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Sample records for aligned yttria-stabilized zirconia

  1. Room temperature growth of biaxially aligned yttria-stabilized zirconia films on glass substrates by pulsed-laser deposition

    CERN Document Server

    Li Peng; Mazumder, J

    2003-01-01

    Room temperature deposition of biaxially textured yttria-stabilized zirconia (YSZ) films on amorphous glass substrates was successfully achieved by conventional pulsed-laser deposition. The influence of the surrounding gases, their pressure and the deposition time on the structure of the films was studied. A columnar growth process was revealed based on the experimental results. The grown biaxial texture appears as a kind of substrate independence, which makes it possible to fabricate in-plane aligned YSZ films on various substrates.

  2. Interaction of NiO with yttria-stabilized zirconia

    DEFF Research Database (Denmark)

    Kuzjukevics, A.; Linderoth, Søren

    1997-01-01

    As-prepared and heat treated plasma-produced 8 and 10 mol% yttria-stabilized zirconia (YSZ) powders doped with 0, 5, 10 and 75 mol% NiO have been investigated by XRD. The as-prepared powders are mixtures of metastable tetragonal and cubic phases but they transform to a single YSZ phase upon heat...... treatment above 1200 degrees C. The solubility of NiO in yttria-stabilized zirconia is less than 2 mol% at 1600 degrees C and varies little within the investigated yttria concentration range. The solubility increases with increasing temperature and the total NiO concentration. The activation energy...

  3. Electronic properties of ion-implanted yttria-stabilized zirconia

    NARCIS (Netherlands)

    Vohrer, U.; Wiemhöfer, H.-D.; Göpel, W.; Hassel, van B.A.; Burggraaf, A.J.

    1993-01-01

    Ion implantation of iron and titanium has been applied to modify the surface properties of polycrystalline yttria-stabilized zirconia ((ZrO2)0.87(YO1.5)0.13 (YSZ)) discs in an attempt to prepare surfaces with a mixed conductivity and by this an enhanced surface oxygen exchange kinetics. Surface-sen

  4. Scandia-and-Yttria-Stabilized Zirconia for Thermal Barriers

    Science.gov (United States)

    Mess, Derek

    2003-01-01

    yttria in suitable proportions has shown promise of being a superior thermal- barrier coating (TBC) material, relative to zirconia stabilized with yttria only. More specifically, a range of compositions in the zirconia/scandia/yttria material system has been found to afford increased resistance to deleterious phase transformations at temperatures high enough to cause deterioration of yttria-stabilized zirconia. Yttria-stabilized zirconia TBCs have been applied to metallic substrates in gas turbine and jet engines to protect the substrates against high operating temperatures. These coatings have porous and microcracked structures, which can accommodate strains induced by thermal-expansion mismatch and thermal shock. The longevity of such a coating depends upon yttria as a stabilizing additive that helps to maintain the zirconia in an yttria-rich, socalled non-transformable tetragonal crystallographic phase, thus preventing transformation to the monoclinic phase with an associated deleterious volume change. However, at a temperature greater than about 1,200 C, there is sufficient atomic mobility that the equilibrium, transformable zirconia phase is formed. Upon subsequent cooling, this phase transforms to the monoclinic phase, with an associated volume change that adversely affects the integrity of the coating. Recently, scandia was identified as a stabilizer that could be used instead of, or in addition to, yttria. Of particular interest are scandia-and-yttria-stabilized zirconia (SYSZ) compositions of about 6 mole percent scandia and 1 mole percent yttria, which have been found to exhibit remarkable phase stability at a temperature of 1,400 C in simple aging tests. Unfortunately, scandia is expensive, so that the problem becomes one of determining whether there are compositions with smaller proportions of scandia that afford the required high-temperature stability. In an attempt to solve this problem, experiments were performed on specimens made with reduced

  5. Phase diagram for a nano-yttria-stabilized zirconia system

    DEFF Research Database (Denmark)

    Asadikiya, Mohammad; Sabarou, Hooman; Chen, Ming;

    2016-01-01

    Due to the attractive properties of nanoparticles because of their effective surface area, they have been studied widely. Nano-yttria-stabilized zirconia (n-YSZ) is a ceramic which has been scrutinized extensively in past years. Because of the different stability behavior of n-YSZ in comparison...... with bulk YSZ, a new phase diagram is needed for the n-YSZ system in order to identify stable phases under various conditions. In this study, a phase diagram for the n-YSZ system was provided to determine phase stability ranges at room temperature with respect to particle size and composition....... By applying the CALPHAD approach, a 3-D phase diagram for the n-YSZ system was established in which the stability range of each individual phase can be predicted based on the particle size, composition, and temperature....

  6. Radiation tolerance of nanocrystalline ceramics: insights from Yttria Stabilized Zirconia.

    Science.gov (United States)

    Dey, Sanchita; Drazin, John W; Wang, Yongqiang; Valdez, James A; Holesinger, Terry G; Uberuaga, Blas P; Castro, Ricardo H R

    2015-01-13

    Materials for applications in hostile environments, such as nuclear reactors or radioactive waste immobilization, require extremely high resistance to radiation damage, such as resistance to amorphization or volume swelling. Nanocrystalline materials have been reported to present exceptionally high radiation-tolerance to amorphization. In principle, grain boundaries that are prevalent in nanomaterials could act as sinks for point-defects, enhancing defect recombination. In this paper we present evidence for this mechanism in nanograined Yttria Stabilized Zirconia (YSZ), associated with the observation that the concentration of defects after irradiation using heavy ions (Kr(+), 400 keV) is inversely proportional to the grain size. HAADF images suggest the short migration distances in nanograined YSZ allow radiation induced interstitials to reach the grain boundaries on the irradiation time scale, leaving behind only vacancy clusters distributed within the grain. Because of the relatively low temperature of the irradiations and the fact that interstitials diffuse thermally more slowly than vacancies, this result indicates that the interstitials must reach the boundaries directly in the collision cascade, consistent with previous simulation results. Concomitant radiation-induced grain growth was observed which, as a consequence of the non-uniform implantation, caused cracking of the nano-samples induced by local stresses at the irradiated/non-irradiated interfaces.

  7. Graphene nanosheet-induced toughening of yttria-stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Su, Jianan; Chen, Yao; Huang, Qiqi [Soochow University, School of Mechanical and Electric Engineering, Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou (China)

    2017-01-15

    Graphene nanosheet (GNS)-reinforced yttria-stabilized tetragonal zirconia polycrystals (TZP) were synthesized using spark plasma sintering (SPS), and the influences of the added GNSs on microstructure evolution and the microscopic mechanical properties of the sintered composites were investigated. Raman spectroscopy and microstructure observation corroborated that these added GNSs, which can survive the harsh SPS processing condition, homogeneously distribute in the matrix of all composites to hinder significantly the grain growth. In comparison with the monolithic TZP, the indentation fracture toughness of a GNS/TZP composite reaches maximum value and increases by up to ∝36% (from ∝4.1 to ∝5.6 MPa m{sup 0.5}) even at 0.5% weight fraction, GNS pullout, crack bridging, crack deflection, and crack branching are responsible for the increased fracture toughness. The computed energy dissipation by GNS pullout decreases with increasing the number of graphene layers due to weak bonding between them, and therefore, graphene agglomeration would impair toughening effect. Moreover, scratch studies suggest that GNS/TZP composites exhibit improved scratch resistance due to the fact that GNSs are promising reinforcing and lubricating nanofillers in ceramic composites. (orig.)

  8. Porous Yttria-Stabilized Zirconia Microstructures for SOFC Anode Fabrication

    Science.gov (United States)

    Palakkathodi Kammampata, Sanoop

    Solid oxide fuel cells (SOFCs) are electrochemical devices that convert fuels, such as hydrogen and natural gas, to electricity at high efficiencies, e.g., up to 90 %. SOFCs are emerging as a key technology for energy production that also minimize greenhouse gas emissions compared to conventional thermal power generation. SOFCs, which are normally based on nickel-yttria stabilized zirconia (YSZ) anodes, undergo degradation with time due to their high operating temperatures and their susceptibility to damage due to anode oxidation (redox cycling) and poisoning. Ni infiltration into porous YSZ scaffolds is considered to be a promising approach for overcoming some of these problems and enhancing their redox tolerance. However, long-term instability of the morphology of these types of anodes is an important problem. The focus of this thesis was therefore to develop methods to form porous YSZ scaffolds and attempt to construct stable Ni-YSZ anodes with reasonable electrochemical performance by infiltration. In this work, the issue of long-term instability was considered to originate from both the porous YSZ scaffold microstructure and the Ni infiltration precursor employed. To study this more closely, two different porous YSZ scaffold microstructures were developed by using tape casting, followed by Ni infiltration using a polymeric precursor, known to form a continuous Ni phase, rather than electrically separated Ni particles. Ni infiltration into porous YSZ scaffolds with large grains (0.5 microm) and large pores (two types of pores: ˜0.5 microm and 5 microm) resulted in extensive Ni particle growth that resulted in poor stability and poor electrochemical performance (0.5 Ω cm2 per electrode at 800°C). Ni infiltration into a scaffold having finer grains and pores (˜200 nm each) resulted in anodes with a much lower polarization resistance of 0.11 Ω cm2 per electrode at 800°C, increasing by ˜5 % after 108 hours at this temperature.

  9. Industrial growth of yttria-stabilized cubic zirconia crystals by skull melting process

    Institute of Scientific and Technical Information of China (English)

    徐家跃; 雷秀云; 蒋新; 何庆波; 房永征; 张道标; 何雪梅

    2009-01-01

    We reported the development of a Ф100 cm growth apparatus for skull melting growth of yttria-stabilized cubic zirconia(YSZ) crystals and more than 1000 kg crystals have been grown in the furnace each time.The growth conditions were optimized and the structure of the as-grown crystals was characterized by X-ray diffraction.The transmittance of 15 mol.% yttria-stabilized cubic zirconia crystal was nearly 80% in the range of 400-1600 nm.The refractive indices were measured and fitted the Sellmeier equation whi...

  10. Electrode polarization at the Au, O2(g)/Fe implanted yttria-stabilized zirconia interface

    NARCIS (Netherlands)

    Hassel, van B.A.; Boukamp, B.A.; Burggraaf, A.J.

    1992-01-01

    Ion implantation has been applied to modify the surface properties of yttria-stabilized zirconia (YSZ). A three-electrode cell was used for measuring steady state current-overpotential curves and for determining the electrode impedance. An increase of the equilibrium exchange current density at the

  11. Characterization of Fe implanted yttria-stabilized zirconia by cyclic voltammetry

    NARCIS (Netherlands)

    Hassel, van B.A.; Burggraaf, A.J.

    1992-01-01

    The technique of cyclic voltammetry has been applied to study reduction and oxidation phenomena which are observed at low oxygen partial pressures during steady state current-overpotential measurements of the Au, O2(g)/Fe implanted yttria-stabilized zirconia interface. The redox potential (EO) of th

  12. Characterization of Fe implanted yttria-stabilized zirconia by cyclic voltammetry

    NARCIS (Netherlands)

    van Hassel, B.A.; van Hassel, B.A.; Burggraaf, Anthonie; Burggraaf, A.J.

    1992-01-01

    The technique of cyclic voltammetry has been applied to study reduction and oxidation phenomena which are observed at low oxygen partial pressures during steady state current-overpotential measurements of the Au, O2(g)/Fe implanted yttria-stabilized zirconia interface. The redox potential (EO) of

  13. Rapid densification of sol–gel derived yttria-stabilized zirconia thin films

    NARCIS (Netherlands)

    Veldhuis, S.A.; Brinks, P.; Elshof, ten J.E.

    2015-01-01

    A method based on X-ray reflectivity was used to study the densification behavior of 8 mol% yttria-stabilized zirconia for use in solid oxide fuel cells. Sol–gel derived thin electrolyte films were prepared via spin coating. Subsequent microwave-assisted rapid thermal annealing at 650–1000 °C result

  14. Effect of Bismuth Oxide on the Microstructure and Electrical Conductivity of Yttria Stabilized Zirconia

    Directory of Open Access Journals (Sweden)

    Liwei Liu

    2016-03-01

    Full Text Available Bismuth oxide (Bi2O3-doped yttria-stabilized zirconia (YSZ were prepared via the solid state reaction method. X-ray diffraction and electron diffraction spectroscopy results indicate that doping with 2 mol% Bi2O3 and adding 10 mol% yttria result in a stable zirconia cubic phase. Adding Bi2O3 as a dopant increases the density of zirconia to above 96%, while reducing its normal sintering temperature by approximately 250 °C. Moreover, electrical impedance analyses show that adding Bi2O3 enhances the conductivity of zirconia, improving its capability as a solid electrolyte for intermediate or even lower temperatures.

  15. Effect of Bismuth Oxide on the Microstructure and Electrical Conductivity of Yttria Stabilized Zirconia.

    Science.gov (United States)

    Liu, Liwei; Zhou, Zheng; Tian, He; Li, Jixue

    2016-03-14

    Bismuth oxide (Bi2O3)-doped yttria-stabilized zirconia (YSZ) were prepared via the solid state reaction method. X-ray diffraction and electron diffraction spectroscopy results indicate that doping with 2 mol% Bi2O3 and adding 10 mol% yttria result in a stable zirconia cubic phase. Adding Bi2O3 as a dopant increases the density of zirconia to above 96%, while reducing its normal sintering temperature by approximately 250°C. Moreover, electrical impedance analyses show that adding Bi2O3 enhances the conductivity of zirconia, improving its capability as a solid electrolyte for intermediate or even lower temperatures.

  16. Strontium zirconate as silicon and aluminum scavenger in yttria stabilized zirconia

    DEFF Research Database (Denmark)

    Andersen, Thomas; Hansen, Karin Vels; Chorkendorff, Ib

    2011-01-01

    Here we report on strontium zirconate as a getter for silicon dioxide and aluminum oxide in yttria stabilized zirconia (YSZ) single crystals for cleaning purposes. YSZ single crystals were covered with strontium zirconate powder and heat treated at 1450°C in water vapor. After treatment the YSZ s...... materials at elevated temperatures and prove a route to remove trace bulk impurities in YSZ....

  17. Nanostructured yttria stabilized zirconia coatings deposited by air plasma spraying

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hong; LI Fei; HE Bo; WANG Jun; SUN Bao-de

    2007-01-01

    Nanostructured yttria partially stabilized zirconia coatings were deposited by air plasma spraying with reconstituted nanosized powder. The microstructures and phase compositions of the powder and the as-sprayed nanostructured coatings were characterized by transmission electron microscopy(TEM), scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results demonstrate that the microstructure of as-sprayed nanostructured zirconia coating exhibits a unique tri-modal distribution including the initial nanostructure of the powder, equiaxed grains and columnar grains. Air plasma sprayed nanostructured zirconia coatings consist of only the nontransformable tetragonal phase, though the reconstituted nanostructured powder shows the presence of the monoclinic, the tetragonal and the cubic phases. The mean grain size of the coating is about 42 nm.

  18. Mechanical properties of yttria-stabilized zirconia ceramics

    Science.gov (United States)

    Shirooyeh A, Mahmood R.

    Superplasticity is a well-known characteristic of Y2O 3-stabilized tetragonal zirconia (3Y-TZP) ceramic composites at elevated temperatures. The present investigation was originated to evaluate the potential of producing zirconia ceramics suitable for achieving superplasticity. High purity 3 mol% Y2O3-stabilized tetragonal zirconia (3Y-TZP) ceramic composites containing 20 wt% alumina were successfully consolidated by application of Cold Isostatic Pressing (CIP) followed by a subsequent sintering process. Constant-stress tensile creep experiments at elevated temperatures were conducted in order to examine plastic deformation behavior of the material. In addition to mechanical testing data, the microstructure observations confirmed superplastic properties of the ceramic composite. It is also known that in order to attain High Strain Rate Superplasticity (HSRS) in zirconia ceramics, it is essential to retain a stable fine-grained microstructure at high temperatures. Experiments have confirmed that adding a second soft phase such as spinel can facilitate to reach high strain-rate superplasticity in zirconia ceramics by suppressing grain growth during sintering process and enhancing cation diffusion. In the present investigation, homogenous 3Y-TZP ceramic composite powders containing 30 vol% MgAl2O4 spinel were successfully prepared through both physical-based and chemical-based methods. An electric current-activated method known as Spark Plasma Sintering (SPS) was employed for powder consolidation process. This is a very rapid electric current-activated sintering technique having a heating rate of 300 K/min. The powder preparation and consolidation steps were carried out over a wide range of conditions to ensure a homogenous nanocomposite. The experiments showed that fully-dense zirconia ceramics with an average initial grain size of the order of ˜100 nm can be sintered at the relatively low processing temperature of 1373 K in 10 min. In order to study the

  19. Synthesis of Nanocrystalline Yttria Stabilized Zirconia for SOFC

    Directory of Open Access Journals (Sweden)

    Mridula Biswas

    2011-12-01

    Full Text Available Nanocrystalline zirconia powders stabilized with varying concentration of yttria (YSZ were synthesized following urea solution combustion route. Thermogravimetric analysis combined with differential scanning calorimetry was carried out for the intermediate gel for analyzing reaction kinetics. The final products were characterized by X‐ray diffractometry, transmission electron microscopy and specific surface area measurements. Sintering behavior of theses powders were studied. The powder quality is poor in respect of surface area and sintered density.

  20. Low-Temperature Superionic Conductivity in Strained Yttria-Stabilized Zirconia

    DEFF Research Database (Denmark)

    Sillassen, Michael; Eklund, Per; Pryds, Nini;

    2010-01-01

    Very high lateral ionic conductivities in epitaxial cubic yttria-stabilized zirconia (YSZ) synthesized on single-crystal SrTiO3 and MgO substrates by reactive direct current magnetron sputtering are reported. Superionic conductivities (i.e., ionic conductivities of the order 1 -1cm-1) are observed...... at 500 °C for 58-nm-thick films on MgO. The results indicate a superposition of two parallel contributions - one due to bulk conductivity and one attributable to conduction along the film-substrate interface. Interfacial effects dominate the conductivity at low temperatures (...

  1. Processing and Characterization of Yttria-Stabilized Zirconia Foams for High-Temperature Applications

    Directory of Open Access Journals (Sweden)

    Ana María Herrera

    2013-01-01

    Full Text Available In this work ceramic foams of 3 and 8 mol% yttria-stabilized zirconia (3YSZ and 8YSZ were manufactured by the replication method using polystyrene-polyurethane foams with pore sizes in the 7–10 ppi range. A second coating was carried out on presintered foams in order to thicken struts and hinder microstructural defects. The produced ceramic foams were structurally and thermomechanically characterized. Samples recoated with 3YSZ presented the highest relative densities (0.2±0.1 which contributed to a better mechanical and thermal behavior.

  2. Preparation of yttria-stabilized zirconia films for solid oxide fuel cells by electrophoretic deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Ishihara, Tatsumi; Sato, Keiji; Mizuhara, Yukako; Takita, Yusaku (Oita Univ. (Japan). Faculty of Engineering)

    1992-06-01

    The electrophoretic deposition (EPD) method was applied for the preparation of yttria-stabilized zirconia (YSZ) films for a solid oxide fuel cell (SOFC). Dense YSZ films with uniform thickness can be readily prepared by EPD method. When the planar SOFC was fabricated by using La[sub 0.6]Sr[sub 0.4]MnO[sub 3] as a cathode and electroless plating Pt as an anode, the open circuit voltage and the maximum power density attained were 1.03 V and 1.87 W cm[sup -2], respectively. (author).

  3. Structural and optical properties of electron beam evaporated yttria stabilized zirconia thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kirubaharan, A. Kamalan; Kuppusami, P., E-mail: pkigcar@gmail.com; Dharini, T.; Ramachandran, D. [Centre for Nanoscience and Nanotechnology, Sathyabama University, Chennai-600119 (India); Singh, Akash; Mohandas, E. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2015-06-24

    Yttria stabilized zirconia (10 mole % Y{sub 2}O{sub 3}) thin films were deposited on quartz substrates using electron beam physical vapor deposition at the substrate temperatures in the range 300 – 973 K. XRD analysis showed cubic crystalline phase of YSZ films with preferred orientation along (111). The surface roughness was found to increase with the increase of deposition temperatures. The optical band gap of ∼5.7 eV was calculated from transmittance curves. The variation in the optical properties is correlated with the changes in the microstructural features of the films prepared as a function of substrate temperature.

  4. Crystallographic Characteristics of Grain Boundaries in Dense Yttria-Stabilized Zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Lam Helmick; Shen J. Dillon; Kirk Gerdes; Randall Gemmen; Gregory S. Rohrer; Sridhar Seetharaman; Paul A. Salvador

    2010-04-01

    Grain-boundary plane, misorientation angle, grain size, and grain-boundary energy distributions were quantified using electron backscatter diffraction data for dense polycrystalline yttria-stabilized zirconia, to understand interfacial crystallography in solid oxide fuel cells. Tape-cast samples were sintered at 14501C for 4 h and annealed for at least 100 h between 8001C and 16501C. Distributions obtained from both three-dimensional (3D) reconstructions and stereological analyses of 2D sections demonstrated that the (100) boundary planes {(111)} have relative areas larger {smaller} than expected in a random distribution, and that the boundary plane distribution is inversely correlated to the boundary energy distribution.

  5. Atomic layer deposition of MgO films on yttria-stabilized zirconia microtubes

    Energy Technology Data Exchange (ETDEWEB)

    Part, Marko, E-mail: markopa@ut.ee [University of Tartu, Institute of Physics, Department of Materials Science, Riia 142, EE-51014 Tartu (Estonia); Tamm, Aile; Kozlova, Jekaterina; Mändar, Hugo; Tätte, Tanel [University of Tartu, Institute of Physics, Department of Materials Science, Riia 142, EE-51014 Tartu (Estonia); Kukli, Kaupo [University of Tartu, Institute of Physics, Department of Materials Science, Riia 142, EE-51014 Tartu (Estonia); University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014, Univ. Helsinki (Finland)

    2014-02-28

    Deposition of MgO thin film on nanocrystalline yttria-stabilized zirconia microtubes was investigated. The microtubes were prepared by self-formation from threads drawn directly from zirconium butoxide [Zr(OBu){sub 4}] precursor and heat treated at 800 °C. The tubes possessed 100% tetragonal phase, their typical outer diameter was 50 μm, inner diameter 30 μm and length 1 cm. MgO films were deposited from β-diketonate-type precursor 2,2,6,6-tetramethyl-heptanedionato-3,5-magnesium(II) at 220 °C by atomic layer deposition. Thickness of MgO film on microtubes was 15.8 nm and growth rate 0.105 Å/cycle. - Highlights: • MgO films were deposited on the surface of yttria-stabilized zirconia microtubes. • The studies are carried out on the basis of surface modification of microtubes. • Films were deposited from β-diketonate-type precursor Mg(thd){sub 2}. • The growth temperature of MgO film was 220 °C.

  6. Coupling between creep and redox behavior in nickel - yttria stabilized zirconia observed in-situ by monochromatic neutron imaging

    DEFF Research Database (Denmark)

    Makowska, Malgorzata Grazyna; Kuhn, Luise Theil; Frandsen, Henrik Lund

    2017-01-01

    Ni-YSZ (nickel - yttria stabilized zirconia) is a material widely used for electrodes and supports in solid oxide electrochemical cells. The mechanical and electrochemical performance of these layers, and thus the whole cell, depends on their microstructure. During the initial operation of a cell...

  7. On the bulk degradation of yttria-stabilized nanocrystalline zirconia dental implant abutments : an electron backscatter diffraction study

    NARCIS (Netherlands)

    Ocelik, V.; Schepke, U.; Rasoul, H. Haji; Cune, M. S.; De Hosson, J. Th. M.

    2017-01-01

    Degradation of yttria-stabilized zirconia dental implants abutments due to the tetragonal to monoclinic phase transformation was studied in detail by microstructural characterization using Electron Back Scatter Diffraction (EBSD). The amount and distribution of the monoclinic phase, the grain-size d

  8. Electrode Properties of Sr-Doped LaMnO3 on Yttria-Stabilized Zirconia II: Electrode kinetics

    NARCIS (Netherlands)

    Heuveln, van F.H.; Bouwmeester, H.J.M.

    1997-01-01

    A series of six cathodes Sr0.15La0.85MnO3 (SLM) on yttria-stabilized zirconia with different morphology of the electrode/electrolyte interface were characterized by ac impedance and dc polarization measurements. It is found that the electrode kinetics at elevated temperature (945°C) are governed by

  9. Effects of dopant concentration and impurities on the conductivity of magnetron-sputtered nanocrystalline yttria-stabilized zirconia

    DEFF Research Database (Denmark)

    Sillassen, M.; Eklund, P.; Pryds, Nini;

    2010-01-01

    Cubic yttria-stabilized zirconia (YSZ) films with yttria concentrations of 8.7, 9.9, and 11 mol% have been deposited by reactive pulsed DC magnetron from Zr–Y alloy targets. The overall microstructure and texture in the films showed no dependence on the yttria concentration. Films deposited at fl...

  10. Low Friction in CuO-Doped Yttria-Stabilized Tetragonal Zirconia Ceramics: A Complementary Macro- and Nanotribology Study

    NARCIS (Netherlands)

    Tocha, Ewa; Pasaribu, Henry R.; Schipper, Dik J.; Schönherr, Holger; Vancso, G. Julius

    2008-01-01

    The tribological behavior of CuO-doped yttria-stabilized tetragonal zirconia (3Y-TZP) ceramics in the absence of additional lubricants was characterized by macroscale pin-on-disk measurements and nanoscale atomic force microscopy (AFM) for a broad range of velocities. The previously observed low she

  11. Initial Bacterial Adhesion on Different Yttria-Stabilized Tetragonal Zirconia Implant Surfaces in Vitro

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    Lamprini Karygianni

    2013-12-01

    Full Text Available Bacterial adhesion to implant biomaterials constitutes a virulence factor leading to biofilm formation, infection and treatment failure. The aim of this study was to examine the initial bacterial adhesion on different implant materials in vitro. Four implant biomaterials were incubated with Enterococcus faecalis, Staphylococcus aureus and Candida albicans for 2 h: 3 mol % yttria-stabilized tetragonal zirconia polycrystal surface (B1a, B1a with zirconium oxide (ZrO2 coating (B2a, B1a with zirconia-based composite coating (B1b and B1a with zirconia-based composite and ZrO2 coatings (B2b. Bovine enamel slabs (BES served as control. The adherent microorganisms were quantified and visualized using scanning electron microscopy (SEM; DAPI and live/dead staining. The lowest bacterial count of E. faecalis was detected on BES and the highest on B1a. The fewest vital C. albicans strains (42.22% were detected on B2a surfaces, while most E. faecalis and S. aureus strains (approximately 80% were vital overall. Compared to BES; coated and uncoated zirconia substrata exhibited no anti-adhesive properties. Further improvement of the material surface characteristics is essential.

  12. Initial Bacterial Adhesion on Different Yttria-Stabilized Tetragonal Zirconia Implant Surfaces in Vitro

    Science.gov (United States)

    Karygianni, Lamprini; Jähnig, Andrea; Schienle, Stefanie; Bernsmann, Falk; Adolfsson, Erik; Kohal, Ralf J.; Chevalier, Jérôme; Hellwig, Elmar; Al-Ahmad, Ali

    2013-01-01

    Bacterial adhesion to implant biomaterials constitutes a virulence factor leading to biofilm formation, infection and treatment failure. The aim of this study was to examine the initial bacterial adhesion on different implant materials in vitro. Four implant biomaterials were incubated with Enterococcus faecalis, Staphylococcus aureus and Candida albicans for 2 h: 3 mol % yttria-stabilized tetragonal zirconia polycrystal surface (B1a), B1a with zirconium oxide (ZrO2) coating (B2a), B1a with zirconia-based composite coating (B1b) and B1a with zirconia-based composite and ZrO2 coatings (B2b). Bovine enamel slabs (BES) served as control. The adherent microorganisms were quantified and visualized using scanning electron microscopy (SEM); DAPI and live/dead staining. The lowest bacterial count of E. faecalis was detected on BES and the highest on B1a. The fewest vital C. albicans strains (42.22%) were detected on B2a surfaces, while most E. faecalis and S. aureus strains (approximately 80%) were vital overall. Compared to BES; coated and uncoated zirconia substrata exhibited no anti-adhesive properties. Further improvement of the material surface characteristics is essential. PMID:28788415

  13. Ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline yttria-stabilized zirconia

    DEFF Research Database (Denmark)

    Sillassen, M.; Eklund, P.; Sridharan, M.;

    2009-01-01

    Thermally stable, stoichiometric, cubic yttria-stabilized zirconia (YSZ) thin-film electrolytes have been synthesized by reactive pulsed dc magnetron sputtering from a Zr–Y (80/20 at. %) alloy target. Films deposited at floating potential had a texture. Single-line profile analysis of the 111 x.......5% at bias voltages of −175 and −200 V with additional incorporation of argon. The films were thermally stable; very limited grain coarsening was observed up to an annealing temperature of 800 °C. Temperature-dependent impedance spectroscopy analysis of the YSZ films with Ag electrodes showed that the in......-plane ionic conductivity was within one order of magnitude higher in films deposited with substrate bias corresponding to a decrease in grain size compared to films deposited at floating potential. This suggests that there is a significant contribution to the ionic conductivity from grain boundaries...

  14. Electrochemical removal of segregated silicon dioxide impurities from yttria stabilized zirconia surfaces at elevated temperatures

    DEFF Research Database (Denmark)

    Andersen, Thomas; Hansen, Karin Vels; Mogensen, Mogens Bjerg;

    2011-01-01

    Here we report on the electrochemical removal of segregated silicon dioxide impurities from Yttria Stabilized Zirconia (YSZ) surfaces at elevated temperatures studied under Ultra High Vacuum (UHV) conditions. YSZ single crystals were heated in vacuum by an applied 18kHz a.c. voltage using the ionic...... and XPS analysis. Silicon enrichment of the surface was only observed at oxygen and water vapor partial pressures above 25mbar and 10mbar, respectively. No silicon was observed on crystals annealed in vacuum and at oxygen and water vapor partial pressures below 10mbar. The YSZ seems to get partially...... electrochemically reduced by the a.c. voltage when no oxidation substances are present. The absence of silicon on the surfaces annealed in vacuum or at low oxygen or water vapor partial pressures was attributed to electrochemical reduction of silicon dioxide to volatile silicon monoxide on the YSZ surface...

  15. Sintering of yttria-stabilized zirconia nanopowders studied by positron annihilation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cizek, J.; Melikhova, O.; Kuriplach, J.; Prochazka, I. [Charles University in Prague, Faculty of Mathematics and Physics, Department of Low Temperature Physics, Praha (Czech Republic); Konstantinova, T.E.; Danilenko, I.A. [Galkin Donetsk Institute for Physics and Engineering, National Academy of Science of Ukraine, Donetsk (Ukraine)

    2009-11-15

    A positron annihilation study of the tetragonal yttria-stabilized zirconia (YSZ) nanopowder compacted under a high pressure and subjected to a sintering at temperatures ranging from 1000 to 1350 C were investigated. The conventional positron lifetime and coincidence Doppler broadening measurements were performed. In the compacted nanopowder, positrons were found to annihilate mainly as trapped at vacancy-like defects (most likely the Zr vacancies) situated in the negative space-charge layers along grain boundaries (GB's) or at larger defects associated with GB intersections (triple points). Moreover, pores of a few-nanometer size were detected via positronium pick-off annihilation in the YSZ nanopowders. These pores, however, disappeared after sintering at 1000 C and a significant grain growth takes place above this temperature. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Mechanical Behavior of Yttria-Stabilized Zirconia Aqueous Cast Tapes and Laminates

    Directory of Open Access Journals (Sweden)

    V. Moreno

    2014-01-01

    Full Text Available Aqueous tape casting was used to produce yttria-stabilized zirconia films for electrolyte-supported solid oxide fuel cell (SOFC. Tape casting slurries were prepared varying the binder content between 20 and 25 wt%. A commercial acrylic emulsion served as binder. Rheological measurements of the two slurries were performed. Both slurries showed a shear-thinning behavior. Tapes with 25 wt% binder exhibited adequate flexibility and a smooth and homogeneous surface, free of cracks and other defects. Suitable conditions of lamination were found and a theoretical density of 54% in the laminates was achieved. Laminated tapes showed higher tensile strength compared to single sheets. Tape orientation has a significant influence on the mechanical properties. Tensile strength, elongation to strain, and Young’s modulus measured in samples produced in the direction of casting showed higher property values.

  17. Tetragonal BiFeO{sub 3} on yttria-stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Heng-Jui [Department of Materials Science Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan (China); Du, Yu-Hao [Department of Materials Science Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Gao, Peng; Ikuhara, Yuichi [Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656 (Japan); Huang, Yen-Chin; Chen, Yi-Chun [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Chen, Hsiao-Wen; Liu, Hsiang-Lin [Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan (China); He, Qing [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Chu, Ying-Hao, E-mail: yhc@nctu.edu.tw [Department of Materials Science Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China)

    2015-11-01

    High structural susceptibility of multiferroic BiFeO{sub 3} (BFO) makes it a potential replacement of current Pb-based piezoelectrics. In this study, a tetragonal phase is identified based on a combination of x-ray diffraction, scanning transmission electronic microscopy, x-ray absorption spectroscopy, and Raman spectroscopy when BFO is grown on yttria-stabilized zirconia (YSZ) substrates. To distinguish the discrepancy between this tetragonal phase and common cases of monoclinic BFO, piezoelectric force microscopy images and optical property are also performed. It shows a lower electrostatic energy of ferroelectric domains and a large reduction of band gap for BFO grown on YSZ substrate comparing to the well-known one grown on LaAlO{sub 3} substrate. Our findings in this work can provide more insights to understand the structural diversity of multiferroic BFO system for further applications.

  18. Tetragonal BiFeO3 on yttria-stabilized zirconia

    Directory of Open Access Journals (Sweden)

    Heng-Jui Liu

    2015-11-01

    Full Text Available High structural susceptibility of multiferroic BiFeO3 (BFO makes it a potential replacement of current Pb-based piezoelectrics. In this study, a tetragonal phase is identified based on a combination of x-ray diffraction, scanning transmission electronic microscopy, x-ray absorption spectroscopy, and Raman spectroscopy when BFO is grown on yttria-stabilized zirconia (YSZ substrates. To distinguish the discrepancy between this tetragonal phase and common cases of monoclinic BFO, piezoelectric force microscopy images and optical property are also performed. It shows a lower electrostatic energy of ferroelectric domains and a large reduction of band gap for BFO grown on YSZ substrate comparing to the well-known one grown on LaAlO3 substrate. Our findings in this work can provide more insights to understand the structural diversity of multiferroic BFO system for further applications.

  19. Machine-able Yttria Stabilized Zirconia Composites for Thermal Insulation in Nuclear Reactors

    Science.gov (United States)

    Lo, J.; Zhang, R.; Santos, R.

    2016-02-01

    Ceramics are a promising insulating material for high temperature environment. To qualify for in-core use in nuclear reactors, there are many other materials requirements to be met, such as neutron irradiation resistance, corrosion resistance, low thermal conductivity, high coefficient of thermal expansion, high strength, high fracture toughness, ease of fabricability, etc. And among the promising ceramics meeting most of the requirements, with the exception of fabricability, is yttria-stabilized zirconia (YSZ). Like all ceramics, YSZ is hard, brittle and difficult to machine. At CanmetMATERIALS, YSZ-based composites for in-core insulation that are machine-able and capable of being formed into complex shapes have been developed. In this paper, the focus is geared towards the fabrication and property evaluation of such composites. In addition, the machinability aspect of the YSZ composites was addressed with a demonstration of a machined component.

  20. Fabrication of Yttria stabilized zirconia thin films on poroussubstrates for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Leming, Andres [Univ. of California, Berkeley, CA (United States)

    2003-06-16

    A process for the deposition of yttria stabilized zirconia (YSZ) films, on porous substrates, has been developed. These films have possible applications as electrolyte membranes in fuel cells. The films were deposited from colloidal suspensions through the vacuum infiltration technique. Films were deposited on both fully sintered and partially sintered substrates. A critical cracking thickness for the films was identified and strategies are presented to overcome this barrier. Green film density was also examined, and a method for improving green density by changing suspension pH and surfactant was developed. A dependence of film density on film thickness was observed, and materials interactions are suggested as a possible cause. Non-shorted YSZ films were obtained on co-fired substrates, and a cathode supported solid oxide fuel cell was constructed and characterized.

  1. Grain Boundary Resistivity of Yttria-Stabilized Zirconia at 1400°C

    Directory of Open Access Journals (Sweden)

    J. Wang

    2013-01-01

    Full Text Available The grain size dependence of the bulk resistivity of 3 mol% yttria-stabilized zirconia at 1400°C was determined from the effect of a dc electric field Ea=18.1 V/cm on grain growth and the corresponding electric current during isothermal annealing tests. Employing the brick layer model, the present annealing test results were in accordance with extrapolations of the values obtained at lower temperature employing impedance spectroscopy and 4-point-probe dc. The combined values give that the magnitude of the grain boundary resistivity ρb=133 ohm-cm. The electric field across the grain boundary width was 28–43 times the applied field for the grain size and current ranges in the present annealing test.

  2. Surface modification of yttria stabilized zirconia via polydopamine inspired coating for hydroxyapatite biomineralization

    Energy Technology Data Exchange (ETDEWEB)

    Zain, Norhidayu Muhamad [Medical Devices and Technology Group, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Hussain, Rafaqat [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Kadir, Mohammed Rafiq Abdul, E-mail: rafiq@biomedical.utm.my [Medical Devices and Technology Group, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia)

    2014-12-15

    Highlights: • Synthesis of functionalized yttria stabilized zirconia using polydopamine. • Improved hydrophilicity of the grafted samples with low contact angle of 44.0 ± 2.3. • Apatite layer with Ca/P ratio of 1.78 formed on the surface of the grafted samples. • Atomic percentage of Ca 2p increased by 2-fold at coating temperature of 37 °C. - Abstract: Yttria stabilized zirconia (YSZ) has been widely used as biomedical implant due to its high strength and enhanced toughening characteristics. However, YSZ is a bioinert material which constrains the formation of chemical bonds with bone tissue following implantation. Inspired by the property of mussels, the surface of YSZ ceramics was functionalized by quinone-rich polydopamine to facilitate the biomineralization of hydroxyapatite. YSZ discs were first immersed in 2 mg/mL of stirred or unstirred dopamine solution at either 25 or 37 °C. The samples were then incubated in 1.5 simulated body fluid (SBF) for 7d. The effect of coating temperature for stirred and unstirred dopamine solutions during substrate grafting was investigated on the basis of chemical compositions, wettability and biomineralization of hydroxyapatite on the YSZ functionalized surface. The results revealed that the YSZ substrate grafted at 37 °C in stirred solution of dopamine possessed significantly improved hydrophilicity (water contact angle of 44.0 ± 2.3) and apatite-mineralization ability (apatite ratio of 1.78). In summary, the coating temperature and stirring condition during grafting procedure affected the chemical compositions of the films and thus influenced the formation of apatite layer on the substrate during the biomineralization process.

  3. Normal spectral emittance of Inconel 718 aeronautical alloy coated with yttria stabilized zirconia films

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Fernandez, L. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Industria de Turbo Propulsores, S.A., Planta de Zamudio, Edificio 300, 48170 Zamudio, Bizkaia (Spain); Campo, L. del [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Perez-Saez, R.B., E-mail: raul.perez@ehu.es [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain); Tello, M.J. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa, Bizkaia (Spain)

    2012-02-05

    Highlights: Black-Right-Pointing-Pointer Emittance of Inconel 718 coated with plasma sprayed yttria stabilized zirconia. Black-Right-Pointing-Pointer The coating is opaque for {lambda} > 9 {mu}m and semi-transparent for {lambda} < 9 {mu}m. Black-Right-Pointing-Pointer In the semi-transparent region the emittance decreases with coating thickness. Black-Right-Pointing-Pointer 300 {mu}m thick coatings are still semi-transparent. Black-Right-Pointing-Pointer In the opaque region the surface roughness determines the emittance level. - Abstract: Knowledge of the radiative behaviour of the yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs) is needed to perform radiative heat transfer calculations in industrial applications. In this paper, normal spectral emittance experimental data of atmospheric plasma sprayed (PS) YSZ films layered on Inconel 718 substrates are shown. The spectral emittance was measured between 2.5 and 22 {mu}m on samples with film thicknesses ranging from 20 to 280 {mu}m. The samples were heated in a controlled environment, and the emittance was measured for several temperatures between 330 and 730 Degree-Sign C. The dependence of the spectral emittance with film thickness, surface roughness and temperature has been studied and compared with the available results for YSZ TBCs obtained by electron-beam physical vapour deposition. The PS-TBC samples show a Christiansen point at {lambda} = 12.8 {mu}m. The films are semi-transparent for {lambda} < 9 {mu}m, and opaque for {lambda} > 9 {mu}m. In the semi-transparent region, the contribution of the radiation emitted by the Inconel 718 substrate to the global emittance of the samples is analysed. In addition, the influence of the roughness in the emittance values in the opaque spectral region is discussed. Finally, the total normal emittance is obtained as a function of the TBC thickness.

  4. Positron annihilation study of yttria-stabilized zirconia nanopowders containing Cr{sub 2}O{sub 3} additive

    Energy Technology Data Exchange (ETDEWEB)

    Prochazka, I; Cizek, J; Melikhova, O; Kuriplach, J [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00, Praha 8 (Czech Republic); Konstantinova, T E; Danilenko, I A, E-mail: ivan.prochazka@mff.cuni.cz [Galkin Donetsk Institute for Physics and Engineering, National Academy of Sciences of Ukraine, Luxemburg Street 72, 83114 Donetsk (Ukraine)

    2011-01-10

    Yttria-stabilized zirconia compacted nanopowders, doped with trivalent chromium oxide, were studied by means of high-resolution positron lifetime and coincidence Doppler broadening techniques. The observed data suggest that positrons annihilate mainly in vacancylike defects at grain boundaries or in larger open volumes most likely located at triple points. The results also show that an addition of Cr{sub 2}O{sub 3} leads to a decrease in grain size.

  5. Surface modification of yttria stabilized zirconia via polydopamine inspired coating for hydroxyapatite biomineralization

    Science.gov (United States)

    Zain, Norhidayu Muhamad; Hussain, Rafaqat; Kadir, Mohammed Rafiq Abdul

    2014-12-01

    Yttria stabilized zirconia (YSZ) has been widely used as biomedical implant due to its high strength and enhanced toughening characteristics. However, YSZ is a bioinert material which constrains the formation of chemical bonds with bone tissue following implantation. Inspired by the property of mussels, the surface of YSZ ceramics was functionalized by quinone-rich polydopamine to facilitate the biomineralization of hydroxyapatite. YSZ discs were first immersed in 2 mg/mL of stirred or unstirred dopamine solution at either 25 or 37 °C. The samples were then incubated in 1.5 simulated body fluid (SBF) for 7d. The effect of coating temperature for stirred and unstirred dopamine solutions during substrate grafting was investigated on the basis of chemical compositions, wettability and biomineralization of hydroxyapatite on the YSZ functionalized surface. The results revealed that the YSZ substrate grafted at 37 °C in stirred solution of dopamine possessed significantly improved hydrophilicity (water contact angle of 44.0 ± 2.3) and apatite-mineralization ability (apatite ratio of 1.78). In summary, the coating temperature and stirring condition during grafting procedure affected the chemical compositions of the films and thus influenced the formation of apatite layer on the substrate during the biomineralization process.

  6. Micro-tubular solid oxide fuel cell based on a porous yttria-stabilized zirconia support.

    Science.gov (United States)

    Panthi, Dhruba; Tsutsumi, Atsushi

    2014-08-29

    Solid oxide fuel cells (SOFCs) are promising electrochemical energy conversion devices owing to their high power generation efficiency and environmentally benign operation. Micro-tubular SOFCs, which have diameters ranging from a few millimeters to the sub-millimeter scale, offer several advantages over competing SOFCs such as high volumetric power density, good endurance against thermal cycling, and flexible sealing between fuel and oxidant streams. Herein, we successfully realized a novel micro-tubular SOFC design based on a porous yttria-stabilized zirconia (YSZ) support using multi-step dip coating and co-sintering methods. The micro-tubular SOFC consisted of Ni-YSZ, YSZ, and strontium-doped lanthanum manganite (LSM)-YSZ as the anode, electrolyte, and cathode, respectively. In addition, to facilitate current collection from the anode and cathode, Ni and LSM were applied as an anode current collector and cathode current collector, respectively. Micro-crystalline cellulose was selected as a pore former to achieve better shrinkage behavior of the YSZ support so that the electrolyte layer could be densified at a co-sintering temperature of 1300 °C. The developed micro-tubular design showed a promising electrochemical performance with maximum power densities of 525, 442, and 354 mW cm(-2) at 850, 800, and 750 °C, respectively.

  7. Rapid densification of sol–gel derived yttria-stabilized zirconia thin films

    Energy Technology Data Exchange (ETDEWEB)

    Veldhuis, Sjoerd A.; Brinks, Peter; Elshof, Johan E. ten, E-mail: j.e.tenelshof@utwente.nl

    2015-08-31

    A method based on X-ray reflectivity was used to study the densification behavior of 8 mol% yttria-stabilized zirconia for use in solid oxide fuel cells. Sol–gel derived thin electrolyte films were prepared via spin coating. Subsequent microwave-assisted rapid thermal annealing at 650–1000 °C resulted in crack-free 70 nm thin films. A maximum density of approximately 95% was achieved within 5 min at 1000 °C. X-ray photoelectron spectroscopy depth analysis on the thin films showed that the shorter annealing times, as opposed to conventional heating, resulted in lower Si concentrations at the top surface and at the substrate interface. - Highlights: • Parameter-free method based on XRR to study densification 8YSZ • Microwave-assisted thermal annealing resulted in crack-free 70 nm thin films. • Density up to 95% was achieved within 5 min at 1000 °C. • XPS analysis showed that short annealing times resulted in lower Si concentrations.

  8. Synthesis, microstructural, optical and mechanical properties of yttria stabilized zirconia thin films

    Energy Technology Data Exchange (ETDEWEB)

    Amezaga-Madrid, P.; Hurtado-Macias, A.; Antunez-Flores, W.; Estrada-Ortiz, F.; Piza-Ruiz, P. [Centro de Investigacion en Materiales Avanzados S. C., and Laboratorio Nacional de Nanotecnologia. Miguel de Cervantes 120, Chihuahua, Chih., C.P. 31109 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados S. C., and Laboratorio Nacional de Nanotecnologia. Miguel de Cervantes 120, Chihuahua, Chih., C.P. 31109 (Mexico)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Thin films of YSZ obtained by AACVD have high quality. Black-Right-Pointing-Pointer They are uniform, very transparent, and have high hardness. Black-Right-Pointing-Pointer Optical characterization were performed in detail, optical constants and band gap energy were determined as a function of dopant content. - Abstract: Thin films of yttria-stabilized zirconia (YSZ) exhibit exceptional properties, such as high thermal, chemical and mechanical stability. Here, we report the synthesis of YSZ thin films by aerosol assisted chemical vapour deposition onto borosilicate glass and fused silica substrates. Optimum deposition temperature was 673 {+-} 5 K. In addition, different Y content was tried to analyse its influence in the microstructure and properties of the films. The films were uniform, transparent and non-light scattering. Surface morphology and cross sectional microstructure were studied by field emission scanning electron microscopy. The microstructure of the films was characterized by grazing incidence X-ray diffraction. Crystallite size and lattice parameter were obtained. Optical properties were analysed from reflectance and transmittance spectra; from these measurements, optical constants and band gap were obtained. Quantum confinement effect, due to the small grain size of the films, was evident in the high band gap energy obtained. Nanoindentation tests were realized at room temperature employing the continuous stiffness measurement method, to determine the hardness and elastic modulus as a function of Y content.

  9. Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia

    Science.gov (United States)

    Good, Brian

    2011-01-01

    Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

  10. Pulsewidth dependence of laser-induced periodic surface structure formed on yttria-stabilized zirconia polycrystal

    Science.gov (United States)

    Kakehata, Masayuki; Yashiro, Hidehiko; Oyane, Ayako; Ito, Atsuo; Torizuka, Kenji

    2016-03-01

    Three-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) is a fine engineering ceramic that offers high fracture resistance and flexural strength. Thus, it is often applied in mechanical components and medical implants. The surface roughness can be controlled to improve the device characters in some applications. Ultrashort pulse lasers can form laser-induced periodic surface structures (LIPSS) on 3Y-TZP, which have never been investigated in detail. Therefore, this paper reports the formation and characteristics of LIPSS formed on 3Y-TZP, focusing on the pulsewidth dependence. The LIPSS was formed by a Ti:sapphire chirped-pulse amplification system, which generates 810 nmcentered 80-fs pulses at a 570 Hz repetition rate. The measured ablation threshold peak fluence was ~1.5 J/cm2 and the LIPSS was formed at the peak fluence of 2.7-7.7 J/cm2. For linearly polarized pulses, the lines of the LIPSS were oriented parallel to the polarization direction, and their period was comparable to or larger than the center wavelength of the laser. These characteristics differ from the reported characteristics of LIPSS on metals and dielectrics. The pulsewidth dependence of the ablation and LIPSS was investigated for different pulsewidths and signs of chirp. Under the investigated fluence condition, the LIPSS period increased with increasing pulsewidth for both signs of chirp. Similar pulsewidth dependencies were observed for circularly polarized pulses.

  11. RF plasma enhanced MOCVD of yttria stabilized zirconia thin films using octanedionate precursors and their characterization

    Energy Technology Data Exchange (ETDEWEB)

    Chopade, S.S. [Laser and Plasma Technology Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Nayak, C.; Bhattacharyya, D.; Jha, S.N.; Tokas, R.B.; Sahoo, N.K. [Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Deo, M.N. [High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Biswas, A. [Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Rai, Sanjay [Indus Synchrotron Utilization Division, RRCAT, Indore 452013 (India); Thulasi Raman, K.H.; Rao, G.M. [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012 (India); Kumar, Niranjan [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Patil, D.S., E-mail: dspatil@iitb.ac.in [Laser and Plasma Technology Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India)

    2015-11-15

    Highlights: • YSZ films are deposited by RF plasma MOCVD using Zr(tod){sub 4} and Y(tod){sub 3} precursors. • Films are deposited under the influence of RF self-bias on the substrates. • Films are characterized by different techniques. • Films properties are dependent on yttria content and film structure. - Abstract: Yttria stabilized zirconia thin films have been deposited by RF plasma enhanced MOCVD technique on silicon substrates at substrate temperature of 400 °C. Plasma of precursor vapors of (2,7,7-trimethyl-3,5-octanedionate) yttrium (known as Y(tod){sub 3}), (2,7,7-trimethyl-3,5-octanedionate) zirconium (known as Zr(tod){sub 4}), oxygen and argon gases is used for deposition. To the best of our knowledge, plasma assisted MOCVD of YSZ films using octanediaonate precursors have not been reported in the literature so far. The deposited films have been characterized by GIXRD, FTIR, XPS, FESEM, AFM, XANES, EXAFS, EDAX and spectroscopic ellipsometry. Thickness of the films has been measured by stylus profilometer while tribological property measurement has been done to study mechanical behavior of the coatings. Characterization by different techniques indicates that properties of the films are dependent on the yttria content as well as on the structure of the films.

  12. Electrochemical behaviour of ceramic yttria stabilized zirconia on carbon steel synthesized via sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Crespo, M.A. Dominguez, E-mail: mdominguezc@ipn.m [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Murillo, A. Garcia; Torres-Huerta, A.M. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Yanez-Zamora, C. [Estudiante del postgrado en Tecnologia Avanzada del CICATA-IPN, Unidad Altamira, km 14.5, Carr. Tampico-Puerto Industrial. C.P. 89600, Altamira, Tamaulipas (Mexico); Carrillo-Romo, F. de J [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira (CICATA-IPN) km 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico)

    2009-08-26

    Chromate conversion coatings have been widely applied for the corrosion of different metallic substrates. However, the waste containing Cr{sup 6+} has many limitations due to the environmental consideration and health hazards. An interesting alternative seems to be the deposition on metallic surface of thin layers of yttria or zirconia or both by the sol-gel process. In this study, Ytttria and Yttria stabilized zirconia (YSZ, 8% Y{sub 2}O{sub 3}) thin films were used for coating commercial carbon steel substrates by sol-gel method and the dip-coating process. The evolution of organic compounds up to crystallization process as a function of heat treatments was study by FT-IR spectroscopy. The structure and morphology of the coatings were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The anticorrosion performance of the coatings has been evaluated by using electrochemical techniques in an aggressive media (3.5 wt.% NaCl). The corrosion behaviour of sol-gel method was compared with traditional chromate conversion coatings. Differences in the electrochemical behaviour of YSZ coatings are related to the development of microcracks during the sintering process and to the presence of organic compounds during growth film. Electrochemical results showed that sol-gel YSZ and Y{sub 2}O{sub 3} coatings can act as protective barriers against wet corrosion; however yttria films displayed low adhesion to substrate. The corrosion parameters provide an explanation of the role of each film and show a considerable increase in the corrosion resistance for coated samples in comparison to the bare steel samples.

  13. Yttria-stabilized zirconia as membrane material for electrolytic deoxidation of CaO-CaCl{sub 2} melts

    Energy Technology Data Exchange (ETDEWEB)

    Martin, A.; Poignet, J. C.; Fouletier, J. [Univ Grenoble, LEPMI, CNRS, INPG, UJF, F-38402 St Martin Dheres (France); Allibert, M. [LPSC, F-38026 Grenoble 1 (France); Lambertin, D. [SPDE, CEA Marcoule, F-30207 Bagnols Sur Ceze (France); Bourges, G. [SRPU, CEA Valduc, F-21120 Is Sur Tille (France)

    2010-07-01

    This article is devoted to the study of the stability of an yttria-stabilized zirconia membrane used in the electrolysis of molten CaCl{sub 2}-CaO mixtures at 850 degrees C. Intentiostatic and potentiostatic electrolysis were carried for periods ranging from 10 to 20 h. Post-mortem composition profiles across the zirconia membrane were determined using Raman spectroscopy and microprobe analysis. The membrane degradation was analyzed in terms of synergetic parameters, i. e., chemical, electrochemical, and thermomechanical effects. (authors)

  14. Electrode Properties of Sr-Doped LaMnO3 on Yttria-Stabilized Zirconia II: Electrode kinetics

    OpenAIRE

    Heuveln, van, J.J.; Bouwmeester, H. J. M.

    1997-01-01

    A series of six cathodes Sr0.15La0.85MnO3 (SLM) on yttria-stabilized zirconia with different morphology of the electrode/electrolyte interface were characterized by ac impedance and dc polarization measurements. It is found that the electrode kinetics at elevated temperature (945°C) are governed by two serial processes. An activation process can be identified to occur at high cathodic overpotential, whereas a transport process competes with charge-transfer at comparatively low overpotential. ...

  15. Aging performances for resisting low-temperature of three dental yttria-stabilized zirconia ceramic core materials

    Institute of Scientific and Technical Information of China (English)

    XIAO Rui; CHU Bing-feng; ZHANG Lan; CAO Jun-kai

    2012-01-01

    Background The low-temperature resistance aging performance of Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is the key effective factor that influences the long-term success rate of prosthesis.The objective of this study was to test and compare the aging performances for resisting low temperature of Lava Frame,Cercon Smart,and Upcera Yttria-stabilized zirconia core materials,via analyzing the micro and the crystal phases of the materials,and measure the three-point bending strength and the fracture toughness.Methods The three zirconia green bodies were prepared as 60 test samples for three-point bending strength and as 60 test samples for fracture toughness.The test samples for three-point bending strength and fracture toughness were assigned to five groups and were treated respectively for 0,5,10,15,and 20 hours to observe the micro and the crystal phases of the test samples.Then the three-point bending strength and fracture toughness were tested by X-ray diffraction (XRD).Results The m phase content of Lava Frame was raised from 7.70% to 13.01%; the m phase content of Cercon Smart was raised from 4.95% to 8.53%; and Lava Frame is raised from 10.84% to 35.18%.The three-point bending strengths of the three zirconia core materials were higher than 1100 MPa and the fracture toughness was higher than 3 MPa·m1/2.The three-point bending strength and the fracture toughness of Upcra zirconia decreased the most,followed by Lava Frame,and then by Cercon Smart.Conclusion The aging resistance sequences of the three zirconia core materials are,from strong to weak,Cercon Smart,Lava Frame,and Upcera.

  16. Study on the influences of reduction temperature on nickel-yttria-stabilized zirconia solid oxide fuel cell anode using nickel oxide-film electrode

    Science.gov (United States)

    Jiao, Zhenjun; Ueno, Ai; Suzuki, Yuji; Shikazono, Naoki

    2016-10-01

    In this study, the reduction processes of nickel oxide at different temperatures were investigated using nickel-film anode to study the influences of reduction temperature on the initial performances and stability of nickel-yttria-stabilized zirconia anode. Compared to conventional nickel-yttria-stabilized zirconia composite cermet anode, nickel-film anode has the advantage of direct observation at nickel-yttria-stabilized zirconia interface. The microstructural changes were characterized by scanning electron microscopy. The reduction process of nickel oxide is considered to be determined by the competition between the mechanisms of volume reduction in nickel oxide-nickel reaction and nickel sintering. Electrochemical impedance spectroscopy was applied to analyze the time variation of the nickel-film anode electrochemical characteristics. The anode performances and microstructural changes before and after 100 hours discharging and open circuit operations were analyzed. The degradation of nickel-film anode is considered to be determined by the co-effect between the nickel sintering and the change of nickel-yttria-stabilized zirconia interface bonding condition.

  17. Deterioration of yttria-stabilized zirconia by boron carbide alone or mixed with metallic or oxidized Fe, Cr, Zr mixtures

    Energy Technology Data Exchange (ETDEWEB)

    De Bremaecker, A., E-mail: adbremae@sckcen.be [Belgian Nuclear Research Center (SCK-CEN), NMS, Mol (Belgium); Ayrault, L., E-mail: laurent.ayrault@cea.fr [Institut de Radio-Protection et Sûreté Nucléaire/DPAM/SEMIC, Bât 702, CEN de Cadarache BP3, F-13115 Saint-Paul-lez-Durance (France); Clément, B. [Institut de Radio-Protection et Sûreté Nucléaire/DPAM/SEMIC, Bât 702, CEN de Cadarache BP3, F-13115 Saint-Paul-lez-Durance (France)

    2014-08-01

    In the frame of severe accident conditions (PHEBUS FPT3 test), different experiments were carried out on the interactions of 20% yttria-stabilized zirconia (YSZ) and 20% ceria-stab zirconia with boron carbide or its oxidation products (B{sub 2}O{sub 3}): either tests under steam between 1230° and 1700 °C with B{sub 4}C alone or B{sub 4}C mixed with metals, either tests under Ar with boron oxide present in a mixture of iron and chromium oxides. In all cases an interaction was observed with formation of intergranular yttrium borate. At 1700 °C boron oxide is able to “pump out” the Y stabiliser from the YSZ grains but also some trace elements (Ca and Al) and to form a eutectic containing YBO{sub 3} and yttrium calcium oxy-borate (YCOB). At the same time a substantial swelling (“bloating”) of the zirconia happens, qualitatively similar to the foaming of irradiated fuel in contact with a Zr-melt. In all samples the lowering of the Y (or Ce)-content in the YSZ grains is so sharp that in the interaction layers zirconia is no longer stabilized. This is important when YSZ is envisaged as simulant of UO{sub 2} or as inert matrix for Am-transmutation.

  18. Deterioration of yttria-stabilized zirconia by boron carbide alone or mixed with metallic or oxidized Fe, Cr, Zr mixtures

    Science.gov (United States)

    De Bremaecker, A.; Ayrault, L.; Clément, B.

    2014-08-01

    In the frame of severe accident conditions (PHEBUS FPT3 test), different experiments were carried out on the interactions of 20% yttria-stabilized zirconia (YSZ) and 20% ceria-stab zirconia with boron carbide or its oxidation products (B2O3): either tests under steam between 1230° and 1700 °C with B4C alone or B4C mixed with metals, either tests under Ar with boron oxide present in a mixture of iron and chromium oxides. In all cases an interaction was observed with formation of intergranular yttrium borate. At 1700 °C boron oxide is able to “pump out” the Y stabiliser from the YSZ grains but also some trace elements (Ca and Al) and to form a eutectic containing YBO3 and yttrium calcium oxy-borate (YCOB). At the same time a substantial swelling (“bloating”) of the zirconia happens, qualitatively similar to the foaming of irradiated fuel in contact with a Zr-melt. In all samples the lowering of the Y (or Ce)-content in the YSZ grains is so sharp that in the interaction layers zirconia is no longer stabilized. This is important when YSZ is envisaged as simulant of UO2 or as inert matrix for Am-transmutation.

  19. A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells.

    Science.gov (United States)

    Yang, Jun; Molouk, Ahmed Fathi Salem; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

    2015-12-30

    In recent years, solid oxide fuel cells fueled with ammonia have been attracting intensive attention. In this work, ammonia fuel was supplied to the Ni/yttria-stabilized zirconia (YSZ) cermet anode at 600 and 700 °C, and the change of electrochemical performance and microstructure under the open-circuit state was studied in detail. The influence of ammonia exposure on the microstructure of Ni was also investigated by using Ni/YSZ powder and Ni film deposited on a YSZ disk. The obtained results demonstrated that Ni in the cermet anode was partially nitrided under an ammonia atmosphere, which considerably roughened the Ni surface. Moreover, the destruction of the anode support layer was confirmed for the anode-supported cell upon the temperature cycling test between 600 and 700 °C because of the nitriding phenomenon of Ni, resulting in severe performance degradation.

  20. Band structure of TiO sub 2 -doped yttria-stabilized zirconia probed by soft-x-ray spectroscopy

    CERN Document Server

    Higuchi, T; Kobayashi, K; Yamaguchi, S; Fukushima, A; Shin, S

    2003-01-01

    The electronic structure of TiO sub 2 -doped yttria-stabilized zirconia (YSZ) has been studied by soft-X-ray emission spectroscopy (SXES) and X-ray absorption spectroscopy (XAS). The valence band is mainly composed of the O 2p state. The O 1s XAS spectrum exhibits the existence of the Ti 3d unoccupied state under the Zr 4d conduction band. The intensity of the Ti 3d unoccupied state increases with increasing TiO sub 2 concentration. The energy separation between the top of the valence band and the bottom of the Ti 3d unoccupied state is in accord with the energy gap, as expected from dc-polarization and total conductivity measurements. (author)

  1. Straight-chain halocarbon forming fluids for TRISO fuel kernel production - Tests with yttria-stabilized zirconia microspheres

    Science.gov (United States)

    Baker, M. P.; King, J. C.; Gorman, B. P.; Braley, J. C.

    2015-03-01

    Current methods of TRISO fuel kernel production in the United States use a sol-gel process with trichloroethylene (TCE) as the forming fluid. After contact with radioactive materials, the spent TCE becomes a mixed hazardous waste, and high costs are associated with its recycling or disposal. Reducing or eliminating this mixed waste stream would not only benefit the environment, but would also enhance the economics of kernel production. Previous research yielded three candidates for testing as alternatives to TCE: 1-bromotetradecane, 1-chlorooctadecane, and 1-iodododecane. This study considers the production of yttria-stabilized zirconia (YSZ) kernels in silicone oil and the three chosen alternative formation fluids, with subsequent characterization of the produced kernels and used forming fluid. Kernels formed in silicone oil and bromotetradecane were comparable to those produced by previous kernel production efforts, while those produced in chlorooctadecane and iodododecane experienced gelation issues leading to poor kernel formation and geometry.

  2. Low Thermal Conductivity Yttria-Stabilized Zirconia Thermal Barrier Coatings Using the Solution Precursor Plasma Spray Process

    Science.gov (United States)

    Jordan, Eric H.; Jiang, Chen; Roth, Jeffrey; Gell, Maurice

    2014-06-01

    The primary function of thermal barrier coatings (TBCs) is to insulate the underlying metal from high temperature gases in gas turbine engines. As a consequence, low thermal conductivity and high durability are the primary properties of interest. In this work, the solution precursor plasma spray (SPPS) process was used to create layered porosity, called inter-pass boundaries, in yttria-stabilized zirconia (YSZ) TBCs. IPBs have been shown to be effective in reducing thermal conductivity. Optimization of the IPB microstructure by the SPPS process produced YSZ TBCs with a thermal conductivity of 0.6 W/mK, an approximately 50% reduction compared to standard air plasma sprayed (APS) coatings. In preliminary tests, SPPS YSZ with IPBs exhibited equal or greater furnace thermal cycles and erosion resistance compared to regular SPPS and commercially made APS YSZ TBCs.

  3. High Temperature Thermal Properties of Columnar Yttria Stabilized Zirconia Thermal Barrier Coating Performed by Suspension Plasma Spraying

    Science.gov (United States)

    Bernard, B.; Schick, V.; Remy, B.; Quet, A.; Bianchi, L.

    2016-09-01

    Performance enhancement of gas turbines is a main issue for the aircraft industry. Over many years, a large part of the effort has been focused on the development of more insulating Thermal Barrier Coatings (TBCs). In this study, Yttria Stabilized Zirconia (YSZ) columnar structures are processed by Suspension Plasma Spraying (SPS). These structures have already demonstrated abilities to get improved thermal lifetime, similarly to standard YSZ TBCs performed by EB-PVD. Thermal diffusivity measurements coupled with differential scanning calorimetry analysis are performed from room temperature up to 1100 °C, first, on HastelloyX substrates and then, on bilayers including a SPS YSZ coating. Results show an effective thermal conductivity for YSZ performed by SPS lower than 1 W.m-1K-1 whereas EB- PVD YSZ coatings exhibit a value of 1.5 W.m-1K-1.

  4. Electrode properties of Sr-doped LaMnO{sub 3} on yttria-stabilized zirconia. 2: Electrode kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Heuveln, F.H. van [Netherlands Energy Research Foundation ECN, Petten (Netherlands); Bouwmeester, H.J.M. [Univ. of Twente, Enschede (Netherlands). Dept. of Chemical Technology

    1997-01-01

    A series of six cathodes Sr{sub 0.15}La{sub 0.85}MnO{sub 3} (SLM) on yttria-stabilized zirconia with different morphology of the electrode/electrolyte interface were characterized by ac impedance and dc polarization measurements. It is found that the electrode kinetics at elevated temperature (945 C) are governed by two serial processes. An activation process can be identified to occur at high cathodic overpotential, whereas a transport process competes with charge-transfer at comparatively low overpotential. Attention is drawn to the profound change in the electrocatalytic properties of Sr{sub 0.15}La{sub 0.85}MnO{sub 3} upon current passage and its influence in elucidation of the interfacial kinetics.

  5. Internal Friction Due to Localized Relaxation around Y-ions in Single Crystal Yttria-Stabilized Zirconia

    Science.gov (United States)

    Ohta, Michihiro; Kirimoto, Kenta; Nobugai, Kohji; Wigmore, J. Keith; Miyasato, Tatsuro

    2001-09-01

    The internal friction in single crystal yttria-stabilized zirconia (YSZ) doped with 9.5 mol% Y2O3 was measured for longitudinal sound waves in the frequency range from 10 Hz to 800 Hz using a vibrating reed technique. In the temperature range from 300 K to 700 K, observations of internal friction reveal two closely overlapping absorption peaks, confirming the existence of two relaxation modes in YSZ@. One of the peaks is due to diffusion relaxation, which is known to be responsible for long-range transport of O-ions. The second peak shows clearly the existence of localized relaxation, which is attributed to bound oxygen vacancies within the local structure which is formed around an Y-ion due to symmetry breaking. The absorption peak caused by the localized relaxation exhibits anisotropy resulting from the asymmetric local structure, and the strength of this peak changes with temperature reflecting the number of bound oxygen vacancies.

  6. Evaluation of nickel-yttria stabilized zirconia anode degradation during discharge operation and redox cycles operation by electrochemical calculation

    Science.gov (United States)

    Shimura, Takaaki; Jiao, Zhenjun; Shikazono, Naoki

    2016-10-01

    Degradation of Solid Oxide Fuel Cell (SOFC) anode during discharge operation and redox cycles operation were evaluated by three-dimensional electrochemical calculations using a Lattice Boltzmann method (LBM). Three dimensional microstructures were obtained by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) reconstruction. In the electrochemical calculations, changes in exchange current density and ionic conductivity of Yttria stabilized Zirconia (YSZ) during the operations were assumed and their values were calculated by fitting the calculated overpotential values to the experimental ones. Changes in triple phase boundary density calculated from the reconstructed microstructures were inconsistent with the gradual degradation observed during repeated redox-discharge cycles. Changes of the fitted exchange current density and YSZ ionic conductivity values in both discharge operation and redox cycle operation showed same tendency as the experimental results. Change in exchange current density or YSZ ionic conductivity should be considered as an essential factor which governs the cell performance change regardless of the redox treatment.

  7. Effect of autoclave induced low-temperature degradation on the adhesion energy between yttria-stabilized zirconia veneered with porcelain.

    Science.gov (United States)

    Li, Kai Chun; Waddell, J Neil; Prior, David J; Ting, Stephanie; Girvan, Liz; van Vuuren, Ludwig Jansen; Swain, Michael V

    2013-11-01

    To investigate the effect of autoclave induced low-temperature degradation on the adhesion energy between yttria-stabilized zirconia veneered with porcelain. The strain energy release rate using a four-point bending stable fracture test was evaluated for two different porcelains [leucite containing (VM9) and glass (Zirox) porcelain] veneered to zirconia. Prior to veneering the zirconia had been subjected to 0 (control), 1, 5, 10 and 20 autoclave cycles. The specimens were manufactured to a total bi-layer dimension of 30 mm × 8 mm × 3 mm. Subsequent scanning electron microscopy/energy dispersive spectrometry, electron backscatter diffraction and X-ray diffraction analysis were performed to identify the phase transformation and fracture behavior. The strain energy release rate for debonding of the VM9 specimens were significantly higher (pautoclave cycles lowered the strain energy release rate significantly (pautoclave cycles between 5 and 20. The monoclinic phase reverted back to tetragonal phase after undergoing conventional porcelain firing cycles. EBSD data showed significant changes of the grain size distribution between the control and autoclaved specimen (cycle 20). Increasing autoclave cycles only significantly decreased the adhesion of the VM9 layered specimens. In addition, a conventional porcelain firing schedule completely reverted the monoclinic phase back to tetragonal. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Reduction of the deposition temperature of high quality EuO films on Yttria Stabilized Zirconia by incorporating an MgO buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Moder, Iris [Group of Nanomaterials and Microsystems, Physics Department, Universitat Autònoma de Barcelona, Campus UAB, Torre C3-222, 08193 Bellaterra (Spain); Garcia, Gemma, E-mail: gemma.garcia@uab.cat [Group of Nanomaterials and Microsystems, Physics Department, Universitat Autònoma de Barcelona, Campus UAB, Torre C3-222, 08193 Bellaterra (Spain); Santiso, José [Centre d' Investigació en Nanociència i Nanotecnologia, CIN2 (CSIC/ICN), Campus UAB, 08193 Bellaterra, Barcelona (Spain); Moodera, Jagadeesh S.; Miao, Guoxing X. [Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Lopeandía, Aitor F. [Group of Nanomaterials and Microsystems, Physics Department, Universitat Autònoma de Barcelona, Campus UAB, Torre C3-222, 08193 Bellaterra (Spain); Rodríguez-Viejo, Javier [Group of Nanomaterials and Microsystems, Physics Department, Universitat Autònoma de Barcelona, Campus UAB, Torre C3-222, 08193 Bellaterra (Spain); MATGAS Research Centre, Campus UAB, 08193 Bellaterra (Spain)

    2013-03-01

    High quality stoichiometric EuO ferromagnetic thin films have been grown by Molecular Beam Epitaxy (MBE) on MgO coated-Yttria Stabilized Zirconia (YSZ) (100) substrates. The proof is made that introducing an MgO buffer layer, that avoid oxygen transfer from YSZ to EuO, allows the preparation of high quality stoichiometric EuO films at reduced deposition temperature compared with films directly deposited onto YSZ, maintaining similar Eu flux and oxygen partial pressure. Structure and texture were characterized by X-ray diffraction showing out-of plane and in-plane ordering for films deposited onto MgO buffer layers. The crystallographic quality was corroborated by a Curie temperature around 69 K and a magnetization moment close or equal to 6.49 · 10{sup −23} J/T (7 μ{sub B}), corresponding to bulk EuO single crystal values. - Highlights: ► EuO films were epitaxially grown on MgO coated Yttria Stabilized Zirconia. ► Deposition temperature was reduced compared to bare Yttria Stabilized Zirconia. ► Epitaxial texture was confirmed by in-plane X-ray diffraction. ► Composition of the heterostructure was defined by X-ray Photoelectron Spectroscopy. ► Single crystal like EuO magnetic moment and coercive field were measured.

  9. Quinone-rich polydopamine functionalization of yttria stabilized zirconia for apatite biomineralization: The effects of coating temperature

    Science.gov (United States)

    Zain, Norhidayu Muhamad; Hussain, Rafaqat; Abdul Kadir, Mohammed Rafiq

    2015-08-01

    The use of yttria stabilized zirconia (YSZ) as biomedical implants is often offset by its bioinert nature that prevents its osseointegration to occur. Therefore, the functionalization of YSZ surface by polydopamine to facilitate the biomineralization of apatite layer on top of the coated film has incessantly been studied. In this study YSZ discs were first immersed in 2 mg/mL of stirred dopamine solution at coating temperatures between 25 and 80 °C. The specimens were then incubated for 7d in 1.5 SBF. The effect of coating temperature on the properties (chemical compositions and wettability) and the apatite mineralization on top of the generated films was investigated. It was found that at 50 °C, the specimen displayed the highest intensity of Ca 2p peak (1.55 ± 0.42 cps) with Ca/P ratio of 1.67 due to the presence of abundant quinone groups (Cdbnd O). However, the hydrophilicity (40.9 ± 01.7°) was greatly improved at 60 °C accompanied by the highest film thickness of 306 nm. Therefore, it was concluded that the presence of high intensity of quinone groups (Cdbnd O) in polydopamine film at elevated temperature affects the chelation of Ca2+ ions and thus enhance the growth of apatite layer on top of the functionalized YSZ surface.

  10. Kinetic Monte Carlo Investigation of the Effects of Vacancy Pairing on Oxygen Diffusivity in Yttria-Stabilized Zirconia

    Science.gov (United States)

    Good, Brian S.

    2011-01-01

    Yttria-stabilized zirconia s high oxygen diffusivity and corresponding high ionic conductivity, and its structural stability over a broad range of temperatures, have made the material of interest for use in a number of applications, for example, as solid electrolytes in fuel cells. At low concentrations, the stabilizing yttria also serves to increase the oxygen diffusivity through the presence of corresponding oxygen vacancies, needed to maintain charge neutrality. At higher yttria concentration, however, diffusivity is impeded by the larger number of relatively high energy migration barriers associated with yttrium cations. In addition, there is evidence that oxygen vacancies preferentially occupy nearest-neighbor sites around either dopant or Zr cations, further affecting vacancy diffusion. We present the results of ab initio calculations that indicate that it is energetically favorable for oxygen vacancies to occupy nearest-neighbor sites adjacent to Y ions, and that the presence of vacancies near either species of cation lowers the migration barriers. Kinetic Monte Carlo results from simulations incorporating this effect are presented and compared with results from simulations in which the effect is not present.

  11. High-temperature stability of yttria-stabilized zirconia thermal barrier coating on niobium alloy—C-103

    Indian Academy of Sciences (India)

    S S Panwar; T Umasankar Patro; K Balasubramanian; B Venkataraman

    2016-02-01

    Thermal barrier coatings (TBCs) of yttria-stabilized zirconia (YSZ) of different thicknesses with an intermediate bond coat were deposited on C-103 Nb alloy using the air plasma spraying technique. The coatings were subjected to rapid infra-red (IR) heating ($\\sim$25°C s$^{−1}$) up to $\\sim$1250°C and exposed up to 100 s at this temperature with heat flux varying from 55 to 61 Wcm$^{−2}$. The TBCs were found to be stable and intact after the heat treatment. In contrast, at the same conditions, the uncoated C-103 alloy specimen showed extensive oxidation followed by weight loss due to spallation. A maximum temperature drop of $\\sim$200°C was observed on the opposite side of the coated alloy with 600 $\\mu$m YSZ coat; as against negligible temperature drop in case of bare alloy specimen. The temperature drop was found to increase with the coating thickness of YSZ. The coatings before and after IR heating were investigated by scanning electron microscopy, X-ray diffraction, electron probe microanalysis, microhardness and residual stress measurements in order to understand the effect of thermal shock on the properties of the TBC. On account of these high-temperature properties, YSZ coating along with the bond coat is expected to find potential thermal barrier coating system on niobium alloys for supersonic vehicles.

  12. Straight-chain halocarbon forming fluids for TRISO fuel kernel production – Tests with yttria-stabilized zirconia microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Baker, M.P. [Nuclear Science and Engineering Program, Metallurgical and Materials Engineering Department, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401 (United States); King, J.C., E-mail: kingjc@mines.edu [Nuclear Science and Engineering Program, Metallurgical and Materials Engineering Department, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401 (United States); Gorman, B.P. [Metallurgical and Materials Engineering Department, Colorado Center for Advanced Ceramics, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401 (United States); Braley, J.C. [Nuclear Science and Engineering Program, Chemistry and Geochemistry Department, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401 (United States)

    2015-03-15

    Highlights: • YSZ TRISO kernels formed in three alternative, non-hazardous forming fluids. • Kernels characterized for size, shape, pore/grain size, density, and composition. • Bromotetradecane is suitable for further investigation with uranium-based precursor. - Abstract: Current methods of TRISO fuel kernel production in the United States use a sol–gel process with trichloroethylene (TCE) as the forming fluid. After contact with radioactive materials, the spent TCE becomes a mixed hazardous waste, and high costs are associated with its recycling or disposal. Reducing or eliminating this mixed waste stream would not only benefit the environment, but would also enhance the economics of kernel production. Previous research yielded three candidates for testing as alternatives to TCE: 1-bromotetradecane, 1-chlorooctadecane, and 1-iodododecane. This study considers the production of yttria-stabilized zirconia (YSZ) kernels in silicone oil and the three chosen alternative formation fluids, with subsequent characterization of the produced kernels and used forming fluid. Kernels formed in silicone oil and bromotetradecane were comparable to those produced by previous kernel production efforts, while those produced in chlorooctadecane and iodododecane experienced gelation issues leading to poor kernel formation and geometry.

  13. Residual stress and buckling patterns of free-standing yttria-stabilized-zirconia membranes fabricated by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Evans, A.; Prestat, M.; Toelke, R.; Schlupp, M.V.F.; Gauckler, L.J. [ETH Zurich, Nonmetallic Inorganic Materials, Zurich (Switzerland); Safa, Y.; Hocker, T. [ZHAW Winterthur, Institute of Computational Physics, Winterthur (Switzerland); Courbat, J.; Briand, D.; Rooij, N.F. de [Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Microengineering, Neuchatel (Switzerland); Courty, D. [ETH Zurich, Laboratory for Nanometallurgy, Zurich (Switzerland)

    2012-08-15

    The residual stress and buckling patterns of free-standing 8 mol.% yttria-stabilized-zirconia (8YSZ) membranes prepared by pulsed laser deposition and microfabrication techniques on silicon substrates are investigated by wafer curvature, light microscopy, white light interferometry, and nanoindentation. The 300 nm thin 8YSZ membranes (390 {mu}m x 390 {mu}m) deposited at 25 C are almost flat after free-etching, whereas deposition at 700 C yields strongly buckled membranes with a compressive stress of -1,100 {+-} 150 MPa and an out-of-plane-displacement of 6.5 {mu}m. These latter membranes are mechanically stable during thermal cycling up to 500 C. Numerical simulations of the buckling shape using the Rayleigh-Ritz-method and a Young's modulus of 200 GPa are in good agreement with the experimental data. The simulated buckling patterns are used to extract the local stress distribution within the free-standing membrane which consists of tensile and compressive stress regions that are below the failure stresses. This is important regarding the application in, e.g., microsolid oxide fuel cell membranes which must be thermomechanically stable during microfabrication and device operation. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Direct ceramic inkjet printing of yttria-stabilized zirconia electrolyte layers for anode-supported solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tomov, R.I.; Hopkins, S.C. [Applied Superconductivity and Cryoscience Group, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB4 3QZ (United Kingdom); Krauz, M.; Kluczowski, J.R. [Institute of Power Engineering, Ceramic Department CEREL, 36-040 Boguchwala (Poland); Jewulski, J. [Institute of Power Engineering, Fuel Cells Department, 02-981 Warsaw (Poland); Glowacka, D.M. [Detector Physics Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom); Glowacki, B.A. [Applied Superconductivity and Cryoscience Group, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB4 3QZ (United Kingdom); Institute of Power Engineering, Fuel Cells Department, 02-981 Warsaw (Poland)

    2010-11-01

    Electromagnetic drop-on-demand direct ceramic inkjet printing (EM/DCIJP) was employed to fabricate dense yttria-stabilized zirconia (YSZ) electrolyte layers on a porous NiO-YSZ anode support from ceramic suspensions. Printing parameters including pressure, nozzle opening time and droplet overlapping were studied in order to optimize the surface quality of the YSZ coating. It was found that moderate overlapping and multiple coatings produce the desired membrane quality. A single fuel cell with a NiO-YSZ/YSZ ({proportional_to}6 {mu}m)/LSM + YSZ/LSM architecture was successfully prepared. The cell was tested using humidified hydrogen as the fuel and ambient air as the oxidant. The cell provided a power density of 170 mW cm{sup -2} at 800 C. Scanning electron microscopy (SEM) revealed a highly coherent dense YSZ electrolyte layer with no open porosity. These results suggest that the EM/DCIJP inkjet printing technique can be successfully implemented to fabricate electrolyte coatings for SOFC thinner than 10 {mu}m and comparable in quality to those fabricated by more conventional ceramic processing methods. (author)

  15. Ionic properties of ultrathin yttria-stabilized zirconia thin films fabricated by atomic layer deposition with water, oxygen, and ozone

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ho Keun; Jang, Dong Young; Kim, Jun Woo [School of Mechanical Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of); Bae, Kiho [School of Mechanical Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of); High-Temperature Energy Materials Research Center, Korea Institute of Science and Technology (KIST), Hawolgok-dong, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Shim, Joon Hyung, E-mail: shimm@korea.ac.kr [School of Mechanical Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of)

    2015-08-31

    We compared the ionic properties of yttria-stabilized zirconia (YSZ) thin films prepared by atomic layer deposition (ALD) using various oxidants including water, oxygen, and ozone. Cross-plane conductivity measurements were performed at low temperature (50 °C) and high temperature (450 °C) using AC impedance spectroscopy. As a result, we have confirmed that the conductivity of ALD YSZ films below 300 °C is greater by several orders of magnitude compared to the nano-scale YSZ thin films synthesized by other conventional techniques. Among the ALD YSZ samples, ALD YSZ fabricated using water showed the highest conductivity while ALD YSZ fabricated using ozone showed the lowest. We have analyzed this result in relation with grain morphology characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), and the chemical binding states measured by X-ray photoelectron spectroscopy (XPS). - Highlights: • YSZ is prepared by atomic layer deposition (ALD) with H{sub 2}O, O{sub 2}, and O{sub 3} as oxidants. • Grain size of ALD YSZ membranes deposited using H{sub 2}O is the smallest. • Conductivity of ALD YSZ made with H{sub 2}O shows the highest value below 300 °C. • Conductivity trends coincide with the hydroxyl group content measured by XPS.

  16. Coupling between creep and redox behavior in nickel - yttria stabilized zirconia observed in-situ by monochromatic neutron imaging

    Science.gov (United States)

    Makowska, Malgorzata Grazyna; Kuhn, Luise Theil; Frandsen, Henrik Lund; Lauridsen, Erik Mejdal; De Angelis, Salvatore; Cleemann, Lars Nilausen; Morgano, Manuel; Trtik, Pavel; Strobl, Markus

    2017-02-01

    Ni-YSZ (nickel - yttria stabilized zirconia) is a material widely used for electrodes and supports in solid oxide electrochemical cells. The mechanical and electrochemical performance of these layers, and thus the whole cell, depends on their microstructure. During the initial operation of a cell, NiO is reduced to Ni. When this process is conducted under external load, like also present in a stack assembly, significant deformations of NiO/Ni-YSZ composite samples are observed. The observed creep is orders of magnitude larger than the one observed after reduction during operation. This phenomenon is referred to as accelerated creep and is expected to have a significant influence on the microstructure development and stress field present in the Ni-YSZ in solid oxide electrochemical cells (SOCs), which is highly important for the durability of the SOC. In this work we present energy selective neutron imaging studies of the accelerated creep phenomenon in Ni/NiO-YSZ composite during reduction and also during oxidation. This approach allowed us to observe the phase transition and the creep behavior simultaneously in-situ under SOC operation-like conditions.

  17. Preparation of alumina-doped yttria-stabilized zirconia nanopowders by microwave-assisted peroxyl-complex coprecipitation

    Institute of Scientific and Technical Information of China (English)

    QI Liang; XU Ming-xia; TIAN Yu-ming; ZHAO Jin-wei

    2006-01-01

    Alumina-doped yttria-stabilized zirconia (ADYSZ) nanopowders were prepared by microwave-assisted peroxyl-complex coprecipitation (MAPCC) using ZrOCl2·8H2O,Y2O3 and AlCl3·6H2O as starting materials,NH3·H2O as precipitant and H2O2 as complexant. The effects of adding H2O2 and microwave drying on the preparation and properties of ADYSZ were investigated. The precursors and nanopowders were studied by EDX,XRD,SEM and TEM techniques. The results show that the uniformity of component distribution within ADYSZ nanopowders is improved by adding appropriate dosage of H2O2. Complexing reaction between H2O2 and Zr4+ ion restrains the hydrolyzation and precipitation of Zr4+ ion. With the addition of H2O2,Al3+,Y3+ and Zr4+ ions can be precipitated synchronously in a relatively narrow range of pH value. H2O2 also improves the filterability of the wet precipitate. The highly hydrophilic precipitates can be quickly and effectively separated from aqueous solution. During microwave drying process,the moisture of wet precursors is selectively heated. Quick expansion of steam vapor within the wet colloidal particles causes the aggregations burst into numerous tiny lumps. Compared with oven drying,microwave drying can not only shorten drying time but also reduce aggregation intensity of the resultant ADYSZ nanopowders.

  18. Surface and Mechanical Characterization of Dental Yttria-Stabilized Tetragonal Zirconia Polycrystals (3Y-TZP) After Different Aging Processes.

    Science.gov (United States)

    Pinto, Palena A; Colas, Guillaume; Filleter, Tobin; De Souza, Grace M

    2016-12-01

    Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) is a ceramic material used in indirect dental restorations. However, phase transformation at body temperature may compromise the material's mechanical properties, affecting the clinical performance of the restoration. The effect of mastication on 3Y-TZP aging has not been investigated. 3Y-TZP specimens (IPS E-max ZirCAD and Z5) were aged in three different modes (n=13): no aging (control), hydrothermal aging (HA), or chewing simulation (CS). Mechanical properties and surface topography were analyzed. Analysis of variance showed that neither aging protocol (p=0.692) nor material (p=0.283) or the interaction between them (p=0.216) had a significant effect on flexural strength, values ranged from 928.8 MPa (IPSHA) to 1,080.6 MPa (Z5HA). Nanoindentation analysis showed that material, aging protocol, and the interaction between them had a significant effect (p<0.001) on surface hardness and reduced Young's modulus. The compositional analysis revealed similar yttrium content for all the experimental conditions (aging: p=0.997; material: p=0.248; interaction material×aging: p=0.720). Atomic force microscopy showed an effect of aging protocols on phase transformation, with samples submitted to CS exhibiting features compatible with maximized phase transformation, such as increased volume of the material microstructure at the surface leading to an increase in surface roughness.

  19. A porous yttria-stabilized zirconia layer to eliminate the delamination of air electrode in solid oxide electrolysis cells

    Science.gov (United States)

    Khan, Muhammad Shirjeel; Xu, Xiaoyong; Zhao, Jie; Knibbe, Ruth; Zhu, Zhonghua

    2017-08-01

    Delamination of La0.8Sr0.2MnO3-δ (LSM) in solid oxide electrolysis cells (SOECs) is usually associated with the high oxygen partial pressure build-up at the LSM-YSZ (yttria-stabilized zirconia) interface. Here we sandwich a porous YSZ layer between the LSM electrode and YSZ electrolyte to release this oxygen pressure. Symmetric cells with and without the porous YSZ layers are prepared and tested in air at 800 °C under the current densities of 0.5 and 1 A cm-2 for 100 h. Voltage change is continuously monitored, and impedance spectrum studies have been carried out before and after testing. No delamination has been observed for the samples with the porous YSZ layer even after 100 h. The improved performance for these samples is due to the shift of oxygen evolution reaction from the dense YSZ-LSM interface to a porous YSZ-LSM interface. This shift also helps the oxygen to be easily released instead of going into the pores or grain boundaries of the electrolyte. On the other hand, for the sample without the porous YSZ layer, the LSM is totally delaminated from the electrolyte just after 70 h.

  20. Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

    Science.gov (United States)

    Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

    2015-08-01

    Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

  1. Resistance to sulfur poisoning of the gold doped nickel/yttria-stabilized zirconia with interface oxygen vacancy

    Science.gov (United States)

    Zhang, Yanxing; Yang, Zongxian

    2014-12-01

    The effects of IB metal (Gold, Silver, and Copper) dopants at the triple phase boundary (TPB) on the resistance to sulfur poisoning of the Nickel/Yttria-Stabilized Zirconia (YSZ) with interface oxygen vacancy (denoted as Ni/YSZ-Ov) are studied using the first-principles method based on density functional theory. Models with Au, Ag, Cu dopants at the TPB of Ni/YSZ-Ov are proposed. It is found that the Au dopant prefers to be at the neighbor of the oxygen vacancy site (denoted as NiAu-d/YSZ-Ov) while the Ag, Cu dopants tend to be located at the top Ni layer, which have little effects on the sulfur adsorption at the interface oxygen vacancy site. Compared with Ni/YSZ-Ov, the NiAu-d/YSZ-Ov can not only weaken the sulfur adsorption at the interface oxygen vacancy site, but also restrain the diffusion of sulfur to the interface oxygen vacancy. Instead, the adsorbed S at the oxygen vacancy is more easily to diffuse out of the interface oxygen vacancy site. So we propose that doping Au in Ni at the neighbor of the interface oxygen vacancy site would be good way to increase the resistance to sulfur poisoning of the Ni/YSZ-Ov anode.

  2. Surface quality of yttria-stabilized tetragonal zirconia polycrystal in CAD/CAM milling, sintering, polishing and sandblasting processes.

    Science.gov (United States)

    Alao, Abdur-Rasheed; Stoll, Richard; Song, Xiao-Fei; Miyazaki, Takashi; Hotta, Yasuhiro; Shibata, Yo; Yin, Ling

    2017-01-01

    This paper studied the surface quality (damage, morphology, and phase transformation) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in CAD/CAM milling, and subsequent polishing, sintering and sandblasting processes applied in dental restorations. X-ray diffraction and scanning electron microscopy (SEM) were used to scan all processed surfaces to determine phase transformations and analyse surface damage morphology, respectively. The average surface roughness (Ra) and maximum roughness (Rz) for all processed surfaces were measured using desk-top SEM-assisted morphology analytical software. X-ray diffraction patterns prove the sintering-induced monoclinic-tetragonal phase transformation while the sandblasting-induced phase transformation was not detected. The CAD/CAM milling of pre-sintered Y-TZP produced very rough surfaces with extensive fractures and cracks. Simply polishing or sintering of milled pre-sintered surfaces did not significantly improve their surface roughness (ANOVA, p>0.05). Neither sintering-polishing of the milled surfaces could effectively improve the surface roughness (ANOVA, p>0.05). The best surface morphology was produced in the milling-polishing-sintering process, achieving Ra=0.21±0.03µm and Rz=1.73±0.04µm, which meets the threshold for bacterial retention. Sandblasting of intaglios with smaller abrasives was recommended as larger abrasive produced visible surface defects. This study provides technical insights into process selection for Y-TZP to achieve the improved restorative quality.

  3. Electrochemical and Oxidation Behavior of Yttria Stabilized Zirconia Coating on Zircaloy-4 Synthesized via Sol-Gel Process

    Directory of Open Access Journals (Sweden)

    S. Rezaee

    2013-01-01

    Full Text Available Sol-gel 8 wt.% Yttria Stabilized Zirconia (YSZ thin films were prepared on zirconium (zircaloy-4 alloy by dip-coating technique followed by heat treating at various temperatures (200°C, 400°C, and 700°C in order to improve both electrochemical corrosion and high temperature oxidation properties of the substrate. Differential thermal analysis and thermogravimetric analysis (DTA-TG revealed the coating formation process. X-ray diffraction (XRD was used to determine the crystalline phase structure transformation. The morphological characterization of the coatings was carried out using scanning electron microscopy (SEM. The electrochemical behavior of the coated and uncoated samples was investigated by means of open circuit potential, Tafel, and electrochemical impedance spectroscopy (EIS in a 3.5 wt.% NaCl solution. The homogeneity and surface appearance of coatings produced was affected by the heat treatment temperature. According to the corrosion parameters, the YSZ coatings showed a considerable increase in the corrosion resistance, especially at higher heat treatment temperatures. The coating with the best quality, from the surface and corrosion point of view, was subjected to oxidation test in air at 800°C. The coated sample presented a 25% reduction in oxidation rate in comparison with bare substrate.

  4. Investigation of the oxygen exchange mechanism on Pt|yttria stabilized zirconia at intermediate temperatures: Surface path versus bulk path

    Science.gov (United States)

    Opitz, Alexander K.; Lutz, Alexander; Kubicek, Markus; Kubel, Frank; Hutter, Herbert; Fleig, Jürgen

    2011-01-01

    The oxygen exchange kinetics of platinum on yttria-stabilized zirconia (YSZ) was investigated by means of geometrically well-defined Pt microelectrodes. By variation of electrode size and temperature it was possible to separate two temperature regimes with different geometry dependencies of the polarization resistance. At higher temperatures (550–700 °C) an elementary step located close to the three phase boundary (TPB) with an activation energy of ∼1.6 eV was identified as rate limiting. At lower temperatures (300–400 °C) the rate limiting elementary step is related to the electrode area and exhibited a very low activation energy in the order of 0.2 eV. From these observations two parallel pathways for electrochemical oxygen exchange are concluded. The nature of these two elementary steps is discussed in terms of equivalent circuits. Two combinations of parallel rate limiting reaction steps are found to explain the observed geometry dependencies: (i) Diffusion through an impurity phase at the TPB in parallel to diffusion of oxygen through platinum – most likely along Pt grain boundaries – as area-related process. (ii) Co-limitation of oxygen diffusion along the Pt|YSZ interface and charge transfer at the interface with a short decay length of the corresponding transmission line (as TPB-related process) in parallel to oxygen diffusion through platinum. PMID:22210951

  5. Investigation of the oxygen exchange mechanism on Pt|yttria stabilized zirconia at intermediate temperatures: Surface path versus bulk path.

    Science.gov (United States)

    Opitz, Alexander K; Lutz, Alexander; Kubicek, Markus; Kubel, Frank; Hutter, Herbert; Fleig, Jürgen

    2011-11-30

    The oxygen exchange kinetics of platinum on yttria-stabilized zirconia (YSZ) was investigated by means of geometrically well-defined Pt microelectrodes. By variation of electrode size and temperature it was possible to separate two temperature regimes with different geometry dependencies of the polarization resistance. At higher temperatures (550-700 °C) an elementary step located close to the three phase boundary (TPB) with an activation energy of ∼1.6 eV was identified as rate limiting. At lower temperatures (300-400 °C) the rate limiting elementary step is related to the electrode area and exhibited a very low activation energy in the order of 0.2 eV. From these observations two parallel pathways for electrochemical oxygen exchange are concluded.The nature of these two elementary steps is discussed in terms of equivalent circuits. Two combinations of parallel rate limiting reaction steps are found to explain the observed geometry dependencies: (i) Diffusion through an impurity phase at the TPB in parallel to diffusion of oxygen through platinum - most likely along Pt grain boundaries - as area-related process. (ii) Co-limitation of oxygen diffusion along the Pt|YSZ interface and charge transfer at the interface with a short decay length of the corresponding transmission line (as TPB-related process) in parallel to oxygen diffusion through platinum.

  6. High temperature {sup 17}O MAS NMR study of calcia, magnesia, scandia and yttria stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Namjun; Stebbins, Jonathan F. [Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 (United States); Hsieh, Cheng-Han [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Huang, Hong [Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States); Prinz, Fritz B. [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Department of Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States)

    2007-11-15

    High-resolution {sup 17}O MAS NMR can provide unique constraints on local structure and oxide ion dynamics in conductive zirconia ceramics of interest for fuel cells and other technologies. We describe here NMR and bulk conductivity measurements for scandia, yttria, calcia, and magnesia stabilized zirconias, including MAS NMR spectra collected in situ at temperatures up to 700 C. All of the cubic compounds with high dopant levels showed line narrowing and coalescence in this temperature range, and the temperature-induced changes in line widths are qualitatively correlated with the bulk conductivities. A monoclinic zirconia with 2% Sc{sub 2}O{sub 3} dopant level (expected to have relatively low ionic mobility) showed no motional averaging of its two {sup 17}O NMR peaks even at 600 C, but instead is observed to begin to transform to a disordered, possibly cubic or tetragonal phase at 600 to 700 C. {sup 17}O MAS NMR spectra of calcia stabilized zirconia were analyzed in detail and the exchange frequencies as a function of temperature, conductivity, and activation energy were estimated and compared with bulk conductivities. The activation energy estimated from NMR exchange frequencies is somewhat lower than that of bulk conductivity but the conductivities estimated from NMR appear to be lower than bulk conductivity. (author)

  7. Effect of metal chloride solutions on coloration and biaxial flexural strength of yttria-stabilized zirconia

    Science.gov (United States)

    Oh, Gye-Jeong; Lee, Kwangmin; Lee, Doh-Jae; Lim, Hyun-Pil; Yun, Kwi-Dug; Ban, Jae-Sam; Lee, Kyung-Ku; Fisher, John G.; Park, Sang-Won

    2012-10-01

    The effect of three kinds of transition metal dopants on the color and biaxial flexural strength of zirconia ceramics for dental applications was evaluated. Presintered zirconia discs were colored through immersion in aqueous chromium, molybdenum and vanadium chloride solutions and then sintered at 1450 °C. The color of the doped specimens was measured using a digital spectrophotometer. For biaxial flexural strength measurements, specimens infiltrated with 0.3 wt% of each aqueous chloride solution were used. Uncolored discs were used as a control. Zirconia specimens infiltrated with chromium, molybdenum and vanadium chloride solutions were dark brown, light yellow and dark yellow, respectively. CIE L*, a*, and b* values of all the chromium-doped specimens and the specimens infiltrated with 0.1 wt% molybdenum chloride solution were in the range of values for natural teeth. The biaxial flexural strengths of the three kinds of metal chloride groups were similar to the uncolored group. These results suggest that chromium and molybdenum dopants can be used as colorants to fabricate tooth colored zirconia ceramic restorations.

  8. Chemical and structural changes in manganese-doped yttria-stabilized zirconia studied by electron energy loss spectroscopy combined with electron diffraction

    DEFF Research Database (Denmark)

    Appel, C.C.; Botton, G.A.; Horsewell, A.

    1999-01-01

    Solid solution of manganese in yttria-stabilized zirconia (YSZ) may occur in the electrolyte of solid oxide fuel cells. Possible changes in valence, coordination, and site occupancy of Mn in YSZ are of interest. Also, subsequent structural modification of the cubic YSZ, as well as the possible...... ordering of vacancies, has important consequences for the ionic conductivity, Electron energy loss spectroscopy was used to measure the O K and the Mn L edge of Mn in solid solution in a zirconia host lattice. The ratio Mn L-3/L-2 was determined for some manganese oxides and for Mn in solid solution...

  9. Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures

    Science.gov (United States)

    Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

    2009-01-01

    The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

  10. Nano-structured yttria-stabilized zirconia coating by electrophoretic deposition

    Energy Technology Data Exchange (ETDEWEB)

    Maleki-Ghaleh, H., E-mail: H_Maleki@sut.ac.ir [Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Rekabeslami, M. [Faculty of Mechanical Engineering, Materials Science and Engineering Division, K. N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Shakeri, M.S. [Materials and Energy Research Center, Karaj (Iran, Islamic Republic of); Siadati, M.H. [Faculty of Mechanical Engineering, Materials Science and Engineering Division, K. N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Javidi, M. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Talebian, S.H. [Faculty of Petroleum Engineering, Universiti Technologi Petronas, Perak (Malaysia); Aghajani, H. [Department of Materials Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2013-09-01

    The most important role of thermal barrier coatings is to reduce the temperature of the substrate in high temperature applications. Nanoparticle zirconia might be a suitable choice for improving the efficiency of thermal barrier coatings. Nanostructured coatings have lower thermal conduction, higher thermal expansion and lower dimensional variations at higher temperatures in comparison with the microstructured coatings. Electrophoretic deposition has been preferred for thermal barrier coatings due to its simplicity, controllability and low cost. In the present study, three different suspensions of ZrO{sub 2}–8 wt%Y{sub 2}O{sub 3} (40 nm) made with ethanol, acetone and acetyl acetone were used. Electrophoretic deposition was conducted at a fixed voltage of 60 V for 120 s on aluminized Inconel 738-LC, and then heat treated at 1100{sup o}C for 4 h in air atmosphere. The coating morphology and elemental distribution were studied using scanning electron microscopy. It was observed that suspension media have an important effect on the quality of the final product. Acetyl acetone showed better dispersion of particles than the other two media. Consequently, deposition from acetyl acetone resulted in uniform and crack-free layers while those from ethanol and acetone were completely non-uniform due to agglomeration and low viscosity, respectively.

  11. Role of dispersion conditions on grindability of yttria stabilized zirconia (YSZ) powders

    Indian Academy of Sciences (India)

    S Ramanathan; K P Krishna Kumar; P K De; S Banerjee

    2005-04-01

    A precursor for zirconia – 8 mole% yttria (YSZ–ZrO2–8 m% Y2O3) powder was prepared by coprecipitation and the calcination temperature was fixed as 900°C from TG–DTA and XRD studies. The calcined powder could be dry ground only to a mean particle size (50) of 6 m containing substantial amount of coarse agglomerates in the size range 10–100 m. The dispersion conditions for its wet grinding were evaluated through zeta-potential and viscosity studies. The zeta-potential variation with pH of the aqueous suspensions of the powder exhibited maximum numerical values at 3 and 11 pH, exhibiting the ideal pHs for dispersion stability through electrostatic columbic repulsion mechanism. Slurries of dry ground powders with solid concentration in the range 15–30 vol.% exhibited pseudo-plastic flow characteristics, indicating presence of flocculates. With progress of grinding, the increase in viscosity of the slurries became less significant with decreasing solid concentration. Even though the particle size of the ground slurries decreased with decreasing solid content, there was little change in it for slurries with solid content < 20 vol.%. Grinding conditions for formation of sinter-active powders of YSZ with sub-micron size (50\\ ∼ 0.7 m free of agglomerates of size > 5 m) were established. Compacts from this powder could be sintered at 1400°C to translucent bodies with 99% theoretical density.

  12. Phase transformations in air plasma-sprayed yttria-stabilized zirconia thermal barrier coatings

    Directory of Open Access Journals (Sweden)

    Julián D. Osorio

    2014-01-01

    Full Text Available En este trabajo, las transformaciones de fase en Recubrimientos de Barrera Térmica (TBC constituidos por ZrO 2 – 8 wt.% Y2O3 (zirconia - 8 wt.% ytrria fueron estudiados a través de Difracción de Rayos X (XRD y refinamiento Rietveld. Las muestras de TBC fueron depositadas mediante aspersión por plasma atmosférico sobre un sustrato tipo Inconel 625 y fueron tratadas térmicamente con dos condiciones diferentes: en la primera se utilizó una temperatura de 1100oC con tiempos de exposición entre 1 hora y 1000 horas; en la segunda las muestras fueron sometidas a temperaturas entre 700oC y 1100o durante 50 horas. De acuerdo a los resultados obtenidos mediante refinamiento Rietveld el contenido de fase cúbica en el recubrimiento (TC se incrementa con el tiempo y la temperatura, desde 7.3 wt.% hasta 15.7 wt.% después de 1000 horas a 1100oC. La fase cúbica en grandes cantidades es indeseable debido a que presenta inferiores propiedades mecánicas cuando se compara con la fase tetragonal. Después de 800 horas de exposición a alta temperatura, el contenido de Y2O3 en la fase tetragonal se reduce hasta 6.6 wt.% y una fracción de la fase tetragonal transforma a monoclínica durante el enfriamiento. La fase monoclínica alcanza 18.0 wt.% después de 1000 horas. Esta fase es también indeseable porque además de tener una mayor conductividad térmica, la transformación de tetragonal a monoclínica viene acompañada de un cambio volumétrico de alrededor de 5% que promueve la formación y propagación de grietas, las cuales comprometen la integridad del recubrimiento.

  13. Microstructural Characterization of Yttria-Stabilized Zirconia Sintered at Different Temperatures Using 3D EBSD, 2D EBSD and Stereological Calculations

    Science.gov (United States)

    Bobrowski, Piotr; Faryna, Marek; Pędzich, Zbigniew

    2017-06-01

    A set of yttria-stabilized zirconia samples sintered at increasing temperatures was investigated using two-dimensional (2D) and three-dimensional (3D) electron backscatter diffraction (EBSD) techniques to calculate grain size distributions and grain boundary densities. The obtained results were compared to the results of stereological calculations and revealed that mean intercept length, a commonly used stereological parameter, is ca. 20% lower than an average grain diameter derived from 2D and 3D EBSD data. Moreover, the results based on 2D and 3D EBSD analyses were similar to each other in grain boundary density, while the values obtained from the stereological approach were noticeably lower.

  14. Plasma-enhanced atomic layer deposition of nanoscale yttria-stabilized zirconia electrolyte for solid oxide fuel cells with porous substrate.

    Science.gov (United States)

    Ji, Sanghoon; Cho, Gu Young; Yu, Wonjong; Su, Pei-Chen; Lee, Min Hwan; Cha, Suk Won

    2015-02-11

    Nanoscale yttria-stabilized zirconia (YSZ) electrolyte film was deposited by plasma-enhanced atomic layer deposition (PEALD) on a porous anodic aluminum oxide supporting substrate for solid oxide fuel cells. The minimum thickness of PEALD-YSZ electrolyte required for a consistently high open circuit voltage of 1.17 V at 500 °C is 70 nm, which is much thinner than the reported thickness of 180 nm using nonplasmatic ALD and is also the thinnest attainable value reported in the literatures on a porous supporting substrate. By further reducing the electrolyte thickness, the grain size reduction resulted in high surface grain boundary density at the cathode/electrolyte interface.

  15. Modeling of gas transport with electrochemical reaction in nickel-yttria-stabilized zirconia anode during thermal cycling by Lattice Boltzmann method

    Science.gov (United States)

    Guo, Pengfei; Guan, Yong; Liu, Gang; Liang, Zhiting; Liu, Jianhong; Zhang, Xiaobo; Xiong, Ying; Tian, Yangchao

    2016-09-01

    This work reports an investigation of the impact of microstructure on the performance of solid oxide fuel cells (SOFC) composed of nickel yttria-stabilized zirconia (Ni YSZ). X-ray nano computed tomography (nano-CT) was used to obtain three-dimensional (3D) models of Ni-YSZ composite anode samples subjected to different thermal cycles. Key parameters, such as triple phase boundary (TPB) density, were calculated using 3D reconstructions. The electrochemical reaction occurring at active-TPB was modeled by the Lattice Boltzmann Method for simulation of multi-component mass transfer in porous anodes. The effect of different electrode geometries on the mass transfer and the electrochemical reaction in anodes was studied by TPB distributions measured by nano CT for samples subjected to different thermal cycles. The concentration polarization and the activation polarization were estimated respectively. The results demonstrate that a combined approach involving nano-CT experiments in conjunction with simulations of gas transport and electrochemical reactions using the Lattice Boltzmann method can be used to better understand the relationship between electrode microstructure and performance of nickel yttria-stabilized zirconia anodes.

  16. Mechanical properties, electrochemical corrosion and in-vitro bioactivity of yttria stabilized zirconia reinforced hydroxyapatite coatings prepared by gas tunnel type plasma spraying.

    Science.gov (United States)

    Yugeswaran, S; Yoganand, C P; Kobayashi, A; Paraskevopoulos, K M; Subramanian, B

    2012-05-01

    Yttria stabilized zirconia reinforced hydroxyapatite coatings were deposited by a gas tunnel type plasma spray torch under optimum spraying conditions. For this purpose, 10, 20 and 30 wt% of yttria stabilized zirconia (YSZ) powders were premixed individually with hydroxyapatite (HA) powder and were used as the feedstocks for the coatings. The effect of YSZ reinforcement on the phase formation and mechanical properties of the coatings such as hardness, adhesive strength and sliding wear rates was examined. The results showed that the reinforcement of YSZ in HA could significantly enhance the hardness and adhesive strength of the coatings. The potentiodynamic polarization and impedance measurements showed that the reinforced coatings exhibited superior corrosion resistance compared to the HA coating in SBF solution. Further the results of the bioactivity test conducted by immersion of coatings in SBF showed that after 10 days of immersion of the obtained coatings with all the above compositions commonly exhibited the onset of bioactive apatite formation except for HA+10%YSZ coating. The cytocompatibility was investigated by culturing the green fluorescent protein (GFP)-labeled marrow stromal cells (MSCs) on the coating surface. The cell culture results revealed that the reinforced coatings have superior cell growth than the pure HA coatings.

  17. A phenomenological study of yttria-stabilized zirconia at 1300 K with the Green-Kubo formulation and equilibrium molecular dynamics

    Science.gov (United States)

    Valadez Huerta, G.; Kelle, A.; Kabelac, S.

    2017-03-01

    In this study, we analyze the transport mechanisms in different yttria-stabilized zirconia compositions as an example for an ionic solid at 1300 K and zero pressure with EMD and the Green-Kubo formulation. As it can be interpreted from the partial and the total correlation functions of the micro fluxes, a certain amount of anions should be given to activate the diffusion of other anions. An incomplete vacancy diffusion favors the coupled effect of heat and diffusion. The heat conduction decreases for higher concentration of vacancies and the optimum of the diffusion is reproducible with this method. We predict a minimum of the thermo-diffusion conductivity at 10 mol% Y2O3. The understanding of the heat and electrical conduction of ionic solids and of the couple effect is essential in systems, where the gradients of different kind of forces are present.

  18. Assessment of the performance of Ni-yttria-stabilized zirconia anodes in anode-supported Solid Oxide Fuel Cells operating on H 2-CO syngas fuels

    Science.gov (United States)

    Ye, Xiao-Feng; Wang, S. R.; Zhou, J.; Zeng, F. R.; Nie, H. W.; Wen, T. L.

    Anode-supported Solid Oxide Fuel Cells (SOFCs) with Ni-yttria-stabilized zirconia (YSZ) anode have been fabricated and studied using H 2-CO syngas fuels. Syngas fuels with different compositions of H 2-CO are supplied and the cell performance is measured at 750 °C. A high CO content has caused carbon deposition and crack formation in the Ni-YSZ anode after long-term operation, even though it is diluted with H 2O and N 2. However, it was found that a Cu-CeO 2 coating on Ni-YSZ can greatly improve the anode stability in syngas by facilitating the water gas shift reaction. The optimized single cell has run in sygas with a composition of 65%H 2-32%CO-3%H 2O for 1050 h without obvious degradation of its performance.

  19. All Metal Organic Deposited High-Tc Superconducting Transition Edge Bolometer on Yttria-Stabilized Zirconia Substrate

    DEFF Research Database (Denmark)

    Mohajeri, Roya; Opata, Yuri Aparecido; Wulff, Anders Christian;

    2016-01-01

    We report on the results of a YBa2Cu3O7−x (YBCO) superconductive transition edge bolometer (TEB) fabricated on a Ce0.9La0.1O2−7 (CLO) buffered single crystalline yttria-stabilized zirconia (YSZ) substrate. Metal organic deposition was used for the fabrication of both the YBCO thin film as well...... as CLO buffer layer, while standard photolithography was applied for TEB preparation. YBCO thin film properties were analysed using scanning electron microscopy (SEM), X-ray diffraction (XRD), AC susceptibility and resistance versus temperature measurements. Optical response of the TEB in terms...... of voltage amplitude and phase was analysed and measured through four-probe technique in a liquid nitrogen cooling system. An increase in voltage amplitude response was observed for the fabricated YBCO/CLO/YSZ bolometer compared to previously reported TEBs with similarly deposited YBCO thin film on a SrTiO3...

  20. Sol-gel dip coating of yttria-stabilized tetragonal zirconia dental ceramic by aluminosilicate nanocomposite as a novel technique to improve the bonding of veneering porcelain.

    Science.gov (United States)

    Madani, Azamsadat; Nakhaei, Mohammadreza; Karami, Parisa; Rajabzadeh, Ghadir; Salehi, Sahar; Bagheri, Hossein

    2016-01-01

    The aim of this in vitro study was to evaluate the effect of silica and aluminosilicate nanocomposite coating of zirconia-based dental ceramic by a sol-gel dip-coating technique on the bond strength of veneering porcelain to the yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in vitro. Thirty Y-TZP blocks (10 mm ×10 mm ×3 mm) were prepared and were assigned to four experimental groups (n=10/group): C, without any further surface treatment as the control group; S, sandblasted using 110 μm alumina powder; Si, silica sol dip coating + calcination; and Si/Al, aluminosilicate sol dip coating + calcination. After preparing Y-TZP samples, a 3 mm thick layer of the recommended porcelain was fired on the coated Y-TZP surface. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis were used to characterize the coating and the nature of the bonding between the coating and zirconia. To examine the zirconia-porcelain bond strength, a microtensile bond strength (μTBS) approach was chosen. FT-IR study showed the formation of silica and aluminosilicate materials. XRD pattern showed the formation of new phases consisting of Si, Al, and Zr in coated samples. SEM showed the formation of a uniform coating on Y-TZP samples. Maximum μTBS values were obtained in aluminosilicate samples, which were significantly increased compared to control and sandblasted groups (P=0.013 and Pporcelain.

  1. Slurry spin coating of thin film yttria stabilized zirconia/gadolinia doped ceria bi-layer electrolytes for solid oxide fuel cells

    Science.gov (United States)

    Kim, Hyun Joong; Kim, Manjin; Neoh, Ke Chean; Han, Gwon Deok; Bae, Kiho; Shin, Jong Mok; Kim, Gyu-Tae; Shim, Joon Hyung

    2016-09-01

    Thin ceramic bi-layered membrane comprising yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is fabricated by the cost-effective slurry spin coating technique, and it is evaluated as an electrolyte of solid oxide fuel cells (SOFCs). It is demonstrated that the slurry spin coating method is capable of fabricating porous ceramic films by adjusting the content of ethyl-cellulose binders in the source slurry. The porous GDC layer deposited by spin coating under an optimal condition functions satisfactorily as a cathode-electrolyte interlayer in the test SOFC stack. A 2-μm-thick electrolyte membrane of the spin-coated YSZ/GDC bi-layer is successfully deposited as a dense and stable film directly on a porous NiO-YSZ anode support without any interlayers, and the SOFC produces power output over 200 mW cm-2 at 600 °C, with an open circuit voltage close to 1 V. Electrochemical impedance spectra analysis is conducted to evaluate the performance of the fuel cell components in relation with the microstructure of the spin-coated layers.

  2. Electrochemical performance and stability of Sr-doped LaMnO3-infiltrated yttria stabilized zirconia oxygen electrode for reversible solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    Hui Fan; Minfang Han

    2014-01-01

    Porous Sr-doped lanthanum manganite–yttria stabilized zirconia (LSM–YSZ) oxygen electrode is prepared by an infiltration process for a reversible solid oxide fuel cell (RSOFC). X-ray diffraction and SEM analysis display that perovskite phase LSM submicro particles are evenly distributed in the porous YSZ matrix. Polarization curves and electrochemical impedance spectra are conducted for the RSOFC at 800 and 850 ?C under both SOFC and SOEC modes. At 850 ?C, the single cell has the maximum power density of*726 mW/cm2 under SOFC mode, and electrolysis voltage of 1.35 V at 1 A/cm2 under SOEC mode. Fuel cell/water electrolysis cycle shows the cell has good performance stability during 6 cycles, which exhibits the LSM–YSZ oxygen electrode has high electrochemical performance and good stability. The results suggest that network-like LSM–YSZ electrode made by infiltration process could be a promising oxygen electrode for high temperature RSOFCs.

  3. Corrosion Behavior of Yttria-Stabilized Zirconia-Coated 9Cr-1Mo Steel in Molten UCl3-LiCl-KCl Salt

    Science.gov (United States)

    Jagadeeswara Rao, Ch.; Venkatesh, P.; Prabhakara Reddy, B.; Ningshen, S.; Mallika, C.; Kamachi Mudali, U.

    2017-02-01

    For the electrorefining step in the pyrochemical reprocessing of spent metallic fuels of future sodium cooled fast breeder reactors, 9Cr-1Mo steel has been proposed as the container material. The electrorefining process is carried out using 5-6 wt.% UCl3 in LiCl-KCl molten salt as the electrolyte at 500 °C under argon atmosphere. In the present study, to protect the container vessel from hot corrosion by the molten salt, 8-9% yttria-stabilized zirconia (YSZ) ceramic coating was deposited on 9Cr-1Mo steel by atmospheric plasma spray process. The hot corrosion behavior of YSZ-coated 9Cr-1Mo steel specimen was investigated in molten UCl3-LiCl-KCl salt at 600 °C for 100-, 500-, 1000- and 2000-h duration. The results revealed that the weight change in the YSZ-coated specimen was insignificant even after exposure to molten salt for 2000 h, and delamination of coating did not occur. SEM examination showed the lamellar morphology of the YSZ coating after the corrosion test with occluded molten salt. The XRD analysis confirmed the presence of tetragonal and cubic phases of ZrO2, without any phase change. Formation of UO2 in some regions of the samples was evident from XRD results.

  4. A simple sol–gel approach to synthesize nanocrystalline 8 mol% yttria stabilized zirconia from metal-chelate precursors: Microstructural evolution and conductivity studies

    Energy Technology Data Exchange (ETDEWEB)

    Bagchi, Biswajoy; Basu, Rajendra Nath, E-mail: ragenbasu54@gmail.com

    2015-10-25

    A facile non alkoxide based sol–gel technique has been used to synthesize homogeneously distributed nanocrystalline 8 mol% yttria stabilized zirconia (YSZ) powder. The two steps of such powder preparation are gelation and thermal decomposition of metal-chelate complex in aqueous solution. Such nano powder was characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscope (FESEM), Fourier transform infra-red spectroscopy (FTIR) and BET surface area analyser. Upon calcinations at 600 °C, well crystallized nano-sized (10–15 nm) YSZ powder is obtained having spherical morphology and reasonably high surface area. The required ionic conductivity (0.107 S/cm) is achieved with 1200 °C sintered samples when measured at 1000 °C in air. - Graphical abstract: A facile non-alkoxide sol–gel route based on metal-EDTA chelate precursor is provided to synthesize dense nanocrystalline YSZ for use as SOFC electrolyte. - Highlights: • Facile one-step non-alkoxide based sol–gel approach. • Nanocrystalline YSZ synthesis from metal-chelate complex. • High ionic conductivity at low sintering temperature.

  5. Material properties of pulsed-laser crystallized Si thin films grown on yttria-stabilized zirconia crystallization-induction layers by two-step irradiation method

    Science.gov (United States)

    Thi Kieu Lien, Mai; Horita, Susumu

    2016-03-01

    Amorphous Si thin films on yttria-stabilized zirconia (YSZ) layers were crystallized widely in solid phase by the two-step method with a pulsed laser, moving the sample stage. The crystalline quality, impurity diffusion, and electrical properties of the crystallized Si films were investigated. It was found that the crystallinity of the Si thin films was improved and their surface was smooth without an incubation layer at the interface, indicating the uniform crystallinity of Si on YSZ. The diffusion of Zr and Y into the Si thin films was as small as or smaller than the order of 1017 atoms/cm3. We evaluated the electrical properties of carrier concentration and Hall mobility of the Si thin films with/without YSZ layers by using the resistivity and AC Hall effect measurements. The temperature and doping concentration dependences were measured for both undoped and P-doped films. It was found that both the undoped and P-doped Si/YSZ/glass films showed higher mobilities and carrier concentrations (and therefore higher conductivities), which indicate a smaller number of defects, than the Si/glass films. This suggested that the Si film crystallized on the YSZ layer is more suitable for application to electronic devices than the Si film on glass.

  6. Effect of tar fractions from coal gasification on nickel-yttria stabilized zirconia and nickel-gadolinium doped ceria solid oxide fuel cell anode materials

    Science.gov (United States)

    Lorente, E.; Berrueco, C.; Millan, M.; Brandon, N. P.

    2013-11-01

    The allowable tar content in gasification syngas is one of the key questions for the exploitation of the full potential of fuel cell concepts with integrated gasification systems. A better understanding of the interaction between tars and the SOFC anodes which leads to carbon formation and deposition is needed in order to design systems where the extent of gas cleaning operations is minimized. Model tar compounds (toluene, benzene, naphthalene) have been used in experimental studies to represent those arising from biomass/coal gasification. However, the use of toluene as a model tar overestimates the negative impact of a real gasification tar on SOFC anode degradation associated with carbon formation. In the present work, the effect of a gasification tar and its distillation fractions on two commercially available fuel cell anodes, Ni/YSZ (yttria stabilized zirconia) and Ni/CGO (gadolinium doped ceria), is reported. A higher impact of the lighter tar fractions was observed, in terms of more carbon formation on the anodes, in comparison with the whole tar sample. The characterization of the recovered tars after contact with the anode materials revealed a shift towards a heavier molecular weight distribution, reinforcing the view that these fractions have reacted on the anode.

  7. Effect of adding urea on performance of Cu/CeO{sub 2}/yttria-stabilized zirconia anodes for solid oxide fuel cells prepared by impregnation method

    Energy Technology Data Exchange (ETDEWEB)

    Li Wenyuan [Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); Lue Zhe, E-mail: lvzhe@hit.edu.c [Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); Zhu Xingbao; Guan Bo; Wei Bo; Guan Chengzhi; Su Wenhui [Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150080 (China)

    2011-02-01

    Anode microstructure has a great influence on the cell performance. The addition of urea into impregnated solution has been proposed to tailor the distribution and/or morphology of Cu when fabricating the Cu-based anodes by impregnation method. While the previous reports demonstrated the single cell performance has not been improved in this route, in this paper, fuel cells with Cu/yttria-stabilized zirconia (YSZ) and Cu-CeO{sub 2}/YSZ anodes were fabricated and evaluated with improved outputs. The microstructure of Cu in anodes appeared significantly different after the addition of urea. The electronic conductivity obtained from the anodes impregnated with adding urea was twice as high as the ones without. Performance of fuel cells increases by 12% while operating on H{sub 2} at 700 {sup o}C upon adding urea. Furthermore, the performance improvement was more prominent when such method was adopted in the fabrication of Cu-CeO{sub 2}/YSZ composite anodes. Cells with Cu-CeO{sub 2}/YSZ composite anodes operating in H{sub 2} at 700 {sup o}C exhibited an increase of cell performance by 37%, from 337 to 462 mW cm{sup -2}, by simply adding urea to the impregnated solution. And the performance enhancement for such fuel cells is also as high as 28% when using CH{sub 4} as fuel.

  8. Failure Behavior of Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings Under Three-Point Bending Test via Acoustic Emission Technique

    Science.gov (United States)

    Wang, L.; Ni, J. X.; Shao, F.; Yang, J. S.; Zhong, X. H.; Zhao, H. Y.; Liu, C. G.; Tao, S. Y.; Wang, Y.; Li, D. Y.

    2017-01-01

    In this paper, the failure behavior of plasma-sprayed yttria-stabilized zirconia thermal barrier coatings fabricated by atmospheric plasma spraying (APS-TBCs) under three-point bending (3PB) test has been characterized via acoustic emission (AE) technique. Linear positioning method has been adopted to monitor dynamic failure process of the APS-TBCs under 3PB test. The investigation results indicate that the variation of AE parameters (AE event counts, amplitudes and AE energy) corresponds well with the change of stress-strain curve of the loading processes. The failure mechanism was analyzed based on the characteristics of AE parameters. The distribution of frequency of crack propagation has been obtained. The AE signals came from two aspects: i.e., plastic deformation of substrates, initiation and propagation of the cracks in the coatings. The AE analysis combined with cross-sectional observation has indicated that many critical cracks initiate at the surface of the top-coat. And some main cracks tend to propagate toward the substrate/bond-coat interface. The actual failure mechanism of the APS-TBCs under 3PB test is attributed to the debonding of metallic coating from the substrates and the propagation of the horizontal crack along the substrate/bond-coat interface under the action of flexural moment.

  9. H 2O chemisorption and H 2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

    Science.gov (United States)

    Gorski, Alexandr; Yurkiv, Vitaliy; Starukhin, Dzmitry; Volpp, Hans-Robert

    The mechanism of H 2O dissociation as well as the adsorption and oxidation reaction of H 2 on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H 2O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H 2 with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H 2 oxidation. Our experiments showed that in both the H 2O/YSZ and the H 2/YSZ + O heterogeneous reaction systems noticeable amounts of H 2O are "dissolved" in the bulk as interstitial hydrogen and hydroxyl species. The experimental H 2O desorption data is used to access the accuracy of the H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H 2 oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H 2/H 2O/YSZ adsorption/desorption and surface reaction kinetics data set is presented.

  10. Thickness determination of large-area films of yttria-stabilized zirconia produced by pulsed laser deposition

    DEFF Research Database (Denmark)

    Pryds, N.; Christensen, Bo Toftmann; Bilde-Sørensen, Jørgen;

    2006-01-01

    Films of yuria-stabilized zirconia (YSZ) on a polished silicon substrate of diameter up to 125 mm have been produced in a large-area pulsed laser deposition (PLD) setup under typical PLD conditions. The film thickness over the full film area has been determined by energy-dispersive Xray spectrome...

  11. Surface roughness and hardness of yttria stabilized zirconia (Y-TZP after 10 years of simulated brushing

    Directory of Open Access Journals (Sweden)

    Lucas Miguel Candido

    Full Text Available Introduction: The Y-TZP zirconia used for prosthetic infrastructure, in some clinical situations, can be exposed to the oral environment. In these situations, a polished surface without changes is extremely important. Objective: The aim of this study was to evaluate the mean roughness (Ra and Vickers hardness of Y-TZP zirconia (Lava™ after simulating ten years of brushing. Material and method: Thirty-six Y-TZP bar-shaped specimens (20mm X 4mm X 1.2mm were divided into three groups: storage in distilled water (DW, n=12, control; brushing with distilled water (BDW, n=12 and brushing with distilled water and fluoride toothpaste (BFT, n=12. Brushing was performed using a brushing machine with a soft-bristled toothbrush, simulating 10 years of brushing (878.400 cycles, 100gf. The mean roughness (Ra in μm and Vickers hardness (VHN of all specimens were measured twice: before and after the experimental treatment, in profilometer and microhardness tester (500gf, 30 seconds, respectively. Data were analyzed using the two-way ANOVA test (α = 0.05. Result: The interaction between groups was not significant for roughness (p = 0.701 nor for hardness (p = 0.928. The final averages for Ra (μm were equal to: DW - 0.63; BDW - 0.64; and, BFT - 0.68. The final averages for Vickers hardness (VHN were: DW - 1301.16; BDW - 1316.60; and, BFT - 1299.58. Conclusion: It was concluded that the brushing with distilled or fluoridated toothpaste was not able to change the roughness and hardness of Y-TZP zirconia used in this study.

  12. Application of the electrophoretic deposition technique for obtaining Yttria-stabilized zirconia tubes; Aplicacao da tecnica de deposicao eletroforetica para a obtencao de tubos ceramicos de zirconia-itria

    Energy Technology Data Exchange (ETDEWEB)

    Caproni, E.; Muccillo, R., E-mail: ecaproni@gmail.com, E-mail: muccillo@usp.br [Centro de Ciencia e Tecnologia de Materiais, Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2012-01-15

    The electrophoretic deposition (EPD) is recognized as the most versatile technique for processing particulate materials, due to low cost, deposition in minutes and forming of pieces with complex geometry shapes. In this work an experimental setup for the simultaneous conformation of 16 ceramic tubes by EPD was built. Bimodal submicron Yttria-stabilized zirconia particles were deposited into graphite electrodes, after suitably adjusting the rheological characteristics of the suspension in isopropanol. After graphite burning and YSZ sintering at 1500 deg C, the ceramic tubes were characterized by X-ray diffraction, scanning probe microscope, impedance spectroscopy and electrical response as a function of oxygen content. Small dense one end-closed ceramic tubes, fully stabilized in the cubic phase, were successfully obtained by the EPD technique, showing the ability of that technique for processing large quantities of tubular solid electrolytes with electrical response to different amounts of oxygen according to the Nernst law (author)

  13. Impact of yttria stabilized zirconia nanoinclusions on the thermal conductivity of n-type Si80Ge20 alloys prepared by spark plasma sintering

    Science.gov (United States)

    Lahwal, Ali; Bhattacharya, S.; He, Jian; Wu, Di; Peterson, A.; Poon, S. J.; Williams, L.; Dehkordi, A. Mehdizadeh; Tritt, T. M.

    2015-04-01

    Nanocomposites have become a new paradigm for thermoelectric research in recent years and have resulted in the reduction of thermal conductivity via the nano-inclusion and grain boundary scattering. In this work, we report the preparation and thermoelectric study of SiGe-yttria stabilized zirconia (YSZ) nanocomposites prepared by Spark Plasma Sintering (SPS). We experimentally investigated the reduction of lattice thermal conductivity (κL) in the temperature range (30-800 K) of n-type Si80Ge20P2 alloys with the incorporation of YSZ nanoparticles (20-40 nm diameter) into the Si-Ge matrix. These samples synthesized by using the SPS technique were found to have densities > 95% of the theoretical density. The thermal conductivity, at both low and high temperatures, was measured by steady state and laser flash techniques, respectively. At room temperature, we observed approximately a 50% reduction in the lattice thermal conductivity as result of adding 10% YSZ by volume to the Si80Ge20P2 host matrix. A phenomenological model developed by Callaway was used to corroborate both the temperature dependence and reduction of κ L over the measured temperature range (30-800 K) of both Si80Ge20P2 and Si80Ge20P2 + YSZ samples. The observed κL is discussed and interpreted in terms of various phonon scattering mechanisms such as alloy disorder, the Umklapp phonon scattering, and boundary scattering. In addition, a contribution from the phonon scattering by YSZ nanoparticles was further included to account for the κL of Si80Ge20P2 + YSZ sample. The theoretical calculations are in reasonably good agreement with the experimental results for both the Si80Ge20P2 and Si80Ge20P2 + YSZ alloys.

  14. Transport properties of water and oxygen in yttria-stabilized zirconia; Transporteigenschaften von Wasser und Sauerstoff in Yttrium-stabilisiertem Zirkoniumdioxid

    Energy Technology Data Exchange (ETDEWEB)

    Pietrowski, Martha Joanna

    2012-12-21

    Oxide materials that adopt the fluorite structure, such as yttria-stabilized zirconia (YSZ), play a central role in electrochemical devices, such as fuel cells and sensors, because of their high ionic conductivity. By virtue of the technological importance of such devices there exists a broad interest in understanding and enhancing mass transport processes in YSZ. In such oxides, not only does transport through the bulk play a critical role; interfaces (internal and external) have an influence, too. The effect of interfaces on the transport properties, however, is not investigated in detail, and remains in many places unclear. In this work two open questions concerning the effect of interfaces on mass transport processes in YSZ are addressed: The first issue is the phenomenon of protonic conductivity observed at low temperatures for nanocrystalline YSZ in wet atmospheres. This protonic conductivity was attributed to the high density of interfaces (grain boundaries) caused by the nanostructure, in which protonic species can be mobile. Through isotope exchange experiments with subsequent Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) the presence of hydrogen in nano-YSZ was confirmed. Questions as to which hydrogen-containing species are present and which transport path is taken in nanocrystalline YSZ were examined by means of in-situ of near-infrared (NIR) spectroscopy. The results indicate that water is adsorbed on internal surfaces, such as pores and micro-cracks. Microscopic analysis of nanocrystalline YSZ showed first indications of nanopores. The second issue concerned transport across the solidgas interface, that is the surface. To this end, oxygen isotope exchange experiments were performed on single crystal samples of yttria-stabilised zirconia under wet and dry conditions as function of oxygen partial pressure pO{sub 2} and water partial pressure pH{sub 2}O with subsequent determination of the oxygen isotope profiles by ToF-SIMS. As expected, the

  15. The Evolution of Solid Oxide Fuel Cell Nickel-Yttria Stabilized Zirconia Anodes Studied Using Electrochemical and Three-Dimensional Microstructural Characterizations

    Science.gov (United States)

    Kennouche, David O.

    This thesis focuses on Solid Oxide Fuel Cells (SOFCs). The 21st century will see major changes in the way energy is produced, stored, and used around the world. SOFCs, which provide an efficient, scalable, and low-pollution alternative method for electricity generation, are expected to play an important role. SOFCs can also be operated in electrolysis mode for energy storage, important since health and economic reasons are causing a shift towards intermittent renewable energy resources. However, multiple limitations mainly linked to cost and durability have prevented the expansion of this technology to mass markets. This work focuses on the Nickel - Yttria Stabilized Zirconia (Ni-YSZ) anode that is widely used in SOFCs. Coarsening of Ni in the Ni-YSZ anode has been widely cited as a primary cause of long-term SOFC degradation. While there have been numerous studies of Ni coarsening reported, these have typically only tracked the evolution of Ni particle size, not the entire microstructure, and have typically not been correlated directly with electrochemical performance. In this thesis, the advanced tomography techniques Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) tomography and Trans- mission X-ray Microscopy (TXM) have been utilized to enable insight into the evolution of Ni-YSZ structure and how it relates to performance degradation. Extensive anode aging studies were done for relatively short times using temperatures higher than in normal SOFC operation in order to accelerate microstructural evolution. In addition the microstructure changes were correlated with changes in anode polarization resistance. While most of the measurements were done by comparing different anodes aged under different conditions, the first example of a "pseudo in situ" measurement where the same anode was 3D imaged repeatedly with intervening aging steps, was also demonstrated. A microstructural evolution model that focuses on the active three-phase boundary density was

  16. Investigations in the mechanism of carbothermal reduction of yttria stabilized zirconia for ultra-high temperature ceramics application and its influence on yttria contained in it

    Science.gov (United States)

    Sondhi, Anchal

    Zirconium carbide (ZrC) is a high modulus ceramic with an ultra-high melting temperature and, consequently, is capable of withstanding extreme environments. Carbon-carbon composites (CCCs) are important structural materials in current commercial and future hypersonic aircraft; however, these materials may be susceptible to degradation when exposed to elevated temperatures during extreme velocities. At speeds of exceeding Mach 5, intense heating of leading edges of the aircraft triggers rapid oxidation of carbon in CCCs resulting in degradation of the structure and probable failure. Environmental/thermal barrier coatings (EBC/TBC) are employed to protect airfoil structures from extreme conditions. Yttria stabilized zirconia (YSZ) is a well-known EBC/TBC material currently used to protect metallic turbine blades and other aerospace structures. In this work, 3 mol% YSZ has been studied as a potential EBC/TBC on CCCs. However, YSZ is an oxygen conductor and may not sufficiently slow the oxidation of the underlying CCC. Under appropriate conditions, ZrC can form at the interface between CCC and YSZ. Because ZrC is a poor oxygen ion conductor in addition to its stability at high temperatures, it can reduce the oxygen transport to the CCC and thus increase the service lifetime of the structure. This dissertation investigates the thermodynamics and kinetics of the YSZ/ZrC/CCC system and the resulting structural changes across multiple size scales. A series of experiments were conducted to understand the mechanisms and species involved in the carbothermal reduction of ZrO2 to form ZrC. 3 mol% YSZ and graphite powders were uniaxially pressed into pellets and reacted in a graphite (C) furnace. Rietveld x-ray diffraction phase quantification determined that greater fractions of ZrC were formed when carbon was the majority mobile species. These results were validated by modeling the process thermochemically and were confirmed with additional experiments. Measurements were

  17. Cationic hetero diffusion and mechanical properties of yttria-stabilized zirconia: influence of irradiation; Heterodiffusion cationique et proprietes mecaniques de la zircone stabilisee a l'oxyde d'yttrium: influence de l'irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Menvie Bekale, V

    2007-12-15

    Cubic yttria-stabilized zirconia (YSZ) is a promising material as target for the transmutation of radioactive waste. In this context, the present work is dedicated to the study of the atomic transport and the mechanical properties of this ceramic, as well as the influence of irradiation on these properties. The preliminary step concerns the synthesis of YSZ cubic zirconia ceramic undoped and doped with rare earths to form homogeneous Ce-YSZ or Gd-YSZ solid solutions with the highest density. The diffusion experiments of Ce and Gd in YSZ or Ce-YSZ were performed in air from 900 to 1400 C, and the depth profiles were established by SIMS. The bulk diffusion decreases when the ionic radius of diffusing element increases. The comparison with literature data of activation energies for bulk diffusion suggests that the cationic diffusion occurs via a vacancy mechanism. The diffusion results of Ce in YSZ irradiated with 4 or 20 MeV Au ions show a bulk diffusion slowing-down at 1000 and 1100 C when the radiation damage becomes important (30 dpa). The mechanical properties of YSZ ceramics irradiated with 944 MeV Pb ions and non irradiated samples were studied by Vickers micro indentation and Berkovitch nano indentation techniques. The hardness of the material increases when the average grain size decreases. Furthermore, the hardness and the toughness increase with irradiation fluence owing to the occurrence of compressive residual stresses in the irradiated area. (author)

  18. Shear Bond Strengths between Three Different Yttria-Stabilized Zirconia Dental Materials and Veneering Ceramic and Their Susceptibility to Autoclave Induced Low-Temperature Degradation

    Directory of Open Access Journals (Sweden)

    Manoti Sehgal

    2016-01-01

    Full Text Available A study was undertaken to evaluate the effect of artificial aging through steam and thermal treatment as influencing the shear bond strength between three different commercially available zirconia core materials, namely, Upcera, Ziecon, and Cercon, layered with VITA VM9 veneering ceramic using Universal Testing Machine. The mode of failure between zirconia and ceramic was further analyzed as adhesive, cohesive, or mixed using stereomicroscope. X-ray diffraction and SEM (scanning electron microscope analysis were done to estimate the phase transformation (m-phase fraction and surface grain size of zirconia particles, respectively. The purpose of this study was to simulate the clinical environment by artificial aging through steam and thermal treatment so as the clinical function and nature of the bond between zirconia and veneering material as in a clinical trial of 15 years could be evaluated.

  19. Shear Bond Strengths between Three Different Yttria-Stabilized Zirconia Dental Materials and Veneering Ceramic and Their Susceptibility to Autoclave Induced Low-Temperature Degradation.

    Science.gov (United States)

    Sehgal, Manoti; Bhargava, Akshay; Gupta, Sharad; Gupta, Prateek

    2016-01-01

    A study was undertaken to evaluate the effect of artificial aging through steam and thermal treatment as influencing the shear bond strength between three different commercially available zirconia core materials, namely, Upcera, Ziecon, and Cercon, layered with VITA VM9 veneering ceramic using Universal Testing Machine. The mode of failure between zirconia and ceramic was further analyzed as adhesive, cohesive, or mixed using stereomicroscope. X-ray diffraction and SEM (scanning electron microscope) analysis were done to estimate the phase transformation (m-phase fraction) and surface grain size of zirconia particles, respectively. The purpose of this study was to simulate the clinical environment by artificial aging through steam and thermal treatment so as the clinical function and nature of the bond between zirconia and veneering material as in a clinical trial of 15 years could be evaluated.

  20. Stainless steel-supported solid oxide fuel cell with La0.2Sr0.8Ti0.9Ni0.1O3-δ/yttria-stabilized zirconia composite anode

    Science.gov (United States)

    Dayaghi, Amir Masoud; Kim, Kun Joong; Kim, Sunwoong; Park, Juahn; Kim, Sun Jae; Park, Byung Hyun; Choi, Gyeong Man

    2016-08-01

    A metal-supported solid oxide fuel cell (MS-SOFC) is fabricated by co-firing stainless steel (STS) support with a new reduction-resistant oxide-anode and yttria-stabilized zirconia electrolyte. La and Ni co-doped SrTiO3 (La0.2Sr0.8Ti0.9Ni0.1O3-δ, LSTN) which shows Ni exsolution capability is composited with Y0.16Zr0.84O2-δ (YSZ) electrolyte to form a new LSTN-YSZ anode. A cermet layer composed of STS and YSZ (STS-YSZ) is inserted between a porous STS support and a new LSTN-YSZ composite anode for stable contact. With La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode and Ce0.8Gd0.2O2-δ (GDC) interlayer coated on top of co-fired half-cell, YSZ/LSTN-YSZ/STS-YSZ/STS, a newly designed and fabricated cell achieved maximum power density of 185 mW cm-2 at 650 °C. This power density is an improvement over many conventional co-fired MS-SOFCs that use a Ni-cermet anode.

  1. Effect of Co{sub 3}O{sub 4} content on sintering and microstructure of 4% mol yttria stabilized zirconia ceramics; Efeito do teor de Co{sub 3}O{sub 4} na sinterizacao e microestrutura de ceramicas de zirconia 4% mol de itria

    Energy Technology Data Exchange (ETDEWEB)

    Grilo, J.P.F.; Neto, P.P.B.; Souza, G.L.; Macedo, D.A.; Paskocimas, C.A.; Nascimento, R.M., E-mail: grilo.jpf@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2011-07-01

    In attempt to reduce the sintering temperature of yttria stabilized zirconia (4% mol, 4YSZ), Co{sub 3}O{sub 4} powders obtained by polymeric precursor method were used as sintering aids. Commercial 4YSZ powder and Co{sub 3}O{sub 4} calcined at 800 deg C for 2 h were characterized by XRD and SEM. Sintering behaviour of ceramics as a function of Co{sub 3}O{sub 4} content (between 0.5 and 4 wt.%) was investigated by dilatometry. Based on dilatometric analysis, ceramics were sintered between 1200 and 1400 deg C for 2 h in air and then characterized using different techniques. XRD results exhibit the attainment of monophasic Co{sub 3}O{sub 4} and the most part of tetragonal zirconia in the sintered ceramics. (author)

  2. Effect of impregnation of La0.85Sr0.15MnO3/Yttria Stabilized Zirconia Solid Oxide Fuel Cell cathodes with La0.85Sr0.15MnO3 or Al2O3 nano-particles

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent; Wandel, Marie; Liu, Yi-Lin;

    2010-01-01

    Strontium substituted lanthanum manganite and yttria stabilized zirconia solid oxide fuel cell composite electrodes were impregnated with nano-particles of strontium substituted lanthanum manganite or alumina. A clear positive effect was observed on low performing electrodes and on good performin...

  3. Thermal radiative properties of (La{sub 1−x}Sr{sub x})MnO{sub 3−δ} thin films fabricated on yttria-stabilized zirconia single-crystal substrate by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shiota, Tadashi, E-mail: tshiota@ceram.titech.ac.jp [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Sato, Kenichi; Cross, Jeffrey S. [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Wakiya, Naoki [Department of Electronics and Material Science, Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Tachikawa, Sumitaka; Ohnishi, Akira [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210 (Japan); Sakurai, Osamu; Shinozaki, Kazuo [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

    2015-10-30

    For application as a variable thermal emittance material in a recently-developed thermal control system for spacecraft, (La{sub 1−x}Sr{sub x})MnO{sub 3−δ} (LSMO) thin films with thicknesses of 1.2 μm, 2.5 μm, and 4.3 μm were fabricated on yttria-stabilized zirconia (100) substrates by a pulsed laser deposition and ex-situ annealing at 1123 K in air. All the films were dense and their surface roughness was much smaller than the thermal infrared (IR) wavelength. The films had (100) and (110)-preferred orientations, and the thicker films showed more preferable growth along the (100) orientation. Temperature–magnetization curves revealed that the LSMO films exhibited a metal–insulator transition near room temperature. The thermal emittance of the films estimated from IR reflectance spectra and black body radiation spectra exhibited large non-linearity near room temperature owing to the phase transition. The change in thermal emittance of the LSMO films that were more than 2.5 μm thick was comparable with that of the Ca-doped LSMO ceramic tiles already used as variable thermal emittance materials. Thus, this result clearly demonstrates that LSMO thin films with thickness of 2.5 μm can work as variable thermal emittance materials in the thermal control system for spacecraft. - Highlights: • High-quality La{sub 1−x}Sr{sub x}MnO{sub 3−δ}thin films were fabricated by pulsed laser deposition. • The films exhibited a metal–insulator transition near room temperature. • Their thermal emittance was dramatically changed owing to the phase transition. • More than 2.5-μm-thick films were suitable for a spacecraft thermal control system.

  4. Electrode properties of Sr-doped LaMnO{sub 3} on yttria-stabilized zirconia. Part 2. Electrode kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Van Heuveln, F.H.; Bouwmeester, H.J.M.

    1996-04-01

    A series of six cathodes Sr{sub 0.15}La{sub 0.85}MnO{sub 3} (SLM) on stabilised zirconia (YSZ) with different morphology of the electrode/electrolyte interface were characterised by ac-impedance and dc-polarisation measurements. It is found that the electrode kinetics at elevated temperature (945C) are governed by two serial processes. An activation process can be identified to occur at high cathodic over potential, whereas a transport process competes with charge transfer at comparatively low overpotential. Attention is drawn to the profound change in the electrocatalytic properties of SLM upon current passage, and its influence in elucidation of the interfacial kinetics. 8 figs., 5 tabs., 11 refs.

  5. Electrode properties of Sr-doped LaMnO{sub 3} on yttria-stabilized zirconia. 1: Three-phase boundary area

    Energy Technology Data Exchange (ETDEWEB)

    Heuveln, F.H. van; Berkel, F.P.F. van [Netherlands Energy Research Foundation ECN, Petten (Netherlands); Bouwmeester, H.J.M. [Univ. of Twente, Enschede (Netherlands). Dept of Chemical Technology

    1997-01-01

    The interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells, Sr{sub x}La{sub 1{minus}x}MnO{sub 3} (SLM), was investigated with respect to its electrochemical performance. The interface microstructure was characterized by grain size and coverage of SLM on the electrolyte surface. Variation of the grain size was obtained by using three different sintering temperatures, whereas variation of the coverage was obtained by using two powders with a different morphology. This resulted in a set of six cathode/electrolyte samples with different combinations of grain size and SLM coverage at the interface. The cathode overpotential, as a measure for the electrochemical performance, could not be related to the length of the three-phase boundary. Based on the constriction resistance occurring in the electrolyte a model was developed which provides an estimate for the width of the active three-phase boundary zone. This zone is most likely to extend outside the cathode particle across the zirconia surface. The width calculated in this way was found to vary in the range of 0.03 to 0.07 {micro}m for the different electrode microstructures. It is argued that the actual values may be smaller by one or two orders of magnitude.

  6. Electrode properties of Sr-doped LaMnO{sub 3} on yttria-stabilized zirconia. Part 1. Three-phase boundary area

    Energy Technology Data Exchange (ETDEWEB)

    Van Heuveln, F.H.; Bouwmeester, H.J.M.; Van Berkel, F.P.F.

    1996-04-01

    The interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells (SOFC`s), Sr{sub x}La{sub 1-x}MnO{sub 3} (SLM), was investigated with respect to its electrochemical performance. The interface microstructure was characterised by the grain size and the coverage of SLM on the electrolyte surface. Variation of the grain size was obtained by using three different sintering temperatures whereas variation of the coverage was obtained by using two powders with a different morphology. This resulted in a set of six cathode/electrolyte samples with different combinations of grain size and SLM coverage at the interface. The cathode overpotential, as a measure for the electrochemical performance, could not be related to the length of the three-phase boundary (tpb). Based on the constriction resistance occurring in the electrolyte a model was developed which provides an estimate for the width of the active tpb zone. This zone is most likely to extend outside the cathode particle across the zirconia surface. The width calculated in this way was found to vary in the range of 0.03-0.07{mu}m for the different electrode micro structures. It is argued that the actual values may be smaller by an order of magnitude. 14 figs., 5 tabs., 12 refs.

  7. In-flight alloying of nanocrystalline yttria-stabilized zirconia using suspension spray to produce ultra-low thermal conductivity thermal barriers.

    Energy Technology Data Exchange (ETDEWEB)

    VanEvery, K.; Krane, M.J.M.; Trice, R.W.; Porter, W.; Wang, H.; Besser, M.; Sordelet, D.; Ilavsky, J.; Almer, J. (X-Ray Science Division); (Purdue University); (Oak Ridge national Laboratory); (Ames Laboratory)

    2011-11-01

    Previous researchers have shown that it is possible to combine rare-earth oxides with the standard thermal barrier coating material (4.5 mol% Y{sub 2}O{sub 3}-ZrO{sub 2} or YSZ) to form ultra-low thermal conductivity coatings using a standard powder manufacturing route. A similar approach to making low thermal conductivity coatings by adding rare-earth oxides is discussed presently, but a different manufacturing route was used. This route involved dissolving hydrated ytterbium and neodymium nitrates into a suspension of 80 nm diameter 4.5 mol% YSZ powder and ethanol. Suspension plasma spray was then used to create coatings in which the YSZ powders were alloyed with rare-earth elements while the plasma transported the melted powders to the substrate. Mass spectrometry measurements showed a YSZ coating composition, in mol%, of ZrO{sub 2}-4.4 Y{sub 2}O{sub 3}-1.4 Nd{sub 2}O{sub 3}-1.3 Yb{sub 2}O{sub 3}. The amount of Yb{sup 3+} and Nd{sup 3+} ions in the final coating was {approx}50% of that added to the starting suspension. Wide-angle X-ray diffraction revealed a cubic ZrO{sub 2} phase, consistent with the incorporation of more stabilizer into the zirconia crystal structure. The total porosity in the coatings was {approx}35-36%, with a bulk density of 3.94 g/cm{sup 3}. Small-angle X-ray scattering measured an apparent void specific surface area of {approx}2.68 m{sup 2}/cm{sup 3} for the alloyed coating and {approx}3.19 m{sup 2}/cm{sup 3} for the baseline coating. Thermal conductivity (k{sub th}) of the alloyed coating was {approx}0.8 W/m/K at 800 C, as compared with {approx}1.5 W/m/K at 800 C for the YSZ-only baseline coating. After 50 h at 1200 C, k{sub th} increased to {approx}1.1 W/m/K at 800 C for the alloyed samples, with an associated decrease in the apparent void specific surface area to {approx}1.55 m{sup 2}/cm{sup 3}.

  8. In-Flight Alloying of Nanocrystalline Yttria-Stabilized Zirconia Using Suspension spray to Produce Ultra-Low Thermal Conductivity Thermal Barriers

    Energy Technology Data Exchange (ETDEWEB)

    Van Every, Kent [Purdue University; Krane, Matthew [Purdue University; Trice, Rodney [Purdue University; Porter, Wallace D [ORNL; Wang, Hsin [ORNL; Besser, Matthew [Ames Laboratory; Sordelet, Daniel [Ames Laboratory; Ilavsky, Dr. Jan [Argonne National Laboratory (ANL); Almer, Jon [Argonne National Laboratory (ANL)

    2011-01-01

    Previous researchers have shown that it is possible to combine rare-earth oxides with the standard thermal barrier coating material (4.5 mol% Y{sub 2}O{sub 3}-ZrO{sub 2} or YSZ) to form ultra-low thermal conductivity coatings using a standard powder manufacturing route. A similar approach to making low thermal conductivity coatings by adding rare-earth oxides is discussed presently, but a different manufacturing route was used. This route involved dissolving hydrated ytterbium and neodymium nitrates into a suspension of 80 nm diameter 4.5 mol% YSZ powder and ethanol. Suspension plasma spray was then used to create coatings in which the YSZ powders were alloyed with rare-earth elements while the plasma transported the melted powders to the substrate. Mass spectrometry measurements showed a YSZ coating composition, in mol%, of ZrO{sub 2}-4.4 Y{sub 2}O{sub 3}-1.4 Nd{sub 2}O{sub 3}-1.3 Yb{sub 2}O{sub 3}. The amount of Yb{sup 3+} and Nd{sup 3+} ions in the final coating was {approx}50% of that added to the starting suspension. Wide-angle X-ray diffraction revealed a cubic ZrO{sub 2} phase, consistent with the incorporation of more stabilizer into the zirconia crystal structure. The total porosity in the coatings was {approx}35-36%, with a bulk density of 3.94 g/cm{sup 3}. Small-angle X-ray scattering measured an apparent void specific surface area of {approx}2.68 m{sup 2}/cm{sup 3} for the alloyed coating and {approx}3.19 m{sup 2}/cm{sup 3} for the baseline coating. Thermal conductivity (k{sub th}) of the alloyed coating was {approx}0.8 W/m/K at 800 C, as compared with {approx}1.5 W/m/K at 800 C for the YSZ-only baseline coating. After 50 h at 1200 C, kth increased to {approx}1.1 W/m/K at 800 C for the alloyed samples, with an associated decrease in the apparent void specific surface area to {approx}1.55 m{sup 2}/cm{sup 3}.

  9. Epitaxial growth of YBa2Cu3O7−x films on Ce0.9La0.1O2−y buffered yttria-stabilized zirconia substrates by an all-chemical-solution route

    DEFF Research Database (Denmark)

    Yue, Zhao; Wu, Wei; Tang, Xiao;

    2014-01-01

    In view of high rate fabrication of coated conductors at low-cost, YBa2Cu3O7 (YBCO) films on Ce0.9La0.1O2−y buffered yttria-stabilized zirconia substrates were deposited by means of a novel low-fluorine metal–organic solution route. A high critical current density of 3 MA cm−2 (77 K, self field......) was achieved on such an all-chemical derived configuration. Structural characterization showed that the enhanced superconductivity performance of the YBCO films is mainly related to the defects induced by the interface....

  10. Influence of core design, production technique, and material selection on fracture behavior of yttria-stabilized tetragonal zirconia polycrystal fixed dental prostheses produced using different multilayer techniques: split-file, over-pressing, and manually built-up veneers

    Directory of Open Access Journals (Sweden)

    Mahmood DJH

    2016-02-01

    Full Text Available Deyar Jallal Hadi Mahmood, Ewa H Linderoth, Ann Wennerberg, Per Vult Von Steyern Department of Prosthetic Dentistry, Faculty of Odontology, Malmö University, Malmö, Sweden Aim: To investigate and compare the fracture strength and fracture mode in eleven groups of currently, the most commonly used multilayer three-unit all-ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP fixed dental prostheses (FDPs with respect to the choice of core material, veneering material area, manufacturing technique, design of connectors, and radii of curvature of FDP cores. Materials and methods: A total of 110 three-unit Y-TZP FDP cores with one intermediate pontic were made. The FDP cores in groups 1–7 were made with a split-file design, veneered with manually built-up porcelain, computer-aided design-on veneers, and over-pressed veneers. Groups 8–11 consisted of FDPs with a state-of-the-art design, veneered with manually built-up porcelain. All the FDP cores were subjected to simulated aging and finally loaded to fracture. Results: There was a significant difference (P<0.05 between the core designs, but not between the different types of Y-TZP materials. The split-file designs with VITABLOCS® (1,806±165 N and e.max® ZirPress (1,854±115 N and the state-of-the-art design with VITA VM® 9 (1,849±150 N demonstrated the highest mean fracture values. Conclusion: The shape of a split-file designed all-ceramic reconstruction calls for a different dimension protocol, compared to traditionally shaped ones, as the split-file design leads to sharp approximal indentations acting as fractural impressions, thus decreasing the overall strength. The design of a framework is a crucial factor for the load bearing capacity of an all-ceramic FDP. The state-of-the-art design is preferable since the split-file designed cores call for a cross-sectional connector area at least 42% larger, to have the same load bearing capacity as the state-of-the-art designed

  11. Measurement and Calculation of Electrochemical Potentials in Hydrogenated High Temperature Water, including an Evaluation of the Yttria-Stabilized Zirconia/Iron-Iron Oxide (Fe/Fe3O4) Probe as Reference Electrode

    Energy Technology Data Exchange (ETDEWEB)

    Steven A. Attanasio; David S. Morton; Mark A. Ando

    2001-10-22

    The importance of knowing the electrochemical corrosion potential (ECP, also referred to as E{sub con}) of nickel-base alloys in hydrogenated water is related to the need to understand the effects of dissolved (i.e., aqueous) hydrogen concentration ([H{sub 2}]) on primary water stress corrosion cracking (PWSCC). Also, the use of a reference electrode (RE) can improve test quality by heightening the ability to detect instances of out-of-specification or unexpected chemistry. Three methods are used to measure and calculate the ECP of nickel-based alloys in hydrogenated water containing {approx} 1 to 150 scc/kg H{sub 2} (0.1 to 13.6 ppm H{sub 2}) at 260 to 360 C. The three methods are referred to as the specimen/component method, the platinum (Pt) method, and the yttria-stabilized zirconia/iron-iron oxide (YSZ/Fe-Fe{sub 3}O{sub 4}) RE method. The specimen/component method relies upon the assumption that the specimen or component behaves as a hydrogen electrode, and its E{sub corr} is calculated using the Nernst equation. The present work shows that this method is valid for aqueous H{sub 2} levels {ge} {approx} 5 to 10 scc/kg H{sub 2}. The Pt method uses a voltage measurement between the specimen or component and a Pt electrode, with the Pt assumed to behave as a hydrogen electrode; this method is valid as long as the aqueous H{sub 2}level is known. The YSZ/Fe-Fe{sub 3}O{sub 4}, which represents a relatively new approach for measuring E{sub corr} in this environment, can be used even if the aqueous H{sub 2} level is unknown. The electrochemical performance of the YSZ/Fe-Fe{sub 3}O{sub 4} probe supports its viability as a RE for use in high temperature hydrogenated water. Recent design modifications incorporating a teflon sealant have improved the durability of this RE (however, some of the REs do still fail prematurely due to water in-leakage). The Pt method is judged to represent the best overall approach, though there are cases where the other methods are superior

  12. Effect of Fe{sub 2}O{sub 3} addition in Yttria-stabilized zirconia properties; Efeito da adicao de Fe{sub 2}O{sub 3} nas propriedades da zirconia estabilizada com itria

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Pedro de Freitas Castro; Elias, Carlos Nelson; Santos, Heraldo Elias Salomao dos, E-mail: elias@ime.eb.br [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Engenharia Mecanica e de Materiais. Laboratorio de Biomateriais

    2017-04-15

    The zirconium oxide (ZrO{sub 2}) polycrystalline partially stabilized by yttrium oxide (Y{sub 2}O{sub 3}) at 3mol%, 3Y-TZP, has its use been increased as a biomaterial. However, as dental prosthetics, its indication is still limited because of its white color and high opacity. Seeking improvements regarding aesthetics without compromising its functional performance, oxides such as iron oxide (Fe{sub 2}O{sub 3}) has been added to the microstructure of zirconia in order to provide a yellow-brownish color similar to natural teeth. This study evaluated the effect of adding Fe{sub 2}O{sub 3} on the microstructure and mechanical and optical properties of 3Y-TZP. Five groups were investigated containing different concentrations of Fe{sub 2}O{sub 3}. Firstly, a chemical characterization of each group was carried out through X-ray fluorescence test (XRF). Microstructural characterization was performed by density and average grain size measurements. Mechanical properties were evaluated by performing hardness and four points flexural strength tests. Quantitative analysis of phase transformation was done using the Rietveld method, for each group submitted to the test of X-ray diffraction (XRD). Fractography by SEM analysis were also made on the fracture surface of the samples from tensile test. The results showed that the Fe{sub 2}O{sub 3} addition influenced the phase transformation process, and proportionally increased the samples hardness and flexural strength when their concentrations varied from 0.02% to 0.17% of the total weight. Above this range, the samples showed losses in their mechanical performance. The Fe{sub 2}O{sub 3} additions showed no significant changes in the density and average grain size of 3Y-TZP. (author)

  13. An X-Ray Diffraction Investigation of alpha-Al2O2 Addition to Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coatings Subject to Destabilizing Vanadium Pentoxide (V2O5) Exposure

    Science.gov (United States)

    1993-09-01

    Stabilized Zirconia TZP - Tetragonal Stabilized Zirconia 6 The effect of ’alloying’ ceramic particles or fibers are clearly evident. The fracture toughness...TA!RL OF CONIMn3S I. INTRO.DUCTION . .. . . . 1 11. BACMWrJD .................... 2 A. CRYSTALLOGRAPHY OF ZIRCONIA .... ............ 2 1. Cubic ...7 1. ZrO2 -Y203 Phase Diagram ......... .......... 7 a. Monoclinic - Tetragonal Transformation 9 b. Cubic

  14. Aplicação da técnica de deposição eletroforética para a obtenção de tubos cerâmicos de zircônia-ítria Application of the electrophoretic deposition technique for obtaining yttria-stabilized zirconia tubes

    Directory of Open Access Journals (Sweden)

    E. Caproni

    2012-03-01

    Full Text Available A técnica de deposição eletroforética (EPD é reconhecida como a mais versátil para o processamento de materiais particulados devido ao seu baixo custo, à deposição em minutos e à conformação de corpos cerâmicos com geometria complexa. Neste trabalho foi feita uma montagem experimental que permite a conformação simultânea de 16 tubos cerâmicos por EPD. Partículas micrométricas de zircônia:ítria foram depositadas, após ajustes nas características reológicas da suspensão em isopropanol, em eletrodo de grafita na forma de tubo. Os tubos cerâmicos, após sinterização a 1500 °C, foram caracterizados por difração de raios X, microscopia de varredura por sonda, espectroscopia de impedância e resposta elétrica em função do teor de oxigênio. A técnica de EPD mostrou-se adequada para obtenção de tubos cerâmicos densos totalmente estabilizados na fase cúbica e resposta elétrica a diferentes quantidades de oxigênio de acordo com a lei de Nernst.The electrophoretic deposition (EPD is recognized as the most versatile technique for processing particulate materials, due to low cost, deposition in minutes and forming of pieces with complex geometry shapes. In this work an experimental setup for the simultaneous conformation of 16 ceramic tubes by EPD was built. Bimodal submicron yttria-stabilized zirconia particles were deposited into graphite electrodes, after suitably adjusting the rheological characteristics of the suspension in isopropanol. After graphite burning and YSZ sintering at 1500 °C, the ceramic tubes were characterized by X-ray diffraction, scanning probe microscope, impedance spectroscopy and electrical response as a function of oxygen content. Small dense one end-closed ceramic tubes, fully stabilized in the cubic phase, were successfully obtained by the EPD technique, showing the ability of that technique for processing large quantities of tubular solid electrolytes with electrical response to different

  15. Effect of Time and Temperature on Transformation Toughened Zirconias.

    Science.gov (United States)

    1987-06-01

    TTZ) and tetragonal airconia polycrystal ( TZP ), as well as sirconla toughened alumina (ZTA), among others. Zirconia based materials are of interest due... zirconia case, two ftctors that affect the analysis are the difficulty in resolving the tetragonal (101) and cubic (111) peaks when copper radiation is...The materials were magnesia stabilized transforma- tion toughened zirconia , yttria stabilized tetragonal zirconia polycrystal, and zirconia toughened

  16. Properties and microstructure of nano-powder 3 mol% yttria stabilized tetragonal zirconia polycrystal as dental materials%牙科纳米材料摩尔分数为3%氧化钇稳定的四方多晶氧化锆性能及其微观结构

    Institute of Scientific and Technical Information of China (English)

    李国华; 龚振宇; 陈吉华

    2009-01-01

    背景:在临床应用中,全瓷修复可解决以往材料的美观与安全等方面的问题而被越来越广泛的接受,尤其是高强度高韧性的氧化锆全瓷材料倍受关注.目的:分析摩尔分数为3%氧化钇稳定的四方多晶氧化锆(3Y-TZP)的烧结性能、力学性能及微观结构.设计、时间及地点:材料学表征,观察实验,于2007-02/2009-05在解放军第四军医大学口腔医学院修复实验室设计实施完成.材料:纳米3Y-TZP粉体(粒度约50 nm)由上海双鼎纳米材料有限公司提供.方法:纳米3Y-TZP粉末与浓度7%聚乙烯醇混合,搅拌均匀后造粒,双向干压成型,制备圆盘及长条状试件,常压烧结.其中圆形试样用于烧结性能测试,长条形试样用于力学性能及微观结构测试.主要观察指标:Archimedes法测试烧结性能,并检测三点抗弯强度、断裂韧性;扫描电镜观察断面形貌;X射线衍射分析晶相组成,比较表面与断面的四方相含量.结果:纳米3Y-TZP在1 500℃烧成,结构致密,三点抗弯强度(921.7±44.2)Mpa;断裂韧性(10.2±1.6)Mpa·m~(1/2).微观形貌示烧结后结构均匀致密,缺陷少,晶粒细小,粒径约0.3μm.X射线衍射分析材料表面为四方相,无单斜相衍射峰;断面四方相81%,单斜相19%.结论:纳米3Y-TZP材料低温烧结,颜色美观,微观结构致密均匀,强韧性好,适宜做牙科全瓷材料.%BACKGROUND: In clinical application, all-ceramic restorations have been widely used because of favorable cosmetic effect and safety, especially zirconia all-ceramic materials with high intensity and toughness. OBJECTIVE: To analyze the sintering and mechanical properties and microstructure of nano-powder 3 mol % yttria stabilized tetragonal zirconia polycrystal (3Y-TZP). DESIGN, TIME AND SETTING: Material characteristics observation. The experiment was performed at the Laboratory of Prosthodontics, Hospital of Stomatology, Fourth Military Medical University of Chinese PLA from February

  17. Fast reactor irradiation effects on fracture toughness of Si3N4 in comparison with MgAl2O4 and yttria stabilized ZrO2

    Science.gov (United States)

    Tada, K.; Watanabe, M.; Tachi, Y.; Kurishita, H.; Nagata, S.; Shikama, T.

    2016-04-01

    Fracture toughness of silicon nitride (Si3N4), magnesia-alumina spinel (MgAl2O4) and yttria stabilized zirconia (8 mol%Y2O3-ZrO2) was evaluated by the Vickers-indentation technique after the fast reactor irradiation up to 55 dpa (displacement per atom) at about 700 °C in the Joyo. The change of the fracture toughness by the irradiation was correlated with nanostructural evolution by the irradiation, which was examined by transmission electron microscopy. The observed degradation of fracture toughness in Si3N4 is thought to be due to the relatively high density of small-sized of the irradiation induced defects, which should be resulted from a large amount of transmutation gases of hydrogen and helium. Observed improvement of fracture toughness in MgAl2O4 was due to the blocking of crack propagation by the antiphase boundaries. The radiation effects affected the fracture toughness of yttria stabilized zirconia at 55 dpa, suggesting that the generated high density voids would affect the propagation of cracks.

  18. Durability of zirconia thermal-barrier ceramic coatings on air-cooled turbine blades in cyclic jet engine operation

    Science.gov (United States)

    Liebert, C. H.; Jacobs, R. E.; Stecura, S.; Morse, C. R.

    1976-01-01

    Thermal barrier ceramic coatings of stabilized zirconia over a bond coat of Ni Cr Al Y were tested for durability on air cooled turbine rotor blades in a research turbojet engine. Zirconia stabilized with either yttria, magnesia, or calcia was investigated. On the basis of durability and processing cost, the yttria stabilized zirconia was considered the best of the three coatings investigated.

  19. Thermochemical stability and nonstoichiometry of yttria-stabilized bismuth oxide solid solutions

    NARCIS (Netherlands)

    Kruidhof, H.; Vries, de K.J.; Burggraaf, A.J.

    1990-01-01

    The thermochemical stability of fast oxygen ion conducting yttria stabilized bismuthoxide (YSB) solid solutions containing 22.0–32.5 mol% of yttria was investigated. It was shown that in the temperature range between 650–740 C the stabilized cubic δ-phase containing less than 31.8 mol% of yttria is

  20. Tailoring of porosity of yttria-stabilized zirconia tubes as supports for oxygen separation membranes

    DEFF Research Database (Denmark)

    Bjørnetun Haugen, Astri; Kothanda Ramachandran, Dhavanesan; Gurauskis, Jonas

    deformation during debinding. The influence of the amount of pore formers (relative to the amount of ceramic and thermoplastics) on the microstructure of sintered samples, as well as the extrudability and ease of debinding of the feedstock, has been studied. Ceramics with 1-20 μm pores, open porosities......Pure oxygen gas supplied by ceramic oxygen transport membranes can facilitate reduced CO2 emissions through more efficient gasification processes and CO2 capture and storage. Tubular membranes have some advantages compared to planar membranes, such as better resistance to thermal gradients and more...... exceeding 55 % and gas permeabilities close to 10-14 m2 could be produced, demonstrating that thermoplastic extrusion is suitable for fabrication of porous and permeable tubes....

  1. Yttria-stabilized zirconia solid oxide electrolyte fuel cells: Monolithic solid oxide fuel cells

    Science.gov (United States)

    1990-10-01

    The monolithic solid oxide fuel cell (MSOFC) is currently under development for a variety of applications including coal-based power generation. The MSOFC is a design concept that places the thin components of a solid oxide fuel cell in lightweight, compact, corrugated structure, and so achieves high efficiency and excellent performance simultaneously with high power density. The MSOFC can be integrated with coal gasification plants and is expected to have high overall efficiency in the conversion of the chemical energy of coal to electrical energy. This report describes work aimed at: (1) assessing manufacturing costs for the MSOFC and system costs for a coal-based plant; (2) modifying electrodes and electrode/electrolyte interfaces to improve the electrochemical performance of the MSOFC; and (3) testing the performance of the MSOFC on hydrogen and simulated coal gas. Manufacturing costs for both the coflow and crossflow MSOFC's were assessed based on the fabrication flow charts developed by direct scaleup of tape calendering and other laboratory processes. Integrated coal-based MSOFC systems were investigated to determine capital costs and costs of electricity. Design criteria were established for a coal-fueled 200-Mw power plant. Four plant arrangements were evaluated, and plant performance was analyzed. Interfacial modification involved modification of electrodes and electrode/electrolyte interfaces to improve the MSOFC electrochemical performance. Work in the cathode and cathode/electrolyte interface was concentrated on modification of electrode porosity, electrode morphology, electrode material, and interfacial bonding. Modifications of the anode and anode/electrolyte interface included the use of additives and improvement of nickel distribution. Single cells have been tested for their electrochemical performance. Performance data were typically obtained with humidified H2 or simulated coal gas and air or oxygen.

  2. Complementary analysis techniques applied on optimizing suspensions of yttria stabilized zirconia

    DEFF Research Database (Denmark)

    Della Negra, Michela; Foghmoes, Søren Preben Vagn; Klemensø, Trine

    2016-01-01

    of dispersing agent and to optimize the dispersants concentration: Electrokinetic Sonic Amplitude was used to obtain zeta potential, Multiple Light Scattering for evaluating sedimentation rate, and multi-wavelength laser light scattering for measuring particle size distribution. All the results agree upon...

  3. Controlled-Stress Large-Area Pulsed Laser Deposition of Yttria Stabilized Zirconia

    Science.gov (United States)

    2006-05-31

    a wide range of wavelengths from UV to IR. IR Carbon dioxide lasers, near–IR Nd:YAG lasers, HeNe red lasers, argon -ion green lasers, and UV excimer ...lines from argon , krypton, mercury, and xenon lamps . These lamps emitted light at multiple known wavelengths. The spectra from each lamp were

  4. Stability of Ni–yttria stabilized zirconia anodes based on Ni-impregnation

    DEFF Research Database (Denmark)

    Klemensø, Trine; Thydén, Karl Tor Sune; Chen, Ming

    2010-01-01

    Sintering of Ni is a key stability issue for Ni–YSZ anodes, and especially infiltration based electrodes. The potential of MgO, Al2O3, TiO2, CeO2 and Ce0.90Gd0.10O1.95 (CGO10) as sintering inhibitors was investigated for infiltrated Ni based anode structures. The structures were prepared from tap...

  5. Model for impedance of an ionic conductor sandwiched between blocking electrodes. [Example: yttria-stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.C.

    1992-06-24

    The simplest model for the impedance of an ionic conductor sandwiched between two blocking electrodes is a resistor in series with a capacitor (rc pair) representing the bulk material and the conductor-electrode interface, respectively, and a second capacitor parallel to the rc pair representing the electronic dielectric response of the system. In practice, to describe the experimental data satisfactorily, one needs to replace the interface capacitor with a constant-phase-angle (CPA) element and to add a non-Debye dielectric element parallel to the resistor to represent the local ionic movement. In this paper, some of the existing physical models for the CPA and non-Debye dielectric elements are discussed, and an example is presented for analyzing the impedance data using the resultant circuit model.

  6. Morphological changes at the interface of the nickel-yttria stabilized zirconia point electrode

    DEFF Research Database (Denmark)

    Aaberg, Rolf Jarle; Tunold, Reidar; Mogensen, Mogens Bjerg;

    1998-01-01

    ex situ. The anodic current was found to induce a self-catalytic effect on the electrode, and the anodic "steady state" current increased to more than twice the initial value with a time constant of about 40 h. In contrast, cathodic polarization reduced the performance of the electrode...... and the cathodic current decreased significantly with a time constant of about 20 h. Redistribution of material in the reaction zone is suggested to control most of the changes in electrode activity. At anodic overpotentials it was observed that Ni was transported to the electrolyte surface, forming a "necklace...... of dispersed metal particles reduced the TPB length, and accordingly the cathodic current. In addition to the morphological modifications, the catalytic properties of the surfaces were significantly altered as the electrode was polarized. Transformation from cubic to tetragonal YSZ, due to segregation...

  7. Solid Oxide Electrolysis Cells: Microstructure and Degradation of the Ni/Yttria-Stabilized Zirconia Electrode

    DEFF Research Database (Denmark)

    Hauch, Anne; Ebbesen, Sune; Jensen, Søren Højgaard;

    2008-01-01

    Solid oxide fuel cells produced at Risø DTU have been tested as solid oxide electrolysis cells for steam electrolysis by applying an external voltage. Varying the sealing on the hydrogen electrode side of the setup verifies that the previously reported passivation over the first few hundred hours...... of electrolysis testing was an effect of the applied glass sealing. Degradation of the cells during long-term galvanostatic electrolysis testing [850°C, −1/2 A/cm2, p(H2O)/p(H2)=0.5/0.5] was analyzed by impedance spectroscopy and the degradation was found mainly to be caused by increasing polarization resistance...... associated with the hydrogen electrode. A cell voltage degradation of 2%/1000 h was obtained. Postmortem analysis of cells tested at these conditions showed that the electrode microstructure could withstand at least 1300 h of electrolysis testing, however, impurities were found in the hydrogen electrode...

  8. Temperature dependence of hardness in yttria-stabilized zirconia single crystals

    Science.gov (United States)

    Morscher, Gregory N.; Pirouz, Pirouz; Heuer, Arthur H.

    1991-01-01

    The temperature dependence of hardness and microcracking in single-crystal 9.5-mol pct-Y2O3-fully-stabilized cubic-ZrO2 was studied as a function of orientation. Crack lengths increased with increased temperature up to 500 C; above 800 C, no cracks were found, indicating an indentation brittle-to-ductile transition of about 800 C. The temperature dependence of hardness was reduced around 500 C. Etching studies to delineate the plastic zone around and below indents identified the operative slip systems. The role of dislocations and their interactions within the plastic zone on the hardness and indentation fracture behavior of cubic-ZrO2 are discussed.

  9. New Approach to Depositing Yttria-Stabilized Zirconia Buffer Layers for Coated Conductors (Postprint)

    Science.gov (United States)

    2012-02-01

    YBa2Cu3O7− ( YBCO ) cannot be deposited directly onto the tapes due to tape oxidation and chemical interdiffu- sion issues,5 so buffer layers must be used... YBCO can be deposited. Control of the biaxial texture of the final YBCO superconducting layer is critical to the success of the YBCO -coated conductor...Misorientation at YBCO grain boundaries, both [100]-tilt and [100]-twist, have a significant impact on critical cur- rent density (Jc); nearly an

  10. Fracture toughness of yttria-stabilized zirconia sintered in conventional and microwave ovens.

    Science.gov (United States)

    Marinis, Aristotelis; Aquilino, Steven A; Lund, Peter S; Gratton, David G; Stanford, Clark M; Diaz-Arnold, Ana M; Qian, Fang

    2013-03-01

    The fabrication of zirconium dioxide (ZrO2) dental prosthetic substructures requires an extended sintering process (8 to 10 hours) in a conventional oven. Microwave sintering is a shorter process (2 hours) than conventional sintering. The purpose of this study was to compare the fracture toughness of 3 mol % Y2O3-stabilized ZrO2 sintered in a conventional or microwave oven. Partially sintered ZrO2 specimens from 3 manufacturers, KaVo, Lava 3M, and Crystal HS were milled (KaVo Everest engine) and randomly divided into 2 groups: conventional sintering and microwave sintering (n=16 per group). The specimens were sintered according to the manufacturers' recommendations and stored in artificial saliva for 10 days. Fracture toughness was determined by using a 4-point bend test, and load to fracture was recorded. Mean fracture toughness for each material was calculated. A 2-way ANOVA followed by the Tukey HDS post hoc test was used to assess the significance of sintering and material effects on fracture toughness, including an interaction between the 2 factors (α=.05). The 2-way ANOVA suggested a significant main effect for ZrO2 manufacturer (P.05). The main effect of the sintering process (Conventional [5.30 MPa·m(1/2) ±1.00] or Microwave [5.36 MPa·m(1/2) ±0.92]) was not significant (P=.76), and there was no interaction between sintering and ZrO2 manufacturer (P=.91). Based on the results of this study, no statistically significant difference was observed in the fracture toughness of ZrO2 sintered in microwave or conventional ovens. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  11. Factors Influencing Residual Stresses in Yttria Stabilized Zirconia Thermal Barrier Coatings

    Science.gov (United States)

    McGrann, Roy T. R.; Rybicki, Edmund F.; Shadley, John R.; Brindley, William J.

    1997-01-01

    To improve gas turbine and diesel engine performance using thermal barrier coatings (TBC's) requires an understanding of the factors that influence the in-service behavior of thermal barrier coatings. One of the many factors related to coating performance is the state of stress in the coating. The total stress state is composed of the stresses due to the in-service loading history and the residual stresses. Residual stresses have been shown to affect TBC life, the bond strength of thermal spray coatings, and the fatigue life of tungsten carbide coatings. Residual stresses are first introduced in TBC's by the spraying process due to elevated temperatures during processing and the difference in coefficients of thermal expansion of the top coat, bond coat, and substrate. Later, the residual stresses can be changed by the in-service temperature history due to a number of time and temperature dependent mechanisms, such as oxidation, creep, and sintering. Silica content has also been shown to affect sintering and the cyclic life of thermal barrier coatings. Thus, it is important to understand how the spraying process, the in-service thermal cycles, and the silica content can create and alter residual stresses in thermal barrier coatings.

  12. Laser surface treatment of plasma-sprayed yttria-stabilized zirconia coatings

    Directory of Open Access Journals (Sweden)

    Pinto, M. A.

    2005-12-01

    Full Text Available Un equipo láser continuo de CO2, con potencia nominal de 1 kW, se utilizó para sellar la superficie revestida con ZrO2 8 % Y2O3 por proyección por plasma sobre un substrato de acero AISI 1045. Se investigaron los efectos del tratamiento de fusión con láser sobre la microestrutura y la resistencia a la corrosión del recubrimiento. La resistencia a la corrosión se analizó por medidas electroquímicas en una solución de NaCl al 3 %. Las micrografias mostraron que la superficie del revestimiento presentó varias grietas pequeñas, sin embargo, no fueron observados poros. La microestructura de la capa sellada presentó una estructura en forma de columnas con crecimiento perpendicular a la superficie libre. El sellado a láser mejora la resistencia a la corrosión de los recubrimientos y aumenta la microdureza.

    Un equipo láser continuo de CO2, con potencia nominal de 1 kW, se utilizó para sellar la superficie revestida con ZrO2 8 % Y2O3 por proyección por plasma sobre un substrato de acero AISI 1045. Se investigaron los efectos del tratamiento de fusión con láser sobre la microestrutura y la resistencia a la corrosión del recubrimiento. La resistencia a la corrosión se analizó por medidas electroquímicas en una solución de NaCl al 3 %. Las micrografias mostraron que la superficie del revestimiento presentó varias grietas pequeñas, sin embargo, no fueron observados poros. La microestructura de la capa sellada presentó una estructura en forma de columnas con crecimiento perpendicular a la superficie libre. El sellado a láser mejora la resistencia a la corrosión de los recubrimientos y aumenta la microdureza.

  13. Tetragonal zirconia: Wet chemical preparation, mechanical and electrical properties

    NARCIS (Netherlands)

    Keizer, K.; Hemert, van M.; Graaf, van de M.A.C.G.; Burggraaf, A.J.

    1985-01-01

    Yttria-stabilized zirconia powders were prepared in the composition range of 3 to 13 at% yttria. The hydrolysis-gel precipitation technique was used, starting from metal alkoxides or chlorides. In the composition range between 5 and 10 at% yttria, the materials sintered at 1250°C have a fully tetrag

  14. Nickel/Yttria-stabilised zirconia cermet anodes for solid oxide fuel cells

    NARCIS (Netherlands)

    Primdahl, Søren

    1999-01-01

    This thesis deals with the porous Ni/yttria-stabilized zirconia (YSZ) cermet anode on a YSZ electrolyte for solid oxide fuel cells (SOFC). Such anodes are predominantly operated in moist hydrogen at 700°C to 1000°C, and the most important technological parameters are the polarization resistance and

  15. Fracture strength of yttria-stabilized zirconium-dioxide (Y-TZP) fixed dental prostheses (FDPs) with different abutment core thicknesses and connector dimensions.

    Science.gov (United States)

    Ambré, Marcus J; Aschan, Fredrik; Vult von Steyern, Per

    2013-07-01

    The aim of this study was to investigate the fracture strength and fracture mode of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) posterior three-unit FDPs with varying connector dimension and abutment core thickness. Seventy 3-unit posterior FDP cores made of Y-TZP were divided into 7 groups with varying connector dimensions and abutment core thicknesses. All the FDPs underwent a simulated aging process including veneering, firing applications, thermocycling, and cyclic preloading. Finally the FDPs were subjected to load until fracture. Significant difference was seen between the different subgroups (p strength. All fractures of the specimens involved the connector. Within the limitations of this in vitro study, it can be concluded that the strength of an all-ceramic Y-TZP FDP beam depends more on the connector dimension than on the thickness of the abutment core. Results indicate that the minimum abutment core thickness of an all-ceramic Y-TZP FDP might be reduced, compared to the recommended thickness, without reducing the strength of the reconstruction. This indication, however, needs to be verified by further studies before being considered generally applicable. © 2012 by the American College of Prosthodontists.

  16. Preparation and analysis of zirconia oxygen sensors

    Institute of Scientific and Technical Information of China (English)

    LUO Zhi-an; XIAO Jian-zhong; XIA Feng

    2006-01-01

    Thimble zirconia oxygen sensors were prepared with yttria stabilized zirconia(YSZ). The surfaces of the electrode,electrolyte and their interface were observed by scanning electron microscope(SEM). The sensor was examined with engine bench test to evaluate the essential performance. The results show that the oxygen sensor has good performance,which can meet the demand of practical applications. Chemical equilibrium theory was introduced to explain electromotive force of the sensors and the influence of temperature on the signals. The educed theoretical model of electromotive force agrees well with testing results.

  17. Yttria-stabilized zirkonia / gadolinium zirconate double-layer plasma-sprayed thermal barrier coating systems (TBCs)

    Energy Technology Data Exchange (ETDEWEB)

    Bakan, Emine

    2015-07-01

    Thermal barrier coating (TBC) research and development is driven by the desirability of further increasing the maximum inlet temperature in a gas turbine engine. A number of new top coat ceramic materials have been proposed during the last decades due to limited temperature capability (1200 C) of the state-of-the-art yttria-stabilized zirconia (7 wt. % Y{sub 2}O{sub 3}-ZrO{sub 2}, YSZ) at long term operation. Zirconate pyrochlores of the large lanthanides((Gd → La){sub 2}Zr{sub 2}O{sub 7}) have been particularly attractive due to their higher temperature phase stability than that of the YSZ. Nonetheless, the issues related with the implementation of pyrochlores such as low fracture toughness and formation of deleterious interphases with thermally grown oxide (TGO, Al{sub 2}O{sub 3}) were reported. The implication was the requirement of an interlayer between the pyrochlores and TGO, which introduced double-layer systems to the TBC literature. Furthermore, processability issues of pyrochlores associated with the different evaporation rates of lanthanide oxides and zirconia resulting in unfavorable composition variations in the coatings were addressed in different studies. After all, although the material properties are available, there is a paucity of data in the literature concerning the properties of the coatings made of pyrochlores. From the processability point of view the most reported pyrochlore is La{sub 2}Zr{sub 2}O{sub 7}. Hence, the goal of this research was to investigate plasma-sprayed Gd{sub 2}Zr{sub 2}O{sub 7} (GZO) coatings and YSZ/GZO double-layer TBC systems. Three main topics were examined based on processing, performance and properties: (i) the plasma spray processing of the GZO and its impact on the microstructural and compositional properties of the GZO coatings; (ii) the cycling lifetime of the YSZ/GZO double-layer systems under thermal gradient at a surface temperature of 1400 C; (iii) the properties of the GZO and YSZ coatings such as

  18. Durability of high performance Ni-yttria stabilized zirconia supported solid oxide electrolysis cells at high current density

    DEFF Research Database (Denmark)

    Hjalmarsson, Per; Sun, Xiufu; Liu, Yi-Lin;

    2014-01-01

    . The results showed rapid initial fuel electrode degradation during the first 350 h followed by partial reactivation. The serial resistance was found to increase with time but in an exponentially decaying behavior. A discussion is made based on the detailed electrochemical results together with post...

  19. Defect structure of yttria-stabilized zirconia and its influence on the ionic conductivity at elevated temperatures

    DEFF Research Database (Denmark)

    Goff, J.P.; Hayes, W.; Hull, S.

    1999-01-01

    of neutron and x-ray diffraction data, including both Bragg and coherent diffuse scattering components, has identified three principal types of defects within the fluorite lattice. At low yttria concentrations (x... relatively few oxygen vacancies, causing the lattice to undergo a slight tetragonal distortion of the type observed in the tetragonal phase of (ZrO2)(1-x)(Y2O3)(x) at x anion sites in the (111) fluorite...... directions, with a cation located between them and extensive relaxations of the surrounding nearest-neighbor cations and anions. As the yttria content increases, these (111) vacancy Fairs pack together in (112) directions to form aggregates, whose short-range defect structure resembles the long-range crystal...

  20. Microstructure and high-temperature mechanical behavior of alumina/alumina-yttria-stabilized tetragonal zirconia multilayer composites

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Melendo, M.; Clauss, C.; Dominguez-Rodriguez, A. [Dept. de Fisica de la Materia Condensada, Sevilla (Spain); Sanchez-Herencia, A.J.; Moya, J.S. [CSIC, Madrid (Spain). Inst. de Ciencias de Materiales

    1997-08-01

    Layered composites of alternate layers of pure Al{sub 2}O{sub 3} (thickness of 125 {micro}m) and 85 vol% Al{sub 2}O{sub 3}-15 vol% ZrO{sub 2} that was stabilized with 3 mol% Y{sub 2}O{sub 3} (thickness of 400 {micro}m) were obtained by sequential slip casting and then fired at either 1,550 or 1,700 C. Constant-strain-rate tests were conducted on these materials in air at 1,400 C at an initial strain rate of 2 {times} 10{sup {minus}5} s{sup {minus}1}. The load axis was applied both parallel and perpendicular to the layer interfaces. Catastrophic failure occurred for the composite that was fired at 1,700 C, because of the coalescence of cavities that had developed in grain boundaries of the Al{sub 2}O{sub 3} layers. In comparison, the composite that was fired at 1,550 C demonstrated the ductility of the Al{sub 2}O{sub 3} + YTZP layer, but at a flow stress level that was determined by the Al{sub 2}O{sub 3} layer.

  1. Critical effect of cubic phase on aging in 3mol% yttria-stabilized zirconia ceramics for hip replacement prosthesis.

    Science.gov (United States)

    Chevalier, Jérôme; Deville, Sylvain; Münch, Etienne; Jullian, Romain; Lair, Frédéric

    2004-11-01

    The isothermal tetragonal-to-monoclinic transformation of 3Y-TZP ceramics sintered at two different temperatures (1450 degrees C and 1550 degrees C) and duration (2 and 5h) is investigated at 134 degrees C in steam. Particular attention is paid to the presence of a cubic phase and its effect on isothermal aging. Sintering at 1550 degrees C can result in a significant amount of large cubic grains in the specimens, that have a detrimental impact on aging resistance, especially for the first stage of the aging process. Cubic grains appear to be enriched in yttrium, which in turn leads to a depletion of yttrium in the neighboring tetragonal grains. These grains will act as nucleation sites for tetragonal-to-monoclinic transformation. Even for specimens sintered at lower temperature, i.e. 1450 degrees C, the presence of a cubic phase is expected from the phase diagram, leading to a significant effect on aging sensitivity.

  2. Fabrication of thin yttria-stabilized-zirconia dense electrolyte layers by inkjet printing for high performing solid oxide fuel cells

    DEFF Research Database (Denmark)

    Esposito, Vincenzo; Gadea, Christophe; Hjelm, Johan

    2015-01-01

    In this work, we present how a low-cost HP Deskjet 1000 inkjet printer was used to fabricate a 1.2 mm thin, dense and gas tight 16 cm2 solid oxide fuel cells (SOFC) electrolyte. The electrolyte was printed using an ink made of highly diluted (...) powders (50 nm in size) in an aqueous medium. The ink was designed to be a highly dispersed, long term stable colloidal suspension, with optimal printability characteristics. The electrolyte was made by a multiple printing procedure, which ensures coverage of the several flaws occurring in a single...... printing pass. Together with an optimized sintering procedure this resulted in good adhesion and densification of the electrolyte. The SOFC exhibited a close-to-theoretical open circuit voltage and a remarkable peak power density above 1.5 W cm-2 at 800 °C....

  3. Phase evolution and thermal properties of yttria-stabilized hafnia nano-coatings deposited on alumina

    Science.gov (United States)

    Rubio, Ernesto Javier

    High-temperature coatings are critical to the future power-generation systems and industries. Thermal barrier coatings (TBCs), which are usually the ceramic materials applied as thin coatings, protect engine components and allow further increase in engine temperatures for higher efficiency. Thus, the durability and reliability of the coating systems have to be more robust compared to current natural gas based engines. While a near and mid-term target is to develop TBC architecture with a 1300 °C surface temperature tolerance, a deeper understanding of the structure evolution and thermal behavior of the TBC-bond coat interface, specifically the thermally grown oxide (TGO), is of primary importance. In the present work, attention is directed towards yttria-stabilized hafnia (YSH) coatings on alumina (α-Al2O 3) to simulate the TBC-TGO interface and understand the phase evolution, microstructure and thermal oxidation of the coatings. YSH coatings were grown on α-Al2O3 substrates by sputter deposition by varying coating thickness in a wide range ˜30-1000 nm. The effect of coating thickness on the structure, morphology and the residual stress has been investigated using X-ray diffraction (XRD) and high resolution scanning electron microscopy (SEM). Thermal oxidation behavior of the coatings has been evaluated using the isothermal oxidation measurements under static conditions. X-ray diffraction analyses revealed the existence of monoclinic hafnia phase for relatively thin coatings indicating that the interfacial phenomena are dominant in phase stabilization. The evolution towards pure stabilized cubic phase of hafnia with the increasing coating thickness is observed. The SEM results indicate the changes in morphology of the coatings; the average grain size increases from 15 to 500 nm with increasing thickness. Residual stress was calculated employing XRD using the variable ψ-angle. Relation between residual stress and structural change is also studied. The results

  4. Zirconia implant abutments: microstructural analysis.

    Science.gov (United States)

    Vaquero-Aguilar, Cristina; Jiménez-Melendo, Manuel; Torres-Lagares, Daniel; Llena-Blasco, Oriol; Bruguera, August; Llena-Blasco, Jaime; García-Calderón, Manuel; Velázquez-Cayón, Rocío; Gutiérrez-Pérez, José-Luis

    2012-01-01

    Yttria-stabilized zirconia (ZrO₂-Y₂O₃) ceramics have received increasing attention in recent years because of their stress-induced tetragonal-to-monoclinic (martensitic) transformation. This unique process acts as a toughening mechanism, imparting strength and toughness to the ceramic alloy. This property, along with well-documented biocompatibility, is now being exploited in an increasing number of medical applications, including implant dentistry. To prevent clinical problems and predict their behavior and physical limitations, a characterization of the ceramic elements used in dental restorations is essential. The aim of the present study is to characterize the crystal structure, elemental composition, and micr ostructure of asreceived ZiReal Post (Biomet 3i) zirconium oxide abutments, as well as specimens coated with a first layer of a low-fusing fluoroapatite ceramic. Zirconium oxide abutments, both as-received and porcelain-coated, were studied using the following techniques: x-ray diffraction, x-ray fluorescence, energy dispersive x-ray spectroscopy, optical microscopy, and scanning and transmission electron microscopy. X-ray analyses detected only the presence of Zr, O, Y, and hafnium (Hf), in an amount of 3% to 4% molecular weight Y₂O₃-ZrO₂. X-ray diffraction measurements showed that the ceramic abutment crystallizes mainly in the tetragonal phase, with some residual monoclinic phase. The microstructure is characterized by a rather homogenous grain distribution, formed by equiaxed and fine grains with a mean size of 0.30 Μm. Compositional and diffraction results are consistent with polycrystalline yttria-stabilized tetragonal zirconia. The material is susceptible to undergoing the stress-induced transformation toughening mechanism because of the very fine grain size. Except for machining ring marks, the surfaces exhibit an excellent finishing quality. No structural modifications were observed in the fluoroapatite ceramic-coated abutments

  5. The effect of melt infiltration of borosilicate glass on biaxial flexural strength of porcelain-veneered zirconia

    Science.gov (United States)

    Joo, Kyu Ji; Song, Kyung Woo; Jung, Jong Hyun; Ahn, Hyo Jin; Park, Il Song; Lee, Min Ho; Bae, Tae Sung

    2011-08-01

    To evaluate the effect of melt infiltration on the biaxial flexural strength of porcelain-bonded zirconia, borosilicate glasses were used in this study. Presintered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) blocks were milled and used for disc specimens. Prior to veneering of porcelain, the infiltration of borosilicate glass on zirconia was performed at 1,100 °C for 1 h. After a biaxial flexural test with the crosshead speed of 0.1 mm/min, fractured surfaces and interfaces between zirconia and veneer porcelain were observed with a Scanning Electron Microscope (SEM). The fracture strength of sintered zirconia and veneer porcelain was significantly increased by the melt infiltration of borosilicate glass (P porcelain increased slightly. The sintered zirconia group showed a smooth fracture surface containing many pores, but the glass-infiltrated zirconia group showed a rough fracture surface.

  6. Microstructured zirconia surfaces modulate osteogenic marker genes in human primary osteoblasts.

    Science.gov (United States)

    Bergemann, Claudia; Duske, Kathrin; Nebe, J Barbara; Schöne, André; Bulnheim, Ulrike; Seitz, Hermann; Fischer, Jens

    2015-01-01

    In dentistry, zirconia has been used since the early 1990s for endodontic posts, more recently for implant abutments and frameworks for fixed dental prostheses. Zirconia is biocompatible and mechanically strong enough to serve as implant material for oral implants. Although several zirconia implant systems are available, currently the scientific and clinical data for zirconia implants are not sufficient to recommend them for routine clinical use. Here the influence of microstructured yttria-stabilized zirconia (YZ) on human primary osteoblast (HOB) behavior was determined. YZ surfaces were treated by sandblasting (YZ-S), acid etching (YZ-SE) and additionally heat treatment (YZ-SEH). Morphological changes of HOB were determined by scanning electron microscopy. Actin cytoskeleton was investigated by laser scanning microscopy and analyzed by novel actin quantification software. Differentiation of HOB was determined by real time RT-PCR. Improved mechanical interlocking of primary HOB into the porous microstructure of the acid etched and additionally heat treated YZ-surfaces correlates with drastically increased osteocalcin (OCN) gene expression. In particular, OCN was considerably elevated in primary HOB after 3 days on YZ-SE (13-fold) as well as YZ-SEH (12-fold) surfaces. Shorter actin filaments without any favored orientation on YZ-SE and YZ-SEH surfaces are associated with higher roughness (Ra) values. Topographically modified yttria-stabilized zirconia is a likely material for dental implants with cell stimulating properties achieving or actually exceeding those of titanium.

  7. Contamination of dental zirconia before final firing: effects on mechanical properties.

    Science.gov (United States)

    Ban, Seiji; Okuda, Yuji; Noda, Makoto; Tsuruki, Jiro; Kawai, Tatsushi; Kono, Hiroshi

    2013-01-01

    Plate-like specimens were prepared, using a diamond saw, from Cercon -a pre-sintered yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) block. These specimens were treated with 10 kinds of dental materials which acted as contaminants, and then sintered at 1,350°C or 1,450°C. After the final firing, specimens were subjected to a three-point flexural test and Vickers hardness test. Their surfaces were also characterized by scanning electron microscopy and X-ray diffractometry. Phosphorus-containing contaminants reduced the three-point flexural strength and hardness of final sintered zirconia due to the formation of YPO4 and phase transformation from tetragonal to monoclinic zirconia. Gypsum also reduced both mechanical properties due to the formation of CaZrO3 and phase transformation from tetragonal to cubic zirconia. Other contaminants showed no adverse effects on the mechanical properties of final sintered zirconia.

  8. Thermal Conductivity of Alumina-Toughened Zirconia Composites

    Science.gov (United States)

    Bansal, Narottam P.; Zhu, Dong-Ming

    2003-01-01

    10-mol% yttria-stabilized zirconia (10YSZ)-alumina composites containing 0 to 30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity of the composites, determined at various temperatures using a steady-state laser heat flux technique, increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from simple rule of mixtures.

  9. Microscopic mechanism of stability in yttria-doped zirconia

    CERN Document Server

    Ostanin, S A

    2001-01-01

    The relaxed configurations of yttria-stabilized zirconia (YSZ) between 3 and 10 mol. % Y sub 2 O sub 3 were modeled within the pseudopotential technique. The vibration mode corresponding to the soft phonon in pure c-ZrO sub 2 has been calculated for each Y sub 2 O sub 3 composition. These anharmonic vibrations, associated with stabilization of YSZ, have been investigated within the self-consistent phonon approximation that makes obtainable the fine structure in spectral density. In studying the phonon dynamics, it is proposed to use the displacement probability density which can quantify very accurately the transition temperature needed to stabilize the YSZ cubic phase

  10. Growth, Structure, and Thermal Conductivity of Yttria-Stabilized Hafnia Thin Films (Postprint)

    Science.gov (United States)

    2012-01-01

    controlled by an Athena X25 controller. B. Characterization. The grown YSH coatings were characterized by performing structure, morphology and thermal...and then through an electro- optic modulator (EOM), which imposes a square-wave pulse train with a frequency of 9.8 MHz. The pump beam is then aligned... optical parametric oscillator for wavelength modification (λ = 700 nm). Both pump and probe beams also have half-waveplate/polarizer combinations for

  11. The atomistic structure of yttria stabilised zirconia at 6.7 mol%: an ab initio study.

    Science.gov (United States)

    Parkes, Michael A; Tompsett, David A; d'Avezac, Mayeul; Offer, Gregory J; Brandon, Nigel P; Harrison, Nicholas M

    2016-11-16

    Yttria stabilized zirconia (YSZ) is an important oxide ion conductor used in solid oxide fuel cells, oxygen sensing devices, and for oxygen separation. Doping pure zirconia (ZrO2) with yttria (Y2O3) stabilizes the cubic structure against phonon induced distortions and this facilitates high oxide ion conductivity. The local atomic structure of the dopant is, however, not fully understood. X-ray and neutron diffraction experiments have established that, for dopant concentrations below 40 mol% Y2O3, no long range order is established. A variety of local structures have been suggested on the basis of theoretical and computational models of dopant energetics. These studies have been restricted by the difficulty of establishing force field models with predictive accuracy or exploring the large space of dopant configurations with first principles theory. In the current study a comprehensive search for all symmetry independent configurations (2857 candidates) is performed for 6.7 mol% YSZ modelled in a 2 × 2 × 2 periodic supercell using gradient corrected density functional theory. The lowest energy dopant structures are found to have oxygen vacancy pairs preferentially aligned along the 〈210〉 crystallographic direction in contrast to previous results which have suggested that orientation along the 〈111〉 orientation is favourable. Analysis of the defect structures suggests that the Y(3+)-Ovac interatomic separation is an important parameter for determining the relative configurational energies. Current force field models are found to be poor predictors of the lowest energy structures. It is suggested that the energies from a simple point charge model evaluated at unrelaxed geometries is actually a better descriptor of the energy ordering of dopant structures. Using these observations a pragmatic procedure for identifying low energy structures in more complicated material models is suggested. Calculation of the oxygen vacancy migration activation energies within

  12. Surface roughened zirconia: towards hydrothermal stability.

    Science.gov (United States)

    Camposilvan, Erik; Flamant, Quentin; Anglada, Marc

    2015-07-01

    Surface roughness is needed in several yttria-stabilized zirconia components used in restorative dentistry for osseointegration or adhesion purposes. This can be achieved by different treatments, which may also modify the microstructure of the surface. Among them, sandblasting and chemical etching are widely used, but their effect on hydrothermal aging of zirconia is not fully understood. In the present work, the zirconia long-term stability of rough surfaces prepared by these techniques is analyzed and a method is proposed for preventing hydrothermal aging while maintaining the original surface appearance and mechanical properties. The method involves pressure infiltration of a Cerium salt solution on the roughened surfaces followed by a thermal treatment. The solution, trapped by surface defects and small pores, is decomposed during thermal treatment into Cerium oxide, which is diffused at high temperature, obtaining Ce co-doping in the near-surface region. In addition, the microstructural changes induced in the near-surface by sandblasting or chemical etching are removed by the thermal treatment together with surface defects. No color modification was observed and the final roughness parameters were in the range of existing implants of proved good osseointegration. The aging resistance of Ce co-doped materials was strongly enhanced, showing the absence of aging after artificial degradation, increasing in this way the surface mechanical integrity. The proposed treatment is easily applicable to the current manufacturing procedures of zirconia dental posts, abutments, crowns and dentures, representing a solution to hydrothermal aging in these and other biomedical applications.

  13. Effects of yttrium, aluminum and chromium concentrations in bond coatings on the performance of zirconia-yttria thermal barriers

    Science.gov (United States)

    Stecura, S.

    1980-01-01

    A cyclic furnace study was conducted on thermal barrier systems to evaluate the effects of yttrium, chromium and aluminum in nickel-base alloy bond coatings and the effect of bond coating thickness on yttria-stabilized zirconia thermal barrier coating life. Without yttrium in the bond coatings, the zirconia coatings failed very rapidly. Increasing chromium and aluminum in the Ni-Cr-Al-Y bond coatings increased total coating life. This effect was not as great as that due to yttrium. Increased bond coat thickness was also found to increase life.

  14. Influence of rare earths on the sintering of zirconia-yttria

    Directory of Open Access Journals (Sweden)

    Canova I.C.

    1999-01-01

    Full Text Available Yttria stabilized zirconia sintered by silicate glass phase with addition of ytterbium or gadolinium was investigated. The grain growth rate was found to be higher in the gadolinium doped samples. The glass phase of the ytterbium doped sample showed partial crystallization on cooling. Grain conductivity was found to be highest in samples with a half hour of sintering, having decreased due to stabilizing ion migration from the grains to the grain boundary glassy phase. The differences observed in the sintering behavior and properties of the sintered bodies are attributed to the different ionic radii of the Yb+3 and Gd+3 ions.

  15. Fracture load of implant-supported zirconia all-ceramic crowns luted with various cements.

    Science.gov (United States)

    Lim, Hyun-Pil; Yoo, Jeong-Min; Park, Sang-Won; Yang, Hong-So

    2010-01-01

    This study compared the fracture load and failure types of implant-supported zirconia all-ceramic crowns cemented with various luting agents. The ceramic frameworks were fabricated from a presintered yttria-stabilized zirconium dioxide block using computer-aided design/computer-assisted manufacturing technology, and were then veneered with feldspathic porcelain. Three luting agents were used. Composite resin cement (1,560.78 +/- 39.43 N) showed the highest mean fracture load, followed by acrylic/urethane cement (1,116.20 +/- 77.32 N) and zinc oxide eugenol cement (741.21 +/- 41.95 N) (P < .05). The types of failure varied between groups.

  16. Implantation of high concentration noble gases in cubic zirconia and silicon carbide: A contrasted radiation tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Velişa, Gihan, E-mail: gihan@tandem.nipne.ro [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Debelle, Aurélien; Thomé, Lionel; Mylonas, Stamatis [Centre de Sciences Nucléaires et de Sciences de la Matière, CNRS-IN2P3-Université Paris-Sud, Bât. 108, F-91405 Orsay (France); Vincent, Laetitia [Centre de Sciences Nucléaires et de Sciences de la Matière, CNRS-IN2P3-Université Paris-Sud, Bât. 108, F-91405 Orsay (France); Institut d’Electronique Fondamentale, Université Paris-Sud, UMR 8622, Bât. 220, 91405 Orsay (France); Boulle, Alexandre [Science des Procédés Céramiques et de Traitements de Surface, CNRS UMR 7315, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges (France); Jagielski, Jacek [Institute for Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); National Center for Nuclear Research, PL-05-400 Swierk/Otwock (Poland); Pantelica, Dan [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania)

    2014-08-01

    The modifications of the microstructure of yttria-stabilized cubic zirconia and silicon carbide single crystals implanted with high concentrations of noble gas ions and subsequently annealed at high temperature were characterized using RBS/C, XRD and TEM. It is found that the annealing behavior is strongly dependent on both the material and the implanted noble gases. Ar-implanted yttria-stabilized zirconia shows no significant microstructural modification upon annealing at 800 °C, e.g. dislocations are still present and the size of the Ar bubbles does not evolve. This is in strong contrast with previous observations on helium-implanted zirconia, where the formation of bubbles and elongated fractures were observed. In the case of SiC, thermal annealing at 1000 °C shows an enhanced damage recovery when He is implanted as compared to Ar implantation and the recrystallization of the matrix is accompanied with the release of noble gas atoms. This difference can be ascribed to different atomic radii, and thus mobility of implanted species.

  17. The influence of microstructure and functional-grading on the electrochemical response of Pt/Yttria-stabilized zirconia nanocomposite thin films in micro-solid oxide fuel cells

    Science.gov (United States)

    Rottmayer, Michael; Singh, Raj; Huang, Hong

    2016-11-01

    The use of microfabricated solid oxide fuel cells (mSOFCs) is a promising technology for a low temperature operation (as low as 300 °C) with reduced start-up time and improved energy density. However, one of the limitations to widespread adoption of this technology has been due to the use of Pt electrodes, which exhibit poor bulk ionic conductivity and suffers from Ostwald ripening. Pt/YSZ is a promising alternative for providing both microstructural and electrochemical stability to the electrode layer. The objective of this research is to investigate the electrochemical performance and long term morphological stability of Pt/YSZ, by tailoring the composition, porosity, thickness, and functional-graded distribution, for use as a high performance mSOFC cathode. The Pt/YSZ cathodes were deposited through a co-sputtering process. An increase in the oxygen reduction reaction (ORR) charge transfer kinetics are observed with the Pt/YSZ cathode versus pure Pt, along with a significantly more stable morphology over a 24hr period. Although the mSOFC performance is found to be sensitive to Pt/YSZ composition at the TPB interface, the mass diffusion of oxygen through the cathode is determined to be the rate limiting step. The increased porosity in the Pt/YSZ led to more efficient oxygen diffusion and higher mSOFC performance.

  18. Electrode Properties of Sr-Doped LaMnO3 on Yttria-Stabilized Zirconia I: Three-phase boundary area

    NARCIS (Netherlands)

    Heuveln, van F.H.; Bouwmeester, H.J.M.; Berkel, van F.P.F.

    1997-01-01

    The interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells, SrxLa1–xMnO3 (SLM), was investigated with respect to its electrochemical performance. The interface microstructure was characterized by grain size and coverage of SLM on the electrolyte surface. Variati

  19. Electrode Properties of Sr-Doped LaMnO3 on Yttria-Stabilized Zirconia I: Three-phase boundary area

    OpenAIRE

    Heuveln, van, J.J.; Bouwmeester, H. J. M.; Berkel, van, T.L.

    1997-01-01

    The interface microstructure of the state-of-the-art cathode material for solid oxide fuel cells, SrxLa1–xMnO3 (SLM), was investigated with respect to its electrochemical performance. The interface microstructure was characterized by grain size and coverage of SLM on the electrolyte surface. Variation of the grain size was obtained by using three different sintering temperatures, whereas variation of the coverage was obtained by using two powders with a different morphology. This resulted in ...

  20. Synthesis, characterization and performance of robust poison-resistant ultrathin film yttria stabilized zirconia - nickel anodes for application in solid electrolyte fuel cells

    Science.gov (United States)

    Garcia-Garcia, F. J.; Yubero, F.; Espinós, J. P.; González-Elipe, A. R.; Lambert, R. M.

    2016-08-01

    We report on the synthesis of undoped ∼5 μm YSZ-Ni porous thin films prepared by reactive pulsed DC magnetron sputtering at an oblique angle of incidence. Pre-calcination of the amorphous unmodified precursor layers followed by reduction produces a film consisting of uniformly distributed tilted columnar aggregates having extensive three-phase boundaries and favorable gas diffusion characteristics. Similarly prepared films doped with 1.2 at.% Au are also porous and contain highly dispersed gold present as Ni-Au alloy particles whose surfaces are strongly enriched with Au. With hydrogen as fuel, the performance of the undoped thin film anodes is comparable to that of 10-20 times thicker typical commercial anodes. With a 1:1 steam/carbon feed, the un-doped anode cell current rapidly falls to zero after 60 h. In striking contrast, the initial performance of the Au-doped anode is much higher and remains unaffected after 170 h. Under deliberately harsh conditions the performance of the Au-doped anodes decreases progressively, almost certainly due to carbon deposition. Even so, the cell maintains some activity after 3 days operation in dramatic contrast with the un-doped anode, which stops working after only three hours of use. The implications and possible practical application of these findings are discussed.

  1. Analysis of tetragonal to monoclinic phase transformation caused by accelerated artificial aging and the effects of microstructure in stabilized zirconia

    Science.gov (United States)

    Lucas, Thomas J.

    This investigation addresses the issue that yttria stabilized zirconia is being used as a dental biomaterial without substantial evidence of its long-term viability. Furthermore, stabilized zirconia (SZ) undergoes low temperature degradation (LTD), which can lead to roughening of the surface. A rougher exterior can lead to increased wear of the antagonist in the oral environment. Despite the LTD concerns, SZ is now widely used in restorative dentistry, including full contour crowns. A comparison of aging methods to determine the role of artificial aging on inducing the transformation has not been extensively studied. Therefore, simulations of the transformation process were investigated by comparing different methods of accelerated aging. The rejected null hypothesis is that the temperature of aging treatment will not affect the time required to cause measurable monoclinic transformation of yttria stabilized zirconia. The transformation of SZ starts at the surface and progresses inward; however, it is unclear whether the progression is constant for different aging conditions. This investigation analyzed the depth of transformation as a function of aging conditions for stabilized zirconia in the top 5-6 mum from the surface. The rejected null hypothesis is that the transformation amount is constant throughout the first six micrometers from the surface. The effects of grain size on the amount of monoclinic transformation were also investigated. This study aimed to determine if the grain size of partially stabilized zirconia affects the amount of monoclinic transformation, surface roughness, and property degradation due to aging. The rejected null hypothesis is that the grain size will not affect the amount of monoclinic transformation, thus have no effect on surface roughening or property degradation. The final part of this study addresses the wear of enamel when opposing zirconia by observing how grain size and aging affected the wear rate of an enamel antagonist

  2. Optical properties of zirconia ceramics for esthetic dental restorations: A systematic review.

    Science.gov (United States)

    Shahmiri, Reza; Standard, Owen Christopher; Hart, Judy N; Sorrell, Charles Christopher

    2017-09-16

    Yttria-stabilized tetragonal zirconia polycrystal has been used as a dental biomaterial for several decades because the fracture toughness and bend strength are increased by a stress-induced transformation-toughening mechanism. However, its esthetics are compromised by its poor translucency and grayish-white appearance. The purpose of the present systematic review was to assess information on the mechanical, chemical, and optical requirements of monolithic zirconia dental restorations. The following databases (2010 to 2015) were electronically searched: ProQuest, EMBASE, SciFinder, MRS Online Proceedings Library, Medline, Compendex, and Journal of the American Ceramic Society. The search was limited to English-language publications, in vitro studies, experimental reports, and modeling studies. The data from 57 studies were considered in order to review the intrinsic and extrinsic characteristics of zirconia and their effects on the optical properties. The materials and microstructural issues relevant to the esthetics and long-term stability of zirconia have been considered in terms of monolithic restorations, while there also are restorations specifically for esthetic applications. Although zirconia-toughened lithium silicate offers the best esthetic outcomes, transformation-toughened zirconia offers the best mechanical properties and long-term stability; cubic stabilized zirconia offers a potential compromise. The properties of these materials can be altered to some extent through the appropriate application of intrinsic (such as, annealing) and extrinsic (such as, shade-matching) parameters. Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.

  3. Fused Zirconia

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    ScopeThis standard specifies the terms,definitions,classification,brands,technical requirements,test methods,inspection rules,packing,marking,transportation,storage,and quality certificate of fused zirconia.This standard is applicable to monoclinic fused zirconia and partially stabilized fused zirconia.

  4. Yttria and ceria doped zirconia thin films grown by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    F. Saporiti

    2013-06-01

    Full Text Available The Yttria stabilized Zirconia (YSZ is a standard electrolyte for solid oxide fuel cells (SOFCs, which are potential candidates for next generation portable and mobile power sources. YSZ electrolyte thin films having a cubic single phase allow reducing the SOFC operating temperature without diminishing the electrochemical power density. Films of 8 mol% Yttria stabilized Zirconia (8YSZ and films with addition of 4 weight% Ceria (8YSZ + 4CeO2 were grown by pulsed laser deposition (PLD technique using 8YSZ and 8YSZ + 4CeO2 targets and a Nd-YAG laser (355 nm. Films have been deposited on Soda-Calcia-Silica glass and Si(100 substrates at room temperature. The morphology and structural characteristics of the samples have been studied by means of X-ray diffraction and scanning electron microscopy. Films of a cubic-YSZ single phase with thickness in the range of 1-3 µm were grown on different substrates.

  5. Yttria and ceria doped zirconia thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Saporiti, F.; Juarez, R. E., E-mail: cididi@fi.uba.ar [Grupo de Materiales Avanzados, Facultad de Ingenieria, Universidad de Buenos Aires (Argentina); Audebert, F. [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Boudard, M. [Laboratoire des Materiaux et du Genie Physique (CNRS), Grenoble (France)

    2013-11-01

    The Yttria stabilized Zirconia (YSZ) is a standard electrolyte for solid oxide fuel cells (SOFCs), which are potential candidates for next generation portable and mobile power sources. YSZ electrolyte thin films having a cubic single phase allow reducing the SOFC operating temperature without diminishing the electrochemical power density. Films of 8 mol% Yttria stabilized Zirconia (8YSZ) and films with addition of 4 weight% Ceria (8YSZ + 4CeO{sub 2}) were grown by pulsed laser deposition (PLD) technique using 8YSZ and 8YSZ + 4CeO{sub 2} targets and a Nd-YAG laser (355 nm). Films have been deposited on Soda-Calcia-Silica glass and Si(100) substrates at room temperature. The morphology and structural characteristics of the samples have been studied by means of X-ray diffraction and scanning electron microscopy. Films of a cubic-YSZ single phase with thickness in the range of 1-3 Micro-Sign m were grown on different substrates (author)

  6. Thermal Conductivity of Alumina-reinforced Zirconia Composites

    Science.gov (United States)

    Bansal, Narottam P.

    2005-01-01

    10-mol% yttria-stabilized zirconia (10SZ) - alumina composites containing 0-30 mol% alumina were fabricated by hot pressing at 1500 C in vacuum. Thermal conductivity was determined at various temperatures using a steady-state laser heat flux technique. Thermal conductivity of the composites increased with increase in alumina content. Composites containing 0, 5, and 10-mol% alumina did not show any change in thermal conductivity with temperature. However, those containing 20 and 30-mol% alumina showed a decrease in thermal conductivity with increase in temperature. The measured values of thermal conductivity were in good agreement with those calculated from the Maxwell-Eucken model where one phase is uniformly dispersed within a second major continuous phase.

  7. Comprehensive study of the effect of the irradiation temperature on the behavior of cubic zirconia

    Science.gov (United States)

    Debelle, A.; Channagiri, J.; Thomé, L.; Décamps, B.; Boulle, A.; Moll, S.; Garrido, F.; Behar, M.; Jagielski, J.

    2014-05-01

    Cubic zirconia single-crystals (yttria-stabilized zirconia (YSZ)) have been irradiated with 4 MeV Au2+ ions in a broad fluence range (namely from 5 × 1012 to 2 × 1016 cm-2) and at five temperatures: 80, 300, 573, 773, and 1073 K. Irradiated samples have been characterized by Rutherford backscattering spectroscopy in channeling mode, X-ray diffraction and transmission electron microscopy techniques in order to determine the disordering kinetics. All experimental results show that, whatever is the irradiation temperature, the damage build-up follows a multi-step process. In addition, the disorder level at high fluence is very similar for all temperatures. Thus, no enhanced dynamic annealing process is observed. On the other hand, transitions in the damage accumulation process occur earlier in fluence with increasing temperature. It is shown that temperature as low as 573 K is sufficient to accelerate the disordering process in ion-irradiated YSZ.

  8. Microstructure and properties of composite of stainless steel and partially stabilized zirconia

    Institute of Scientific and Technical Information of China (English)

    张文泉; 谢建新; 杨志国; 王从曾

    2003-01-01

    To fabricate the metal-ceramics multi-layer hollow functionally gradient materials(FGMs) that mightmeet the requirement of repeated service and long working time of high temperature burners, such as spacecraft en-gine, the microstructure and properties of composite of stainless steel and partially stabilized zirconia were investiga-ted. Samples of different proportions of stainless steel to partially yttria-stabilized zirconia were fabricated by powderextrusion and sintering method. Shrinkage, relative density, microstructure, micro-Vickers hardness, compressionstrength, bending strength, fractography morphology and electrical resistivity of sintered samples with differentproportions of stainless steel were measured. The results show that threshold of metallic matrix composite(MMC)is approximately equal to 60 % (volume fraction) stainless steel. The samples with 0 to 50% (volume fraction) stain-less steel indicate ceramic brittleness and non cutability, and the samples with 70% to 100% (volume fraction) stain-less steel indicate metallic plasticity and cutability.

  9. Mixed zirconia calcium phosphate coatings for dental implants: Tailoring coating stability and bioactivity potential

    Energy Technology Data Exchange (ETDEWEB)

    Pardun, Karoline [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany); Treccani, Laura, E-mail: treccani@uni-bremen.de [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany); Volkmann, Eike [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany); Streckbein, Philipp [University Hospital, Justus-Liebig-University Giessen, Department of Cranio-Maxillo-Facial Surgery, Klinikstrasse 33, 35385 Giessen (Germany); Heiss, Christian [University Hospital of Giessen-Marburg, Department of Trauma Surgery, Rudolf-Buchheim-Strasse 7, 35385 Giessen, Germany, (Germany); Laboratory of Experimental Surgery, Kerkraderstrasse 9, 35392 Giessen (Germany); Destri, Giovanni Li; Marletta, Giovanni [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemistry, University of Catania and CSGI, Viale A. Doria 6, 95125 Catania (Italy); Rezwan, Kurosch [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany)

    2015-03-01

    Enhanced coating stability and adhesion are essential for long-term success of orthopedic and dental implants. In this study, the effect of coating composition on mechanical, physico-chemical and biological properties of coated zirconia specimens is investigated. Zirconia discs and dental screw implants are coated using the wet powder spraying (WPS) technique. The coatings are obtained by mixing yttria-stabilized zirconia (TZ) and hydroxyapatite (HA) in various ratios while a pure HA coating served as reference material. Scanning electron microscopy (SEM) and optical profilometer analysis confirm a similar coating morphology and roughness for all studied coatings, whereas the coating stability can be tailored with composition and is probed by insertion and dissections experiments in bovine bone with coated zirconia screw implants. An increasing content of calcium phosphate (CP) resulted in a decrease of mechanical and chemical stability, while the bioactivity increased in simulated body fluid (SBF). In vitro experiments with human osteoblast cells (HOB) revealed that the cells grew well on all samples but are affected by dissolution behavior of the studied coatings. This work demonstrates the overall good mechanical strength, the excellent interfacial bonding and the bioactivity potential of coatings with higher TZ contents, which provide a highly interesting coating for dental implants. - Highlights: • Different ratios of zirconia (TZ) and calcium phosphate (CP) were deposited on zirconia substrates. • Enhancement of TZ content in mixed coatings increased coating stability. • Enhancement of CP content in mixed coatings increased bioactivity. • All tested coating compositions were non-toxic.

  10. Magnesium-containing mixed coatings on zirconia for dental implants: mechanical characterization and in vitro behavior.

    Science.gov (United States)

    Pardun, Karoline; Treccani, Laura; Volkmann, Eike; Streckbein, Philipp; Heiss, Christian; Gerlach, Juergen W; Maendl, Stephan; Rezwan, Kurosch

    2015-07-01

    An important challenge in the field of dental and orthopedic implantology is the preparation of implant coatings with bioactive functions that feature a high mechanical stability and at the same time mimic structural and compositional properties of native bone for a better bone ingrowth. This study investigates the influence of magnesium addition to zirconia-calcium phosphate coatings. The mixed coatings were prepared with varying additions of either magnesium oxide or magnesium fluoride to yttria-stabilized zirconia and hydroxyapatite. The coatings were deposited on zirconia discs and screw implants by wet powder spraying. Microstructure studies confirm a porous coating with similar roughness and firm adhesion not hampered by the coating composition. The coating morphology, mechanical flexural strength and calcium dissolution showed a magnesium content-dependent effect. Moreover, the in vitro results obtained with human osteoblasts reveal an improved biological performance caused by the presence of Mg(2+) ions. The magnesium-containing coatings exhibited better cell proliferation and differentiation in comparison to pure zirconia-calcium phosphate coatings. In conclusion, these results demonstrate that magnesium addition increases the bioactivity potential of zirconia-calcium phosphate coatings and is thus a highly suitable candidate for bone implant coatings.

  11. Crystallization of zirconia based thin films.

    Science.gov (United States)

    Stender, D; Frison, R; Conder, K; Rupp, J L M; Scherrer, B; Martynczuk, J M; Gauckler, L J; Schneider, C W; Lippert, T; Wokaun, A

    2015-07-28

    The crystallization kinetics of amorphous 3 and 8 mol% yttria stabilized zirconia (3YSZ and 8YSZ) thin films grown by pulsed laser deposition (PLD), spray pyrolysis and dc-magnetron sputtering are explored. The deposited films were heat treated up to 1000 °C ex situ and in situ in an X-ray diffractometer. A minimum temperature of 275 °C was determined at which as-deposited amorphous PLD grown 3YSZ films fully crystallize within five hours. Above 325 °C these films transform nearly instantaneously with a high degree of micro-strain when crystallized below 500 °C. In these films the t'' phase crystallizes which transforms at T > 600 °C to the t' phase upon relaxation of the micro-strain. Furthermore, the crystallization of 8YSZ thin films grown by PLD, spray pyrolysis and dc-sputtering are characterized by in situ XRD measurements. At a constant heating rate of 2.4 K min(-1) crystallization is accomplished after reaching 800 °C, while PLD grown thin films were completely crystallized already at ca. 300 °C.

  12. Long-term stability and properties of zirconia ceramics for heavy duty diesel engine components

    Science.gov (United States)

    Larsen, D. C.; Adams, J. W.

    1985-01-01

    Physical, mechanical, and thermal properties of commercially available transformation-toughened zirconia are measured. Behavior is related to the material microstructure and phase assemblage. The stability of the materials is assessed after long-term exposure appropriate for diesel engine application. Properties measured included flexure strength, elastic modulus, fracture toughness, creep, thermal shock, thermal expansion, internal friction, and thermal diffusivity. Stability is assessed by measuring the residual property after 1000 hr/1000C static exposure. Additionally static fatigue and thermal fatigue testing is performed. Both yttria-stabilized and magnesia-stabilized materials are compared and contrasted. The major limitations of these materials are short term loss of properties with increasing temperature as the metastable tetragonal phase becomes more stable. Fine grain yttria-stabilized material (TZP) is higher strength and has a more stable microstructure with respect to overaging phenomena. The long-term limitation of Y-TZP is excessive creep deformation. Magnesia-stabilized PSZ has relatively poor stability at elevated temperature. Overaging, decomposition, and/or destabilization effects are observed. The major limitation of Mg-PSZ is controlling unwanted phase changes at elevated temperature.

  13. Effect of high thermal expansion glass infiltration on mechanical properties of alumina–zirconia composite

    Indian Academy of Sciences (India)

    A Balakrishnan; B B Panigrahi; K P Sanosh; Min-Cheol Chu; T N Kim; Seong-Jai Cho

    2009-08-01

    This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature. This could be attributed to the drastic drop in the coefficient of thermal expansion due to the compositional change in the soda lime glass during infiltration. There was a significant improvement in the Weibull modulus after glass infiltration. Glass infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the penetrated glass.

  14. Fermi Potential across Working Solid Oxide Cells with Zirconia or Ceria Electrolytes

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    Two kinds of electrochemical relevant potentials are important in order to describe several observed phenomena in operating electrochemical cells with solid electrolytes. This paper gives illustrative examples of how the profiles of the two potential types, the Galvani potential, φ......, and the electromotive – also called the Fermi potential, π, will vary across the electrolyte, and of how the electron leak current density though the electrolyte, which is related to π, will be affected by temperature and cell voltage across the electrolyte in cells based on gadolinia doped ceria (CGO) and on yttria...... stabilized zirconia (YSZ) electrolytes. The nature of the two potential types and the importance of each of them for the cell operation are explained....

  15. Fermi Potential across Working Solid Oxide Cells with Zirconia or Ceria Electrolytes

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    A solid electrolyte will always possess a finite electronic conductivity, in particular electrolytes like doped ceria that easily get reduced and become mixed ionic and electronic conductors. This given rise too high leak currents through the solid oxide cell (SOC). Especially, problems have been...... observed for ceria based electrolytes, but also in case of solid oxide electrolyser cells (SOEC) with yttria stabilized zirconia (YSZ) big electronic leak currents have been observed for very high overvoltages on one or both electrodes. Furthermore, it is important to realize that the potential gradient...... driving the O2-ions is not the Fermi potential, which is the potential of the electrons, but the Galvani potential (or inner potential) (1). The concepts of potentials describing the electrical situation of a solid electrolyte is shown i Fig. 1, and an example of the Fermi potential (π) and Galvani...

  16. Fermi Potential across Working Solid Oxide Cells with Zirconia or Ceria Electrolytes

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    A solid electrolyte will always possess a finite electronic conductivity, in particular electrolytes like doped ceria that easily get reduced and become mixed ionic and electronic conductors. This given rise too high leak currents through the solid oxide cell (SOC). Especially, problems have been...... observed for ceria based electrolytes, but also in case of solid oxide electrolyser cells (SOEC) with yttria stabilized zirconia (YSZ) big electronic leak currents have been observed for very high overvoltages on one or both electrodes. Furthermore, it is important to realize that the potential gradient...... at various temperatures and operation conditions. Furthermore, the situation within cells based on gadolinia doped ceria (CGO) and on YSZ electrolytes are compared. Finally, it is discussed how the Fermi potential and electron conductivity will be affected by the various parameters including operation...

  17. Influence of dopant ion on localized relaxation of an oxygen vacancy in stabilized zirconia

    Science.gov (United States)

    Ohta, M.; Wigmore, J. K.; Nobugai, K.; Miyasato, T.

    2002-05-01

    It is well known that stabilized zirconia exhibits long-range transport of oxygen ions which gives rise to diffusion relaxation of oxygen vacancies. The internal friction and the change in sound velocity in single-crystal calcia-stabilized zirconia (CSZ) doped with 12 mol % CaO were measured for longitudinal sound waves in the frequency range from 20 Hz to 700 Hz using a vibrating reed technique. In the temperature range from 300 K to 700 K, the relaxation strength exhibits strong anisotropy with respect to the directions of the k vectors. As the frequency increases the internal friction peak and the change in sound velocity shift toward high temperature, and the relaxation strength remains constant. The results show that a smaller number of oxygen vacancies contribute to diffusion relaxation than to localized relaxation, which is attributed to hopping of bound oxygen vacancies within the local structure. Comparison of the results with those reported previously for yttria-stabilized zirconia (YSZ) doped with 9.5 mol % Y2O3, suggests that oxygen vacancies are more strongly bound by the local structure in CSZ than in YSZ.

  18. Processing of Transparent Rare Earth Doped Zirconia for High Temperature Light Emission Applications

    Science.gov (United States)

    Hardin, Corey Lee

    The high fracture toughness of stabilized zirconia makes it one of the most widely applicable high temperature structural materials. However, it is not typicality considered for optical applications since the microstructure achieved by traditional processing makes it opaque. The aim of this dissertation is to develop processing methods for the introducing new functionalities of light transparency and light emission (photoluminescence) and to understand the nanostructure-property relationships that make these functionalities possible. A processing study of rare-earth (RE) doped Zirconium Oxide (ZrO2, zirconia) via Current Activated Pressure Assisted Densification (CAPAD) is presented. The role of processing temperature and dopant concentration on the crystal structure, microstructure and properties of the RE: ZrO2 is studied. Microstructural shows sub-100 nm grain size and homogeneous dopant distribution. X-ray diffraction and Raman analysis show that with increased dopant concentration the material changes from monoclinic to tetragonal. Structural analysis shows the material shows high hardness and toughness values 30% greater than similarly processed yttria-stabilized zirconia. Despite birefringence in the tetragonal phase, optical characterization is presented showing the samples are both highly transparent and photo-luminescent. Special attention is paid to analyzing structural and photoluminescence development during densification, as well as the role of oxygen vacancies on the optical properties of the densified material. This material is shown to be a promising candidate for a number of applications including luminescence thermometry and high temperature light emission.

  19. Load-bearing capacity of all-ceramic posterior four-unit fixed partial dentures with different zirconia frameworks.

    Science.gov (United States)

    Kohorst, Philipp; Herzog, Timo J; Borchers, Lothar; Stiesch-Scholz, Meike

    2007-04-01

    The aim of this in vitro study was to compare the load-bearing capacity of posterior four-unit fixed partial dentures (FPDs) produced with two different yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP) ceramics, one being a presintered material, the other a fully sintered, hot isostatically pressed material. Additionally, as a novel approach, the influence of preliminary mechanical damage upon the fracture force of an FPD has been investigated. A total of 20 frameworks each were milled from presintered zirconia and from fully sintered zirconia. Prior to veneering, 10 frameworks of each material were 'damaged' by a defined saw cut similar to an accidental flaw generated during shape cutting. Before fracture testing, all FPDs were subjected to thermal and mechanical cycling. Additionally, scanning electron microscopy was used to investigate fracture surfaces. Statistical analysis showed that FPDs milled from fully sintered zirconia had a significantly higher fracture resistance compared with specimens made from presintered material, whereas preliminary damage did not have a significant effect. After aging, FPDs made from both materials were capable of withstanding occlusal forces reported in the literature. Therefore, both types of Y-TZP may be suitable for posterior four-unit all-ceramic FPDs, although further prolonged aging experiments and prospective clinical trials are required to prove their fitness for clinical use.

  20. Determination of strain and damage profiles in irradiated materials: Application to cubic zirconia irradiated at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Channagiri, J. [Science des Procédés Céramiques et Traitements de Surface, CNRS UMR 7315, Centre Européen de la Céramique, 12 rue atlantis, 87068 Limoges Cedex (France); Boulle, A., E-mail: alexandre.boulle@unilim.fr [Science des Procédés Céramiques et Traitements de Surface, CNRS UMR 7315, Centre Européen de la Céramique, 12 rue atlantis, 87068 Limoges Cedex (France); Debelle, A. [Centre de Sciences Nucléaires et Sciences de la Matière, Université Paris-Sud, CNRS-IN2P3, 91405 Orsay Cedex (France)

    2014-05-01

    A methodology is presented that allows to retrieve strain and damage profiles in irradiated single crystals. The approach makes use of high-resolution X-ray diffraction θ–2θ scans coupled with numerical simulations of the diffraction profiles. The potential of the method is illustrated with cubic yttria-stabilized zirconia single crystals, irradiated with 4 MeV Au{sup 2+} ions at different temperatures (25, 500 and 800 °C). The simulations reveal that upon increasing ion fluence, the width of the damaged region increases and both the strain and damage levels inside this region increase. The damage build-up occurs according to a two-step mechanism: in the first step, the damage increases slowly up to a critical fluence, above which the second step takes place and is characterized by dramatic increase of the damage. The transition fluence is shifted towards lower values at higher temperatures.

  1. Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings

    Science.gov (United States)

    Abbas, Musharaf; Hasham, Hasan Junaid; Baig, Yasir

    2016-02-01

    Numerical-based finite element investigation has been conducted to explain the effect of bond coat thickness on stress distribution in traditional and nanostructured yttria-stabilized zirconia (YSZ)-based thermal barrier coatings (TBC). Stress components have been determined to quantitatively analyze the mechanical response of both kinds of coatings under the thermal shock effect. It has been found that maximum radial tensile and compressive stresses that exist at thermally grown oxide (TGO)/bond coat interface and within TGO respectively decrease with an increase in bond coat thickness. Effect of bond coat thickness on axial tensile stresses is not significant. However, axial compressive stresses that exist at the edge of the specimen near bond coat/substrate interface decrease appreciably with the increase in bond coat thickness. Residual stress profile as a function of bond coat thickness is further explained for comparative analysis of both coatings to draw some useful conclusions helpful in failure studies of TBCs.

  2. Effect of different laser surface treatment on microshear bond strength between zirconia ceramic and resin cement.

    Science.gov (United States)

    Akhavan Zanjani, Vagharaldin; Ahmadi, Hadi; Nateghifard, Afshin; Ghasemi, Amir; Torabzadeh, Hassan; Abdoh Tabrizi, Maryam; Alikhani, Farnaz; Razi, Reza; Nateghifard, Ardalan

    2015-11-01

    The purpose of this study was to evaluate the effect of sandblasting, carbon dioxide (CO₂), and erbium,chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers on the microshear bond strength of zirconia to resin cement. Sixty-one sintered yttria stabilized tetragonal zirconia blocks (10 × 5 × 2 mm) were prepared and divided into four experimental groups (n = 15); one sample was retained as a control. The samples were treated by aluminium oxide air abrasion, CO₂4W, Er,Cr:YSGG 3W, and Er,Cr:YSGG 2W, respectively. One sample from each group and the control sample were analyzed by scanning electron microscope. Panavia F2.0 resin microcylinders were prepared and placed on treated surfaces, light cured, and incubated for 48 h. Microshear bond strength testing was done by a microtensile tester machine, and the type of bond failures were determined by stereomicroscope. Data were analyzed by one-way anova and Tukey's test at a significance level of P laser showed significantly higher bond strength than Er,Cr:YSGG 2W (P laser-treated surfaces, the roughness was much less than the air abrasion-treated surfaces, and the mode of failure was almost pure adhesive. Air abrasion has a greater effect than CO₂and Er,Cr:YSGG lasers in the treatment of zirconia ceramic surfaces to enhance the bonding strength of resin cement to zirconia. CO₂laser at 4W and Er,Cr:YSGG laser at only 3-W output power can be regarded as surface treatment options for roughening the zirconia surface to establish better bond strength with resin cements. © 2014 Wiley Publishing Asia Pty Ltd.

  3. Effect of Three Different Core Materials on Masking Ability of a Zirconia Ceramic

    Directory of Open Access Journals (Sweden)

    Farhad Tabatabaian

    2016-12-01

    Full Text Available Objectives: Masking ability of a restorative material plays a role in hiding colored substructures; however, the masking ability of zirconia ceramic (ZRC has not yet been clearly understood in zirconia-based restorations. This study evaluated the effect of three different core materials on masking ability of a ZRC.Materials and Methods: Ten zirconia disc samples, 0.5mm in thickness and 10mm in diameter, were fabricated. A white (W substrate (control and three substrates of nickel-chromium alloy (NCA, non-precious gold alloy (NPGA, and ZRC were prepared. The zirconia discs were placed on the four types of substrates for spectrophotometry. The L*, a*, and b* values of the specimens were measured by a spectrophotometer and color change (ΔE values were calculated to determine color differences between the test and control groups and were then compared with the perceptual threshold. Randomized block ANOVA and Bonferroni test analyzed the data. A significance level of 0.05 was considered.Results: The mean and standard deviation values of ΔE for NCA, NPGA, and ZRC groups were 10.26±2.43, 9.45±1.74, and 6.70±1.91 units, respectively. Significant differences were found in the ΔE values between ZRC and the other two experimental groups (NCA and NPGA; P<0.0001 and P=0.001, respectively. The ΔE values for the groups were more than the predetermined perceptual threshold.Conclusions: Within the limitations of this study, it was concluded that the tested ZRC could not well mask the examined core materials.Keywords: Color; Spectrophotometry; Visual Perception; Yttria Stabilized Tetragonal Zirconia

  4. Monoclinic phase transformation and mechanical durability of zirconia ceramic after fatigue and autoclave aging.

    Science.gov (United States)

    Mota, Yasmine A; Cotes, Caroline; Carvalho, Rodrigo F; Machado, João P B; Leite, Fabíola P P; Souza, Rodrigo O A; Özcan, Mutlu

    2017-10-01

    This study evaluated the influence of two aging procedures on the biaxial flexural strength of yttria-stabilized tetragonal zirconia ceramics. Disc-shaped zirconia specimens and (ZE: E.max ZirCAD, Ivoclar; ZT: Zirkon Translucent, Zirkonzahn) (N = 80) (∅:12 mm; thickness:1.2 mm, ISO 6872) were prepared and randomly divided into four groups (n = 10 per group) according to the aging procedures: C: Control, no aging; M: mechanical cycling (2 × 10(6) cycles/3.8 Hz/200 N); AUT: Aging in autoclave at 134°C, 2 bar for 24 h; AUT + M: Autoclave aging followed by mechanical cycling. After aging, the transformed monoclinic zirconia (%) were evaluated using X-ray diffraction and surface roughness was measured using atomic force microscopy. The average grain size was measured by scanning electron microscopy and the specimens were submitted to biaxial flexural strength testing (1 mm/min, 1000 kgf in water). Data (MPa) were statistically analyzed using 2-way analysis of variance and Tukey's test (α = 0.05). Aging procedures significantly affected (p = 0.000) the flexural strength data but the effect of zirconia type was not significant (p = 0.657). AUTZT (936.4 ± 120.9(b) ) and AUT + MZE (867.2 ± 49.3(b) ) groups presented significantly higher values (p autoclave aging alone or with mechanical aging increased the flexure strength but also induced higher transformation from tetragonal to monoclinic phase in both zirconia materials tested. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1972-1977, 2017. © 2016 Wiley Periodicals, Inc.

  5. Obtention of zirconia films stabilized with Yttria via pyrolysis spray: study of the solvent influence; Obtencao de filmes de zirconia estabilizada com itria via spray pirolise: estudo da influencia do solvente

    Energy Technology Data Exchange (ETDEWEB)

    Halmenschlager, Cibele Melo; Vieira, Ramaugusto da Porciuncula; Takimi, Antonio Shigueaki; Bergmann, Carlos Perez; Silva, Aline Lima da; Malfatti, Celia de Fraga [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais (PPGEM). Lab. de Materiais Ceramicos (LACER)]. E-mail: cibelemh@yahoo.com.br

    2008-07-01

    Yttria-stabilized-zirconia (YSZ) has been object of many studies, due to its great chemical stability and excellent ionic conduction in high temperature. This material has been studies with an intention of to be used with electrolyte of oxide solid fuel cells, which work in high temperature. The aim of the present work was to evaluate the influence of the solvent on the elaboration of crystalline films of YSZ via spray pyrolysis. The film was prepared by spray pyrolysis with zirconium acetylacetonate (Zr(C{sub 6}H{sub 7}O{sub 2}){sub 4}) and yttrium chloride (YCl{sub 3}.6H{sub 2}O), dissolved in different solvents: ethanol (C{sub 2}H{sub 6}O), ethanol (C{sub 2}H{sub 6}O) + propyleneglycol (C{sub 3}H{sub 8}O{sub 2}) with volume ratio (1:1) and ethanol (C{sub 2}H{sub 6}O) + diethylene glycol butyl ether (C{sub 8}H{sub 18}O{sub 3}) with volume ratio of 1:1. A disk of steel 316L was used as substrate. The amorphous film was deposited in the substrate heated at 280 deg C {+-} 50 deg C. After deposition from thermal treatment at 700 deg C the amorphous film was changed into Yttria-stabilized-zirconia film. The thermal behavior of the films has been studied by both (DTA/TGA) thermogravimetric and mass spectroscopy analyses. The morphology and crystalline phase of the films was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The YSZ film obtained after heat treatment was dense and crystalline, however, the analyses indicate a significant influence of the solvent and of the substrate temperature during the deposition process on the film morphology.(author)

  6. Thermomechanical behavior of plasma-sprayed zirconia thermal barrier coatings.

    Energy Technology Data Exchange (ETDEWEB)

    Singh, J. P.

    1998-04-01

    The effect of coating porosity and thickness on the resistance to damage of yttria stabilized zirconia thermal barrier coatings in an oxidizing environment by thermal cycling was evaluated. Hardness and elastic modulus of an as-processed porous coating were lower than those of a dense coating and the porous coating failed after fewer thermal cycles. Similarly, specimen with a thicker coating failed after fewer thermal cycles than specimen with a thinner coating. The earlier failure of the porous coating is due to lower fracture toughness and enhanced oxidation of the coating/substrate interface, whereas, the earlier failure of the thick coating is due to higher thermal transient stresses that developed in the coating during thermal cycling. Generally, an increase in coating density led to initial increase in both hardness and elastic modulus with increasing thermal cycles. However, hardness and density gradually decreased as the number of thermal cycles increase because of microcracks formation and growth. Microscopic observations indicated that the formation of multiple microcracks and their subsequent growth and coalescence led to final coating failure.

  7. High-temperature zirconia microthruster with an integrated flow sensor

    Science.gov (United States)

    Lekholm, Ville; Persson, Anders; Palmer, Kristoffer; Ericson, Fredric; Thornell, Greger

    2013-05-01

    This paper describes the design, fabrication and characterization of a ceramic, heated cold-gas microthruster device made with silicon tools and high temperature co-fired ceramic processing. The device contains two opposing thrusters, each with an integrated calorimetric propellant flow sensor and a heater in the stagnation chamber of the nozzle. The exhaust from a thruster was photographed using schlieren imaging to study its behavior and search for leaks. The heater elements were tested under a cyclic thermal load and to the maximum power before failure. The nozzle heater was shown to improve the efficiency of the thruster by 6.9%, from a specific impulse of 66 to 71 s, as calculated from a decrease of the flow rate through the nozzle of 13%, from 44.9 to 39.2 sccm. The sensitivity of the integrated flow sensor was measured to 0.15 mΩ sccm-1 in the region of 0-15 sccm and to 0.04 mΩ sccm-1 above 20 sccm, with a zero-flow sensitivity of 0.27 mΩ sccm-1. The choice of yttria-stabilized zirconia as a material for the devices makes them robust and capable of surviving temperatures locally exceeding 1000 °C.

  8. Modifying zirconia solid electrolyte surface property to enhance oxide transport

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, B.Y.; Song, S.Y. [Univ. of Hawaii, Honolulu, HI (United States)

    1996-12-31

    Bismuth-strontium-calcium-copper oxide (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, BSCCO) is known for its high T{sub c} superconducting behavior and mixed conducting property. The applicability of similar high T{sub c} cuprates for intermediate-temperature solid oxide fuel cell (SOFC) application has been studied recently. We investigated the electrochemical behavior of several Ag{vert_bar}BSCCO{vert_bar}10 mol% yttria-stabilized zirconia (YSZ){vert_bar}Ag and Ag{vert_bar}YSZ{vert_bar}Ag cells using complex impedance spectroscopy. A highly uniform and porous microstructure was observed at the interface of the YSZ and BSCCO. The ionic conductivity determined from the Nyquest plots in the temperature range of 200-700{degrees}C agrees with the values reported in the literature. The specific resistance of the BSCCO{vert_bar}YSZ interface was also determined to be lower than those of the conventional manganite electrode, suggesting that BSCCO seems attractive for cathode applications in SOFC.

  9. Thermal conductivity of zirconia based inert matrix fuel: use and abuse of the formal models for testing new experimental data

    Science.gov (United States)

    Degueldre, C.; Arima, T.; Lee, Y. W.

    2003-06-01

    An inert matrix fuel material based on yttria-stabilized cubic zirconia: Er xY yPu zZr 1- x- y- zO 2-( x + y)/2 ( x+ y=0.15, z: [0.05-0.15]) was proposed for burning excess plutonium in light water reactors. The studied inert matrix fuel is made of cubic stabilized zirconia. The limited number of experimental thermal conductivity data justifies this formal and intensive study. Approaches derived from Klemens theory were revisited and the derived conductivity model applied for zirconia, accounting the effects of phononic scattering centers. The hyperbolic thermal conductivity trend with temperature known for pure zirconia, is reduced by isotopes, impurities, dopants and oxygen vacancies, which act as scattering centers and contribute to conductivity reduction to a flat plot with temperature for stabilized zirconia. It is experimentally observed that the thermal conductivity derived from laser flash measurements for Er xY yM zZr 1- x- y- zO 2-( x + y)/2 (with M=Ce or Pu, z=0 or ˜0.1 and x+ y=0.15) is rather constant as a function of temperature in the range 300-1000 K. The thermal conductivity was observed to depend on the concentration of dopants such as YO 1.5 and/or ErO 1.5, CeO 2 (analogous of PuO 2) or PuO 2. The bulk material conductivity of Er 0.05Y 0.10Pu 0.10Zr 0.75O 1.925 is about 2 W m -1 K -1. In this study, the thermal conductivity data of both monoclinic and stabilized cubic zirconia based IMF are tested with the model approach in order to understand the experimental data in a semi-quantitative way.

  10. Dipentaerythritol penta-acrylate phosphate - an alternative phosphate ester monomer for bonding of methacrylates to zirconia

    Science.gov (United States)

    Chen, Ying; Tay, Franklin R.; Lu, Zhicen; Chen, Chen; Qian, Mengke; Zhang, Huaiqin; Tian, Fucong; Xie, Haifeng

    2016-12-01

    The present work examined the effects of dipentaerythritol penta-acrylate phosphate (PENTA) as an alternative phosphate ester monomer for bonding of methacrylate-based resins to yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and further investigated the potential bonding mechanism involved. Shear bond strength testing was performed to evaluate the efficacy of experimental PENTA-containing primers (5, 10, 15, 20 or 30 wt% PENTA in acetone) in improving resin-Y-TZP bond strength. Bonding without the use of a PENTA-containing served as the negative control, and a Methacryloyloxidecyl dihydrogenphosphate(MDP)-containing primer was used as the positive control. Inductively coupled plasma-mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were used to investigate the potential existence of chemical affinity between PENTA and Y-TZP. Shear bond strengths were significant higher in the 15 and 20 wt% PENTA groups. The ICP-MS, XPS and FTIR data indicated that the P content on the Y-TZP surface increased as the concentration of PENTA increased in the experimental primers, via the formation of Zr–O–P bond. Taken together, the results attest that PENTA improves resin bonding of Y-TZP through chemical reaction with Y-TZP. Increasing the concentration of PENTA augments its binding affinity but not its bonding efficacy with zirconia.

  11. Comprehensive study of the effect of the irradiation temperature on the behavior of cubic zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Debelle, A., E-mail: aurelien.debelle@u-psud.fr; Thomé, L.; Décamps, B.; Moll, S.; Garrido, F. [Centre de Sciences Nucléaires et de Sciences de la Matière, Univ. Paris-Sud, CNRS/IN2P3, 91405 Orsay (France); Channagiri, J.; Boulle, A. [Science des Procédés Céramiques et Traitements de Surface, CNRS UMR 7315, Centre Européen de la Céramique, 12 rue atlantis, 87068 Limoges Cedex (France); Behar, M. [Instituto de Física, Universidade Federal do Rio Grande do Sul, C.P. 15051, 91501-970 Porto Alegre, RS (Brazil); Jagielski, J. [Institute for Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); The Andrzej Soltan Institute for Nuclear Studies, 05-400 Swierk/Otwock (Poland)

    2014-05-14

    Cubic zirconia single-crystals (yttria-stabilized zirconia (YSZ)) have been irradiated with 4 MeV Au{sup 2+} ions in a broad fluence range (namely from 5 × 10{sup 12} to 2 × 10{sup 16} cm{sup −2}) and at five temperatures: 80, 300, 573, 773, and 1073 K. Irradiated samples have been characterized by Rutherford backscattering spectroscopy in channeling mode, X-ray diffraction and transmission electron microscopy techniques in order to determine the disordering kinetics. All experimental results show that, whatever is the irradiation temperature, the damage build-up follows a multi-step process. In addition, the disorder level at high fluence is very similar for all temperatures. Thus, no enhanced dynamic annealing process is observed. On the other hand, transitions in the damage accumulation process occur earlier in fluence with increasing temperature. It is shown that temperature as low as 573 K is sufficient to accelerate the disordering process in ion-irradiated YSZ.

  12. Novel erbia-yttria co-doped zirconia fluorescent thermal history sensor

    Science.gov (United States)

    Copin, E. B.; Massol, X.; Amiel, S.; Sentenac, T.; Le Maoult, Y.; Lours, P.

    2017-01-01

    Thermochromic pigments are commonly used for off-line temperature mapping on components from systems operating at a temperature higher than 1073 K. However, their temperature resolution is often limited by the discrete number of color transitions they offer. This paper investigates the potential of erbia-yttria co-doped zirconia as a florescent thermal history sensor alternative to thermochromic pigments. Samples of yttria-stabilized zirconia powder (YSZ, 8.3 mol% YO1.5) doped with 1.5 mol% ErO1.5 and synthesized by a sol-gel route are calcined for 15 minutes under isothermal conditions between 1173 and 1423 K. The effects of temperature on their crystal structure and room temperature fluorescence properties are then studied. Results show a steady increase of the crystallinity of the powders with temperature, causing a significant and permanent increase of the emission intensity and fluorescence lifetime which could be used to determine temperature with a calculated theoretical resolution lower than 1 K for intensity. The intensity ratio obtained using a temperature insensitive YSZ:Eu3+ reference phosphor is proposed as a more robust parameter regarding experimental conditions for determining thermal history. Finally, the possibilities for integrating this fluorescent marker into sol-gel deposited coatings for future practical thermal history sensing applications is also discussed.

  13. Influence of characteristics of stabilized zirconia electrolyte on performance of cermet supported tubular SOFCs

    Institute of Scientific and Technical Information of China (English)

    LI Changjiu; LI Chengxin; XING Yazhe; XIE Yingxin; LONG Huiguo

    2006-01-01

    Ni-Al2O3 cermet supported tubular SOFC was fabricated by thermal spraying. Flame-sprayed Al2O3-Ni cermet coating plays dual roles of a support tube and an anode current collector. 4.5mol.% yttria-stabilized zirconia (YSZ) and 10mol.% scandia-stabilized zirconia (ScSZ) coatings were deposited by atmospheric plasma spraying (APS) as the electrolyte in present study. The electrical conductivity of electrolyte was measured using DC method. The post treatment was employed using nitrate solution infiltration to densify APS electrolyte layer for improvement of gas permeability. The electrical conductivity of electrolyte and the performance of single cell were investigated to optimize SOFC performance. The electrical conductivity of the as-sprayed YSZ and ScSZ coating is about 0.03 and 0.07 S·cm-1 at 1000 ℃, respectively. The ohmic polarization significantly influences the performance of SOFC. The maximum output power density at 1000 ℃ increases from 0.47 to 0.76 W·cm-2 as the YSZ electrolyte thickness reduces from 100 μm to 40 μm. Using APS ScSZ coating of about 40 μm as the electrolyte, the test cell presents a maximum power output density of over 0.89 W·m-2 at 1000 ℃.

  14. Synthesis and ceramic processing of zirconia alumina composites for application as solid oxide fuel cell electrolytes; Sintese e processamento de compositos de zirconia-alumina para aplicacao como eletrolito em celulas a combustivel de oxido solido

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Rafael Henrique Lazzari

    2007-07-01

    The global warmness and the necessity to obtain clean energy from alternative methods than petroleum raises the importance of developing cleaner and more efficient systems of energy generation, among then, the solid oxide fuel cell (SOFC). Cubic stabilized zirconia (CSZ) has been the most studied material as electrolyte in SOFC, due to its ionic conductivity and great stability at operation conditions. However, its low fracture toughness difficulties its application as a thin layer, what could lead to an improvement of cell efficiency. In this sense, the alumina addition in CSZ forms a composite, which can shift its mechanical properties, without compromising its electrical properties. In this work, coprecipitation synthesis route and ceramic processing of zirconia-alumina composites were studied, in order to establish optimum conditions to attain high density, homogeneous microstructure, and better mechanical properties than CSZ, without compromising ionic conductivity. For this purpose, composites containing up to 40 wt % of alumina, in a 9 mol % yttria-stabilized zirconia (9Y-CSZ) matrix were evaluated. In order to optimize the synthesis of the composites, a preliminary study of powder obtaining and processing were carried out, at compositions containing 20 wt % of alumina, in 9Y-CSZ. The ceramic powders were characterized by helium picnometry, X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, thermogravimetry, differential scanning calorimetry, granulometry by laser diffraction and gas adsorption (BET). The characterization of sinterized compacts were performed by X-ray diffraction, scanning electron microscopy, optical microscopy, density measurements, Vickers indentation and impedance spectroscopy. The obtained results show that the alumina addition, in the 9Y-CSZ matrix powders, raises the specific surface area, promotes deagglomeration of powders and elevates the oxides crystallization temperature, requiring higher

  15. Properties and clinical application of zirconia bioceramics in medicine

    Directory of Open Access Journals (Sweden)

    Čedomir Oblak

    2014-01-01

    Full Text Available Background: A group of inorganic non-metal biomaterials, that are commonly used in clinical medicine to replace or repair tissues, can be classified as a bioceramics. This group includes bioactive glasses, glass-ceramics, hydroxy-apatite and some other calcium phosphates. In addition, some bio-inert engineering ceramics materials have become increasingly utilised, aluminum oxide, zirconium oxide and their composites being the most popular. With the developement of yttria stabilized tetragonal zirconium oxide ceramics (Y-TZP medical community received a high strength biomaterial that is currently a material of choice for the manufacturing of medical devices. Y-TZP ceramics is becoming also increasingly used in dental medicine, where frameworks are manufactured by the use of computer-assisted technology.Conclusions: The article describes the basic properties of zirconia oxide ceramics important for the use in clinical medicine; high strength and fracture toughness, biocompatibility and negligible radiation. The ageing issue of this particular material, which is attributable to the thermo-dynamical instability of tetragonal zirconium oxide in hydrothermal conditions, is also discussed. When exposed to an aqueous environment over long periods of time, the surface of the Y-TZP ceramic will start transforming spontaneously into the monoclinic structure. The mechanism leading to the t-m transformation is temperature-dependent and is accompanied by extensive micro-cracking, which ultimately leads to strength degradation. The degradation might influence the clinical success rate of medical devices and therefore Y-TZP femoral heads are no longer made of pure zirconium oxide. Composites of zirconium and aluminium oxides are used instead, that are currently the strongest ceramic materials used in clinical medicine. In this work the clinical application of zirconia oxide ceramics in dental medicine is also presented. Conventional porcelain fused to metal

  16. Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning

    NARCIS (Netherlands)

    Cadafalch Gazquez, G.; Smulders, V.; Veldhuis, S.A.; Wieringa, P.; Moroni, L.; Boukamp, B.A.; Elshof, ten J.E.

    2017-01-01

    The fabrication process of ceramic yttria-stabilized zirconia (YSZ) and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the phys

  17. Study on nano-structured hydroxyapatite/zirconia stabilized yttria on healing of articular cartilage defect in rabbit

    Directory of Open Access Journals (Sweden)

    Amir Sotoudeh

    2013-05-01

    Full Text Available PURPOSE: Articular Cartilage has limited potential for self-repair and tissue engineering approaches attempt to repair articular cartilage by scaffolds. We hypothesized that the combined hydroxyapatite and zirconia stabilized yttria would enhance the quality of cartilage healing. METHODS: In ten New Zealand white rabbits bilateral full-thickness osteochondral defect, 4 mm in diameter and 3 mm depth, was created on the articular cartilage of the patellar groove of the distal femur. In group I the scaffold was implanted into the right stifle and the same defect was created in the left stifle without any transplant (group II. Specimens were harvested at 12 weeks after implantation, examined histologically for morphologic features, and stained immunohistochemically for type-II collagen. RESULTS: In group I the defect was filled with a white translucent cartilage tissue In contrast, the defects in the group II remained almost empty. In the group I, the defects were mostly filled with hyaline-like cartilage evidenced but defects in group II were filled with fibrous tissue with surface irregularities. Positive immunohistochemical staining of type-II collagen was observed in group I and it was absent in the control group. CONCLUSION: The hydroxyapatite/yttria stabilized zirconia scaffold would be an effective scaffold for cartilage tissue engineering.

  18. Low temperature environmental degradation of zirconia ceramics

    Science.gov (United States)

    Zhao, Zhenbo

    2005-11-01

    The low temperature environmental degradation (LTED) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has been prevented, or at least retarded, by using both bulk doping and surface doping methods with either cation, or anion, stabilizers. The introduction of both mullite and alumina into 3Y-TZP by a bulk-doping method was found to be effective in suppressing the tetragonal-->monoclinic transformation induced by water during hydrothermal treatment thus giving rise to better mechanical properties. The beneficial effects of alumina on the phase stability of the 3Y-TZP ceramic are considered to be due to the increase in the elastic modulus of the constraining matrix, as well as to the segregation of A12O3 at grain boundaries. The LTED transformation kinetics as determined by x-ray diffraction (XRD) and White Light Interferometer (WLI) analysis showed that the isothermal tetragonal-to-monoclinic transformation starts from the surface and has an incubation-nucleation-growth mechanism which can be described by the Johnson-Mehl-Avrami equation. The degradation of Y-TZP ceramic after hydrothermal treatment can be effectively overcome by surface doping by a solid diffusion method with tetravalent dopants: CeO2 and GeO2; with trivalent dopants: La2O 3 and Fe2O3; and with divalent dopants: CuO and MgO. For surface CeO2-, GeO2- and Fe2O 3-doping, this degradation inhibition behaviour is attributed to a localized increase in cation stabilizer content which satisfies the requirements for stabilization of the tetragonal phase. However, in each case, the stability mechanisms are different. For surface La2O3doping, surface doping overcomes the formation of La2O3 and La 2Zr2O7 since the extra La2O3 can further diffuse to the center of the 3Y-TZP ceramic. For CuO-doping, small amounts of CuO form a liquid that can act as a conduit for the re-distribution of yttria. In the case of surface MgO modification, the stabilization results from the isolated nature of the

  19. A review of C1 chemistry synthesis using yttrium-stabilized zirconia catalyst

    Institute of Scientific and Technical Information of China (English)

    Antonius Indarto; Jae-Wook Choi; Hwaung Lee; Hyung Keun Song

    2008-01-01

    C1 chemistry based on synthesis gas, methane, and carbon dioxide offers many routes to industrial chemicals. The reactions related to the synthesis of gas can be classified into direct and indirect approach for making such products, such as acetic acid, dimethyl ether, and alcohol. Catalytic syngas processing is currently done at high temperatures and pressures, conditions that could be unfavorable for the life of the catalyst. Another issue of C1 chemistry is related to the methane-initiated process. It has been known that direct methane conversions are still suffering from low yields and selectivity of products resulting in unprofitable ways to produce products, such as higher hydrocarbons, methanol, and so on. However, many experts and researchers are still trying to find the best method to overcome these barriers, for example, by finding the best catalyst to reduce the high-energy barrier of the reactions and conduct only selective catalyst-surface reactions. The application of Yttria-Stabilized Zirconia (YSZ) and its combination with other metals for catalyzing purposes are increasing. The existence of an interesting site that acts as oxygen store could be the main reason for it. Moreover, formation of intermediate species on the surface of YSZ also contributes significantly in increasing the production of some specific products. Understanding the phenomena happening inside could be necessary. In this article, the use of YSZ for some C1 chemistry reactions was discussed and reviewed.

  20. Mechanical properties of dental zirconia ceramics changed with sandblasting and heat treatment.

    Science.gov (United States)

    Sato, Hideo; Yamada, Kiyotaka; Pezzotti, Giuseppe; Nawa, Masahiro; Ban, Seiji

    2008-05-01

    Two types of tetragonal zirconia polycrystals (TZP), a ceria-stabilized TZP/Al2O3 nanocomposite (CZA) and a conventional yttria-stabilized TZP (Y-TZP), were sandblasted with 70-microm alumina and 125-microm SiC powders, then partially annealed at 500-1200 degrees C for five minutes. Monoclinic ZrO2 content was determined by X-ray diffractometry and Raman spectroscopy. Biaxial flexure test was conducted on the specimens before and after the treatments. Monoclinic ZrO2 content and biaxial flexure strength increased after sandblasting, but decreased after heat treatment. However, in both cases, the strength of CZA was higher than that of Y-TZP. Raman spectroscopy showed that a compressive stress field was introduced on the sample surface after sandblasting. It was concluded that sandblasting induced tetragonal-to-monoclinic phase transformation and that the volume expansion associated with such a phase transformation gave rise to an increase in compressive stress on the surface of CZA. With the occurrence of such a strengthening mechanism in the microstructure, it was concluded that CZA was more susceptible to stress-induced transformation than Y-TZP.

  1. Preparation of hydroxyapatite/zirconia bioceramic nanocomposites for orthopaedic and dental prosthesis applications

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Yun-Mo [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Shin, Young-Keun [Technical Support Division, Korloy Incorporated, Cheongjoo-si, Choongbook 361-290 (Korea, Republic of); Ryu, Jae-Jun [Department of Prosthodontics, Medical School, Korea University, Seoul 136-701 (Korea, Republic of)

    2007-02-14

    Homogeneous mixtures of hydroxyapatite (HAp) and yttria-stabilized zirconia (YSZ) nanoparticles were successfully synthesized using chemical co-precipitation and subsequent calcination. For the synthesis of HAp/YSZ nanopowder, the Ca/P atomic ratio was 1.73 to obtain high-content stoichiometric hydroxyapatite phase and to suppress {beta}-tricalcium phosphate ({beta}-TCP) formation. The agglomerated crystalline powders were milled using YSZ ball media to obtain well-separated nanoparticles. The final particle size of the HAp and YSZ was {approx}50-70 and {approx}15-30 nm, respectively. The crystallinity and morphological feature of the nanopowder was analysed using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses. The ball-milled nanopowder mixture was hot pressed at 1100 deg. C for 1 h under 20 MPa in vacuum atmosphere. The sintered HAp/YSZ nanocomposites exhibited approximately 99% of the theoretical density, due not only to the fine nanoscale of the particles, but also to the homogeneous distribution of the nanoparticle mixture. They also showed fine grain structures of the HAp phase due to the suppressed grain growth by YSZ particles. The nanocomposites showed improved mechanical properties, flexural strength of {approx}155 MPa and fracture toughness of {approx}2.1 MP m{sup 1/2}, due to the YSZ contribution to the HAp matrix.

  2. Preparation of hydroxyapatite/zirconia bioceramic nanocomposites for orthopaedic and dental prosthesis applications

    Science.gov (United States)

    Sung, Yun-Mo; Shin, Young-Keun; Ryu, Jae-Jun

    2007-02-01

    Homogeneous mixtures of hydroxyapatite (HAp) and yttria-stabilized zirconia (YSZ) nanoparticles were successfully synthesized using chemical co-precipitation and subsequent calcination. For the synthesis of HAp/YSZ nanopowder, the Ca/P atomic ratio was 1.73 to obtain high-content stoichiometric hydroxyapatite phase and to suppress β-tricalcium phosphate (β-TCP) formation. The agglomerated crystalline powders were milled using YSZ ball media to obtain well-separated nanoparticles. The final particle size of the HAp and YSZ was ~50-70 and ~15-30 nm, respectively. The crystallinity and morphological feature of the nanopowder was analysed using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analyses. The ball-milled nanopowder mixture was hot pressed at 1100 °C for 1 h under 20 MPa in vacuum atmosphere. The sintered HAp/YSZ nanocomposites exhibited approximately 99% of the theoretical density, due not only to the fine nanoscale of the particles, but also to the homogeneous distribution of the nanoparticle mixture. They also showed fine grain structures of the HAp phase due to the suppressed grain growth by YSZ particles. The nanocomposites showed improved mechanical properties, flexural strength of ~155 MPa and fracture toughness of ~2.1 MP m1/2, due to the YSZ contribution to the HAp matrix.

  3. A high-temperature calorimetric flow sensor employing ion conduction in zirconia

    Science.gov (United States)

    Persson, A.; Lekholm, V.; Thornell, G.; Klintberg, L.

    2015-05-01

    This paper presents the use of the temperature-dependent ion conductivity of 8 mol % yttria-stabilized zirconia (YSZ8) in a miniature high-temperature calorimetric flow sensor. The sensor consists of 4 layers of high-temperature co-fired ceramic (HTCC) YSZ8 tape with a 400 μm wide, 100 μm deep, and 12 500 μm long internal flow channel. Across the center of the channel, four platinum conductors, each 80 μm wide with a spacing of 160 μm, were printed. The two center conductors were used as heaters, and the outer, up- and downstream conductors were used to probe the resistance through the zirconia substrate around the heaters. The thermal profile surrounding the two heaters could be made symmetrical by powering them independently, and hence, the temperature sensing elements could be balanced at zero flow. With nitrogen flowing through the channel, forced convection shifted the thermal profile downstream, and the resistance of the temperature sensing elements diverged. The sensor was characterized at nitrogen flows from 0 to 40 sccm, and resistances at zero-flow from 10 to 50 MΩ. A peak sensitivity of 3.1 MΩ/sccm was obtained. Moreover, the sensor response was found to be linear over the whole flow range, with R2 of around 0.999, and easy to tune with the individual temperature control of the heaters. The ability of the sensor to operate in high temperatures makes it promising for use in different harsh environments, e.g., for close integration with microthrusters.

  4. Effects of Acid Treatment on Dental Zirconia: An In Vitro Study.

    Directory of Open Access Journals (Sweden)

    Haifeng Xie

    Full Text Available The aim of this study was to evaluate the effects of hydrofluoric (HF acid, acetic acid, and citric acid treatments on the physical properties and structure of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP at ambient temperature. In total, 110 bar-shaped zirconia specimens were randomly assigned to 11 groups. The specimens in the control group (C received no surface treatment, while those in the Cage group were hydrothermally aged at 134°C and 0.2 MPa for 20 h. Ten specimens each were immersed at ambient temperature in 5% and 40% HF acid for 2 h (40HF0, 1 day (5HF1, 40HF1, and 5 days (5HF5, 40HF5, while 10 each were immersed at ambient temperature in 10% acetic acid and 20% citric acid for 7 (AC7, CI7 and 14 days (AC14, CI14. X-ray diffraction (XRD was used to quantitatively estimate the monoclinic phase. Furthermore, flexural strength, surface roughness, and surface Vickers hardness were measured after treatment. Scanning electron microscopy (SEM was used to characterize the surface morphology. The Cage group specimens exhibited an increased monoclinic phase and flexural strength. Furthermore, 40% HF acid immersion decreased the flexural strength and surface hardness and deteriorated the surface finish, while 5% HF acid immersion only decreased the surface hardness. All the HF acid-immersed specimens showed an etched surface texture on SEM observations, while the other groups did not. These findings suggest that the treatment of Y-TZP with 40% HF acid at ambient temperature causes potential damage, while treatment with 5% HF acid, acetic acid, and citric acid is safe.

  5. Effect of liner and porcelain application on zirconia surface structure and composition

    Institute of Scientific and Technical Information of China (English)

    Tariq F Alghazzawi; Gregg M Janowski

    2016-01-01

    The purpose of this study was to determine if there is an effect of liner and porcelain application (layering and pressing techniques) on the surface of yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), which were exposed to permutations of liner, layered porcelain, and pressed porcelain. Scanning electron microscope (SEM)/energy dispersive spectroscope (EDS) was used to identify changes in composition and microstructure after removing liner and porcelain with hydrofluoric acid. Simulated aging was also conducted to determine the effect of liner and porcelain on low-temperature degradation. The control group had a typical equiaxed grain structure, referred to as unaffected. When covered with liner or porcelain, some areas changed in structure and composition and were termed affected. The frequency of affected structure decreased when liner was covered with either layered porcelain or pressed porcelain. There were statistical differences (Po0.05) in the composition between affected and unaffected for zirconium (layered porcelain with liner:affected=60%(0.8%) (m/m), unaffected=69%(4%), layered porcelain without liner:affected=59%(3%), unaffected=65%(3%)) and oxygen (layered porcelain with liner:affected=35%(2%), unaffected=26%(4%), layered porcelain without liner:affected=35%(3%), unaffected=30%(2%)). However, there were statistical differences (Po0.05) in the composition for zirconium and oxygen of the aged layered porcelain without liner only. The liner should not be used before porcelain application, especially when using the layering technique for zirconia restorations. Furthermore, pressing should be considered the technique of choice over layering.

  6. Synthesis of Zirconia Powder in Zirconia Aqueous Sol

    Institute of Scientific and Technical Information of China (English)

    LIMao-qiang

    1994-01-01

    Spherical zirconia particles formed by coagulation of colloidal particles in zirconia aqueous sol followed by calcination.The zirconia sol was prepared from zirconium oxychloride aqueous solution by adjusting its pH value.The coag-ulation resulted from addition of preopanol in the sol the coagulation mechanism was discussed based on collicd theory.

  7. Veneered zirconia inlay-retained fixed dental prostheses: 10-Year results from a prospective clinical study.

    Science.gov (United States)

    Rathmann, Friederike; Bömicke, Wolfgang; Rammelsberg, Peter; Ohlmann, Brigitte

    2017-09-01

    The purpose of this study was to evaluate the 10-year clinical performance of zirconia-based inlay-retained fixed dental prostheses (IRFDP). For replacement of a molar in 27 patients, 30 IRFDP were luted by use of different cements, Panavia F (Kuraray Europe GmbH) or Multilink Automix (Ivoclar Vivadent GmbH), with use of inlay/inlay, inlay/full-crown, or inlay/partial-crown retainers for anchorage. Frameworks were milled from yttria-stabilized zirconia (IPS e.maxZirCAD; Ivoclar Vivadent GmbH) and fully veneered with pressable ceramic (IPS e.max ZirPress; Ivoclar Vivadent GmbH). Before luting, the IRFDP were silica-coated (Rocatec; 3M Espe) and silanized (Monobond S; Ivoclar Vivadent GmbH). Complications (for example, chipping or delamination of the veneering ceramic, debonding, secondary caries, endodontic treatment, and abutment tooth fracture) and failure were reported, by use of standardized report forms, 2 weeks, 6 months, and 1, 2, and 10 years after cementation. Statistical analysis included Kaplan-Meier survival and success (complication-free survival) and Cox regression analysis (α=0.05 for all). During the 10-year observation period, the complications most often observed were chipping of the veneer and debonding. Twenty-five restorations failed and one participant dropped out. Cumulative 10-year survival and success were 12.1% and 0%, respectively. The design of the retainer, use of a dental dam, choice of cement, and location in the dental arch had no statistically significant effect on the occurrence of complications. Use of fully veneered zirconia-based IRFDP with this technique cannot be recommended. A large incidence of complications and poor survival were observed for fully veneered zirconia-based IRFDP, revealing an urgent need for further design improvements for this type of restoration. This, again, emphasizes the need for testing of new restoration designs in clinical trials before implementation in general dental practice. Copyright © 2017

  8. Zirconia-reinforced dental restorations

    NARCIS (Netherlands)

    C. Chen

    2013-01-01

    The series of studies conducted in this thesis showed that there are several ways to enhance the performance of fixed restorations regarding the application of zirconia. One possible way is to change the sintering procedure of zirconia, so that the physical properties of zirconia such BFS, density o

  9. Four-year clinical results of fixed dental prostheses with zirconia substructures (Cercon): end abutments vs. cantilever design.

    Science.gov (United States)

    Wolfart, Stefan; Harder, Sönke; Eschbach, Stefanie; Lehmann, Frank; Kern, Matthias

    2009-12-01

    The purpose of this prospective study was to evaluate the clinical outcome of three- to four-unit posterior all-ceramic fixed dental prostheses (FDPs) made of yttria-stabilized tetragonal zirconia-polycrystal ceramic frameworks (CerconBase; Degudent). Fifty-eight restorations were placed in 48 patients. Twenty-four FDPs had an end abutment design (EAD) replacing 3 premolars and 21 molars. Thirty-four FDPs had a cantilever design (CD) replacing 11 premolars and 23 molars. The frameworks had a minimum proximal connector dimension of 3 x 3 mm. The fixed dental prostheses were cemented with glass-ionomer cement after air-abrading the inner crown surfaces. Three FDPs were defined as drop-outs. The mean observation period was 48 +/- 7 months for the EAD (21 patients/24 FDPs) and 50 +/- 14 months for the CD (25 patients/31 FDPs). The 4-yr survival rate, according to the Kaplan-Meier analyses, was 96% for the EAD and 92% for the CD. The technical complication rate was 13% for the EAD and 12% for the CD, and the biological complication rate was 21% for the EAD and 15% for the CD. For none of the analyses were significant differences found between both groups. After 4 yr the clinical outcome of three- to four-unit posterior FDPs with EAD and CD was promising.

  10. Zirconia-based mixed potential sensor with Pt electrode prepared by spin-coating of polymeric precursor

    Science.gov (United States)

    Chrzan, A.; Woźniak, Ł.; Szymczewska, D.; Jasiński, P.

    2016-11-01

    Many types of yttria-stabilized zirconia (YSZ) based gas sensors have been explored extensively in recent years. Great attention have been directed to mixed-potential-type gas sensors. It is due to growing concerns with environmental issues. Not without a significance is the fact of very attractive performance of this type of sensor allowing to detect low concentration of pollutant gases. In this paper two types of YSZ based mixed-potential planar sensors were investigated, with platinum electrode painted using commercial paste and with spin coated platinum layer. Both types had second electrode in the form of porous gold. Measurements were performed at 400 °C in synthetic air and different concentrations of SO2. Gas flow was set to 100 cm3min-1 and the concentration of 50 ppm SO2 was tested. During this measurements the sensor was sintered in-situ at increasing temperatures. Sensor with 100 nm spin-coated platinum layer sintered at 700 °C was shown to exhibit two times smaller response than sensor with 5 μm porous electrode, while consisting of over 20 times smaller amount of Pt. The influence of sintering temperature on electrical conductivity of platinum films was also examined. Moreover, the platinum microstructure was investigated using SEM microscopy.

  11. Growth and characterization of highly oriented gadolinia-doped ceria (111) thin films on zirconia (111)/sapphire (0001) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bera, Debasis; Kuchibhatla, Satyanarayana V N T; Azad, Samina; Saraf, Laxmikant V.; Wang, Chong M.; Shutthanandan, V.; Nachimuthu, Ponnusamy; Mccready, David E.; Engelhard, Mark H.; Marina, Olga A.; Baer, Donald R.; Seal, Sudipta; Thevuthasan, Suntharampillai

    2008-07-31

    Highly-oriented pure and gadolinia-doped ceria thin films have been grown on pure and ZrO2 (111)-buffered Al2O3 (0001) substrates using oxygen plasma-assisted molecular beam epitaxy (OPA-MBE) to understand the oxygen ionic transport processes in ceria based oxide thin films. Gadolinia-doped ceria films grown on pure Al2O3(0001) substrate show polycrystalline features due to structural deformations resulting from the large lattice mismatch between the Al2O3(0001) substrate and the films. However, the films, grown on a thin layer of ZrO2(111) buffered Al2O3 (0001) substrate, appears to be highly oriented. These films were characterized using high resolution transmission electron microscopy (HRTEM) and x-ray photoelectron spectroscopy (XPS) depth profiling. Oxygen ionic conductivity in gadolinia-doped ceria films was measured as a function of Gd concentration and these results were compared with the ion conductance data of the polycrystalline and single crystalline yttria-stabilized zirconia (YSZ).

  12. Production and characterization of miro- and nano-features in biomedical alumina and zirconia ceramics using a tape casting route.

    Science.gov (United States)

    Domanski, Maciej; Winnubst, Louis; Luttge, Regina; Lamers, Edwin; Walboomers, X Frank; Jansen, John; Gardeniers, Han

    2012-07-01

    A process of micromolding, delivering micro- and nanopatterned ceramic surfaces for biomaterial applications is described in this work. To create the desired structures, tape casting of ceramic slurries on microfabricated silicon mold was used. Several tape casting slurry compositions were tested to evaluate the feasibility of transferring micro- and nano-features from silicon molds. Used ceramics were alumina (α-Al(2)O(3)) and yttria stabilized zirconia. Three types of polymeric binders for the green tape (PVB, PES, and PVP) were investigated using three different solvents (ethanol, n-methyl-pyrrolidone, water). Well-defined features in shapes of wells with diameters down to 2.4 μm and a depth of 10 μm and pillars with diameters down to 1.7 μm and a height of 3 μm were obtained. Morphology, grain size and porosity of the sintered bodies were characterized. Finally fibroblast cells were cultured on the surfaces in order to observe their morphology under influence of the microstructured surfaces.

  13. Examination of bond strength and mechanical properties of Y-TZP zirconia ceramics with different surface modifications.

    Science.gov (United States)

    Yamaguchi, Hiroaki; Ino, Satoshi; Hamano, Naho; Okada, Shusaku; Teranaka, Toshio

    2012-01-01

    The purpose of our study was to evaluate the effects of surface modifications on the bond strength between veneering porcelains and Yttria-stabilized tetragonal zirconia (Y-TZP). In a bond strength tests, the effect of control, 70 µm alumina-sandblasting, 30 µm and 110 µm silica-coating of the Y-TZP surface on bonding were evaluated with veneering porcelains. In addition, the effect of surface modification on the flexural strength of Y-TZP was also evaluated. The data was analyzed using one-way ANOVA and Tukey test. All specimens showed bond strength values in excess of 25 MPa, the minimum allowed by ISO9693. In addition, significantly differences were found between the control and the 30 µm silica-coated. On the other hand the flexural strength of Y-TZP does not significantly difference for any surface modification. These results indicate that silica-coating may provide an effective pre-treatment for this enhancement of the bond strength while maintaining the strength of Y-TZP.

  14. Zirconia in fixed implant prosthodontics.

    Science.gov (United States)

    Guess, Petra Christine; Att, Wael; Strub, Joerg Rudolf

    2012-10-01

    CAD/CAM technology in combination with zirconia ceramic has increasingly gained popularity in implant dentistry. This narrative review presents the current knowledge on zirconia utilized as framework material for implant-borne restorations and implant abutments, laboratory tests and developments, clinical performance, and possible future trends for implant dentistry are addressed. A review of available literature from 1990 through 2010 was conducted with search terms zirconia,"implants,"abutment,"crown," and "fixed dental prosthesis" using electronic databases (PubMed) and manual searching. Latest applications of zirconia in implant dentistry include implant abutments, multiple unit and full-arch frameworks as well as custom-made bars to support fixed and removable prostheses. High biocompatibility, low bacterial surface adhesion as well as favorable chemical properties of zirconia ceramics are reported. Zirconia stabilized with yttrium oxide exhibits high flexural strength and fracture toughness due to a transformation toughening mechanism. Preliminary clinical data confirmed the high stability of zirconia for abutments and as a framework material for implant borne crowns and fixed dental prostheses. Zirconia abutment or framework damage has rarely been encountered. However, veneering porcelain fractures are the most common technical complication in implant-supported zirconia restorations. These porcelain veneer failures have led to concerns regarding differences in coefficient of thermal expansions between core and veneering porcelain and their respective processing techniques. As presently evidence of clinical long-term data is missing, caution with regard to especially extensive implant-borne zirconia frameworks is recommended. © 2010 Wiley Periodicals, Inc.

  15. Biomechanical and histological evaluation of the osseointegration capacity of two types of zirconia implant

    Science.gov (United States)

    Han, Jian-min; Hong, Guang; Lin, Hong; Shimizu, Yoshinaka; Wu, Yuhan; Zheng, Gang; Zhang, Hongyu; Sasaki, Keiichi

    2016-01-01

    The purpose of this study was to evaluate the biomechanical and histological behavior of a ceria-stabilized zirconia–alumina nanocomposite (NanoZr) in comparison with that of 3 mol% yttria-stabilized tetragonal zirconia polycrystalline (3Y-TZP) in Sprague Dawley rats. Cylindrical NanoZr and 3Y-TZP implants (diameter 1 mm, length 2 mm) were used. Implant-surface morphology and surface roughness were determined by scanning white-light interferometry and scanning electron microscopy, respectively. The cylindrical zirconia implants were placed at the distal edge of the femur of Sprague Dawley rats. At weeks 2, 4, and 8, the interfacial shear strength between implant and bone was measured by push-in test. Histological analysis was performed using hard-tissue sections. Bone–implant contact (BIC), the thickness of new bone around the implant within the bone marrow area, and osteoclast numbers were evaluated. The average surface roughness of 3Y-TZP (Sa 0.788 μm) was significantly higher than that of NanoZr (Sa 0.559 μm). The shear strengths of 3Y-TZP and NanoZr were similar at 2 weeks, but at 4 and 8 weeks the shear strength of NanoZr was higher than that of 3Y-TZP. The average BIC values within the bone marrow area for 3Y-TZP and NanoZr were 25.26% and 31.51% at 2 weeks, 46.78% and 38% at 4 weeks, and 47.88% and 56.81% at 8 weeks, respectively. The average BIC values within the cortical area were 38.86% and 58.42% at 2 weeks, 66.82% and 57.74% at 4 weeks, and 79.91% and 78.97% at 8 weeks, respectively. The mean BIC value did not differ significantly between the two zirconia materials at any time point. The NanoZr implants were biocompatible, capable of establishing close BIC, and may be preferred for metal-free dental implants. PMID:27994456

  16. Irradiation effects and behaviour of fission products in zirconia and spinel; Effets d'irradiation et comportement des produits de fission dans la zircone et le spinelle

    Energy Technology Data Exchange (ETDEWEB)

    Gentils, A

    2003-10-01

    Crystalline oxides, such as zirconia (ZrO{sub 2}) and spinel (MgAl{sub 2}O{sub 4}), are promising inert matrices for the transmutation of plutonium and minor actinides. This work deals with the study of the physico-chemical properties of these matrices, more specifically their behaviour under irradiation and their capacity to retain fission products. Irradiations at low energy and incorporation of stable analogs of fission products (Cs, I, Xe) into yttria-stabilized zirconia and magnesium-aluminate spinel single crystals were performed by using the ion implanter IRMA (CSNSM-Orsay). Irradiations at high energy were made on several heavy ion accelerators (GANIL-Caen, ISL-Berlin, HIL-Warsaw). The damage induced by irradiation and the release of fission products were monitored by in situ Rutherford Backscattering Spectrometry experiments. Transmission electron microscopy was also used in order to determine the nature of the damage induced by irradiation. The results show that irradiation of ZrO{sub 2} and MgAl{sub 2}O{sub 4} with heavy ions (about hundred keV and about hundred MeV) induces a huge structural damage in crystalline matrices. Total disorder (amorphization) is however never reached in zirconia, contrary to what is observed in the case of spinel. The results also emphasize the essential role played by the concentration of implanted species on their retention capacity. A dramatic release of fission products was observed when the concentration exceeds a threshold of a few atomic percent. Irradiation of implanted samples with medium-energy noble-gas ions leads to an enhancement of the fission product release. The exfoliation of spinel crystals implanted at high concentration of Cs ions is observed after a thermal treatment at high temperature. (author)

  17. Zirconia as a Dental Biomaterial

    Directory of Open Access Journals (Sweden)

    Alvaro Della Bona

    2015-08-01

    Full Text Available Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different substrates, which has offered a great challenge to dental zirconia research and development. This study characterizes zirconia as a dental biomaterial, presenting the current consensus and challenges to its dental applications.

  18. Phase Transformation of Nanosized Zirconia

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The nanosized zirconia was synthesized via solid state reaction in the presence of surfactant. The results indicate that crystal phase of zirconia can be controlled by tuning the syn- thesis parameters such as OH-/Zr molar ratio, crystallizing temperature and time. It can be trans- formed among amorphous, tetragonal and monoclinic phases. The transformation is driven by particle size. The research shows the nanocrystalline zirconia possesses the higher thermal stability compared with amorphous framework. The "glow exotherm" can be observed for the amorphous samples. Otherwise, it is in the absence for nanocrystalline samples. Herein, the reason for retention of tetragonal zirconia is demonstrated.

  19. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications; Sintese e processamento de compositos a base de alumina e zirconia com infiltracao de fase vitrea para aplicacoes odontologicas

    Energy Technology Data Exchange (ETDEWEB)

    Duarte, Daniel Gomes

    2009-07-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning

  20. Influence of Grain Refinement on Microstructure and Mechanical Properties of Tungsten Carbide/Zirconia Nanocomposites

    Science.gov (United States)

    Nasser, Ali; Kassem, Mohamed A.; Elsayed, Ayman; Gepreel, Mohamed A.; Moniem, Ahmed A.

    2016-11-01

    WC-W2C/ZrO2 nanocomposites were synthesized by pressure-less sintering (PS) and spark plasma sintering (SPS) of tungsten carbide/yttria-stabilized tetragonal zirconia, WC/TZ-3Y. Prior to sintering, WC/TZ-3Y powders were totally ball-milled for 20 and 120 h to obtain targeted nano (N) and nano-nano (N-N) structures, indicated by transmission electron microscopy and powder x-ray diffraction (PXRD). The milled powders were processed via PS at temperatures of 1773 and 1973 K for 70 min and SPS at 1773 K for 10 min. PXRD as well as SEM-EDS indicated the formation of WC-W2C/ZrO2 composites after sintering. The mechanical properties were characterized via Vicker microhardness and nanoindentation techniques indicating enhancements for sufficiently consolidated composites with high W2C content. The effects of reducing particle sizes on phase transformation, microstructure and mechanical properties are reported. In general, the composites based on the N structure showed higher microhardness than those for N-N structure, except for the samples PS-sintered at 1773 K. For instance, after SPS at 1773 K, the N structure showed a microhardness of 18.24 GPa. Nanoindentation measurements revealed that nanoscale hardness up to 22.33 and 25.34 GPa and modulus of elasticity up to 340 and 560 GPa can be obtained for WC-W2C/ZrO2 nanocomposites synthesized by the low-cost PS at 1973 K and by SPS at 1773 K, respectively.

  1. Influence of Grain Refinement on Microstructure and Mechanical Properties of Tungsten Carbide/Zirconia Nanocomposites

    Science.gov (United States)

    Nasser, Ali; Kassem, Mohamed A.; Elsayed, Ayman; Gepreel, Mohamed A.; Moniem, Ahmed A.

    2016-09-01

    WC-W2C/ZrO2 nanocomposites were synthesized by pressure-less sintering (PS) and spark plasma sintering (SPS) of tungsten carbide/yttria-stabilized tetragonal zirconia, WC/TZ-3Y. Prior to sintering, WC/TZ-3Y powders were totally ball-milled for 20 and 120 h to obtain targeted nano (N) and nano-nano (N-N) structures, indicated by transmission electron microscopy and powder x-ray diffraction (PXRD). The milled powders were processed via PS at temperatures of 1773 and 1973 K for 70 min and SPS at 1773 K for 10 min. PXRD as well as SEM-EDS indicated the formation of WC-W2C/ZrO2 composites after sintering. The mechanical properties were characterized via Vicker microhardness and nanoindentation techniques indicating enhancements for sufficiently consolidated composites with high W2C content. The effects of reducing particle sizes on phase transformation, microstructure and mechanical properties are reported. In general, the composites based on the N structure showed higher microhardness than those for N-N structure, except for the samples PS-sintered at 1773 K. For instance, after SPS at 1773 K, the N structure showed a microhardness of 18.24 GPa. Nanoindentation measurements revealed that nanoscale hardness up to 22.33 and 25.34 GPa and modulus of elasticity up to 340 and 560 GPa can be obtained for WC-W2C/ZrO2 nanocomposites synthesized by the low-cost PS at 1973 K and by SPS at 1773 K, respectively.

  2. Response of cubic zirconia irradiated with 4-MeV Au ions at high temperature: An X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Debelle, A., E-mail: aurelien.debelle@u-psud.fr [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse (CSNSM), Univ. Paris-Sud, CNRS-IN2P3, 91405 Orsay Cedex (France); Thome, L. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse (CSNSM), Univ. Paris-Sud, CNRS-IN2P3, 91405 Orsay Cedex (France); Boulle, A. [Science des Procedes Ceramiques et de Traitements de Surface (SPCTS), CNRS UMR 6638, Centre Europeen de la Ceramique, 12 rue Atlantis, 87068 Limoges (France); Moll, S.; Garrido, F.; Qasim, L.; Rosza, P. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse (CSNSM), Univ. Paris-Sud, CNRS-IN2P3, 91405 Orsay Cedex (France)

    2012-04-15

    Yttria-stabilized cubic zirconia single-crystals have been irradiated with 4-MeV Au{sup 2+} ions at fluences ranging from 10{sup 12} cm{sup -2} to 5 Multiplication-Sign 10{sup 15} cm{sup -2} and at three temperatures (room temperature, 500 Degree-Sign C and 800 Degree-Sign C). Evaluation of the irradiation-induced strain has been performed by the X-ray diffraction technique. It is found that, whatever the irradiation temperature, the elastic-strain build-up exhibits two steps. An increase of the (tensile) strain-level is observed in the first step. A drastic strain relaxation occurs at a transition fluence, which defines the beginning of the second step. Increasing the irradiation temperature induces a decrease of the strain level and a shift of the transition fluence towards low fluence. Both effects may be explained by an enhanced defect-clustering rate which occurs already at 500 Degree-Sign C.

  3. Gibbs-Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth

    OpenAIRE

    Shen, Y; Chen, R.; Yu, X.; Wang, Q.; Jungjohann, KL; Dayeh, SA; Wu, T.

    2016-01-01

    Epitaxy-enabled bottom-up synthesis of self-assembled planar nanowires via the vapor-liquid-solid mechanism is an emerging and promising approach toward large-scale direct integration of nanowire-based devices without postgrowth alignment. Here, by examining large assemblies of indium tin oxide nanowires on yttria-stabilized zirconia substrate, we demonstrate for the first time that the growth dynamics of planar nanowires follows a modified version of the Gibbs-Thomson mechanism, which has be...

  4. Zirconia as a Dental Biomaterial

    OpenAIRE

    Alvaro Della Bona; Oscar E. Pecho; Rodrigo Alessandretti

    2015-01-01

    Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different subs...

  5. Zirconia as a Dental Biomaterial

    OpenAIRE

    Alvaro Della Bona; Pecho, Oscar E.; Rodrigo Alessandretti

    2015-01-01

    Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different subs...

  6. Effect of adhesive luting on the fracture resistance of zirconia compared to that of composite resin and lithium disilicate glass ceramic

    Science.gov (United States)

    Lim, Myung-Jin

    2017-01-01

    Objectives The purpose of this study was to evaluate the effect of adhesive luting on the fracture resistance of zirconia compared to that of a composite resin and a lithium disilicate glass ceramic. Materials and Methods The specimens (dimension: 2 mm × 2 mm × 25 mm) of the composite resin, lithium disilicate glass ceramic, and yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) were prepared. These were then divided into nine groups: three non-luting groups, three non-adhesive luting groups, and three adhesive luting groups, for each restorative material. In the non-luting groups, specimens were placed on the bovine tooth without any luting agents. In the non-adhesive luting groups, only zinc phosphate cement was used for luting the specimen to the bovine tooth. In the adhesive luting groups, specimens were pretreated, and the adhesive luting procedure was performed using a self-adhesive resin cement. For all the groups, a flexural test was performed using universal testing machine, in which the fracture resistance was measured by recording the force at which the specimen was fractured. Results The fracture resistance after adhesive luting increased by approximately 29% in the case of the composite resin, 26% in the case of the lithium disilicate glass ceramic, and only 2% in the case of Y-TZP as compared to non-adhesive luting. Conclusions The fracture resistance of Y-TZP did not increased significantly after adhesive luting as compared to that of the composite resin and the lithium disilicate glass ceramic.

  7. Shear bond strength of veneering porcelain to porous zirconia.

    Science.gov (United States)

    Nakamura, Takashi; Sugano, Tsuyoshi; Usami, Hirofumi; Wakabayashi, Kazumichi; Ohnishi, Hiroshi; Sekino, Tohru; Yatani, Hirofumi

    2014-01-01

    In this study, two types of porous zirconia and dense zirconia were used. The flexural strength of non-layered zirconia specimens and those of the layered zirconia specimens with veneering porcelain were examined. Furthermore, the shear bond strength of veneering porcelain to zirconia was examined. The flexural strength of the non-layered specimens was 1,220 MPa for dense zirconia and 220 to 306 MPa for porous zirconia. The flexural strength of the layered specimens was 360 MPa for dense zirconia and 132 to 156 MPa for porous zirconia, when a load was applied to the porcelain side. The shear bond strength of porcelain veneered to dense zirconia was 27.4 MPa and that of porcelain veneered to porous zirconia was 33.6 to 35.1 MPa. This suggests that the veneering porcelain bonded strongly to porous zirconia although porous zirconia has a lower flexural strength than dense zirconia.

  8. Thermal properties of plasma-sprayed yttria-stabilized zirconia thermal barrier coating on Ti-6Al-4V alloy analyzed by scanning thermal microscopy%钛合金表面等离子喷涂Y2O3稳定的ZrO2涂层的 扫描热显微镜分析

    Institute of Scientific and Technical Information of China (English)

    郭富安; 纪艳丽; N.Trannoy

    2007-01-01

    以纳米结构Y2O3稳定的ZrO2热喷涂粉末为原料,采用等离子喷涂法在Ti-6Al-4V合金上制备了纳米结构的热障涂层.利用扫描电镜(SEM)及扫描热显微镜(SThM)对涂层的微观组织及热性能进行了分析.在实验基础上建立了理论模型,并对涂层及基体的热导率进行了估算.结果表明:采用SThM分析方法估算的涂层厚度及涂层上的缺陷尺寸与采用其它分析方法测得的结果一致;虽然热导率的估算结果与采用其它方法得出的结果差异较大,但显示出扫描热显微镜分析是估算材料热导率潜在的方法.

  9. Facile one-step forming of NiO and yttrium-stabilized zirconia composite anodes with straight open pores for planar solid oxide fuel cell using phase-inversion tape casting method

    Science.gov (United States)

    Huang, Hua; Lin, Jie; Wang, Yunlong; Wang, Shaorong; Xia, Changrong; Chen, Chusheng

    2015-01-01

    The anode of NiO and yttria-stabilized zirconia (YSZ) with straight open pores is prepared by phase-inversion tape casting method. In the as-prepared green tape, its top and middle layers are derived from a slurry of NiO and YSZ, while the bottom layer from a slurry of graphite. The graphite layer is eliminated by calcination at elevated temperatures, leaving the finger-like porous layer exposed to the gas phase. A cell supported on the as-prepared anode substrate exhibits satisfactory electrochemical performances with a maximum power density of 780 mW cm-2 at 800 °C. The cell dose not show a convex-up curvature in I-V plots at high current density as often observed for most anode-supported cells, indicating the absence of concentration polarization which is in turn attributed to the open pore structure of the phase-inversion derived anode. The phase inversion tape casting technique explored in the present study involves almost the same equipments as and similar procedures to the conventional tape casting, and after further optimization it may become a simple and effective technique for mass production of anodes for SOFCs.

  10. Theoretical evaluation of zirconia and hafnia as gate oxides for si microelectronics.

    Science.gov (United States)

    Fiorentini, Vincenzo; Gulleri, Gianluca

    2002-12-23

    Parameters determining the performance of the crystalline oxides zirconia (ZrO2) and hafnia (HfO2) as gate insulators in nanometric Si electronics are estimated via ab initio calculations of the energetics, dielectric properties, and band alignment of bulk and thin-film oxides on Si (001). With their large dielectric constants, stable and low-formation-energy interfaces, large valence offsets, and reasonable (though not optimal) conduction offsets (electron injection barriers), zirconia and hafnia appear to have considerable potential as gate oxides for Si electronics.

  11. Investigation of a zirconia co-fired ceramic calorimetric microsensor for high-temperature flow measurements

    Science.gov (United States)

    Lekholm, Ville; Persson, Anders; Klintberg, Lena; Thornell, Greger

    2015-06-01

    This paper describes the design, fabrication and characterization of a flow sensor for high-temperature, or otherwise aggressive, environments, like, e.g. the propulsion system of a small spacecraft. The sensor was fabricated using 8 mol% yttria stabilized zirconia (YSZ8) high-temperature co-fired ceramic (HTCC) tape and screen printed platinum paste. A calorimetric flow sensor design was used, with five 80 µm wide conductors, separated by 160 µm, in a 0.4 mm wide, 0.1 mm deep and 12.5 mm long flow channel. The central conductor was used as a heater for the sensor, and the two adjacent conductors were used to resistively measure the heat transferred from the heater by forced convection. The two outermost conductors were used to study the influence of an auxiliary heat source on the sensor. The resistances of the sensor conductors were measured using four-point connections, as the gas flow rate was slowly increased from 0 to 40 sccm, with different power supplied through the central heater, as well as with an upstream or downstream heater powered. In this study, the thermal and electrical integrability of microcomponents on the YSZ8 substrate was of particular interest and, hence, the influence of thermal and ionic conduction in the substrate was studied in detail. The effect of the ion conductivity of YSZ8 was studied by measuring the resistance of a platinum conductor and the resistance between two adjacent conductors on YSZ8, in a furnace at temperatures from 20 to 930 °C and by measuring the resistance with increasing current through a conductor. With this design, the influence of ion conductivity through the substrate became apparent above 700 °C. The sensitivity of the sensor was up to 1 mΩ sccm-1 in a range of 0-10 sccm. The results show that the signal from the sensor is influenced by the integrated auxiliary heating conductors and that these auxiliary heaters provide a way to balance disturbing heat sources, e.g. thrusters or other electronics, in

  12. Shear bond strength between veneering ceramics and ceria-stabilized zirconia/alumina.

    Science.gov (United States)

    Fischer, Jens; Stawarczyk, Bogna; Sailer, Irena; Hämmerle, Christoph H F

    2010-05-01

    Ceria-stabilized tetragonal ZrO(2)/Al(2)O(3) nanocomposite (Ce-TZP/A) offers superior properties compared to yttria-stabilized zirconia (Y-TZP). However, the bond quality to veneering ceramics has not been investigated. The purpose of this study was to evaluate the bond strength of different veneering ceramics to Ce-TZP/A. Cubes of Ce-TZP/A (NANOZR) (edge length, 10 mm) were layered with veneering ceramics (5 mm in thickness) with or without application of a liner and sheared at the interface. The effect of different surface treatments (polished with 3-mum diamond paste or airborne-particle abraded) was evaluated with 1 veneering ceramic (Cerabien ZR). Shear bond strength of 5 additional veneering ceramics (IPS e.max, Initial ZR, Triceram, Vintage ZR, or VITA VM 9) to polished Ce-TZP/A was measured (n=10). Polished Y-TZP (Hint-ELs ZrO(2) HIP) veneered with 2 ceramics (Cerabien ZR, Vintage ZR) served as the control. Mean shear bond strength values (MPa) were calculated. The means were statistically analyzed with 2-way ANOVA for the effect of surface treatment and liner, 2-way ANOVA for the effect of different veneering ceramic brands and liner, and 3-way ANOVA for the effect of substrate, veneering ceramic brands, and liner, as well as 1-way ANOVA for the differences between the veneering ceramics. A post hoc Scheffé test was used (alpha=.05). The effects of surface treatment (P=.007) or application of liner (Pceramics showed bond strength values with means ranging between 14.2 +/-1.7 MPa (IPS e.max with liner) and 27.5 +/-4.2 MPa (VITA VM 9). A significant difference was found between the results of shear bond tests with Y-TZP and Ce-TZP/A (P=.022). The application of a liner on Y-TZP had no significant effect. Airborne-particle abrasion is not necessary to enhance the shear bond strength of the evaluated veneering ceramics to Ce-TZP/A. Liners impair the shear bond strength of veneering ceramics to Ce-TZP/A.

  13. A study on the phenomena of flash-sintering with tetragonal zirconia

    Science.gov (United States)

    Francis, John Stanley Curtis

    A new method for the sintering of ceramics will be presented in detail. This method called Flash-Sintering was first reported in 2010 by Cologna et al. In Flash-Sintering an electric field is applied across a "green" sample with a pair of electrodes and the sintering is measured as a function of the field and temperature. The electric field is shown to remarkably enhance densification. Both the sintering time to achieve near full density and the temperature required are reduced substantially. These changes allow for sintering of 3m% yttria stabilized zirconia at furnace temperatures below 850°C in a matter of seconds. The objective of this dissertation is to understand the phenomenological behavior of flash-sintering. This new method is a highly non-linear event which occurs at a particular temperature for a given applied field and sintering is accompanied by an abrupt rise in the conductivity. The development of relationships between the electrical control parameters, the sintering behavior, and the evolution of the microstructure are the principal themes of this doctoral research. The present work covers the following topics: (i) The influence of uniaxial pressure applied in combination with electrical field on sintering and superplastic deformation, which show an equivalence between mechanical and electrical driving forces, (ii) A shift of the flash to a higher temperature with increasing particle size of the ceramic powders, (iii) The influence of the electric field on the incubation time for the onset of the flash in experiments carried out at isothermal furnace temperatures, and the effect of the current density immediately following the flash on densification, (iv) The relationship between electrical parameters on microstructure (grain size) evolution, (v) A comparison with the microstructure and mechanical strength of specimens prepared by conventional sintering, and (vi) Measurement of luminescence spectra, which lies in the visible range, that

  14. Fracture resistance of zirconia-composite veneered crowns in comparison with zirconia-porcelain crowns.

    Science.gov (United States)

    Alsadon, Omar; Patrick, David; Johnson, Anthony; Pollington, Sarah; Wood, Duncan

    2017-02-11

    The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create 3D crown models and evaluated using FEA. The zirconia/composite crowns subjected to static occlusal load showed comparable results to the zirconia/porcelain crowns. Zirconia/composite crowns showed higher stress on the zirconia substructure at 63.6 and 50.9 MPa on the zirconia substructure veneered with porcelain. In conclusion, zirconia/composite crowns withstood high occlusal loads similar to zirconia/porcelain crowns with no significant difference. However, the zirconia/composite crowns showed higher stress values than the zirconia/porcelain crowns at the zirconia substructure.

  15. To Evaluate Effect of Airborne Particle Abrasion using Different Abrasives Particles and Compare Two Commercial Available Zirconia on Flexural Strength on Heat Treatment

    Science.gov (United States)

    Prasad, Hari A.; Pasha, Naveed; Hilal, Mohammed; Amarnath, G. S.; Kundapur, Vinaya; Anand, M; Singh, Sumeet

    2017-01-01

    Background and objective: The popularity of ceramic restorations can be attributed to its life-like appearance, durability and biocompatibility and therefore ceramic restorations have been widely used for anterior and posterior teeth. Ceramic restorations have esthetic and biocompatible advantages but low fracture resistance. Since it has high flexural strength and fracture resistance, yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is the dental material most commonly used for the core of ceramic crowns and fixed dental prosthesis. In spite of improved mechanical properties, acceptable marginal adaptation and biocompatibility the whitish opacity of zirconia is an obvious esthetic disadvantage. The zirconia framework is often veneered with conventional feldspathic porcelain to achieve a natural appearance. However it is difficult to achieve sufficient bond strength between zirconia and the veneering material. Achieving sufficient bond strength between the veneering ceramic and the zirconia core is a major challenge in the long term clinical success of veneered zirconia restorations. The main objective of this study is to evaluate the effect of different surface treatments on the fracture strength of the two commercially available Zirconia namely Ceramill and ZR-White (AMANNGIRRBACH and UPCERA) respectively. Method: Two commercially available pre-sinteredyttrium stabilized Zirconia blanks (ZR-White and Ceramill) from AMANNGIRRBACH and UPCERA respectively are used to produce the disc shaped specimens of size (15.2 ± 0.03 mm in diameter and 1.2 ± 0.03 mm thick) from each Zirconia blank. All disc shaped specimens are heated at 1200°C in a furnace for 2 hours to form homogenous tetragonal ZrO2. The dimensions of the specimens are measured with a digital caliper (aerospace). The thickness and diameter of each specimen are calculated as the means of 3 measurements made at random sites. 80 discs from each Zirconia blank are divided into ten groups of 8

  16. Effect of accelerated aging on translucency of monolithic zirconia

    Directory of Open Access Journals (Sweden)

    O. Abdelbary

    2016-12-01

    Conclusion: Thickness of zirconia has significant effect on translucency. Aging has significant effect on thinner sections of zirconia. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

  17. The influence of pigments on the slow crack growth in dental zirconia

    NARCIS (Netherlands)

    Aboushelib, M.N.; de Jager, N.; Kleverlaan, C.J.; Feilzer, A.J.

    2012-01-01

    Objectives Partially yttria stabilized zirconium oxide was introduced as core material for core-veneered full ceramic dental restorations, because of its biological inertness, high mechanical strength, and toughness. In order to improve the esthetical possibilities pigments in the core are

  18. The influence of pigments on the slow crack growth in dental zirconia

    NARCIS (Netherlands)

    Aboushelib, M.N.; de Jager, N.; Kleverlaan, C.J.; Feilzer, A.J.

    2012-01-01

    Objectives Partially yttria stabilized zirconium oxide was introduced as core material for core-veneered full ceramic dental restorations, because of its biological inertness, high mechanical strength, and toughness. In order to improve the esthetical possibilities pigments in the core are introduce

  19. Sinter-hipping of zirconia and alumina/zirconia composites

    Energy Technology Data Exchange (ETDEWEB)

    Solomah, A.G. (Kernforschungsanlage Juelich GmbH (Germany, F.R.). Inst. fuer Chemische Technologie)

    1989-01-01

    Pressureless sintered yttria-tetragonal zirconia polycrystals (Y-TZP) and yttria-partially stabilized zirconia (X-PSZ) containing different compositions of alumina (Y-PSZ/Al{sub 2}O{sub 3}) were hot-isostatically pressed, as a post-sintering processing technique, producing near theoretically dense materials (> 99.5% TD). Hipping has no measurable effect on hardness (H) and fracture toughness (K{sub IC}= of Y-TZP and Y-PSZ/Al{sub 2}O{sub 3} composites, as they were determined using Vicker's indentation technique. No changes in the crystalline phases due to hiping were observed. Low-temperature annealing has caused severe degradation to Y-TZP while for Y-PSZ/Al{sub 2}O{sub 3} composites no surface cracking was observed, but a loss in K{sub IC} was noticed, depending on Al{sub 2}O{sub 3} content. High-temperature annealing has insignificant effect on H and K{sub IC} of Y-TZP, while a loss in K{sub IC} was observed for Y-PSZ/Al{sub 2}O{sub 3} composites due to the increase in the mole fraction of cubic phase of zirconia with consistent decrease in the fraction of tetragonal phase as it has been confirmed by X-ray diffraction. (orig.).

  20. Dilemmas in zirconia bonding: A review

    Directory of Open Access Journals (Sweden)

    Obradović-Đuričić Kosovka

    2013-01-01

    Full Text Available This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

  1. Performance of Zirconia for Dental Healthcare

    Directory of Open Access Journals (Sweden)

    Ralf J. Kohal

    2010-02-01

    Full Text Available The positive results of the performance of zirconia for orthopedics devices have led the dental community to explore possible esthetical and mechanical outcomes using this material. However, questions regarding long-term results have opened strong and controversial discussions regarding the utilization of zirconia as a substitute for alloys for restorations and implants. This narrative review presents the current knowledge on zirconia utilized for dental restorations, oral implant components, and zirconia oral implants, and also addresses laboratory tests and developments, clinical performance, and possible future trends of this material for dental healthcare.

  2. Zirconia-molybdenum disilicide composites

    Science.gov (United States)

    Petrovic, John J.; Honnell, Richard E.

    1991-01-01

    Compositions of matter comprised of molybdenum disilicide and zirconium oxide in one of three forms: pure, partially stabilized, or fully stabilized and methods of making the compositions. The stabilized zirconia is crystallographically stabilized by mixing it with yttrium oxide, calcium oxide, cerium oxide, or magnesium oxide and it may be partially stabilized or fully stabilized depending on the amount of stabilizing agent in the mixture.

  3. Enamel wear opposing polished and aged zirconia.

    Science.gov (United States)

    Burgess, J O; Janyavula, S; Lawson, N C; Lucas, T J; Cakir, D

    2014-01-01

    Aging of dental zirconia roughens its surface through low temperature degradation. We hypothesized that age-related roughening of zirconia crowns may cause detrimental wear to the enamel of an opposing tooth. To test our hypothesis, we subjected artificially aged zirconia and reference specimens to simulated mastication in a wear device and measured the wear of an opposing enamel cusp. Additionally, the roughness of the pretest surfaces was measured. The zirconia specimens, artificially aged by autoclave, showed no significant increase in roughness compared to the nonaged specimens. Furthermore, no significant difference in material or opposing enamel wear between the aged and nonaged zirconia was seen. All zirconia specimens showed less material and opposing enamel wear than the enamel to enamel control or veneering porcelain specimens. Scanning electron micrographs showed relatively smooth surfaces of aged and nonaged zirconia following wear testing. The micrographs of the veneering ceramic showed sharp fractured edges and fragments of wear debris. Zirconia may be considered a wear-friendly material for restorations opposing enamel, even after simulated aging.

  4. Femtosecond laser microstructuring of zirconia dental implants

    NARCIS (Netherlands)

    Delgado-Ruiz, R. A.; Calvo-Guirado, J. L.; Moreno, P.; Guardia, J.; Gomez-Moreno, G.; Mate-Sanchez, J. E.; Ramirez-Fernandez, P.; Chiva, F.

    2011-01-01

    This study evaluated the suitability of femtosecond laser for microtexturizing cylindrical zirconia dental implants surface. Sixty-six cylindrical zirconia implants were used and divided into three groups: Control group (with no laser modification), Group A (microgropored texture), and Group 13 (mic

  5. Fitting accuracy and fracture resistance of crowns using a hybrid zirconia frame made of both porous and dense zirconia.

    Science.gov (United States)

    Nakamura, Takashi; Sugano, Tsuyoshi; Usami, Hirofumi; Wakabayashi, Kazumichi; Ohnishi, Hiroshi; Sekino, Tohru; Yatani, Hirofumi

    2015-01-01

    The purpose of this study is to evaluate the fitting accuracy and fracture resistance of crowns using a hybrid zirconia frame made of both porous and dense zirconia. Commercial semi-sintered zirconia, sintered dense zirconia and sintered hybrid zirconia were used. Sintered zirconia was milled using the CAD/CAM system, and semi-sintered zirconia was milled and sintered to fabricate molar crown frames. Completed frames were veneered with tooth-colored porcelain. The marginal and internal gaps between frames/crowns and abutments were measured. Each crown specimen was subjected to a fracture test. There were no significant differences in marginal and internal gap among all the frames and crowns. The crown with the hybrid zirconia frame had a 31-35% greater fracture load than that with the commercial or dense zirconia frame (pcrowns with a hybrid zirconia frame have a high fracture resistance.

  6. Catastrophic failure of a monolithic zirconia prosthesis.

    Science.gov (United States)

    Chang, Jae-Seung; Ji, Woon; Choi, Chang-Hoon; Kim, Sunjai

    2015-02-01

    Recently, monolithic zirconia restorations have received attention as an alternative to zirconia veneered with feldspathic porcelain to eliminate chipping failures of veneer ceramics. In this clinical report, a patient with mandibular edentulism received 4 dental implants in the interforaminal area, and a screw-retained monolithic zirconia prosthesis was fabricated. The patient also received a maxillary complete removable dental prosthesis over 4 anterior roots. At the 18-month follow-up, all of the zirconia cylinders were seen to be fractured, and the contacting abutment surfaces had lost structural integrity. The damaged abutments were replaced with new abutments, and a new prosthesis was delivered with a computer-assisted design and computer-assisted manufacturing fabricated titanium framework with denture teeth and denture base resins. At the 6-month recall, the patient did not have any problems. Dental zirconia has excellent physical properties; however, care should be taken to prevent excessive stresses on the zirconia cylinders when a screw-retained zirconia restoration is planned as a definitive prosthesis.

  7. Doped Zirconia/Ceria Electrolyte Fabricated at Low Temperature%低温制备掺杂氧化锆/氧化铈电解质

    Institute of Scientific and Technical Information of China (English)

    刘泽; 雷泽; 宋世栋; 于立安; 韩敏芳

    2011-01-01

    固体氧化物燃料电池(SOFC)及其组元的低温制备有利于材料和电池性能的优化,降低制备成本.立方相的全致密氧化钇稳定氧化锆(YSZ)电解质是SOFC中最通用的电解质.传统的烧结工艺需要在1 400-1 450℃才能实现YSZ电解质的致密,而使用纳米粉体和三步烧结工艺可以在1 200-1 300℃得到致密电解质.氧化钪稳定氧化锆(ScSZ)电解质可以使用3nm的粉体在900℃下致密化,氧化钆掺杂的氧化铈可以通过加入烧结助剂在800℃下实现致密化烧结,这些工艺已广泛用于SOFC制备.SOFC的低温制备工艺可有效推进SOFC的产业化.%The manufacturing of solid oxide fuel cell (SOFC) and its main components at low temperature are very important to optimise the performance of material, cell and lower the cost. The cubic full dense yttria stabilized zirconia (YSZ) electrolyte, one of the most popular electrolyte in SOFC, is obtained by three-step sintering process at 1 200-1 300℃ from nano powders, which needs to be dense at 1 400-1 450℃ by traditional sintering process. The scandia stabilized zirconia (ScSZ) and gadolinia doped ceria (GDC) electrolytes are sintered to be full dense respectively at low temperature of 900℃ and 800℃ from 3nm powders of ScSZ and by sintering additives, which, now, are widely used in SOFC process. The low temperature process of SOFC would be benefit to put forward SOFC commercial ization in the market.

  8. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    Energy Technology Data Exchange (ETDEWEB)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J. [Department of Materials Science and Engineering, NC State University, EB-1, Raleigh, North Carolina 27695-7907 (United States)

    2013-06-21

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 Multiplication-Sign 10{sup -9} s) at lower energies. Microstructural studies, conducted by X-ray diffraction ({theta}-2{theta} and {phi} techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO<111 > Double-Vertical-Line Double-Vertical-Line c-YSZ<001> and in-plane NiO<110> Double-Vertical-Line Double-Vertical-Line c-YSZ<100>. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min{sup -1} for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies

  9. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    Science.gov (United States)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J.

    2013-06-01

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 × 10-9 s) at lower energies. Microstructural studies, conducted by X-ray diffraction (θ-2θ and φ techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO⟨111 ⟩||c-YSZ⟨001⟩ and in-plane NiO⟨110⟩||c-YSZ⟨100⟩. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min-1 for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies ease the adsorption of 4-chlorophenol, hydroxyl, and water molecules to the surface. Thus, n

  10. Osteoblast response to zirconia surfaces with different topographies

    Energy Technology Data Exchange (ETDEWEB)

    Herath, H.M.T.U. [Department of Medical Laboratory Science, Faculty of Allied Health Sciences, University of Peradeniya (Sri Lanka); Di Silvio, L. [Guy' s, King' s and St Thomas' Medical and Dental Institute, King' s College London, London SE1 9RT (United Kingdom); Evans, J.R.G., E-mail: j.r.g.evans@ucl.ac.uk [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2015-12-01

    Zirconia-3 mol% yttria ceramics were prepared with as-sintered, abraded, polished, and porous surfaces in order to explore the attachment, proliferation and differentiation of osteoblast-like cells. After modification, all surfaces were heated to 600 °C to extinguish traces of organic contamination. All surfaces supported cell attachment, proliferation and differentiation but the surfaces with grain boundary grooves or abraded grooves provided conditions for enhanced initial cell attachment. Nevertheless, overall cell proliferation and total DNA were highest on the polished surface. Zirconia sintered at a lower temperature (1300 °C vs. 1450 °C) had open porosity and presented reduced proliferation as assessed by alamarBlue™ assay, possibly because the openness of the pores prevented cells developing a local microenvironment. All cells retained the typical polygonal morphology of osteoblast-like cells with variations attributable to the underlying surface notably alignment along the grooves of the abraded surface. - Highlights: • Biocompatibility of chemically identical, topologically different ZrO{sub 2} was tested. • ZrO{sub 2} promoted cell adhesion, proliferation, differentiation and nodule formation. • Proliferation was high on polished ZrO{sub 2} but initial recruitment was high on abraded ZrO{sub 2}. • With open porosity, proliferation was low; cells cannot establish a microenvironment.

  11. Alignment validation

    Energy Technology Data Exchange (ETDEWEB)

    ALICE; ATLAS; CMS; LHCb; Golling, Tobias

    2008-09-06

    The four experiments, ALICE, ATLAS, CMS and LHCb are currently under constructionat CERN. They will study the products of proton-proton collisions at the Large Hadron Collider. All experiments are equipped with sophisticated tracking systems, unprecedented in size and complexity. Full exploitation of both the inner detector andthe muon system requires an accurate alignment of all detector elements. Alignmentinformation is deduced from dedicated hardware alignment systems and the reconstruction of charged particles. However, the system is degenerate which means the data is insufficient to constrain all alignment degrees of freedom, so the techniques are prone to converging on wrong geometries. This deficiency necessitates validation and monitoring of the alignment. An exhaustive discussion of means to validate is subject to this document, including examples and plans from all four LHC experiments, as well as other high energy experiments.

  12. In situ redox cycle of a nickel–YSZ fuel cell anode in an environmental transmission electron microscope

    DEFF Research Database (Denmark)

    Jeangros, Quentin; Faes, Antonin; Wagner, Jakob Birkedal

    2010-01-01

    Environmental transmission electron microscopy is used in combination with density functional theory calculations to study the redox stability of a nickel/yttria-stabilized zirconia solid oxide fuel cell anode. The results reveal that the transfer of oxygen from NiO to yttria-stabilized zirconia...... triggers the reduction reaction. During Ni reoxidation, the creation of a porous structure, due to mass transport, accounts for the redox instability of the Ni-based anode. Both the expansion of NiO during a redox cycle and the presence of stress in the yttria-stabilized zirconia grains are observed...

  13. Development of Corundum—Mullite—Zirconia Clinkers

    Institute of Scientific and Technical Information of China (English)

    LIUXin-yu; SUNGeng-chen; 等

    1994-01-01

    The properties of corundum-mullite-zirco-nia clinkers made by reaction-sintering have been investigated.It is shown that corundum-mullite-zirconia clinkers exhibit lower sintering tempera-ture as well as better thermal shock resistance and corrosion resistance,The carbon-bonded alu-mina-mullite-zirconia material possesses satis-factory properties and may have prospects for application in severe process environments such as continuous casting.

  14. An overview of monolithic zirconia in dentistry

    Directory of Open Access Journals (Sweden)

    Özlem Malkondu

    2016-07-01

    Full Text Available Zirconia restorations have been used successfully for years in dentistry owing to their biocompatibility and good mechanical properties. Because of their lack of translucency, zirconia cores are generally veneered with porcelain, which makes restorations weaker due to failure of the adhesion between the two materials. In recent years, all-ceramic zirconia restorations have been introduced in the dental sector with the intent to solve this problem. Besides the elimination of chipping, the reduced occlusal space requirement seems to be a clear advantage of monolithic zirconia restorations. However, scientific evidence is needed to recommend this relatively new application for clinical use. This mini-review discusses the current scientific literature on monolithic zirconia restorations. The results of in vitro studies suggested that monolithic zirconia may be the best choice for posterior fixed partial dentures in the presence of high occlusal loads and minimal occlusal restoration space. The results should be supported with much more in vitro and particularly in vivo studies to obtain a final conclusion.

  15. Zirconia in dental implantology: A review

    Science.gov (United States)

    Apratim, Abhishek; Eachempati, Prashanti; Krishnappa Salian, Kiran Kumar; Singh, Vijendra; Chhabra, Saurabh; Shah, Sanket

    2015-01-01

    Background: Titanium has been the most popular material of choice for dental implantology over the past few decades. Its properties have been found to be most suitable for the success of implant treatment. But recently, zirconia is slowly emerging as one of the materials which might replace the gold standard of dental implant, i.e., titanium. Materials and Methods: Literature was searched to retrieve information about zirconia dental implant and studies were critically analyzed. PubMed database was searched for information about zirconia dental implant regarding mechanical properties, osseointegration, surface roughness, biocompatibility, and soft tissue health around it. The literature search was limited to English language articles published from 1975 to 2015. Results: A total of 45 papers met the inclusion criteria for this review, among the relevant search in the database. Conclusion: Literature search showed that some of the properties of zirconia seem to be suitable for making it an ideal dental implant, such as biocompatibility, osseointegration, favourable soft tissue response and aesthetics due to light transmission and its color. At the same time, some studies also point out its drawbacks. It was also found that most of the studies on zirconia dental implants are short-term studies and there is a need for more long-term clinical trials to prove that zirconia is worth enough to replace titanium as a biomaterial in dental implantology. PMID:26236672

  16. The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth

    Directory of Open Access Journals (Sweden)

    Widowati Siswomihardjo

    2012-01-01

    . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony.

  17. Beyond Alignment

    DEFF Research Database (Denmark)

    Beyond Alignment: Applying Systems Thinking to Architecting Enterprises is a comprehensive reader about how enterprises can apply systems thinking in their enterprise architecture practice, for business transformation and for strategic execution. The book's contributors find that systems thinking...... is a valuable way of thinking about the viable enterprise and how to architect it....

  18. Nanosilica coating for bonding improvements to zirconia

    Directory of Open Access Journals (Sweden)

    Chen C

    2013-10-01

    Full Text Available Chen Chen, Gang Chen, Haifeng Xie, Wenyong Dai, Feimin Zhang Institute of Stomatology, Nanjing Medical University, Nanjing, Jiangsu Province, People's Republic of China Abstract: Resin bonding to zirconia cannot be established from standard methods that are currently utilized in conventional silica-based dental ceramics. The solution–gelatin (sol–gel process is a well developed silica-coating technique used to modify the surface of nonsilica-based ceramics. Here, we use this technique to improve resin bonding to zirconia, which we compared to zirconia surfaces treated with alumina sandblasting and tribochemical silica coating. We used the shear bond strength test to examine the effect of the various coatings on the short-term resin bonding of zirconia. Furthermore, we employed field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and Fourier transform infrared spectroscopy to characterize the zirconia surfaces. Water–mist spraying was used to evaluate the durability of the coatings. To evaluate the biological safety of the experimental sol–gel silica coating, we conducted an in vitro Salmonella typhimurium reverse mutation assay (Ames mutagenicity test, cytotoxicity tests, and in vivo oral mucous membrane irritation tests. When compared to the conventional tribochemical silica coating, the experimental sol–gel silica coating provided the same shear bond strength, higher silicon contents, and better durability. Moreover, we observed no apparent mutagenicity, cytotoxicity, or irritation in this study. Therefore, the sol–gel technique represents a promising method for producing silica coatings on zirconia. Keywords: zirconia, bond, silica coating, tribochemical silica coating, biocompatibility

  19. Phase transformation of zirconia ceramics by hydrothermal degradation

    OpenAIRE

    Kawai, Yohei; Uo, Motohiro; Wang, Yong ming; Kono, Sayaka; Ohnuki, Somei; Watari, Fumio

    2011-01-01

    Zirconia has found wide application in dentistry because of its high mechanical strength and superior esthetic properties. However, zirconia degradation caused by phase transformation occurring in a hydrothermal environment is of concern. In the present study, phase transformation and microstructure of tetragonal zirconia polycrystal partially stabilized with yttrium oxide (Y-TZP) and alumina-toughened zirconia (ATZ) sintered at different temperatures were estimated. On grazing angle X-ray di...

  20. Self-supported ceramic substrates with directional porosity by mold freeze casting

    DEFF Research Database (Denmark)

    Gurauskis, Jonas; Graves, Christopher R.; Moreno, R.

    2016-01-01

    Manufacture of thin-film ceramic substrates with high permeability and robustness is of high technological interest. In this work thin (green state thickness ∼500 μm) porous yttria-stabilized zirconia self-supported substrates were fabricated by pouring stable colloidal aqueous suspensions...... in a mold and applying directional freeze casting. Use of optimized suspension, cryoprotector additive and mold proved to deliver defect free ceramic films with high dimensional control. Microstructure analysis demonstrated the formation of desirable aligned porosity at macro-structural scale and resulted...

  1. Nickel/Yttria-stabilised zirconia cermet anodes for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Primdahl, S.

    1999-08-01

    This thesis deals with the porous Ni/yttria-stabilized zirconia (YSZ) cermet anode on a YSZ electrolyte for solid oxide fuel cells (SOFC). Such anodes are predominantly operated in moist hydrogen at 700 deg. C to 1000 deg. C, and the most important technological parameters are the polarization resistance and the long-term stability. The polarization resistance can be measured by a number of techniques, in the present work impedance spectroscopy has been used extensively. By impedance spectroscopy limiting processes in the anode polarization resistance may often be separated and characterized individually, provided they have a reasonable separation in time constants. Three limiting processes are recognized in impedance spectra obtained on technological Ni/YSZ cermet anodes characterized against a stable reference electrode atmosphere. By parameter studies and illustrative experiments, the two contributions at low and medium frequency have been identified as gas conversion and diffusion limitations, respectively. Both of these effects are concentration limitations relating to the inefficient exchange of fuel gas in the test setup outside the porous cermet. A test setup geometry where these concentration effects are avoided for high-performance electrodes is recommended. The high frequency limitation is demonstrated to relate to the cermet structure. The dependence on gas composition, temperature, adsorbed species (sulfur), isotopes (H/D), sintering temperature and cermet thickness is investigated. Despite these studies and several similar studies by others, the exact chemical or physical nature of the limiting step has not been incontestably identified. However, these is a general consensus in literature about the hydrogen oxidation process taking place on or near to the triple phase boundary (TPB) line, where open gas-filled pores, the continuous electrolyte phase (oxide ion cunductor) and the continuous Ni phase (electronic conductor) meet. The physical thickness

  2. Tribological characterization of zirconia coatings deposited on Ti6Al4V components for orthopedic applications.

    Science.gov (United States)

    Berni, M; Lopomo, N; Marchiori, G; Gambardella, A; Boi, M; Bianchi, M; Visani, A; Pavan, P; Russo, A; Marcacci, M

    2016-05-01

    One of the most important issues leading to the failure of total joint arthroplasty is related to the wear of the plastic components, which are generally made of ultra high molecular weight polyethylene (UHMWPE). Therefore, the reduction of joint wear represents one of the main challenges the research in orthopedics is called to address nowadays. Surface treatments and coatings have been recognized as innovative methods to improve tribological properties, also in the orthopedic field. This work investigated the possibility to realize hard ceramic coatings on the metal component of a prosthesis, by means of Pulsed Plasma Deposition, in order to reduce friction and wear in the standard coupling against UHMWPE. Ti6Al4V substrates were coated with a 2 μm thick yttria-stabilized zirconia (YSZ) layer. The mechanical properties of the YSZ coatings were assessed by nanoindentation tests performed on flat Ti6Al4V substrates. Tribological performance was evaluated using a ball-on-disk tribometer in dry and lubricated (i.e. with fetal bovine serum) highly-stressing conditions, up to an overall distance of 10 km. Tribology was characterized in terms of coefficient of friction (CoF) and wear rate of the UHMWPE disk. After testing, specimens were analyzed through optical microscopy and SEM images, in order to check the wear degradation mechanisms. Progressive loading scratch tests were also performed in dry and wet conditions to determine the effects of the environment on the adhesion of the coating. Our results supported the beneficial effect of YSZ coating on metal components. In particular, the proposed solution significantly reduced UHMWPE wear rate and friction. At 10 km of sliding distance, a wear rate reduction of about 18% in dry configuration and of 4% in presence of serum, was obtained by the coated group compared to the uncoated group. As far as friction in dry condition is concerned, the coating allowed to maintain low CoF values until the end of the tests, with an

  3. Zirconia batter separators: An historical perspective and development update

    Energy Technology Data Exchange (ETDEWEB)

    Hamling, P. [ZIRCAR Products Inc., Florida, NY (United States); Hamling, B.H. [ZIRCAR Products Inc., Kingston, NY (United States)

    1996-11-01

    Zirconia cloth battery separators have been widely accepted for use in nickel-hydrogen and select nickel cadmium aerospace batteries. A discussion of the characteristics, properties and applications of two grades of zirconia cloth is presented. Additionally a status report on the development, characteristics and properties plus intended applications of a novel zirconia paper is offered.

  4. Tribological properties of nanoscale alumina-zirconia composites

    NARCIS (Netherlands)

    Kerkwijk, B.; Winnubst, A.J.A.; Verweij, H.; Mulder, E.J.; Metselaar, H.S.C.; Schipper, D.J.

    1999-01-01

    The tribological properties of zirconia (Y-TZP), alumina and their composites, alumina dispersed in zirconia (ADZ) and zirconia-toughened alumina (ZTA), were investigated. These ceramics are made by colloidal processing methods such that well-defined, homogeneous microstructures with submicron grain

  5. Partial-retainer design considerations for zirconia restorations

    NARCIS (Netherlands)

    M.N. Aboushelib; A.J. Feilzer; C.J. Kleverlaan; Z. Salameh

    2010-01-01

    Objective: Bond strength limitations of adhesive zirconia restorations have stood as a barrier against their widespread use. Selective infiltration etching is a new surface treatment that enhances bonding to zirconia-based materials. Beside bond strength, the performance of adhesive zirconia restora

  6. Bonding between layering materials and zirconia frameworks

    Directory of Open Access Journals (Sweden)

    Futoshi Komine

    2012-08-01

    Full Text Available The availability of zirconium dioxide (zirconia ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. This article reviews the literature on the bond strength between layering materials and zirconia frameworks used in dental restorations. Database searches were conducted for in vitro studies of bond strength between layering materials and zirconia frameworks. The search was carried out in different electronic databases, supplemented by handsearch in dental journals and by examination of the bibliographies of the retrieved articles. A variety of studies on bond strength was identified, including comparisons with metal–ceramic systems and studies on mismatched coefficients of thermal expansion, the use of press-on ceramics or liner materials, and the effect of cooling time after firing. The available data provide considerable information on achieving stable layering of material/zirconia composites. However, only a few in vitro studies on bond strength between indirect composites and zirconia were identified. Such studies and additional controlled clinical trials are needed.

  7. Fabrication and characterization of dense zirconia and zirconia-silica ceramic nanofibers.

    Science.gov (United States)

    Xu, Xiaoming; Guo, Guangqing; Fan, Yuwei

    2010-09-01

    The objective of this study was to prepare dense zirconia-yttria (ZY), zirconia-silica (ZS) and zirconia-yttria-silica (ZYS) nanofibers as reinforcing elements for dental composites. Zirconium (IV) propoxide, yttrium nitrate hexahydrate, and tetraethyl orthosilicate (TEOS) were used as precursors for the preparation of zirconia, yttria, and silica sols. A small amount (1-1.5 wt%) of polyethylene oxide (PEO) was used as a carry polymer. The sols were preheated at 70 degrees C before electrospinning and their viscosity was measured with a viscometer at different heating time. The gel point was determined by viscosity-time (eta-t) curve. The ZY, ZS and ZYS gel nanofibers were prepared using a special reactive electrospinning device under the conditions near the gel point. The as-prepared gel nanofibers had diameters between 200 and 400 nm. Dense (nonporous) ceramic nanofibers of zirconia-yttria (96/4), zirconia-silica (80/20) and zirconia-yttria-silica (76.8/3.2/20) with diameter of 100-300 nm were obtained by subsequent calcinations at different temperatures. The gel and ceramic nanofibers obtained were characterized by scanning electron microscope (SEM), high-resolution field-emission scanning electron microscope (FE-SEM), thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), Fourier transform infrared spectrometer (FT-IR), and X-ray diffraction (XRD). SEM micrograph revealed that ceramic ZY nanofibers had grained structure, while ceramic ZS and ZYS nanofibers had smooth surfaces, both showing no visible porosity under FE-SEM. Complete removal of the polymer PEO was confirmed by TGA/DSC and FT-IR. The formation of tetragonal phase of zirconia and amorphous silica was proved by XRD. In conclusion, dense zirconia-based ceramic nanofibers can be fabricated using the new reactive sol-gel electrospinning technology with minimum organic polymer additives.

  8. Effect of an experimental zirconia-silica coating technique on micro tensile bond strength of zirconia in different priming conditions

    NARCIS (Netherlands)

    Chen, C.; Kleverlaan, C.J.; Feilzer, A.J.

    2012-01-01

    Objectives This study aimed to evaluate the adhesive properties of a MDP-containing resin cement to a colored zirconia ceramic, using an experimental zirconia-silica coating technique with different priming conditions. Methods 18 zirconia ceramic discs (Cercon base colored) were divided into two gro

  9. Stabilization of mesoporous nanocrystalline zirconia with Laponite

    Institute of Scientific and Technical Information of China (English)

    LIU Xinmei; YAN Zifeng; LU Gaoqing

    2005-01-01

    The mesoporous nanocrystalline zircoina was synthesized via solid state reaction--structure directing method in the presence of Laponite. The introduction of Laponite renders the higher thermal stability and lamellar track to the zirconia. Laponite acts as inhibitor for crystal growth and also hard template for the mesostructure. The role of Laponite is attributed to the interaction between the zirconia precursors and the nano-platelets of Laponite via the bridge of hydrophilic segments of surfactant. It results in the formation of Zr-O-Mg-O-Si frameworks in the direction of Laponite layer with the condensation of frameworks during the calcination process, which contributes the higher stability and lamellar structure to the nano-sized zirconia samples.

  10. Dense zig-zag microstructures in YSZ thin films by pulsed laser deposition

    Directory of Open Access Journals (Sweden)

    Dieter Stender

    2015-01-01

    Full Text Available The very brittle oxygen ion conductor yttria stabilized zirconia (YSZ is a typical solid electrolyte for miniaturized thin film fuel cells. In order to decrease the fuel cell operating temperature, the thickness of yttria stabilized zirconia thin films is reduced. Often, these thin membranes suffer from mechanical failure and gas permeability. To improve these mechanical issues, a glancing angle deposition approach is used to grow yttria stabilized zirconia thin films with tilted columnar structures. Changes of the material flux direction during the deposition result in a dense, zigzag-like structure with columnar crystallites. This structure reduces the elastic modulus of these membranes as compared to columnar yttria stabilized zirconia thin films as monitored by nano-indentation which makes them more adaptable to applied stress.

  11. Chipping resistance of graded zirconia ceramics for dental crowns.

    Science.gov (United States)

    Zhang, Y; Chai, H; Lee, J J-W; Lawn, B R

    2012-03-01

    A serious drawback of veneering porcelains is a pronounced susceptibility to chipping. Glass-infiltrated dense zirconia structures can now be produced with esthetic quality, making them an attractive alternative. In this study, we examined the hypothesis that such infiltrated structures are much more chip-resistant than conventional porcelains, and at least as chip-resistant as non-infiltrated zirconia. A sharp indenter was used to produce chips in flat and anatomically correct glass-infiltrated zirconia crown materials, and critical loads were measured as a function of distance from the specimen edge (flat) or side wall (crown). Control data were obtained on zirconia specimens without infiltration and on crowns veneered with porcelains. The results confirmed that the resistance to chipping in graded zirconia is more than 4 times higher than that of porcelain-veneered zirconia and is at least as high as that of non-veneered zirconia.

  12. Influence of new universal adhesives and zirconia primer application techniques on zirconia repair

    OpenAIRE

    Seabra, Bruno

    2012-01-01

    Tese de mestrado, Medicina Dentária, Universidade de Lisboa, Faculdade de Medicina Dentária, 2012 INTRODUCTION The protocol traditionally used for bonding composite resin to feldspathic ceramic is not effective to promote adhesion to Zirconia. In the last years, different methods have been studied to achieve that purpose. The development of new primers and adhesives containing phosphate monomers (MDP), have shown promising results. OBJECTIVES To investigate the influence of a zirconia prim...

  13. Crystal structure of zirconia by Rietveld refinement

    Institute of Scientific and Technical Information of China (English)

    王大宁; 郭永权; 梁开明; 陶琨

    1999-01-01

    The crystal structures and phase transformation of zirconia ceramics have been investigated by means of X-ray powder diffraction and Rietveld powder diffraction profile fitting technique. A structural transition from monoclinic to tetragonal occurs when Y2O3 and CeO2 are doped into zirconia. The space group of the tetragonal structure is P42/nmc, Z=2. The lattice parameters are α=0.362 6(5) nm, c=0.522 6(3)nm for CeO2 doped zirconia and α=0. 360 2(8)nm, c=0. 517 9(1)nm for Y2O3 doped zirconia, respectively. In each unit cell, there are two kinds of equivalent positions, i. e. 2b and 4d, which are occupied by Zr4+, M(M=Y3+, Ce4+) cations and O2- anions, respectively. The crystallographic correlation among the cubic, tetragonal and monoclinic structures of ZrO2 is discussed.

  14. Direct silanization of zirconia for increased biointegration.

    Science.gov (United States)

    Caravaca, Carlos; Shi, Liu; Balvay, Sandra; Rivory, Pascaline; Laurenceau, Emmanuelle; Chevolot, Yann; Hartmann, Daniel; Gremillard, Laurent; Chevalier, Jérôme

    2016-12-01

    High-performance bioinert ceramics such as zirconia have been used for biomedical devices since the early seventies. In order to promote osseointegration, the historical solution has been to increase the specific surface of the implant through roughness. Nevertheless these treatments on ceramics may create defects at the surface, exposing the material to higher chances of early failure. In zirconia, such treatments may also affect the stability of the surface. More recently, the interest of improving osseointegration of implants has moved the research focus towards the actual chemistry of the surface. Inspired by this, we have adapted the current knowledge and techniques of silica functionalization and applied it to successfully introduce 3-aminopropyldimethylethoxy silane (APDMES) directly on the surface of zirconia (3Y-TZP). We used plasma of oxygen to clean the surface and promote hydroxylation of the surface to increase silane density. The samples were extensively characterized by means of X-ray photoelectron spectroscopy (XPS) and contact angle, mechanically tested and its cytotoxicity was evaluated through cell adhesion and proliferation tests. Additionally, aging was studied to discard negative effects of the treatment on the stability of the tetragonal phase. No adverse effect was found on the mechanical response of treated samples. In addition, plasma-treated samples exhibited an unexpectedly higher resistance to aging. Finally, silane density was 35% lower than the one reported in literature for silica. However cells displayed a qualitatively higher spreading in opposition to the rounder appearance of cells on untreated zirconia. These results lay the foundations for the next generation of zirconia implants with biologically friendlier surfaces.

  15. The effect of graded glass-zirconia structure on the bond between core and veneer in layered zirconia restorations.

    Science.gov (United States)

    Liu, Ruoyu; Sun, Ting; Zhang, Yanli; Zhang, Yaokun; Jiang, Danyu; Shao, Longquan

    2015-06-01

    The aim of this study was to test the hypothesis that a graded glass-zirconia structure can strengthen the core-veneer bond in layered zirconia materials. A graded glass-zirconia structure was fabricated by infiltrating glass compositions developed in our laboratory into a presintered yttria tetrahedral zirconia polycrystal (Y-TZP) substrate by the action of capillary forces. The wettability of the infiltrated glass and Y-TZP substrate was investigated by the sessile drop technique. The microstructures of the graded glass-zirconia structure were examined by scanning electron microscopy (SEM). The phase structure characterization in the graded glass-zirconia structure were identified by X-ray diffraction (XRD) analysis. The elastic modulus and hardness of the graded glass-zirconia structure were evaluated from nanoindentations. Further, the shear bond strength (SBS) of the graded glass-zirconia structure and veneering porcelain was also evaluated. SEM images confirmed the formation of the graded glass-zirconia structure. Glass frits wet the Y-TZP substrate at 1200 °C with a contact angle of 43.2°. Only a small amount of t-m transformation was observed in as-infiltrated Y-TZP specimens. Nanoindentation studies of the glass-zirconia graded structure showed that the elastic modulus and hardness of the surface glass layer were higher than those of the dense Y-TZP layer. The mean SBS values for the graded glass-zirconia structure and veneering porcelain (24.35 ± 0.40 MPa) were statistically higher than those of zirconia and veneering porcelain (9.22 ± 0.20 MPa) (Pglass-zirconia structure can be fabricated by the glass infiltration/densification technique, and this structure exhibits a strong core-veneer bond. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Injection of Aqueous Slurry for Making Zirconia Fiber

    Institute of Scientific and Technical Information of China (English)

    HE Shun'ai; LI Maoqiang

    2009-01-01

    Zirconia aqueous slurry was prepared with fine zirconia powder.Injection process for making zirconia fiber was demonstrated,including preparation of aqueous slurry,injection of slurry,fiber setting in acetone,and fiber firing.The principle of the process was discussed.The effects of solid loading in the zirconia slurry,addition of dispersant in the slurry,and ball milling time on the rheological properties of the slurry,especially yield stress,were illustrated.The role of acetone as curing agent was discussed.Zirconia poly-crystalline fber with at 1 530 ℃ for 5 h.Microstructure of the sintered zirconia fiber was investigated.

  17. Effects of cementation surface modifications on fracture resistance of zirconia

    Science.gov (United States)

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  18. State of the art of zirconia for dental applications.

    Science.gov (United States)

    Denry, Isabelle; Kelly, J Robert

    2008-03-01

    Zirconia has been recently introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures, in combination with CAD/CAM techniques. This review encompasses the specific types of zirconia available in dentistry, together with their properties. The two main processing techniques, soft and hard machining, are assessed in the light of their possible clinical implications and consequences on the long-term performance of zirconia. An update on the status of clinical trials occurring worldwide is provided.

  19. Effect of Zirconia Thickness on the Tensile Stress of Zirconia Based All-Ceramic Restorations

    Directory of Open Access Journals (Sweden)

    Masood Shiezadeh

    2015-09-01

    Full Text Available Introduction: The purpose of the presented study was to evaluate the effect of zirconia thickness on the tensile stress of zirconia based all-ceramic restorations. Methods: Twenty zirconia disks with 10mm diameter were prepared in two groups using CAD/CAM system. The thickness of zirconia was 0.5mm in first group and 0.3mm in second group. After sintering, 0.4mm glass ceramic porcelain was applied to each disk. Then, sintering and glazing of porcelain carried out. Instron testing machine with 1mm/min crosshead speed used to evaluate the failure load of the samples. Biaxial Flexural strength standard formula employed to calculate tensile stress of specimens. Statistical analysis performed using SPSS software. Results: Although data analysis showed more maximum tensile stress in 1st group, no significant differences were found between two groups. Conclusion: Zirconia with 0.5mm and 0.3mm thicknesses cause similar tensile stress in all-ceramic restorations and thickness of these laminates could be reduced to 0.7mm.

  20. Novel fabrication method for zirconia restorations: bonding strength of machinable ceramic to zirconia with resin cements.

    Science.gov (United States)

    Kuriyama, Soichi; Terui, Yuichi; Higuchi, Daisuke; Goto, Daisuke; Hotta, Yasuhiro; Manabe, Atsufumi; Miyazaki, Takashi

    2011-01-01

    A novel method was developed to fabricate all-ceramic restorations which comprised CAD/CAM-fabricated machinable ceramic bonded to CAD/CAM-fabricated zirconia framework using resin cement. The feasibility of this fabrication method was assessed in this study by investigating the bonding strength of a machinable ceramic to zirconia. A machinable ceramic was bonded to a zirconia plate using three kinds of resin cements: ResiCem (RE), Panavia (PA), and Multilink (ML). Conventional porcelain-fused-to-zirconia specimens were also prepared to serve as control. Shear bond strength test (SBT) and Schwickerath crack initiation test (SCT) were carried out. SBT revealed that PA (40.42 MPa) yielded a significantly higher bonding strength than RE (28.01 MPa) and ML (18.89 MPa). SCT revealed that the bonding strengths of test groups using resin cement were significantly higher than those of Control. Notably, the bonding strengths of RE and ML were above 25 MPa even after 10,000 times of thermal cycling -adequately meeting the ISO 9693 standard for metal-ceramic restorations. These results affirmed the feasibility of the novel fabrication method, in that a CAD/CAM-fabricated machinable ceramic is bonded to a CAD/CAM-fabricated zirconia framework using a resin cement.

  1. Fission Enhanced diffusion of uranium in zirconia

    CERN Document Server

    Bérerd, N; Moncoffre, N; Sainsot, P; Faust, H; Catalette, H

    2005-01-01

    This paper deals with the comparison between thermal and Fission Enhanced Diffusion (FED) of uranium into zirconia, representative of the inner face of cladding tubes. The experiments under irradiation are performed at the Institut Laue Langevin (ILL) in Grenoble using the Lohengrin spectrometer. A thin $^{235}UO\\_2$ layer in direct contact with an oxidized zirconium foil is irradiated in the ILL high flux reactor. The fission product flux is about 10$^{11}$ ions cm$^{-2}$ s$^{-1}$ and the target temperature is measured by an IR pyrometer. A model is proposed to deduce an apparent uranium diffusion coefficient in zirconia from the energy distribution broadening of two selected fission products. It is found to be equal to 10$^{-15}$ cm$^2$ s$^{-1}$ at 480$\\circ$C and compared to uranium thermal diffusion data in ZrO$\\_2$ in the same pressure and temperature conditions. The FED results are analysed in comparison with literature data.

  2. Yttria Tetragonal Zirconia Biomaterials: Kinetic Investigation

    Institute of Scientific and Technical Information of China (English)

    Ezzat S. Elshazly; S.M. El-Hout; M. El-Sayed Ali

    2011-01-01

    The low temperature aging behavior of polycrystalline tetragonal zirconia was investigated to explore the effects on phase transformation occurring during the process. XRD analysis was conducted for the phase identification and the tetragonal to monoclinic phase transformation was determined. The aging of tetragonal zirconia polycrystals doped with 3 mol% Y2O3 triggers tetragonal to monoclinic phase transformation on the surface of the specimen only, while the penetration inside the bulk of the specimen is very limited. A slight decrease in the mechanical properties was also observed after aging for 40 h. The transformation kinetics show a nucleation and growth mechanism on the specimen surface to be dominant in the iow temperature aging in water environment.

  3. Microstructural evolution of alumina-zirconia nanocomposites; Evolucao microestrutural de nanocompositos alumina-zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Ojaimi, C.L.; Chinelatto, A.S.A.; Chinelatto, A.L. [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil); Pallone, E.M.J.A., E-mail: christianelago@yahoo.com.br [Universidade de Sao Paulo (USP), Pirassununga, Sao Paulo, SP (Brazil). Faculdade de Zootecnia e Engenharia de Alimentos

    2012-07-01

    Ceramic materials have limited use due to their brittleness. The inclusion of nanosized particles in a ceramic matrix, which are called nanocomposites, and ceramic processing control by controlling the grain size and densification can aid in obtaining ceramic products of greater strength and toughness. Studies showed that the zirconia nano inclusions in the matrix of alumina favors an increase in mechanical properties by inhibiting the grain growth of the matrix and not by the mechanism of the transformation toughening phase of zirconia. In this work, the microstructural evolution of alumina nanocomposites containing 15% by volume of nanometric zirconia was studied. From the results it was possible to understand the sintering process of these nanocomposites. (author)

  4. Evaluation of zirconia bonding to veneering porcelain

    Directory of Open Access Journals (Sweden)

    Aneta Mijoska

    2014-10-01

    Full Text Available Zirconium dioxide as core ceramic material for dental crowns and bridges, possess high strength, chemical stability and superior aesthetics after veneering. Veneering ceramic is considered to be the weakest part of all-ceramic restorations. The adhesion between the core and veneering porcelain is based on the manner in which the connection occurs in metal-ceramic structures. Standard procedures for connecting zirconia to hard dental tissues and veneering materials do not achieve the required strength of bonding. The aim of the paper is to investigate different surface treatments of the zirconium dioxide ceramic core and find the best, for achieving highest adhesive bonding values to veneering porcelain. The study was primarily designed to investigate the bonding strength of the veneering porcelain to zirconia with in vitro Macro shear bond strength test. The specimens with different surface treatment of the zirconia were divided in five groups of twelve according to the treatment of zirconium surface and results showed highest bonding values for specimens treated with Rocatec system.

  5. Innovations in bonding to zirconia-based materials: Part I

    NARCIS (Netherlands)

    Abou Shelib, M.N.M.; Matinlinna, J.P.; Salameh, Z.; Ounsi, H.

    2008-01-01

    Abstract Objectives Establishing a reliable bond to zirconia-based materials has proven to be difficult which is the major limitation against fabricating adhesive zirconia restorations. This bond could be improved using novel selective infiltration etching conditioning in combination with engineered

  6. Bonding to zirconia using a new surface treatment

    NARCIS (Netherlands)

    Aboushelib, M.N.; Feilzer, A.J.; Kleverlaan, C.J.

    2010-01-01

    Purpose: Selective infiltration etching (SIE) is a newly developed surface treatment used to modify the surface of zirconia-based materials, rendering them ready for bonding to resin cements. The aim of this study was to evaluate the zirconia/resin bond strength and durability using the proposed tec

  7. Bonding to zirconia using a new surface treatment

    NARCIS (Netherlands)

    Aboushelib, M.N.; Feilzer, A.J.; Kleverlaan, C.J.

    2010-01-01

    Purpose: Selective infiltration etching (SIE) is a newly developed surface treatment used to modify the surface of zirconia-based materials, rendering them ready for bonding to resin cements. The aim of this study was to evaluate the zirconia/resin bond strength and durability using the proposed

  8. Light activated phase transformation of metastable tetragonal nanocrystalline zirconia

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; van Lelieveld, A

    2012-01-01

    This study searches for small molecules, which can be generated by photoacid generators (PAGs) capable of inducing the tetragonal-to-monoclinic transformation in zirconia nanocrystals. Metastable tetragonal zirconia nanocrystals were exposed in alcohol suspension. X-ray diffraction analysis showe...

  9. Preliminary Synthesis and Characterization of Mesoporous Nanocrystalline Zirconia

    Institute of Scientific and Technical Information of China (English)

    Xinmei Liu; Gaoqing Lu; Zifeng Yan

    2003-01-01

    A novel method to prepare mesoporous nano-zirconia was developed. The synthesis was carried out in the presence of PEO surfactants via a solid-state reaction. The materials exhibit a strong diffraction peak at low 2θ angle and their nitrogen adsorption/desorption isotherms are typical of type Ⅳ with H1 hysteresis loops. The pore structure imaged by TEM can be described as wormhole domains.The tetragonal zirconia nanocrystals are uniform in size (around 1.5 nm) and their mesopores focus on around 4.6 nm. The zirconia nanocrystal growth is tentatively postulated to be the result of an aggregation mechanism. This study also reveals that the PEO surfactants can interact with the Zr-O-Zr framework to reinforce the thermal stability of zirconia. The ratio of NaOH to ZrOC12, crystallization and calcination temperature play an important role in the synthesis of mesoporous nano-zirconia.

  10. Zirconia supported catalysts for bioethanol steam reforming: Effect of active phase and zirconia structure

    Energy Technology Data Exchange (ETDEWEB)

    Benito, M.; Padilla, R.; Rodriguez, L.; Sanz, J.L.; Daza, L. [Instituto de Catalisis y Petroleoquimica (CSIC), C/ Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain)

    2007-06-10

    Three new catalysts have been prepared in order to study the active phase influence in ethanol steam reforming reaction. Nickel, cobalt and copper were the active phases selected and were supported on zirconia with monoclinic and tetragonal structure, respectively. To characterize the behaviour of the catalysts in reaction conditions a study of catalytic activity with temperature was performed. The highest activity values were obtained at 973 K where nickel and cobalt based catalysts achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. Nickel supported on tetragonal zirconia exhibited the highest hydrogen production efficiency, higher than 4.5 mol H{sub 2}/mol EtOH fed. The influence of steam/carbon (S/C) ratio on product distribution was another parameter studied between the range 3.2-6.5. Nickel supported on tetragonal zirconia at S/C = 3.2 operated at 973 K without by-product production such as ethylene or acetaldehyde. In order to consider a further application in an ethanol processor, a long-term reaction experiment was performed at 973 K, S/C = 3.2 and atmospheric pressure. After 60 h, nickel supported on tetragonal zirconia exhibited high stability and selectivity to hydrogen production. (author)

  11. Clinical assessment of enamel wear caused by monolithic zirconia crowns.

    Science.gov (United States)

    Stober, T; Bermejo, J L; Schwindling, F S; Schmitter, M

    2016-08-01

    The purpose of this study was to measure enamel wear caused by antagonistic monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia full molar crowns were placed in 20 patients. Patients with high activity of the masseter muscle at night (bruxism) were excluded. For analysis of wear, vinylpolysiloxane impressions were prepared after crown incorporation and at 6-, 12-, and 24-month follow-up. Wear of the occlusal contact areas of the crowns, of their natural antagonists, and of two contralateral natural antagonists (control teeth) was measured by use of plaster replicas and a 3D laser-scanning device. Differences of wear between the zirconia crown antagonists and the control teeth were investigated by means of two-sided paired Student's t-tests and linear regression analysis. After 2 years, mean vertical loss was 46 μm for enamel opposed to zirconia, 19-26 μm for contralateral control teeth and 14 μm for zirconia crowns. Maximum vertical loss was 151 μm for enamel opposed to zirconia, 75-115 μm for control teeth and 60 μm for zirconia crowns. Statistical analysis revealed significant differences between wear of enamel by zirconia-opposed teeth and by control teeth. Gender, which significantly affected wear, was identified as a possible confounder. Monolithic zirconia crowns generated more wear of opposed enamel than did natural teeth. Because of the greater wear caused by other dental ceramics, the use of monolithic zirconia crowns may be justified.

  12. Influence of multimode universal adhesives and zirconia primer application techniques on zirconia repair.

    Science.gov (United States)

    Seabra, Bruno; Arantes-Oliveira, Sofia; Portugal, Jaime

    2014-08-01

    More information is needed on the efficacy of the new universal adhesives and on the best 10-methacryloyloxydecyl dihydrogen phosphate- (MDP)-containing primer protocol to promote adhesion to zirconia. The aim of this study was to evaluate the influence of 2 new multimode MDP-containing adhesives and several application protocols of a zirconia primer on the shear bond strength (SBS) of composite resin to zirconia. Sixty zirconia (3Y-TZP) blocks were abraded (50 μm Al2O3) and divided into 6 experimental groups (n=10): one Z-Prime Plus coat without light polymerization; one Z-Prime Plus light-polymerized coat; two Z-Prime Plus coats without light polymerization; two Z-Prime Plus light-polymerized coats; All-Bond Universal; and ScotchBond Universal Adhesive. Multimode adhesives were applied according to the manufacturers' recommendations. After composite resin (Filtek Z250) light polymerization, the specimens were stored in distilled water (37°C/48 hours) and tested in shear (1 mm/min). Failure mode was classified as adhesive or mixed. Statistical analysis of the SBS data was performed with 1-way ANOVA followed by the Student-Newman-Keuls post hoc tests. Nonparametric tests (Kruskal-Wallis) were used to analyze the failure mode data (α=.05). The ScotchBond Universal Adhesive, All-Bond Universal, and two Z-Prime Plus light-polymerized coats groups showed a higher mean SBS than the other experimental groups (Padhesive failures. The new multimode adhesives tested were effective in promoting adhesion between composite resin and zirconia. Z-Prime Plus should be applied in 2 light-polymerized coats to promote SBS values similar to those of the new multimode adhesives. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  13. Microstructural aspects of zirconia thermal barrier coatings

    Science.gov (United States)

    Mitchell, T. E.; Suhr, D. S.; Keller, R. J.; Lanteri, V.; Heuer, A. H.

    1985-01-01

    Various combination of plasma-sprayed bond coatings and zirconia ceramic coatings on a nickel-based superalloy substrate were tested by static thermal exposure at 1200 C and cyclic thermal exposure to 1000 C. The bond coats were based on Ni-Cr-Al alloys with additions of rare earth elements and Si. The ceramic coats were various ZrO2-Y2O3 compositions, of which the optimum was found to be ZrO2-8.9 wt percent Y2O3. Microstructural analysis showed that resistance to cracking during thermal exposure is strongly related to deleterious phase changes. Zones depleted of Al formed at the bond coat/ceramic coat interface due to oxidation and at the bond coat/substrate interface due to interdiffusion, leading eventually to breakdown of the bond coat. The 8.9 percent Y2O3 coating performed best because the as-sprayed metastable tetragonal phase converted slowly into the low-Y2O3 tetragonal plus high-Y2O3 cubic-phase mixture, so that the deleterious monoclinic phase was inhibited from forming. Failure appeared to start with the formation of circumferential cracks in the zirconia, probably due to compressive stresses during cooling, followed by the formation of radial cracks due to tensile stresses during heating. Cracks appeared to initiate at the Al2O3 scale/bond coat interface and propagate through the zirconia coating. Comparisons were made with the behavior of bulk ZrO2-Y2O3 and the relationship between the microstructure of the tetragonal phase and the phase diagram. A separate investigation was also made of the ZrO2-Al2O3 interface.

  14. Microstructure and application of mesoporous nanosize zirconia

    Institute of Scientific and Technical Information of China (English)

    LIU Xinmei; YAN Zifeng; G.Q.Lu

    2004-01-01

    The mesoporous nanoscale zircoina zeolite was firstly synthesized via solid state -- Structure directing method without addition of any stabilizer. The sample bears lamellar or worm pore structures, relatively high surface area compared with that reported. The mesoporous nanosize structure can also resist higher calcination temperature. The introduction of above zirconia to the catalyst of methanol synthesis dedicates the nanosize particle size to the catalyst, which significantly changes the physical structure and electronic effect of the catalyst. The catalyst shows higher catalytic activity and selectivity to methanol. The active sites for methanol synthesis are demonstrated over various catalysts in this paper.

  15. Nanostructured zirconia layers as thermal barrier coatings

    Directory of Open Access Journals (Sweden)

    Radu Robert PITICESCU

    2011-09-01

    Full Text Available The coatings obtained by thermal spray are used both as antioxidant and connection materials (e.g. MCrAlY type alloys as well as thermal barrier coatings (e.g. partially stabilized zirconia oxide with yttria oxide. This paper studies the characteristics of the coatings obtained with nanostructured powders by thermal spraying and air plasma jet metallization. Testing of coatings is done against the most disturbing factor, thermal shock. Structural changes occurring after thermal shock tests are highlighted by investigations of optical and electronic microscopy. The results obtained after quick thermal shock show a good morphological and surface behavior of the developed coatings.

  16. Vibrating wire alignment technique

    CERN Document Server

    Xiao-Long, Wang; lei, Wu; Chun-Hua, Li

    2013-01-01

    Vibrating wire alignment technique is a kind of method which through measuring the spatial distribution of magnetic field to do the alignment and it can achieve very high alignment accuracy. Vibrating wire alignment technique can be applied for magnet fiducialization and accelerator straight section components alignment, it is a necessary supplement for conventional alignment method. This article will systematically expound the international research achievements of vibrating wire alignment technique, including vibrating wire model analysis, system frequency calculation, wire sag calculation and the relation between wire amplitude and magnetic induction intensity. On the basis of model analysis this article will introduce the alignment method which based on magnetic field measurement and the alignment method which based on amplitude and phase measurement. Finally, some basic questions will be discussed and the solutions will be given.

  17. Developing porous ceramics on the base of zirconia oxide with thin and permeable pores by crystallization of organic additive method

    Science.gov (United States)

    Kamyshnaya, K. S.; Khabas, T. A.

    2016-11-01

    In this paper porous ceramics on the base of ZrO2 nanopowders and micropowders has been developed by freeze-casting method. A zirconia/carbamide slurry was frozen in mold and dehydrated in CaCl2 at room temperature. This simple process enabled the formation of porous ceramics with highly aligned pores as a replica of the carbamide crystals. The samples showed higher porosity of 47.9%. In addition, these materials could be used as membrane for air cleaning.

  18. Eco friendly nitration of toluene using modified zirconia

    Directory of Open Access Journals (Sweden)

    K.R. Sunaja Devi

    2013-03-01

    Full Text Available Nitration of toluene has been studied in the liquid phase over a series of modified zirconia catalysts.  Zirconia, zirconia- ceria (Zr0.98Ce0.02O2, sulfated zirconia and sulfated zirconia- ceria were synthesised by co precipitation method and were characterised by X-ray diffraction, BET surface area, Infra red spectroscopy analysis (FTIR, Thermogravimetric analysis (TGA, Scanning Electron Microscopy (SEM and Energy Dispersive X ray analysis (EDAX. The acidity of the prepared catalysts was determined by FTIR pyridine adsorption study. X-ray diffraction studies reveal that the catalysts prepared mainly consist of tetragonal phase with the crystallite size in the nano range and the tetragonal phase of zirconia is stabilized by the addition of ceria. The modified zirconia samples have higher surface area and exhibits uniform pore size distribution aggregated by zirconia nanoparticles. The onset of sulfate decomposition was observed around 723 K for sulfated samples. The catalytic performance was determined for the liquid phase nitration of toluene to ortho-, meta- and para- nitro toluene. The effect of reaction temperature, concentration of nitric acid, catalyst reusability and reaction time was also investigated. © 2013 BCREC UNDIP. All rights reservedReceived: 20th November 2012; Revised: 8th December 2012; Accepted: 7th January 2013[How to Cite: K. R. S. Devi, S. Jayashree, (2013. Eco friendly nitration of toluene using modified zirconia. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (3: 205-214. (doi:10.9767/bcrec.7.3.4154.205-214][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4154.205-214 ] View in  |

  19. Glass ceramic toughened with tetragonal zirconia

    Science.gov (United States)

    Keefer, Keith D.; Michalske, Terry A.

    1986-01-01

    A phase transformation-toughened glass ceramic and a process for making it are disclosed. A mixture of particulate network-forming oxide, network-modifying oxide, and zirconium oxide is heated to yield a homogeneous melt, and this melt is then heat-treated to precipitate an appreciable quantity of tetragonal zirconia, which is retained at ambient temperature to form a phase transformation-toughened glass ceramic. Nucleating agents and stabilizing agents may be added to the mixture to facilitate processing and improve the ceramic's properties. Preferably, the mixture is first melted at a temperature from 1200.degree. to 1700.degree. C. and is then heat-treated at a temperature within the range of 800.degree. to 1200.degree. C. in order to precipitate tetragonal ZrO.sub.2. The composition, as well as the length and temperature of the heat-treatment, must be carefully controlled to prevent solution of the precipitated tetragonal zirconia and subsequent conversion to the monoclinic phase.

  20. Local atomic structure in cubic stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Villella, P.; Conradson, S. D.; Espinosa-Faller, F. J.; Foltyn, S. R.; Sickafus, K. E.; Valdez, J. A.; Degueldre, C. A.

    2001-09-01

    X-ray-absorption fine structure measurements have been used to elucidate the local atomic structure of quaternary Zr, Y, Er, Ce/U cubic stabilized zirconia. These compounds display more complicated local environments than those reported for simpler binary systems. While the shortest cation-O distances are similar to those found in the binary cubic stabilized compounds, responding to the different sizes of the cations, we have identified large distortions in the first-shell oxygen distribution involving long, 2.8--3.2 {angstrom} cation-O distances that are similar to those found in the amorphous phase of zirconium. The cation-cation distributions are also found to be quite complicated (non-Gaussian) and element specific. The U-near neighbor distances are expanded relative to the Ce ions for which it substitutes, consistent with the larger size of the actinide, and the U-cation distribution is also more complicated. In terms of the effects of this substitution on the other cation sites, the local environment around Y is altered while the Zr and Er local environments remain unchanged. These results point out the importance of collective and correlated interactions between the different pairs of cations and the host lattice that are mediated by the local strain fields generated by the different cations. The presence of pair-specific couplings has not been commonly included in previous analyses and may have implications for the stabilization mechanisms of cubic zirconia.

  1. Monoclinic zirconia distributions in plasma-sprayed thermal barrier coatings

    Science.gov (United States)

    Lance, M. J.; Haynes, J. A.; Ferber, M. K.; Cannon, W. R.

    2000-03-01

    Phase composition in an air plasma-sprayed Y2O3-stabilized ZrO2 (YSZ) top coating of a thermal barrier coating (TBC) system was characterized. Both the bulk phase content and localized pockets of monoclinic zirconia were measured with Raman spectroscopy. The starting powder consisted of ˜15 vol.% monoclinic zirconia, which decreased to ˜2 vol.% in the as-sprayed coating. Monoclinic zirconia was concentrated in porous pockets that were evenly distributed throughout the TBC. The pockets resulted from the presence of unmelted granules in the starting powder. The potential effect of the distributed monoclinic pockets on TBC performance is discussed.

  2. Zirconia Rehabilitation Focused on the Emergence Profile: A Case Report.

    Science.gov (United States)

    Mesquita, Alfredo Mikail Melo; Kojima, Alberto Noriyuki; Giovani, Elcio Madaglena; Saraceni, Cintia Helena Coury; Rodrigues, Flávia Pires

    2016-06-01

    The first choice for anterior rehabilitation has been metal-free materials due to their successful aesthetic results. However, the definitive clinical work accuracy may be affected by the lack of clinicians' expertise and familiarization with the latest techniques, as well as recurrent laboratory procedures. This manuscript presents a clinical experience with zirconia ceramic for anterior crowns and zirconia CAD/CAM abutments, including both clinical and laboratory steps after the implant installation. The 'emergence profile' and the 'double scanning' techniques obtained by the waxing technique appear to be a very promising procedure for aesthetic improvement of the single-implant zirconia restoration in anterior teeth.

  3. Preparation and characterization of mesoporous tetragonal sulfated zirconia

    Institute of Scientific and Technical Information of China (English)

    Chun Xia He; Bin Yue; Ji Fang Cheng; Wei Ming Hua; Ying Hong Yue; He Yong He

    2009-01-01

    Mesoporous tetragonal sulfated zirconia with high surface area and narrow pore-size distribution was prepared using Zr(O-nPr)4 as zirconium precursor, sulfuric acid as sulfur source and triblock copolymer poly(ethylene glycol)-poly(propylene glycol)poly(ethylene glycol) (P123) as the template. The samples were characterized by X-ray diffraction, N2 sorption, TEM, and NH3TPD. A phase transformation from monoclinic sulfated zirconia to tetragonal sulfated zirconia is observed. The product shows strong acidity.

  4. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez.

    Since June of 2009, the muon alignment group has focused on providing new alignment constants and on finalizing the hardware alignment reconstruction. Alignment constants for DTs and CSCs were provided for CRAFT09 data reprocessing. For DT chambers, the track-based alignment was repeated using CRAFT09 cosmic ray muons and validated using segment extrapolation and split cosmic tools. One difference with respect to the previous alignment is that only five degrees of freedom were aligned, leaving the rotation around the local x-axis to be better determined by the hardware system. Similarly, DT chambers poorly aligned by tracks (due to limited statistics) were aligned by a combination of photogrammetry and hardware-based alignment. For the CSC chambers, the hardware system provided alignment in global z and rotations about local x. Entire muon endcap rings were further corrected in the transverse plane (global x and y) by the track-based alignment. Single chamber track-based alignment suffers from poor statistic...

  5. On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures.

    Science.gov (United States)

    Chai, Herzl; Lee, James J-W; Mieleszko, Adam J; Chu, Stephen J; Zhang, Yu

    2014-08-01

    Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations.

  6. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez and J. Pivarski

    2011-01-01

    Alignment efforts in the first few months of 2011 have shifted away from providing alignment constants (now a well established procedure) and focussed on some critical remaining issues. The single most important task left was to understand the systematic differences observed between the track-based (TB) and hardware-based (HW) barrel alignments: a systematic difference in r-φ and in z, which grew as a function of z, and which amounted to ~4-5 mm differences going from one end of the barrel to the other. This difference is now understood to be caused by the tracker alignment. The systematic differences disappear when the track-based barrel alignment is performed using the new “twist-free” tracker alignment. This removes the largest remaining source of systematic uncertainty. Since the barrel alignment is based on hardware, it does not suffer from the tracker twist. However, untwisting the tracker causes endcap disks (which are aligned ...

  7. Distortion of CAD-CAM-fabricated implant-fixed titanium and zirconia complete dental prosthesis frameworks.

    Science.gov (United States)

    Al-Meraikhi, Hadi; Yilmaz, Burak; McGlumphy, Edwin; Brantley, William A; Johnston, William M

    2017-05-03

    Computer-aided design and computer-aided manufacturing (CAD-CAM)-fabricated titanium and zirconia implant-supported fixed dental prostheses have become increasingly popular for restoring patients with complete edentulism. However, the distortion level of these frameworks is not well known. The purpose of this in vitro study was to compare the 3-dimensional (3D) distortion of CAD-CAM zirconia and titanium implant-fixed screw-retained complete dental prostheses. A master edentulous model with 4 implants at the positions of the maxillary first molars and canines was used. Multiunit abutments (Nobel Biocare) secured to the model were digitally scanned using scan bodies and a laboratory scanner (S600 ARTI; Zirkonzahn). Titanium (n=5) and zirconia (n=5) frameworks were milled using a CAD-CAM system (Zirkonzahn M1; Zirkonzahn). All frameworks were scanned using an industrial computed tomography (CT) scanner (Nikon/X-Tek XT H 225kV MCT Micro-Focus). The direct CT scans were reconstructed to generate standard tessellation language (STL) files. To calculate the 3D distortion of the frameworks, STL files of the CT scans were aligned to the CAD model using a sum of the least squares best-fit algorithm. Surface comparison points were placed on the CAD model on the midfacial aspect of all teeth. The 3D distortion of each direct scan to the CAD model was calculated. In addition, color maps of the scan-to-CAD comparison were constructed using a ±0.500 mm color scale range. Both materials exhibited distortion; however, no significant difference was found in the amount of distortion from the CAD model between the materials (P=.747). Absolute values of deviations from the CAD model were evident in the x and y plane and less so in the z direction. Zirconia and titanium frameworks showed similar 3D distortion compared with the CAD model for the tested CAD-CAM and implant systems. The distortion was more pronounced in the horizontal and sagittal plane than in the vertical plane

  8. Indentation creep in zirconia ceramics under variable loads

    Energy Technology Data Exchange (ETDEWEB)

    Ren, X.J. [School of Engineering, Liverpool John Moores Univ., Liverpool (United Kingdom); Hooper, R.M. [School of Engineering and Computer Science, Univ. of Exeter, Exeter (United Kingdom); Henshall, J.L. [Mechanical and Mfg. Engineering Dept., Nottingham Trent Univ., Nottingham (United Kingdom)

    2005-07-01

    Time dependent deformation at room and elevated temperature is a significant property of zirconia ceramics and has a direct influence on their use. An understanding of this time dependent behaviour is therefore important in predicting the service life of a component. In this work, the indentation creep behaviour of two typical zirconia ceramics - ceria stabilised polycrystalline tetragonal (Ce-TZP) and yttria (6%) stabilized polycrystalline cubic zirconia, YCPZ, have been investigated from room temperature to 600 C. Indentation creep tests with various loads yielded identical creep rate, which indicates that indentation size effect has no significant effect on the indentation creep of zirconia ceramics. Tests with variable loads, using a spring loaded apparatus, exhibited comparable indentation creep rates to that under constant loading. (orig.)

  9. Orthodontic bracket bonding to glazed full-contour zirconia

    OpenAIRE

    Kwak, Ji-Young; Jung, Hyo-Kyung; Choi, Il-Kyung; Kwon, Tae-Yub

    2016-01-01

    Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometr...

  10. Synthesis of zirconia colloidal dispersions by forced hydrolysis

    Directory of Open Access Journals (Sweden)

    JELENA P. MARKOVIC

    2006-06-01

    Full Text Available Different zirconia colloidal dispersions (sols were prepared from zirconyl oxynitrate and zirconyl oxychloride solutions by forced hydrolysis. Vigorously stirred acidic solutions of these salts were refluxed at 102 oC for 24 h. Characterization of the obtained sols (pH, solid phase content, crystal structure was performed by potentiometric, XRD, TGA/DTA and SEM measurements. The prepared sols contained almost spherical monoclinic hydrated zirconia particles 7–10 nm in diameter.

  11. Fracture resistance of monolithic zirconia molar crowns with reduced thickness

    OpenAIRE

    Nakamura, Keisuke; Harada, A.; Inagaki, R.; Kanno, Taro; Niwano, Y; Milleding, Percy; Ørtengren, Ulf Thore

    2015-01-01

    This is the accepted manuscript version. Published version is available at Acta Odontologica Scandinavica Objectives. The purpose of the present study was to analyze the relationship between fracture load of monolithic zirconia crowns and axial/occlusal thickness, and to evaluate the fracture resistance of monolithic zirconia crowns with reduced thickness in comparison with that of monolithic lithium disilicate crowns with regular thickness. Materials and methods. Monolithic zi...

  12. Zirconia crowns - the new standard for single-visit dentistry?

    Science.gov (United States)

    Wiedhahn, Klaus; Fritzsche, Günter; Wiedhahn, Claudine; Schenk, Olaf

    2016-01-01

    Zirconia crowns combine the advantages of metal restorations, such as minimally invasive tooth preparation and ease of cementation, with those of full ceramic crowns, such as low thermal conductivity and tooth color. With the introduction of a high-speed sintering procedure, it is possible to produce and cement zirconia crowns and small monolithic bridges in a Cerec Single Visit procedure. This new procedure is compared to established chairside methods.

  13. Effect of surface treatments on resin-zirconia bonding

    OpenAIRE

    Yan, Fung; 忻峰

    2015-01-01

    Zirconia offers a favorable choice for esthetic indirect dental restorations with excellent mechanical properties and biocompatibility. In the hostile oral environment, the longevity of dental restorations relies heavily on whether a strong and stable bond between the restoration and underlying supporting tooth structures can be achieved. However, unlike conventional ceramics, zirconia is a chemically inert material which makes it notoriously difficult to bond with any dental composite resin ...

  14. Preparation and properties of dental zirconia ceramics

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Y2O3-stabilized tetragonal zireonia polyerystalline (Y-TZP) ceramics with high-performance were prepared for dental application by use of the micro-emulsion and two-step sintering method.The crystal phase,morphology,and microstructure of the reaction products were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and transmission electron microscopy (TEM).XRD results show that the ceramics mainly consist of tetragonal zirconia.Physical and mechanical properties test results show that the bending strength,fracture toughness,and the density of full sintered Y-TZP ceramics are llS0 MPa,5.53 crown machined with this material by CAD/CAM system exhibits a verisimilitude configuration and the material's expansion coefficient well matches that of the glaze.These results further indicate that the product can be used as a promising new ceramic material

  15. Fracture simulation for zirconia toughened alumina microstructure

    CERN Document Server

    Kim, Kyungmok; Forest, Bernard

    2013-01-01

    Purpose - The purpose of this paper is to describe finite element modelling for fracture and fatigue behaviour of zirconia toughened alumina microstructures. Design/methodology/approach - A two-dimensional finite element model is developed with an actual $Al{_2}O{_3}$ - 10 vol% $ZrO{_2}$ microstructure. A bilinear, time-independent cohesive zone law is implemented for describing fracture behaviour of grain boundaries. Simulation conditions are similar to those found at contact between a head and a cup of hip prosthesis. Residual stresses arisen from the mismatch of thermal coefficient between grains are determined. Then, effects of a micro-void and contact stress magnitude are investigated with models containing residual stresses. For the purpose of simulating fatigue behaviour, cyclic loadings are applied to the models. Findings - Results show that crack density is gradually increased with increasing magnitude of contact stress or number of fatigue cycles. It is also identified that a micro-void brings about...

  16. Phase transformation of zirconia ceramics by hydrothermal degradation.

    Science.gov (United States)

    Kawai, Yohei; Uo, Motohiro; Wang, Yongming; Kono, Sayaka; Ohnuki, Somei; Watari, Fumio

    2011-01-01

    Zirconia has found wide application in dentistry because of its high mechanical strength and superior esthetic properties. However, zirconia degradation caused by phase transformation occurring in a hydrothermal environment is of concern. In the present study, phase transformation and microstructure of tetragonal zirconia polycrystal partially stabilized with yttrium oxide (Y-TZP) and alumina-toughened zirconia (ATZ) sintered at different temperatures were estimated. On grazing angle X-ray diffraction analysis, ATZ showed less phase transformation to the monoclinic phase during hydrothermal treatment and this transformation appeared to occur within a few micrometers below the surface. At a higher sintering temperature the monoclinic phase content of ATZ was found to be lesser than that of Y-TZP, indicating that the alumina in ATZ was effective in suppressing hydrothermal degradation. Examination by transmission electron microscopy and studying of electron backscatter diffraction patterns indicated that grain growth in ATZ was slightly suppressed compared with that in Y-TZP at higher sintering temperatures. The present study demonstrated the effect of adding alumina to zirconia for suppressing hydrothermal degradation and studied the effect of this addition on grain growth in zirconia.

  17. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Sherly, K. B.; Rakesh, K. [Mahatma Gandhi University Regional Research Center in Chemistry, Department of Chemistry, Mar Athanasius College, Kothamangalam-686666, Kerala (India)

    2014-01-28

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl{sub 2}⋅8H{sub 2}O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  18. Orthodontic bracket bonding to glazed full-contour zirconia

    Science.gov (United States)

    Kwak, Ji-Young; Jung, Hyo-Kyung; Choi, Il-Kyung

    2016-01-01

    Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10). Results Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa) and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed. PMID:27200278

  19. Dental zirconia can be etched by hydrofluoric acid.

    Science.gov (United States)

    Sriamporn, Tool; Thamrongananskul, Niyom; Busabok, Chumphol; Poolthong, Sushit; Uo, Motohiro; Tagami, Junji

    2014-01-01

    The surface morphology and crystal structure change of dental zirconia after hydrofluoric acid (HF) etching were evaluated. Four groups of sintered zirconia specimens were 1) control group, 2) immersion in 9.5%HF at 25°C for 1, 2, 3, or 24 h, 3) immersion in 9.5%HF at 80°C for 1, 3, 5, or 30 min and 4) immersion in 48%HF at 25°C for 30 or 60 min. The specimens were evaluated under SEM and XRD. The SEM analysis revealed changes in surface topography for all the HF-etched zirconia specimens. The irregularities surface increased with increasingly longer immersion times and higher etching solution temperatures. The XRD analysis of the HFetched zirconia specimens revealed the presence of a crystalline monoclinic phase along with a tetragonal form. It was concluded HF can etch dental zirconia ceramic, creating micro-morphological changes. Tetragonal-to-monoclinic phase transformation was induced on the etched zirconia surface.

  20. Porous alumina and zirconia ceramics with tailored thermal conductivity

    Science.gov (United States)

    Gregorová, E.; Pabst, W.; Sofer, Z.; Jankovský, O.; Matějíček, J.

    2012-11-01

    The thermal conductivity of porous ceramics can be tailored by slip casting and uniaxial dry pressing, using either fugitive pore formers (saccharides) or partial sintering. Porous alumina and zirconia ceramics have been prepared using appropriate powder types (ungranulated for casting, granulated for pressing) and identical firing regimes (but different maximum temperatures in the case of partial sintering). Thermal diffusivities have been measured by the laser- and xenon-flash method and transformed into relative thermal conductivities, which enable a temperature-independent comparison between different materials. While the porosity can be controlled in a similar way for both materials when using pore formers, partial sintering exhibits characteristic differences between alumina and zirconia (for alumina porosities below 45 %, full density above 1600 °C, for zirconia porosities below 60 %, full density above 1300 °C). The different compaction behavior of alumina and zirconia (porosity after pressing 0.465 and 0.597, respectively) is reflected in the fact that for alumina the relative conductivity data of partially sintered materials are below the exponential prediction, while for zirconia they coincide with the latter. Notwithstanding these characteristic differences, for both alumina and zirconia it is possible to tailor the thermal conductivity from 100 % down to approx. 15 % of the solid phase value.

  1. Condensation of tetragonal zirconia polycrystals by reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-M. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Yeh, S.-W. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Chiou, S.-Y. [Department of Mold and Die Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China); Gan Dershin [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)]. E-mail: dgan@mail.nsysu.edu.tw; Shen Pouyan [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)

    2005-11-22

    Reactive sputtering on metallic Zr target under various oxygen flow rates was employed to produce nanocrystalline zirconia condensates, which were collected on a carbon-coated collodion film for analytical electron microscopic observations. With an Ar flow rate of 28 sccm, the collected condensates are cubic and tetragonal (t-) zirconia less than 10 nm in size under 0-2 sccm oxygen flow rate and increased to 10-20 nm in size with partial t- to monoclinic (m-) zirconia transformation at 3 sccm. Between 4 and 4.5 sccm, t-zirconia polycrystals (TZP) about 20 nm in grain size were formed by coalescence of the t-zirconia condensates. Above 6 sccm, the (111) and {l_brace}100{r_brace} specific coalescence as well as random attachment prevailed to form larger (> 30 nm) individual condensates of m-zirconia as the critical size of martensitic t-m transformation is exceeded. The TZP formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of neighboring grains.

  2. PREPARATION AND CHARACTERIZATION OF SULFATED ZIRCONIA FOR BIODIESEL PRODUCTION

    Directory of Open Access Journals (Sweden)

    Heri Rustamaji

    2012-05-01

    Full Text Available Sulfated zirconia has been prepared and characterized by X-ray diffraction, infrared spectroscopy, BET surface area, and BJH pore distribution methods. XRD patterns reveal that the sulfated zirconia mainly consists of tetragonal crystalline zirconia with average size of about 9.8 nm. N2 adsorption data show that the nanosized sulfated zirconia has high surface area (109.4 m2/g and shows the uniform pore distribution aggregated by zirconia nanoparticles. Sulfated zirconias were used as catalysts in the alcoholysis of jatropha oil. The conversions of jatropha oil alcoholysis under good conditions (120oC, 2 h, 3 wt% of catalyst and 1000 rpm agitation speed were 79.65%.  Abstrak PREPARASI DAN KARAKTERISASI ZIRKONIA TERSULFATASI SEBAGAI KATALISATOR DALAM PEMBUATAN BIODIESEL. Zirkonia tersulfatasi berhasil dibuat dan dikarakterisasi dengan difraksi sinar X, spektroskopi inframerah, pengukuran luas permukaan dengan metode BET dan dan pengukuran distribusi pori dengan metode BJH. Pola difraksi sinar X menunjukkan bahwa susunan utama zirkonia tersulfatasi terdiri atas kristal zirkonia tetragonal dengan ukuran pori rata-rata sekitar 9,8 nm. Data adsorpsi N2 menunjukkan bahwa zirkonia tersulfatasi yang berukuran nano memiliki luas permukaan yang tinggi (109,4 m2/g dan memiliki distribusi ukuran pori yang seragam. Zirkonia tersulfatasi digunakan sebagai katalisator dalam reaksi alkoholisis minyak jarak pagar dengan konversi pada kondisi yang relatif baik (120oC, 2 jam, 3% berat katalis dan kecepatan pengadukan 1000 rpm sebesar 79,65%.

  3. Synthesis and catalytic activity of polysaccharide templated nanocrystalline sulfated zirconia

    Science.gov (United States)

    Sherly, K. B.; Rakesh, K.

    2014-01-01

    Nanoscaled materials are of great interest due to their unique enhanced optical, electrical and magnetic properties. Sulfate-promoted zirconia has been shown to exhibit super acidic behavior and high activity for acid catalyzed reactions. Nanocrystalline zirconia was prepared in the presence of polysaccharide template by interaction between ZrOCl2ṡ8H2O and chitosan template. The interaction was carried out in aqueous phase, followed by the removal of templates by calcination at optimum temperature and sulfation. The structural and textural features were characterized by powder XRD, TG, SEM and TEM. XRD patterns showed the peaks of the diffractogram were in agreement with the theoretical data of zirconia with the catalytically active tetragonal phase and average crystalline size of the particles was found to be 9 nm, which was confirmed by TEM. TPD using ammonia as probe, FTIR and BET surface area analysis were used for analyzing surface features like acidity and porosity. The BET surface area analysis showed the sample had moderately high surface area. FTIR was used to find the type species attached to the surface of zirconia. UV-DRS found the band gap of the zirconia was found to be 2.8 eV. The benzylation of o-xylene was carried out batchwise in atmospheric pressure and 433K temperature using sulfated zirconia as catalyst.

  4. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez

    2010-01-01

    The main developments in muon alignment since March 2010 have been the production, approval and deployment of alignment constants for the ICHEP data reprocessing. In the barrel, a new geometry, combining information from both hardware and track-based alignment systems, has been developed for the first time. The hardware alignment provides an initial DT geometry, which is then anchored as a rigid solid, using the link alignment system, to a reference frame common to the tracker. The “GlobalPositionRecords” for both the Tracker and Muon systems are being used for the first time, and the initial tracker-muon relative positioning, based on the link alignment, yields good results within the photogrammetry uncertainties of the Tracker and alignment ring positions. For the first time, the optical and track-based alignments show good agreement between them; the optical alignment being refined by the track-based alignment. The resulting geometry is the most complete to date, aligning all 250 DTs, ...

  5. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    Z. Szillasi and G. Gomez.

    2013-01-01

    When CMS is opened up, major components of the Link and Barrel Alignment systems will be removed. This operation, besides allowing for maintenance of the detector underneath, is needed for making interventions that will reinforce the alignment measurements and make the operation of the alignment system more reliable. For that purpose and also for their general maintenance and recalibration, the alignment components will be transferred to the Alignment Lab situated in the ISR area. For the track-based alignment, attention is focused on the determination of systematic uncertainties, which have become dominant, since now there is a large statistics of muon tracks. This will allow for an improved Monte Carlo misalignment scenario and updated alignment position errors, crucial for high-momentum muon analysis such as Z′ searches.

  6. Light transmittance of zirconia as a function of thickness and microhardness of resin cements under different thicknesses of zirconia

    OpenAIRE

    Cekic Nagas, Isil; Egilmez,Ferhan; Ergün, Gülfem; Kaya, Bekir-Murat

    2013-01-01

    Objective: The objective of this study was to compare microhardness of resin cements under different thicknesses of zirconia and the light transmittance of zirconia as a function of thickness. Study design: A total of 126 disc-shaped specimens (2 mm in height and 5 mm in diameter) were prepared from dual-cured resin cements (RelyX Unicem, Panavia F and Clearfil SA cement). Photoactivation was performed by using quartz tungsten halogen and light emitting diode light curing units under differen...

  7. Bioactive and thermally compatible glass coating on zirconia dental implants.

    Science.gov (United States)

    Kirsten, A; Hausmann, A; Weber, M; Fischer, J; Fischer, H

    2015-02-01

    The healing time of zirconia implants may be reduced by the use of bioactive glass coatings. Unfortunately, existing glasses are either bioactive like Bioglass 45S5 but thermally incompatible with the zirconia substrate, or they are thermally compatible but exhibit only a very low level of bioactivity. In this study, we hypothesized that a tailored substitution of alkaline earth metals and alkaline metals in 45S5 can lead to a glass composition that is both bioactive and thermally compatible with zirconia implants. A novel glass composition was analyzed using x-ray fluorescence spectroscopy, dilatometry, differential scanning calorimetry, and heating microscopy to investigate its chemical, physical, and thermal properties. Bioactivity was tested in vitro using simulated body fluid (SBF). Smooth and microstructured glass coatings were applied using a tailored spray technique with subsequent thermal treatment. Coating adhesion was tested on implants that were inserted in bovine ribs. The cytocompatibility of the coating was analyzed using L929 mouse fibroblasts. The coefficient of thermal expansion of the novel glass was shown to be slightly lower (11.58 · 10(-6) K(-1)) than that of the zirconia (11.67 · 10(-6) K(-1)). After storage in SBF, the glass showed reaction layers almost identical to the bioactive glass gold standard, 45S5. A process window between 800 °C and 910 °C was found to result in densely sintered and amorphous coatings. Microstructured glass coatings on zirconia implants survived a minimum insertion torque of 60 Ncm in the in vitro experiment on bovine ribs. Proliferation and cytotoxicity of the glass coatings was comparable with the controls. The novel glass composition showed a strong adhesion to the zirconia substrate and a significant bioactive behavior in the SBF in vitro experiments. Therefore, it holds great potential to significantly reduce the healing time of zirconia dental implants.

  8. Orthodontic bracket bonding to glazed full-contour zirconia

    Directory of Open Access Journals (Sweden)

    Ji-Young Kwak

    2016-05-01

    Full Text Available Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau disc surfaces were pre-treated: PO (control, polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z or a silane primer (Monobond-S, S was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S. Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10. Results Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p < 0.05. For AA-Z, most of the adhesive remained on the bracket. Conclusions For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

  9. Ontology alignment with OLA

    OpenAIRE

    Euzenat, Jérôme; Loup, David; Touzani, Mohamed; Valtchev, Petko

    2004-01-01

    euzenat2004d; International audience; Using ontologies is the standard way to achieve interoperability of heterogeneous systems within the Semantic web. However, as the ontologies underlying two systems are not necessarily compatible, they may in turn need to be aligned. Similarity-based approaches to alignment seems to be both powerful and flexible enough to match the expressive power of languages like OWL. We present an alignment tool that follows the similarity-based paradigm, called OLA. ...

  10. Application of Monolithic Zirconia Ceramics in Dental Practice: A Case History Report.

    Science.gov (United States)

    Kim, Hee-Kyung; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk; Yeo, In-Sung

    2016-01-01

    Monolithic zirconia restorations increasingly have been used in dental practice in recent years and demonstrate superior mechanical performance compared with porcelain-veneered zirconia restorations. Recent advances in manufacturing technology have made possible the fabrication of translucent monolithic zirconia ceramics. This case report describes three clinical examples of monolithic zirconia fixed dental prostheses being used in the anterior and posterior regions and exhibiting acceptable esthetic results.

  11. Y-TZP ceramic processing from coprecipitated powders : A comparative study with three commercial dental ceramics

    NARCIS (Netherlands)

    Lazar, Dolores R. R.; Bottino, Marco C.; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H. A.

    2008-01-01

    Objectives. (1) To synthesize 3 mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. Methods.

  12. Y-TZP ceramic processing from coprecipitated powders : A comparative study with three commercial dental ceramics

    NARCIS (Netherlands)

    Lazar, Dolores R. R.; Bottino, Marco C.; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H. A.

    2008-01-01

    Objectives. (1) To synthesize 3 mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. Methods.

  13. Tidal alignment of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  14. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez

    2010-01-01

    Most of the work in muon alignment since December 2009 has focused on the geometry reconstruction from the optical systems and improvements in the internal alignment of the DT chambers. The barrel optical alignment system has progressively evolved from reconstruction of single active planes to super-planes (December 09) to a new, full barrel reconstruction. Initial validation studies comparing this full barrel alignment at 0T with photogrammetry provide promising results. In addition, the method has been applied to CRAFT09 data, and the resulting alignment at 3.8T yields residuals from tracks (extrapolated from the tracker) which look smooth, suggesting a good internal barrel alignment with a small overall offset with respect to the tracker. This is a significant improvement, which should allow the optical system to provide a start-up alignment for 2010. The end-cap optical alignment has made considerable progress in the analysis of transfer line data. The next set of alignment constants for CSCs will there...

  15. Combined novel bonding method of resin to zirconia ceramic in dentistry: a pilot study

    NARCIS (Netherlands)

    Aboushelib, M.N.; Matinlinna, J.P.

    2011-01-01

    Zirconia is a promising metal-free framework material that can be used to construct all-ceramic resin-bonded restorations in modern minimally invasive dentistry. The lack of a durable bond to zirconia is the major limitation against its widespread use. A technique to promote adhesion to the zirconia

  16. Influence of framework color and layering technique on the final color of zirconia veneered restorations

    NARCIS (Netherlands)

    Aboushelib, M.N.; Dozic, A.; Liem, J.K.

    2010-01-01

    Objective: To investigate the influence of colored zirconia frameworks on the overall color match of zirconia- veneered restorations. Method and Materials: Identical natural and colored zirconia frameworks (Cercon Base, Degudent) were layered using a veneer ceramic (IPS e.max Ceram Dentin, Ivoclar

  17. CAD/CAM Zirconia vs. slip-cast glass-infiltrated Alumina/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial

    Directory of Open Access Journals (Sweden)

    Murat Cavit Çehreli

    2009-02-01

    Full Text Available The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram® Zirconia and Cercon® Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA quality evaluation system was used to evaluate the prosthetic replacements, and plaque and gingival index scores were used to explore the periodontal outcome of the treatments. No clinical sign of marginal discoloration, persistent pain and secondary caries was detected in any of the restorations. All InCeram® Zirconia crowns survived during the 2-year period, although one nonvital tooth experienced root fracture coupled with the fracture of the veneering porcelain of the restoration. One Cercon® Zirconia restoration fractured and was replaced. According to the CDA criteria, marginal integrity was rated excellent for InCeram® Zirconia (73% and Cercon® Zirconia (80% restorations, respectively. Slight color mismatch rate was higher for InCeram® Zirconia restorations (66% than Cercon® Zirconia (26% restorations. Plaque and gingival index scores were mostly zero and almost constant over time. Time-dependent changes in plaque and gingival index scores within and between groups were statistically similar (p>0.05. This clinical study demonstrates that single-tooth InCeram® Zirconia and Cercon® Zirconia crowns have comparable early clinical outcome, both seem as acceptable treatment modalities, and most importantly, all-ceramic alumina crowns strengthened by 25% zirconia can sufficiently withstand functional load in the posterior zone.

  18. MECHANICAL BEHAVIOUR OF ALUMINA-ZIRCONIA COMPOSITE BY SLURRY METHOD

    Directory of Open Access Journals (Sweden)

    JYOTI PRAKASH

    2011-02-01

    Full Text Available Alumina has got some excellent properties like chemical inertness, thermal and mechanical strength against hazardous environment. Alumina is a good ceramic material which is being used for structuralapplications. To enhance the toughness and strength of the body some Zirconia is also used with it. The use of Zirconia in alumina is known as toughening of alumina. One difficulty arises, when alumina and alumina toughened composite are sintered , because the low sinterability of Alumina-Zirconia forced the compact to give very low density body. To overcome this problem alumina and alumina composites are made from slurry method which gives nearly theoretical density. The combined effect of alumina and Zirconia on the phase transformation and microstructure development of heat-treated Alumina-Zirconia composites has been studied. Slurry is prepared by adding water, dispersant, binder and anti-foaming agent. In the present study, Sintering schedule is optimized and kept constant for all samples. After sintering, mechanical behaviour of the composite has been studied.

  19. Shear bond strength of indirect composite material to monolithic zirconia

    Science.gov (United States)

    2016-01-01

    PURPOSE This study aimed to evaluate the effect of surface treatments on bond strength of indirect composite material (Tescera Indirect Composite System) to monolithic zirconia (inCoris TZI). MATERIALS AND METHODS Partially stabilized monolithic zirconia blocks were cut into with 2.0 mm thickness. Sintered zirconia specimens were divided into different surface treatment groups: no treatment (control), sandblasting, glaze layer & hydrofluoric acid application, and sandblasting + glaze layer & hydrofluoric acid application. The indirect composite material was applied to the surface of the monolithic zirconia specimens. Shear bond strength value of each specimen was evaluated after thermocycling. The fractured surface of each specimen was examined with a stereomicroscope and a scanning electron microscope to assess the failure types. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey LSD tests (α=.05). RESULTS Bond strength was significantly lower in untreated specimens than in sandblasted specimens (P<.05). No difference between the glaze layer and hydrofluoric acid application treated groups were observed. However, bond strength for these groups were significantly higher as compared with the other two groups (P<.05). CONCLUSION Combined use of glaze layer & hydrofluoric acid application and silanization are reliable for strong and durable bonding between indirect composite material and monolithic zirconia. PMID:27555895

  20. Corrosion behavior of zirconia in acidulated phosphate fluoride

    Directory of Open Access Journals (Sweden)

    Anie Thomas

    2016-02-01

    Full Text Available ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM. Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study.

  1. Mechanical behavior of mullite-zirconia composites

    Directory of Open Access Journals (Sweden)

    Sahnoune F.

    2010-06-01

    Full Text Available In this work, mechanical properties of mullite–zirconia composites synthesised through reaction sintering of Algerian kaolin, α-Al2O3, and ZrO2 were characterized. Phases present and their transformations were characterized using x-ray diffraction. Hardness H and fracture toughness KIC were measured by Vickers indentation using a Zwick microhardness tester. The flexural strength was measured through three point bending test using an Instron Universal Testing Machine. It was found that the increase of ZrO2 content (from 0 to 32wt.% decreased the microhardness of the composites from 14 to 10.8 GPa. However, the increase of ZrO2 content (from 0 to 24wt.% increased the flexural strength of the composites from 142 to 390 MPa then decreased it with further increase of ZrO2 content. Also, the fracture toughness increased from 1.8 to 2.9 MPa.m1/2 with the increase of ZrO2 content from 0 to 32 wt.%; and the rate of the increase decreased at higher fractions of ZrO2 content. The average linear coefficient of thermal expansion (within the range 50 to 1450°C for samples containing 0 and 16 wt.% ZrO2 sintered at 1600°C for 2 hours was 4.7 x10-6 K-1 and 5.2 x 10-6 K-1 respectively.

  2. Mechanical behavior of mullite-zirconia composites

    Science.gov (United States)

    Sahnoune, F.; Saheb, N.

    2010-06-01

    In this work, mechanical properties of mullite-zirconia composites synthesised through reaction sintering of Algerian kaolin, α-Al2O3, and ZrO2 were characterized. Phases present and their transformations were characterized using x-ray diffraction. Hardness H and fracture toughness KIC were measured by Vickers indentation using a Zwick microhardness tester. The flexural strength was measured through three point bending test using an Instron Universal Testing Machine. It was found that the increase of ZrO2 content (from 0 to 32wt.%) decreased the microhardness of the composites from 14 to 10.8 GPa. However, the increase of ZrO2 content (from 0 to 24wt.%) increased the flexural strength of the composites from 142 to 390 MPa then decreased it with further increase of ZrO2 content. Also, the fracture toughness increased from 1.8 to 2.9 MPa.m1/2 with the increase of ZrO2 content from 0 to 32 wt.%; and the rate of the increase decreased at higher fractions of ZrO2 content. The average linear coefficient of thermal expansion (within the range 50 to 1450°C) for samples containing 0 and 16 wt.% ZrO2 sintered at 1600°C for 2 hours was 4.7 x10-6 K-1 and 5.2 x 10-6 K-1 respectively.

  3. Formation of zirconia polymorphs under hydrothermal conditions

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Yanqing(郑燕青); SHl; Erwei(施尔畏); Li; Wenjun(李汶军); CHEN; Zhizhan(陈之战); ZHONG; Weizhuo(仲维卓); HUXingfang(胡行方)

    2002-01-01

    Using zirconium oxychloride solution as precursor, monoclinic zirconia crystallites withnarrow distribution of nanosize were obtained in the hydrothermal reaction. However, when thereaction was in weak acidic medium or base medium, whether directly using the colloidal precipi-tate prepared from zirconium salt solutions with base solution as precursor added, or using theprecipitate after filtrating, washing and drying treatments as precursor, the product of the hydro-thermal reaction was the mixture of both monoclinic and tetragonal polymorphs. As the pH of themedium rises, the content of tetragonal phase in the product, the morphologies and size of thecrystallites all change. There are three types of formation mechanisms under hydrothermal condi-tion, which can be called as saturation-precipitation mechanism in homogeneous solution, dissolu-tion-crystallization mechanism and in-situ crystallization mechanism, respectively. The formationmechanism of crystallites varies with different hydrothermal conditions, such as the states of theprecursor and the pH of the medium, which lead to changes in the phases, morphologies andsizes of the resulting crystallites.

  4. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez

    Since December, the muon alignment community has focused on analyzing the data recorded so far in order to produce new DT and CSC Alignment Records for the second reprocessing of CRAFT data. Two independent algorithms were developed which align the DT chambers using global tracks, thus providing, for the first time, a relative alignment of the barrel with respect to the tracker. These results are an important ingredient for the second CRAFT reprocessing and allow, for example, a more detailed study of any possible mis-modelling of the magnetic field in the muon spectrometer. Both algorithms are constructed in such a way that the resulting alignment constants are not affected, to first order, by any such mis-modelling. The CSC chambers have not yet been included in this global track-based alignment due to a lack of statistics, since only a few cosmics go through the tracker and the CSCs. A strategy exists to align the CSCs using the barrel as a reference until collision tracks become available. Aligning the ...

  5. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    Gervasio Gomez

    The main progress of the muon alignment group since March has been in the refinement of both the track-based alignment for the DTs and the hardware-based alignment for the CSCs. For DT track-based alignment, there has been significant improvement in the internal alignment of the superlayers inside the DTs. In particular, the distance between superlayers is now corrected, eliminating the residual dependence on track impact angles, and good agreement is found between survey and track-based corrections. The new internal geometry has been approved to be included in the forthcoming reprocessing of CRAFT samples. The alignment of DTs with respect to the tracker using global tracks has also improved significantly, since the algorithms use the latest B-field mapping, better run selection criteria, optimized momentum cuts, and an alignment is now obtained for all six degrees of freedom (three spatial coordinates and three rotations) of the aligned DTs. This work is ongoing and at a stage where we are trying to unders...

  6. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez

    2011-01-01

    The Muon Alignment work now focuses on producing a new track-based alignment with higher track statistics, making systematic studies between the results of the hardware and track-based alignment methods and aligning the barrel using standalone muon tracks. Currently, the muon track reconstruction software uses a hardware-based alignment in the barrel (DT) and a track-based alignment in the endcaps (CSC). An important task is to assess the muon momentum resolution that can be achieved using the current muon alignment, especially for highly energetic muons. For this purpose, cosmic ray muons are used, since the rate of high-energy muons from collisions is very low and the event statistics are still limited. Cosmics have the advantage of higher statistics in the pT region above 100 GeV/c, but they have the disadvantage of having a mostly vertical topology, resulting in a very few global endcap muons. Only the barrel alignment has therefore been tested so far. Cosmic muons traversing CMS from top to bottom are s...

  7. Zirconia: Established facts and perspectives for a biomaterial in dental implantology.

    Science.gov (United States)

    Hisbergues, Michael; Vendeville, Sophie; Vendeville, Philippe

    2009-02-01

    Currently, zirconia is widely used in biomedical area as a material for prosthetic devices because of its good mechanical and chemical properties. Largely employed in clinical area for total hip replacement, zirconia ceramics (ZrO(2)) are becoming a prevalent biomaterial in dentistry and dental implantology. Although titanium is used in dental implantology currently, there is a trend to develop new ceramic-based implants as an alternative to monolithic titanium. This article reviews the evolution and development of zirconia through data published between 1963 and January 2008 in English language. Articles were identified via a MEDLINE search using the following keywords: zirconia, zirconia/biocompatibility, zirconia/osseointegration, zirconia/periointegration, zirconia/review, and zirconia/bacterial adhesion or colonization. This review of the literature aims at highlighting and discussing zirconia properties in biological systems for their future use in dental implantology. In conclusion, zirconia with its interesting microstructural properties has been confirmed to be a material of choice for the "new generation" of implants, thanks to its biocompatibility, osseoconductivity, tendency to reduce plaque accumulation, and interaction with soft tissues, which leads to periointegration. However, scientific studies are promptly needed to fulfill gaps like long-term clinical evaluations of "all zirconia implants," currently leading to propose an alternative use of "hybrid systems" (i.e., titanium screw with zirconia collar) and also bacterial colonization of zirconia. Moreover, there is a permanent need for consistent information about topography and chemistry of zirconia allowing easier cross-product comparisons of clinical devices. Copyright 2008 Wiley Periodicals, Inc.

  8. Physics of Grain Alignment

    CERN Document Server

    Lazarian, A

    2000-01-01

    Aligned grains provide one of the easiest ways to study magnetic fields in diffuse gas and molecular clouds. How reliable our conclusions about the inferred magnetic field depends critically on our understanding of the physics of grain alignment. Although grain alignment is a problem of half a century standing recent progress achieved in the field makes us believe that we are approaching the solution of this mystery. I review basic physical processes involved in grain alignment and show why mechanisms that were favored for decades do not look so promising right now. I also discuss why the radiative torque mechanism ignored for more than 20 years looks right now the most powerful means of grain alignment.

  9. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez

    2011-01-01

    A new set of muon alignment constants was approved in August. The relative position between muon chambers is essentially unchanged, indicating good detector stability. The main changes concern the global positioning of the barrel and of the endcap rings to match the new Tracker geometry. Detailed studies of the differences between track-based and optical alignment of DTs have proven to be a valuable tool for constraining Tracker alignment weak modes, and this information is now being used as part of the alignment procedure. In addition to the “split-cosmic” analysis used to investigate the muon momentum resolution at high momentum, a new procedure based on reconstructing the invariant mass of di-muons from boosted Zs is under development. Both procedures show an improvement in the momentum precision of Global Muons with respect to Tracker-only Muons. Recent developments in track-based alignment include a better treatment of the tails of residual distributions and accounting for correla...

  10. SPEAR3 Construction Alignment

    Energy Technology Data Exchange (ETDEWEB)

    LeCocq, Catherine; Banuelos, Cristobal; Fuss, Brian; Gaudreault, Francis; Gaydosh, Michael; Griffin, Levirt; Imfeld, Hans; McDougal, John; Perry, Michael; Rogers,; /SLAC

    2005-08-17

    An ambitious seven month shutdown of the existing SPEAR2 synchrotron radiation facility was successfully completed in March 2004 when the first synchrotron light was observed in the new SPEAR3 ring, SPEAR3 completely replaced SPEAR2 with new components aligned on a new highly-flat concrete floor. Devices such as magnets and vacuum chambers had to be fiducialized and later aligned on girder rafts that were then placed into the ring over pre-aligned support plates. Key to the success of aligning this new ring was to ensure that the new beam orbit matched the old SPEAR2 orbit so that existing experimental beamlines would not have to be reoriented. In this presentation a pictorial summary of the Alignment Engineering Group's surveying tasks for the construction of the SPEAR3 ring is provided. Details on the networking and analysis of various surveys throughout the project can be found in the accompanying paper.

  11. Porous alumina, zirconia and alumina/zirconia for bone repair: fabrication, mechanical and in vitro biological response.

    Science.gov (United States)

    Hadjicharalambous, Chrystalleni; Buyakov, Ales; Buyakova, Svetlana; Kulkov, Sergey; Chatzinikolaidou, Maria

    2015-04-23

    Zirconia (ZrO2) and alumina (Al2O3) based ceramics are widely used for load-bearing applications in bone repair due to their excellent mechanical properties and biocompatibility. They are often regarded as bioinert since no direct bone-material interface is created unless a porous structure intercedes, leading to better bone bonding. In this regard, investigating interactions between cells and porous ceramics is of great interest. In the present study, we report on the successful fabrication of sintered alumina A-61, zirconia Z-50 and zirconia/alumina composite ZA-60 ceramics with medium porosities of 61, 50 and 60%, respectively, indicating a bimodal pore size distribution and good interconnectivity. They exhibit elastic moduli of 3-10 GPa and compressive strength values of 60-240 MPa, similar to those of human cortical bone.We performed in vitro cell-material investigations comparing the adhesion, proliferation and differentiation of mouse pre-osteoblasts MC3T3-E1 on the three porous materials. While all three ceramics demonstrate a strong cell attachment, better cell spreading is observed on zirconia-containing substrates. Significantly higher cell growth was quantified on the latter ceramics, revealing an increased alkaline phosphatase activity, higher collagen production and increased calcium biomineralization compared to A-61. Hence, these porous zirconia-containing ceramics elicit superior biological responses over porous alumina of similar porosity, promoting enhanced biological interaction, with potential use as non-degradable bone grafts or as implant coatings.

  12. Quantum Mechanical Calculations Of Elastic Properties Of Doped Tetragonal Yttria-Stabilized Zirconium Dioxide

    Directory of Open Access Journals (Sweden)

    Yuriy Natanzon

    2008-01-01

    Full Text Available We report first principles calculations of the electronic and elastic properties of yttriastabilized tetragonal zirconium dioxide doped with metal oxides like: GeO2, TiO2, SiO2,MgO and Al2O3. It is shown that addition of such dopants affects selected elastic propertiesof ZrO2, which is driven by the attraction of electron density by dopant atom and creationof stronger dopant–oxygen bonds. This effect contributes to the increase of superplasticityof doped material.

  13. Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

    Science.gov (United States)

    Lineback, L. D.; Manning, C. R.

    1971-01-01

    Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.

  14. Optimization of compressive strength of zirconia based dental composites

    Indian Academy of Sciences (India)

    U V Hambire; V K Tripathi

    2014-10-01

    Dental composites are tooth-coloured restorative material used by dentists for various applications. Restoration of a lost tooth structure requires a material having mechanical as well as aesthetic properties similar to that of tooth. This poses challenges to engineers and the dentist alike. Dental composites consist of a matrix and a dispersed phase called filler, which are mainly responsible for its mechanical properties. Most commonly used matrix is bisphenol glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGMA). Silica and glass are conventional fillers used in the past. Recently, zirconia is being used due to its improved mechanical properties. A study was conducted to evaluate the contribution of zirconia to the mechanical properties in general and compressive strength in particular. We have attempted to make an experimental dental composite with a conglomerate of nanofillers, namely, zirconia, glass and silica, and optimize this filler volume percentage and obtain an optimum compressive strength for the experimental dental composite.

  15. Enhanced initial protein adsorption on an engineered nanostructured cubic zirconia

    CERN Document Server

    Sabirianov, R F; Namavar, F

    2010-01-01

    Motivated by experimentally observed biocompatibility enhancement of nanoengineered cubic zirconia ZrO2 coatings to mesenchymal stromal cells, we have carried out computational analysis of the initial immobilization of one of known structural fragment of the adhesive protein (fibronectin) on the corresponding surface. We constructed an atomistic model of the zirconia nano-hillock of 3-fold symmetry based on AFM and TEM images. First-principle quantum-mechanical calculations show a substantial variation of electrostatic potential at the hillock due to the presence of surface features such as edges and vertexes. Using an implemented Monte Carlo simulated annealing method we found the orientation of the immobilized protein on the zirconia surface (both flat and nanostructured) and contribution of the each amino acid residue from the protein sequence to the adsorption energy. Accounting for the variation of the dielectric permittivity at the protein-implant interface we use a model distance-dependent dielectric f...

  16. High-energy radiation damage in zirconia: modeling results

    Energy Technology Data Exchange (ETDEWEB)

    Zarkadoula, Eva; Devanathan, Ram; Weber, William J.; Seaton, Michael; Todorov, Ilian; Nordlund, Kai; Dove, Martin T.; Trachenko, Kostya

    2014-02-28

    Zirconia has been viewed as a material of exceptional resistance to amorphization by radiation damage, and was consequently proposed as a candidate to immobilize nuclear waste and serve as a nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1-0.5 MeV energies with the account of electronic energy losses. We find that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely disjoint from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  17. High-energy radiation damage in zirconia: modeling results

    Energy Technology Data Exchange (ETDEWEB)

    Zarkadoula, Evangelia [Queen Mary, University of London; Devanathan, Ram [Pacific Northwest National Laboratory (PNNL); Weber, William J [ORNL; Seaton, M [Daresbury Laboratory, UK; Todorov, I T [Daresbury Laboratory, UK; Nordlund, Kai [University of Helsinki; Dove, Martin T [Queen Mary, University of London; Trachenko, Kostya [Queen Mary, University of London

    2014-01-01

    Zirconia is viewed as a material of exceptional resistance to amorphization by radiation damage, and consequently proposed as a candidate to immobilize nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1-0.5 MeV energies with account of electronic energy losses. We nd that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely isolated from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  18. High-energy radiation damage in zirconia: Modeling results

    Energy Technology Data Exchange (ETDEWEB)

    Zarkadoula, E., E-mail: zarkadoulae@ornl.gov [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); SEPnet, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Devanathan, R. [Nuclear Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Weber, W. J. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States); Seaton, M. A.; Todorov, I. T. [STFC Daresbury Laboratory, Scientific Computing Department, Keckwick Lane, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Nordlund, K. [University of Helsinki, P.O. Box 43, FIN-00014 Helsinki (Finland); Dove, M. T. [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Trachenko, K. [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); SEPnet, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2014-02-28

    Zirconia is viewed as a material of exceptional resistance to amorphization by radiation damage, and consequently proposed as a candidate to immobilize nuclear waste and serve as an inert nuclear fuel matrix. Here, we perform molecular dynamics simulations of radiation damage in zirconia in the range of 0.1–0.5 MeV energies with account of electronic energy losses. We find that the lack of amorphizability co-exists with a large number of point defects and their clusters. These, importantly, are largely isolated from each other and therefore represent a dilute damage that does not result in the loss of long-range structural coherence and amorphization. We document the nature of these defects in detail, including their sizes, distribution, and morphology, and discuss practical implications of using zirconia in intense radiation environments.

  19. Study on the neotype zirconia's implant coated nanometer hydroxyapatite ceramics

    Science.gov (United States)

    Zhu, J. W.; Yang, D. W.

    2007-07-01

    In recent years, biologic ceramics is a popular material of implants and bioactive surface modification of dental implant became a research emphasis, which aims to improve bioactivity of implants materials and acquire firmer implants-bone interface. The zirconia ceramic has excellent mechanical properties and nanometer HA ceramics is a bioceramic well known for its bioactivity, therefore, nanometer HA ceramics coating on zirconia, allows combining the excellent mechanical properties of zirconia substrates with its bioactivity. This paper shows a new method for implant shape design and bioactive modification of dental implants surface. Zirconia's implant substrate was prepared by sintered method, central and lateral tunnels were drilled in the zirconia hollow porous cylindrical implants by laser processing. The HA powders and needle-like HA crystals were made by a wet precipitation and calcining method. Its surface was coated with nanometer HA ceramics which was used brush HA slurry and vacuum sintering. Mechanical testing results revealed that the attachment strength of nanometer HA ceramics coated zirconia samples is high. SEM and interface observation after inserted experiment indicated that calcium and phosphor content increased and symmetrically around coated implant-bone tissue interface. A significantly higher affinity index was demonstrated in vivo by histomorphometric evaluation in coated versus uncoated implants. SEM analysis demonstrated better bone adhesion to the material in coated implant at any situation. In addition, the hollow porous cylindrical implant coated with nanometer HA ceramics increase the interaction of bone and implant, the new bone induced into the surface of hollow porous cylindrical implant and through the most tunnels filled into central hole. The branch-like structure makes the implant and bone a body, which increased the contact area and decreased elastic ratio. Therefore, the macroscopical and microcosmic nested structure of

  20. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    Science.gov (United States)

    Becher, Paul F.; Tiegs, Terry N.

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  1. Mechanical behaviour of new zirconia-hydroxyapatite ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Delgado, J.A.; Morejon, L. [La Habana Univ. (Cuba). Centro de Biomateriales; Martinez, S. [Barcelona Univ. (Spain). Dept. Cristallografia, Mineralogia; Ginebra, M.P.; Carlsson, N.; Fernandez, E.; Planell, J.A. [Universidad Politecnica de Cataluna, Barcelona (Spain). CREB; Clavaguera-Mora, M.T.; Rodriguez-Viejo, J. [Universitat Autonoma de Barcelona (Spain). Dept. de Fisica

    2001-07-01

    In this work a new zirconia-hydroxyapatite ceramic material was obtained by uniaxial pressing and sintering in humid environment. The powder X-ray diffraction (XRD) patterns and infrared spectra (FT-IR) showed that the hydroxyapatite (HA) is the only calcium phosphate phase present. The fracture toughness for HA with 20 wt.% of magnesia partially stabilised zirconia (Mg-PSZ) was around 2.5 times higher than those obtained for HA pure, also the highest value of bending strength (160 MPa) was obtained for material reinforced with Mg-PSZ. For the MgPSZ-HA (20%) the fracture mechanism seems to be less transgranular. (orig.)

  2. Electrospun zirconia nanofibers and corresponding formation mechanism study

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Guo-Xun [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Liu, Fu-Tian [School of Material Science and Engineering, University of Jinan, Jinan 250022 (China); Bi, Jian-Qiang, E-mail: bjq1969@163.com [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Engineering Ceramics Key Laboratory of Shandong Province, Shandong University, Jinan 250061 (China); Wang, Chang-An [State Key Laboratory of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China)

    2015-11-15

    Zirconia nanofibers were fabricated by the sol–gel combined with an electrospinning process. The spinnable sol was prepared with zirconium carbonate and acetic acid as raw materials, yttrium nitrate as phase stabilizer, and polyvinyl pyrrolidone as spinning aid. Formation mechanism of spinnable sol was studied. The possible structure of Poly zirconium acetate (PZA) and idealized formation process of PZA were researched in this mechanism. Electrospinning process and heat-treatment process were also researched. Being heat-treated to 1200 °C, the fibers with diameters of 400–600 nm are composed of 20–40 nm tetragonal zirconia grains, which is crack free with smooth surface.

  3. Phase composition of yttrium-doped zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hennig, Christoph; Scheinost, Andreas C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Weiss, Stephan [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements; Gumeniuk, R. [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Experimentelle Physik

    2017-06-01

    Ceramic material might be an alternative to borosilicate glass for the immobilization of nuclear waste. The crystallinity of ceramic material increases the corrosion resistance over several magnitudes in relation to amorphous glasses. The stability of such ceramics depend on several parameters, among them the crystal phase composition. A reliable quantitative phase analysis is necessary to correlate the macroscopic material properties with structure parameters. We performed a feasibility study based on yttrium-doped zirconia ceramics as analogue for trivalent actinides to ascertain that the nanosized crystal phases in zirconia ceramics can be reliably determined.

  4. Interaction between γ-TiAl alloy and zirconia

    Institute of Scientific and Technical Information of China (English)

    Liu Aihu; Li Bangsheng; Nan Hai; Sui Yanwei; Guo Jingjie; Fu Hengzhi

    2008-01-01

    A study on the interaction between TiAI alloy and zirconia was carried out in argon atmosphere. The rnicrographic observations of the cross-section perpendicular to the interface were obtained using a scanning electron microscope with a dedicated energy dispersive spectrometer (SEM/EDS). The results showed that firstly TiAI alloy spreads on the ceramic surface, and then infiltrates into the pores between ceramic particles accompanied by a chemical reaction. The whole ceramic mold is broken into tiny blocks. A multiple fission reaction mechanism was developed to explain the interaction between TiAI alloy and zirconia.

  5. CRACK PROPAGATION BEHAVIOR AND LIFETIME PREDICTION IN ALUMINA AND ZIRCONIA

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The lifetime prediction of ceramics is discussed on the basis of the relationship between stress intensity factor KI and crack velocity v. The effects of water environment, the cyclic loading and microstructure of material on KI-v characteristics are studied by carrying out the crack growth tests by the double torsion (DT) method under the static and cyclic loading in both environments of air and water for alumina and zirconia. KI-v characteristics determined by the double torsion method are used to predict time-to-failure under the cyclic loading of alumina and zirconia ceramics. The predictions agree qualitatively with the experimental results.

  6. Effect of cation dopants in zirconia on interfacial properties in nickel/zirconia systems: an atomistic modeling study

    Science.gov (United States)

    Iskandarov, Albert M.; Ding, Yingna; Umeno, Yoshitaka

    2017-02-01

    Cation doping is often used to stabilize the cubic or tetragonal phase of zirconia for enhanced thermomechanical and electrochemical properties. In the present paper we report a combined density functional theory (DFT) and molecular dynamics study of the effect of Sc, Y, and Ce dopants on properties of Ni/\\text{Zr}{{\\text{O}}2} interfaces and nickel sintering. First, we develop an MD model that is based on DFT data for various nickel/zirconia interfaces. Then, we employ the model to simulate Ni nanoparticles coalescing on a zirconia surface. The results show the possibility of particle migration by means of fast sliding over the surface when the work of separation is small (nanoparticle migration. DFT calculations for the interface revealed that dopants with a smaller covalent radius result in a larger energy barriers for Ni diffusion. We analyze this effect and discuss how it can be used to suppress nickel sintering by using the dopant selection.

  7. Use of spray-dried zirconia microspheres in the separation of immunoglobulins from cell culture supernatant.

    Science.gov (United States)

    Subramanian, A; Carr, P W; McNeff, C V

    2000-08-18

    A method suitable for the isolation of monoclonal antibodies (MAbs) on novel zirconia microspheres (20-30 microm) is described. Zirconia microspheres were generated by spray drying colloidal zirconia. Spray-dried zirconia microspheres were further classified and characterized by X-ray diffraction, BET porosimetry and scanning electron microscopy. Spray-dried zirconia microspheres were modified with ethylenediamine-N,N'-tetra(methylenephosphonic) acid (EDTPA) to create a cation-exchange chromatographic support. The chromatographic behavior of a semi-preparative column packed with EDTPA-modified zirconia microspheres was evaluated and implications for scale-up are provided. EDTPA-modified zirconia microspheres were further used to purify MAbs from cell culture supernatant. Analysis by enzyme linked immunosorbent assay and gel electrophoresis demonstrate that MAbs can be recovered from a cell culture supernatant at high yield (92-98%) and high purity (>95%) in a single chromatographic step.

  8. Sintering and Phase Transformation of 7wt% Calcia-stabilized Zirconia Ceramics

    Institute of Scientific and Technical Information of China (English)

    CHEN Changlian; SHEN Qiang; LI Junguo; ZHANG Lianmeng

    2009-01-01

    Calcia stabilized zirconia(CSZ) ceramics were prepared with 7wt% calcia-stabilized zirconia powder by pressureless sintering technology. The crystal phases of the sintered samples were studied by X-ray diffraction(XRD) and Raman spectroscopy techniques, and the microstructures of the fracture surfaces were observed by scanning electron spectroscopy(SEM). The phase compositions and the lattice parameters of cubic calcia-stabilized zirconia were calculated by XRD patterns. As the sintering temperature increasing from 1400 ℃ to 1600 ℃, the monoclinic zirconia content decreases gradually, finally all monoclinic phase transforms to cubic calcia-stabilized zirconia, which is deter-mined to be Ca0.134Zr0.866O1.866. It is revealed that monoclinic zirconia is the main factor causing minute cracks on the surface of sintered samples, and the combination of the XRD patterns and Raman spectra is an effective way to research the phase transformations of zirconia.

  9. Galaxy alignments: An overview

    CERN Document Server

    Joachimi, Benjamin; Kitching, Thomas D; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Hoekstra, Henk; Kiessling, Alina; Kirk, Donnacha; Rassat, Anais

    2015-01-01

    The alignments between galaxies, their underlying matter structures, and the cosmic web constitute vital ingredients for a comprehensive understanding of gravity, the nature of matter, and structure formation in the Universe. We provide an overview on the state of the art in the study of these alignment processes and their observational signatures, aimed at a non-specialist audience. The development of the field over the past one hundred years is briefly reviewed. We also discuss the impact of galaxy alignments on measurements of weak gravitational lensing, and discuss avenues for making theoretical and observational progress over the coming decade.

  10. Discriminative Shape Alignment

    DEFF Research Database (Denmark)

    Loog, M.; de Bruijne, M.

    2009-01-01

    The alignment of shape data to a common mean before its subsequent processing is an ubiquitous step within the area shape analysis. Current approaches to shape analysis or, as more specifically considered in this work, shape classification perform the alignment in a fully unsupervised way......, not taking into account that eventually the shapes are to be assigned to two or more different classes. This work introduces a discriminative variation to well-known Procrustes alignment and demonstrates its benefit over this classical method in shape classification tasks. The focus is on two......-dimensional shapes from a two-class recognition problem....

  11. Research progress on zirconia and doped zirconia%氧化锆及掺杂氧化锆的研究进展

    Institute of Scientific and Technical Information of China (English)

    刘树信; 王海滨

    2011-01-01

    The properties, preparation methods and research status of zirconia in China and overseas were introduced.The research progress of doped zirconia was summarized.The development direction of zirconia and doped zirconia was analyzed and discussed.%介绍了氧化锆的性质、制备方法及国内外研究现状,概述了掺杂氧化锆的研究进展,并对氧化锆及掺杂氧化锆的发展方向进行了分析和讨论.

  12. CAD/CAM Zirconia vs. slip-cast glass-infiltrated Alumina/Zirconia all-ceramic crowns: 2-year results of a randomized controlled clinical trial

    OpenAIRE

    Murat Cavit Çehreli; Ali Murat Kökat; Kivanç Akça

    2009-01-01

    The aim of this randomized controlled clinical trial was to compare the early clinical outcome of slip-cast glass-infiltrated Alumina/Zirconia and CAD/CAM Zirconia all-ceramic crowns. A total of 30 InCeram® Zirconia and Cercon® Zirconia crowns were fabricated and cemented with a glass ionomer cement in 20 patients. At baseline, 6-month, 1-year, and 2-year recall appointments, Californian Dental Association (CDA) quality evaluation system was used to evaluate the prosthetic replacements, and p...

  13. In situ redox cycle of a nickel-YSZ fuel cell anode in an environmental transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Jeangros, Q. [Interdisciplinary Center for Electron Microscopy, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Faes, A. [Interdisciplinary Center for Electron Microscopy, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)] [Laboratory of Industrial Energy Systems, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Wagner, J.B.; Hansen, T.W. [Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Aschauer, U. [Chemistry Department, Princeton University, Princeton, NJ 08544 (United States); Van herle, J. [Laboratory of Industrial Energy Systems, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Hessler-Wyser, A., E-mail: aicha.hessler@epfl.ch [Interdisciplinary Center for Electron Microscopy, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Dunin-Borkowski, R.E. [Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)

    2010-08-15

    Environmental transmission electron microscopy is used in combination with density functional theory calculations to study the redox stability of a nickel/yttria-stabilized zirconia solid oxide fuel cell anode. The results reveal that the transfer of oxygen from NiO to yttria-stabilized zirconia triggers the reduction reaction. During Ni reoxidation, the creation of a porous structure, due to mass transport, accounts for the redox instability of the Ni-based anode. Both the expansion of NiO during a redox cycle and the presence of stress in the yttria-stabilized zirconia grains are observed directly. Besides providing an understanding of the Ni-YSZ anode redox degradation, the observations are used to propose an alternative anode design for improved redox tolerance.

  14. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez

    Since September, the muon alignment system shifted from a mode of hardware installation and commissioning to operation and data taking. All three optical subsystems (Barrel, Endcap and Link alignment) have recorded data before, during and after CRAFT, at different magnetic fields and during ramps of the magnet. This first data taking experience has several interesting goals: •    study detector deformations and movements under the influence of the huge magnetic forces; •    study the stability of detector structures and of the alignment system over long periods, •    study geometry reproducibility at equal fields (specially at 0T and 3.8T); •    reconstruct B=0T geometry and compare to nominal/survey geometries; •    reconstruct B=3.8T geometry and provide DT and CSC alignment records for CMSSW. However, the main goal is to recons...

  15. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    S. Szillasi

    2013-01-01

    The CMS detector has been gradually opened and whenever a wheel became exposed the first operation was the removal of the MABs, the sensor structures of the Hardware Barrel Alignment System. By the last days of June all 36 MABs have arrived at the Alignment Lab at the ISR where, as part of the Alignment Upgrade Project, they are refurbished with new Survey target holders. Their electronic checkout is on the way and finally they will be recalibrated. During LS1 the alignment system will be upgraded in order to allow more precise reconstruction of the MB4 chambers in Sector 10 and Sector 4. This requires new sensor components, so called MiniMABs (pictured below), that have already been assembled and calibrated. Image 6: Calibrated MiniMABs are ready for installation For the track-based alignment, the systematic uncertainties of the algorithm are under scrutiny: this study will enable the production of an improved Monte Carlo misalignment scenario and to update alignment position errors eventually, crucial...

  16. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez

    2012-01-01

      A new muon alignment has been produced for 2012 A+B data reconstruction. It uses the latest Tracker alignment and single-muon data samples to align both DTs and CSCs. Physics validation has been performed and shows a modest improvement in stand-alone muon momentum resolution in the barrel, where the alignment is essentially unchanged from the previous version. The reference-target track-based algorithm using only collision muons is employed for the first time to align the CSCs, and a substantial improvement in resolution is observed in the endcap and overlap regions for stand-alone muons. This new alignment is undergoing the approval process and is expected to be deployed as part of a new global tag in the beginning of December. The pT dependence of the φ-bias in curvature observed in Monte Carlo was traced to a relative vertical misalignment between the Tracker and barrel muon systems. Moving the barrel as a whole to match the Tracker cures this pT dependence, leaving only the &phi...

  17. Incremental Alignment Manifold Learning

    Institute of Scientific and Technical Information of China (English)

    Zhi Han; De-Yu Meng; Zong-Sen Xu; Nan-Nan Gu

    2011-01-01

    A new manifold learning method, called incremental alignment method (IAM), is proposed for nonlinear dimensionality reduction of high dimensional data with intrinsic low dimensionality. The main idea is to incrementally align low-dimensional coordinates of input data patch-by-patch to iteratively generate the representation of the entire dataset. The method consists of two major steps, the incremental step and the alignment step. The incremental step incrementally searches neighborhood patch to be aligned in the next step, and the alignment step iteratively aligns the low-dimensional coordinates of the neighborhood patch searched to generate the embeddings of the entire dataset. Compared with the existing manifold learning methods, the proposed method dominates in several aspects: high efficiency, easy out-of-sample extension, well metric-preserving, and averting of the local minima issue. All these properties are supported by a series of experiments performed on the synthetic and real-life datasets. In addition, the computational complexity of the proposed method is analyzed, and its efficiency is theoretically argued and experimentally demonstrated.

  18. Comparative analysis of the structure and morphology of a zirconia synthesized by combustion reaction with commercial zirconia; Analise comparativa da estrutura e morfologia de uma zirconia sintetizada por reacao de combustao com uma zirconia comercial

    Energy Technology Data Exchange (ETDEWEB)

    Silva, F.N.; Dantas, J.; Cunha, R.B.L.; Costa, A.C.F.M., E-mail: fnilson.s@hotmail.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais; Pallone, E.M.J.A. [Universidade de Sao Paulo (USP), Pirassununga, SP (Brazil). Departamento de Ciencias Basicas

    2013-07-01

    This work aims to obtain zirconia (ZrO{sub 2}) by combustion reaction, and to make a comparative analysis regarding the structure and morphology of a commercial monoclinic zirconia. The synthetic ZrO{sub 2} was obtained by combustion reaction in batch of 15 g of product, used as precursor the n-propoxide of zirconium IV and urea. The commercial ZrO{sub 2} was supplied by Saint-Gobain Zirpro. The samples were characterized by DRX, SEM and particle size distribution. The results showed for the synthesized ZrO{sub 2} a major phase formation of monoclinic zirconia with trace of the orthorhombic zirconia phase, with crystallite size 16 nm and crystallinity 57%. In the commercial sample was identified only the single monoclinic phase with crystallite size 39 nm and crystallinity of 86%. Both samples have shown homogeneous morphology, constituted of very fine particles of approximately hexagonal shape, with average particle size of 47 to 72 nm, for the synthesized and commercial ZrO{sub 2}, respectively. Comparing among samples, it was found that synthesis by combustion reaction was effective to get monoclinic ZrO{sub 2} nanoparticles with traces of orthorhombic phase with morphology of the finer particles than commercial monoclinic ZrO{sub 2}. (author)

  19. Surface roughness and morphologic changes of zirconia: Effect of ...

    African Journals Online (AJOL)

    surfaces for Cercon (45.15 Ra) and Aadva Zr (51.67 Ra) ceramics. .... cement to dentin and to surface‑treated posts of titanium alloy, glass fiber, and zirconia. J Adhes ... Subasi MG, Inan O. Evaluation of the topographical surface changes and.

  20. TOF-SIMS studies of yttria-stabilised zirconia

    DEFF Research Database (Denmark)

    Hansen, Karin Vels; Norrman, Kion; Mogensen, Mogens Bjerg

    2006-01-01

    The surface of an as-polished and an as-sintered yttria-stabilised zirconia pellet was analysed with XPS and TOF-SIMS (depth profiling and imaging) in order to study the distribution of impurities. The polished sample was slightly contaminated with Na, K, Mg and Ca. The sintered sample showed...

  1. Evaluation of resin adhesion to zirconia ceramic using some organosilanes

    NARCIS (Netherlands)

    Matinlinna, Jukka P.; Heikkinen, Mo; Ozcan, Mutlu; Lassila, Lippo V. J.; Vallittu, Pekka K.

    2006-01-01

    Objectives. This study evaluated and compared the effect of three trialkoxysilane coupling agents on the bond strength of a Bis-GMA-based unfilled resin and a dimethacrylate-based resin composite luting cement to a zirconia ceramics (Procera(R) AllZircon, Nobel Biocare, Goteborg, Sweden). Methods. S

  2. Mechanical properties of ultra-fine grained zirconia ceramics

    NARCIS (Netherlands)

    Theunissen, G.S.A.M.; Bouma, J.S.; Winnubst, A.J.A.; Burggraaf, A.J.

    1992-01-01

    The mechanical properties of tetragonal zirconia (TZP) materials doped with Y, Ce or Ti were studied as a function of temperature and grain size. Fine grained Y-TZP (grain size < 0.3 mgrm) shows values for fracture toughness and strength at room temperature, which are comparable with the coarse grai

  3. Clinical Evaluation and Parental Satisfaction with Pediatric Zirconia Anterior Crowns.

    Science.gov (United States)

    Holsinger, Daniel M; Wells, Martha H; Scarbecz, Mark; Donaldson, Martin

    2016-01-01

    The purpose of this study was to evaluate the clinical success of and parental satisfaction with anterior pediatric zirconia crowns. A retrospective analysis of maxillary anterior pediatric zirconia crowns was performed. Crowns were evaluated for retention, gingival health, color match, contour, marginal integrity, and opposing tooth wear. Parental satisfaction regarding the esthetics of the crowns and parental perception of the impact of treatment on the child's appearance and oral health were evaluated by questionnaire. Fifty-seven crowns were evaluated in 18 children. Eight teeth were lost to exfoliation, three were extracted due to pathology, and two crowns debonded, leaving 44 available for examination. The average crown age at time of examination was 20.8 months. Sixteen crowns (36 percent) displayed gingival inflammation and color mismatch. No recurrent caries or opposing tooth wear was noted. Parents reported high satisfaction with the color, size, and shape of the crowns. The majority of parents reported that crowns improved the appearance and oral health of their child (78 percent and 83 percent, respectively). Eight-nine percent of parents reported that they would highly recommend these crowns. Zirconia crowns are clinically acceptable restorations in the primary maxillary anterior dentition. Parental satisfaction with zirconia crowns is high.

  4. Curriculum Alignment Research Suggests that Alignment Can Improve Student Achievement

    Science.gov (United States)

    Squires, David

    2012-01-01

    Curriculum alignment research has developed showing the relationship among three alignment categories: the taught curriculum, the tested curriculum and the written curriculum. Each pair (for example, the taught and the written curriculum) shows a positive impact for aligning those results. Following this, alignment results from the Third…

  5. Curriculum Alignment Research Suggests that Alignment Can Improve Student Achievement

    Science.gov (United States)

    Squires, David

    2012-01-01

    Curriculum alignment research has developed showing the relationship among three alignment categories: the taught curriculum, the tested curriculum and the written curriculum. Each pair (for example, the taught and the written curriculum) shows a positive impact for aligning those results. Following this, alignment results from the Third…

  6. Measurements of scattering anisotropy in dental tissue and zirconia ceramic

    Science.gov (United States)

    Fernández-Oliveras, Alicia; Pecho, Oscar E.; Rubiño, Manuel; Pérez, María M.

    2012-06-01

    Knowledge of the optical properties of biological structures is useful for clinical applications, especially when dealing with incoming biomaterials engineered to improve the benefits for the patient. One ceramic material currently used in restorative dentistry is yttrium cation-doped tetragonal zirconia polycrystal (3Y-TZP) because of its good mechanical properties. However, its optical properties have not been thoroughly studied. Many methods for the determination of optical parameters from biological media make the assumption that scattered light is isotropically distributed over all angles. Nevertheless, real biological materials may have an angular dependence on light scattering, which may affect the optical behaviour of the materials. Therefore, the recovery of the degree of anisotropy in the scattering angular distribution is important. The phase function that represents the scattering angular distribution is usually characterized by the anisotropy coefficient g, which equals the average cosine of the scattering angle. In this work, we measured angularscattering distributions for two zirconia ceramic samples, pre-sintered and sintered, with similar thicknesses (0.48 mm and 0.50 mm, respectively) and also for a human dentine sample (0.41 mm in thickness). The samples were irradiated with a He-Ne laser beam (λ = 632.8 nm) and the angular-scattering distributions were measured using a rotating goniometer. The g values yielded were: -0.7970 +/- 0.0016 for pre-sintered zirconia, -0.2074 +/- 0.0024 for sintered zirconia and 0.0620 +/- 0.0010 for dentine. The results show that zirconia sintering results in optical behaviour more similar to those of dentine tissue, in terms of scattering anisotropy.

  7. Surface roughness of zirconia for full-contour crowns after clinically simulated grinding and polishing

    Institute of Scientific and Technical Information of China (English)

    Rim Hmaidouch; Wolf-Dieter Mu ller; Hans-Christoph Lauer; Paul Weigl

    2014-01-01

    The aim of this study was to evaluate the effect of controlled intraoral grinding and polishing on the roughness of full-contour zirconia compared to classical veneered zirconia. Thirty bar-shaped zirconia specimens were fabricated and divided into two groups (n515). Fifteen specimens (group 1) were glazed and 15 specimens (group 2) were veneered with feldspathic ceramic and then glazed. Prior to grinding, maximum roughness depth (Rmax) values were measured using a profilometer, 5 times per specimen. Simulated clinical grinding and polishing were performed on the specimens under water coolant for 15 s and 2 N pressure. For grinding, NTI diamonds burs with grain sizes of 20 mm, 10 mm, and 7.5 mm were used sequentially. The ground surfaces were polished using NTI kits with coarse, medium and fine polishers. After each step, Rmax values were determined. Differences between groups were examined using one-way analysis of variance (ANOVA). The roughness of group 1 was significantly lower than that of group 2. The roughness increased significantly after coarse grinding in both groups. The results after glazing were similar to those obtained after fine grinding for non-veneered zirconia. However, fine-ground veneered zirconia had significantly higher roughness than venerred, glazed zirconia. No significant difference was found between fine-polished and glazed zirconia, but after the fine polishing of veneered zirconia, the roughness was significantly higher than after glazing. It can be concluded that for full-contour zirconia, fewer defects and lower roughness values resulted after grinding and polishing compared to veneered zirconia. After polishing zirconia, lower roughness values were achieved compared to glazing;more interesting was that the grinding of glazed zirconia using the NTI three-step system could deliver smooth surfaces comparable to untreated glazed zirconia surfaces.

  8. Surface roughness of zirconia for full-contour crowns after clinically simulated grinding and polishing.

    Science.gov (United States)

    Hmaidouch, Rim; Müller, Wolf-Dieter; Lauer, Hans-Christoph; Weigl, Paul

    2014-12-01

    The aim of this study was to evaluate the effect of controlled intraoral grinding and polishing on the roughness of full-contour zirconia compared to classical veneered zirconia. Thirty bar-shaped zirconia specimens were fabricated and divided into two groups (n=15). Fifteen specimens (group 1) were glazed and 15 specimens (group 2) were veneered with feldspathic ceramic and then glazed. Prior to grinding, maximum roughness depth (Rmax) values were measured using a profilometer, 5 times per specimen. Simulated clinical grinding and polishing were performed on the specimens under water coolant for 15 s and 2 N pressure. For grinding, NTI diamonds burs with grain sizes of 20 µm, 10 µm, and 7.5 µm were used sequentially. The ground surfaces were polished using NTI kits with coarse, medium and fine polishers. After each step, Rmax values were determined. Differences between groups were examined using one-way analysis of variance (ANOVA). The roughness of group 1 was significantly lower than that of group 2. The roughness increased significantly after coarse grinding in both groups. The results after glazing were similar to those obtained after fine grinding for non-veneered zirconia. However, fine-ground veneered zirconia had significantly higher roughness than venerred, glazed zirconia. No significant difference was found between fine-polished and glazed zirconia, but after the fine polishing of veneered zirconia, the roughness was significantly higher than after glazing. It can be concluded that for full-contour zirconia, fewer defects and lower roughness values resulted after grinding and polishing compared to veneered zirconia. After polishing zirconia, lower roughness values were achieved compared to glazing; more interesting was that the grinding of glazed zirconia using the NTI three-step system could deliver smooth surfaces comparable to untreated glazed zirconia surfaces.

  9. MaxAlign: maximizing usable data in an alignment

    DEFF Research Database (Denmark)

    Oliveira, Rodrigo Gouveia; Sackett, Peter Wad; Pedersen, Anders Gorm

    2007-01-01

    BACKGROUND: The presence of gaps in an alignment of nucleotide or protein sequences is often an inconvenience for bioinformatical studies. In phylogenetic and other analyses, for instance, gapped columns are often discarded entirely from the alignment. RESULTS: MaxAlign is a program that optimizes...... the alignment prior to such analyses. Specifically, it maximizes the number of nucleotide (or amino acid) symbols that are present in gap-free columns - the alignment area - by selecting the optimal subset of sequences to exclude from the alignment. MaxAlign can be used prior to phylogenetic and bioinformatical...... analyses as well as in other situations where this form of alignment improvement is useful. In this work we test MaxAlign's performance in these tasks and compare the accuracy of phylogenetic estimates including and excluding gapped columns from the analysis, with and without processing with MaxAlign...

  10. EFFECTIVE ELASTIC PROPERTIES OF ALUMINA-ZIRCONIA COMPOSITE CERAMICS - PART 4. TENSILE MODULUS OF POROUS ALUMINA AND ZIRCONIA

    Directory of Open Access Journals (Sweden)

    W. Pabst

    2004-12-01

    Full Text Available In this fourth paper of a series on the effective elastic properties of alumina-zirconia composite ceramics the influence of porosity on the effective tensile modulus of alumina and zirconia ceramics is discussed. The examples investigated are alumina and zirconia ceramics prepared from submicron powders by starch consolidation casting using two different types of starch, potato starch (median size D50 =47.2 µm and corn starch (median size D50 =13.7 µm. The dependence of effective tensile moduli E, on the porosity f, measured for porosities in the ranges of approx. 19-55 vol.% and 10-42 vol.% for alumina and zirconia, respectively, using a resonant frequency technique, was evaluated by fitting with various model relations, including newly developed ones. A detailed comparison of the fitting results suggests the superiority of the new relation E/E0 = (1 - f·(1 - f/fC, developed by the authors (with the tensile modulus of the dense ceramic material E0 and the critical porosity fC, over most other existing fit models. Only for special purposes and well-behaved data sets the recently proposed exponential relation E/E0 = exp [-Bf/(1 - f] and the well-known Phani-Niyogi relation E/E0 = (1 - f/fCN might be preferable.

  11. Superconducting Electronic Film Structures

    Science.gov (United States)

    1991-02-14

    cubic, yttria stabilized, zirconia (YSZ) single crystals with (100) orientation and ao = 0.512 to 0.516 nm. Films were magnetron-sputtered... Crown by Solid-State and Vapor-Phase Epitaxy," IEEE Trans. Uagn. 25(2), 2538 (1989). 6. J. H. Kang, R. T. Kampwirth, and K. E. Gray, "Superconductivity...summarized in Fig. 1, are too high for SrTiO3 or yttria- stabilized zirconia (YSZ) to be used in rf applications. MgO, LaAIO 3 , and LaGaO3 have a tan 6

  12. Sulfur Poisoning of SOFC Anodes: Effect of Overpotential on Long-Term Degradation

    DEFF Research Database (Denmark)

    Hauch, Anne; Hagen, Anke; Hjelm, Johan

    2014-01-01

    Sulfur impurities in carbon containing fuels for solid oxide fuel cells (SOFC), e.g. natural gas and biogas, typically lead to significant losses in performance due to the sulfur sensitivity of Ni/yttria-stabilized-zirconia (YSZ) anodes for SOFC. Full cells having Ni/YSZ anodes have been characte......Sulfur impurities in carbon containing fuels for solid oxide fuel cells (SOFC), e.g. natural gas and biogas, typically lead to significant losses in performance due to the sulfur sensitivity of Ni/yttria-stabilized-zirconia (YSZ) anodes for SOFC. Full cells having Ni/YSZ anodes have been...

  13. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    Gervasio Gomez

    2012-01-01

      The new alignment for the DT chambers has been successfully used in physics analysis starting with the 52X Global Tag. The remaining main areas of development over the next few months will be preparing a new track-based CSC alignment and producing realistic APEs (alignment position errors) and MC misalignment scenarios to match the latest muon alignment constants. Work on these items has been delayed from the intended timeline, mostly due to a large involvement of the muon alignment man-power in physics analyses over the first half of this year. As CMS keeps probing higher and higher energies, special attention must be paid to the reconstruction of very-high-energy muons. Recent muon POG reports from mid-June show a φ-dependence in curvature bias in Monte Carlo samples. This bias is observed already at the tracker level, where it is constant with muon pT, while it grows with pT as muon chamber information is added to the tracks. Similar studies show a much smaller effect in data, at le...

  14. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez

    2010-01-01

    For the last three months, the Muon Alignment group has focussed on providing a new, improved set of alignment constants for the end-of-year data reprocessing. These constants were delivered on time and approved by the CMS physics validation team on November 17. The new alignment incorporates several improvements over the previous one from March for nearly all sub-systems. Motivated by the loss of information from a hardware failure in May (an entire MAB was lost), the optical barrel alignment has moved from a modular, super-plane reconstruction, to a full, single loop calculation of the entire geometry for all DTs in stations 1, 2 and 3. This makes better use of the system redundancy, mitigating the effect of the information loss. Station 4 is factorised and added afterwards to make the system smaller (and therefore faster to run), and also because the MAB calibration at the MB4 zone is less precise. This new alignment procedure was tested at 0 T against photogrammetry resulting in precisions of the order...

  15. MUON DETECTORS: ALIGNMENT

    CERN Document Server

    M. Dallavalle

    2013-01-01

    A new Muon misalignment scenario for 2011 (7 TeV) Monte Carlo re-processing was re-leased. The scenario is based on running of standard track-based reference-target algorithm (exactly as in data) using single-muon simulated sample (with the transverse-momentum spectrum matching data). It used statistics similar to what was used for alignment with 2011 data, starting from an initially misaligned Muon geometry from uncertainties of hardware measurements and using the latest Tracker misalignment geometry. Validation of the scenario (with muons from Z decay and high-pT simulated muons) shows that it describes data well. The study of systematic uncertainties (dominant by now due to huge amount of data collected by CMS and used for muon alignment) is finalised. Realistic alignment position errors are being obtained from the estimated uncertainties and are expected to improve the muon reconstruction performance. Concerning the Hardware Alignment System, the upgrade of the Barrel Alignment is in progress. By now, d...

  16. Ergodic Secret Alignment

    CERN Document Server

    Bassily, Raef

    2010-01-01

    In this paper, we introduce two new achievable schemes for the fading multiple access wiretap channel (MAC-WT). In the model that we consider, we assume that perfect knowledge of the state of all channels is available at all the nodes in a causal fashion. Our schemes use this knowledge together with the time varying nature of the channel model to align the interference from different users at the eavesdropper perfectly in a one-dimensional space while creating a higher dimensionality space for the interfering signals at the legitimate receiver hence allowing for better chance of recovery. While we achieve this alignment through signal scaling at the transmitters in our first scheme (scaling based alignment (SBA)), we let nature provide this alignment through the ergodicity of the channel coefficients in the second scheme (ergodic secret alignment (ESA)). For each scheme, we obtain the resulting achievable secrecy rate region. We show that the secrecy rates achieved by both schemes scale with SNR as 1/2log(SNR...

  17. Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning.

    Science.gov (United States)

    Cadafalch Gazquez, Gerard; Smulders, Vera; Veldhuis, Sjoerd A; Wieringa, Paul; Moroni, Lorenzo; Boukamp, Bernard A; Ten Elshof, Johan E

    2017-01-13

    The fabrication process of ceramic yttria-stabilized zirconia (YSZ) and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the physicochemical properties of the spinning solutions, and the thermal treatment procedure on spinnability and final microstructure of the ceramic fibers was determined. The fiber diameter can be varied from hundreds of nanometers to more than a micrometer by controlling the solution properties of the electrospinning process, while the grain size and surface roughness of the resulting fibers are mainly controlled via the final thermal annealing process. Although most observed phenomena are in qualitative agreement with previous studies on the electrospinning of polymeric nanofibers, one of the main differences is the high ionic strength of ceramic precursor solutions, which may hamper the spinnability. A strategy to control the effective ionic strength of precursor solutions is also presented.

  18. High critical current densities of YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} thin films on buffered technical substrates

    Energy Technology Data Exchange (ETDEWEB)

    Knierim, A.; Auer, R.; Geerk, J.; Linker, G.; Meyer, O.; Reiner, H.; Schneider, R. [Forschungszentrum Karlsruhe, INFP and ITP, D 76021 Karlsruhe (Germany)

    1997-02-01

    C-axis oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO) thin films were deposited on polycrystalline metallic tapes buffered with yttria stabilized zirconia (YSZ). The in-plane alignment of the YSZ layers achieved by simultaneous ion bombardment of the growing film (ion beam assisted deposition) and of the postdeposited YBCO thin films was studied by x-ray diffraction as a function of the buffer layer thickness. A significant improvement of the in-plane texture, achieved for buffer layers exceeding a thickness of about 1.5 {mu}m, resulted in high critical current densities above 10{sup 6} A/cm{sup 2} of the YBCO films. {copyright} {ital 1997 American Institute of Physics.}

  19. Solid Lubrication by Multiwalled Carbon Nanotubes in Air and in Vacuum for Space and Aeronautics Applications

    Science.gov (United States)

    Miyoshi, Kazuhisa; Street, Kenneth W., Jr.; Andraws, Rodney; Jacques, David; VanderWal, Randy L.; Sayir, Ali

    2005-01-01

    To evaluate recently developed aligned multiwalled carbon nanotubes (MWNTs) and dispersed MWNTs for solid lubrication applications, unidirectional sliding friction experiments were conducted with 440 C stainless steel balls and hemispherical alumina-yttria stabilized zirconia pins in sliding contact with the MWNTs deposited on quartz disks in air and in vacuum. The results indicate that MWNTs have superior solid lubrication friction properties and endurance lives in air and vacuum under dry conditions. The coefficient of friction of the dispersed MWNTs is close to 0.05 and 0.009 in air and in vacuum, respectively, showing good dry lubricating ability. The wear life of MWNTs exceeds 1 million passes in both air and vacuum showing good durability. In general, the low coefficient of friction can be attributed to the combination of the transferred, agglomerated patches of MWNTs on the counterpart ball or pin surfaces and the presence of tubular MWNTs at interfaces.

  20. Influence of Solution Properties and Process Parameters on the Formation and Morphology of YSZ and NiO Ceramic Nanofibers by Electrospinning

    Directory of Open Access Journals (Sweden)

    Gerard Cadafalch Gazquez

    2017-01-01

    Full Text Available The fabrication process of ceramic yttria-stabilized zirconia (YSZ and nickel oxide nanofibers by electrospinning is reported. The preparation of hollow YSZ nanofibers and aligned nanofiber arrays is also demonstrated. The influence of the process parameters of the electrospinning process, the physicochemical properties of the spinning solutions, and the thermal treatment procedure on spinnability and final microstructure of the ceramic fibers was determined. The fiber diameter can be varied from hundreds of nanometers to more than a micrometer by controlling the solution properties of the electrospinning process, while the grain size and surface roughness of the resulting fibers are mainly controlled via the final thermal annealing process. Although most observed phenomena are in qualitative agreement with previous studies on the electrospinning of polymeric nanofibers, one of the main differences is the high ionic strength of ceramic precursor solutions, which may hamper the spinnability. A strategy to control the effective ionic strength of precursor solutions is also presented.

  1. FMIT alignment cart

    Energy Technology Data Exchange (ETDEWEB)

    Potter, R.C.; Dauelsberg, L.B.; Clark, D.C.; Grieggs, R.J.

    1981-01-01

    The Fusion Materials Irradiation Test (FMIT) Facility alignment cart must perform several functions. It must serve as a fixture to receive the drift-tube girder assembly when it is removed from the linac tank. It must transport the girder assembly from the linac vault to the area where alignment or disassembly is to take place. It must serve as a disassembly fixture to hold the girder while individual drift tubes are removed for repair. It must align the drift tube bores in a straight line parallel to the girder, using an optical system. These functions must be performed without violating any clearances found within the building. The bore tubes of the drift tubes will be irradiated, and shielding will be included in the system for easier maintenance.

  2. Strategic Alignment of Business Intelligence

    OpenAIRE

    Cederberg, Niclas

    2010-01-01

    This thesis is about the concept of strategic alignment of business intelligence. It is based on a theoretical foundation that is used to define and explain business intelligence, data warehousing and strategic alignment. By combining a number of different methods for strategic alignment a framework for alignment of business intelligence is suggested. This framework addresses all different aspects of business intelligence identified as relevant for strategic alignment of business intelligence...

  3. PILOT optical alignment

    Science.gov (United States)

    Longval, Y.; Mot, B.; Ade, P.; André, Y.; Aumont, J.; Baustista, L.; Bernard, J.-Ph.; Bray, N.; de Bernardis, P.; Boulade, O.; Bousquet, F.; Bouzit, M.; Buttice, V.; Caillat, A.; Charra, M.; Chaigneau, M.; Crane, B.; Crussaire, J.-P.; Douchin, F.; Doumayrou, E.; Dubois, J.-P.; Engel, C.; Etcheto, P.; Gélot, P.; Griffin, M.; Foenard, G.; Grabarnik, S.; Hargrave, P..; Hughes, A.; Laureijs, R.; Lepennec, Y.; Leriche, B.; Maestre, S.; Maffei, B.; Martignac, J.; Marty, C.; Marty, W.; Masi, S.; Mirc, F.; Misawa, R.; Montel, J.; Montier, L.; Narbonne, J.; Nicot, J.-M.; Pajot, F.; Parot, G.; Pérot, E.; Pimentao, J.; Pisano, G.; Ponthieu, N.; Ristorcelli, I.; Rodriguez, L.; Roudil, G.; Salatino, M.; Savini, G.; Simonella, O.; Saccoccio, M.; Tapie, P.; Tauber, J.; Torre, J.-P.; Tucker, C.

    2016-07-01

    PILOT is a balloon-borne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy at wavelengths 240 μm with an angular resolution about two arcminutes. Pilot optics is composed an off-axis Gregorian type telescope and a refractive re-imager system. All optical elements, except the primary mirror, are in a cryostat cooled to 3K. We combined the optical, 3D dimensional measurement methods and thermo-elastic modeling to perform the optical alignment. The talk describes the system analysis, the alignment procedure, and finally the performances obtained during the first flight in September 2015.

  4. Group Based Interference Alignment

    CERN Document Server

    Ma, Yanjun; Chen, Rui; Yao, Junliang

    2010-01-01

    in $K$-user single-input single-output (SISO) frequency selective fading interference channels, it is shown that the achievable multiplexing gain is almost surely $K/2$ by using interference alignment (IA). However when the signaling dimensions is limited, allocating all the resource to all the users simultaneously is not optimal. According to this problem, a group based interference alignment (GIA) scheme is proposed and a search algorithm is designed to get the group patterns and the resource allocation among them. Analysis results show that our proposed scheme achieves a higher multiplexing gain when the resource is limited.

  5. Orientation and Alignment Echoes

    CERN Document Server

    Karras, G; Billard, F; Lavorel, B; Hartmann, J -M; Faucher, O; Gershnabel, E; Prior, Y; Averbukh, I Sh

    2015-01-01

    We present what is probably the simplest classical system featuring the echo phenomenon - a collection of randomly oriented free rotors with dispersed rotational velocities. Following excitation by a pair of time-delayed impulsive kicks, the mean orientation/alignment of the ensemble exhibits multiple echoes and fractional echoes. We elucidate the mechanism of the echo formation by kick-induced filamentation of phase space, and provide the first experimental demonstration of classical alignment echoes in a thermal gas of CO_2 molecules excited by a pair of femtosecond laser pulses.

  6. Shear bond strength of veneering porcelain to zirconia: Effect of surface treatment by CNC-milling and composite layer deposition on zirconia.

    Science.gov (United States)

    Santos, R L P; Silva, F S; Nascimento, R M; Souza, J C M; Motta, F V; Carvalho, O; Henriques, B

    2016-07-01

    The purpose of this study was to evaluate the shear bond strength of veneering feldspathic porcelain to zirconia substrates modified by CNC-milling process or by coating zirconia with a composite interlayer. Four types of zirconia-porcelain interface configurations were tested: RZ - porcelain bonded to rough zirconia substrate (n=16); PZ - porcelain bonded to zirconia substrate with surface holes (n=16); RZI - application of a composite interlayer between the veneering porcelain and the rough zirconia substrate (n=16); PZI - application of a composite interlayer between the porcelain and the zirconia substrate treated by CNC-milling (n=16). The composite interlayer was composed of zirconia particles reinforced porcelain (30%, vol%). The mechanical properties of the ceramic composite have been determined. The shear bond strength test was performed at 0.5mm/min using a universal testing machine. The interfaces of fractured and untested specimens were examined by FEG-SEM/EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The one-way ANOVA followed by Tukey HSD multiple comparison test was used to compare shear bond strength results (α=0.05). The shear bond strength of PZ (100±15MPa) and RZI (96±11MPa) specimens were higher than that recorded for RZ (control group) specimens (89±15MPa), although not significantly (p>0.05). The highest shear bond strength values were recorded for PZI specimens (138±19MPa), yielding a significant improvement of 55% relative to RZ specimens (p<0.05). This study shows that it is possible to highly enhance the zirconia-porcelain bond strength - even by ~55% - by combining surface holes in zirconia frameworks and the application of a proper ceramic composite interlayer. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. In vitro evaluation of fracture strength of zirconia restoration veneered with various ceramic materials

    OpenAIRE

    Choi, Yu-Sung; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk; Yeo, In-Sung

    2012-01-01

    PURPOSE Fracture of the veneering material of zirconia restorations frequently occurs in clinical situations. The purpose of this in vitro study was to compare the fracture strengths of zirconia crowns veneered with various ceramic materials by various techniques. MATERIALS AND METHODS A 1.2 mm, 360° chamfer preparation and occlusal reduction of 2 mm were performed on a first mandibular molar, and 45 model dies were fabricated in a titanium alloy by CAD/CAM system. Forty-five zirconia copings...

  8. Surface properties of monolithic zirconia after dental adjustment treats and in vitro wear simulation

    OpenAIRE

    Preis, Verena; Schmalzbauer, Michael; Bougeard, Dominique; Schneider-Feyrer, Sibylle; Rosentritt, Martin

    2014-01-01

    Objectives To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation. Methods Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n = 10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each tre...

  9. Morphology and Composition of Nanocrystalline Stabilized Zirconia using Sem-Eds System

    OpenAIRE

    Sunday Adesunloye JONAH; Patrick Ovie AKUSU; Tajudeen Oladele AHMED; Rabiu NASIRU

    2011-01-01

    Bismuth oxide of known mole percentages has been incorporated into zirconia matrix via co-precipitation method. The co-precipitated powders containing mixed oxides of bismuth and zirconium are dried and calcined in air at 200°C and 800°C respectively to obtain nanosized-stabilized zirconia. The microstructures and the composition of the nanosized-stabilized zirconia are investigated using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) at a low accel...

  10. Improvement on Corrosion Resistance of Zirconia-Graphite Material for Powder Line of SEN

    Institute of Scientific and Technical Information of China (English)

    LI Hongxia; YANG Bin; YANG Jinsong; LIU Guoqi

    2003-01-01

    The influence of anti-oxidation additions and microstructure characters off used zirconia raw materials on the corrosion resistance of ZrO2-C were studied. The results show that BN addition can enhance the corrosion resistance of ZrO2-C due to the prevention of graphite oxidation,and zirconia raw material with good crystallization and densification will give better corrosion resistance by restrain the reaction between slag and zirconia.

  11. Simulation of beamline alignment operations

    Energy Technology Data Exchange (ETDEWEB)

    Annese, C; Miller, M G

    1999-02-02

    The CORBA-based Simulator was a Laboratory Directed Research and Development (LDRD) project that applied simulation techniques to explore critical questions about distributed control systems. The simulator project used a three-prong approach that studied object-oriented distribution tools, computer network modeling, and simulation of key control system scenarios. The National Ignition Facility's (NIF) optical alignment system was modeled to study control system operations. The alignment of NIF's 192 beamlines is a large complex operation involving more than 100 computer systems and 8000 mechanized devices. The alignment process is defined by a detailed set of procedures; however, many of the steps are deterministic. The alignment steps for a poorly aligned component are similar to that of a nearly aligned component; however, additional operations/iterations are required to complete the process. Thus, the same alignment operations will require variable amounts of time to perform depending on the current alignment condition as well as other factors. Simulation of the alignment process is necessary to understand beamline alignment time requirements and how shared resources such as the Output Sensor and Target Alignment Sensor effect alignment efficiency. The simulation has provided alignment time estimates and other results based on documented alignment procedures and alignment experience gained in the laboratory. Computer communication time, mechanical hardware actuation times, image processing algorithm execution times, etc. have been experimentally determined and incorporated into the model. Previous analysis of alignment operations utilized average implementation times for all alignment operations. Resource sharing becomes rather simple to model when only average values are used. The time required to actually implement the many individual alignment operations will be quite dynamic. The simulation model estimates the time to complete an operation using

  12. Engineering Materials for Very High Temperatures: An ONRL Workshop

    Science.gov (United States)

    1988-08-29

    stabilized partially stabilized zirconia (Mg-PSZ) (Schioler et al, 1984), yttria stabilized tetragonal zirconia polycrystal (Y- TZP ) (Swab, 1987) and SiC...compounds. Currently, boron carbide is being de- the right scientific/technical challenge and which have veloped, boron nitride ( cubic and graphite...with inevitable intergranular residues and high temperature property impairment. Zirconia (Zr0 2 ) based ceramics are an important development of the

  13. ADVANCED CERAMIC MATERIALS FOR DENTAL APPLICATIONS SINTERED BY MICROWAVE HEATING

    OpenAIRE

    Presenda Barrera, Álvaro

    2016-01-01

    [EN] Zirconia has become a widely utilized structural ceramic material with important applications in dentistry due to its superb mechanical properties, biocompatibility, aesthetic characteristics and durability. Zirconia needs to be stabilized in the t-phase to obtain improved mechanical properties such as hardness and fracture toughness. Fully dense yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) materials are normally consolidated through the energy-intensive processing of po...

  14. Aligning Responsible Business Practices

    DEFF Research Database (Denmark)

    Weller, Angeli E.

    2017-01-01

    This article offers an in-depth case study of a global high tech manufacturer that aligned its ethics and compliance, corporate social responsibility, and sustainability practices. Few large companies organize their responsible business practices this way, despite conceptual relevance and calls...... and managers interested in understanding how responsible business practices may be collectively organized....

  15. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez and Y. Pakhotin

    2012-01-01

      A new track-based alignment for the DT chambers is ready for deployment: an offline tag has already been produced which will become part of the 52X Global Tag. This alignment was validated within the muon alignment group both at low and high momentum using a W/Z skim sample. It shows an improved mass resolution for pairs of stand-alone muons, improved curvature resolution at high momentum, and improved DT segment extrapolation residuals. The validation workflow for high-momentum muons used to depend solely on the “split cosmics” method, looking at the curvature difference between muon tracks reconstructed in the upper or lower half of CMS. The validation has now been extended to include energetic muons decaying from heavily boosted Zs: the di-muon invariant mass for global and stand-alone muons is reconstructed, and the invariant mass resolution is compared for different alignments. The main areas of development over the next few months will be preparing a new track-based C...

  16. Aligning Theory with Practice

    Science.gov (United States)

    Kurz, Terri L.; Batarelo, Ivana

    2009-01-01

    This article describes a structure to help preservice teachers get invaluable field experience by aligning theory with practice supported by the integration of elementary school children into their university mathematics methodology course. This course structure allowed preservice teachers to learn about teaching mathematics in a nonthreatening…

  17. Alignment of concerns

    DEFF Research Database (Denmark)

    Andersen, Tariq Osman; Bansler, Jørgen P.; Kensing, Finn;

    2014-01-01

    The emergence of patient-centered eHealth systems introduces new challenges, where patients come to play an increasingly important role. Realizing the promises requires an in-depth understanding of not only the technology, but also the needs of both clinicians and patients. However, insights from...... as a design rationale for successful eHealth, termed 'alignment of concerns'....

  18. Aligning Mental Representations

    DEFF Research Database (Denmark)

    Kano Glückstad, Fumiko

    2013-01-01

    on the application of the BMG to publicly available datasets, the Leuven natural concept database [3] representing semantic structures of domain knowledge possessed by individual subjects [3]. Results indicate that the BMG is potentially a model applicable to simulating the alignment of domain knowledge from...

  19. Characterization of combustion synthesized zirconia powder by UV-vis, IR and other techniques

    Indian Academy of Sciences (India)

    H Ranjan Sahu; G Ranga Rao

    2000-10-01

    Fine powders of zirconia were prepared by employing combustion method with varying fuel to precursor molar ratios. The zirconia powders contained more amount of monoclinic phase as the fuel content was increased. This aspect was studied using XRD, IR and UV-vis diffuse reflectance techniques. The surface acidbase properties of these samples were also investigated by indicator titration method. The catalytic activity was probed with transfer hydrogenation reaction in liquid phase. It was found that combustion synthesized zirconia did not provide required active sites for transfer hydrogenation reactions in liquid phase unlike hydrous zirconia.

  20. Synthesis and Characterization of Yttrium Doped Nano-zirconia by a Cationic Surfactant-assisted Route

    Institute of Scientific and Technical Information of China (English)

    YU Jian-Chang; HU Shen-Wei

    2006-01-01

    Recently, more and more interest has been focused on zirconia for its unique characteristics. In this paper, via the preceding preparation technique, yttrium can be successfully incorporated into nano-zirconia by a cationic surfactant-assisted route. The methods of XRD, TEM, EDS, Uv-vis and N2 adsorption-desorption are adopted to characterize the synthesized samples. The results show that the yttrium has been successfully incorporated into the zirconia lattice, and the thermal stability of yttrium doped zirconia has been enhanced remarkably.

  1. Surface properties of titanium and zirconia dental implant materials and their effect on bacterial adhesion.

    Science.gov (United States)

    Al-Radha, Afya Sahib Diab; Dymock, David; Younes, Charles; O'Sullivan, Dominic

    2012-02-01

    Zirconia ceramic material has been widely used in implant dentistry. In this in vitro study the physiochemical properties of titanium and zirconia materials were investigated and the affinity of different bacteria to different materials was compared. Disc samples with different surface states were used: polished partially stabilized zirconia (PZ), titanium blasted with zirconia (TBZ), titanium blasted with zirconia then acid etched (TBZA), and polished titanium (PT) as a control. Surface topography was examined using scanning electron microscopy and profilometry. Contact angle, surface free energy (SFE), surface microhardness and chemical composition were determined. Disc samples were separately incubated with Streptococcus mitis and Prevotella nigrescens, either with or without pre-coating with human saliva, for 6h and the surface area covered by bacteria was calculated from fluorescence microscope images. PZ and TBZ exhibited lower surface free energy and lesser surface wettability than PT. Also, PZ and TBZ surfaces showed lower percentage of bacterial adhesion compared with control PT surface. The zirconia material and titanium blasted with zirconia surface (TBZ surface) showed superior effect to titanium material in reducing the adhesion of the experimented bacteria especially after coating with saliva pellicle. Modifying titanium with zirconia lead to have the same surface properties of pure zirconia material in reducing bacterial adhesion. SFE appears to be the most important factors that determine initial bacterial adhesion to smooth surface. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. colorimetric evaluation of Cercon zirconia and metal ceramic restorations in two thicknesses of veneering porcelain

    Directory of Open Access Journals (Sweden)

    Dorriz H

    2011-02-01

    Full Text Available "nBackground and Aims: The aim of this study was to evaluate the effect of zirconia and base metal cores on the color of restorations. Furthermore, the effect of different backings on the color of cercon zirconia was evaluated."nMaterials and Methods: The specimens were Cercon zirconia and metal ceramic discs with "high Au" and "base metal" alloys. Cercon zirconia discs were veneered with veneering shade of A2 and two thickness of porcelain"n(0.7 mm, 1.2 mm. There were 3 discs in each group. Metal ceramic discs were made of "nickel-chromium" alloy (Verobond and "high Au" alloy (World 89 and two shades (A2, A3.5 and two thicknesses of veneering porcelain. 3 types of backing (high Au, nickel-chromium and A3 shade composite were made for Cercon zirconia discs. Spectrophotometric evaluation of zirconia discs (on 3 backings and metal ceramic discs was done. One-way ANOVA and Tukey tests were used for data analysis."nResults: There were no significant differences between the amounts of L*, a*, b* for Cercon zirconia on different backings (P>0.05. In comparison between different core groups, a* was significantly higher in metal ceramic groups compared with that of zirconia groups (P<0.05."nConclusion: Cercon zirconia can completely mask the underlying backing.

  3. The radiation response of mesoporous nanocrystalline zirconia thin films

    Science.gov (United States)

    Manzini, Ayelén M.; Alurralde, Martin A.; Giménez, Gustavo; Luca, Vittorio

    2016-12-01

    The next generation of nuclear systems will require materials capable of withstanding hostile chemical, physical and radiation environments over long time-frames. Aside from its chemical and physical stability, crystalline zirconia is one of the most radiation tolerant materials known. Here we report the first ever study of the radiation response of nanocrystalline and mesoporous zirconia and Ce3+-stabilized nanocrystalline zirconia (Ce0.1Zr0.9O2) thin films supported on silicon wafers. Zirconia films prepared using the block copolymer Brij-58 as the template had a thickness of around 60-80 nm. In the absence of a stabilizing trivalent cation they consisted of monoclinic and tetragonal zirconia nanocrystals with diameters in the range 8-10 nm. Films stabilized with Ce3+ contained only the tetragonal phase. The thin films were irradiated with iodine ions of energies of 70 MeV and 132 keV at low fluences (1013 - 1014 cm-2) corresponding to doses of 0.002 and 1.73 dpa respectively, and at 180 keV and high fluences (2 × 1016 cm-2) corresponding to 82.4 dpa. The influence of heavy ion irradiation on the nanocrystalline structure was monitored through Rietveld analysis of grazing incidence X-ray diffraction (GIXRD) patterns recorded at angles close to the critical angle to ensure minimum contribution to the diffraction pattern from the substrate. Irradiation of the mesoporous nanocrystalline zirconia thin films with 70 MeV iodine ions, for which electronic energy loss is dominant, resulted in slight changes in phase composition and virtually no change in crystallographic parameters as determined by Rietveld analysis. Iodine ion bombardment in the nuclear energy loss regime (132-180 keV) at low fluences did not provoke significant changes in phase composition or crystallographic parameters. However, at 180 keV and high fluences the monoclinic phase was totally eliminated from the GIXRD pattern of films prepared at both 350 and 500 °C implying either a monoclinic

  4. Zirconia-based solid state chemical gas sensors

    CERN Document Server

    Zhuiykov, S

    2000-01-01

    This paper presents an overview of chemical gas sensors, based on solid state technology, that are sensitive to environmental gases, such as O sub 2 , SO sub x , NO sub x , CO sub 2 and hydrocarbons. The paper is focussed on performance of electrochemical gas sensors that are based on zirconia as a solid electrolyte. The paper considers sensor structures and selection of electrode materials. Impact of interfaces on sensor performance is discussed. This paper also provides a brief overview of electrochemical properties of zirconia and their effect on sensor performance. Impact of auxiliary materials on sensors performance characteristics, such as sensitivity, selectivity, response time and recovery time, is also discussed. Dual gas sensors that can be applied for simultaneous monitoring of the concentration of both oxygen and other gas phase components, are briefly considered

  5. Zirconia-based fixed partial dentures: a clinical review.

    Science.gov (United States)

    Bachhav, Vinay Chila; Aras, Meena Ajay

    2011-02-01

    Ceramics have a long history in fixed prosthodontics of achieving optimal esthetics. Yttrium tetragonal zirconia polycrystal (Y-TZP)-based systems are a recent addition to the high-strength, all-ceramic systems used for crowns and fixed partial dentures. CAD/CAM-produced, Y-TZP-based systems are in considerable demand in esthetic and stress-bearing regions. The highly esthetic nature of zirconia coupled with its superior physical properties and biocompatibility have resulted in restorative systems that meet the demands of today's patients. Undoubtedly, these systems are considered to be prospective replacements for metal-ceramic restorations. This article reviews relevant contemporary literature regarding all-ceramic materials and systems and discusses their material properties, biocompatibility, advances in cementation, and more with special emphasis on clinical survival. The article also aims to provide recommendations for their use.

  6. Preparation of zirconia-alumina powder by co-precipitation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A zirconia-alumina powder with a near spherical shape and an average size of 0.1 ~ 0.2μm was prepared byco-precipitation. XRD analysis shows that α-Al2O3 phase may be directly transformed from amorphous in calcining the hydroxide composite. The ZrO2-Al2O3 composite ceramics manufactured from this powder has the maximum fracture toughness of 9 M Pa·m- 1/2 at 15 % ZrO2 and 740 MPa fracture strength at 5 % ZrO2. Zirconia grains about 1 μm in diameter aredispersed uniformly in the alumina ceramic matrix

  7. Long Term Fatigue Behavior of Zirconia Based Dental Ceramics

    Directory of Open Access Journals (Sweden)

    Moustafa N. Aboushelib

    2010-04-01

    Full Text Available This study evaluated the influence of cyclic loading on zirconia bar-shaped specimens after being subjected to three different surface treatments: particle abrasion with either 50 μm or 110 μm alumina and grinding with diamond points, while polished specimens served as a control. Statistical analysis revealed significant reduction (38-67% in flexure strength (P < 0.001 after three million cycles of dynamic loading for all surface treatments. Scanning electron imaging revealed grain boundary thickening, grain pull-out, and micro-cracking as the main structural defects. The results suggest that various surface treatments of zirconia based dental ceramics may significantly influence their long term fatigue resistance in the oral environment.

  8. Tetragonal and cubic zirconia multilayered ceramic constructs created by EPD.

    Science.gov (United States)

    Mochales, Carolina; Frank, Stefan; Zehbe, Rolf; Traykova, Tania; Fleckenstein, Christine; Maerten, Anke; Fleck, Claudia; Mueller, Wolf-Dieter

    2013-02-14

    The interest in electrophoretic deposition (EPD) for nanomaterials and ceramics production has widely increased due to the versatility of this technique to effectively combine different materials in unique shapes and structures. We successfully established an EPD layering process with submicrometer sized powders of Y-TZP with different mol percentages of yttrium oxide (3 and 8%) and produced multilayers of alternating tetragonal and cubic phases with a clearly defined interface. The rationale behind the design of these multilayer constructs was to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase. In this work, a preliminary study of the mechanical properties of these constructs proved the good mechanical integrity of the multilayered constructs obtained as well as crack deflection in the interface between tetragonal and cubic zirconia layers.

  9. In-vitro bioactivity of zirconia doped borosilicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Samudrala, Rajkumar; Azeem, P. Abdul, E-mail: rk.satyaswaroop@gmail.com, E-mail: drazeem2002@yahoo.com [Department of Physics, National Institute of Technology, Warangal-506004 (India)

    2015-06-24

    Glass composition 31B{sub 2}O{sub 3}-20SiO{sub 2}-24.5Na{sub 2}O-(24.5-x) CaO-xZrO{sub 2} x=1,2,3,4,5 were prepared by melt-quenching Technique. The formation of hydroxyapatite layer on the surface of glasses after immersion in simulated body fluid (SBF) was explored through XRD, Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM-EDX) analyses. In this report, we observed that hydroxyapatite formation for 5days of immersion time. Also observed that with increasing the immersion time up to 15days, higher amount of hydroxyapatite layer formation on the surface of glasses. The varying composition of zirconia in glass samples influences shown by XRD, FTIR studies. The present results indicate that, in-vitro bioactivity of glasses decreased with increasing zirconia incorporation.

  10. Initial bacterial adhesion on resin, titanium and zirconia in vitro

    OpenAIRE

    Lee, Byung-Chul; Jung, Gil-Yong; Kim, Dae-Joon; Han, Jung-Suk

    2011-01-01

    PURPOSE The aim of this in vitro study was to investigate the adhesion of initial colonizer, Streptococcus sanguis, on resin, titanium and zirconia under the same surface polishing condition. MATERIALS AND METHODS Specimens were prepared from Z-250, cp-Ti and 3Y-TZP and polished with 1 µm diamond paste. After coating with saliva, each specimen was incubated with Streptococcus sanguis. Scanning electron microscope, crystal violet staining and measurement of fluorescence intensity resulting fro...

  11. Preparation of Zirconia Based Packing Material and Its Evaluation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new reversed-phase packing (C18-PBD-ZrO2) was prepared by depositing and cross-linking 1-octadecene (ODE or C18) and polybutadiene (PBD) onto the surface of porous zirconia microspheres (5~10 mm in diameter) which were synthesized by a sol-gel process. These novel column packings possess high mechanical and chemical stability,wider usable pH range and can be used to separate basic compounds with no observable peak tailing.

  12. A new testing protocol for zirconia dental implants.

    Science.gov (United States)

    Sanon, Clarisse; Chevalier, Jérôme; Douillard, Thierry; Cattani-Lorente, Maria; Scherrer, Susanne S; Gremillard, Laurent

    2015-01-01

    Based on the current lack of standards concerning zirconia dental implants, we aim at developing a protocol to validate their functionality and safety prior their clinical use. The protocol is designed to account for the specific brittle nature of ceramics and the specific behavior of zirconia in terms of phase transformation. Several types of zirconia dental implants with different surface textures (porous, alveolar, rough) were assessed. The implants were first characterized in their as-received state by Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB), X-Ray Diffraction (XRD). Fracture tests following a method adapted from ISO 14801 were conducted to evaluate their initial mechanical properties. Accelerated aging was performed on the implants, and XRD monoclinic content measured directly at their surface instead of using polished samples as in ISO 13356. The implants were then characterized again after aging. Implants with an alveolar surface presented large defects. The protocol shows that such defects compromise the long-term mechanical properties. Implants with a porous surface exhibited sufficient strength but a significant sensitivity to aging. Even if associated to micro cracking clearly observed by FIB, aging did not decrease mechanical strength of the implants. As each dental implant company has its own process, all zirconia implants may behave differently, even if the starting powder is the same. Especially, surface modifications have a large influence on strength and aging resistance, which is not taken into account by the current standards. Protocols adapted from this work could be useful. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  13. First Synthesis of Zirconia-pillared Layered Lanthanum Niobate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A zirconia-pillared layered lanthanum niobate was prepared by first preswelling layered HLaNb2O7 with n-hexadecylamine(n-C16H33NH2), then further reacting with zirconyl chloride aqueous solution, and finally calcining the resultant solid product in air. The obtained new material has an interlayer spacing of 1.36nm, and a high thermal stability above 700°C.

  14. Development of solid state thick film zirconia oxygen gas sensors.

    OpenAIRE

    Ioannou, Andreas Stylianou

    1992-01-01

    Aspects relating to and including the development of thick film amperometric zirconia oxygen sensors were investigated. These devices, which were operated in the range 550-950°C, had a laminated structure in which a cathode, an electrolyte and an anode were printed, in that order, onto a planar alumina substrate. The anode and electrolyte were porous and during sensor Operation also acted as a diffusion barrier, restricting the rate of oxygen diffusion to the cathode. A thick film platinum he...

  15. Comparative study of physical properties of zirconia based dental ceramics

    OpenAIRE

    Pittayachawan, P.

    2009-01-01

    The aim of this project was to evaluate and compare the mechanical properties of commercial yttria partially stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics, which have generated interest in restorative dentistry because of their high strength and high resistance to fracture. Mechanical properties of three commercial Y-TZP ceramics (Lava™, Cercon® and Invizion™) were investigated including the biaxial flexural strength, hardness, fatigue, and subcritical crack growth....

  16. CSL grain boundary distribution in alumina and zirconia ceramics

    OpenAIRE

    Vonlanthen, Pierre; Grobéty, Bernard

    2008-01-01

    The distributions of general and coincidence site lattice (CSL) grain boundaries (GBs) in texture-free alumina and zirconia ceramics sintered at two different temperatures were investigated based on electron backscatter diffraction (EBSD) measurements. Results were compared with the distributions obtained from random 2D spatial models and with calculated random distributions reported in the literature. All alumina samples independent on sintering temperature show the same characteristic devia...

  17. Surface stability and small-scale testing of zirconia

    OpenAIRE

    Camposilvan, Erik

    2015-01-01

    Tetragonal polycrystalline zirconia stabilized with 3 mol% of yttria (3Y-TZP) is a biocompatible ceramic showing superior mechanical properties, which are partly the consequence of phase transformation: the tetragonal metastable phase can transform, with a net volume increase, to the stable monoclinic phase by a martensitic transformation. The transformation can be activated either mechanically by the application of high stresses, or chemically by the diffusion of water species, when the mate...

  18. Thermomechanical Properties of Corundum—Mullite—Zirconia Materials

    Institute of Scientific and Technical Information of China (English)

    ZHONGXiangchong; SUNGengcheng

    1998-01-01

    The mechanical properties at elevated tempera-tures of corundum-mullite materials and the effects of zirconia and titania additions have been investi-gated.The results are correlated with changes in microstructure,Based on the results of these investi-gations ,reaction-sintered corundum-mullite-zirco-nia materials with improved hot strength and ther-mal shock resistance have been developed for refractor-ries usage.

  19. ABS: Sequence alignment by scanning

    KAUST Repository

    Bonny, Mohamed Talal

    2011-08-01

    Sequence alignment is an essential tool in almost any computational biology research. It processes large database sequences and considered to be high consumers of computation time. Heuristic algorithms are used to get approximate but fast results. We introduce fast alignment algorithm, called Alignment By Scanning (ABS), to provide an approximate alignment of two DNA sequences. We compare our algorithm with the well-known alignment algorithms, the FASTA (which is heuristic) and the \\'Needleman-Wunsch\\' (which is optimal). The proposed algorithm achieves up to 76% enhancement in alignment score when it is compared with the FASTA Algorithm. The evaluations are conducted using different lengths of DNA sequences. © 2011 IEEE.

  20. Fast global sequence alignment technique

    KAUST Repository

    Bonny, Mohamed Talal

    2011-11-01

    Bioinformatics database is growing exponentially in size. Processing these large amount of data may take hours of time even if super computers are used. One of the most important processing tool in Bioinformatics is sequence alignment. We introduce fast alignment algorithm, called \\'Alignment By Scanning\\' (ABS), to provide an approximate alignment of two DNA sequences. We compare our algorithm with the wellknown sequence alignment algorithms, the \\'GAP\\' (which is heuristic) and the \\'Needleman-Wunsch\\' (which is optimal). The proposed algorithm achieves up to 51% enhancement in alignment score when it is compared with the GAP Algorithm. The evaluations are conducted using different lengths of DNA sequences. © 2011 IEEE.

  1. A facile approach to the synthesis of non-porous and microporous sub-micron spherical zirconia and alumina-zirconia solid solution.

    Science.gov (United States)

    Ghotbi, Mohammad Yeganeh; Nasiri, Vida; Rafiee, Mehdi

    2013-01-01

    Amorphous monodisperse sub-micron spherical zirconia and alumina/zirconia solid solution particles were prepared by hydrolysis of zirconium and aluminum salts in ethanol. The heat-treatment process of the amorphous materials in air atmosphere at 500°C for 2h leaded to the production of non-porous zirconia and alumina/zirconia solid solution in tetragonal phase. The alkaline etching process of the as-prepared alumina/zirconia solid solution resulted in the formation of mono-modal microporous material with specific surface area of 125.0 m(2) g(-1) in comparison with 2. 9m(2) g(-1) for the parent material. Thermal analysis of the solid solution revealed that the incorporation of aluminum ions in the zirconia structure has decreased the phase transformation temperature from amorphous to crystalline structure. Moreover, optical study confirmed the presence of oxygen vacancy defect by substitution of tetravalent cations, Zr(4+) by trivalent cations, Al(3+) in zirconia lattice.

  2. Ionoluminscence of partially-stabilized zirconia for thermal barrier coatings

    Energy Technology Data Exchange (ETDEWEB)

    Rebollo, N.R. [Departamento de Fisica Experimental, Instituto de Fisica, Universidad Nacional Autonoma de Mexico (UNAM), Circuito de la Investigacion Cientifica S/N, Ciudad Universitaria, Mexico D.F., C.P. 04510 (Mexico)]. E-mail: nrebollof@yahoo.com; Ruvalcaba-Sil, J.L. [Departamento de Fisica Experimental, Instituto de Fisica, Universidad Nacional Autonoma de Mexico (UNAM), Circuito de la Investigacion Cientifica S/N, Ciudad Universitaria, Mexico D.F., C.P. 04510 (Mexico); Miranda, J. [Departamento de Fisica Experimental, Instituto de Fisica, Universidad Nacional Autonoma de Mexico (UNAM), Circuito de la Investigacion Cientifica S/N, Ciudad Universitaria, Mexico D.F., C.P. 04510 (Mexico)

    2007-08-15

    Ionoluminescence is explored as an alternative technique to study the high temperature phase stability of zirconia-based oxides. The evolution of an initially metastable single tetragonal phase towards de-stabilization is investigated for three single-doped zirconia compositions with Y, Yb and Gd. The differences in de-stabilization paths are identified using X-ray diffraction and ionoluminescence; elemental analysis is also performed using particle-induced X-ray emission. X-ray diffraction studies reveal a different scenario for each of the compositions selected; the differences are strongly influenced by the thermodynamic driving forces associated to the fluorite-to-tetragonal displacive transformation. Ionoluminescence studies indicate a significant increment on the signal intensity for de-stabilized samples, relative to previous annealing stages. There are also more subtle differences in the luminescent response from the samples at intermediate annealing stages also related to phase changes. This study provides a basis to characterize phase evolution in single-doped zirconia compositions for thermal insulation applications using luminescence.

  3. Characteristics of porous zirconia coated with hydroxyapatite as human bones

    Indian Academy of Sciences (India)

    V V Narulkar; S Prakash; K Chandra

    2007-08-01

    Since hydroxyapatite has excellent biocompatibility and bone bonding ability, porous hydroxyapatite ceramics have been intensively studied. However, porous hydroxyapatite bodies are mechanically weak and brittle, which makes shaping and implantation difficult. One way to solve this problem is to introduce a strong porous network onto which hydroxyapatite coating is applied. In this study, porous zirconia and alumina-added zirconia ceramics were prepared by ceramic slurry infiltration of expanded polystyrene bead compacts, followed by firing at 1500°C. Then slurry of hydroxyapatite–borosilicate glass mixed powder was used to coat the porous ceramics, followed by firing at 1200°C. The porous structures without the coating had high porosities of 51–69%, high pore interconnectivity, and sufficiently large pore window sizes (300–500 m). The porous ceramics had compressive strengths of 5.3∼36.8 MPa, favourably comparable to the mechanical properties of cancellous bones. In addition, porous hydroxyapatite surface was formed on the top of the composite coating, whereas a borosilicate glass layer was found on the interface. Thus, porous zirconia-based ceramics were modified with a bioactive composite coating for biomedical applications.

  4. Comparison of peri-implant bone formation around injection-molded and machined surface zirconia implants in rabbit tibiae.

    Science.gov (United States)

    Kim, Hong-Kyun; Woo, Kyung Mi; Shon, Won-Jun; Ahn, Jin-Soo; Cha, Seunghee; Park, Young-Seok

    2015-01-01

    The aim of this study was to compare osseointegration and surface characteristics of zirconia implants made by the powder injection molding (PIM) technique against those made by the conventional milling procedure in rabbit tibiae. Surface characteristics of 2 types of implants were evaluated. Sixteen rabbits received 2 types of external hex implants with similar geometry, either machined zirconia implants or PIM zirconia implants, in the tibiae. Removal torque tests and histomorphometric analyses were performed. The roughness of the PIM zirconia implants was higher than that of machined zirconia implants. The PIM zirconia implants exhibited significantly higher bone-implant contact and removal torque values than the machined zirconia implants (pmold etching technique, can produce substantially rougher surfaces on zirconia implants.

  5. Formatt: Correcting protein multiple structural alignments by incorporating sequence alignment

    Directory of Open Access Journals (Sweden)

    Daniels Noah M

    2012-10-01

    Full Text Available Abstract Background The quality of multiple protein structure alignments are usually computed and assessed based on geometric functions of the coordinates of the backbone atoms from the protein chains. These purely geometric methods do not utilize directly protein sequence similarity, and in fact, determining the proper way to incorporate sequence similarity measures into the construction and assessment of protein multiple structure alignments has proved surprisingly difficult. Results We present Formatt, a multiple structure alignment based on the Matt purely geometric multiple structure alignment program, that also takes into account sequence similarity when constructing alignments. We show that Formatt outperforms Matt and other popular structure alignment programs on the popular HOMSTRAD benchmark. For the SABMark twilight zone benchmark set that captures more remote homology, Formatt and Matt outperform other programs; depending on choice of embedded sequence aligner, Formatt produces either better sequence and structural alignments with a smaller core size than Matt, or similarly sized alignments with better sequence similarity, for a small cost in average RMSD. Conclusions Considering sequence information as well as purely geometric information seems to improve quality of multiple structure alignments, though defining what constitutes the best alignment when sequence and structural measures would suggest different alignments remains a difficult open question.

  6. Residual compressive surface stress increases the bending strength of dental zirconia.

    Science.gov (United States)

    Inokoshi, Masanao; Zhang, Fei; Vanmeensel, Kim; De Munck, Jan; Minakuchi, Shunsuke; Naert, Ignace; Vleugels, Jozef; Van Meerbeek, Bart

    2017-04-01

    To assess the influence of surface treatment and thermal annealing on the four-point bending strength of two ground dental zirconia grades. Fully-sintered zirconia specimens (4.0×3.0×45.0mm(3)) of Y-TZP zirconia (LAVA Plus, 3M ESPE) and Y-TZP/Al2O3 zirconia (ZirTough, Kuraray Noritake) were subjected to four surface treatments: (1) 'GROUND': all surfaces were ground with a diamond-coated grinding wheel on a grinding machine; (2) 'GROUND+HEAT': (1) followed by annealing at 1100°C for 30min; (3) 'GROUND+Al2O3 SANDBLASTED': (1) followed by sandblasting using Al2O3; (4) 'GROUND+CoJet SANDBLASTED': (1) followed by tribochemical silica (CoJet) sandblasting. Micro-Raman spectroscopy was used to assess the zirconia-phase composition and potentially induced residual stress. The four-point bending strength was measured using a universal material-testing machine. Weibull analysis revealed a substantially higher Weibull modulus and slightly higher characteristic strength for ZirTough (Kuraray Noritake) than for LAVA Plus (3M ESPE). For both zirconia grades, the 'GROUND' zirconia had the lowest Weibull modulus in combination with a high characteristic strength. Sandblasting hardly changed the bending strength but substantially increased the Weibull modulus of the ground zirconia, whereas a thermal treatment increased the Weibull modulus of both zirconia grades but resulted in a significantly lower bending strength. Micro-Raman analysis revealed a higher residual compressive surface stress that correlated with an increased bending strength. Residual compressive surface stress increased the bending strength of dental zirconia. Thermal annealing substantially reduced the bending strength but increased the consistency (reliability) of 'GROUND' zirconia. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. Effect of sol size on nanofiltration performance of a sol-gel derived microporous zirconia membrane

    Institute of Scientific and Technical Information of China (English)

    Guizhi Zhu; Qian Jiang; Hong Qi; Nanping Xu

    2015-01-01

    This paper reports the effect of sol size on nanofiltration performances of sol–gel derived microporous zirconia membranes. Microstructure, pure water flux, molecular weight cut-off (MWCO) and salt retention of zirconia membranes derived from zirconia sols with different sizes were characterized. Thermal evolution, phase compo-sition, microstructure and chemical stability of unsupported zirconia membranes (powder) were determined by thermogravimetric and differential thermal analysis, X-ray diffraction, nitrogen adsorption–desorption and static solubility measurements. Results show that nanofiltration performance of zirconia membranes is highly depen-dent on sol size. The sol with an average size of 3.8 nm, which is smaller than the pore size of theγ-Al2O3 support (pore size:5–6 nm), forms a discontinuous zirconia separation layer because of excessive penetration of sol into the support. This zirconia membrane displays a MWCO value towards polyethylene glycol higher than 4000 Da. A smooth and defect-free zirconia membrane with a MWCO value of 1195 Da (pore size:1.75 nm) and relative high retention rates towards MgCl2 (76%) and CaCl2 (64%) was successfully fabricated by dip-coating the sol with an appropriate size of 8.6 nm. Zirconia sol with an average size of 12 nm exhibits colloidal nature and forms a zirconia membrane with a MWCO value of 2332 Da (pore size:2.47 nm). This promising microporous zirconia membrane presents sufficiently high chemical stability in a wide pH range of 1–12.

  8. Fracture resistance of monolithic zirconia crowns: The importance of the compressive strength of the dental cements used.

    OpenAIRE

    2014-01-01

    Background: Monolithic zirconia crowns have not been used for a very long period in dentistry even though zirconia with veneering porcelain, as crown and bridge material has been used for several years with great clinical success. Several different luting materials have been purposed for zirconia but concerning monolithic zirconia the knowledge of the influence of the cement seem to be limited. The aim of the study was to investigate three different cements (one phosphate, one self adhesive a...

  9. Inflation by alignment

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, C.P. [PH -TH Division, CERN,CH-1211, Genève 23 (Switzerland); Department of Physics & Astronomy, McMaster University,1280 Main Street West, Hamilton ON (Canada); Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo ON (Canada); Roest, Diederik [Van Swinderen Institute for Particle Physics and Gravity, University of Groningen,Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2015-06-08

    Pseudo-Goldstone bosons (pGBs) can provide technically natural inflatons, as has been comparatively well-explored in the simplest axion examples. Although inflationary success requires trans-Planckian decay constants, f≳M{sub p}, several mechanisms have been proposed to obtain this, relying on (mis-)alignments between potential and kinetic energies in multiple-field models. We extend these mechanisms to a broader class of inflationary models, including in particular the exponential potentials that arise for pGB potentials based on noncompact groups (and so which might apply to moduli in an extra-dimensional setting). The resulting potentials provide natural large-field inflationary models and can predict a larger primordial tensor signal than is true for simpler single-field versions of these models. In so doing we provide a unified treatment of several alignment mechanisms, showing how each emerges as a limit of the more general setup.

  10. Aligning component upgrades

    Directory of Open Access Journals (Sweden)

    Roberto Di Cosmo

    2011-08-01

    Full Text Available Modern software systems, like GNU/Linux distributions or Eclipse-based development environment, are often deployed by selecting components out of large component repositories. Maintaining such software systems by performing component upgrades is a complex task, and the users need to have an expressive preferences language at their disposal to specify the kind of upgrades they are interested in. Recent research has shown that it is possible to develop solvers that handle preferences expressed as a combination of a few basic criteria used in the MISC competition, ranging from the number of new components to the freshness of the final configuration. In this work we introduce a set of new criteria that allow the users to specify their preferences for solutions with components aligned to the same upstream sources, provide an efficient encoding and report on the experimental results that prove that optimising these alignment criteria is a tractable problem in practice.

  11. Inflation by Alignment

    CERN Document Server

    Burgess, Cliff

    2015-01-01

    Pseudo-Goldstone bosons (pGBs) can provide technically natural inflatons, as has been comparatively well-explored in the simplest axion examples. Although inflationary success requires trans-Planckian decay constants, f > Mp, several mechanisms have been proposed to obtain this, relying on (mis-)alignments between potential and kinetic energies in multiple-field models. We extend these mechanisms to a broader class of inflationary models, including in particular the exponential potentials that arise for pGB potentials based on noncompact groups (and so which might apply to moduli in an extra-dimensional setting). The resulting potentials provide natural large-field inflationary models and can predict a larger primordial tensor signal than is true for simpler single-field versions of these models. In so doing we provide a unified treatment of several alignment mechanisms, showing how each emerges as a limit of the more general setup.

  12. Aligning component upgrades

    CERN Document Server

    Di Cosmo, Roberto; Michel, Claude; 10.4204/EPTCS.65.1

    2011-01-01

    Modern software systems, like GNU/Linux distributions or Eclipse-based development environment, are often deployed by selecting components out of large component repositories. Maintaining such software systems by performing component upgrades is a complex task, and the users need to have an expressive preferences language at their disposal to specify the kind of upgrades they are interested in. Recent research has shown that it is possible to develop solvers that handle preferences expressed as a combination of a few basic criteria used in the MISC competition, ranging from the number of new components to the freshness of the final configuration. In this work we introduce a set of new criteria that allow the users to specify their preferences for solutions with components aligned to the same upstream sources, provide an efficient encoding and report on the experimental results that prove that optimising these alignment criteria is a tractable problem in practice.

  13. Zirconia powders production by precipitation: state-of-art review; Producao de pos de zirconia por precipitacao - revisao do estado da arte

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Ana Paula Almeida de; Torem, Mauricio Leonardo [Pontificia Univ. Catolica do Rio de Janeiro, RJ (Brazil). Dept. de Ciencia dos Materiais e Metalurgia

    1994-12-31

    The important role played by zirconia in advanced ceramics can be attributed to its excellent wear and corrosion resistance and refractory character. The polymorphic nature of zirconia made the controlled addition of stabilizing oxides or the constraining effect of a dense ceramics matrix necessary to maintain high parameters had a significant influence on powder properties and on compacted powder behaviour in sintering. Particle shape and size, purity and crystalline structure were specially influenced by precipitation parameters. Therefore, this work presented a review of the state of the art in zirconia powder production and in the recent research on precipitation of that powder. (author) 15 refs., 5 figs., 2 tabs.

  14. Alignment of concerns

    DEFF Research Database (Denmark)

    Andersen, Tariq Osman; Bansler, Jørgen P.; Kensing, Finn

    E-health promises to enable and support active patient participation in chronic care. However, these fairly recent innovations are complicated matters and emphasize significant challenges, such as patients’ and clinicians’ different ways of conceptualizing disease and illness. Informed by insight...... from medical phenomenology and our own empirical work in telemonitoring and medical care of heart patients, we propose a design rationale for e-health systems conceptualized as the ‘alignment of concerns’....

  15. Orbit IMU alignment: Error analysis

    Science.gov (United States)

    Corson, R. W.

    1980-01-01

    A comprehensive accuracy analysis of orbit inertial measurement unit (IMU) alignments using the shuttle star trackers was completed and the results are presented. Monte Carlo techniques were used in a computer simulation of the IMU alignment hardware and software systems to: (1) determine the expected Space Transportation System 1 Flight (STS-1) manual mode IMU alignment accuracy; (2) investigate the accuracy of alignments in later shuttle flights when the automatic mode of star acquisition may be used; and (3) verify that an analytical model previously used for estimating the alignment error is a valid model. The analysis results do not differ significantly from expectations. The standard deviation in the IMU alignment error for STS-1 alignments was determined to the 68 arc seconds per axis. This corresponds to a 99.7% probability that the magnitude of the total alignment error is less than 258 arc seconds.

  16. Nuclear reactor alignment plate configuration

    Energy Technology Data Exchange (ETDEWEB)

    Altman, David A; Forsyth, David R; Smith, Richard E; Singleton, Norman R

    2014-01-28

    An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accomodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through with the dowel pins pass.

  17. Mechanical testing of thin-walled zirconia abutments

    Directory of Open Access Journals (Sweden)

    Luigi CANULLO

    2013-01-01

    Full Text Available Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bi-component aesthetic abutments has been suggested. Objective Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. Material and Methods Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25° angle inclination (n=10 each group. Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20°C±5°C. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope. Results Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean Fmax was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253 and dynamic testing (p=0.135. A significant difference in the bending moment required for fracture was detected between the groups (p=0.01. Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region. Conclusion Angled or straight thin-walled zirconia abutments presented similar Fmax under fatigue testing despite the different bending moments required for fracture. The main

  18. Seeking the perfect alignment

    CERN Multimedia

    2002-01-01

    The first full-scale tests of the ATLAS Muon Spectrometer are about to begin in Prévessin. The set-up includes several layers of Monitored Drift Tubes Chambers (MDTs) and will allow tests of the performance of the detectors and of their highly accurate alignment system.   Monitored Drift Chambers in Building 887 in Prévessin, where they are just about to be tested. Muon chambers are keeping the ATLAS Muon Spectrometer team quite busy this summer. Now that most people go on holiday, the beam and alignment tests for these chambers are just starting. These chambers will measure with high accuracy the momentum of high-energy muons, and this implies very demanding requirements for their alignment. The MDT chambers consist of drift tubes, which are gas-filled metal tubes, 3 cm in diameter, with wires running down their axes. With high voltage between the wire and the tube wall, the ionisation due to traversing muons is detected as electrical pulses. With careful timing of the pulses, the position of the muon t...

  19. PPB级锆基安培型NO气体传感器性能的研究%Characteristics Study of the Zirconia-Based Amperometric Gas Sensors Response to the PPB-Level Concentration of NO

    Institute of Scientific and Technical Information of China (English)

    朱卫学; 金涵; 朱丽娜; 张帆; 简家文

    2015-01-01

    采用丝网印刷技术制备了以In2O3为敏感电极的锆基安培型三电极NO传感器用以探测10-9级NO气体。用X射线衍射仪(XRD)和扫描电镜(SEM)对该传感器进行了理化分析;通过测量其在不同温度和不同NO浓度的气氛中的伏安特性曲线和时间响应曲线,研究了传感器的电流输出信号和NO浓度的关系以及时间响应特性。实验表明:在350℃~500℃测试温度范围内,极化电压为-60 mV,NO浓度变化为0~900×10-9时传感器响应电流的变化值Δcurrent和NO浓度之间存在较好的线性关系并且传感器在400℃时响应值最大。在被测气体总流量为100 cm3/min时,传感器信号90%的响应和恢复时间分别为18 s和12 s。传感器信号不受CO2浓度变化的影响,传感器的响应信号在测试时间里具有较好短期稳定性,但长期稳定性有待进一步提高。本文还采用阻抗谱分析方法对传感器的响应机理进行了初步的探索。%Amperometric NO sensor based on yttria-stabilized zirconia(YSZ)with In2O3sensing electrode was pre⁃pared by screen-printing technique to detect the ppblevel of NO. The physical characteristics of the sensor were studied by the X-ray diffraction(XRD)and scanning electron microscope(SEM).The sensitivity of the sensor was studied by measuring the current-voltagecurves and response/recovery time characteristics atdifferent NO concentra⁃tions and temperatures.The results show that,inthe range of 350℃~500℃and with the polarization voltage of-60 mV,there is a good linear relationship between the variation of the current change∆currentand NO concentration , whilethe volume fraction of NO changes from 0 to 900 × 10-9.The sensor response best when the temperature is at 400℃. When the total gas flow rate is 100 cm3/min,the response and recovery time of the 90%signal of the sensors are respectively 18 s and 12 s. Sensor signal is not affected by changes in CO2 concentration

  20. RECAT - Redundant Channel Alignment Technique

    Science.gov (United States)

    2016-06-07

    distribution unlimited 13. SUPPLEMENTARY NOTES NUWC2015 14. ABSTRACT A problem in the analog-to- digital , (A/D), conversion of broadband tape recorded...Alignment Technique, is used to align data taken on one pass with data from any other pass. The accuracy of this alignment is a function of the digital ...Redundant Channel Alignment Technique; analog-to- digital ; A/D; Broadband Bearing Time Processing 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

  1. Effect of Surface Treatment with Carbon Dioxide (CO2) Laser on Bond Strength between Cement Resin and Zirconia

    OpenAIRE

    Kasraei, Shahin; Atefat, Mohammad; Beheshti, Maryam; Safavi, Nassimeh; Mojtahedi, Maryam; Rezaei-Soufi, Loghman

    2014-01-01

    Introduction: Since it is not possible to form an adequate micromechanical bond between resin cement and zirconia ceramics using common surface treatment techniques, laser pretreatment has been suggested for zirconia ceramic surfaces. The aim of this study was to evaluate the effect of Carbon Dioxide (CO2) Laser treatment on shear bond strength (SBS) of resin cement to zirconia ceramic.

  2. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic: The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R.; Ozcan, M.; Bottino, M.A.; Valandro, L.F.

    2006-01-01

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR, VI

  3. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic : The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R; Ozcan, M; Bottino, MA; Valandro, LF

    2006-01-01

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR, VI

  4. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic : The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R; Ozcan, M; Bottino, MA; Valandro, LF

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR,

  5. Microtensile bond strength of a resin cement to glass infiltrated zirconia-reinforced ceramic: The effect of surface conditioning

    NARCIS (Netherlands)

    Amaral, R.; Ozcan, M.; Bottino, M.A.; Valandro, L.F.

    2006-01-01

    Objectives. This study evaluated the effect of three surface conditioning methods on the microtensile bond strength of resin cement to a glass-infiltrated zirconia-reinforced alumina-based core ceramic. Methods. Thirty blocks (5 x 5 x 4 mm) of In-Ceram Zirconia ceramics (In-Ceram Zirconia-INC-ZR,

  6. Method for alignment of microwires

    Energy Technology Data Exchange (ETDEWEB)

    Beardslee, Joseph A.; Lewis, Nathan S.; Sadtler, Bryce

    2017-01-24

    A method of aligning microwires includes modifying the microwires so they are more responsive to a magnetic field. The method also includes using a magnetic field so as to magnetically align the microwires. The method can further include capturing the microwires in a solid support structure that retains the longitudinal alignment of the microwires when the magnetic field is not applied to the microwires.

  7. Fatigue and fracture resistance of zirconia crowns prepared with different finish line designs

    NARCIS (Netherlands)

    Aboushelib, M.N.

    2012-01-01

    Purpose: The aim of this study was to evaluate the effect of finish line design on the fatigue, fracture resistance, and failure type of veneered zirconia restorations. Materials and Methods: A CAD/CAM system (Cercon) was used to prepare zirconia frameworks (0.5 mm thick) for a maxillary central

  8. Development of alternative oxygen production source using a zirconia solid electrolyte membrane

    Energy Technology Data Exchange (ETDEWEB)

    Suitor, J.W.; Clark, D.J.; Losey, R.W.

    1990-08-01

    The objective of this multiyear effort was the development, fabrication and testing of a zirconia oxygen production module capable of delivering approximately 100 liters/minute (LPM) of oxygen. The work discussed in this report consists of development and improvement of the zirconia cell along with manufacture of cell components, preliminary design of the final plant, additional economic analysis and industrial participation. (VC)

  9. Development of alternative oxygen production source using a zirconia solid electrolyte membrane. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Suitor, J.W.; Clark, D.J.; Losey, R.W.

    1990-08-01

    The objective of this multiyear effort was the development, fabrication and testing of a zirconia oxygen production module capable of delivering approximately 100 liters/minute (LPM) of oxygen. The work discussed in this report consists of development and improvement of the zirconia cell along with manufacture of cell components, preliminary design of the final plant, additional economic analysis and industrial participation. (VC)

  10. The Reinforcement Effect of Nano-Zirconia on the Transverse Strength of Repaired Acrylic Denture Base

    Directory of Open Access Journals (Sweden)

    Mohammed Gad

    2016-01-01

    Full Text Available Objective. The aim of this study was to evaluate the effect of incorporation of glass fiber, zirconia, and nano-zirconia on the transverse strength of repaired denture base. Materials and Methods. Eighty specimens of heat polymerized acrylic resin were prepared and randomly divided into eight groups (n=10: one intact group (control and seven repaired groups. One group was repaired with autopolymerized resin while the other six groups were repaired using autopolymerized resin reinforced with 2 wt% or 5 wt% glass fiber, zirconia, or nano-zirconia particles. A three-point bending test was used to measure the transverse strength. The results were analyzed using SPSS and repeated measure ANOVA and post hoc least significance (LSD test (P≤0.05. Results. Among repaired groups it was found that autopolymerized resin reinforced with 2 or 5 wt% nano-zirconia showed the highest transverse strength (P≤0.05. Repairs with autopolymerized acrylic resin reinforced with 5 wt% zirconia showed the lowest transverse strength value. There was no significant difference between the groups repaired with repair resin without reinforcement, 2 wt% zirconia, and glass fiber reinforced resin. Conclusion. Reinforcing of repair material with nano-zirconia may significantly improve the transverse strength of some fractured denture base polymers.

  11. The Reinforcement Effect of Nano-Zirconia on the Transverse Strength of Repaired Acrylic Denture Base.

    Science.gov (United States)

    Gad, Mohammed; ArRejaie, Aws S; Abdel-Halim, Mohamed Saber; Rahoma, Ahmed

    2016-01-01

    Objective. The aim of this study was to evaluate the effect of incorporation of glass fiber, zirconia, and nano-zirconia on the transverse strength of repaired denture base. Materials and Methods. Eighty specimens of heat polymerized acrylic resin were prepared and randomly divided into eight groups (n = 10): one intact group (control) and seven repaired groups. One group was repaired with autopolymerized resin while the other six groups were repaired using autopolymerized resin reinforced with 2 wt% or 5 wt% glass fiber, zirconia, or nano-zirconia particles. A three-point bending test was used to measure the transverse strength. The results were analyzed using SPSS and repeated measure ANOVA and post hoc least significance (LSD) test (P ≤ 0.05). Results. Among repaired groups it was found that autopolymerized resin reinforced with 2 or 5 wt% nano-zirconia showed the highest transverse strength (P ≤ 0.05). Repairs with autopolymerized acrylic resin reinforced with 5 wt% zirconia showed the lowest transverse strength value. There was no significant difference between the groups repaired with repair resin without reinforcement, 2 wt% zirconia, and glass fiber reinforced resin. Conclusion. Reinforcing of repair material with nano-zirconia may significantly improve the transverse strength of some fractured denture base polymers.

  12. Leveling and thixotropic characteristics of concentrated zirconia inks for screen-printing

    DEFF Research Database (Denmark)

    Phair, John; Lundberg, Mats; Kaiser, Andreas

    2009-01-01

    Screen-printing is a cost-effective method for the mass manufacture of zirconia-based solid oxide fuel cells (SOFCs) and oxygen separation membranes. The present work outlines an investigation into the leveling, thixotropic, and screen-printing characteristics of concentrated zirconia inks by a v...

  13. Effect of adhesive resin type for bonding to zirconia using two surface pretreatments

    NARCIS (Netherlands)

    Samimi, P.; Hasankhani, A.; Matinlinna, J.P.; Mirmohammadi, H.

    2015-01-01

    Purpose: This laboratory study evaluated the short-term adhesive properties of one 10-MDP-containing and two MDP-free resin composite cements, using two types of zirconia surface pretreatments. Materials and Methods: Eighteen sintered zirconia disks (Procera, Nobel Biocare) were randomly divided int

  14. Zirconia dental implants : a clinical, radiographic, and microbiologic evaluation up to 3 years

    NARCIS (Netherlands)

    Brüll, Felix; van Winkelhoff, Arie Jan; Cune, Marco S.

    2014-01-01

    PURPOSE: To retrospectively evaluate the clinical performance of zirconia endosseous implants. MATERIALS AND METHODS: Partially edentulous patients with adequate bone volume to fit yttria tetragonal zirconia polycrystal (Y-TZP) implants at least 3.5 mm wide and 8.0 mm long were included. Full-mouth

  15. Development of alternative oxygen production source using a zirconia solid electrolyte membrane

    Energy Technology Data Exchange (ETDEWEB)

    Suitor, J.W.; Clark, D.J.; Losey, R.W.

    1990-08-01

    The objective of this multiyear effort was the development, fabrication and testing of a zirconia oxygen production module capable of delivering approximately 100 liters/minute (LPM) of oxygen. The work discussed in this report consists of development and improvement of the zirconia cell along with manufacture of cell components, preliminary design of the final plant, additional economic analysis and industrial participation. (VC)

  16. Development of alternative oxygen production source using a zirconia solid electrolyte membrane. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Suitor, J.W.; Clark, D.J.; Losey, R.W.

    1990-08-01

    The objective of this multiyear effort was the development, fabrication and testing of a zirconia oxygen production module capable of delivering approximately 100 liters/minute (LPM) of oxygen. The work discussed in this report consists of development and improvement of the zirconia cell along with manufacture of cell components, preliminary design of the final plant, additional economic analysis and industrial participation. (VC)

  17. Soft tissue response to zirconia and titanium implant abutments : an in vivo within-subject comparison

    NARCIS (Netherlands)

    van Brakel, Ralph; Meijer, Gert J.; Verhoeven, Jan Willem; Jansen, John; de Putter, Cornelis; Cune, Marco S.

    2012-01-01

    Aim To compare the health of the soft tissues towards zirconia and titanium abutments in man, as observed using histological data. Material and Methods Twenty patients received two mandibular implants with either a zirconia or titanium abutment (split mouth study design, left-right randomization). A

  18. Soft tissue response to zirconia and titanium implant abutments: an in vivo within-subject comparison.

    NARCIS (Netherlands)

    Brakel, R. van; Meijer, G.J.; Verhoeven, J.W.; Jansen, J.A.; Putter, C. de; Cune, M.S.

    2012-01-01

    AIM: To compare the health of the soft tissues towards zirconia and titanium abutments in man, as observed using histological data. MATERIAL AND METHODS: Twenty patients received two mandibular implants with either a zirconia or titanium abutment (split mouth study design, left-right randomization).

  19. Microtensile bond strength and impact energy of fracture of CAD-veneered zirconia restorations

    NARCIS (Netherlands)

    M.N. Aboushelib; M. de Kler; J.M. van der Zel; A.J. Feilzer

    2009-01-01

    Purpose: With state-of-the-art CAD/CAM technology, the fabrication of large and complex zirconia frameworks is just a click away. On the other hand, veneering of the frameworks is still operator-dependent. The aim of this work was to evaluate CAD veneering of zirconia restorations in terms of zircon

  20. Simple Heat Treatment of Zirconia Ceramic Pre-Treated with Silane Primer to Improve Resin Bonding.

    Science.gov (United States)

    Ha, Jung-Yun; Son, Jun Sik; Kim, Kyo-Han; Kwon, Tae-Yub

    2015-01-01

    Establishing a strong resin bond to dental zirconia ceramic remains difficult. Previous studies have shown that the conventional application of silane does not work well with zirconia. This paper reports that a silane pre-treatment of dental zirconia ceramic combined with subsequent heat treatment has potential as an adhesive cementation protocol for improving zirconia-resin bonding. Among the various concentrations (0.1 to 16 vol%) of experimental γ-methacryloxypropyltrimethoxysilane (γ-MPTS) primers assessed, the 1% solution was found to be the most effective in terms of the shear bond strength of the resin cement to dental zirconia ceramic. A high shear bond strength (approx. 30 MPa) was obtained when zirconia specimens were pre-treated with this primer and then heat-treated in a furnace for 60 min at 150 degrees C. Heat treatment appeared to remove the hydrophilic constituents from the silane film formed on the zirconia ceramic surface and accelerate the condensation reactions between the silanol groups of the hydrolyzed silane molecules at the zirconia/resin interface, finally making a more desirable surface for bonding with resin. This estimation was supported by Fourier transform infrared spectroscopy of the silanes prepared in this study.