Clock," by the Chantilly Porcelain Factory; (2) "Poppy Vase," by Adelaide Robineau; (3) "Laughing Eyes," by Pablo Picasso; and (4) "Ceramic Drum Jar," by Tsayutitsa. (GEA)

  16. Voltage-gated Proton Channels

    Science.gov (United States)

    DeCoursey, Thomas E.

    2014-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance ~103 smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn2+ (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H+ for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens. PMID:23798303

  17. Thermal shock resistance ceramic insulator

    Science.gov (United States)

    Morgan, Chester S.; Johnson, William R.

    1980-01-01

    Thermal shock resistant cermet insulators containing 0.1-20 volume % metal present as a dispersed phase. The insulators are prepared by a process comprising the steps of (a) providing a first solid phase mixture of a ceramic powder and a metal precursor; (b) heating the first solid phase mixture above the minimum decomposition temperature of the metal precursor for no longer than 30 minutes and to a temperature sufficiently above the decomposition temperature to cause the selective decomposition of the metal precursor to the metal to provide a second solid phase mixture comprising particles of ceramic having discrete metal particles adhering to their surfaces, said metal particles having a mean diameter no more than 1/2 the mean diameter of the ceramic particles, and (c) densifying the second solid phase mixture to provide a cermet insulator having 0.1-20 volume % metal present as a dispersed phase.

  18. Dynamic properties of ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Grady, D.E. [Sandia National Labs., Albuquerque, NM (United States). Experimental Impact Physics Dept.

    1995-02-01

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.

  19. Support Services for Ceramic Fiber-Ceramic Matrix Composites

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, JP

    2001-08-16

    To increase national energy self-sufficiency for the near future, power systems will be required to fire low-grade fuels more efficiently than is currently possible. The typical coal-fired steam cycle used at present is limited to a maximum steam temperature of 540 C and a conversion efficiency of 35%. Higher working-fluid temperatures are required to boost efficiency, exposing subsystems to very damaging conditions. Issues of special concern to materials developers are corrosion and warping of hot-gas particulate filters and corrosion and erosion of high-temperature heat exchangers. The University of North Dakota Energy and Environmental Research Center (EERC) is working with the National Energy Technology Laboratory in conjunction with NCC Engineering, Inc., to provide technical assistance and coal by-products to the Fossil Energy Materials Advanced Research and Technology Development Materials Program investigating materials failure in fossil energy systems. The main activities of the EERC are to assemble coal slag and hot-gas filter ash samples for use by materials researchers, to assist in providing opportunities for realistic tests of advanced materials in pilot-scale fossil energy systems, and to provide analytical support in determining corrosion mechanisms of the exposed materials. In this final report for the project year of September 2000 through August 2001, the facilities at the EERC that can be used by researchers for realistic testing of materials are described. Researchers can include sample coupons in each of these facilities at no cost since they are being operated under separate funding. In addition, two pilot-scale coal combustion tests are described in which material sample coupons were included from researchers involved in the development of fossil energy materials. The results of scanning electron microscopy (SEM) energy dispersive x-ray analyses of the corrosion products and interactions between the surface scales of the coupons and the

  20. Charged and Neutral Particles Channeling Phenomena Channeling 2008

    Science.gov (United States)

    Dabagov, Sultan B.; Palumbo, Luigi

    2010-04-01

    regime by a buried oxide layer / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- A positron source using channeling in crystals for linear colliders / X. Artru ... [et al.] -- Parametric channeling and collapse of charged particles beams in crystals / M. Vysotskyy and V. Vysotskii.The formation and usage of coherent correlated charged particles states in the physics of channeling in crystals / S. V. Adamenko, V. I. Vysotskii and M. V. Vysotskyy -- Surface channeling of magnetic-charged particles on multilayer surface / S. V. Adamenko and V. I. Vysotskii -- Coherent creation of anti-hydrogen atoms in a crystal by relativistic antiproton / Yu. P. Kunashenko -- Thermal equilibrium of light ions in heavy crystals / E. Tsyganov -- Photon emission of electrons in a crystalline undulator / H. Backe ... [et al.] -- Channeling radiation from relativistic electrons in a crystal target as complementary x-ray and gamma ray source at synchrotron light facilities / K. B. Korotchenko, Yu. L. Pivovarov and T. A. Tukhfatullin -- Diffracted channeling radiation and other compound radiation processes / H. Nitta -- Collective scattering on the atom planes under the condition of full transition / A. R. Mkrtchyan ... [et al.] -- The proposal of the experiment on the research of the diffracted channeling radiation / D. A. Baklanov ... [et al.] -- Positron channeling at the DaOne BTF Facility: the cup experiment / L. Quintieri ... [et al.] -- Radiation spectra of 200 MeV electrons in diamond and silicon crystals at axial and planar orientations / K. Fissum ... [et al.] -- Channeling experiments with electrons at the Mainz Microtron Mami / W. Lauth ... [et al.] -- Dechanneling of positrons by dislocations: effects of anharmonic interactions / J. George and A. P. Pathak -- Diffracted channeling radiation from axially channeled relativistic electrons / K. B. Korotchenko ... [et al.] -- Intensive quasi-monochromatic, directed x-ray radiation of planar channeled positron bunch / L. Gevorgian

  1. TECHNOLOGY OF PRODUCTION OF CERAMIC TILES BASED ON DOLERITE AND FUSIBLE CLAY

    Directory of Open Access Journals (Sweden)

    Pleshko Marianna Viktorovna

    2018-02-01

    Full Text Available The paper presents a completely new composition of the ceramic mass for production of ceramic tiles for interior lining of walls, on the basis of fusible clay. The optimal compositions of jade engobe and glossy glaze, the most suitable for this composition, are determined. A new technological scheme is developed for production of ceramic tiles for interior lining based on dolerite and fusible clay. The curve of firing, which is the most suitable for charge masses and decorative coating compositions being used, has been constructed. Subject: ceramic mass for the production of ceramic facing tiles. Ceramic tiles are the most popular building material in Russia. The most promising technology for its production from the standpoint of technical and economic efficiency is the technology of rapid single firing, which is rarely used at the plants of our country. In this regard, the development and implementation of new effective compositions of ceramic masses and decorative coatings that are the most compatible with the specifics of rapid single firing technology, based on new unconventional raw materials, are very relevant and promising. Research objectives: development of technological parameters, compositions of ceramic masses and decorative coatings of ceramic tiles for the internal wall lining that provide an increase in tiles production efficiency using the technology of rapid single firing through the use of non-traditional plagioclase-pyroxene raw materials: dolerites, loam and technogenic raw materials. Materials and methods: technological, numerical and experimental studies were conducted. To select the optimal composition of the ceramic mass, the method of mathematical planning was used, namely the simplex-centroid design of Scheffe. To identify the scientific foundations of the energy-efficient production technology being developed, differential thermal and X-ray phase, optical, electron microscopic and dilatometric studies were applied

  2. Investigation of ceramics based on Cu-Sn powder obtained by plasma dynamic method

    Science.gov (United States)

    Shanenkova, Yu; Sivkov, A.; Ivashutenko, A.; Tsimmerman, A.

    2017-05-01

    Composites based on copper matrix are of a great interest in various applications. Copper-tin alloys are intensively investigated due to their thermal and chemical stability in combination with good mechanical properties. This work shows the possibility to obtain Cu-Sn ceramics by spark plasma sintering using nanoscale powders consisting of copper and tin, synthesized by plasma dynamic method. This method is implemented by using a coaxial magnetoplasma accelerator with copper electrodes and adding the solid precursor (tin) in the accelerator before carrying out the synthesis process. The synthesized Cu-Sn powders were investigated by X-Ray diffractometry and transmission electron microscopy. It was determined that the final material consists of phase Cu41Sn11. Using this product, the bulk ceramics samples were obtained by spark plasma sintering at different temperatures (150 °C, 250 °C and 500 °C). The changes in microstructure of copper-tin ceramics in dependence on the sintering temperature were also studied. After analyzing all ceramics samples by X-Ray diffractometry and scanning electron microscopy methods, it was found that the optimal temperature for sintering Cu-Sn ceramics, which was made of the powder synthesized by a plasma dynamic method, was equal to 250 °C at pressure 60 MPa. At these conditions, the ceramics sample had the lowest porosity with the smallest grain size.

  3. Analytical admittance characterization of high mobility channel

    Energy Technology Data Exchange (ETDEWEB)

    Mammeri, A. M.; Mahi, F. Z., E-mail: fati-zo-mahi2002@yahoo.fr [Institute of Science and Technology, University of Bechar (Algeria); Varani, L. [Institute of Electronics of the South (IES - CNRS UMR 5214), University of Montpellier (France)

    2015-03-30

    In this contribution, we investigate the small-signal admittance of the high electron mobility transistors field-effect channels under a continuation branching of the current between channel and gate by using an analytical model. The analytical approach takes into account the linearization of the 2D Poisson equation and the drift current along the channel. The analytical equations discuss the frequency dependence of the admittance at source and drain terminals on the geometrical transistor parameters.

  4. Ceramic components for MHD electrode

    Science.gov (United States)

    Marchant, D.D.

    A ceramic component which exhibits electrical conductivity down to near room temperatures has the formula: Hf/sub x/In/sub y/A/sub z/O/sub 2/ where x = 0.1 to 0.4, y = 0.3 to 0.6, z = 0.1 to 0.4 and A is a lanthanide rare earth or yttrium. The component is suitable for use in the fabrication of MHD electrodes or as the current leadout portion of a composite electrode with other ceramic components.

  5. Ceramic veneers with minimum preparation

    Science.gov (United States)

    da Cunha, Leonardo Fernandes; Reis, Rachelle; Santana, Lino; Romanini, Jose Carlos; Carvalho, Ricardo Marins; Furuse, Adilson Yoshio

    2013-01-01

    The aim of this article is to describe the possibility of improving dental esthetics with low-thickness glass ceramics without major tooth preparation for patients with small to moderate anterior dental wear and little discoloration. For this purpose, a carefully defined treatment planning and a good communication between the clinician and the dental technician helped to maximize enamel preservation, and offered a good treatment option. Moreover, besides restoring esthetics, the restorative treatment also improved the function of the anterior guidance. It can be concluded that the conservative use of minimum thickness ceramic laminate veneers may provide satisfactory esthetic outcomes while preserving the dental structure. PMID:24932126

  6. Carbon-ceramic composites from coal tar pitch and clays: application as electrocatalyst support

    Energy Technology Data Exchange (ETDEWEB)

    Montilla, F.; Morallon, E.; Vazquez, J.L.; Alcaniz-Monge, J.; Cazorla-Amoros, D.

    2002-07-01

    Carbon-ceramic composites were prepared and characterised by different techniques (electron microscopy, X-ray microanalysis, X-ray diffraction and cyclic voltammetry). The effect on the conductivity of the thermal treatment temperature of the composites and the structure of the starting ceramic were analysed. The results demonstrate that the layered structure of the clay determines their conductivity. The composites prepared are conductors and the conductivity increases to a maximum with increasing thermal treatment. Platinum was successfully deposited on the carbon-ceramic composite by chemical and electrochemical methods. A better distribution of platinum and smaller particle sizes are obtained by the electrochemical method. The direct electrooxidation of methanol in acid medium was studied on platinum-modified carbon-ceramic electrodes.

  7. EFFECTS OF INCORPORATING NATURAL MINERALS ON PRODUCTION AND BIOACTIVITY OF BIOACTIVE GLASS CERAMICS

    Directory of Open Access Journals (Sweden)

    Franco Matias Stabile

    2016-07-01

    Full Text Available Two glass-ceramics composition were produced from natural minerals. Quartzes and feldspars were pre-selected on the basis of their purities studied by X-ray diffraction (XRD and chemical analysis. Prepared compositions of glasses precursors were two different theoretical leucite (KAlSi₂O₆ /Bioglass 45S5 (L/Bg ratios. Transformations of raw materials mixtures and glass precursors were studied by differential thermal analyses. On the basis of thermal analysis results, glass ceramics were produced and characterized by XRD. Glass-ceramics were composed of two major crystalline phases, leucite and sodium calcium silicate. Bioactivity tests were performed submerging the glass-ceramics into simulated body fluid (SBF for different periods (1, 5 and 10 days. Bioactive behavior was monitored by XRD and scanning electron microscopy (SEM. Studied samples were found to be bioactive, in which hydroxyapatite layer was developed within 5 days of contact with SBF.

  8. Crystallization behaviors and seal application of basalt based glass-ceramics

    Science.gov (United States)

    Ateş, A.; Önen, U.; Ercenk, E.; Yılmaz, Ş.

    2017-02-01

    Basalt based glass-ceramics were prepared by conventional melt-quenching technique and subsequently converted to glass-ceramics by a controlled nucleation and crystallization process. Glass materials were obtained by melt at 1500°C and quenched in cold water. The powder materials were made by milling and spin coating. The powders were applied on the 430 stainless steel interconnector material, and heat treatment was carried out. The interface characteristics between the glass-ceramic layer and interconnector were investigated by using X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The results showed that the basalt base glass-ceramic sealant material exhibited promising properties to use for SOFC.

  9. Synthesis of biomorphic SiC and SiO2 ceramics

    Directory of Open Access Journals (Sweden)

    ADELA EGELJA

    2008-07-01

    Full Text Available Coniferous wood (fir was transformed by pyrolysis into carbon preforms, which were subsequently converted into biomorphic ceramics by the pressure infiltration technique with colloidal silica. An in situ reaction between the silica and the carbon template occurred in the cellular wall at a high sintering temperature. Depending on the employed atmosphere, non-oxide (SiC or oxide (SiO2 ceramics were obtained. The morphology of the resulting porous ceramics and their phase composition were investigated by scanning electron microscopy (SEM/EDX and X-ray diffraction (XRD. The experimental results showed that the biomorphic cellular morphology of the wood maintained in both the SiC and silica ceramics, which consisted of only the b-SiC phase and SiO2, respectively.

  10. Evaluation of the reuse of glass and ceramic blocks in the development of a ceramic products; Avaliacao do reaproveitamento de blocos ceramicos e de vidro no desenvolvimento de um produto ceramico

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, R.A.; Silva, L.A.; Martins, B.E.D.B.S.; Felippe, C.E.C.; Almeida, V.C., E-mail: valeria@eq.ufrj.b [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Escola de Quimica

    2010-07-01

    The ceramic industry has enormous potential to absorb wastes. The main objective of this study was to evaluate the feasibility of reusing leftovers ceramic blocks, from construction and, with shards of glass in the development of a ceramic product. The ceramic pieces were prepared with different compositions of glass by the method of pressing conformation and heating at 1000 and 1100 deg C. The conformed pieces were tested for linear shrinkage, water absorption, porosity, and tensile strength. The techniques for characterization were X-ray fluorescence, X-ray diffraction and scanning electron microscopy, the results show that the ceramic material produced has a high flexural strength and low values of water absorption. (author)

  11. Comparison of fatigue resistance and failure modes between metal-ceramic and all-ceramic crowns by cyclic loading in water.

    Science.gov (United States)

    Nicolaisen, Maj H; Bahrami, Golnosh; Finlay, Scott; Isidor, Flemming

    2014-12-01

    To compare fatigue resistance and fracture mode of metal-ceramic crowns with all-ceramic crowns containing yttria tetragonal zirconia polycrystal (Y-TZP) frameworks under compressive cycling loading in water. Twenty specimens of ivory were randomized and individually prepared to receive anatomically shaped metal-ceramic (n=10) or veneered Y-TZP all-ceramic crowns (n=10). All steps in production were equivalent to clinical situations. Resistance to fatigue fracture was tested under compressive cyclic loading using a universal testing machine, with a loading frequency of 12Hz using a spherical tungsten carbide indenter (6mm diameter) in distilled water. The maximum compressive load was increased as the number of cycles increased (600,000 cycles at 400N, 200,000 cycles at 600 N, 200,000 cycles at 800 N and 200,000 cycles at 1000 N). The specimens were inspected after each loading sequence for initial failures such as infractions. Final failure was considered as any loss of material which automatically ended the test and the number of cycles until final failure was recorded. Fractographic analysis of the fractured specimens was performed with scanning electron microscopy (SEM). The two types of crowns exhibit similar fatigue resistance (P=0.87) to compressive cycling loading under wet conditions. The failure modes as observed with SEM were similar in the two groups and were found in the veneer ceramic, except that three veneered Y-TZP all-ceramic crowns displayed a complete framework fracture. Within the limitation of this study using simulated oral masticatory function, the results revealed that the fatigue resistance was similar for the two crown types. In this study metal-ceramic crowns and veneered Y-TZP all-ceramic crowns showed similar fracture resistance to compressive cycling loading in water. The test conditions were simulating clinical conditions. Thus, the result may predict the long-term clinical performance of these types of crowns. Copyright © 2014

  12. Radio Channel Modeling in Body Area Networks

    NARCIS (Netherlands)

    An, L.; Bentum, Marinus Jan; Meijerink, Arjan; Scanlon, W.G.

    2009-01-01

    A body area network (BAN) is a network of bodyworn or implanted electronic devices, including wireless sensors which can monitor body parameters or to de- tect movements. One of the big challenges in BANs is the propagation channel modeling. Channel models can be used to understand wave propagation

  13. Radio channel modeling in body area networks

    NARCIS (Netherlands)

    An, L.; Bentum, Marinus Jan; Meijerink, Arjan; Scanlon, W.G.

    2010-01-01

    A body area network (BAN) is a network of bodyworn or implanted electronic devices, including wireless sensors which can monitor body parameters or to detect movements. One of the big challenges in BANs is the propagation channel modeling. Channel models can be used to understand wave propagation in

  14. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  15. Bonding of a mica-based castable ceramic material with a tri-n-butylborane-initiated adhesive resin.

    Science.gov (United States)

    Morikawa, T; Matsumura, H; Atsuta, M

    1996-07-01

    Adhesive bonding of a mica-based castable ceramic material (Olympus Castable Ceramics, OCC) was evaluated in vitro with the use of a silane primer in conjunction with an adhesive luting material. The primer contained a silane coupler and 4-methacryloxyethyl trimellitate anhydride (4-META), while the methyl methacrylate (MMA)-based luting agent was initiated with a tri-n-butylborane derivative (TBB) and contained 4-META (4-META/MMA-TBB resin). Ceramic specimens were sanded with No. 600 silicon carbide paper followed by blasting with alumina and/or etching with ammonium bifluoride. The specimens were bonded with various combinations and shear bond strengths were determined. Both priming and alumina blasting enhanced the bond between 4-META resin and OCC. Although etching with ammonium bifluoride roughened the ceramic surface, this procedure did not improve the bond strength. Electron probe microanalysis of the ceramic surface revealed a decrease in silicon and aluminium elements after etching with ammonium bifluoride.

  16. Nd:YAG Laser-aided ceramic brackets debonding: Effects on shear bond strength and enamel surface

    Energy Technology Data Exchange (ETDEWEB)

    Han Xianglong [State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041 (China); Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Liu Xiaolin [Department of Orthodontics, Stomatology Hospital, Dalian University, Dalian 116021 (China); Bai Ding [State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041 (China); Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China)], E-mail: baiding88@hotmail.com; Meng Yao; Huang Lan [Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China)

    2008-11-15

    In order to evaluate the efficiency of Nd:YAG laser-aided ceramic brackets debonding technique, both ceramic brackets and metallic brackets were bonded with orthodontic adhesive to 30 freshly extracted premolars. The specimens were divided into three groups, 10 in each, according to the brackets employed and the debonding techniques used: (1) metallic brackets with shear debonding force, (2) ceramic brackets with shear debonding force, and (3) ceramic brackets with Nd:YAG laser irradiation. The result showed that laser irradiation could diminish shear bond strength (SBS) significantly and produce the most desired ARI scores. Moreover, scanning electron microscopy investigation displayed that laser-aided technique induced little enamel scratch or loss. It was concluded that Nd:YAG laser could facilitate the debonding of ceramic brackets and diminish the amount of remnant adhesive without damaging enamel structure.

  17. Recent progress on synthesis of ceramics core/shell nanostructures

    Directory of Open Access Journals (Sweden)

    Vladimir V. Srdić

    2013-06-01

    Full Text Available Thin surface layers on fine particles were found to substantially change their functionalities and properties, such as chemical reactivity, thermal stability, catalytic activity, dispersibility, or optical, magnetic and electronic properties. Because of that, the core/shell nanostructures have opened up research opportunities in almost all areas of science and engineering, including medicine, catalysis, biotechnology, chemistry, optics, electronics, energy storage, etc. Immense efforts have been implied to produce and investigate different core/shell systems, and thereby, various synthesis techniques have been developed. In this review, we report adetailed overview of different synthesis techniques used for preparation of various ceramics core/shell nanostructures with tunable size and tailored structure.

  18. Shape-dependent plasma-catalytic activity of ZnO nanomaterials coated on porous ceramic membrane for oxidation of butane.

    Science.gov (United States)

    Sanjeeva Gandhi, M; Mok, Young Sun

    2014-12-01

    In order to explore the effects of the shape of ZnO nanomaterials on the plasma-catalytic decomposition of butane and the distribution of byproducts, three types of ZnO nanomaterials (nanoparticles (NPs), nanorods (NRs) and nanowires (NWs)) were prepared and coated on multi-channel porous alumina ceramic membrane. The structures and morphologies of the nanomaterials were confirmed by X-ray diffraction method and scanning electron microscopy. The observed catalytic activity of ZnO in the oxidative decomposition of butane was strongly shape-dependent. It was found that the ZnO NWs exhibited higher catalytic activity than the other nanomaterials and could completely oxidize butane into carbon oxides (COx). When using the bare or ZnO NPs-coated ceramic membrane, several unwanted partial oxidation and decomposition products like acetaldehyde, acetylene, methane and propane were identified during the decomposition of butane. When the ZnO NWs- or ZnO NRs-coated membrane was used, however, the formation of such unwanted byproducts except methane was completely avoided, and full conversion into COx was achieved. Better carbon balance and COx selectivity were obtained with the ZnO NWs and NRs than with the NPs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Industrial ceramics in Spain

    Directory of Open Access Journals (Sweden)

    Regueiro, M.

    2000-02-01

    Full Text Available The Spanish ceramic industry has experienced a amazing growth in the last four years. Such expansion has affected all sector, but has been particularly noteworthy in those directly related to construction: tiles. glazes, bricks and roof tiles. A combination of an extraordinary exporting effort, together with a record figure in new housing projects (415 000 houses in 1999, are responsible for such outburst. Other sectors, such as refractories have undergone significant growths due to the high rate of steel production increase, also in historical record figures (15m t in 1999. All this sectors doubled altogether the growing rate of their main European competitors. Raw material production has had an even more effervescent trend, almost doubling 1995 production. Such dynamic growth has been associated to a remarkable quality increase and to an unparalleled technological innovation process.

    La industria española de la cerámica ha experimentado un notable crecimiento en los últimos cuatro años; expansión que ha alcanzado a todos los sectores, pero que ha sido especialmente notable en los mas directamente asociados a la construcción: revestimientos, esmaltes, tejas y ladrillos. La combinación de un extraordinario esfuerzo exportador unido a las cifras récord en la viviendas iniciadas, 415 000 en 1999, justifican este auge. Otros sectores como refractarios han experimentado crecimientos significativos ante el ritmo elevado en la producción de acero, que alcanzó asimismo un récord histórico, 15 Mt en 1999. Para el conjunto de estos sectores el ritmo de crecimiento ha duplicado el de los principales competidores europeos. La producción de materias primas han experimentado un dinamismo aún mas elevado duplicándose prácticamente las cifras respecto a 1995. Este crecimiento ha estado asociado a un notable incremento en la calidad y en los procesos de innovación tecnológica.

  20. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; Thomas W. Eagar; Harold R. Larson; Raymundo Arroyave; X.-D Zhou; Y.-W. Shin; H.U. Anderson; Nigel Browning; Alan Jacobson; C.A. Mims

    2003-11-01

    The present quarterly report describes some of the initial studies on newer compositions and also includes newer approaches to address various materials issues such as in metal-ceramic sealing. The current quarter's research has also focused on developing a comprehensive reliability model for predicting the structural behavior of the membranes in realistic conditions. In parallel to industry provided compositions, models membranes have been evaluated in varying environment. Of importance is the behavior of flaws and generation of new flaws aiding in fracture. Fracture mechanics parameters such as crack tip stresses are generated to characterize the influence of environment. Room temperature slow crack growth studies have also been initiated in industry provided compositions. The electrical conductivity and defect chemistry of an A site deficient compound (La{sub 0.55}Sr{sub 0.35}FeO{sub 3}) was studied. A higher conductivity was observed for La{sub 0.55}Sr{sub 0.35}FeO{sub 3} than that of La{sub 0.60}Sr{sub 0.40}FeO{sub 3} and La{sub 0.80}Sr{sub 0.20}FeO{sub 3}. Defect chemistry analysis showed that it was primarily contributed by a higher carrier concentration in La{sub 0.55}Sr{sub 0.35}FeO{sub 3}. Moreover, the ability for oxygen vacancy generation is much higher in La{sub 0.55}Sr{sub 0.35}FeO{sub 3} as well, which indicates a lower bonding strength between Fe-O and a possible higher catalytic activity for La{sub 0.55}Sr{sub 0.35}FeO{sub 3}. The program continued to investigate the thermodynamic properties (stability and phase separation behavior) and total conductivity of prototype membrane materials. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previous report listed initial measurements on a sample of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-x} prepared in-house by Praxair. Subsequently, a second sample of powder from a larger batch of sample were characterized and compared

  1. Divalent ytterbium ions in yttrium aluminum garnet and yttrium oxide ceramics

    Science.gov (United States)

    Solomonov, V. I.; Orlov, A. N.; Spirina, A. V.; Konev, S. F.; Cholakh, S. O.; Luk'yashin, K. E.

    2014-12-01

    Laser ceramics based on ytterbium-doped yttrium aluminum garnet and yttrium oxide are synthesized. The transmission, pulsed cathodoluminescence, and electron-spin resonance spectra of these ceramics at room temperature are measured and analyzed. It is shown that all the samples contain Yb2+ ions with the 4 f 136 s electronic configuration of the ground state, which manifest themselves in the form of relatively weak bands in the IR region of the optical spectra in addition to the bands of Yb3+ ions.

  2. Doubled-ended ceramic thyratron

    CERN Multimedia

    1974-01-01

    The double-ended ceramic thyratron CX 1171 B, with its coaxial voltage divider for the SPS. Such a switch, paralleled by three ignitrons in series forms the "thyragnitron" arrangement, and can switch 10 kA, 25 ms pulses, with very fast rise times.

  3. Optical scattering in glass ceramics

    NARCIS (Netherlands)

    Mattarelli, M.; Montagna, M.; Verrocchio, P.

    2008-01-01

    The transparency of glass ceramics with nanocrystals is generally higher than that expected from the theory of Rayleigh scattering. We attribute this ultra-transparency to the spatial correlation of the nanoparticles. The structure factor is calculated for a simple model system, the random

  4. Gas Separations using Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Paul KT Liu

    2005-01-13

    This project has been oriented toward the development of a commercially viable ceramic membrane for high temperature gas separations. A technically and commercially viable high temperature gas separation membrane and process has been developed under this project. The lab and field tests have demonstrated the operational stability, both performance and material, of the gas separation thin film, deposited upon the ceramic membrane developed. This performance reliability is built upon the ceramic membrane developed under this project as a substrate for elevated temperature operation. A comprehensive product development approach has been taken to produce an economically viable ceramic substrate, gas selective thin film and the module required to house the innovative membranes for the elevated temperature operation. Field tests have been performed to demonstrate the technical and commercial viability for (i) energy and water recovery from boiler flue gases, and (ii) hydrogen recovery from refinery waste streams using the membrane/module product developed under this project. Active commercializations effort teaming with key industrial OEMs and end users is currently underway for these applications. In addition, the gas separation membrane developed under this project has demonstrated its economical viability for the CO2 removal from subquality natural gas and landfill gas, although performance stability at the elevated temperature remains to be confirmed in the field.

  5. Quantitative 'real-time' imaging of multi-phase flow in ceramic monoliths.

    Science.gov (United States)

    Sederman, A J; Mantle, M D; Gladden, L F

    2003-01-01

    An extension of the RARE technique has been developed which acquires multiple images from a single radio-frequency excitation. This pulse sequence has been used to image, in real-time, gas flow through stagnant liquid within parallel-channel ceramic monoliths. From these images, gas-phase volume fractions, and distributions of gas bubble length and velocity as a function of gas flow rate (50-300 cm3 min(-1)) and channel size (300 and 400 channels per square inch, cpsi) are obtained directly. Increasing the gas flow rate increased the number of large bubbles and the average bubble velocity. A bimodal distribution in the bubble velocities was observed for flow within the larger channel size (300 cpsi) in contrast to a broad unimodal distribution characterizing two-phase flow within the smaller channel size (400 cpsi).

  6. Crystallisation Kinetics of a β-Spodumene-Based Glass Ceramic

    Directory of Open Access Journals (Sweden)

    Oscar Rubem Klegues Montedo

    2012-01-01

    Full Text Available LZSA (Li2O-ZrO2-SiO2-Al2O3 glass ceramic system has shown high potential to obtain LTCC laminate tapes at low sintering temperature (<1000°C for several applications, such as screen-printed electronic components. Furthermore, LZSA glass ceramics offer interesting mechanical, chemical, and thermal properties, which make LZSA also a potential candidate for fabricating multilayered structures processed by Laminated Objects Manufacturing (LOM technology. The crystallization kinetics of an LZSA glass ceramic with a composition of 16.9Li2O⋅5.0ZrO2⋅65.1SiO2⋅8.6Al2O3 was investigated using nonisothermal methods by differential thermal analysis and scanning electronic microscopy. Apparent activation energy for crystallization was found to be in the 274–292 kJ⋅mol−1 range, and an Avrami parameter n of 1 was obtained that is compared very favorably with SEM observations.

  7. Synthesis and characterization of ceramic/carbon nanotubes composite adsorptive membrane for copper ion removal from water

    Energy Technology Data Exchange (ETDEWEB)

    Tofighy, Maryam Ahmadzadeh; Mohammadi, Toraj [Iran University of Science and Technology (IUST), Tehran (Iran, Islamic Republic of)

    2015-02-15

    We prepared a novel adsorptive membrane by implanting carbon nanotubes (CNTs) in pore channels of ceramic (α-alumina) support via chemical vapor deposition (CVD) method using cyclohexanol and ferrocene as carbon precursor and catalyst, respectively. Optimization of CNTs growth conditions resulted in uniform distribution of the CNTs in the pore channels of the support. The optimized CNTs-ceramic membrane was oxidized with concentrated nitric acid, and chitosan was employed for filling intertube-CNT gaps. The modified CNTs-ceramic membrane was used for copper ion removal from water, and the effects of the modification steps (oxidation and filling intertube-CNT gaps with chitosan) and pH on permeation flux and rejection of the prepared adsorptive membrane were investigated. Moreover, static adsorption was also investigated and Langmuir and Freundlich isotherms and two kinetics models were used to describe adsorption behavior of copper ions by the prepared adsorptive membrane.

  8. Fabrication of silica ceramic membrane via sol-gel dip-coating method at different nitric acid amount

    Science.gov (United States)

    Kahlib, N. A. Z.; Daud, F. D. M.; Mel, M.; Hairin, A. L. N.; Azhar, A. Z. A.; Hassan, N. A.

    2018-01-01

    Fabrication of silica ceramics via the sol-gel method has offered more advantages over other methods in the fabrication of ceramic membrane, such as simple operation, high purity homogeneous, well defined-structure and complex shapes of end products. This work presents the fabrication of silica ceramic membrane via sol-gel dip-coating methods by varying nitric acid amount. The nitric acid plays an important role as catalyst in fabrication reaction which involved hydrolysis and condensation process. The tubular ceramic support, used as the substrate, was dipped into the sol of Tetrethylorthosilicate (TEOS), distilled water and ethanol with the addition of nitric acid. The fabricated silica membrane was then characterized by (Field Emission Scanning Electron Microscope) FESEM and (Fourier transform infrared spectroscopy) FTIR to determine structural and chemical properties at different amount of acids. From the XRD analysis, the fabricated silica ceramic membrane showed the existence of silicate hydrate in the final product. FESEM images indicated that the silica ceramic membrane has been deposited on the tubular ceramic support as a substrate and penetrate into the pore walls. The intensity peak of FTIR decreased with increasing of amount of acids. Hence, the 8 ml of acid has demonstrated the appropriate amount of catalyst in fabricating good physical and chemical characteristic of silica ceramic membrane.

  9. Silica coating on alumina ceramic: comparison of three chairside air-abrasion devices working for different times and distances.

    Science.gov (United States)

    Pestana Passos, S; Dias Vanderlei, A; Ozcan, M; Felipe Valandro, L F; Felipe Valandro, L

    2011-03-01

    This study evaluated, by scanning electron microscope (SEM) and EDS, the effect of different strategies for silica coating (sandblasters, time and distance) of a glass-infiltrated ceramic (In-Ceram Alumina). Forty-one ceramic blocks were produced. For comparison of the three air-abrasion devices, 15 ceramic samples were divided in three groups (N.=5): Bioart, Microetcher and Ronvig (air-abrasion parameters: 20 s at a distance of 10 mm). For evaluation of the time and distance factors, ceramic samples (N.=5) were allocated in groups considering three applied times (5 s, 13 s and 20 s) and two distances (10 mm and 20 mm), using the Ronvig device. In a control sample, no surface treatment was performed. After that, the micro-morphologic analyzes of the ceramic surfaces were made using SEM. EDS analyzes were carried out to detect the % of silica on representative ceramic surface. ANOVA and Tukey tests were used to analyze the results. One-way ANOVA showed the silica deposition was different for different devices (P=0.0054). The Ronvig device promoted the highest silica coating compared to the other devices (Tukey test). Two-way ANOVA showed the distance and time factors did not affect significantly the silica deposition (application time and distance showed no statistical difference). The Ronvig device provided the most effective silica deposition on glass-infiltrated alumina ceramic surface and the studied time and distance for air-abrasion did not affect the silica coating.

  10. Physical properties of neodymium tin oxide pyrochlore ceramics

    Directory of Open Access Journals (Sweden)

    Saleh Adli A.

    2017-10-01

    Full Text Available In this work, physical properties of neodymium tin oxide pyrochlore ceramics prepared by solid state reaction technique are investigated by means of X-ray diffraction, scanning electron microscopy, ultraviolet-visible light (UV-Vis spectrophotometry and temperature dependent electrical resistivity measurements. The pyrochlore is observed to have a cubic FCC crystal lattice with lattice parameter of 10.578 Å. The planes of the cubic cell are best oriented in the [2 2 2] direction. From the X-ray, the UV-Vis spectrophotometry and the electrical resistivity data analysis, the grain size, strain, dislocation density, optical and thermal energy band gaps, localized energy band tail states and resistivity activation energies are determined and discussed. The pyrochlore is observed to have an optical energy band gap of ~3.40 eV. This value corresponds to 365 nm UV light spectra which nominates the neodymium tin oxide pyrochlore ceramics for the use as UV sensors.

  11. Microstructure characterization of porous microalloyed aluminium-silicate ceramics

    Directory of Open Access Journals (Sweden)

    Purenović Jelena

    2011-01-01

    Full Text Available Kaolinite and bentonite clay powders mixed with active additives, based on Mg(NO32 and Al(NO32, sintered at high temperatures produce very porous ceramics with microcrystalline and amorphous regions and highly developed metalized surfaces (mainly with magnesium surplus. Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. The ceramics samples were characterized by scanning electron microscopy (SEM, energy dispersive spectrometer (EDS, X-ray diffraction analysis (XRD and IR spectroscopy analysis, prior and after treatment in “synthetic water”, i.e. in aqueous solution of arsenic-salt. Grain size distribution for untreated and treated samples was done with software SemAfore 4. It has shown great variety in size distribution of grains from clay powders to sintered samples.

  12. Thin-Film Ceramic Thermocouples Fabricated and Tested

    Science.gov (United States)

    Wrbanek, John D.; Fralick, Gustave C.; Farmer, Serene C.; Sayir, Ali; Gregory, Otto J.; Blaha, Charles A.

    2004-01-01

    The Sensors and Electronics Technology Branch of the NASA Glenn Research Center is developing thin-film-based sensors for surface measurement in propulsion system research. Thin-film sensors do not require special machining of the components on which they are mounted, and they are considerably thinner than wire- or foil-based sensors. One type of sensor being advanced is the thin-film thermocouple, specifically for applications in high-temperature combustion environments. Ceramics are being demonstrated as having the potential to meet the demands of thin-film thermocouples in advanced aerospace environments. The maximum-use temperature of noble metal thin-film thermocouples, 1500 C (2700 F), may not be adequate for components used in the increasingly harsh conditions of advanced aircraft and next-generation launch vehicles. Ceramic-based thermocouples are known for their high stability and robustness at temperatures exceeding 1500 C, but are typically in the form of bulky rods or probes. As part of ASTP, Glenn's Sensors and Electronics Technology Branch is leading an in-house effort to apply ceramics as thin-film thermocouples for extremely high-temperature applications as part of ASTP. Since the purity of the ceramics is crucial for the stability of the thermocouples, Glenn's Ceramics Branch and Case Western Reserve University are developing high-purity ceramic sputtering targets for fabricating high-temperature sensors. Glenn's Microsystems Fabrication Laboratory, supported by the Akima Corporation, is using these targets to fabricate thermocouple samples for testing. The first of the materials used were chromium silicide (CrSi) and tantalum carbide (TaC). These refractory materials are expected to survive temperatures in excess of 1500 C. Preliminary results indicate that the thermoelectric voltage output of a thin-film CrSi versus TaC thermocouple is 15 times that of the standard type R (platinum-rhodium versus platinum) thermocouple, producing 20 mV with a 200

  13. Catalyzed Ceramic Burner Material

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Amy S., Dr.

    2012-06-29

    period in accomplishing these objectives. Our work in the area of Pd-based, methane oxidation catalysts has led to the development of highly active catalysts with relatively low loadings of Pd metal using proprietary coating methods. The thermal stability of these Pd-based catalysts were characterized using SEM and BET analyses, further demonstrating that certain catalyst supports offer enhanced stability toward both PdO decomposition and/or thermal sintering/growth of Pd particles. When applied to commercially available fiber mesh substrates (both metallic and ceramic) and tested in an open-air burner, these catalyst-support chemistries showed modest improvements in the NOx emissions and radiant output compared to uncatalyzed substrates. More significant, though, was the performance of the catalyst-support chemistries on novel media substrates. These substrates were developed to overcome the limitations that are present with commercially available substrate designs and increase the gas-catalyst contact time. When catalyzed, these substrates demonstrated a 65-75% reduction in NOx emissions across the firing range when tested in an open air burner. In testing in a residential boiler, this translated into NOx emissions of <15 ppm over the 15-150 kBtu/hr firing range.

  14. PREFACE: Symposium 1: Advanced Structure Analysis and Characterization of Ceramic Materials

    Science.gov (United States)

    Yashima, Masatomo

    2011-05-01

    Preface to Symposium 1 (Advanced Structure Analysis and Characterization of Ceramic Materials) of the International Congress of Ceramics III, held 14-18 November 2010 in Osaka, Japan Remarkable developments have been made recently in the structural analysis and characterization of inorganic crystalline and amorphous materials, such as x-ray, neutron, synchrotron and electron diffraction, x-ray/neutron scattering, IR/Raman scattering, NMR, XAFS, first-principle calculations, computer simulations, Rietveld analysis, the maximum-entropy method, in situ measurements at high temperatures/pressures and electron/nuclear density analysis. These techniques enable scientists to study not only static and long-range periodic structures but also dynamic and short-/intermediate-range structures. Multi-scale characterization from the electron to micrometer levels is becoming increasingly important as a means of understanding phenomena at the interfaces, grain boundaries and surfaces of ceramic materials. This symposium has discussed the structures and structure/property relationships of various ceramic materials (electro, magnetic and optical ceramics; energy and environment related ceramics; bio-ceramics; ceramics for reliability secure society; traditional ceramics) through 38 oral presentations including 8 invited lectures and 49 posters. Best poster awards were given to six excellent poster presentations (Y-C Chen, Tokyo Institute of Technology; C-Y Chung, Tohoku University; T Stawski, University of Twente; Y Hirano, Nagoya Institute of Technology; B Bittova, Charles University Prague; Y Onodera, Kyoto University). I have enjoyed working with my friends in the ICC3 conference. I would like to express special thanks to other organizers: Professor Scott T Misture, Alfred University, USA, Professor Xiaolong Chen, Institute of Physics, CAS, China, Professor Takashi Ida, Nagoya Institute of Technology, Japan, Professor Isao Tanaka, Kyoto University, Japan. I also acknowledge the

  15. Surface characterization of lithium disilicate ceramic after nonthermal plasma treatment.

    Science.gov (United States)

    Vechiato Filho, Aljomar José; dos Santos, Daniela Micheline; Goiato, Marcelo Coelho; de Medeiros, Rodrigo Antonio; Moreno, Amália; Bonatto, Liliane da Rocha; Rangel, Elidiane Cipriano

    2014-11-01

    Surface transformation with nonthermal plasma may be a suitable treatment for dental ceramics, because it does not affect the physical properties of the ceramic material. The purpose of this study was to characterize the chemical composition of lithium disilicate ceramic and evaluate the surface of this material after nonthermal plasma treatment. A total of 21 specimens of lithium disilicate (10 mm in diameter and 3 mm thick) were fabricated and randomly divided into 3 groups (n=7) according to surface treatment. The control group was not subjected to any treatment except surface polishing with abrasive paper. In the hydrofluoric acid group, the specimens were subjected to hydrofluoric acid gel before silane application. Specimens in the nonthermal plasma group were subjected to the nonthermal plasma treatment. The contact angle was measured to calculate surface energy. In addition, superficial roughness was measured and was examined with scanning electron microscopy, and the chemical composition was characterized with energy-dispersive spectroscopy analysis. The results were analyzed with ANOVA and the Tukey honestly significant difference test (α=.05). The water contact angle was decreased to 0 degrees after nonthermal plasma treatment. No significant difference in surface roughness was observed between the control and nonthermal plasma groups. Scanning electron microscopy and energy-dispersive spectroscopy images indicated higher amounts of oxygen (O) and silicon (Si) and a considerable reduction in carbon (C) in the specimens after nonthermal plasma treatment. Nonthermal plasma treatment can transform the characteristics of a ceramic surface without affecting its surface roughness. A reduction in C levels and an increase in O and Si levels were observed with the energy-dispersive spectroscopy analysis, indicating that the deposition of the thin silica film was efficient. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by

  16. Translucency of dental ceramics with different thicknesses.

    Science.gov (United States)

    Wang, Fu; Takahashi, Hidekazu; Iwasaki, Naohiko

    2013-07-01

    The increased use of esthetic restorations requires an improved understanding of the translucent characteristics of ceramic materials. Ceramic translucency has been considered to be dependent on composition and thickness, but less information is available about the translucent characteristics of these materials, especially at different thicknesses. The purpose of this study was to investigate the relationship between translucency and the thickness of different dental ceramics. Six disk-shaped specimens of 8 glass ceramics (IPS e.max Press HO, MO, LT, HT, IPS e.max CAD LT, MO, AvanteZ Dentin, and Trans) and 5 specimens of 5 zirconia ceramics (Cercon Base, Zenotec Zr Bridge, Lava Standard, Lava Standard FS3, and Lava Plus High Translucency) were prepared following the manufacturers' instructions and ground to a predetermined thickness with a grinding machine. A spectrophotometer was used to measure the translucency parameters (TP) of the glass ceramics, which ranged from 2.0 to 0.6 mm, and of the zirconia ceramics, which ranged from 1.0 to 0.4 mm. The relationship between the thickness and TP of each material was evaluated using a regression analysis (α=.05). The TP values of the glass ceramics ranged from 2.2 to 25.3 and the zirconia ceramics from 5.5 to 15.1. There was an increase in the TP with a decrease in thickness, but the amount of change was material dependent. An exponential relationship with statistical significance (Pceramics and zirconia ceramics. The translucency of dental ceramics was significantly influenced by both material and thickness. The translucency of all materials increased exponentially as the thickness decreased. All of the zirconia ceramics evaluated in the present study showed some degree of translucency, which was less sensitive to thickness compared to that of the glass ceramics. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  17. Biomimetic processing of oriented crystalline ceramic layers

    Energy Technology Data Exchange (ETDEWEB)

    Cesarano, J.; Shelnutt, J.A.

    1997-10-01

    The aim of this project was to develop the capabilities for Sandia to fabricate self assembled Langmuir-Blodgett (LB) films of various materials and to exploit their two-dimensional crystalline structure to promote the growth of oriented thin films of inorganic materials at room temperature. This includes the design and synthesis of Langmuir-active (amphiphilic) organic molecules with end groups offering high nucleation potential for various ceramics. A longer range goal is that of understanding the underlying principles, making it feasible to use the techniques presented in this report to fabricate unique oriented films of various materials for electronic, sensor, and membrane applications. Therefore, whenever possible, work completed in this report was completed with the intention of addressing the fundamental phenomena underlying the growth of crystalline, inorganic films on template layers of highly organized organic molecules. This problem was inspired by biological processes, which often produce exquisitely engineered structures via templated growth on polymeric layers. Seashells, for example, exhibit great toughness owing to their fine brick-and-mortar structure that results from templated growth of calcium carbonate on top of layers of ordered organic proteins. A key goal in this work, therefore, is to demonstrate a positive correlation between the order and orientation of the template layer and that of the crystalline ceramic material grown upon it. The work completed was comprised of several parallel efforts that encompassed the entire spectrum of biomimetic growth from solution. Studies were completed on seashells and the mechanisms of growth for calcium carbonate. Studies were completed on the characterization of LB films and the capability developed for the in-house fabrication of these films. Standard films of fatty acids were studied as well as novel polypeptides and porphyrins that were synthesized.

  18. Environmental Effects on Non-oxide Ceramics

    Science.gov (United States)

    Jacobson, Nathan S.; Opila, Elizabeth J.

    1997-01-01

    Non-oxide ceramics such as silicon carbide (SiC) and silicon nitride (Si3N4) are promising materials for a wide range of high temperature applications. These include such diverse applications as components for heat engines, high temperature electronics, and re-entry shields for space vehicles. Table I lists a number of selected applications. Most of the emphasis here will be on SiC and Si3N4. Where appropriate, other non-oxide materials such as aluminum nitride (AlN) and boron nitride (BN) will be discussed. Proposed materials include both monolithic ceramics and composites. Composites are treated in more detail elsewhere in this volume, however, many of the oxidation/corrosion reactions discussed here can be extended to composites. In application these materials will be exposed to a wide variety of environments. Table I also lists reactive components of these environments.It is well-known that SiC and Si3N4 retain their strength to high temperatures. Thus these materials have been proposed for a variety of hot-gas-path components in combustion applications. These include heat exchanger tubes, combustor liners, and porous filters for coal combustion products. All combustion gases contain CO2, CO, H2, H2O, O2, and N2. The exact gas composition is dependent on the fuel to air ratio or equivalence ratio. (Equivalence ratio (EQ) is a fuel-to-air ratio, with total hydrocarbon content normalized to the amount of O2 and defined by EQ=1 for complete combustion to CO2 and H2O). Figure 1 is a plot of equilibrium gas composition vs. equivalence ratio. Note that as a general rule, all combustion atmospheres are about 10% water vapor and 10% CO2. The amounts of CO, H2, and O2 are highly dependent on equivalence ratio.

  19. Fabrication and measurement of optical and spectral properties of the transparent Yb:MgAl2O4 ceramics

    Science.gov (United States)

    Balabanov, S. S.; Belyaev, A. V.; Gavrishchuk, E. M.; Mukhin, I. B.; Novikova, A. V.; Palashov, O. V.; Permin, D. A.; Snetkov, I. L.

    2017-09-01

    In this paper results concerning the fabrication of transparent (with 0.1% mol Yb3+), translucent (with 0.5% mol Yb3+) and opaque (up to 5% mol Yb3+) Yb3+: MgAl2O4 ceramics by hot pressing are presented. The alkoxotechnology of starting magnesium aluminate spinel nanopowder synthesis with homogeneous distribution of Yb ions is proposed. The structural properties of the prepared powders and ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET method. The optical transmittance, absorption and emission cross sections, and the upper level lifetime of the Yb3+:MgAl2O4 ceramics were measured.

  20. The Lattice Compatibility Theory: Arguments for Recorded I-III-O2 Ternary Oxide Ceramics Instability at Low Temperatures beside Ternary Telluride and Sulphide Ceramics

    Directory of Open Access Journals (Sweden)

    K. Boubaker

    2013-01-01

    Full Text Available Some recorded behaviours differences between chalcopyrite ternary oxide ceramics and telluride and sulphides are investigated in the framework of the recently proposed Lattice Compatibility Theory (LCT. Alterations have been evaluated in terms of Urbach tailing and atomic valence shell electrons orbital eigenvalues, which were calculated through several approximations. The aim of the study was mainly an attempt to explain the intriguing problem of difficulties of elaborating chalcopyrite ternary oxide ceramics (I-III-O2 at relatively low temperatures under conditions which allowed crystallization of ternary telluride and sulphides.

  1. Ceramic fiber reinforced glass-ceramic matrix composite

    Science.gov (United States)

    Bansal, Narottam P. (Inventor)

    1993-01-01

    A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous chemical vapor deposition (CVD)-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite which is heated to burn out organic constituents. The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

  2. Investigation of zircon/zirconia ceramics doped with {sup 239}Pu and {sup 238}Pu

    Energy Technology Data Exchange (ETDEWEB)

    Burakov, B.E.; Anderson, E.B.; Zamoryanskaya, M.V.; Nikolaeva, E.V.; Strykanova, E.E.; Yagovkina, M.A. [V.G. Khlopin Radium Institute, Saint Petersburg (Russian Federation)

    2001-07-01

    Several samples of crystalline double-phase ceramics based on zircon, (Zr,Pu)SiO{sub 4} and zirconia, (Zr,Pu)O{sub 2}, were synthesized by sintering in air, precursors containing approximately 5-6 and 10 wt% {sup 239}Pu, respectively. One sample doped with 5-6 wt% {sup 238-39-40}Pu was also obtained under the same conditions. All ceramic samples were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and MCC-1 leach test in deionized water at 90 C. Results indicate that even radiation damaged zircon/zirconia ceramics retain high chemical resistance and mechanical durability. (author)

  3. Machinability of lithium disilicate glass ceramic in in vitro dental diamond bur adjusting process.

    Science.gov (United States)

    Song, Xiao-Fei; Ren, Hai-Tao; Yin, Ling

    2016-01-01

    Esthetic high-strength lithium disilicate glass ceramics (LDGC) are used for monolithic crowns and bridges produced in dental CAD/CAM and oral adjusting processes, which machinability affects the restorative quality. A machinability study has been made in the simulated oral clinical machining of LDGC with a dental handpiece and diamond burs, regarding the diamond tool wear and chip control, machining forces and energy, surface finish and integrity. Machining forces, speeds and energy in in vitro dental adjusting of LDGC were measured by a high-speed data acquisition and force sensor system. Machined LDGC surfaces were assessed using three-dimensional non-contact chromatic confocal optical profilometry and scanning electron microscopy (SEM). Diamond bur morphology and LDGC chip shapes were also examined using SEM. Minimum tool wear but significant LDGC chip accumulations were found. Machining forces and energy significantly depended on machining conditions (pglass ceramics (pglass ceramics (pglass ceramics. Surface roughness for machined LDGC was comparable for other glass ceramics. The removal mechanisms of LDGC were dominated by penetration-induced brittle fracture and shear-induced plastic deformation. Unlike most other glass ceramics, distinct intergranular and transgranular fractures of lithium disilicate crystals were found in LDGC. This research provides the fundamental data for dental clinicians on the machinability of LDGC in intraoral adjustments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Fabrication and characterization of biomimetic ceramic/polymer composite materials for dental restoration.

    Science.gov (United States)

    Petrini, Morena; Ferrante, Maurizio; Su, Bo

    2013-04-01

    Conventional dental composites with randomly dispersed inorganic particles within a polymer matrix fail to recapitulate the aligned and anisotropic structure of the dentin and enamel. The aim of the study was to produce a biomimetic composite consisting of a ceramic preform with graded and continuously aligned open pores, infiltrated with epoxy resin. The freeze casting technique was used to obtain the hierarchically structured architecture of the ceramic preforms. Optical and scanning electron microscopy (SEM) and differential thermal analysis and thermogravimetry (TG-DTA) were used to characterize the samples. Three point bending test and compression test were also performed. All analysis confirmed that the biomimetic composite was characterized by a multi-level hierarchical structure along the freezing direction. In the bottom layers close to the cooling plate (up to 2mm thick), a randomly packed ceramic with closed pores were formed, which resulted in incomplete infiltration with resin and resultant poor mechanical propertiesof the composite. Above 2mm, all ceramic samples showed an aligned structure with an increasing lamellae spacing (wavelength) and a decreasing wall thickness. Mechanical tests showed that the properties of the composites made from ceramic preforms above 2mm from cooling plate are similar to those of the dentin. The fabrication processing reported in this work offers a viable route for the fabrication of biomimetic composites, which could be potentially used in a range of dental restorations to compete with the current dental composites and ceramics. Copyright © 2012 Academy of Dental Materials. All rights reserved.

  5. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    Science.gov (United States)

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P dental materials. PMID:22619551

  6. Incisal coverage or not in ceramic laminate veneers: A systematic review and meta-analysis.

    Science.gov (United States)

    Albanesi, Rafael Borges; Pigozzo, Mônica Nogueira; Sesma, Newton; Laganá, Dalva Cruz; Morimoto, Susana

    2016-09-01

    There is no consensus on whether incisal coverage is a risk or a protective factor in preparations for ceramic veneers. The aim of this systematic review and meta-analysis was to evaluate the survival rates of preparation designs for ceramic veneers with and without incisal coverage. Primary clinical studies with the following characteristics were included: 1) studies related to ceramic laminate veneers and 2) prospective or retrospective studies conducted in humans. From the selected studies, the survival rates and failures rates for ceramic veneers were extracted according to preparation design, with or without incisal coverage. The Cochran Q test and the I(2) statistic were used to evaluate heterogeneity. Metaregression, meta-analysis were performed. Two reviewers searched in the MEDLINE (Pubmed) and Cochrane Central Register of Controlled Trials (Central) electronic databases, from 1977 to June 5, 2016, without language restrictions. Eight studies out of 1145 articles initially identified were included for risk of bias and systematic assessment. No study was identified for crystalline ceramic veneers. The estimated survival rate for laminate veneers with incisal coverage was 88% and 91% for those without incisal coverage. Incisal coverage presented an OR of 1.25. Irrespective of the preparation designs, with or without incisal coverage, ceramic veneers showed high survival rates. As regard implications for future clinical research studies, randomized clinical studies are necessary to compare preparation designs with and without incisal coverage, and to provide clear descriptions of these preparation designs. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Bond strength of selected composite resin-cements to zirconium-oxide ceramic

    Science.gov (United States)

    Fons-Font, Antonio; Amigó-Borrás, Vicente; Granell-Ruiz, María; Busquets-Mataix, David; Panadero, Rubén A.; Solá-Ruiz, Maria F.

    2013-01-01

    Objectives: The aim of this study was to evaluate bond strengths of zirconium-oxide (zirconia) ceramic and a selection of different composite resin cements. Study Design: 130 Lava TM cylinders were fabricated. The cylinders were sandblasted with 80 µm aluminium oxide or silica coated with CoJet Sand. Silane, and bonding agent and/or Clearfil Ceramic Primer were applied. One hundred thirty composite cement cylinders, comprising two dual-polymerizing (Variolink II and Panavia F) and two autopolymerizing (Rely X and Multilink) resins were bonded to the ceramic samples. A shear test was conducted, followed by an optical microscopy study to identify the location and type of failure, an electron microscopy study (SEM and TEM) and statistical analysis using the Kruskal-Wallis test for more than two independent samples and Mann-Whitney for two independent samples. Given the large number of combinations, Bonferroni correction was applied (α=0.001). Results: Dual-polymerizing cements provided better adhesion values (11.7 MPa) than the autopolymerizing (7.47 MPa) (p-value M-WAdhesive failure (separation of cement and ceramic) was produced at a lesser force than cohesive failure (fracture of cement) (p-value M-Wcement and the ceramic. Key words:Shear bond strength, silica coating, surface treatment, zirconia ceramics, phosphate monomer. PMID:22926485

  8. Chemical and microstructural analyses for heavy metals removal from water media by ceramic membrane filtration.

    Science.gov (United States)

    Ali, Asmaa; Ahmed, Abdelkader; Gad, Ali

    2017-01-01

    This study aims to investigate the ability of low cost ceramic membrane filtration in removing three common heavy metals namely; Pb2+, Cu2+, and Cd2+ from water media. The work includes manufacturing ceramic membranes with dimensions of 15 by 15 cm and 2 cm thickness. The membranes were made from low cost materials of local clay mixed with different sawdust percentages of 0.5%, 2.0%, and 5.0%. The used clay was characterized by X-ray diffraction (XRD) and X-ray fluorescence analysis. Aqueous solutions of heavy metals were prepared in the laboratory and filtered through the ceramic membranes. The influence of the main parameters such as pH, initial driving pressure head, and concentration of heavy metals on their removal efficiency by ceramic membranes was investigated. Water samples were collected before and after the filtration process and their heavy metal concentrations were determined by chemical analysis. Moreover, a microstructural analysis using scanning electronic microscope (SEM) was performed on ceramic membranes before and after the filtration process. The chemical analysis results showed high removal efficiency up to 99% for the concerned heavy metals. SEM images approved these results by showing adsorbed metal ions on sides of the internal pores of the ceramic membranes.

  9. Evaluation of Monolithic Ceramics and Ceramic Thermal Barrier Coatings for Diesel Engine Applications

    National Research Council Canada - National Science Library

    Swab, Jeffrey J

    2001-01-01

    The Metals and Ceramics Research Branch (MCRB) of the Weapons and Materials Research Directorate is providing ceramic material characterization and evaluation to the Tank Automotive Research, Development, and Engineering Center (TARDEC...

  10. Optical properties of base dentin ceramics for all-ceramic restorations.

    OpenAIRE

    Shiraishi, Takanobu; Wood, Duncan J.; Shinozaki, Nobuya; Van Noort, Richard

    2011-01-01

    The study was conducted to compare the optical parameters of VM7(®) M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER(®) shade system.

  11. Final Project Report CFA-14-6357: A New Paradigm for Understanding Multiphase Ceramic Waste Form Performance

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, Kyle [Clemson Univ., SC (United States); Bordia, Rajendra [Clemson Univ., SC (United States); Reifsnider, Kenneth [Univ. of South Carolina, Columbia, SC (United States); Chiu, Wilson [Univ. of Connecticut, Storrs, CT (United States); Amoroso, Jake [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-12-28

    This project fabricated model multiphase ceramic waste forms with processing-controlled microstructures followed by advanced characterization with synchrotron and electron microscopy-based 3D tomography to provide elemental and chemical state-specific information resulting in compositional phase maps of ceramic composites. Details of 3D microstructural features were incorporated into computer-based simulations using durability data for individual constituent phases as inputs in order to predict the performance of multiphase waste forms with varying microstructure and phase connectivity.

  12. Synthesis of Micro/Nano Crystalline Ceramics

    Science.gov (United States)

    Mathew, Philip; Isac, Sheelakumari; Abraham, Rosalin; Isac, Jayakumari

    2008-04-01

    As a matter of fact almost every industrial production line, office and home is dependant on ceramic materials. Newly designed devices incorporate ceramic materials because of their useful chemical, electrical, mechanical, thermal and structural properties. The effectiveness of a large system depends critically on its ceramic components. That is ceramics are important, first because they comprise a large basic industry and second because their properties are essential for many applications. Ceramics are more stable than metals both in chemical and thermal environments. In this work the authors describes a method for the preparation of PBT ceramics material from lead oxide (PbO), barium carbonate and titanium oxide based on pre-calcinations of oxides. The results were analyzed by X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and TGA. XRD and SEM studies revealed that its particle size is in nanometer range. Dielectric studies were conducted at a frequency range of 100 KHz to 13 MHz. Mechanical properties were calculated.

  13. Ceramics as biomaterials for dental restoration.

    Science.gov (United States)

    Höland, Wolfram; Schweiger, Marcel; Watzke, Ronny; Peschke, Arnd; Kappert, Heinrich

    2008-11-01

    Sintered ceramics and glass-ceramics are widely used as biomaterials for dental restoration, especially as dental inlays, onlays, veneers, crowns or bridges. Biomaterials were developed either to veneer metal frameworks or to produce metal-free dental restorations. Different types of glass-ceramics and ceramics are available and necessary today to fulfill customers' needs (patients, dentists and dental technicians) regarding the properties of the biomaterials and the processing of the products. All of these different types of biomaterials already cover the entire range of indications of dental restorations. Today, patients are increasingly interested in metal-free restoration. Glass-ceramics are particularly suitable for fabricating inlays, crowns and small bridges, as these materials achieve very strong, esthetic results. High-strength ceramics are preferred in situations where the material is exposed to high masticatory forces.

  14. Process for making ceramic hot gas filter

    Science.gov (United States)

    Connolly, Elizabeth Sokolinski; Forsythe, George Daniel; Domanski, Daniel Matthew; Chambers, Jeffrey Allen; Rajendran, Govindasamy Paramasivam

    2001-01-01

    A ceramic hot-gas candle filter having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during backpulse cleaning and is resistant to chemical degradation at high temperatures.

  15. BasePetroCeram: a database for petrographic and geochemical analysis of archaeological ceramics

    OpenAIRE

    Barreau, Jean-Baptiste; Gehres, Benjamin

    2015-01-01

    International audience; Based on ceramics petrographic and geochemical studies, "BasePetroCeram" project aims to reference petrographic and geochemical analysis of archaeological ceramics from France. In the form of a secure database associated with a web interface, this tool allows a stronger recognition of ceramic bodies, as well as exchanges over long distances, but also collaboration of research teams and emergence of new issues. From a technical point of view, the web framework used is F...

  16. Synthesis and characterization of biomorphic ceramics; Sintese e caracterizacao de ceramicas biomorficas

    Energy Technology Data Exchange (ETDEWEB)

    Rambo, Carlos Renato

    2001-07-01

    Biotemplating represents a recently developed technology for manufacturing of biomorphous ceramics from naturally grown plant structures. This approach allows the production of ceramic materials with cellular structure, where the microstructural features of the ceramic product are similar to the native plant. After processing, the biomorphic ceramic exhibits directed pore morphology in the micrometer range. Biomorphic SiC fibers were produced from bamboo by carbothermal reduction of SiO{sub 2} originally present in the bamboo structure. Bamboo pieces were heated up to 1500 deg C in argon to promote the reaction between carbon and silica. Biomorphic alumina, mullite and zirconia ceramics were manufactured via the sol-gel route by repeated infiltration of low viscous oxide precursors (sols) into rattan, pine and bamboo structures. The raw samples were pyrolyzed at 800 deg C in nitrogen for 1h and subsequently annealed at 1550 deg C in air. The microstructure and physical properties of the biomorphic ceramics were characterized by X-ray diffraction (XRD) and high temperature-XRD, scanning electron microscopy (SEM), porosimetry and picnometry. Thermal analysis (TGA/DTA) was performed on the infiltrated samples in order to evaluate the reactions and the total weight loss during the thermal process. The mechanical properties were evaluated by compressive strength tests. In contrast to conventional processed ceramic foam of similar porosity, the microstructure highly porous biomorphic ceramics shows uniaxial pore morphology with anisotropic properties. These properties are favorable for applications in catalyst support, filters or low-density heat insulation structures, or as biomaterials. (author)

  17. X-ray shielding behaviour of kaolin derived mullite-barites ceramic

    Science.gov (United States)

    Ripin, A.; Mohamed, F.; Choo, T. F.; Yusof, M. R.; Hashim, S.; Ghoshal, S. K.

    2018-03-01

    Mullite-barite ceramic (MBC) is an emergent material for effective shielding of redundant ionizing radiation exposure. The composition dependent mechanical, thermal, and microstructure properties of MBC that makes MBC a high performing novel radiation shielding candidate remained unexplored. This paper examines the possibility of exploiting Malaysian kaolin (AKIM-35) and barite (BaSO4) derived ceramic (MBC) system for X-ray shielding operation. Using conventional pressing and sintering method six ceramic samples are prepared by mixing AKIM-35 with barite at varying contents (0, 10, 20, 30, 40 and 50 wt%). Synthesized pressed mixtures are calcined at 400 °C for 30 min and then sintered to 1300 °C for 120 min at a heating rate of 10 °C/min. Sintered samples are characterized via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), lead equivalent (LE), uniformity and dose reduction analyses. XRD pattern of prepared ceramics revealed the presence of monoclinic barium alumino-silicate (BAS) and orthorhombic mullite as major shielding phases together with other minor phase of barite and hexagonal quartz (SiO2) structures. Furthermore, FESEM images of ceramics (between 0 and 30 wt%) displayed the existence of compacted monoclinic plate of BAS and acicular mullite morphology (ceramics at 40 and 50 wt%). Radiation tests displayed the capacity of ceramics (at 0 and 10 wt%) to shield the X-ray radiation emanated at tube potential range of 50-120 kV. The highest radiation attenuation is ascertained at 70 kV where the dose is reduced remarkably between 99.11% and 97.42%. Ceramics at 0 and 10 wt% demonstrated the highest lead (Pb) equivalent thickness (LE) of 0.44 mm and 0.34 mm, respectively. It is established that such MBC may contribute towards the development of shielding material against ionizing radiation in diagnostic radiology (X-ray) dose range.

  18. The effect of water on the mechanical properties of soluble and insoluble ceramic cements.

    Science.gov (United States)

    Koh, Ilsoo; López, Alejandro; Pinar, Ana B; Helgason, Benedikt; Ferguson, Stephen J

    2015-11-01

    Ceramic cements are good candidates for the stabilization of fractured bone due to their potential ease of application and biological advantages. New formulations of ceramic cements have been tested for their mechanical properties, including strength, stiffness, toughness and durability. The changes in the mechanical properties of a soluble cement (calcium sulfate) upon water-saturation (saturation) was reported in our previous study, highlighting the need to test ceramic cements using saturated samples. It is not clear if the changes in the mechanical properties of ceramic cements are exclusive to soluble cements. Therefore the aim of the present study was to observe the changes in the mechanical properties of soluble and insoluble ceramic cements upon saturation. A cement with high solubility (calcium sulfate dihydrate, CSD) and a cement with low solubility (dicalcium phosphate dihydrate, DCPD) were tested. Three-point bending tests were performed on four different groups of: saturated CSD, non-saturated CSD, saturated DCPD, and non-saturated DCPD samples. X-ray diffraction analysis and scanning electron microscopy were also performed on a sample from each group. Flexural strength, effective flexural modulus and flexural strain at maximum stress, lattice volume, and crystal sizes and shape were compared, independently, between saturated and non-saturated groups of CSD and DCPD. Although material dissolution did not occur in all cases, all calculated mechanical properties decreased significantly in both CSD and DCPD upon saturation. The results indicate that the reductions in the mechanical properties of saturated ceramic cements are not dependent on the solubility of a ceramic cement. The outcome raised the importance of testing any implantable ceramic cements in saturated condition to estimate its in vivo mechanical properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. In situ hydroxyapatite nanofiber growth on calcium borate silicate ceramics in SBF and its structural characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Pu, Yinfu; Huang, Yanlin; Qi, Shuyun [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Chen, Cuili [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

    2015-10-01

    A novel calcium silicate borate Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramic was firstly prepared by the conventional solid-state reaction. In vitro hydroxyapatite mineralization was investigated by soaking the ceramics in simulated body fluid (SBF) solutions at body temperature (37 °C) for various time periods. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) measurements were applied to investigate the samples before and after the immersion of ceramics in SBF solution. The elemental compositions of a hydroxyapatite layer on the ceramics during the mineralization were confirmed by X-ray energy-dispersive spectra (EDS). Meanwhile, the bending strength and elastic modulus of Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics were also measured, which indicate that the biomaterials based on Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics possess bioactivity and might be a potential candidate as biomaterials for hard tissue repair. The bioactive mineralization ability was evaluated on the base of its crystal structural characteristics, i.e., silanol (Si–OH) and B–OH groups can be easily induced on the surface of Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics soaked in SBF solutions. - Highlights: • Calcium silicate borate Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} ceramics were developed as a new biomaterial. • Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} shows a superior in vitro bioactivity by inducing bone-like apatite. • Ca{sub 11}Si{sub 4}B{sub 2}O{sub 22} has good mechanical properties as potential candidate biomaterials. • The structure with SiO{sub 4} and BO{sub 3} groups is favorable for hydroxyapatite formation.

  20. Effect of Nb doping on sintering and dielectric properties of PZT ceramics

    Directory of Open Access Journals (Sweden)

    Ali Mirzaei

    2016-09-01

    Full Text Available The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4 mol% Nb-doped PZT (PZTN powders were successfully obtained by a solid-state reaction and calcination at 850 °C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD. In order to study morphology of powders, scanning electron microscopy (SEM was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 °C, with a heating rate of 10 °C/min, and holding time of 1–6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 °C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (εr ∼17960 with lower Curie temperature (∼358 °C relative to PZT (εr = 16000 at ∼363 °C as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.

  1. Salt splitting with ceramic membranes

    Energy Technology Data Exchange (ETDEWEB)

    Kurath, D. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    The purpose of this task is to develop ceramic membrane technologies for salt splitting of radioactively contaminated sodium salt solutions. This technology has the potential to reduce the low-level waste (LLW) disposal volume, the pH and sodium hydroxide content for subsequent processing steps, the sodium content of interstitial liquid in high-level waste (HLW) sludges, and provide sodium hydroxide free of aluminum for recycle within processing plants at the DOE complex. Potential deployment sites include Hanford, Savannah River, and Idaho National Engineering Laboratory (INEL). The technical approach consists of electrochemical separation of sodium ions from the salt solution using sodium (Na) Super Ion Conductors (NaSICON). As the name implies, sodium ions are transported rapidly through these ceramic crystals even at room temperatures.

  2. Silsesquioxane-derived ceramic fibres

    Science.gov (United States)

    Hurwitz, F. I.; Farmer, S. C.; Terepka, F. M.; Leonhardt, T. A.

    1991-01-01

    Fibers formed from blends of silsesquioxane polymers were characterized to study the pyrolytic conversion of these precursors to ceramics. The morphology of fibers pyrolyzed to 1400 C revealed primarily amorphous glasses whose conversion to beta-SiC is a function of both blend composition and pyrolysis conditions. Formation of beta-SiC crystallites within the glassy phase is favored by higher than stoichiometric C/Si ratios, while carbothermal reduction of Si-O bonds to form SiC with loss of SiO and CO occurs at higher methyl/phenylpropyl silsesquioxane (lower C/Si) ratios. As the carbothermal reduction is assumed to be diffusion controlled, the fibers can serve as model systems to gain understanding of the silsesquioxane pyrolysis behavior, and therefore are useful in the development of polysilsesquioxane-derived ceramic matrices and coatings as well.

  3. Ceramics: Durability and radiation effects

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C.; Lutze, W. [Univ. of New Mexico, Albuquerque, NM (United States); Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-05-01

    At present, there are three seriously considered options for the disposition of excess weapons plutonium: (1) incorporation, partial burn-up and direct disposal of MOX-fuel; (2) vitrification with defense waste and disposal as glass {open_quotes}logs{close_quotes}; (3) deep borehole disposal. The first two options provide a safeguard due to the high activity of fission products in the irradiated fuel and the defense waste. The latter option has only been examined in a preliminary manner, and the exact form of the plutonium has not been identified. In this paper, we review the potential for the immobilization of plutonium in highly durable crystalline ceramics apatite, pyrochlore, zirconolite, monazite and zircon. Based on available data, we propose zircon as the preferred crystalline ceramic for the permanent disposition of excess weapons plutonium.

  4. Manufacturing tailored property ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Ewsuk, K.G. [Sandia National Labs., Albuquerque, NM (United States). Ceramic Processing Science Dept.; Harrison, L.W. [E.I. du Pont de Nemours and Co., Inc., Wilmington, DE (United States). Central Research and Development Dept.

    1994-11-14

    Composite materials are desirable for many advanced engineering applications where the properties of a single phase material cannot meet all of the service requirements; however, existing process technology has limited the development and commercialization of composites. Lack of reproducible sintering to high density is one of the major obstacles to commercializing ceramic composites. Final-stage, non-reactive liquid phase sintering (NLPS) theory provides metrics for sinterability that can be used as guidelines to design and manufacture dense ceramic-filled-glass (CFG) composites. Additionally, within the constraints defined by the NLPS theory, sum-property models can be used to predict CFG composite properties, and to design composites with properties tailored to specific applications. By integrating composite process models with composite property models, processable, application-tailored CFG composites for microelectronics packaging have been designed and fabricated.

  5. Mullite Ceramics at Extreme Conditions

    Science.gov (United States)

    Kalita, Patricia; Cornelius, Andrew; Lipinska, Kris; Hemmers, Oliver; Sinogeikin, Stanislav; Fisher, Reinhard; Schneider, Hartmut

    2013-03-01

    Mullite is perhaps one of the most important phases in both traditional and advanced ceramics and thus one of the most widely studied ceramic phases. Even though the thermo-elastic behavior of mullites have been studied extensively (spectroscopy, diffraction, dilatometry, theoretical simulations), there are only few studies into the effects of pressure on mullites. This work aims at filling this gap by examining the role of oxygen vacancies on the mechanical stability and on the bulk modulus of mullite-type structures. DAAD, German Research Council, DFG No FI442/14-1. DOE-NNSA DE-FC08-01NV14049. DOE-BES, DOE-NNSA, NSF, DOD -TACOM, the W.M. Keck Found. DOE-BES, W-31-109-ENG-38.

  6. Experiences with voice to design ceramics

    DEFF Research Database (Denmark)

    Hansen, Flemming Tvede; Jensen, Kristoffer

    2014-01-01

    This article presents SoundShaping, a system to create ceramics from the human voice and thus how digital technology makes new possibilities in ceramic craft. The article is about how experiential knowledge that the craftsmen gains in a direct physical and tactile interaction with a responding....... The shape is output to a 3D printer to make ceramic results. The system demonstrates the close connection between digital technology and craft practice. Several experiments and reflections demonstrate the validity of this work....

  7. Tantalum-Based Ceramics for Refractory Composites

    Science.gov (United States)

    Stewart, David A.; Leiser, Daniel; DiFiore, Robert; Kalvala, Victor

    2006-01-01

    A family of tantalum-based ceramics has been invented as ingredients of high-temperature composite insulating tiles. These materials are suitable for coating and/or permeating the outer layers of rigid porous (foam-like or fibrous) ceramic substrates to (1) render the resulting composite ceramic tiles impervious to hot gases and (2) enable the tiles to survive high heat fluxes at temperatures that can exceed 3,000 F ( 1,600 C).

  8. Low-thermal expansion infrared glass ceramics

    Science.gov (United States)

    Lam, Philip

    2009-05-01

    L2 Tech, Inc. is in development of an innovative infrared-transparent glass ceramic material with low-thermal expansion (ZrW2O8) which has Negative Thermal Expansion (NTE). The glass phase is the infrared-transparent germanate glass which has positive thermal expansion (PTE). Then glass ceramic material has a balanced thermal expansion of near zero. The crystal structure is cubic and the thermal expansion of the glass ceramic is isotropic or equal in all directions.

  9. Synthesis of luminescent ceramics from alumina nanopowder

    Science.gov (United States)

    Kortov, V.; Kiryakov, A.; Ananchenko, D.; Zvonarev, S.

    2015-11-01

    The effect of the conditions of high-temperature synthesis in a reducing medium on the density, area and cathodoluminescence of ceramics made of compacted α-Al2O3 powder is the focus of this work. The dependence of the luminescence intensity on the temperature and duration of the synthesis of ceramics is presented. The optimal parameters for synthesis of luminescent ceramics from alumina nanopowder are defined.

  10. Multiphase-Multifunctional Ceramic Coatings

    Science.gov (United States)

    2013-06-30

    Ceramic Coatings Performing Organization names: Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional – Unidad Queretaro...University of California, Santa Barbara Principal Investigator / Organization: Dr . Luis Gerardo Trápaga Martínez CINVESTAV-Querétaro Principal...Investigator US collaboration / Organization: Dr . Carlos G. Levi University of California, Santa Barbara Reporting Period Final Dates covered

  11. Evaluation of bond strength of various margin ceramics to a zirconia ceramic

    NARCIS (Netherlands)

    Comlekoglu, M. Erhan; Dundar, Mine; Ozcan, Mutlu; Gungor, M. Ali; Gokce, Bulent; Artunc, Celal

    2008-01-01

    Objective: This study evaluated the bond strengths of four different margin ceramics based on fluoroapatite and feldspath to a zirconia ceramic. Methods: Zirconia cores (Zirconzahn) (N = 28, n = 7/margin ceramic group) were fabricated according to the manufacturers' instructions (diameter: 4 mm;

  12. Ceramic Technology Project database: March 1990 summary report. DOE/ORNL Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    Keyes, B.L.P.

    1992-07-01

    This report is the fifth in a series of semiannual data summary reports on information being stored in the Ceramic Technology Project (CTP) database. The overall system status as of March 31, 1990, is summarized, and the latest additions of ceramic mechanical properties data are given for zirconia, silicon carbide, and silicon nitride ceramic mechanical properties data, including some properties on brazed specimens.

  13. In vitro biocompatibility of a ferrimagnetic glass-ceramic for hyperthermia application.

    Science.gov (United States)

    Bretcanu, Oana; Miola, Marta; Bianchi, Claudia L; Marangi, Ida; Carbone, Roberta; Corazzari, Ingrid; Cannas, Mario; Verné, Enrica

    2017-04-01

    Ferrimagnetic glass-ceramics containing magnetite crystals were developed for hyperthermia applications of solid neoplastic tissue. The present work is focused on in vitro evaluation of the biocompatibility of these materials, before and after soaking in a simulated body fluid (SBF). X-ray diffraction, scanning electron microscopy, atomic absorption spectrophotometry, X-ray photoelectron spectrometry and pH measurements were employed in glass-ceramic characterisation. The free-radical mediated reactivity of the glass-ceramic was evaluated by Electron Paramagnetic Resonance (EPR) spin trapping. Cell adhesion and proliferation tests were carried out by using 3T3 murine fibroblasts. Cytotoxicity was performed by qualitative evaluation of human bone osteosarcoma cells U2OS cell line. The results show that almost two times more 3T3 cells proliferated on the samples pre-treated in SBF, compared with the untreated specimens. Moreover a decrease of confluence was observed at 48 and 72h for U2OS cells exposed to the untreated glass-ceramic, while the powder suspensions of glass-ceramic pre-treated in SBF did not influence the cell morphology up to 72h of exposition. The untreated glass-ceramic exhibited Fenton-like reactivity, as well as reactivity towards formate molecule. After pre-treatment with SBF the reactivity towards formate was completely suppressed. The concentration of iron released into the SBF solution was below 0.1ppm at 37°C, during one month of soaking. The different in vitro behaviour of the samples before and after SBF treatment has been correlated to the bioactive glass-ceramic surface modifications as detected by morphological, structural and compositional analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Ceramic technology for Advanced Heat Engines Project

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.

    1991-07-01

    Significant accomplishments in fabricating ceramic components for advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and database and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. An assessment of needs was completed, and a five year project plan was developed with extensive input from private industry. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities. This project is managed by ORNL for the Office of Transportation Technologies, Office of Transportation Materials, and is closely coordinated with complementary ceramics tasks funded by other DOE offices, NASA, DOD, and industry.

  15. Emerging ceramic-based materials for dentistry.

    Science.gov (United States)

    Denry, I; Kelly, J R

    2014-12-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. © International & American Associations for Dental Research.

  16. Ceramic-Metal Interfaces in Multilayer Actuators

    DEFF Research Database (Denmark)

    Engell, John; Pedersen, Henrik Guldberg; Andersen, Bjørn

    1996-01-01

    on the quality and strength of this interface. In the case of a weak ceramic-metal interface, delaminations will occur under severe working conditions.Work has been carried out on a commercial PZT type ceramic and various types of Pt electrode paste. The present study involves characterization of the interface......Multilayer actuators consist of a number of piezoelectric or electrostrictive ceramic layers, separated by thin metal electrodes. Thus, the ceramic-metal interface plays an even more important role than for bulk piezoceramics. The performance and durability of the actuator depends closely...

  17. Ceramic Technology For Advanced Heat Engines Project

    Energy Technology Data Exchange (ETDEWEB)

    1990-12-01

    Significant accomplishments in fabricating ceramic components for the Department of Energy (DOE), National Aeronautics and Space Administration (NASA), and Department of Defense (DoD) advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. The objective of the project is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. This advanced materials technology is being developed in parallel and close coordination with the ongoing DOE and industry proof of concept engine development programs. To facilitate the rapid transfer of this technology to U.S. industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities. Abstracts prepared for appropriate papers.

  18. Portland blended cements: demolition ceramic waste management

    Directory of Open Access Journals (Sweden)

    M. A. Trezza

    2017-01-01

    Full Text Available Demolition ceramic wastes (DCWs were investigated in order to determine their potential use as supplementary cementitious materials in Portland Blended Cements (PBCs. For this purpose, three ceramic wastes were investigated. After characterization of the materials used, the effect of ceramic waste replacement (8, 24 and 40% by mass was analyzed. Pozzolanic activity, hydration progress, workability and compressive strength were determined at 2, 7 and 28 days. The results showed that the ground wastes behave as filler at an early age, but as hydration progresses, the pozzolanic activity of ceramic waste contributes to the strength requirement.

  19. Manufacturing of superconductive silver/ceramic composites

    DEFF Research Database (Denmark)

    Seifi, Behrouz; Bech, Jakob Ilsted; Eriksen, Morten

    2000-01-01

    Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium, and cop......Manufacturing of superconducting metal/ceramic composites is a rather new discipline within materials forming processes. High Temperature SuperConductors, HTSC, are manufactured applying the Oxide-Powder-In-Tube process, OPIT. A ceramic powder containing lead, calcium, bismuth, strontium...

  20. Improved Slip Casting Of Ceramic Models

    Science.gov (United States)

    Buck, Gregory M.; Vasquez, Peter; Hicks, Lana P.

    1994-01-01

    Improved technique of investment slip casting developed for making precise ceramic wind-tunnel models. Needed in wind-tunnel experiments to verify predictions of aerothermodynamical computer codes. Ceramic materials used because of their low heat conductivities and ability to survive high temperatures. Present improved slip-casting technique enables casting of highly detailed models from aqueous or nonaqueous solutions. Wet shell molds peeled off models to ensure precise and undamaged details. Used at NASA Langley Research Center to form superconducting ceramic components from nonaqueous slip solutions. Technique has many more applications when ceramic materials developed further for such high-strength/ temperature components as engine parts.

  1. Post-fatigue fracture resistance of metal core crowns: press-on metal ceramic versus a conventional veneering system.

    Science.gov (United States)

    Solá-Ruiz, M Fernanda; Agustín-Panadero, Rubén; Campos-Estellés, Carlos; Labaig-Rueda, Carlos

    2015-04-01

    The aim of this in vitro study was to compare the mechanical failure behavior and to analyze fracture characteristics of metal ceramic crowns with two veneering systems - press-on metal (PoM) ceramic versus a conventional veneering system - subjected to static compressive loading. Forty-six crowns were constructed and divided into two groups according to porcelain veneer manufacture. Group A: 23 metal copings with porcelain IPS-InLine veneering (conventional metal ceramic). Group B: 23 metal copings with IPS-InLine PoM veneering porcelain. After 120,000 fatigue cycles, the crowns were axially loaded to the moment of fracture with a universal testing machine. The fractured specimens were examined under optical stereomicroscopy and scanning electron microscope. Fracture resistance values showed statistically significant differences (Student's t-test) regarding the type of ceramic veneering technique (p=0.001): Group A (conventional metal ceramics) obtained a mean fracture resistance of 1933.17 N, and Group B 1325.74N (Press-on metal ceramics). The most common type of fracture was adhesive failure (with metal exposure) (p=0.000). Veneer porcelain fractured on the occlusal surface following a radial pattern. Metal ceramic crowns made of IPS InLine or IPS InLine PoM ceramics with different laboratory techniques all achieved above-average values for clinical survival in the oral environment according to ISO 6872. Crowns made with IPS InLine by conventional technique resisted fracture an average of 45% more than IPS InLine PoM fabricated with the press-on technique. Key words:Mechanical failure, conventional feldspathic, pressable ceramic, chewing simulator, thermocycling, compressive testing, fracture types, scanning electron microscope.

  2. The effect of Zn contents on phase composition, chemical stability and cellular bioactivity in Zn-Ca-Si system ceramics.

    Science.gov (United States)

    Wu, Chengtie; Ramaswamy, Yogambha; Chang, Jiang; Woods, Joy; Chen, Yiqing; Zreiqat, Hala

    2008-11-01

    Ca-Si system ceramics, in particular CaSiO(3) ceramics, are regarded as potential bioactive bone repair/regeneration material. However, their high dissolution rate limits their biological applications. The aim of this study was to incorporate Zinc (Zn) into the Ca-Si system ceramics to produce part (at 10 and 20% Zn) or complete (at 50% Zn) new crystal phase (hardystonite: Ca(2)ZnSi(2)O(7)) with improved chemical stability and cellular activity. Zn-Ca-Si ceramics with four Zn contents (0, 10, 20, and 50%) were successfully prepared by sintering sol-gel-derived Zn-Ca-Si powder compacts. A new pure crystal phase Ca(2)ZnSi(2)O(7) was formed only when 50% Zn was added. The chemical stability of Zn-Ca-Si ceramics was evaluated by soaking in simulating body fluid (SBF), and the ion release from ceramics and the change in pH values of the SBF were measured. Their ability to form apatite in SBF was determined by analyzing the surface phase composition and morphology of the ceramics using X-ray diffraction and scanning electron microscopy (SEM). Results indicated that, with the increase of Zn contents, the chemical stability of ceramics increased while the apatite-formation ability decreased. The ability of Zn-Ca-Si ceramics to support attachment, proliferation, and differentiation of the human bone osteoblastic-like cells (HOB) was assessed using SEM, MTS, and alkaline phosphate activity assays, respectively. Zn-Ca-Si ceramics supported HOB attachment and their proliferation increased with the increase of Zn content. ALP activity of HOB on Zn-Ca-Si ceramics with 50% Zn (Ca(2)ZnSi(2)O(7)) was the highest among the levels obtained for the four ceramics tested. Taken together, Ca(2)ZnSi(2)O(7) ceramics possessed the best chemical stability and cellular bioactivity in Zn containing Ca-Si ceramics, indicating their potential application in skeletal tissue regeneration.

  3. Frost-resistance of red ceramic products

    Directory of Open Access Journals (Sweden)

    Ramires, M. V. V.

    2000-02-01

    Full Text Available The present work is a study about degradation occurring with red ceramics whenever they are exposed to the environmental conditions of a cold and humid climate. Four different types of clay from Rio Grande do Sul were studied: two of them from the Serra Geral formation, and the other two from the formation of Strada Nova, which are commonly used to make roof tiles. The clay was characterised to identify its chemical and mineralogical composition. Also the physical properties were researched. In the ceramic processing, the pressure with four different sintering temperatures (850ºC, 900ºC, 950ºC, and 1000ºC at three different intervals (3, 12, and 24 hours were used. The ceramic materials thus obtained were characterised according to their physical properties (water absorption, total density, porosity, and porous size, and mechanical (mechanical resistance over four points. For the characterisation of the degradation mechanism, some trials were carried out to obtain the coefficient of saturation and on frost and defrost cycles. The microstructural analysis was made with a scanning electronic microscopy. On the basis of the results obtained, a model for the degradation mechanism is presented, and a degradation factor which relates the total volume of mesopores to the standard size of mesopores is suggested. It was concluded that the red ceramic products more prone to be frost-resistant are those presenting a degradation factor below 100.

    Se estudia la degradación que sufre la cerámica roja cuando se expone a la acción de los climas fríos e húmedos. La experimentación se ha realizado con cuatro arcillas de la son expuestas a los climas fríos y húmedos. Se investigaron cuatro diferentes arcillas de la provincia del Rio Grande do Sul, que se emplean tradicionalmente en la fabricación de tejas. Dos de ellas pertenecen a la formación de la Serra Geral y las otras dos de la formación Estrada Nova. La caracterización de las arcillas

  4. Applications of Modern Analysis Techniques in Searching back Ancient Art Ceramic Technologies

    Directory of Open Access Journals (Sweden)

    Nguyen Quang Liem

    2011-12-01

    Full Text Available This report highlights the promising applications of modern analysis techniques such as Scanning Electron Microsopy, X-ray fluorescence, X-ray diffraction, Raman scattering spectroscopy, and thermal expansion measurement in searching back the ancient art ceramics technologies.

  5. Optical properties of ytterbium-doped yttrium oxide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Solomonov, V.I.; Maksimov, R.N. [Institute of Electrophysics UrB RAS, Amundsena 106, 620016 Ekaterinburg (Russian Federation); Ural Federal University Named After the First President of Russia B.N. Yeltsin, Mira 19, 620002 Ekaterinburg (Russian Federation); Osipov, V.V.; Shitov, V.A.; Lipchak, A.I. [Institute of Electrophysics UrB RAS, Amundsena 106, 620016 Ekaterinburg (Russian Federation)

    2017-05-15

    Ytterbium-doped yttrium oxide (Yb:Y{sub 2}O{sub 3}) transparent ceramics with different sintering additives (Lu{sub 2}O{sub 3}, Sc{sub 2}O{sub 3}, CeO{sub 2}, ZrO{sub 2}, or HfO{sub 2}) were fabricated using nanopowders produced by laser ablation. Transmission and photoluminescence spectra of the obtained ceramics were investigated at room temperature. Highest in-line transmittance was over 80% at the wavelength of 1060 nm for 2 mm thick Yb:Y{sub 2}O{sub 3} ceramics with zirconium and hafnium. Divalent Yb ions with the ground state electron configuration 4f{sup 13}6s were revealed. The absorption and emission bands caused by s <-> s transitions of these ions were observed in the IR spectral range of Yb{sup 3+} ions. The superposition of both Yb{sup 3+} and Yb{sup 2+} emission bands leads to an effective broadening of the whole luminescence band. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Radiation-disorder and aperiodicity in irradiated ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, L.W.

    1992-01-01

    This final technical report documents the accomplishments of the program of research entitled Radiation Disorder and Aperiodicity in Irradiated Ceramics'' for the period June 22, 1989--June 21, 1992. This research forms the latest part on an on-going program, begun at MIT in 1983 under DOE support, which has had as its objectives investigation of the responses in radiation environments of ceramics heavily-irradiated with electrons, neutrons and ions, with potential applications to fusion energy technology and high-level nuclear waste storage. Materials investigated have included SiO{sub 2}, MgAl{sub 2}O{sub 4}, Al{sub 23}O{sub 27}N{sub 5}, SiC, BeO, LiAlO{sub 2}, Li{sub 2}ZrO{sub 3}, CaTiO{sub 3}KTaO{sub 3} and Ca(Zr, Pu)Ti{sub 2}O{sub 7}. The program initially proposed for 1989 had as its major objectives two main thrusts: (1) research on defect aggregation in irradiated non-oxide ceramics, and (2) research on irradiation-induced amorphization of network silicas and phosphates.

  7. Radiation damage of hollandite in multiphase ceramic waste forms

    Science.gov (United States)

    Clark, Braeden M.; Tumurgoti, Priyatham; Sundaram, S. K.; Amoroso, Jake W.; Marra, James C.; Shutthanandan, Vaithiyalingam; Tang, Ming

    2017-10-01

    Radiation damage was simulated in multiphase titanate-based ceramic waste forms using an ion accelerator to generate high energy alpha particles (He+) and an ion implanter to generate 7 MeV gold (Au3+) particles. X-ray diffraction and transmission electron microscopy were used to characterize the damaged surfaces and nearby regions. Simulated multiphase ceramic waste forms were prepared using two processing methods: spark plasma sintering and melt-processing. Both processing methods produced ceramics with similar phase assemblages consisting of hollandite-, zirconolite/pyrochlore-, and perovskite-type phases. The measured heavy ion (Au3+) penetration depth was less in spark plasma sintered samples than in melt-processed samples. Structural breakdown of the hollandite phase occurred under He+ irradiation indicated by the presence of x-ray diffraction peaks belonging to TiO2, BaTiO5, and other hollandite related phases (Ba2Ti9O20). The composition of the constituent hollandite phase affected the extent of damage induced by Au3+ ions.

  8. Use of basaltic waste as red ceramic raw material

    Directory of Open Access Journals (Sweden)

    T. M. Mendes

    Full Text Available Abstract Nowadays, environmental codes restrict the emission of particulate matters, which result in these residues being collected by plant filters. This basaltic waste came from construction aggregate plants located in the Metropolitan Region of Londrina (State of Paraná, Brazil. Initially, the basaltic waste was submitted to sieving (< 75 μm and the powder obtained was characterized in terms of density and particle size distribution. The plasticity of ceramic mass containing 0%, 10%, 20%, 30%, 40% and 50% of basaltic waste was measured by Atterberg method. The chemical composition of ceramic formulations containing 0% and 20% of basaltic waste was determined by X-ray fluorescence. The prismatic samples were molded by extrusion and fired at 850 °C. The specimens were also tested to determine density, water absorption, drying and firing shrinkages, flexural strength, and Young's modulus. Microstructure evaluation was conducted by scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry. Basaltic powder has similar physical and chemical characteristics when compared to other raw materials, and contributes to ceramic processing by reducing drying and firing shrinkage. Mechanical performance of mixtures containing basaltic powder is equivalent to mixtures without waste. Microstructural aspects such as pore size distribution were modified by basaltic powder; albite phase related to basaltic powder was identified by X-ray diffraction.

  9. Verification of creep performance of a ceramic gas turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Lin, H.T.; Becher, P.F.; Ferber, M.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Parthasarathy, V. [Solar Turbines Inc., San Diego, CA (United States)

    1998-03-01

    Tensile creep tests were carried out on a Norton NT164 silicon nitride ceramic turbine blade containing 4 wt. % Y{sub 2}O{sub 3} sintering additive at 1,370 C in air under selected stress levels. The objective of this study was to measure the creep properties of test specimens extracted from a complex shaped ceramic gas turbine blade to verify the response of actual components. The creep results indicated that specimens from both the airfoil and dovetail sections exhibited creep rates that were about 4 to 100 times higher than those obtained from both the buttonhead and dogbone creep specimens machined from the developmental billets fabricated with the same composition and processing procedures. Electron microscopy analyses suggested that high creep rates and short lifetimes observed in specimens extracted from the turbine blade resulted from a higher glassy phase(s) content and smaller number density of elongated grain microstructure. Silicon nitride ceramics with an in-situ reinforced elongated microstructure have been the primary candidates for both advanced automotive and land-based gas turbine engine applications.

  10. Microstructure and properties of LZSA glass-ceramic foams

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, E. de [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Rambo, C.R. [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Department of Chemical Engineering-EQA, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil)], E-mail: Rambo@enq.ufsc.br; Hotza, D. [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Department of Chemical Engineering-EQA, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Oliveira, A.P. Novaes de [Graduate Program on Materials Science and Engineering-PGMAT, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Department of Mechanical Engineering-EMC, Federal University of Santa Catarina-UFSC, P.O. Box 476, 88040-900 Florianopolis, SC (Brazil); Fey, T.; Greil, P. [Department of Materials Science, Glass and Ceramics, University of Erlangen-Nuremberg, Martensstrasse 5, D-91058 Erlangen (Germany)

    2008-03-15

    Commercial polyurethane foams with a monomodal pore size distribution were used to produce LZSA glass-ceramic foams by the polymeric sponge method. A suspension containing LZSA glass powder, bentonite and sodium silicate was prepared in isopropanol to impregnate the polymeric foams by dip coating. The sintering conditions were varied in the range of 700-850 deg. C for 30-180 min. The cellular microstructure of glass-ceramic foams was characterized by scanning electron microscopy (SEM) and micro-computer X-ray tomography ({mu}CT). Optimum physical, mechanical and fluidynamic properties of the LZSA glass-ceramic foams were obtained at 750 deg. C for 60 min. Main crystalline phases detected were {beta}-spodumene and zirconium silicate. The compressive strength of the foams (0.1-10 MPa) is strongly dependent on their overall porosity and their behaviour could be explained using the Gibson-Ashby model. The Darcyan permeability of LZSA foams was found to be in the range of 0.1-4 x 10{sup -9} m{sup 2}, which is in the order of magnitude of cellular supports for aerosol filters, and, therefore, suitable for several other technological applications.

  11. High-temperature-pressure polymerized resin-infiltrated ceramic networks.

    Science.gov (United States)

    Nguyen, J F; Ruse, D; Phan, A C; Sadoun, M J

    2014-01-01

    The aim of this study was to produce composite blocks (CB) for CAD/CAM applications by high-temperature-pressure (HT/HP) polymerization of resin-infiltrated glass-ceramic networks. The effect of network sintering and the absence/presence of initiator was investigated. Mechanical properties were determined and compared with those of Paradigm MZ100 (3M ESPE) blocks and HT/HP polymerized experimental "classic" CB, in which the filler had been incorporated by conventional mixing. The networks were made from glass-ceramic powder (VITA Zahnfabrik) formed by slip casting and were either sintered or not. They were silanized, infiltrated by urethane dimethacrylate, with or without initiator, and polymerized under HT/HP (300 MPa, 180°C) to obtain resin-infiltrated glass-ceramic network (RIGCN) CB. HT/HP polymerized CB were also made from an experimental "classic" composite. Flexural strength (σf), fracture toughness (KIC), and Vickers hardness were determined and analyzed by one- or two-way analysis of variance (ANOVA), Scheffé multiple-means comparisons (α = 0.05), and Weibull statistics (for σf). Fractured surfaces were characterized with scanning electron microscopy. The mechanical properties of RIGCN CB were significantly higher. Sintering induced significant increases in σf and hardness, while the initiator significantly decreased hardness. The results suggested that RIGCN and HT/HP polymerization could be used to obtain CB with superior mechanical properties, suitable for CAD/CAM applications.

  12. Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Gonsalves, Anthony; Nakamura, Kei; Lin, Chen; Osterhoff, Jens; Shiraishi, Satomi; Schroeder, Carl; Geddes, Cameron; Toth, Csaba; Esarey, Eric; Leemans, Wim

    2011-03-23

    A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy provided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.

  13. Measurement of the T quark mass in the electron-muon channel with the D0 detector at the Tevatron; Mesure de la masse du quark top dans le canal electron-muon aupres du detecteur D0 au TeVatron

    Energy Technology Data Exchange (ETDEWEB)

    Arthaud, M

    2008-06-15

    The standard model of particle physics is a theory that describes the elementary components of matter and their interactions. The top quark is the heaviest elementary particle described by this model and its mass is one of its free parameters. The measurement of this mass constrains the Higgs boson mass. At the moment of this study, it can be observed only with the 2 detectors located around the Tevatron which collides protons and antiprotons at a centre of mass energy of {radical}(s) = 1.96 TeV. In this thesis, the Run-II b data collected by the D0 detector between June 2006 and August 2007 (around 1 fb{sup -1}) have been analysed. The top quark is mainly produced by pairs and it decays in almost 100% of the time into a W boson and a bottom quark. In the final state studied here, one of the W bosons decays into an electron and a neutrino and the second one into a muon and a neutrino. Such a final state requires to control tightly the muon transverse momentum precision measurement. Events containing Z and J/{psi} decaying into 2 muons have been studied to adjust the momentum precision in simulated events to one observed in data. During the analysis, 77 top-anti-top events have been selected in the electron-muon channel to determine the top quark mass with a method based on the Monte-Carlo integration of the matrix element describing the production of a top-anti-top pair decaying into an electron and a muon. This yields a top quark mass value of m(top) equals (172 {+-} 4.2 (sta) {+-} 2.5 (syst)) GeV. (author)

  14. Luminescence characterization of dental ceramics for individual retrospective dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Correcher, V.; Gomesdarocha, R. [CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Garcia G, J. [Consejo Superior de Investigaciones Cientificas, Museo Nacional de Ciencias Naturales, Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Rivera M, T., E-mail: v.correcher@ciemat.es [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico)

    2015-10-15

    Full text: Ceramic materials in general and dental crowns in particular exhibit thermoluminescence (Tl) properties and are of interest in the field of individual retrospective dosimetry. This property could be potentially employed to provide a means of determining cumulative exposure to external gamma radiation arising from accidents or large-scale incidents (radiological terrorism) involving population groups where conventional monitoring has not been established. The thermal stability and dose effect of the UV-blue Tl emission of a well characterized Spanish samples (by means of cathodoluminescence and electron-probe microanalysis) are here reported. It displays (i) an excellent linearity in the range of 0.12 - 9.6 Gy, (II) good stability of the Tl signal of 0.6, 1.2 and 2.4 Gy irradiated samples after 6 months of storage showing an initial rapid decay (ca. 30%) maintaining the stability from 30 days onwards. It means that the electron population decreases asymptotically by the X - axis and the involved electrons are located in deeper traps at room temperature. (III) The reusability performed on the dental ceramic, involving successive cycles of irradiation (1.2 Gy) followed by readout (up to 500 degrees C), exhibited a negligible variation in the Tl response, when measured six times. (IV) The tests of thermal stability at different temperatures (in the range of 100-240 degrees C) confirms a continuum in the trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the maximum peak. Therefore, these preliminary results suggest that dental ceramics could be used as suitable dosimeters in retrospective conditions. (Author)

  15. Crystallization behavior during melt-processing of ceramic waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Tumurugoti, Priyatham; Sundaram, S.K.; Misture, Scott T. [Kazuo Inamori School of Engineering, The New York State College of Ceramics, Alfred University, Alfred, NY, 14802 (United States); Marra, James C. [Savannah River National Laboratory, Aiken, SC, 29808 (United States); Amoroso, Jake, E-mail: jake.amoroso@srs.gov [Savannah River National Laboratory, Aiken, SC, 29808 (United States)

    2016-05-15

    Multiphase ceramic waste forms based on natural mineral analogs are of great interest for their high chemical durability, radiation resistance, and thermodynamic stability. Melt-processed ceramic waste forms that leverage existing melter technologies will broaden the available disposal options for high-level nuclear waste. This work reports on the crystallization behavior in selected melt-processed ceramics for waste immobilization. The phase assemblage and evolution of hollandite, zirconolite, pyrochlore, and perovskite type structures during melt processing were studied using thermal analysis, x-ray diffraction, and electron microscopy. Samples prepared by melting followed by annealing and quenching were analyzed to determine and measure the progression of the phase assemblage. Samples were melted at 1500 °C and heat-treated at crystallization temperatures of 1285 °C and 1325 °C corresponding to exothermic events identified from differential scanning calorimetry measurements. Results indicate that the selected multiphase composition partially melts at 1500 °C with hollandite coexisting as crystalline phase. Perovskite and zirconolite phases crystallized from the residual melt at temperatures below 1350 °C. Depending on their respective thermal histories, different quenched samples were found to have different phase assemblages including phases such as perovskite, zirconolite and TiO{sub 2.} - Highlights: • Crystallization behavior during melt processing multiphase ceramics was studied. • Phase evolution order upon cooling was hollandite → perovskite → zirconolite → TiO{sub 2}. • Hollandite phases co-exists with a liquid phase at temperatures >1500 °C. • Zirconolite crystallization is complex and involves intermediate phases.

  16. [An experimental study of the wear behavior of dental feldspathic glass-ceramic and lithium disilicate glass-ceramic].

    Science.gov (United States)

    Tian, Bei-min; Zhang, Shao-feng; He, Lin; Guo, Jia-wen; Yu, Jin-tao; Wu, Xiao-hong

    2013-11-01

    To investigate the tribology characteristics of two ceramic materials in vitro:feldspathic glass-ceramic (veneer porcelain) and lithium disilicate glass-ceramic (heat-pressed ceramic), and to evaluate the wear resistance of different ceramic materials from the dynamic chewing perspective. Wear tests were performed in simulated oral environment with stainless steel ball antagonists (r = 3 mm), veneer porcelain (CERAMCO 3) and heat-pressed ceramic (IPS e.max Press HT type) in the chewing simulator. The tribological tests were carried out under artificial saliva lubrication condition in room temperature with a vertical load of 10 N for 1.2×10(6) cycles (f = 1.5 Hz, uniform circular motion, revolving speed = 90 r/min, radius = 0.5 mm). The wear volumes were measured using three-dimensional profiling, and surface microscopic morphology were observed using scanning electron microscopy at time point of 200 000, 400 000, 600 000, 800 000, 1 000 000, and 1 200 000 cycles. In a simulated oral environment, the wear rates of veneer porcelain were (0.001 20 ± 0.00 018) , (0.000 10 ± 0.000 03) , (0.000 50 ± 0.000 05), (0.000 10 ± 0.000 02) , (0.004 10 ± 0.000 38) , and (0.019 00 ± 0.003 53) (×10(-4) mm(3)/cycles) at 200 000, 400 000, 600 000, 800 000, 1 000 000, 1 200 000 cycles. The wear rates of heat-pressed ceramic were (0.139 50 ± 0.030 94), (0.124 40 ± 0.031 20), (0.054 80 ± 0.005 38), (0.038 80 ± 0.006 10), (0.011 10 ± 0.003 75), (0.198 90 ± 0.045 80) (×10(-4) mm(3)/cycles) at 200 000, 400 000, 600 000, 800 000, 1 000 000, 1 200 000 cycles. Three stages were observed in the wear loss process of the two materials: running-in stage, steady wear stage and severe wear stage. In running-in and steady wear stage, the shallow wear tracks of veneer porcelain were produced by the fatigue effect.While in severe wear stage, the wear tracks turned into ploughing. In running-in stage, the surface of heat-pressed ceramic was characterized by dense and shallow ploughing

  17. EPR of transition metal ions in NZP ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Yegor`kova, O.; Kryukova-Orlova, A.I. [Univ. of Nizhnii Novgorod (Russian Federation); Stefanovsky, S.V. [SIA Radon, Moscow (Russian Federation)

    1995-12-31

    NZP-ceramics have been produced by different methods such as sol-gel, flux melting and sintering of dry salts or phosphates. Formation of NZP and related phases was confirmed by X-ray diffraction analysis. Electron paramagnetic resonance (EPR) was applied to evaluate a structure positions of paramagnetic ions and nature of radiation-induced centers. EPR responses from transition metal ions Fe{sup 3+} and Mn{sup 2+} with electron configuration 3d{sup 5} (ground state {sup 6}S{sub 5/2}) which occurred as impurities in raw materials were registered in powders of NZP-ceramics. Fine structure arising due to high spin iron complexes is well resolved. A part of Fe{sup 3+} ions substitutes for Zr{sup 4+} and another part of one substitutes for Na{sup +} ions in six-fold coordinated positions. A great value of hyperfine structure (hfs) constant (9.3 mT) shows a high ionic character of Mn-O bonds in the first coordination sphere. A coordination number is close to 6. Fine structure of Mn{sup 2+} ions are not well resolved. A comparison of the spectra of samples containing various alkali cations shows the substitution for cations in series of Li-Na-K-Rb-Cs does not result in fundamental variation in spectra except for CZP ceramics where the response with g=4.3 due to Fe{sup 3+} in strong ligand field rather than response with g=2.0 due to Fe{sup 3+} in weak field is observed. An investigation of some samples doped by 0.1...0.5 mole % of Fe{sup 3+} or Gd{sup 3+} has been carried out and principal spin-Hamiltonian parameters have been determined. The increase of Fe and Gd ions content as compared to impurity substituting for Zr and possibly Na in their own structural positions results in noticeable site distortion. Gamma irradiation of NZP ceramics results in formation of radiation-induced paramagnetic centers connected to phosphorus-oxygen. The nature and concentration of these centers depend on production method. The lowest defect concentration is in hot-pressed ceramics.

  18. What every surgeon should know about Ceramic-on-Ceramic bearings in young patients

    Science.gov (United States)

    Hernigou, Philippe; Roubineau, François; Bouthors, Charlie; Flouzat-Lachaniette, Charles-Henri

    2016-01-01

    Based on the exceptional tribological behaviour and on the relatively low biological activity of ceramic particles, Ceramic-on-Ceramic (CoC) total hip arthroplasty (THA) presents significant advantages CoC bearings decrease wear and osteolysis, the cumulative long-term risk of dislocation, muscle atrophy, and head-neck taper corrosion. However, there are still concerns regarding the best technique for implantation of ceramic hips to avoid fracture, squeaking, and revision of ceramic hips with fracture of a component. We recommend that surgeons weigh the potential advantages and disadvantages of current CoC THA in comparison with other bearing surfaces when considering young very active patients who are candidates for THA. Cite this article: Hernigou P, Roubineau F, Bouthors C, Flouzat-Lachaniette C-H. What every surgeon should know about Ceramic-on-Ceramic bearings in young patients. EFORT Open Rev 2016;1:107-111. DOI: 10.1302/2058-5241.1.000027. PMID:28461936

  19. Improving the strength of ceramics by controlling the interparticle forces and rheology of the ceramic suspensions

    CERN Document Server

    Chou, Y P

    2001-01-01

    This thesis describes a study of the modification of the interparticle forces of colloidal ceramic particles in aqueous suspensions in order to improve the microstructural homogeneity, and hence the reliability and mechanical performances, of subsequently formed ceramic compacts. A concentrated stable fine ceramic powder suspension has been shown to be able to generate a higher density of a ceramic product with better mechanical, and also electrical, electrochemical and optical, properties of the ceramic body. This is because in a colloidally stable suspension there are no aggregates and so defect formation, which is responsible for the ceramic body performance below its theoretical maximum, is reduced. In order to achieve this, it is necessary to form a well dispersed ceramic suspension by ensuring the interparticle forces between the particles are repulsive, with as a high a loading with particles as possible. By examining the rheological behaviour and the results of Atomic Force Microscope, the dispersion ...

  20. Ceramic Technology Project database: September 1990 summary report

    Energy Technology Data Exchange (ETDEWEB)

    Keyes, B.L.P.

    1992-06-01

    Data generated within the Ceramic Technology Project (CTP) represent a valuable resource for both research and industry. The CTP database was created to provide easy access to this information in electronic and hardcopy forms by using a computerized database and by issuing periodic hardcopy reports on the database contents. This report is the sixth in a series of semiannual database summaries and covers recent additions to the database, including joined brazed specimen test data. It covers 1 SiC, 34 SiN, 10 whisker-reinforced SiN, 2 zirconia-toughened aluminas, 8 zirconias, and 34 joints.